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Title: Man and Nature
or, Physical Geography as Modified by Human Action
Author: George P. Marsh
Release Date: November 9, 2011 [EBook #37957]
Language: English
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MAN AND NATURE;
OR,
PHYSICAL GEOGRAPHY
AS MODIFIED BY HUMAN ACTION.
BY
GEORGE P. MARSH.
"Not all the winds, and storms, and earthquakes, and seas, and seasons
of the world, have done so much to revolutionize the earth as MAN, the
power of an endless life, has done since the day he came forth upon it,
and received dominion over it."--H. BUSHNELL, _Sermon on the Power of an
Endless Life_.
NEW YORK:
CHARLES SCRIBNER & CO., No. 654 BROADWAY.
1867.
ENTERED, according to Act of Congress, in the year 1864, by
CHARLES SCRIBNER,
In the Clerk's Office of the District Court of the United States for the
Southern District of New York.
JOHN F. TROW & CO.
PRINTER, STEREOTYPER, AND ELECTROTYPER,
46, 48, & 50 Greene St., New York.
PREFACE.
The object of the present volume is: to indicate the character and,
approximately, the extent of the changes produced by human action in the
physical conditions of the globe we inhabit; to point out the dangers of
imprudence and the necessity of caution in all operations which, on a
large scale, interfere with the spontaneous arrangements of the organic
or the inorganic world; to suggest the possibility and the importance of
the restoration of disturbed harmonies and the material improvement of
waste and exhausted regions; and, incidentally, to illustrate the
doctrine, that man is, in both kind and degree, a power of a higher
order than any of the other forms of animated life, which, like him, are
nourished at the table of bounteous nature.
In the rudest stages of life, man depends upon spontaneous animal and
vegetable growth for food and clothing, and his consumption of such
products consequently diminishes the numerical abundance of the species
which serve his uses. At more advanced periods, he protects and
propagates certain esculent vegetables and certain fowls and
quadrupeds, and, at the same time, wars upon rival organisms which prey
upon these objects of his care or obstruct the increase of their
numbers. Hence the action of man upon the organic world tends to subvert
the original balance of its species, and while it reduces the numbers of
some of them, or even extirpates them altogether, it multiplies other
forms of animal and vegetable life.
The extension of agricultural and pastoral industry involves an
enlargement of the sphere of man's domain, by encroachment upon the
forests which once covered the greater part of the earth's surface
otherwise adapted to his occupation. The felling of the woods has been
attended with momentous consequences to the drainage of the soil, to the
external configuration of its surface, and probably, also, to local
climate; and the importance of human life as a transforming power is,
perhaps, more clearly demonstrable in the influence man has thus exerted
upon superficial geography than in any other result of his material
effort.
Lands won from the woods must be both drained and irrigated; river banks
and maritime coasts must be secured by means of artificial bulwarks
against inundation by inland and by ocean floods; and the needs of
commerce require the improvement of natural, and the construction of
artificial channels of navigation. Thus man is compelled to extend over
the unstable waters the empire he had already founded upon the solid
land.
The upheaval of the bed of seas and the movements of water and of wind
expose vast deposits of sand, which occupy space required for the
convenience of man, and often, by the drifting of their particles,
overwhelm the fields of human industry with invasions as disastrous as
the incursions of the ocean. On the other hand, on many coasts, sand
hills both protect the shores from erosion by the waves and currents,
and shelter valuable grounds from blasting sea winds. Man, therefore,
must sometimes resist, sometimes promote, the formation and growth of
dunes, and subject the barren and flying sands to the same obedience to
his will to which he has reduced other forms of terrestrial surface.
Besides these old and comparatively familiar methods of material
improvement, modern ambition aspires to yet grander achievements in the
conquest of physical nature, and projects are meditated which quite
eclipse the boldest enterprises hitherto undertaken for the modification
of geographical surface.
The natural character of the various fields where human industry has
effected revolutions so important, and where the multiplying population
and the impoverished resources of the globe demand new triumphs of mind
over matter, suggests a corresponding division of the general subject,
and I have conformed the distribution of the several topics to the
chronological succession in which man must be supposed to have extended
his sway over the different provinces of his material kingdom. I have,
then, in the Introductory chapter, stated, in a comprehensive way, the
general effects and the prospective consequences of human action upon
the earth's surface and the life which peoples it. This chapter is
followed by four others in which I have traced the history of man's
industry as exerted upon Animal and Vegetable Life, upon the Woods,
upon the Waters, and upon the Sands; and to these I have added a
concluding chapter upon Probable and Possible Geographical Revolutions
yet to be effected by the art of man.
I have only to add what, indeed, sufficiently appears upon every page of
the volume, that I address myself not to professed physicists, but to
the general intelligence of educated, observing, and thinking men; and
that my purpose is rather to make practical suggestions than to indulge
in theoretical speculations properly suited to a different class from
that to which those for whom I write belong.
GEORGE P. MARSH.
_December 1, 1863._
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TABLE OF CONTENTS.
CHAPTER I.
INTRODUCTORY.
Natural Advantages of the Territory of the Roman Empire--Physical
Decay of that Territory and of other parts of the Old World--
Causes of the Decay--New School of Geographers--Reaction of
Man upon Nature--Observation of Nature--Cosmical and Geological
Influences--Geographical Influence of Man--Uncertainty of our
Meteorological Knowledge--Mechanical Effects produced by Man on
the surface of the Earth--Importance and Possibility of Physical
Restoration--Stability of Nature--Restoration of Disturbed
Harmonies--Destructiveness of Man--Physical Improvement--Human
and Brute Action Compared--Forms and Formations most liable to
Physical Degradation--Physical Decay of New Countries--Corrupt
Influence of Private Corporations, _Note_, 1
CHAPTER II.
TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL
SPECIES.
Modern Geography embraces Organic Life--Transfer of Vegetable
Life--Foreign Plants grown in the United States--American
Plants grown in Europe--Modes of Introduction of Foreign
Plants--Vegetables, how affected by transfer to Foreign
Soils--Extirpation of Vegetables--Origin of Domestic Plants--
Organic Life as a Geological and Geographical Agency--Origin
and Transfer of Domestic Animals--Extirpation of Animals--
Numbers of Birds in the United States--Birds as Sowers and
Consumers of Seeds, and as Destroyers of Insects--Diminution
and Extirpation of Birds--Introduction of Birds--Utility of
Insects and Worms--Introduction of Insects--Destruction of
Insects--Reptiles--Destruction of Fish--Introduction and
Breeding of Fish--Extirpation of Aquatic Animals--Minute
Organisms, 57
CHAPTER III.
THE WOODS.
The Habitable Earth originally Wooded--The Forest does not
furnish Food for Man--First Removal of the Woods--Effects
of Fire on Forest Soil--Effects of the Destruction of the
Forest--Electrical Influence of Trees--Chemical Influence
of the Forest.
Influence of the Forest, considered as Inorganic Matter, on
Temperature: _a_, Absorbing and Emitting Surface; _b_, Trees
as Conductors of Heat; _c_, Trees in Summer and in Winter;
_d_, Dead Products of Tree; _e_, Trees as a Shelter to Grounds
to the leeward of them; _f_, Trees as a Protection against
Malaria--The Forest, as Inorganic Matter, tends to mitigate
extremes.
Trees as Organisms: Specific Temperature--Total Influence of
the Forest on Temperature.
Influence of Forests on the Humidity of the Air and the Earth:
_a_, as Inorganic Matter; _b_, as Organic--Wood Mosses and
Fungi--Flow of Sap--Absorption and Exhalation of Moisture by
Trees--Balance of Conflicting Influences--Influence of the
Forest on Temperature and Precipitation--Influence of the
Forest on the Humidity of the Soil--Its Influence on the Flow
of Springs--General Consequences of the Destruction of the
Woods--Literature and Condition of the Forest in different
Countries--The Influence of the Forest on Inundations--
Destructive Action of Torrents--The Po and its Deposits--
Mountain Slides--Protection against the Fall of Rocks and
Avalanches by Trees--Principal Causes of the Destruction of
the Forest--American Forest Trees--Special Causes of the
Destruction of European Woods--Royal Forests and Game Laws--
Small Forest Plants, Vitality of Seeds--Utility of the
Forest--The Forests of Europe--Forests of the United States
and Canada--The Economy of the Forest--European and American
Trees Compared--Sylviculture--Instability of American Life, 128
CHAPTER IV.
THE WATERS.
Land artificially won from the Waters: _a_, Exclusion of the Sea
by Diking; _b_, Draining of Lakes and Marshes; _c_, Geographical
Influence of such Operations--Lowering of Lakes--Mountain Lakes--
Climatic Effects of Draining Lakes and Marshes.
Geographical and Climatic Effects of Aqueducts, Reservoirs,
and Canals--Surface and Underdraining, and their Climatic and
Geographical Effects--Irrigation and its Climatic and Geographical
Effects.
Inundations and Torrents: _a_, River Embankments; _b_, Floods of
the Ardèche; _c_, Crushing Force of Torrents; _d_, Inundations of
1856 in France; _e_, Remedies against Inundations--Consequences
if the Nile had been confined by Lateral Dikes.
Improvements in the Val di Chiana--Improvements in the Tuscan
Maremme--Obstruction of River Mouths--Subterranean Waters--
Artesian Wells--Artificial Springs--Economizing Precipitation, 330
CHAPTER V.
THE SANDS.
Origin of Sand--Sand now carried down to the Sea--The Sands of
Egypt and the adjacent Desert--The Suez Canal--The Sands of
Egypt--Coast Dunes and Sand Plains--Sand Banks--Dunes on Coast of
America--Dunes of Western Europe--Formation of Dunes--Character of
Dune Sand--Interior Structure of Dunes--Form of Dunes--Geological
Importance of Dunes--Inland Dunes--Age, Character, and Permanence
of Dunes--Use of Dunes as Barrier against the Sea--Encroachments
of the Sea--The Lümfjord--Encroachments of the Sea--Drifting
of Dune Sands--Dunes of Gascony--Dunes of Denmark--Dunes of
Prussia--Artificial Formation of Dunes--Trees suitable for Dune
Plantations--Extent of Dunes in Europe--Dune Vineyards of Cape
Breton--Removal of Dunes--Inland Sand Plains--The Landes of
Gascony--The Belgian Campine--Sands and Steppes of Eastern
Europe--Advantages of Reclaiming Dunes--Government Works of
Improvement, 451
CHAPTER VI.
PROJECTED OR POSSIBLE GEOGRAPHICAL CHANGES BY MAN.
Cutting of Marine Isthmuses--The Suez Canal--Canal across Isthmus
of Darien--Canals to the Dead Sea--Maritime Canals in Greece--
Canal of Saros--Cape Cod Canal--Diversion of the Nile--Changes
in the Caspian--Improvements in North American Hydrography--
Diversion of the Rhine--Draining of the Zuiderzee--Waters of
the Karst--Subterranean Waters of Greece--Soil below Rock--
Covering Rocks with Earth--Wadies of Arabia Petræa--Incidental
Effects of Human Action--Resistance to great Natural Forces--
Effects of Mining--Espy's Theories--River Sediment--Nothing
small in Nature, 517
CHAPTER I.
INTRODUCTORY.
NATURAL ADVANTAGES OF THE TERRITORY OF THE ROMAN EMPIRE--PHYSICAL
DECAY OF THAT TERRITORY AND OF OTHER PARTS OF THE OLD WORLD--CAUSES
OF THE DECAY--NEW SCHOOL OF GEOGRAPHERS--REACTION OF MAN UPON NATURE--
OBSERVATION OF NATURE--COSMICAL AND GEOLOGICAL INFLUENCES--GEOGRAPHICAL
INFLUENCE OF MAN--UNCERTAINTY OF OUR METEOROLOGICAL KNOWLEDGE--
MECHANICAL EFFECTS PRODUCED BY MAN ON THE SURFACE OF THE EARTH--
IMPORTANCE AND POSSIBILITY OF PHYSICAL RESTORATION--STABILITY OF
NATURE--RESTORATION OF DISTURBED HARMONIES--DESTRUCTIVENESS OF MAN--
PHYSICAL IMPROVEMENT--HUMAN AND BRUTE ACTION COMPARED--FORMS AND
FORMATIONS MOST LIABLE TO PHYSICAL DEGRADATION--PHYSICAL DECAY OF NEW
COUNTRIES--CORRUPT INFLUENCE OF PRIVATE CORPORATIONS, _note_.
_Natural Advantages of the Territory of the Roman Empire._
The Roman Empire, at the period of its greatest expansion, comprised the
regions of the earth most distinguished by a happy combination of
physical advantages. The provinces bordering on the principal and the
secondary basins of the Mediterranean enjoyed a healthfulness and an
equability of climate, a fertility of soil, a variety of vegetable and
mineral products, and natural facilities for the transportation and
distribution of exchangeable commodities, which have not been possessed
in an equal degree by any territory of like extent in the Old World or
the New. The abundance of the land and of the waters adequately supplied
every material want, ministered liberally to every sensuous enjoyment.
Gold and silver, indeed, were not found in the profusion which has
proved so baneful to the industry of lands richer in veins of the
precious metals; but mines and river beds yielded them in the spare
measure most favorable to stability of value in the medium of exchange,
and, consequently, to the regularity of commercial transactions. The
ornaments of the barbaric pride of the East, the pearl, the ruby, the
sapphire, and the diamond--though not unknown to the luxury of a people
whose conquests and whose wealth commanded whatever the habitable world
could contribute to augment the material splendor of their social
life--were scarcely native to the territory of the empire; but the
comparative rarity of these gems in Europe, at somewhat earlier periods,
was, perhaps, the very circumstance that led the cunning artists of
classic antiquity to enrich softer stones with engravings, which invest
the common onyx and carnelian with a worth surpassing, in cultivated
eyes, the lustre of the most brilliant oriental jewels.
Of these manifold blessings the temperature of the air, the distribution
of the rains, the relative disposition of land and water, the plenty of
the sea, the composition of the soil, and the raw material of some of
the arts, were wholly gratuitous gifts. Yet the spontaneous nature of
Europe, of Western Asia, of Libya, neither fed nor clothed the civilized
inhabitants of those provinces. Every loaf was eaten in the sweat of the
brow. All must be earned by toil. But toil was nowhere else rewarded by
so generous wages; for nowhere would a given amount of intelligent labor
produce so abundant, and, at the same time, so varied returns of the
good things of material existence. The luxuriant harvests of cereals
that waved on every field from the shores of the Rhine to the banks of
the Nile, the vines that festooned the hillsides of Syria, of Italy, and
of Greece, the olives of Spain, the fruits of the gardens of the
Hesperides, the domestic quadrupeds and fowls known in ancient rural
husbandry--all these were original products of foreign climes,
naturalized in new homes, and gradually ennobled by the art of man,
while centuries of persevering labor were expelling the wild vegetation,
and fitting the earth for the production of more generous growths.
Only for the sense of landscape beauty did unaided nature make
provision. Indeed, the very commonness of this source of refined
enjoyment seems to have deprived it of half its value; and it was only
in the infancy of lands where all the earth was fair, that Greek and
Roman humanity had sympathy enough with the inanimate world to be alive
to the charms of rural and of mountain scenery. In later generations,
when the glories of the landscape had been heightened by plantation, and
decorative architecture, and other forms of picturesque improvement, the
poets of Greece and Rome were blinded by excess of light, and became, at
last, almost insensible to beauties that now, even in their degraded
state, enchant every eye, except, too often, those which a lifelong
familiarity has dulled to their attractions.
_Physical Decay of the Territory of the Roman Empire, and of other parts
of the Old World._
If we compare the present physical condition of the countries of which I
am speaking, with the descriptions that ancient historians and
geographers have given of their fertility and general capability of
ministering to human uses, we shall find that more than one half of
their whole extent--including the provinces most celebrated for the
profusion and variety of their spontaneous and their cultivated
products, and for the wealth and social advancement of their
inhabitants--is either deserted by civilized man and surrendered to
hopeless desolation, or at least greatly reduced in both productiveness
and population. Vast forests have disappeared from mountain spurs and
ridges; the vegetable earth accumulated beneath the trees by the decay
of leaves and fallen trunks, the soil of the alpine pastures which
skirted and indented the woods, and the mould of the upland fields, are
washed away; meadows, once fertilized by irrigation, are waste and
unproductive, because the cisterns and reservoirs that supplied the
ancient canals are broken, or the springs that fed them dried up; rivers
famous in history and song have shrunk to humble brooklets; the willows
that ornamented and protected the banks of the lesser watercourses are
gone, and the rivulets have ceased to exist as perennial currents,
because the little water that finds its way into their old channels is
evaporated by the droughts of summer, or absorbed by the parched earth,
before it reaches the lowlands; the beds of the brooks have widened into
broad expanses of pebbles and gravel, over which, though in the hot
season passed dryshod, in winter sealike torrents thunder; the entrances
of navigable streams are obstructed by sandbars, and harbors, once marts
of an extensive commerce, are shoaled by the deposits of the rivers at
whose mouths they lie; the elevation of the beds of estuaries, and the
consequently diminished velocity of the streams which flow into them,
have converted thousands of leagues of shallow sea and fertile lowland
into unproductive and miasmatic morasses.
Besides the direct testimony of history to the ancient fertility of the
regions to which I refer--Northern Africa, the greater Arabian
peninsula, Syria, Mesopotamia, Armenia and many other provinces of Asia
Minor, Greece, Sicily, and parts of even Italy and Spain--the multitude
and extent of yet remaining architectural ruins, and of decayed works of
internal improvement, show that at former epochs a dense population
inhabited those now lonely districts. Such a population could have been
sustained only by a productiveness of soil of which we at present
discover but slender traces; and the abundance derived from that
fertility serves to explain how large armies, like those of the ancient
Persians, and of the Crusaders and the Tartars in later ages, could,
without an organized commissariat, secure adequate supplies in long
marches through territories which, in our times, would scarcely afford
forage for a single regiment.
It appears, then, that the fairest and fruitfulest provinces of the
Roman Empire, precisely that portion of terrestrial surface, in short,
which, about the commencement of the Christian era, was endowed with the
greatest superiority of soil, climate, and position, which had been
carried to the highest pitch of physical improvement, and which thus
combined the natural and artificial conditions best fitting it for the
habitation and enjoyment of a dense and highly refined and cultivated
population, is now completely exhausted of its fertility, or so
diminished in productiveness, as, with the exception of a few favored
oases that have escaped the general ruin, to be no longer capable of
affording sustenance to civilized man. If to this realm of desolation we
add the now wasted and solitary soils of Persia and the remoter East,
that once fed their millions with milk and honey, we shall see that a
territory larger than all Europe, the abundance of which sustained in
bygone centuries a population scarcely inferior to that of the whole
Christian world at the present day, has been entirely withdrawn from
human use, or, at best, is thinly inhabited by tribes too few in
numbers, too poor in superfluous products, and too little advanced in
culture and the social arts, to contribute anything to the general moral
or material interests of the great commonwealth of man.
_Causes of this Decay._
The decay of these once flourishing countries is partly due, no doubt,
to that class of geological causes, whose action we can neither resist
nor guide, and partly also to the direct violence of hostile human
force; but it is, in a far greater proportion, either the result of
man's ignorant disregard of the laws of nature, or an incidental
consequence of war, and of civil and ecclesiastical tyranny and misrule.
Next to ignorance of these laws, the primitive source, the _causa
causarum_, of the acts and neglects which have blasted with sterility
and physical decrepitude the noblest half of the empire of the Cæsars,
is, first, the brutal and exhausting despotism which Rome herself
exercised over her conquered kingdoms, and even over her Italian
territory; then, the host of temporal and spiritual tyrannies which she
left as her dying curse to all her wide dominion, and which, in some
form of violence or of fraud, still brood over almost every soil subdued
by the Roman legions.[1] Man cannot struggle at once against crushing
oppression and the destructive forces of inorganic nature. When both are
combined against him, he succumbs after a shorter or a longer struggle,
and the fields he has won from the primeval wood relapse into their
original state of wild and luxuriant, but unprofitable forest growth,
or fall into that of a dry and barren wilderness.
Rome imposed on the products of agricultural labor in the rural
districts taxes which the sale of the entire harvest would scarcely
discharge; she drained them of their population by military
conscription; she impoverished the peasantry by forced and unpaid labor
on public works; she hampered industry and internal commerce by absurd
restrictions and unwise regulations. Hence, large tracts of land were
left uncultivated, or altogether deserted, and exposed to all the
destructive forces which act with such energy on the surface of the
earth when it is deprived of those protections by which nature
originally guarded it, and for which, in well-ordered husbandry, human
ingenuity has contrived more or less efficient substitutes.[2] Similar
abuses have tended to perpetuate and extend these evils in later ages,
and it is but recently that, even in the most populous parts of Europe,
public attention has been half awakened to the necessity of restoring
the disturbed harmonies of nature, whose well-balanced influences are so
propitious to all her organic offspring, of repaying to our great mother
the debt which the prodigality and the thriftlessness of former
generations have imposed upon their successors--thus fulfilling the
command of religion and of practical wisdom, to use this world as not
abusing it.
_New School of Geographers._
The labors of Humboldt, of Ritter, of Guyot and their followers, have
given to the science of geography a more philosophical, and, at the same
time, a more imaginative character than it had received from the hands
of their predecessors. Perhaps the most interesting field of
speculation, thrown open by the new school to the cultivators of this
attractive study, is the inquiry: how far external physical conditions,
and especially the configuration of the earth's surface, and the
distribution, outline, and relative position of land and water, have
influenced the social life and social progress of man.
_Reaction of Man on Nature._
But, as we have seen, man has reacted upon organized and inorganic
nature, and thereby modified, if not determined, the material structure
of his earthly home. The measure of that reaction manifestly constitutes
a very important element in the appreciation of the relations between
mind and matter, as well as in the discussion of many purely physical
problems. But though the subject has been incidentally touched upon by
many geographers, and treated with much fulness of detail in regard to
certain limited fields of human effort, and to certain specific effects
of human action, it has not, as a whole, so far as I know, been made
matter of special observation, or of historical research by any
scientific inquirer.[3] Indeed, until the influence of physical
geography upon human life was recognized as a distinct branch of
philosophical investigation, there was no motive for the pursuit of such
speculations; and it was desirable to inquire whether we have or can
become the architects of our own abiding place, only when it was known
how the mode of our physical, moral, and intellectual being is affected
by the character of the home which Providence has appointed, and we have
fashioned, for our material habitation.[4]
It is still too early to attempt scientific method in discussing this
problem, nor is our present store of the necessary facts by any means
complete enough to warrant me in promising any approach to fulness of
statement respecting them. Systematic observation in relation to this
subject has hardly yet begun,[5] and the scattered data which have
chanced to be recorded have never been collected. It has now no place in
the general scheme of physical science, and is matter of suggestion and
speculation only, not of established and positive conclusion. At
present, then, all that I can hope is to excite an interest in a topic
of much economical importance, by pointing out the directions and
illustrating the modes in which human action has been or may be most
injurious or most beneficial in its influence upon the physical
conditions of the earth we inhabit.
_Observation of Nature._
In these pages, as in all I have ever written or propose to write, it is
my aim to stimulate, not to satisfy, curiosity, and it is no part of my
object to save my readers the labor of observation or of thought. For
labor is life, and
Death lives where power lives unused.[6]
Self is the schoolmaster whose lessons are best worth his wages; and
since the subject I am considering has not yet become a branch of formal
instruction, those whom it may interest can, fortunately, have no
pedagogue but themselves. To the natural philosopher, the descriptive
poet, the painter, and the sculptor, as well as to the common observer,
the power most important to cultivate, and, at the same time, hardest to
acquire, is that of seeing what is before him. Sight is a faculty;
seeing, an art. The eye is a physical, but not a self-acting apparatus,
and in general it sees only what it seeks. Like a mirror, it reflects
objects presented to it; but it may be as insensible as a mirror, and it
does not necessarily perceive what it reflects.[7] It is disputed
whether the purely material sensibility of the eye is capable of
improvement and cultivation. It has been maintained by high authority,
that the natural acuteness of none of our sensuous faculties can be
heightened by use, and hence that the minutest details of the image
formed on the retina are as perfect in the most untrained, as in the
most thoroughly disciplined organ. This may well be doubted, and it is
agreed on all hands that the power of multifarious perception and rapid
discrimination may be immensely increased by well-directed practice.[8]
This exercise of the eye I desire to promote, and, next to moral and
religious doctrine, I know no more important practical lessons in this
earthly life of ours--which, to the wise man, is a school from the
cradle to the grave--than those relating to the employment of the sense
of vision in the study of nature.
The pursuit of physical geography, embracing actual observation of
terrestrial surface, affords to the eye the best general training that
is accessible to all. The majority of even cultivated men have not the
time and means of acquiring anything beyond a very superficial
acquaintance with any branch of physical knowledge. Natural science has
become so vastly extended, its recorded facts and its unanswered
questions so immensely multiplied, that every strictly scientific man
must be a specialist, and confine the researches of a whole life within
a comparatively narrow circle. The study I am recommending, in the view
I propose to take of it, is yet in that imperfectly developed state
which allows its votaries to occupy themselves with such broad and
general views as are attainable by every person of culture, and it does
not now require a knowledge of special details which only years of
application can master. It may be profitably pursued by all; and every
traveller, every lover of rural scenery, every agriculturist, who will
wisely use the gift of sight, may add valuable contributions to the
common stock of knowledge on a subject which, as I hope to convince my
readers, though long neglected, and now inartificially presented, is not
only a very important, but a very interesting field of inquiry.
_Cosmical and Geological Influences._
The revolutions of the seasons, with their alternations of temperature
and of length of day and night, the climates of different zones, and the
general condition and movements of the atmosphere and the seas, depend
upon causes for the most part cosmical, and, of course, wholly beyond
our control. The elevation, configuration, and composition of the great
masses of terrestrial surface, and the relative extent and distribution
of land and water, are determined by geological influences equally
remote from our jurisdiction. It would hence seem that the physical
adaptation of different portions of the earth to the use and enjoyment
of man is a matter so strictly belonging to mightier than human powers,
that we can only accept geographical nature as we find her, and be
content with such soils and such skies as she spontaneously offers.
_Geographical Influence of Man._
But it is certain that man has done much to mould the form of the
earth's surface, though we cannot always distinguish between the results
of his action and the effects of purely geological causes; that the
destruction of the forests, the drainage of lakes and marshes, and the
operations of rural husbandry and industrial art have tended to produce
great changes in the hygrometric, thermometric, electric, and chemical
condition of the atmosphere, though we are not yet able to measure the
force of the different elements of disturbance, or to say how far they
have been compensated by each other, or by still obscurer influences;
and, finally, that the myriad forms of animal and vegetable life, which
covered the earth when man first entered upon the theatre of a nature
whose harmonies he was destined to derange, have been, through his
action, greatly changed in numerical proportion, sometimes much modified
in form and product, and sometimes entirely extirpated.
The physical revolutions thus wrought by man have not all been
destructive to human interests. Soils to which no nutritious vegetable
was indigenous, countries which once brought forth but the fewest
products suited for the sustenance and comfort of man--while the
severity of their climates created and stimulated the greatest number
and the most imperious urgency of physical wants--surfaces the most
rugged and intractable, and least blessed with natural facilities of
communication, have been made in modern times to yield and distribute
all that supplies the material necessities, all that contributes to the
sensuous enjoyments and conveniences of civilized life. The Scythia, the
Thule, the Britain, the Germany, and the Gaul which the Roman writers
describe in such forbidding terms, have been brought almost to rival the
native luxuriance and easily won plenty of Southern Italy; and, while
the fountains of oil and wine that refreshed old Greece and Syria and
Northern Africa have almost ceased to flow, and the soils of those fair
lands are turned to thirsty and inhospitable deserts, the hyperborean
regions of Europe have conquered, or rather compensated, the rigors of
climate, and attained to a material wealth and variety of product that,
with all their natural advantages, the granaries of the ancient world
can hardly be said to have enjoyed.
These changes for evil and for good have not been caused by great
natural revolutions of the globe, nor are they by any means attributable
wholly to the moral and physical action or inaction of the peoples, or,
in all cases, even of the races that now inhabit these respective
regions. They are products of a complication of conflicting or
coincident forces, acting through a long series of generations; here,
improvidence, wastefulness, and wanton violence; there, foresight and
wisely guided persevering industry. So far as they are purely the
calculated and desired results of those simple and familiar operations
of agriculture and of social life which are as universal as
civilization--the removal of the forests which covered the soil required
for the cultivation of edible fruits, the drying of here and there a few
acres too moist for profitable husbandry, by draining off the surface
waters, the substitution of domesticated and nutritious for wild and
unprofitable vegetable growths, the construction of roads and canals and
artificial harbors--they belong to the sphere of rural, commercial, and
political economy more properly than to geography, and hence are but
incidentally embraced within the range of our present inquiries, which
concern physical, not financial balances. I propose to examine only the
greater, more permanent, and more comprehensive mutations which man has
produced, and is producing, in earth, sea, and sky, sometimes, indeed,
with conscious purpose, but for the most part, as unforeseen though
natural consequences of acts performed for narrower and more immediate
ends.
The exact measurement of the geographical changes hitherto thus effected
is, as I have hinted, impracticable, and we possess, in relation to
them, the means of only qualitative, not quantitative analysis. The fact
of such revolutions is established partly by historical evidence, partly
by analogical deduction from effects produced in our own time by
operations similar in character to those which must have taken place in
more or less remote ages of human action. Both sources of information
are alike defective in precision; the latter, for general reasons too
obvious to require specification; the former, because the facts to which
it bears testimony occurred before the habit or the means of rigorously
scientific observation upon any branch of physical research, and
especially upon climatic changes, existed.
_Uncertainty of our Meteorological Knowledge._
The invention of measures of heat, and of atmospheric moisture,
pressure, and precipitation, is extremely recent. Hence, ancient
physicists have left us no thermometric or barometric records, no tables
of the fall, evaporation, and flow of waters, and even no accurate maps
of coast lines and the course of rivers. Their notices of these
phenomena are almost wholly confined to excessive and exceptional
instances of high or of low temperatures, extraordinary falls of rain
and snow, and unusual floods or droughts. Our knowledge of the
meteorological condition of the earth, at any period more than two
centuries before our own time, is derived from these imperfect details,
from the vague statements of ancient historians and geographers in
regard to the volume of rivers and the relative extent of forest and
cultivated land, from the indications furnished by the history of the
agriculture and rural economy of past generations, and from other almost
purely casual sources of information.
Among these latter we must rank certain newly laid open fields of
investigation, from which facts bearing on the point now under
consideration have been gathered. I allude to the discovery of
artificial objects in geological formations older than any hitherto
recognized as exhibiting traces of the existence of man; to the ancient
lacustrine habitations of Switzerland, containing the implements of the
occupants, remains of their food, and other relics of human life; to the
curious revelations of the Kjökkenmöddinger, or heaps of kitchen refuse,
in Denmark, and of the peat mosses in the same and other northern
countries; to the dwellings and other evidences of the industry of man
in remote ages sometimes laid bare by the movement of sand dunes on the
coasts of France and of the North Sea; and to the facts disclosed on the
shores of the latter, by excavations in inhabited mounds which were,
perhaps, raised before the period of the Roman Empire. These remains are
memorials of races which have left no written records, because they
perished before the historical period of the countries they occupied
began. The plants and animals that furnished the relics found in the
deposits were certainly contemporaneous with man; for they are
associated with his works, and have evidently served his uses. In some
cases, the animals belonged to species well ascertained to be now
altogether extinct; in some others, both the animals and the vegetables,
though extant elsewhere, have ceased to inhabit the regions where their
remains are discovered. From the character of the artificial objects, as
compared with others belonging to known dates, or at least to known
periods of civilization, ingenious inferences have been drawn as to
their age; and from the vegetation, remains of which accompany them, as
to the climates of Central and Northern Europe at the time of their
production.
There are, however, sources of error which have not always been
sufficiently guarded against in making these estimates. When a boat,
composed of several pieces of wood fastened together by pins of the same
material, is dug out of a bog, it is inferred that the vessel, and the
skeletons and implements found with it, belong to an age when the use of
iron was not known to the builders. But this conclusion is not warranted
by the simple fact that metals were not employed in its construction;
for the Nubians at this day build boats large enough to carry half a
dozen persons across the Nile, out of small pieces of acacia wood pinned
together entirely with wooden bolts. Nor is the occurrence of flint
arrow heads and knives, in conjunction with other evidences of human
life, conclusive proof as to the antiquity of the latter. Lyell informs
us that some Oriental tribes still continue to use the same stone
implements as their ancestors, "after that mighty empires, where the use
of metals in the arts was well known, had flourished for three thousand
years in their neighborhood;"[9] and the North American Indians now
manufacture and use weapons of stone, and even of glass, chipping them
in the latter case out of the bottoms of thick bottles, with great
facility.[10]
We may also be misled by our ignorance of the commercial relations
existing between savage tribes. Extremely rude nations, in spite of
their jealousies and their perpetual wars, sometimes contrive to
exchange the products of provinces very widely separated from each
other. The mounds of Ohio contain pearls, thought to be marine, which
must have come from the Gulf of Mexico, or perhaps even from California,
and the knives and pipes found in the same graves are often formed of
far-fetched material, that was naturally paid for by some home product
exported to the locality whence the material was derived. The art of
preserving fish, flesh, and fowl by drying and smoking is widely
diffused, and of great antiquity. The Indians of Long Island Sound are
said to have carried on a trade in dried shell fish with tribes residing
very far inland. From the earliest ages, the inhabitants of the Faroe
and Orkney Islands, and of the opposite mainland coasts, have smoked
wild fowl and other flesh. Hence it is possible that the animal and the
vegetable food, the remains of which are found in the ancient deposits I
am speaking of, may sometimes have been brought from climates remote
from that where it was consumed.
The most important, as well as the most trustworthy conclusions with
respect to the climate of ancient Europe and Asia, are those drawn from
the accounts given by the classical writers of the growth of cultivated
plants; but these are by no means free from uncertainty, because we can
seldom be sure of an identity of species, almost never of an identity of
race or variety, between vegetables known to the agriculturists of
Greece and Rome and those of modern times which are thought most nearly
to resemble them. Besides this, there is always room for doubt whether
the habits of plants long grown in different countries may not have been
so changed by domestication that the conditions of temperature and
humidity which they required twenty centuries ago were different from
those at present demanded for their advantageous cultivation.[11]
Even if we suppose an identity of species, of race, and of habit to be
established between a given ancient and modern plant, the negative fact
that the latter will not grow now where it flourished two thousand years
ago does not in all cases prove a change of climate. The same result
might follow from the exhaustion of the soil,[12] or from a change in
the quantity of moisture it habitually contains. After a district of
country has been completely or even partially cleared of its forest
growth, and brought under cultivation, the drying of the soil, under
favorable circumstances, goes on for generations, perhaps for ages.[13]
In other cases, from injudicious husbandry, or the diversion or choking
up of natural watercourses, it may become more highly charged with
humidity. An increase or diminution of the moisture of a soil almost
necessarily supposes an elevation or a depression of its winter or its
summer heat, and of its extreme, if not of its mean annual temperature,
though such elevation or depression may be so slight as not sensibly to
raise or lower the mercury in a thermometer exposed to the open air. Any
of these causes, more or less humidity, or more or less warmth of soil,
would affect the growth both of wild and of cultivated vegetation, and
consequently, without any appreciable change in atmospheric temperature,
precipitation, or evaporation, plants of a particular species might
cease to be advantageously cultivated where they had once been easily
reared.[14] We are very imperfectly acquainted with the present mean
and extreme temperature, or the precipitation and the evaporation of any
extensive region, even in countries most densely peopled and best
supplied with instruments and observers. The progress of science is
constantly detecting errors of method in older observations, and many
laboriously constructed tables of meteorological phenomena are now
thrown aside as fallacious, and therefore worse than useless, because
some condition necessary to secure accuracy of result was neglected, in
obtaining the data on which they were founded.
To take a familiar instance: it is but recently that attention has been
drawn to the great influence of slight changes of station upon the
results of observations of temperature and precipitation. A thermometer
removed but a few hundred yards from its first position differs not
unfrequently five, sometimes even ten degrees in its readings; and when
we are told that the annual fall of rain on the roof of the observatory
at Paris is two inches less than on the ground by the side of it, we may
see that the level of the rain-gauge is a point of much consequence in
making estimates from its measurements. The data from which results have
been deduced with respect to the hygrometrical and thermometrical
conditions, the climate in short, of different countries, have very
often been derived from observations at single points in cities or
districts separated by considerable distances. The tendency of errors
and accidents to balance each other authorizes us, indeed, to entertain
greater confidence than we could otherwise feel in the conclusions drawn
from such tables; but it is in the highest degree probable that they
would be much modified by more numerous series of observations, at
different stations within narrow limits.[15]
There is one branch of research which is of the utmost importance in
reference to these questions, but which, from the great difficulty of
direct observation upon it, has been less successfully studied than
almost any other problem of physical science. I refer to the proportions
between precipitation, superficial drainage, absorption, and
evaporation. Precise actual measurement of these quantities upon even a
single acre of ground is impossible; and in all cabinet experiments on
the subject, the conditions of the surface observed are so different
from those which occur in nature, that we cannot safely reason from one
case to the other. In nature, the inclination of the ground, the degree
of freedom or obstruction of the surface, the composition and density of
the soil, upon which its permeability by water and its power of
absorbing and retaining or transmitting moisture depend, its
temperature, the dryness or saturation of the subsoil, vary at
comparatively short distances; and though the precipitation upon and the
superficial flow from very small geographical basins may be estimated
with an approach to precision, yet even here we have no present means
of knowing how much of the water absorbed by the earth is restored to
the atmosphere by evaporation, and how much carried off by infiltration
or other modes of underground discharge. When, therefore, we attempt to
use the phenomena observed on a few square or cubic yards of earth, as a
basis of reasoning upon the meteorology of a province, it is evident
that our data must be insufficient to warrant positive general
conclusions. In discussing the climatology of whole countries, or even
of comparatively small local divisions, we may safely say that none can
tell what percentage of the water they receive from the atmosphere is
evaporated; what absorbed by the ground and conveyed off by subterranean
conduits; what carried down to the sea by superficial channels; what
drawn from the earth or the air by a given extent of forest, of short
pasture vegetation, or of tall meadow-grass; what given out again by
surfaces so covered, or by bare ground of various textures and
composition, under different conditions of atmospheric temperature,
pressure, and humidity; or what is the amount of evaporation from water,
ice, or snow, under the varying exposures to which, in actual nature,
they are constantly subjected. If, then, we are so ignorant of all these
climatic phenomena in the best-known regions inhabited by man, it is
evident that we can rely little upon theoretical deductions applied to
the former more natural state of the same regions--less still to such as
are adopted with respect to distant, strange, and primitive countries.
_Mechanical Effects produced by Man on the Surface of the Earth more
easily ascertainable._
In investigating the mechanical effects of human action on superficial
geography, we are treading on safer ground, and dealing with much less
subtile phenomena, less intractable elements. Great physical changes
can, in some cases, be positively shown, in some almost certainly
inferred, to have been produced by the operations of rural industry, and
by the labors of man in other spheres of material effort; and hence, in
this most important part of our subject, we can arrive at many positive
generalizations, and obtain practical results of no small economical
value.
_Importance and Possibility of Physical Restoration._
Many circumstances conspire to invest with great present interest the
questions: how far man can permanently modify and ameliorate those
physical conditions of terrestrial surface and climate on which his
material welfare depends; how far he can compensate, arrest, or retard
the deterioration which many of his agricultural and industrial
processes tend to produce; and how far he can restore fertility and
salubrity to soils which his follies or his crimes have made barren or
pestilential. Among these circumstances, the most prominent, perhaps, is
the necessity of providing new homes for a European population which is
increasing more rapidly than its means of subsistence, new physical
comforts for classes of the people that have now become too much
enlightened and have imbibed too much culture to submit to a longer
deprivation of a share in the material enjoyments which the privileged
ranks have hitherto monopolized.
To supply new hives for the emigrant swarms, there are, first, the vast
unoccupied prairies and forests of America, of Australia, and of many
other great oceanic islands, the sparsely inhabited and still
unexhausted soils of Southern and even Central Africa, and, finally, the
impoverished and half-depopulated shores of the Mediterranean, and the
interior of Asia Minor and the farther East. To furnish to those who
shall remain after emigration shall have conveniently reduced the too
dense population of many European states, those means of sensuous and of
intellectual well-being which are styled "artificial wants" when
demanded by the humble and the poor, but are admitted to be
"necessaries" when claimed by the noble and the rich, the soil must be
stimulated to its highest powers of production, and man's utmost
ingenuity and energy must be tasked to renovate a nature drained, by
his improvidence, of fountains which a wise economy would have made
plenteous and perennial sources of beauty, health, and wealth.
In those yet virgin lands which the progress of modern discovery in both
hemispheres has brought and is still bringing to the knowledge and
control of civilized man, not much improvement of great physical
conditions is to be looked for. The proportion of forest is indeed to be
considerably reduced, superfluous waters to be drawn off, and routes of
internal communication to be constructed; but the primitive geographical
and climatic features of these countries ought to be, as far as
possible, retained.
_Stability of Nature._
Nature, left undisturbed, so fashions her territory as to give it almost
unchanging permanence of form, outline, and proportion, except when
shattered by geologic convulsions; and in these comparatively rare cases
of derangement, she sets herself at once to repair the superficial
damage, and to restore, as nearly as practicable, the former aspect of
her dominion. In new countries, the natural inclination of the ground,
the self-formed slopes and levels, are generally such as best secure the
stability of the soil. They have been graded and lowered or elevated by
frost and chemical forces and gravitation and the flow of water and
vegetable deposit and the action of the winds, until, by a general
compensation of conflicting forces, a condition of equilibrium has been
reached which, without the action of man, would remain, with little
fluctuation, for countless ages.
We need not go far back to reach a period when, in all that portion of
the North American continent which has been occupied by British
colonization, the geographical elements very nearly balanced and
compensated each other. At the commencement of the seventeenth century,
the soil, with insignificant exceptions, was covered with forests;[16]
and whenever the Indian, in consequence of war or the exhaustion of the
beasts of the chase, abandoned the narrow fields he had planted and the
woods he had burned over, they speedily returned, by a succession of
herbaceous, arborescent, and arboreal growths, to their original state.
Even a single generation sufficed to restore them almost to their
primitive luxuriance of forest vegetation.[17] The unbroken forests had
attained to their maximum density and strength of growth, and, as the
older trees decayed and fell, they were succeeded by new shoots or
seedlings, so that from century to century no perceptible change seems
to have occurred in the wood, except the slow, spontaneous succession of
crops. This succession involved no interruption of growth, and but
little break in the "boundless contiguity of shade;" for, in the
husbandry of nature, there are no fallows. Trees fall singly, not by
square roods, and the tall pine is hardly prostrate, before the light
and heat, admitted to the ground by the removal of the dense crown of
foliage which had shut them out, stimulate the germination of the seeds
of broad-leaved trees that had lain, waiting this kindly influence,
perhaps for centuries. Two natural causes, destructive in character,
were, indeed, in operation in the primitive American forests, though, in
the Northern colonies, at least, there were sufficient compensations;
for we do not discover that any considerable permanent change was
produced by them. I refer to the action of beavers and of fallen trees
in producing bogs,[18] and of smaller animals, insects, and birds, in
destroying the woods. Bogs are less numerous and extensive in the
Northern States of the American union, because the natural inclination
of the surface favors drainage; but they are more frequent, and cover
more ground, in the Southern States, for the opposite reason.[19] They
generally originate in the checking of watercourses by the falling of
timber, or of earth and rocks, across their channels. If the impediment
thus created is sufficient to retain a permanent accumulation of water
behind it, the trees whose roots are overflowed soon perish, and then by
their fall increase the obstruction, and, of course, occasion a still
wider spread of the stagnating stream. This process goes on until the
water finds a new outlet, at a higher level, not liable to similar
interruption. The fallen trees not completely covered by water are soon
overgrown with mosses; aquatic and semi-aquatic plants propagate
themselves, and spread until they more or less completely fill up the
space occupied by the water, and the surface is gradually converted from
a pond to a quaking morass.[20] The morass is slowly solidified by
vegetable production and deposit, then very often restored to the
forest condition by the growth of black ashes, cedars, or, in southern
latitudes, cypresses, and other trees suited to such a soil, and thus
the interrupted harmony of nature is at last reëstablished.
I am disposed to think that more bogs in the Northern States owe their
origin to beavers than to accidental obstructions of rivulets by
wind-fallen or naturally decayed trees; for there are few swamps in
those States, at the outlets of which we may not, by careful search,
find the remains of a beaver dam. The beaver sometimes inhabits natural
lakelets, but he prefers to owe his pond to his own ingenuity and toil.
The reservoir once constructed, its inhabitants rapidly multiply, and as
its harvests of pond lilies, and other aquatic plants on which this
quadruped feeds in winter, become too small for the growing population,
the beaver metropolis sends out expeditions of discovery and
colonization. The pond gradually fills up, by the operation of the same
causes as when it owes its existence to an accidental obstruction, and
when, at last, the original settlement is converted into a bog by the
usual processes of vegetable life, the remaining inhabitants abandon it
and build on some virgin brooklet a new city of the waters.
In countries somewhat further advanced in civilization than those
occupied by the North American Indians, as in mediæval Ireland, the
formation of bogs may be commenced by the neglect of man to remove, from
the natural channels of superficial drainage, the tops and branches of
trees felled for the various purposes to which wood is applicable in
his rude industry; and, when the flow of the water is thus checked,
nature goes on with the processes I have already described. In such
half-civilized regions, too, windfalls are more frequent than in those
where the forest is unbroken, because, when openings have been made in
it, for agricultural or other purposes, the entrance thus afforded to
the wind occasions the sudden overthrow of hundreds of trees which might
otherwise have stood for generations, and thus have fallen to the
ground, only one by one, as natural decay brought them down.[21] Besides
this, the flocks bred by man in the pastoral state, keep down the
incipient growth of trees on the half-dried bogs, and prevent them from
recovering their primitive condition.
Young trees in the native forest are sometimes girdled and killed by the
smaller rodent quadrupeds, and their growth is checked by birds which
feed on the terminal bud; but these animals, as we shall see, are
generally found on the skirts of the wood only, not in its deeper
recesses, and hence the mischief they do is not extensive. The insects
which damage primitive forests by feeding upon products of trees
essential to their growth, are not numerous, nor is their appearance, in
destructive numbers, frequent; and those which perforate the stems and
branches, to deposit and hatch their eggs, more commonly select dead
trees for that purpose, though, unhappily, there are important
exceptions to this latter remark.[22] I do not know that we have any
evidence of the destruction or serious injury of American forests by
insects, before or even soon after the period of colonization; but since
the white man has laid bare a vast proportion of the earth's surface,
and thereby produced changes favorable, perhaps, to the multiplication
of these pests, they have greatly increased in numbers, and, apparently,
in voracity also. Not many years ago, the pines on thousands of acres of
land in North Carolina, were destroyed by insects not known to have ever
done serious injury to that tree before. In such cases as this and
others of the like sort, there is good reason to believe that man is the
indirect cause of an evil for which he pays so heavy a penalty. Insects
increase whenever the birds which feed upon them disappear. Hence, in
the wanton destruction of the robin and other insectivorous birds, the
_bipes implumis_, the featherless biped, man, is not only exchanging the
vocal orchestra which greets the rising sun for the drowsy beetle's
evening drone, and depriving his groves and his fields of their fairest
ornament, but he is waging a treacherous warfare on his natural
allies.[23]
In fine, in countries untrodden by man, the proportions and relative
positions of land and water, the atmospheric precipitation and
evaporation, the thermometric mean, and the distribution of vegetable
and animal life, are subject to change only from geological influences
so slow in their operation that the geographical conditions may be
regarded as constant and immutable. These arrangements of nature it is,
in most cases, highly desirable substantially to maintain, when such
regions become the seat of organized commonwealths. It is, therefore, a
matter of the first importance, that, in commencing the process of
fitting them for permanent civilized occupation, the transforming
operations should be so conducted as not unnecessarily to derange and
destroy what, in too many cases, it is beyond the power of man to
rectify or restore.
_Restoration of Disturbed Harmonies._
In reclaiming and reoccupying lands laid waste by human improvidence or
malice, and abandoned by man, or occupied only by a nomade or thinly
scattered population, the task of the pioneer settler is of a very
different character. He is to become a co-worker with nature in the
reconstruction of the damaged fabric which the negligence or the
wantonness of former lodgers has rendered untenantable. He must aid her
in reclothing the mountain slopes with forests and vegetable mould,
thereby restoring the fountains which she provided to water them; in
checking the devastating fury of torrents, and bringing back the surface
drainage to its primitive narrow channels; and in drying deadly morasses
by opening the natural sluices which have been choked up, and cutting
new canals for drawing off their stagnant waters. He must thus, on the
one hand, create new reservoirs, and, on the other, remove mischievous
accumulations of moisture, thereby equalizing and regulating the sources
of atmospheric humidity and of flowing water, both which are so
essential to all vegetable growth, and, of course, to human and lower
animal life.
_Destructiveness of Man._
Man has too long forgotten that the earth was given to him for usufruct
alone, not for consumption, still less for profligate waste. Nature has
provided against the absolute destruction of any of her elementary
matter, the raw material of her works; the thunderbolt and the tornado,
the most convulsive throes of even the volcano and the earthquake, being
only phenomena of decomposition and recomposition. But she has left it
within the power of man irreparably to derange the combinations of
inorganic matter and of organic life, which through the night of æons
she had been proportioning and balancing, to prepare the earth for his
habitation, when, in the fulness of time, his Creator should call him
forth to enter into its possession.
Apart from the hostile influence of man, the organic and the inorganic
world are, as I have remarked, bound together by such mutual relations
and adaptations as secure, if not the absolute permanence and
equilibrium of both, a long continuance of the established conditions of
each at any given time and place, or at least, a very slow and gradual
succession of changes in those conditions. But man is everywhere a
disturbing agent. Wherever he plants his foot, the harmonies of nature
are turned to discords. The proportions and accommodations which insured
the stability of existing arrangements are overthrown. Indigenous
vegetable and animal species are extirpated, and supplanted by others of
foreign origin, spontaneous production is forbidden or restricted, and
the face of the earth is either laid bare or covered with a new and
reluctant growth of vegetable forms, and with alien tribes of animal
life. These intentional changes and substitutions constitute, indeed,
great revolutions; but vast as is their magnitude and importance, they
are, as we shall see, insignificant in comparison with the contingent
and unsought results which have flowed from them.
The fact that, of all organic beings, man alone is to be regarded as
essentially a destructive power, and that he wields energies to resist
which, nature--that Nature whom all material life and all inorganic
substance obey--is wholly impotent, tends to prove that, though living
in physical nature, he is not of her, that he is of more exalted
parentage, and belongs to a higher order of existences than those born
of her womb and submissive to her dictates.
There are, indeed, brute destroyers, beasts and birds and insects of
prey--all animal life feeds upon, and, of course, destroys other
life,--but this destruction is balanced by compensations. It is, in
fact, the very means by which the existence of one tribe of animals or
of vegetables is secured against being smothered by the encroachments of
another; and the reproductive powers of species, which serve as the food
of others, are always proportioned to the demand they are destined to
supply. Man pursues his victims with reckless destructiveness; and,
while the sacrifice of life by the lower animals is limited by the
cravings of appetite, he unsparingly persecutes, even to extirpation,
thousands of organic forms which he cannot consume.[24]
The earth was not, in its natural condition, completely adapted to the
use of man, but only to the sustenance of wild animals and wild
vegetation. These live, multiply their kind in just proportion, and
attain their perfect measure of strength and beauty, without producing
or requiring any change in the natural arrangements of surface, or in
each other's spontaneous tendencies, except such mutual repression of
excessive increase as may prevent the extirpation of one species by the
encroachments of another. In short, without man, lower animal and
spontaneous vegetable life would have been constant in type,
distribution, and proportion, and the physical geography of the earth
would have remained undisturbed for indefinite periods, and been subject
to revolution only from possible, unknown cosmical causes, or from
geological action.
But man, the domestic animals that serve him, the field and garden
plants the products of which supply him with food and clothing, cannot
subsist and rise to the full development of their higher properties,
unless brute and unconscious nature be effectually combated, and, in a
great degree, vanquished by human art. Hence, a certain measure of
transformation of terrestrial surface, of suppression of natural, and
stimulation of artificially modified productivity becomes necessary.
This measure man has unfortunately exceeded. He has felled the forests
whose network of fibrous roots bound the mould to the rocky skeleton of
the earth; but had he allowed here and there a belt of woodland to
reproduce itself by spontaneous propagation, most of the mischiefs which
his reckless destruction of the natural protection of the soil has
occasioned would have been averted. He has broken up the mountain
reservoirs, the percolation of whose waters through unseen channels
supplied the fountains that refreshed his cattle and fertilized his
fields; but he has neglected to maintain the cisterns and the canals of
irrigation which a wise antiquity had constructed to neutralize the
consequences of its own imprudence. While he has torn the thin glebe
which confined the light earth of extensive plains, and has destroyed
the fringe of semi-aquatic plants which skirted the coast and checked
the drifting of the sea sand, he has failed to prevent the spreading of
the dunes by clothing them with artificially propagated vegetation. He
has ruthlessly warred on all the tribes of animated nature whose spoil
he could convert to his own uses, and he has not protected the birds
which prey on the insects most destructive to his own harvests.
Purely untutored humanity, it is true, interferes comparatively little
with the arrangements of nature,[25] and the destructive agency of man
becomes more and more energetic and unsparing as he advances in
civilization, until the impoverishment, with which his exhaustion of the
natural resources of the soil is threatening him, at last awakens him to
the necessity of preserving what is left, if not of restoring what has
been wantonly wasted. The wandering savage grows no cultivated
vegetable, fells no forest, and extirpates no useful plant, no noxious
weed. If his skill in the chase enables him to entrap numbers of the
animals on which he feeds, he compensates this loss by destroying also
the lion, the tiger, the wolf, the otter, the seal, and the eagle, thus
indirectly protecting the feebler quadrupeds and fish and fowls, which
would otherwise become the booty of beasts and birds of prey. But with
stationary life, or rather with the pastoral state, man at once
commences an almost indiscriminate warfare upon all the forms of animal
and vegetable existence around him, and as he advances in civilization,
he gradually eradicates or transforms every spontaneous product of the
soil he occupies.[26]
_Human and Brute Action Compared._
It has been maintained by authorities as high as any known to modern
science, that the action of man upon nature, though greater in _degree_,
does not differ in _kind_, from that of wild animals. It appears to me
to differ in essential character, because, though it is often followed
by unforeseen and undesired results, yet it is nevertheless guided by a
self-conscious and intelligent will aiming as often at secondary and
remote as at immediate objects. The wild animal, on the other hand, acts
instinctively, and, so far as we are able to perceive, always with a
view to single and direct purposes. The backwoodsman and the beaver
alike fell trees; the man that he may convert the forest into an olive
grove that will mature its fruit only for a succeeding generation, the
beaver that he may feed upon their bark or use them in the construction
of his habitation. Human differs from brute action, too, in its
influence upon the material world, because it is not controlled by
natural compensations and balances. Natural arrangements, once disturbed
by man, are not restored until he retires from the field, and leaves
free scope to spontaneous recuperative energies; the wounds he inflicts
upon the material creation are not healed until he withdraws the arm
that gave the blow. On the other hand, I am not aware of any evidence
that wild animals have ever destroyed the smallest forest, extirpated
any organic species or modified its natural character, occasioned any
permanent change of terrestrial surface, or produced any disturbance of
physical conditions which nature has not, of herself, repaired without
the expulsion of the animal that had caused it.[27]
The form of geographical surface, and very probably the climate of a
given country, depend much on the character of the vegetable life
belonging to it. Man has, by domestication, greatly changed the habits
and properties of the plants he rears; he has, by voluntary selection,
immensely modified the forms and qualities of the animated creatures
that serve him; and he has, at the same time, completely rooted out many
forms of animal if not of vegetable being.[28] What is there, in the
influence of brute life, that corresponds to this? We have no reason to
believe that in that portion of the American continent which, though
peopled by many tribes of quadruped and fowl, remained uninhabited by
man, or only thinly occupied by purely savage tribes, any sensible
geographical change had occurred within twenty centuries before the
epoch of discovery and colonization, while, during the same period, man
had changed millions of square miles, in the fairest and most fertile
regions of the Old World, into the barrenest deserts.
The ravages committed by man subvert the relations and destroy the
balance which nature had established between her organized and her
inorganic creations; and she avenges herself upon the intruder, by
letting loose upon her defaced provinces destructive energies hitherto
kept in check by organic forces destined to be his best auxiliaries, but
which he has unwisely dispersed and driven from the field of action.
When the forest is gone, the great reservoir of moisture stored up in
its vegetable mould is evaporated, and returns only in deluges of rain
to wash away the parched dust into which that mould has been converted.
The well-wooded and humid hills are turned to ridges of dry rock, which
encumbers the low grounds and chokes the watercourses with its debris,
and--except in countries favored with an equable distribution of rain
through the seasons, and a moderate and regular inclination of
surface--the whole earth, unless rescued by human art from the physical
degradation to which it tends, becomes an assemblage of bald mountains,
of barren, turfless hills, and of swampy and malarious plains. There are
parts of Asia Minor, of Northern Africa, of Greece, and even of Alpine
Europe, where the operation of causes set in action by man has brought
the face of the earth to a desolation almost as complete as that of the
moon; and though, within that brief space of time which we call "the
historical period," they are known to have been covered with luxuriant
woods, verdant pastures, and fertile meadows, they are now too far
deteriorated to be reclaimable by man, nor can they become again fitted
for human use, except through great geological changes, or other
mysterious influences or agencies of which we have no present knowledge,
and over which we have no prospective control. The earth is fast
becoming an unfit home for its noblest inhabitant, and another era of
equal human crime and human improvidence, and of like duration with that
through which traces of that crime and that improvidence extend, would
reduce it to such a condition of impoverished productiveness, of
shattered surface, of climatic excess, as to threaten the depravation,
barbarism, and perhaps even extinction of the species.[29]
_Physical Improvement._
True, there is a partial reverse to this picture. On narrow theatres,
new forests have been planted; inundations of flowing streams restrained
by heavy walls of masonry and other constructions; torrents compelled to
aid, by depositing the slime with which they are charged, in filling up
lowlands, and raising the level of morasses which their own overflows
had created; ground submerged by the encroachments of the ocean, or
exposed to be covered by its tides, has been rescued from its dominion
by diking;[30] swamps and even lakes have been drained, and their beds
brought within the domain of agricultural industry; drifting coast dunes
have been checked and made productive by plantation; seas and inland
waters have been repeopled with fish, and even the sands of the Sahara
have been fertilized by artesian fountains. These achievements are more
glorious than the proudest triumphs of war, but, thus far, they give but
faint hope that we shall yet make full atonement for our spendthrift
waste of the bounties of nature.
It is, on the one hand, rash and unphilosophical to attempt to set
limits to the ultimate power of man over inorganic nature, and it is
unprofitable, on the other, to speculate on what may be accomplished by
the discovery of now unknown and unimagined natural forces, or even by
the invention of new arts and new processes. But since we have seen
aerostation, the motive power of elastic vapors, the wonders of modern
telegraphy, the destructive explosiveness of gunpowder, and even of a
substance so harmless, unresisting, and inert as cotton, nothing in the
way of mechanical achievement seems impossible, and it is hard to
restrain the imagination from wandering forward a couple of generations
to an epoch when our descendants shall have advanced as far beyond us in
physical conquest, as we have marched beyond the trophies erected by our
grandfathers.
I must therefore be understood to mean only, that no agencies now known
to man and directed by him seem adequate to the reducing of great Alpine
precipices to such slopes as would enable them to support a vegetable
clothing, or to the covering of large extents of denuded rock with
earth, and planting upon them a forest growth. But among the mysteries
which science is yet to reveal, there may be still undiscovered methods
of accomplishing even grander wonders than these. Mechanical
philosophers have suggested the possibility of accumulating and
treasuring up for human use some of the greater natural forces, which
the action of the elements puts forth with such astonishing energy.
Could we gather, and bind, and make subservient to our control, the
power which a West Indian hurricane exerts through a small area in one
continuous blast, or the momentum expended by the waves, in a
tempestuous winter, upon the breakwater at Cherbourg,[31] or the lifting
power of the tide, for a month, at the head of the Bay of Fundy, or the
pressure of a square mile of sea water at the depth of five thousand
fathoms, or a moment of the might of an earthquake or a volcano, our
age--which moves no mountains and casts them into the sea by faith
alone--might hope to scarp the rugged walls of the Alps and Pyrenees and
Mount Taurus, robe them once more in a vegetation as rich as that of
their pristine woods, and turn their wasting torrents into refreshing
streams.[32]
Could this old world, which man has overthrown, be rebuilded, could
human cunning rescue its wasted hillsides and its deserted plains from
solitude or mere nomade occupation, from barrenness, from nakedness, and
from insalubrity, and restore the ancient fertility and healthfulness of
the Etruscan sea coast, the Campagna and the Pontine marshes, of
Calabria, of Sicily, of the Peloponnesus and insular and continental
Greece, of Asia Minor, of the slopes of Lebanon and Hermon, of
Palestine, of the Syrian desert, of Mesopotamia and the delta of the
Euphrates, of the Cyrenaica, of Africa proper, Numidia, and Mauritania,
the thronging millions of Europe might still find room on the Eastern
continent, and the main current of emigration be turned toward the
rising instead of the setting sun.
But changes like these must await great political and moral revolutions
in the governments and peoples by whom those regions are now possessed,
a command of pecuniary and of mechanical means not at present enjoyed by
those nations, and a more advanced and generally diffused knowledge of
the processes by which the amelioration of soil and climate is possible,
than now anywhere exists. Until such circumstances shall conspire to
favor the work of geographical regeneration, the countries I have
mentioned, with here and there a local exception, will continue to sink
into yet deeper desolation, and in the mean time, the American
continent, Southern Africa, Australia, and the smaller oceanic islands,
will be almost the only theatres where man is engaged, on a great scale,
in transforming the face of nature.
_Arrest of Physical Decay of New Countries._
Comparatively short as is the period through which the colonization of
foreign lands by European emigrants extends, great, and, it is to be
feared, sometimes irreparable, injury has been already done in the
various processes by which man seeks to subjugate the virgin earth; and
many provinces, first trodden by the _homo sapiens Europæ_ within the
last two centuries, begin to show signs of that melancholy dilapidation
which is now driving so many of the peasantry of Europe from their
native hearths. It is evidently a matter of great moment, not only to
the population of the states where these symptoms are manifesting
themselves, but to the general interests of humanity, that this decay
should be arrested, and that the future operations of rural husbandry
and of forest industry, in districts yet remaining substantially in
their native condition, should be so conducted as to prevent the
widespread mischiefs which have been elsewhere produced by thoughtless
or wanton destruction of the natural safeguards of the soil. This can be
done only by the diffusion of knowledge on this subject among the
classes that, in earlier days, subdued and tilled ground in which they
had no vested rights, but who, in our time, own their woods, their
pastures, and their ploughlands as a perpetual possession for them and
theirs, and have, therefore, a strong interest in the protection of
their domain against deterioration.
_Forms and Formations most liable to Physical Degradation._
The character and extent of the evils under consideration depend very
much on climate and the natural forms and constitution of surface. If
the precipitation, whether great or small in amount, be equally
distributed through the seasons, so that there are neither torrential
rains nor parching droughts, and if, further, the general inclination of
ground be moderate, so that the superficial waters are carried off
without destructive rapidity of flow, and without sudden accumulation in
the channels of natural drainage, there is little danger of the
degradation of the soil in consequence of the removal of forest or other
vegetable covering, and the natural face of the earth may be considered
as substantially permanent. These conditions are well exemplified in
Ireland, in a great part of England, in extensive districts in Germany
and France, and, fortunately, in an immense proportion of the valley of
the Mississippi and the basin of the great American lakes, as well as in
many parts of the continents of South America and of Africa.
Destructive changes are most frequent in countries of irregular and
mountainous surface, and in climates where the precipitation is confined
chiefly to a single season, and where the year is divided into a wet and
a dry period, as is the case throughout a great part of the Ottoman
empire, and, more or less strictly, the whole Mediterranean basin. It is
partly, though by no means entirely, owing to topographical and climatic
causes that the blight, which has smitten the fairest and most fertile
provinces of Imperial Rome, has spared Britannia, Germania, Pannonia,
and M[oe]sia, the comparatively inhospitable homes of barbarous races,
who, in the days of the Cæsars, were too little advanced in civilized
life to possess either the power or the will to wage that war against
the order of nature which seems, hitherto, an almost inseparable
condition precedent of high social culture, and of great progress in
fine and mechanical art.[33]
In mountainous countries, on the other hand, various causes combine to
expose the soil to constant dangers. The rain and snow usually fall in
greater quantity, and with much inequality of distribution; the snow on
the summits accumulates for many months in succession, and then is not
unfrequently almost wholly dissolved in a single thaw, so that the
entire precipitation of months is in a few hours hurried down the flanks
of the mountains, and through the ravines that furrow them; the natural
inclination of the surface promotes the swiftness of the gathering
currents of diluvial rain and of melting snow, which soon acquire an
almost irresistible force, and power of removal and transportation; the
soil itself is less compact and tenacious than that of the plains, and
if the sheltering forest has been destroyed, it is confined by few of
the threads and ligaments by which nature had bound it together, and
attached it to the rocky groundwork. Hence every considerable shower
lays bare its roods of rock, and the torrents sent down by the thaws of
spring, and by occasional heavy discharges of the summer and autumnal
rains, are seas of mud and rolling stones that sometimes lay waste, and
bury beneath them acres, and even miles, of pasture and field and
vineyard.[34]
_Physical Decay of New Countries._
I have remarked that the effects of human action on the forms of the
earth's surface could not always be distinguished from those resulting
from geological causes, and there is also much uncertainty in respect to
the precise influence of the clearing and cultivating of the ground,
and of other rural operations, upon climate. It is disputed whether
either the mean or the extremes of temperature, the periods of the
seasons, or the amount or distribution of precipitation and of
evaporation, in any country whose annals are known, have undergone any
change during the historical period. It is, indeed, impossible to doubt
that many of the operations of the pioneer settler tend to produce great
modifications in atmospheric humidity, temperature, and electricity; but
we are at present unable to determine how far one set of effects is
neutralized by another, or compensated by unknown agencies. This
question scientific research is inadequate to solve, for want of the
necessary data; but well conducted observation, in regions now first
brought under the occupation of man, combined with such historical
evidence as still exists, may be expected at no distant period to throw
much light on this subject.
Australia is, perhaps, the country from which we have a right to expect
the fullest elucidation of these difficult and disputable problems. Its
colonization did not commence until the physical sciences had become
matter of almost universal attention, and is, indeed, so recent that the
memory of living men embraces the principal epochs of its history; the
peculiarities of its fauna, its flora, and its geology are such as to
have excited for it the liveliest interest of the votaries of natural
science; its mines have given its people the necessary wealth for
procuring the means of instrumental observation, and the leisure
required for the pursuit of scientific research; and large tracts of
virgin forest and natural meadow are rapidly passing under the control
of civilized man. Here, then, exist greater facilities and stronger
motives for the careful study of the topics in question than have ever
been found combined in any other theatre of European colonization.
In North America, the change from the natural to the artificial
condition of terrestrial surface began about the period when the most
important instruments of meteorological observation were invented. The
first settlers in the territory now constituting the United States and
the British American provinces had other things to do than to tabulate
barometrical and thermometrical readings, but there remain some
interesting physical records from the early days of the colonies,[35]
and there is still an immense extent of North American soil where the
industry and the folly of man have as yet produced little appreciable
change. Here, too, with the present increased facilities for scientific
observation, the future effects, direct and contingent, of man's labors,
can be measured, and such precautions taken in those rural processes
which we call improvements, as to mitigate evils, perhaps, in some
degree, inseparable from every attempt to control the action of natural
laws.
In order to arrive at safe conclusions, we must first obtain a more
exact knowledge of the topography, and of the present superficial and
climatic condition of countries where the natural surface is as yet more
or less unbroken. This can only be accomplished by accurate surveys, and
by a great multiplication of the points of meteorological registry,[36]
already so numerous; and as, moreover, considerable changes in the
proportion of forest and of cultivated land, or of dry and wholly or
partially submerged surface, will often take place within brief periods,
it is highly desirable that the attention of observers, in whose
neighborhood the clearing of the soil, or the drainage of lakes and
swamps, or other great works of rural improvement, are going on or
meditated, should be especially drawn not only to revolutions in
atmospheric temperature and precipitation, but to the more easily
ascertained and perhaps more important local changes produced by these
operations in the temperature and the hygrometric state of the
superficial strata of the earth, and in its spontaneous vegetable and
animal products.
The rapid extension of railroads, which now everywhere keeps pace with,
and sometimes even precedes, the occupation of new soil for agricultural
purposes, furnishes great facilities for enlarging our knowledge of the
topography of the territory they traverse, because their cuttings reveal
the composition and general structure of surface, and the inclination
and elevation of their lines constitute known hypsometrical sections,
which give numerous points of departure for the measurement of higher
and lower stations, and of course for determining the relief and
depression of surface, the slope of the beds of watercourses, and many
other not less important questions.[37]
The geological, hydrographical, and topographical surveys, which almost
every general and even local government of the civilized world is
carrying on, are making yet more important contributions to our stock of
geographical and general physical knowledge, and, within a comparatively
short space, there will be an accumulation of well established constant
and historical facts, from which we can safely reason upon all the
relations of action and reaction between man and external nature.
But we are, even now, breaking up the floor and wainscoting and doors
and window frames of our dwelling, for fuel to warm our bodies and
seethe our pottage, and the world cannot afford to wait till the slow
and sure progress of exact science has taught it a better economy. Many
practical lessons have been learned by the common observation of
unschooled men; and the teachings of simple experience, on topics where
natural philosophy has scarcely yet spoken, are not to be despised.
In these humble pages, which do not in the least aspire to rank among
scientific expositions of the laws of nature, I shall attempt to give
the most important practical conclusions suggested by the history of
man's efforts to replenish the earth and subdue it; and I shall aim to
support those conclusions by such facts and illustrations only as
address themselves to the understanding of every intelligent reader, and
as are to be found recorded in works capable of profitable perusal, or
at least consultation, by persons who have not enjoyed a special
scientific training.
CHAPTER II.
TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL
SPECIES.
MODERN GEOGRAPHY EMBRACES ORGANIC LIFE--TRANSFER OF VEGETABLE LIFE--
FOREIGN PLANTS GROWN IN THE UNITED STATES--AMERICAN PLANTS GROWS IN
EUROPE--MODES OF INTRODUCTION OF FOREIGN PLANTS--VEGETABLES, HOW
AFFECTED BY TRANSFER TO FOREIGN SOILS--EXTIRPATION OF VEGETABLES--
ORIGIN OF DOMESTIC PLANTS--ORGANIC LIFE AS A GEOLOGICAL AND GEOGRAPHICAL
AGENCY--ORIGIN AND TRANSFER OF DOMESTIC ANIMALS--EXTIRPATION OF
ANIMALS--NUMBERS OF BIRDS IN THE UNITED STATES--BIRDS AS SOWERS AND
CONSUMERS OF SEEDS, AND AS DESTROYERS OF INSECTS--DIMINUTION AND
EXTIRPATION OF BIRDS--INTRODUCTION OF BIRDS--UTILITY OF INSECTS AND
WORMS--INTRODUCTION OF INSECTS--DESTRUCTION OF INSECTS--REPTILES--
DESTRUCTION OF FISH--INTRODUCTION AND BREEDING OF FISH--EXTIRPATION
OF AQUATIC ANIMALS--MINUTE ORGANISMS.
_Modern Geography embraces Organic Life._
It was a narrow view of geography which confined that science to
delineation of terrestrial surface and outline, and to description of
the relative position and magnitude of land and water. In its improved
form, it embraces not only the globe itself, but the living things which
vegetate or move upon it, the varied influences they exert upon each
other, the reciprocal action and reaction between them and the earth
they inhabit. Even if the end of geographical studies were only to
obtain a knowledge of the external forms of the mineral and fluid masses
which constitute the globe, it would still be necessary to take into
account the element of life; for every plant, every animal, is a
geographical agency, man a destructive, vegetables, and even wild
beasts, restorative powers. The rushing waters sweep down earth from the
uplands; in the first moment of repose, vegetation seeks to reëstablish
itself on the bared surface, and, by the slow deposit of its decaying
products, to raise again the soil which the torrent had lowered. So
important an element of reconstruction is this, that it has been
seriously questioned whether, upon the whole, vegetation does not
contribute as much to elevate, as the waters to depress, the level of
the surface.
Whenever man has transported a plant from its native habitat to a new
soil, he has introduced a new geographical force to act upon it, and
this generally at the expense of some indigenous growth which the
foreign vegetable has supplanted. The new and the old plants are rarely
the equivalents of each other, and the substitution of an exotic for a
native tree, shrub, or grass, increases or diminishes the relative
importance of the vegetable element in the geography of the country to
which it is removed. Further, man sows that he may reap. The products of
agricultural industry are not suffered to rot upon the ground, and thus
raise it by an annual stratum of new mould. They are gathered,
transported to greater or less distances, and after they have served
their uses in human economy, they enter, on the final decomposition of
their elements, into new combinations, and are only in small proportion
returned to the soil on which they grew. The roots of the grasses, and
of many other cultivated plants, however, usually remain and decay in
the earth, and contribute to raise its surface, though certainly not in
the same degree as the forest.
The vegetables, which have taken the place of trees, unquestionably
perform many of the same functions. They radiate heat, they condense the
humidity of the atmosphere, they act upon the chemical constitution of
the air, their roots penetrate the earth to greater depths than is
commonly supposed, and form an inextricable labyrinth of filaments which
bind the soil together and prevent its erosion by water. The
broad-leaved annuals and perennials, too, shade the ground, and prevent
the evaporation of moisture from its surface by wind and sun.[38] At a
certain stage of growth, grass land is probably a more energetic
radiator and condenser than even the forest, but this powerful action is
exerted, in its full intensity, for a few days only, while trees
continue such functions, with unabated vigor, for many months in
succession. Upon the whole, it seems quite certain, that no cultivated
ground is as efficient in tempering climatic extremes, or in
conservation of geographical surface and outline, as is the soil which
nature herself has planted.
_Transfer of Vegetable Life._
It belongs to vegetable and animal geography, which are almost sciences
of themselves, to point out in detail what man has done to change the
distribution of plants and of animated life and to revolutionize the
aspect of organic nature; but some of the more important facts bearing
on this subject may pertinently be introduced here. Most of the fruit
trees grown in Europe and the United States are believed, and--if the
testimony of Pliny and other ancient naturalists is to be depended
upon--many of them are historically known, to have originated in the
temperate climates of Asia. The wine grape has been thought to be truly
indigenous only in the regions bordering on the eastern end of the Black
Sea, where it now, particularly on the banks of the Rion, the ancient
Phasis, propagates itself spontaneously, and grows with unexampled
luxuriance.[39] But, some species of the vine seem native to Europe, and
many varieties of grape have been too long known as common to every part
of the United States to admit of the supposition that they were all
introduced by European colonists.[40]
It is an interesting fact that the commerce--or at least the maritime
carrying trade--and the agricultural and mechanical industry of the
world are, in very large proportion, dependent on vegetable and animal
products little or not at all known to ancient Greek, Roman, and Jewish
civilization. In many instances, the chief supply of these articles
comes from countries to which they are probably indigenous, and where
they are still almost exclusively grown; but in many others, the plants
or animals from which they are derived have been introduced by man into
the regions now remarkable for their most successful cultivation, and
that, too, in comparatively recent times, or, in other words, within two
or three centuries.
_Foreign Plants grown in the United States._
According to Bigelow, the United States had, on the first of June, 1860,
in round numbers, 163,000,000 acres of improved land, the quantity
having been increased by 50,000,000 acres within the ten years next
preceding.[41] Not to mention less important crops, this land produced,
in the year ending on the day last mentioned, in round numbers,
171,000,000 bushels of wheat, 21,000,000 bushels of rye, 172,000,000
bushels of oats, 15,000,000 bushels of pease and beans, 16,000,000
bushels of barley, orchard fruits to the value of $20,000,000, 900,000
bushels of cloverseed, 900,000 bushels of other grass seed, 104,000 tons
of hemp, 4,000,000 pounds of flax, and 600,000 pounds of flaxseed. These
vegetable growths were familiar to ancient European agriculture, but
they were all introduced into North America after the close of the
sixteenth century.
Of the fruits of agricultural industry unknown to the Greeks and Romans,
or too little employed by them to be of any commercial importance, the
United States produced, in the same year, 187,000,000 pounds of rice,
18,000,000 bushels of buckwheat, 2,075,000,000 pounds of ginned
cotton,[42] 302,000,000 pounds of cane sugar, 16,000,000 gallons of
cane molasses, 7,000,000 gallons of sorghum molasses, all yielded by
vegetables introduced into that country within two hundred years,
and--with the exception of buckwheat, the origin of which is uncertain,
and of cotton--all, directly or indirectly, from the East Indies;
besides, from indigenous plants unknown to ancient agriculture,
830,000,000 bushels of Indian corn or maize, 429,000,000 pounds of
tobacco, 110,000,000 bushels of potatoes, 42,000,000 bushels of sweet
potatoes, 39,000,000 pounds of maple sugar, and 2,000,000 gallons of
maple molasses. To all this we are to add 19,000,000 tons of hay,
produced partly by new, partly by long known, partly by exotic, partly
by native herbs and grasses, an incalculable quantity of garden
vegetables, chiefly of European or Asiatic origin, and many minor
agricultural products.
The weight of this harvest of a year would be not less than 60,000,000
tons--which is eleven times the tonnage of all the shipping of the
United States at the close of the year 1861--and, with the exception of
the maple sugar, the maple molasses, and the products of the Western
prairie lands and some small Indian clearings, it was all grown upon
lands wrested from the forest by the European race within little more
than two hundred years. The wants of Europe have introduced into the
colonies of tropical America the sugar cane, the coffee plant, the
orange and the lemon,[43] all of Oriental origin, have immensely
stimulated the cultivation of the former two in the countries of which
they are natives, and, of course, promoted agricultural operations which
must have affected the geography of those regions to an extent
proportionate to the scale on which they have been pursued.
_American Plants grown in Europe._
America has partially repaid her debt to the Eastern continent. Maize
and the potato are very valuable additions to the field agriculture of
Europe and the East, and the tomato is no mean gift to the kitchen
gardens of the Old World, though certainly not an adequate return for
the multitude of esculent roots and leguminous plants which the European
colonists carried with them.[44] I wish I could believe, with some, that
America is not alone responsible for the introduction of the filthy
weed, tobacco, the use of which is the most vulgar and pernicious habit
engrafted by the semi-barbarism of modern civilization upon the less
multifarious sensualism of ancient life;[45] but the alleged occurrence
of pipe-like objects in Sclavonic, and, it has been said, in Hungarian
sepulchres, is hardly sufficient evidence to convict those races of
complicity in this grave offence against the temperance and the
refinement of modern society.
_Modes of Introduction of Foreign Plants._
Besides the vegetables I have mentioned, we know that many plants of
smaller economical value have been the subjects of international
exchange in very recent times. Busbequius, Austrian ambassador at
Constantinople about the middle of the sixteenth century--whose letters
contain one of the best accounts of Turkish life which have appeared
down to the present day--brought home from the Ottoman capital the lilac
and the tulip. The Belgian Clusius about the same time introduced from
the East the horse chestnut, which has since wandered to America. The
weeping willows of Europe and the United States are said to have sprung
from a slip received from Smyrna by the poet Pope, and planted by him in
an English garden; and the Portuguese declare that the progenitor of all
the European and American oranges was an Oriental tree transplanted to
Lisbon, and still living in the last generation.[46] The present
favorite flowers of the parterres of Europe have been imported from
America, Japan and other remote Oriental countries, within a century and
a half, and, in fine, there are few vegetables of any agricultural
importance, few ornamental trees or decorative plants, which are not now
common to the three civilized continents.
The statistics of vegetable emigration exhibit numerical results quite
surprising to those not familiar with the subject. The lonely island of
St. Helena is described as producing, at the time of its discovery in
the year 1501, about sixty vegetable species, including some three or
four known to grow elsewhere also. At the present time its flora numbers
seven hundred and fifty species. Humboldt and Bonpland found, among the
unquestionably indigenous plants of tropical America, monocotyledons
only, all the dicotyledons of those extensive regions having been
probably introduced after the colonization of the New World by Spain.
The faculty of spontaneous reproduction and perpetuation necessarily
supposes a greater power of accommodation, within a certain range, than
we find in most domesticated plants, for it would rarely happen that the
seed of a wild plant would fall into ground as nearly similar, in
composition and condition, to that where its parent grew, as the soils
of different fields artificially prepared for growing a particular
vegetable are to each other. Accordingly, though every wild species
affects a habitat of a particular character, it is found that, if
accidentally or designedly sown elsewhere, it will grow under conditions
extremely unlike those of its birthplace.[47] Cooper says: "We cannot
say positively that _any_ plant is _uncultivable_ anywhere until it has
been tried;" and this seems to be even more true of wild than of
domesticated vegetation.
The seven hundred new species which have found their way to St. Helena
within three centuries and a half, were certainly not all, or even in
the largest proportion, designedly planted there by human art, and if we
were well acquainted with vegetable emigration, we should probably be
able to show that man has intentionally transferred fewer plants than he
has accidentally introduced into countries foreign to them. After the
wheat, follow the tares that infest it. The weeds that grow among the
cereal grains, the pests of the kitchen garden, are the same in America
as in Europe.[48] The overturning of a wagon, or any of the thousand
accidents which befall the emigrant in his journey across the Western
plains, may scatter upon the ground the seeds he designed for his
garden, and the herbs which fill so important a place in the rustic
materia medica of the Eastern States, spring up along the prairie paths
but just opened by the caravan of the settler.[49] The hortus siccus of
a botanist may accidentally sow seeds from the foot of the Himalayas on
the plains that skirt the Alps; and it is a fact of very familiar
observation, that exotics, transplanted to foreign climates suited to
their growth, often escape from the flower garden and naturalize
themselves among the spontaneous vegetation of the pastures. When the
cases containing the artistic treasures of Thorvaldsen were opened in
the court of the museum where they are deposited, the straw and grass
employed in packing them were scattered upon the ground, and the next
season there sprang up from the seeds no less than twenty-five species
of plants belonging to the Roman campagna, some of which were preserved
and cultivated as a new tribute to the memory of the great Scandinavian
sculptor, and at least four are said to have spontaneously naturalized
themselves about Copenhagen.[50] In the campaign of 1814, the Russian
troops brought, in the stuffing of their saddles and by other accidental
means, seeds from the banks of the Dnieper to the valley of the Rhine,
and even introduced the plants of the steppes into the environs of
Paris. The Turkish armies, in their incursions into Europe, brought
Eastern vegetables in their train, and left the seeds of Oriental wall
plants to grow upon the ramparts of Buda and Vienna.[51] The Canada
thistle, _Erigeron Canadense_, is said to have sprung up in Europe, two
hundred years ago, from a seed which dropped out of the stuffed skin of
a bird.[52]
_Vegetables, how affected by Transfer to Foreign Soils._
Vegetables, naturalized abroad either by accident or design, sometimes
exhibit a greatly increased luxuriance of growth. The European cardoon,
an esculent thistle, has broken out from the gardens of the Spanish
colonies on the La Plata, acquired a gigantic stature, and propagated
itself, in impenetrable thickets, over hundreds of leagues of the
Pampas; and the _Anacharis alsinastrum_, a water plant not much inclined
to spread in its native American habitat, has found its way into English
rivers, and extended itself to such a degree as to form a serious
obstruction to the flow of the current, and even to navigation.
Not only do many wild plants exhibit a remarkable facility of
accommodation, but their seeds usually possess great tenacity of life,
and their germinating power resists very severe trials. Hence, while the
seeds of very many cultivated vegetables lose their vitality in two or
three years, and can be transported safely to distant countries only
with great precautions, the weeds that infest those vegetables, though
not cared for by man, continue to accompany him in his migrations, and
find a new home on every soil he colonizes. Nature fights in defence of
her free children, but wars upon them when they have deserted her
banners and tamely submitted to the dominion of man.[53]
Not only is the wild plant much hardier than the domesticated vegetable,
but the same law prevails in animated brute and even human life. The
beasts of the chase are more capable of endurance and privation and more
tenacious of life, than the domesticated animals which most nearly
resemble them. The savage fights on, after he has received half a dozen
mortal wounds, the least of which would have instantly paralyzed the
strength of his civilized enemy, and, like the wild boar,[54] he has
been known to press forward along the shaft of the spear which was
transpiercing his vitals, and to deal a deathblow on the soldier who
wielded it.
True, domesticated plants can be gradually acclimatized to bear a degree
of heat or of cold, which, in their wild state, they would not have
supported; the trained English racer outstrips the swiftest horse of the
pampas or prairies, perhaps even the less systematically educated
courser of the Arab; the strength of the European, as tested by the
dynamometer, is greater than that of the New Zealander. But all these
are instances of excessive development of particular capacities and
faculties at the expense of general vital power. Expose untamed and
domesticated forms of life, together, to an entire set of physical
conditions equally alien to the former habits of both, so that every
power of resistance and accommodation shall be called into action, and
the wild plant or animal will live, while the domesticated will perish.
The saline atmosphere of the sea is specially injurious both to seeds
and to very many young plants, and it is only recently that the
transportation of some very important vegetables across the ocean has
been made practicable, through the invention of Ward's airtight glass
cases. It is by this means that large numbers of the trees which produce
the Jesuit's bark have been successfully transplanted from America to
the British possessions in the East, where it is hoped they will become
fully naturalized.
_Extirpation of Vegetables._
Lamentable as are the evils produced by the too general felling of the
woods in the Old World, I believe it does not satisfactorily appear that
any species of native forest tree has yet been extirpated by man on the
Eastern continent. The roots, stumps, trunks, and foliage found in bogs
are recognized as belonging to still extant species. Except in some few
cases where there is historical evidence that foreign material was
employed, the timber of the oldest European buildings, and even of the
lacustrine habitations of Switzerland, is evidently the product of trees
still common in or near the countries where such architectural remains
are found; nor have the Egyptian catacombs themselves revealed to us the
former existence of any woods not now familiar to us as the growth of
still living trees.[55] It is, however, said that the yew tree, _Taxus
baccata_, formerly very common in England, Germany, and--as we are
authorized to infer from Theophrastus--in Greece, has almost wholly
disappeared from the latter country, and seems to be dying out in
Germany. The wood of the yew surpasses that of any other European tree
in closeness and fineness of grain, and it is well known for the
elasticity which of old made it so great a favorite with the English
archer. It is much in request among wood carvers and turners, and the
demand for it explains, in part, its increasing scarcity. It is also
worth remarking that no insect depends upon it for food or shelter, or
aids in its fructification, no bird feeds upon its berries--the latter a
circumstance of some importance, because the tree hence wants one means
of propagation or diffusion common to so many other plants. But it is
alleged that the reproductive power of the yew is exhausted, and that it
can no longer be readily propagated by the natural sowing of its seeds,
or by artificial methods. If further investigation and careful
experiment should establish this fact, it will go far to show that a
climatic change, of a character unfavorable to the growth of the yew,
has really taken place in Germany, though not yet proved by instrumental
observation, and the most probable cause of such change would be found
in the diminution of the area covered by the forests.
The industry of man is said to have been so successful in the local
extirpation of noxious or useless vegetables in China, that, with the
exception of a few water plants in the rice grounds, it is sometimes
impossible to find a single weed in an extensive district; and the late
eminent agriculturist, Mr. Coke, is reported to have offered in vain a
considerable reward for the detection of a weed in a large wheatfield on
his estate in England. In these cases, however, there is no reason to
suppose that diligent husbandry has done more than to eradicate the
pests of agriculture within a comparatively limited area, and the cockle
and the darnel will probably remain to plague the slovenly cultivator as
long as the cereal grains continue to bless him.[56]
_Origin of Domestic Plants._
One of the most important, and, at the same time, most difficult
questions connected with our subject is: how far we are to regard our
cereal grains, our esculent bulbs and roots, and the multiplied tree
fruits of our gardens, as artificially modified and improved forms of
wild, self-propagating vegetation. The narratives of botanical
travellers have often announced the discovery of the original form and
habitat of domesticated plants, and scientific journals have described
the experiments by which the identity of particular wild and cultivated
vegetables has been thought to be established. It is confidently
affirmed that maize and the potato--which we must suppose to have been
first cultivated at a much later period than the breadstuffs and most
other esculent vegetables of Europe and the East--are found wild and
self-propagating in Spanish America, though in forms not recognizable by
the common observer as identical with the familiar corn and tuber of
modern agriculture. It was lately asserted, upon what seemed very strong
evidence, that the _Ægilops ovata_, a plant growing wild in Southern
France, had been actually converted into common wheat; but, upon a
repetition of the experiments, later observers have declared that the
apparent change was only a case of temporary hybridation or fecundation
by the pollen of true wheat, and that the grass alleged to be
transformed into wheat could not be perpetuated as such from its own
seed.
The very great modifications which cultivated plants are constantly
undergoing under our eyes, and the numerous varieties and races which
spring up among them, certainly countenance the doctrine, that every
domesticated vegetable, however dependent upon human care for growth and
propagation in its present form, may have been really derived, by a long
succession of changes, from some wild plant not now much resembling it.
But it is, in every case, a question of evidence. The only satisfactory
proof that a given wild plant is identical with a given garden or field
vegetable, is the test of experiment, the actual growing of the one from
the seed of the other, or the conversion of the one into the other by
transplantation and change of conditions. It is hardly contended that
any of the cereals or other plants important as human aliment, or as
objects of agricultural industry, exist and propagate themselves
uncultivated in the same form and with the same properties as when sown
and reared by human art.[57] In fact, the cases are rare where the
identity of a wild with a domesticated plant is considered by the best
authorities as conclusively established, and we are warranted in
affirming of but few of the latter, as a historically known or
experimentally proved fact, that they ever did exist, or could exist,
independently of man.[58]
_Organic Life as a Geological and Geographical Agency._
The quantitative value of organic life, as a geological agency, seems to
be inversely as the volume of the individual organism; for nature
supplies by numbers what is wanting in the bulk of the plant or animal
out of whose remains or structures she forms strata covering whole
provinces, and builds up from the depths of the sea large islands, if
not continents. There are, it is true, near the mouths of the great
Siberian rivers which empty themselves into the Polar Sea, drift islands
composed, in an incredibly large proportion, of the bones and tusks of
elephants, mastodons, and other huge pachyderms, and many extensive
caves in various parts of the world are half filled with the skeletons
of quadrupeds, sometimes lying loose in the earth, sometimes cemented
together into an osseous breccia by a calcareous deposit or other
binding material. These remains of large animals, though found in
comparatively late formations, generally belong to extinct species, and
their modern congeners or representatives do not exist in sufficient
numbers to be of sensible importance in geology or in geography by the
mere mass of their skeletons.[59] But the vegetable products found with
them, and, in rare cases, in the stomachs of some of them, are those of
yet extant plants; and besides this evidence, the recent discovery of
works of human art, deposited in juxtaposition with fossil bones, and
evidently at the same time and by the same agency which buried these
latter--not to speak of alleged human bones found in the same
strata--proves that the animals whose former existence they testify were
contemporaneous with man, and possibly even extirpated by him.[60] I do
not propose to enter upon the thorny question, whether the existing
races of man are genealogically connected with these ancient types of
humanity, and I advert to these facts only for the sake of the
suggestion that man, in his earliest known stages of existence, was
probably a destructive power upon the earth, though perhaps not so
emphatically as his present representatives.
The larger wild animals are not now numerous enough in any one region to
form extensive deposits by their remains; but they have, nevertheless, a
certain geographical importance. If the myriads of large browsing and
grazing quadrupeds which wander over the plains of Southern Africa--and
the slaughter of which by thousands is the source of a ferocious
pleasure and a brutal triumph to professedly civilized hunters--if the
herds of the American bison, which are numbered by hundreds of
thousands, do not produce visible changes in the forms of terrestrial
surface, they have at least an immense influence on the growth and
distribution of vegetable life, and, of course, indirectly upon all the
physical conditions of soil and climate between which and vegetation a
mutual interdependence exists.
The influence of wild quadrupeds upon vegetable life has been little
studied, and not many facts bearing upon it have been recorded, but, so
far as it is known, it appears to be conservative rather than
pernicious.[61] Few if any of them depend for their subsistence on
vegetable products obtainable only by the destruction of the plant, and
they seem to confine their consumption almost exclusively to the annual
harvest of leaf or twig, or at least of parts of the vegetable easily
reproduced. If there are exceptions to this rule, they are in cases
where the numbers of the animal are so proportioned to the abundance of
the vegetable, that there is no danger of the extermination of the plant
from the voracity of the quadruped, or of the extinction of the
quadruped from the scarcity of the plant. In diet and natural wants the
bison resembles the ox, the ibex and the chamois assimilate themselves
to the goat and the sheep; but while the wild animal does not appear to
be a destructive agency in the garden of nature, his domestic congeners
are eminently so. This is partly from the change of habits resulting
from domestication and association with man, partly from the fact that
the number of reclaimed animals is not determined by the natural
relation of demand and spontaneous supply which regulates the
multiplication of wild creatures, but by the convenience of man, who is,
in comparatively few things, amenable to the control of the merely
physical arrangements of nature. When the domesticated animal escapes
from human jurisdiction, as in the case of the ox, the horse, the goat,
and perhaps the ass--which, so far as I know, are the only
well-authenticated instances of the complete emancipation of household
quadrupeds--he becomes again an unresisting subject of nature, and all
his economy is governed by the same laws as that of his fellows which
have never been enslaved by man; but, so long as he obeys a human lord,
he is an auxiliary in the warfare his master is ever waging against all
existences except those which he can tame to a willing servitude.
_Number of Quadrupeds in the United States._
Civilization is so intimately associated with, if not dependent upon,
certain inferior forms of animal life, that cultivated man has never
failed to accompany himself, in all his migrations, with some of these
humble attendants. The ox, the horse, the sheep, and even the
comparatively useless dog and cat, as well as several species of
poultry, are voluntarily transported by every emigrant colony, and they
soon multiply to numbers very far exceeding those of the wild genera
most nearly corresponding to them.[62] According to the census of the
United States for 1860,[63] the total number of horses in all the
States of the American Union, was, in round numbers, 7,300,000; of asses
and mules, 1,300,000; of the ox tribe, 29,000,000;[64] of sheep,
25,000,000; and of swine, 39,000,000. The only North American quadruped
sufficiently gregarious in habits, and sufficiently multiplied in
numbers, to form really large herds, is the bison, or, as he is commonly
called in America, the buffalo; and this animal is confined to the
prairie region of the Mississippi basin and Northern Mexico. The
engineers sent out to survey railroad routes to the Pacific estimated
the number of a single herd of bisons seen within the last ten years on
the great plains near the Upper Missouri, at not less than 200,000, and
yet the range occupied by this animal is now very much smaller in area
than it was when the whites first established themselves on the
prairies.[65] But it must be remarked that the American buffalo is a
migratory animal, and that, at the season of his annual journeys, the
whole stock of a vast extent of pasture ground is collected into a
single army, which is seen at or very near any one point only for a few
days during the entire season. Hence there is risk of great error in
estimating the numbers of the bison in a given district from the
magnitude of the herds seen at or about the same time at a single place
of observation; and, upon the whole, it is neither proved nor probable
that the bison was ever, at any one time, as numerous in North America
as the domestic bovine species is at present. The elk, the moose, the
musk ox, the caribou, and the smaller quadrupeds popularly embraced
under the general name of deer,[66] though sufficient for the wants of a
sparse savage population, were never numerically very abundant, and the
carnivora which fed upon them were still less so. It is almost needless
to add that the Rocky Mountain sheep and goat must always have been very
rare.
Summing up the whole, then, it is evident that the wild quadrupeds of
North America, even when most numerous, were few compared with their
domestic successors, that they required a much less supply of vegetable
food, and consequently were far less important as geographical elements
than the many millions of hoofed and horned cattle now fed by civilized
man on the same continent.
_Origin and Transfer of Domestic Quadrupeds._
Of the origin of our domestic animals, we know historically nothing,
because their domestication belongs to the ages which preceded written
history; but though they cannot all be specifically identified with now
extant wild animals, it is presumable that they have been reclaimed from
an originally wild state. Ancient annalists have preserved to us fewer
data respecting the introduction of domestic animals into new countries
than respecting the transplantation of domestic vegetables. Ritter, in
his learned essay on the camel, has shown that this animal was not
employed by the Egyptians until a comparatively late period in their
history; that he was unknown to the Carthaginians until after the
downfall of their commonwealth; and that his first appearance in Western
Africa is more recent still. The Bactrian camel was certainly brought
from Asia Minor to the Northern shores of the Black Sea, by the Goths,
in the third or fourth century.[67] The Arabian single-humped camel, or
dromedary, has been carried to the Canary Islands, partially introduced
into Australia, Greece, Spain, and even Tuscany, experimented upon to
little purpose in Venezuela, and finally imported by the American
Government into Texas and New Mexico, where it finds the climate and the
vegetable products best suited to its wants, and promises to become a
very useful agent in the promotion of the special civilization for which
those regions are adapted. America had no domestic quadruped but a
species of dog, the lama tribe, and, to a certain extent, the bison or
buffalo.[68] Of course, it owes the horse, the ass, the ox, the sheep,
the goat, and the swine, as does also Australia, to European
colonization. Modern Europe has, thus far, not accomplished much in the
way of importation of new animals, though some interesting essays have
been made. The reindeer was successfully introduced into Iceland about a
century ago, while similar attempts failed, about the same time, in
Scotland. The Cashmere or Thibet goat was brought to France a generation
since, and succeeds well. The same or an allied species and the Asiatic
buffalo were carried to South Carolina about the year 1850, and the
former, at least, is thought likely to prove of permanent value in the
United States. The yak, or Tartary ox, seems to thrive in France, and
success has attended the recent efforts to introduce the South American
alpaca into Europe.
_Extirpation of Quadrupeds._
Although man never fails greatly to diminish, and is perhaps destined
ultimately to exterminate, such of the larger wild quadrupeds as he
cannot profitably domesticate, yet their numbers often fluctuate, and
even after they seem almost extinct, they sometimes suddenly increase,
without any intentional steps to promote such a result on his part.
During the wars which followed the French Revolution, the wolf
multiplied in many parts of Europe, partly because the hunters were
withdrawn from the woods to chase a nobler game, and partly because the
bodies of slain men and horses supplied this voracious quadruped with
more abundant food. The same animal became again more numerous in Poland
after the general disarming of the rural population by the Russian
Government. On the other hand, when the hunters pursue the wolf, the
graminivorous wild quadrupeds increase, and thus in turn promote the
multiplication of their great four-footed destroyer by augmenting the
supply of his nourishment. So long as the fur of the beaver was
extensively employed as a material for fine hats, it bore a very high
price, and the chase of this quadruped was so keen that naturalists
feared its speedy extinction. When a Parisian manufacturer invented the
silk hat, which soon came into almost universal use, the demand for
beavers' fur fell off, and this animal--whose habits, as we have seen,
are an important agency in the formation of bogs and other modifications
of forest nature--immediately began to increase, reappeared in haunts
which he had long abandoned, and can no longer be regarded as rare
enough to be in immediate danger of extirpation. Thus the convenience or
the caprice of Parisian fashion has unconsciously exercised an influence
which may sensibly affect the physical geography of a distant continent.
Since the invention of gunpowder, some quadrupeds have completely
disappeared from many European and Asiatic countries where they were
formerly numerous. The last wolf was killed in Great Britain two hundred
years ago, and the bear was extirpated from that island still earlier.
The British wild ox exists only in a few English and Scottish parks,
while in Irish bogs, of no great apparent antiquity, are found antlers
which testify to the former existence of a stag much larger than any
extant European species. The lion is believed to have inhabited Asia
Minor and Syria, and probably Greece and Sicily also, long after the
commencement of the historical period, and he is even said to have been
not yet extinct in the first-named two of these countries at the time of
the first Crusades.[69] Two large graminivorous or browsing quadrupeds,
the ur and the schelk, once common in Germany, are utterly extinct, the
eland and the auerochs nearly so. The Nibelungen-Lied, which, in the
oldest form preserved to us, dates from about the year 1,200, though its
original composition no doubt belongs to an earlier period, thus sings:
Then slowe the dowghtie Sigfrid a wisent and an elk,
He smote four stoute uroxen and a grim and sturdie schelk.[70]
Modern naturalists identify the elk with the eland, the wisent with the
auerochs. The period when the ur and the schelk became extinct is not
known. The auerochs survived in Prussia until the middle of the last
century, but unless it is identical with a similar quadruped said to be
found on the Caucasus, it now exists only in the Russian imperial forest
of Bialowitz, where about a thousand are still preserved, and in some
great menageries, as for example that at Schönbrunn, near Vienna, which,
in 1852, had four specimens. The eland, which is closely allied to the
American wapiti, if not specifically the same animal, is still kept in
the royal preserves of Prussia, to the number of four or five hundred
individuals. The chamois is becoming rare, and the ibex or steinbock,
once common in all the high Alps, is now believed to be confined to the
Cogne mountains in Piedmont, between the valleys of the Dora Baltea and
the Orco.
_Number of Birds in the United States._
The tame fowls play a much less conspicuous part in rural life than the
quadrupeds, and, in their relations to the economy of nature, they are
of very much less moment than four-footed animals, or than the
undomesticated birds. The domestic turkey[71] is probably more numerous
in the territory of the United States than the wild bird of the same
species ever was, and the grouse cannot, at the period of their greatest
abundance, have counted as many as we now number of the common hen. The
dove, however, must fall greatly short of the wild pigeon in multitude,
and it is hardly probable that the flocks of domestic geese and ducks
are as numerous as once were those of their wild congeners. The pigeon,
indeed, seems to have multiplied immensely, for some years after the
first clearings in the woods, because the settlers warred unsparingly
upon the hawk, while the crops of grain and other vegetable growths
increased the supply of food within the reach of the young birds, at the
age when their power of flight is not yet great enough to enable them
to seek it over a wide area.[72] The pigeon is not described by the
earliest white inhabitants of the American States as filling the air
with such clouds of winged life as astonish naturalists in the
descriptions of Audubon, and, at the present day, the net and the gun
have so reduced its abundance, that its appearance in large numbers is
recorded only at long intervals, and it is never seen in the great
flocks remembered by many still living observers as formerly very
common.
_Birds as Sowers and Consumers of Seeds, and as Destroyers of Insects._
Wild birds form of themselves a very conspicuous and interesting feature
in the _staffage_, as painters call it, of the natural landscape, and
they are important elements in the view we are taking of geography,
whether we consider their immediate or their incidental influence. Birds
affect vegetation directly by sowing seeds and by consuming them; they
affect it indirectly by destroying insects injurious, or, in some cases,
beneficial to vegetable life. Hence, when we kill a seed-sowing bird, we
check the dissemination of a plant; when we kill a bird which digests
the seed it swallows, we promote the increase of a vegetable. Nature
protects the seeds of wild, much more effectually than those of
domesticated plants. The cereal grains are completely digested when
consumed by birds, but the germ of the smaller stone fruits and of very
many other wild vegetables is uninjured, perhaps even stimulated to more
vigorous growth, by the natural chemistry of the bird's stomach. The
power of flight and the restless habits of the bird enable it to
transport heavy seeds to far greater distances than they could be
carried by the wind. A swift-winged bird may drop cherry stones a
thousand miles from the tree they grow on; a hawk, in tearing a pigeon,
may scatter from its crop the still fresh rice it had swallowed at a
distance of ten degrees of latitude,[73] and thus the occurrence of
isolated plants in situations where their presence cannot otherwise well
be explained, is easily accounted for. There is a large class of seeds
apparently specially fitted by nature for dissemination by animals. I
refer to those which attach themselves, by means of hooks, or by viscous
juices, to the coats of quadrupeds and the feathers of birds, and are
thus transported wherever their living vehicles may chance to wander.
Some birds, too, deliberately bury seeds, not indeed with a foresight
aiming directly at the propagation of the plant, but from apparently
purposeless secretiveness, or as a mode of preserving food for future
use.
An unfortunate popular error greatly magnifies the injury done to the
crops of grain and leguminous vegetables by wild birds. Very many of
those generally supposed to consume large quantities of the seeds of
cultivated plants really feed almost exclusively upon insects, and
frequent the wheatfields, not for the sake of the grain, but for the
eggs, larvæ, and fly of the multiplied tribes of insect life which are
so destructive to the harvests. This fact has been so well established
by the examination of the stomachs of great numbers of birds in Europe
and New England, at different seasons of the year, that it is no longer
open to doubt, and it appears highly probable that even the species
which consume more or less grain generally make amends, by destroying
insects whose ravages would have been still more injurious.[74] On this
subject, we have much other evidence besides that derived from
dissection. Direct observation has shown, in many instances, that the
destruction of wild birds has been followed by a great multiplication of
noxious insects, and, on the other hand, that these latter have been
much reduced in numbers by the protection and increase of the birds that
devour them. Many interesting facts of this nature have been collected
by professed naturalists, but I shall content myself with a few taken
from familiar and generally accessible sources. The following extract is
from Michelet, _L'Oiseau_ pp. 169, 170:
"The _stingy_ farmer--an epithet justly and feelingly bestowed by
Virgil. Avaricious, blind, indeed, who proscribes the birds--those
destroyers of insects, those defenders of his harvests. Not a grain for
the creature which, during the rains of winter, hunts the future insect,
finds out the nests of the larvæ, examines, turns over every leaf, and
destroys, every day, thousands of incipient caterpillars. But sacks of
corn for the mature insect, whole fields for the grasshoppers, which the
bird would have made war upon. With eyes fixed upon his furrow, upon the
present moment only, without seeing and without foreseeing, blind to the
great harmony which is never broken with impunity, he has everywhere
demanded or approved laws for the extermination of that necessary ally
of his toil--the insectivorous bird. And the insect has well avenged the
bird. It has become necessary to revoke in haste the proscription. In
the Isle of Bourbon, for instance, a price was set on the head of the
martin; it disappeared, and the grasshoppers took possession of the
island, devouring, withering, scorching with a biting drought all that
they did not consume. In North America it has been the same with the
starling, the protector of Indian corn.[75] Even the sparrow, which
really does attack grain, but which protects it still more, the
pilferer, the outlaw, loaded with abuse and smitten with curses--it has
been found in Hungary that they were likely to perish without him, that
he alone could sustain the mighty war against the beetles and the
thousand winged enemies that swarm in the lowlands; they have revoked
the decree of banishment, recalled in haste this valiant militia, which,
though deficient in discipline, is nevertheless the salvation of the
country.[76]
"Not long since, in the neighborhood of Rouen and in the valley of
Monville, the blackbird was for some time proscribed. The beetles
profited well by this proscription; their larvæ, infinitely multiplied,
carried on their subterranean labors with such success, that a meadow
was shown me, the surface of which was completely dried up, every
herbaceous root was consumed, and the whole grassy mantle, easily
loosened, might have been rolled up and carried away like a carpet."
_Diminution and Extirpation of Birds._
The general hostility of the European populace to the smaller birds is,
in part, the remote effect of the reaction created by the game laws.
When the restrictions imposed upon the chase by those laws were suddenly
removed in France, the whole people at once commenced a destructive
campaign against every species of wild animal. Arthur Young, writing in
Provence, on the 30th of August, 1789, soon after the National Assembly
had declared the chase free, thus complains of the annoyance he
experienced from the use made by the peasantry of their newly won
liberty. "One would think that every rusty firelock in all Provence was
at work in the indiscriminate destruction of all the birds. The wadding
buzzed by my ears, or fell into my carriage, five or six times in the
course of the day." * * "The declaration of the Assembly that every man
is free to hunt on his own land * * has filled all France with an
intolerable cloud of sportsmen. * * The declaration speaks of
compensations and indemnities [to the _seigneurs_], but the ungovernable
populace takes advantage of the abolition of the game laws and laughs at
the obligation imposed by the decree."
The French Revolution removed similar restrictions, with similar
results, in other countries. The habits then formed have become
hereditary on the Continent, and though game laws still exist in
England, there is little doubt that the blind prejudices of the ignorant
and half-educated classes in that country against birds are, in some
degree, at least, due to a legislation, which, by restricting the chase
of all game worth killing, drives the unprivileged sportsman to
indemnify himself by slaughtering all wild life which is not reserved
for the amusement of his betters. Hence the lord of the manor buys his
partridges and his hares by sacrificing the bread of his tenants, and so
long as the farmers of Crawley are forbidden to follow higher game, they
will suicidally revenge themselves by destroying the sparrows which
protect their wheatfields.
On the Continent, and especially in Italy, the comparative scarcity and
dearness of animal food combine with the feeling I have just mentioned
to stimulate still further the destructive passions of the fowler. In
the Tuscan province of Grosseto, containing less than 2,000 square
miles, nearly 300,000 thrushes and other small birds are annually
brought to market.[77]
Birds are less hardy in constitution, they possess less facility of
accommodation,[78] and they are more severely affected by climatic
excess than quadrupeds. Besides, they generally want the means of
shelter against the inclemency of the weather and against pursuit by
their enemies, which holes and dens afford to burrowing animals and to
some larger beasts of prey. The egg is exposed to many dangers before
hatching, and the young bird is especially tender, defenceless, and
helpless. Every cold rain, every violent wind, every hailstorm during
the breeding season, destroys hundreds of nestlings, and the parent
often perishes with her progeny while brooding over it in the vain
effort to protect it.[79] The great proportional numbers of birds, their
migratory habits, and the ease with which they may escape most dangers
that beset them, would seem to secure them from extirpation, and even
from very great numerical reduction. But experience shows that when not
protected by law, by popular favor or superstition, or by other special
circumstances, they yield very readily to the hostile influences of
civilization, and, though the first operations of the settler are
favorable to the increase of many species, the great extension of rural
and of mechanical industry is, in a variety of ways, destructive even to
tribes not directly warred upon by man.[80]
Nature sets bounds to the disproportionate increase of birds, while at
the same time, by the multitude of their resources, she secures them
from extinction through her own spontaneous agencies. Man both preys
upon them and wantonly destroys them. The delicious flavor of game
birds, and the skill implied in the various arts of the sportsman who
devotes himself to fowling, make them favorite objects of the chase,
while the beauty of their plumage, as a military and feminine
decoration, threatens to involve the sacrifice of the last survivor of
many once numerous species. Thus far, but few birds described by ancient
or modern naturalists are known to have become absolutely extinct,
though there are some cases in which they are ascertained to have
utterly disappeared from the face of the earth in very recent times. The
most familiar instances are those of the dodo, a large bird peculiar to
the Mauritius or Isle of France, exterminated about the year 1690, and
now known only by two or three fragments of skeletons, and the solitary,
which inhabited the islands of Bourbon and Rodriguez, but has not been
seen for more than a century. A parrot and some other birds of the
Norfolk Island group are said to have lately become extinct. The
wingless auk, _Alca impennis_, a bird remarkable for its excessive
fatness, was very abundant two or three hundred years ago in the Faroe
Islands, and on the whole Scandinavian seaboard. The early voyagers
found either the same or a closely allied species, in immense numbers,
on all the coasts and islands of Newfoundland. The value of its flesh
and its oil made it one of the most important resources of the
inhabitants of those sterile regions, and it was naturally an object of
keen pursuit. It is supposed to be now completely extinct, and few
museums can show even its skeleton.
There seems to be strong reason to believe that our boasted modern
civilization is guiltless of one or two sins of extermination which have
been committed in recent ages. New Zealand formerly possessed three
species of dinornis, one of which, called _moa_ by the islanders, was
much larger than the ostrich. The condition in which the bones of these
birds have been found and the traditions of the natives concur to prove
that, though the aborigines had probably extirpated them before the
discovery of New Zealand by the whites, they still existed at a
comparatively late period. The same remarks apply to a winged giant the
eggs of which have been brought from Madagascar. This bird must have
much exceeded the dimensions of the moa, at least so far as we can judge
from the egg, which is eight times as large as the average size of the
ostrich egg, or about one hundred and fifty times that of the hen.
But though we have no evidence that man has exterminated many species of
birds, we know that his persecutions have caused their disappearance
from many localities where they once were common, and greatly diminished
their numbers in others. The cappercailzie, _Tetrao urogallus_, the
finest of the grouse family, formerly abundant in Scotland, had become
extinct in Great Britain, but has been reintroduced from Sweden.[81] The
ostrich is mentioned by all the old travellers, as common on the
Isthmus of Suez down to the middle of the seventeenth century. It
appears to have frequented Syria and even Asia Minor at earlier periods,
but is now found only in the seclusion of remoter deserts.
The modern increased facilities of transportation have brought distant
markets within reach of the professional hunter, and thereby given a new
impulse to his destructive propensities. Not only do all Great Britain
and Ireland contribute to the supply of game for the British capital,
but the canvas-back duck of the Potomac, and even the prairie hen from
the basin of the Mississippi, may be found at the stalls of the London
poulterer. Kohl[82] informs us that on the coasts of the North Sea,
twenty thousand wild ducks are usually taken in the course of the season
in a single decoy, and sent to the large maritime towns for sale. The
statistics of the great European cities show a prodigious consumption of
game birds, but the official returns fall far below the truth, because
they do not include the rural districts, and because neither the poacher
nor his customers report the number of his victims. Reproduction, in
cultivated countries, cannot keep pace with this excessive destruction,
and there is no doubt that all the wild birds which are chased for their
flesh or their plumage are diminishing with a rapidity which justifies
the fear that the last of them will soon follow the dodo and the
wingless auk.
Fortunately the larger birds which are pursued for their flesh or for
their feathers, and those the eggs of which are used as food, are, so
far as we know the functions appointed to them by nature, not otherwise
specially useful to man, and, therefore, their wholesale destruction is
an economical evil only in the same sense in which all waste of
productive capital is an evil. If it were possible to confine the
consumption of game fowl to a number equal to the annual increase, the
world would be a gainer, but not to the same extent as it would be by
checking the wanton sacrifice of millions of the smaller birds, which
are of no real value as food, but which, as we have seen, render a most
important service by battling, in our behalf, as well as in their own,
against the countless legions of humming and of creeping things, with
which the prolific powers of insect life would otherwise cover the
earth.
_Introduction of Birds._
Man has undesignedly introduced into new districts perhaps fewer species
of birds than of quadrupeds; but the distribution of birds is very much
influenced by the character of his industry, and the transplantation of
every object of agricultural production is, at a longer or shorter
interval, followed by that of the birds which feed upon its seeds, or
more frequently upon the insects it harbors. The vulture, the crow, and
other winged scavengers, follow the march of armies as regularly as the
wolf. Birds accompany ships on long voyages, for the sake of the offal
which is thrown overboard, and, in such cases, it might often happen
that they would breed and become naturalized in countries where they had
been unknown before.[83] There is a familiar story of an English bird
which built its nest in an unused block in the rigging of a ship, and
made one or two short voyages with the vessel while hatching its eggs.
Had the young become fledged while lying in a foreign harbor, they would
of course have claimed the rights of citizenship in the country where
they first took to the wing.[84]
Some enthusiastic entomologist will, perhaps, by and by discover that
insects and worms are as essential as the larger organisms to the proper
working of the great terraqueous machine, and we shall have as eloquent
pleas in defence of the mosquito, and perhaps even of the tzetze fly, as
Toussenel and Michelet have framed in behalf of the bird.[85] The
silkworm and the bee need no apologist; a gallnut produced by the
puncture of an insect on a Syrian oak is a necessary ingredient in the
ink I am writing with, and from my windows I recognize the grain of the
kermes and the cochineal in the gay habiliments of the holiday groups
beneath them. But agriculture, too, is indebted to the insect and the
worm. The ancients, according to Pliny, were accustomed to hang
branches of the wild fig upon the domestic tree, in order that the
insects which frequented the former might hasten the ripening of the
cultivated fig by their punctures--or, as others suppose, might fructify
it by transporting to it the pollen of the wild fruit--and this process,
called caprification, is not yet entirely obsolete. The earthworms long
ago made good their title to the respect and gratitude of the farmer as
well as of the angler. The utility of the earthworms has been pointed
out in many scientific as well as in many agricultural treatises. The
following extract, cut from a newspaper, will answer my present purpose:
"Mr. Josiah Parkes, the consulting engineer of the Royal Agricultural
Society of England, says that worms are great assistants to the drainer,
and valuable aids to the farmer in keeping up the fertility of the soil.
He says they love moist, but not wet soils; they will bore down to, but
not into water; they multiply rapidly on land after drainage, and prefer
a deeply dried soil. On examining with Mr. Thomas Hammond, of Penhurst,
Kent, part of a field which he had deeply drained, after long-previous
shallow drainage, he found that the worms had greatly increased in
number, and that their bores descended quite to the level of the pipes.
Many worm bores were large enough to receive the little finger. Mr.
Henry Handley had informed him of a piece of land near the sea in
Lincolnshire, over which the sea had broken and killed all the
worms--the field remained sterile until the worms again inhabited it. He
also showed him a piece of pasture land near to his house, in which
worms were in such numbers that he thought their casts interfered too
much with its produce, which induced him to have it rolled at night in
order to destroy the worms. The result was, that the fertility of the
field greatly declined, nor was it restored until they had recruited
their numbers, which was aided by collecting and transporting multitudes
of worms from the fields.
"The great depth into which worms will bore, and from which they push up
fine fertile soil, and cast it on the surface, has been admirably traced
by Mr. C. Darwin, of Down, Kent, who has shown that in a few years they
have actually elevated the surface of fields by a large layer of rich
mould, several inches thick--thus affording nourishment to the roots of
grasses, and increasing the productiveness of the soil."
It should be added that the writer quoted, and others who have discussed
the subject, have overlooked one very important element in the
fertilization produced by earthworms. I refer to the enrichment of the
soil by their excreta during life, and by the decomposition of their
remains when they die. The manure thus furnished is as valuable as the
like amount of similar animal products derived from higher organisms,
and when we consider the prodigious numbers of these worms found on a
single square yard of some soils, we may easily see that they furnish no
insignificant contribution to the nutritive material required for the
growth of plants.[86]
The perforations of the earthworm mechanically affect the texture of the
soil and its permeability by water, and they therefore have a certain
influence on the form and character of surface. But the geographical
importance of insects proper, as well as of worms, depends principally
on their connection with vegetable life as agents of its fecundation,
and of its destruction.[87] I am acquainted with no single fact so
strikingly illustrative of this importance, as the following statement
which I take from a notice of Darwin's volume, On Various Contrivances
by which British and Foreign Orchids are Fertilized by Insects, in the
_Saturday Review_, of October 18, 1862: "The net result is, that some
six thousand species of orchids are absolutely dependent upon the agency
of insects for their fertilization. That is to say, were those plants
unvisited by insects, they would all rapidly disappear." What is true of
the orchids is more or less true of many other vegetable families. We do
not know the limits of this agency, and many of the insects habitually
regarded as unqualified pests, may directly or indirectly perform
functions as important to the most valuable plants as the services
rendered by certain tribes to the orchids. I say directly or indirectly,
because, besides the other arrangements of nature for checking the undue
multiplication of particular species, she has established a police among
insects themselves, by which some of them keep down or promote the
increase of others; for there are insects, as well as birds and beasts,
of prey. The existence of an insect which fertilizes a useful vegetable
may depend on that of another, which constitutes his food in some stage
of his life, and this other again may be as injurious to some plant as
his destroyer is beneficial to another. The equation of animal and
vegetable life is too complicated a problem for human intelligence to
solve, and we can never know how wide a circle of disturbance we produce
in the harmonies of nature when we throw the smallest pebble into the
ocean of organic life.
This much, however, we seem authorized to conclude: as often as we
destroy the balance by deranging the original proportions between
different orders of spontaneous life, the law of self-preservation
requires us to restore the equilibrium, by either directly returning the
weight abstracted from one scale, or removing a corresponding quantity
from the other. In other words, destruction must be either repaired by
reproduction, or compensated by new destruction in an opposite quarter.
The parlor aquarium has taught even those to whom it is but an amusing
toy, that the balance of animal and vegetable life must be preserved,
and that the excess of either is fatal to the other, in the artificial
tank as well as in natural waters. A few years ago, the water of the
Cochituate aqueduct at Boston became so offensive in smell and taste as
to be quite unfit for use. Scientific investigation found the cause in
the too scrupulous care with which aquatic vegetation had been excluded
from the reservoir, and the consequent death and decay of the animalculæ
which could not be shut out, nor live in the water without the vegetable
element.[88]
_Introduction of Insects._
The general tendency of man's encroachments upon spontaneous nature has
been to increase insect life at the expense of vegetation and of the
smaller quadrupeds and birds. Doubtless there are insects in all woods,
but in temperate climates they are comparatively few and harmless, and
the most numerous tribes which breed in the forest, or rather in its
waters, and indeed in all solitudes, are those which little injure
vegetation, such as mosquitoes, gnats, and the like. With the cultivated
plants of man come the myriad tribes which feed or breed upon them, and
agriculture not only introduces new species, but so multiplies the
number of individuals as to defy calculation. Newly introduced
vegetables frequently escape for years the insect plagues which had
infested them in their native habitat; but the importation of other
varieties of the plant, the exchange of seed, or some mere accident, is
sure in the long run to carry the egg, the larva, or the chrysalis to
the most distant shores where the plant assigned to it by nature as its
possession has preceded it. For many years after the colonization of the
United States, few or none of the insects which attack wheat in its
different stages of growth, were known in America. During the
Revolutionary war, the Hessian fly, _Cecidomyia destructor_, made its
appearance, and it was so called because it was first observed in the
year when the Hessian troops were brought over, and was popularly
supposed to have been accidentally imported by those unwelcome
strangers. Other destroyers of cereal grains have since found their way
across the Atlantic, and a noxious European aphis has first attacked the
American wheatfields within the last four or five years. Unhappily, in
these cases of migration, the natural corrective of excessive
multiplication, the parasitic or voracious enemy of the noxious insect,
does not always accompany the wanderings of its prey, and the bane long
precedes the antidote. Hence, in the United States, the ravages of
imported insects injurious to cultivated crops, not being checked by the
counteracting influences which nature had provided to limit their
devastations in the Old World, are much more destructive than in Europe.
It is not known that the wheat midge is preyed upon in America by any
other insect, and in seasons favorable to it, it multiplies to a degree
which would prove almost fatal to the entire harvest, were it not that,
in the great territorial extent of the United States, there is room for
such differences of soil and climate as, in a given year, to present in
one State all the conditions favorable to the increase of a particular
insect, while in another, the natural influences are hostile to it. The
only apparent remedy for this evil is, to balance the disproportionate
development of noxious foreign species by bringing from their native
country the tribes which prey upon them. This, it seems, has been
attempted. The United States' Census Report for 1860, p. 82, states that
the New York Agricultural Society "has introduced into this country from
abroad certain parasites which Providence has created to counteract the
destructive powers of some of these depredators."
This is, however, not the only purpose for which man has designedly
introduced foreign forms of insect life. The eggs of the silkworm are
known to have been brought from the farther East to Europe in the sixth
century, and new silk spinners which feed on the castor oil bean and the
ailanthus, have recently been reared in France and in South America with
promising success. The cochineal, long regularly bred in aboriginal
America, has been transplanted to Spain, and both the kermes insect and
the cantharides have been transferred to other climates than their own.
The honey bee must be ranked next to the silkworm in economical
importance.[89] This useful creature was carried to the United States
by European colonists, in the latter part of the seventeenth century; it
did not cross the Mississippi till the close of the eighteenth, and it
is only within the last five or six years that it has been transported
to California, where it was previously unknown. The Italian stingless
bee has very lately been introduced into the United States.
The insects and worms intentionally transplanted by man bear but a small
proportion to those accidentally introduced by him. Plants and animals
often carry their parasites with them, and the traffic of commercial
countries, which exchange their products with every zone and every stage
of social existence, cannot fail to transfer in both directions the
minute organisms that are, in one way or another, associated with almost
every object important to the material interests of man.[90]
The tenacity of life possessed by many insects, their prodigious
fecundity, the length of time they often remain in the different phases
of their existence,[91] the security of the retreats into which their
small dimensions enable them to retire, are all circumstances very
favorable not only to the perpetuity of their species, but to their
transportation to distant climates and their multiplication in their new
homes. The teredo, so destructive to shipping, has been carried by the
vessels whose wooden walls it mines to almost every part of the globe.
The termite, or white ant, is said to have been brought to Rochefort by
the commerce of that port a hundred years ago.[92] This creature is more
injurious to wooden structures and implements than any other known
insect. It eats out almost the entire substance of the wood, leaving
only thin partitions between the galleries it excavates in it; but as it
never gnaws through the surface to the air, a stick of timber may be
almost wholly consumed without showing any external sign of the damage
it has sustained. The termite is found also in other parts of France,
and particularly at Rochelle, where, thus far, its ravages are confined
to a single quarter of the city. A borer, of similar habits, is not
uncommon in Italy, and you may see in that country, handsome chairs and
other furniture which have been reduced by this insect to a framework of
powder of post, covered, and apparently held together, by nothing but
the varnish.
The carnivorous, and often the herbivorous insects render an important
service to man by consuming dead and decaying animal and vegetable
matter, the decomposition of which would otherwise fill the air with
effluvia noxious to health. Some of them, the grave-digger beetle, for
instance, bury the small animals in which they lay their eggs, and
thereby prevent the escape of the gases disengaged by putrefaction. The
prodigious rapidity of development in insect life, the great numbers of
the individuals in many species, and the voracity of most of them while
in the larva state, justify the appellation of nature's scavengers which
has been bestowed upon them, and there is very little doubt that, in
warm countries, they consume a much larger quantity of putrescent
organic material than the quadrupeds and the birds which feed upon such
aliment.
_Destruction of Insects._
It is well known to naturalists, but less familiarly to common
observers, that the aquatic larvæ of some insects constitute, at certain
seasons, a large part of the food of fresh-water fish, while other
larvæ, in their turn, prey upon the spawn and even the young of their
persecutors.[93] The larvæ of the mosquito and the gnat are the favorite
food of the trout in the wooded regions where those insects abound.[94]
Earlier in the year the trout feeds on the larvæ of the May fly, which
is itself very destructive to the spawn of the salmon, and hence, by a
sort of house-that-Jack-built, the destruction of the mosquito, that
feeds the trout that preys on the May fly that destroys the eggs that
hatch the salmon that pampers the epicure, may occasion a scarcity of
this latter fish in waters where he would otherwise be abundant. Thus
all nature is linked together by invisible bonds, and every organic
creature, however low, however feeble, however dependent, is necessary
to the well-being of some other among the myriad forms of life with
which the Creator has peopled the earth.
I have said that man has promoted the increase of the insect and the
worm, by destroying the bird and the fish which feed upon them. Many
insects, in the four different stages of their growth, inhabit in
succession the earth, the water, and the air. In each of these elements
they have their special enemies, and, deep and dark as are the minute
recesses in which they hide themselves, they are pursued to the
remotest, obscurest corners by the executioners that nature has
appointed to punish their delinquencies, and furnished with cunning
contrivances for ferreting out the offenders and dragging them into the
light of day. One tribe of birds, the woodpeckers, seems to depend for
subsistence almost wholly on those insects which breed in dead or dying
trees, and it is, perhaps, needless to say that the injury these birds
do the forest is imaginary. They do not cut holes in the trunk of the
tree to prepare a lodgment for a future colony of boring larvæ, but to
extract the worm which has already begun his mining labors. Hence these
birds are not found where the forester removes trees as fast as they
become fit habitations for such insects. In clearing new lands in the
United States, dead trees, especially of the spike-leaved kinds, too
much decayed to serve for timber, and which, in that state, are worth
little for fuel, are often allowed to stand until they fall of
themselves. Such _stubs_, as they are popularly called, are filled with
borers, and often deeply cut by the woodpeckers, whose strong bills
enable them to penetrate to the very heart of the tree and drag out the
lurking larvæ. After a few years, the stubs fall, or, as wood becomes
valuable, are cut and carried off for firewood, and, at the same time,
the farmer selects for felling, in the forest he has reserved as a
permanent source of supply of fuel and timber, the decaying trees which,
like the dead stems in the fields, serve as a home for both the worm and
his pursuer. We thus gradually extirpate this tribe of insects, and,
with them, the species of birds which subsist principally upon them.
Thus the fine, large, red-headed woodpecker, _Picus erythrocephalus_,
formerly very common in New England, has almost entirely disappeared
from those States, since the dead trees are gone, and the apples, his
favorite vegetable food, are less abundant.
There are even large quadrupeds which feed almost exclusively upon
insects. The ant bear is strong enough to pull down the clay houses
built by the species of termites that constitute his ordinary diet, and
the curious ai-ai, a climbing quadruped of Madagascar--of which I
believe only a single specimen, secured by Mr. Sandwith, has yet reached
Europe--is provided with a very slender, hook-nailed finger, long enough
to reach far into a hole in the trunk of a tree, and extract the worm
which bored it.
_Reptiles._
But perhaps the most formidable foes of the insect, and even of the
small rodents, are the reptiles. The chameleon approaches the insect
perched upon the twig of a tree, with an almost imperceptible slowness
of motion, until, at the distance of a foot, he shoots out his long,
slimy tongue, and rarely fails to secure the victim. Even the slow toad
catches the swift and wary housefly in the same manner; and in the warm
countries of Europe, the numerous lizards contribute very essentially to
the reduction of the insect population, which they both surprise in the
winged state upon walls and trees, and consume as egg, worm, and
chrysalis, in their earlier metamorphoses. The serpents feed much upon
insects, as well as upon mice, moles, and small reptiles, including also
other snakes. The disgust and fear with which the serpent is so
universally regarded expose him to constant persecution by man, and
perhaps no other animal is so relentlessly sacrificed by him. In
temperate climates, snakes are consumed by scarcely any beast or bird of
prey except the stork, and they have few dangerous enemies but man,
though in the tropics other animals prey upon them.[95] It is doubtful
whether any species of serpent has been exterminated within the human
period, and even the dense population of China has not been able
completely to rid itself of the viper. They have, however, almost
entirely disappeared from particular localities. The rattlesnake is now
wholly unknown in many large districts where it was extremely common
half a century ago, and Palestine has long been, if not absolutely free
from venomous serpents, at least very nearly so.[96]
_Destruction of Fish._
The inhabitants of the waters seem comparatively secure from human
pursuit or interference by the inaccessibility of their retreats, and by
our ignorance of their habits--a natural result of the difficulty of
observing the ways of creatures living in a medium in which we cannot
exist. Human agency has, nevertheless, both directly and incidentally,
produced great changes in the population of the sea, the lakes, and the
rivers, and if the effects of such revolutions in aquatic life are
apparently of small importance in general geography, they are still not
wholly inappreciable. The great diminution in the abundance of the
larger fish employed for food or pursued for products useful in the arts
is familiar, and when we consider how the vegetable and animal life on
which they feed must be affected by the reduction of their numbers, it
is easy to see that their destruction may involve considerable
modifications in many of the material arrangements of nature. The whale
does not appear to have been an object of pursuit by the ancients, for
any purpose, nor do we know when the whale fishery first commenced.[97]
It was, however, very actively prosecuted in the Middle Ages, and the
Biscayans seem to have been particularly successful in this as indeed in
other branches of nautical industry.[98] Five hundred years ago, whales
abounded in every sea. They long since became so rare in the
Mediterranean as not to afford encouragement for the fishery as a
regular occupation; and the great demand for oil and whalebone for
mechanical and manufacturing purposes, in the present century, has
stimulated the pursuit of the "hugest of living creatures" to such
activity, that he has now almost wholly disappeared from many favorite
fishing grounds, and in others is greatly diminished in numbers.
What special functions, besides his uses to man, are assigned to the
whale in the economy of nature, we do not know; but some considerations,
suggested by the character of the food upon which certain species
subsist, deserve to be specially noticed. None of the great mammals
grouped under the general name of whale are rapacious. They all live
upon small organisms, and the most numerous species feed almost wholly
upon the soft gelatinous mollusks in which the sea abounds in all
latitudes. We cannot calculate even approximately the number of the
whales, or the quantity of organic nutriment consumed by an individual,
and of course we can form no estimate of the total amount of animal
matter withdrawn by them, in a given period, from the waters of the sea.
It is certain, however, that it must have been enormous when they were
more abundant, and that it is still very considerable. A very few years
since, the United States had more than six hundred whaling ships
constantly employed in the Pacific, and the product of the American
whale fishery for the year ending June 1st, 1860, was seven millions and
a half of dollars.[99] The mere bulk of the whales destroyed in a single
year by the American and the European vessels engaged in this fishery
would form an island of no inconsiderable dimensions, and each one of
those taken must have consumed, in the course of his growth, many times
his own weight of mollusks. The destruction of the whales must have been
followed by a proportional increase of the organisms they feed upon, and
if we had the means of comparing the statistics of these humble forms of
life, for even so short a period as that between the years 1760 and
1860, we should find a difference sufficient, possibly, to suggest an
explanation of some phenomena at present unaccounted for.
For instance, as I have observed in another work,[100] the
phosphorescence of the sea was unknown to ancient writers, or at least
scarcely noticed by them, and even Homer--who, blind as tradition makes
him when he composed his epics, had seen, and marked, in earlier life,
all that the glorious nature of the Mediterranean and its coasts
discloses to unscientific observation--nowhere alludes to this most
beautiful and striking of maritime wonders. In the passage just referred
to, I have endeavored to explain the silence of ancient writers with
respect to this as well as other remarkable phenomena on psychological
grounds; but is it not possible that, in modern times, the animalculæ
which produce it may have immensely multiplied, from the destruction of
their natural enemies by man, and hence that the gleam shot forth by
their decomposition, or by their living processes, is both more frequent
and more brilliant than in the days of classic antiquity?
Although the whale does not prey upon smaller creatures resembling
himself in form and habits, yet true fishes are extremely voracious, and
almost every tribe devours unsparingly the feebler species, and even
the spawn and young of its own. The enormous destruction of the pike,
the trout family, and other ravenous fish, as well as of the fishing
birds, the seal, and the otter, by man, would naturally have occasioned
a great increase in the weaker and more defenceless fish on which they
feed, had he not been as hostile to them also as to their persecutors.
We have little evidence that any fish employed as human food has
naturally multiplied in modern times, while all the more valuable tribes
have been immensely reduced in numbers.[101] This reduction must have
affected the more voracious species not used as food by man, and
accordingly the shark, and other fish of similar habits, though not
objects of systematic pursuit, are now comparatively rare in many waters
where they formerly abounded. The result is, that man has greatly
reduced the numbers of all larger marine animals, and consequently
indirectly favored the multiplication of the smaller aquatic organisms
which entered into their nutriment. This change in the relations of the
organic and inorganic matter of the sea must have exercised an influence
on the latter. What that influence has been, we cannot say, still less
can we predict what it will be hereafter; but its action is not for that
reason the less certain.
_Introduction and Breeding of Fish._
The introduction and successful breeding of fish of foreign species
appears to have been long practised in China and was not unknown to the
Greeks and Romans. This art has been revived in modern times, but thus
far without any important results, economical or physical, though there
seems to be good reason to believe it may be employed with advantage on
an extended scale. As in the case of plants, man has sometimes
undesignedly introduced new species of aquatic animals into countries
distant from their birthplace. The accidental escape of the Chinese
goldfish from ponds where they were bred as a garden ornament, has
peopled some European, and it is said American streams with this
species. Canals of navigation and irrigation interchange the fish of
lakes and rivers widely separated by natural barriers, as well as the
plants which drop their seeds into the waters. The Erie Canal, as
measured by its own channel, has a length of about three hundred and
sixty miles, and it has ascending and descending locks in both
directions. By this route, the fresh-water fish of the Hudson and the
Upper Lakes, and some of the indigenous vegetables of these respective
basins, have intermixed, and the fauna and flora of the two regions have
now more species common to both than before the canal was opened. Some
accidental attraction not unfrequently induces fish to follow a vessel
for days in succession, and they may thus be enticed into zones very
distant from their native habitat. Several years ago, I was told at
Constantinople, upon good authority, that a couple of fish, of a species
wholly unknown to the natives, had just been taken in the Bosphorus.
They were alleged to have followed an English ship from the Thames, and
to have been frequently observed by the crew during the passage, but I
was unable to learn their specific character.
Many of the fish which pass the greater part of the year in salt water
spawn in fresh, and some fresh-water species, the common brook trout of
New England for instance, which, under ordinary circumstances, never
visit the sea, will, if transferred to brooks emptying directly into the
ocean, go down into the salt water after spawning time, and return again
the next season. Sea fish, the smelt among others, are said to have been
naturalized in fresh water, and some naturalists have argued from the
character of the fish of Lake Baikal, and especially from the existence
of the seal in that locality, that all its inhabitants were originally
marine species, and have changed their habits with the gradual
conversion of the saline waters of the lake--once, as is assumed, a
maritime bay--into fresh.[102] The presence of the seal is hardly
conclusive on this point, for it is sometimes seen in Lake Champlain at
the distance of some hundreds of miles from even brackish water. One of
these animals was killed on the ice in that lake in February, 1810,
another in February, 1846,[103] and remains of the seal have been found
at other times in the same waters.
The remains of the higher orders of aquatic animals are generally so
perishable that, even where most abundant, they do not appear to be now
forming permanent deposits of any considerable magnitude; but it is
quite otherwise with shell fish, and, as we shall see hereafter, with
many of the minute limeworkers of the sea. There are, on the southern
coast of the United States, beds of shells so extensive that they were
formerly supposed to have been naturally accumulated, and were appealed
to as proofs of an elevation of the coast by geological causes; but they
are now ascertained to have been derived from oysters, consumed in the
course of long ages by the inhabitants of Indian towns. The planting of
a bed of oysters in a new locality might, very probably, lead, in time,
to the formation of a bank, which, in connection with other deposits,
might perceptibly affect the line of a coast, or, by changing the course
of marine currents, or the outlet of a river, produce geographical
changes of no small importance. The transplantation of oysters to
artificial ponds has long been common, and it appears to have recently
succeeded well on a large scale in the open sea on the French coast. A
great extension of this fishery is hoped for, and it is now proposed to
introduce upon the same coast the American soft clam, which is so
abundant in the tide-washed beach sands of Long Island Sound as to form
an important article in the diet of the neighboring population.
The intentional naturalization of foreign fish, as I have said, has not
thus far yielded important fruits; but though this particular branch of
what is called, not very happily, _pisciculture_, has not yet
established its claims to the attention of the physical geographer or
the political economist, the artificial breeding of domestic fish has
already produced very valuable results, and is apparently destined to
occupy an extremely conspicuous place in the history of man's efforts to
compensate his prodigal waste of the gifts of nature. The restoration of
the primitive abundance of salt and fresh water fish, is one of the
greatest material benefits that, with our present physical resources,
governments can hope to confer upon their subjects. The rivers, lakes,
and seacoasts once restocked, and protected by law from exhaustion by
taking fish at improper seasons, by destructive methods, and in
extravagant quantities, would continue indefinitely to furnish a very
large supply of most healthful food, which, unlike all domestic and
agricultural products, would spontaneously renew itself and cost nothing
but the taking. There are many sterile or wornout soils in Europe so
situated that they might, at no very formidable cost, be converted into
permanent lakes, which would serve not only as reservoirs to retain the
water of winter rains and snow, and give it out in the dry season for
irrigation, but as breeding ponds for fish, and would thus, without
further cost, yield a larger supply of human food than can at present be
obtained from them even at a great expenditure of capital and labor in
agricultural operations. The additions which might be made to the
nutriment of the civilized world by a judicious administration of the
resources of the waters, would allow some restriction of the amount of
soil at present employed for agricultural purposes, and a corresponding
extension of the area of the forest, and would thus facilitate a return
to primitive geographical arrangements which it is important partially
to restore.
_Extirpation of Aquatic Animals._
It does not seem probable that man, with all his rapacity and all his
enginery, will succeed in totally extirpating any salt-water fish, but
he has already exterminated at least one marine warm-blooded
animal--Steller's sea cow--and the walrus, the sea lion, and other large
amphibia, as well as the principal fishing quadrupeds, are in imminent
danger of extinction. Steller's sea cow, _Rhytina Stelleri_, was first
seen by Europeans in the year 1741, on Bering's Island. It was a huge
amphibious mammal, weighing not less than eight thousand pounds, and
appears to have been confined exclusively to the islands and coasts in
the neighborhood of Bering's Strait. Its flesh was very palatable, and
the localities it frequented were easily accessible from the Russian
establishments in Kamtschatka. As soon as its existence and character,
and the abundance of fur animals in the same waters, were made known to
the occupants of those posts by the return of the survivors of Bering's
expedition, so active a chase was commenced against the amphibia of that
region, that, in the course of twenty-seven years, the sea cow,
described by Steller as extremely numerous in 1741, is believed to have
been completely extirpated, not a single individual having been seen
since the year 1768. The various tribes of seals in the Northern and
Southern Pacific, the walrus and the sea otter, are already so reduced
in numbers that they seem destined soon to follow the sea cow, unless
protected by legislation stringent enough, and a police energetic
enough, to repress the ardent cupidity of their pursuers.
The seals, the otter tribe, and many other amphibia which feed almost
exclusively upon fish, are extremely voracious, and of course their
destruction or numerical reduction must have favored the multiplication
of the species of fish principally preyed upon by them. I have been
assured by the keeper of several tamed seals that, if supplied at
frequent intervals, each seal would devour not less than fourteen pounds
of fish, or about a quarter of his own weight, in a day.[104] A very
intelligent and observing hunter, who has passed a great part of his
life in the forest, after carefully watching the habits of the
fresh-water otter of the Northern American States, estimates their
consumption of fish at about four pounds per day.
Man has promoted the multiplication of fish by making war on their brute
enemies, but he has by no means thereby compensated his own greater
destructiveness.[105] The bird and beast of prey, whether on land or in
the water, hunt only as long as they feel the stimulus of hunger, their
ravages are limited by the demands of present appetite, and they do not
wastefully destroy what they cannot consume. Man, on the contrary,
angles to-day that he may dine to-morrow; he takes and dries millions of
fish on the banks of Newfoundland, that the fervent Catholic of the
shores of the Mediterranean may have wherewithal to satisfy the cravings
of the stomach during next year's Lent, without imperilling his soul by
violating the discipline of the papal church; and all the arrangements
of his fisheries are so organized as to involve the destruction of many
more fish than are secured for human use, and the loss of a large
proportion of the annual harvest of the sea in the process of curing, or
in transportation to the places of its consumption.[106]
Fish are more affected than quadrupeds by slight and even imperceptible
differences in their breeding places and feeding grounds. Every river,
every brook, every lake stamps a special character upon its salmon, its
shad, and its trout, which is at once recognized by those who deal in or
consume them. No skill can give the fish fattened by food selected and
prepared by man the flavor of those which are nourished at the table of
nature, and the trout of the artificial ponds in Germany and Switzerland
are so inferior to the brook fish of the same species and climate, that
it is hard to believe them identical. The superior sapidity of the
American trout to the European species, which is familiar to every one
acquainted with both continents, is probably due less to specific
difference than to the fact that, even in the parts of the New World
which have been longest cultivated, wild nature is not yet tamed down to
the character it has assumed in the Old, and which it will acquire in
America also when her civilization shall be as ancient as is now that of
Europe.
Man has hitherto hardly anywhere produced such climatic or other changes
as would suffice of themselves totally to banish the wild inhabitants of
the dry land, and the disappearance of the native birds and quadrupeds
from particular localities is to be ascribed quite as much to his direct
persecutions as to the want of forest shelter, of appropriate food, or
of other conditions indispensable to their existence. But almost all the
processes of agriculture, and of mechanical and chemical industry, are
fatally destructive to aquatic animals within reach of their influence.
When, in consequence of clearing the woods, the changes already
described as thereby produced in the beds and currents of rivers, are in
progress, the spawning grounds of fish are exposed from year to year to
a succession of mechanical disturbances; the temperature of the water is
higher in summer, colder in winter, than when it was shaded and
protected by wood; the smaller organisms, which formed the sustenance of
the young fry, disappear or are reduced in numbers, and new enemies are
added to the old foes that preyed upon them; the increased turbidness of
the water in the annual inundations chokes the fish; and, finally, the
quickened velocity of its current sweeps them down into the larger
rivers or into the sea, before they are yet strong enough to support so
great a change of circumstances.[107] Industrial operations are not
less destructive to fish which live or spawn in fresh water. Milldams
impede their migrations, if they do not absolutely prevent them, the
sawdust from lumber mills clogs their gills, and the thousand
deleterious mineral substances, discharged into rivers from
metallurgical, chemical, and manufacturing establishments, poison them
by shoals.
_Minute Organisms._
Besides the larger creatures of the land and of the sea, the quadrupeds,
the reptiles, the birds, the amphibia, the crustacea, the fish, the
insects, and the worms, there are other countless forms of vital being.
Earth, water, the ducts and fluids of vegetable and of animal life, the
very air we breathe, are peopled by minute organisms which perform most
important functions in both the living and the inanimate kingdoms of
nature. Of the offices assigned to these creatures, the most familiar to
common observation is the extraction of lime, and more rarely, of silex,
from the waters inhabited by them, and the deposit of these minerals in
a solid form, either as the material of their habitations or as the
exuviæ of their bodies. The microscope and other means of scientific
observation assure us that the chalk beds of England and of France, the
coral reefs of marine waters in warm climates, vast calcareous and
silicious deposits in the sea and in many fresh-water ponds, the common
polishing earths and slates, and many species of apparently dense and
solid rock, are the work of the humble organisms of which I speak,
often, indeed, of animalculæ so small as to become visible only by the
aid of lenses magnifying a hundred times the linear measures. It is
popularly supposed that animalculæ, or what are commonly embraced under
the vague name of infusoria, inhabit the water alone, but the
atmospheric dust transported by every wind and deposited by every calm
is full of microscopic life or of its relics. The soil on which the city
of Berlin stands, contains at the depth of ten or fifteen feet below the
surface, living elaborators of silex;[108] and a microscopic examination
of a handful of earth connected with the material evidences of guilt has
enabled the naturalist to point out the very spot where a crime was
committed. It has been computed that one sixth part of the solid matter
let fall by great rivers at their outlets consists of still recognizable
infusory shells and shields, and, as the friction of rolling water must
reduce much of these fragile structures to a state of comminution which
even the microscope cannot resolve into distinct particles and identify
as relics of animal or of vegetable life, we must conclude that a
considerably larger proportion of river deposits is really the product
of animalcules.[109]
It is evident that the chemical, and in many cases the mechanical
character of a great number of the objects important in the material
economy of human life, must be affected by the presence of so large an
organic element in their substance, and it is equally obvious that all
agricultural and all industrial operations tend to disturb the natural
arrangements of this element, to increase or to diminish the special
adaptation of every medium in which it lives to the particular orders
of being inhabited by it. The conversion of woodland into pasturage, of
pasture into plough land, of swamp or of shallow sea into dry ground,
the rotations of cultivated crops, must prove fatal to millions of
living things upon every rood of surface thus deranged by man, and must,
at the same time, more or less fully compensate this destruction of life
by promoting the growth and multiplication of other tribes equally
minute in dimensions.
I do not know that man has yet endeavored to avail himself, by
artificial contrivances, of the agency of these wonderful architects and
manufacturers. We are hardly well enough acquainted with their natural
economy to devise means to turn their industry to profitable account,
and they are in very many cases too slow in producing visible results
for an age so impatient as ours. The over-civilization of the nineteenth
century cannot wait for wealth to be amassed by infinitesimal gains, and
we are in haste to _speculate_ upon the powers of nature, as we do upon
objects of bargain and sale in our trafficking one with another. But
there are still some cases where the little we know of a life, whose
workings are invisible to the naked eye, suggests the possibility of
advantageously directing the efforts of troops of artisans that we
cannot see. Upon coasts occupied by the corallines, the reef-building
animalcule does not work near the mouth of rivers. Hence the change of
the outlet of a stream, often a very easy matter, may promote the
construction of a barrier to coast navigation at one point, and check
the formation of a reef at another, by diverting a current of fresh
water from the former and pouring it into the sea at the latter. Cases
may probably be found in tropical seas, where rivers have prevented the
working of the coral animalcules in straits separating islands from each
other or from the mainland. The diversion of such streams might remove
this obstacle, and reefs consequently be formed which should convert an
archipelago into a single large island, and finally join that to the
neighboring continent.
Quatrefages proposed to destroy the teredo in harbors by impregnating
the water with a mineral solution fatal to them. Perhaps the labors of
the coralline animals might be arrested over a considerable extent of
sea coast by similar means. The reef builders are leisurely architects,
but the precious coral is formed so rapidly that the beds may be
refished advantageously as often as once in ten years.[110] It does not
seem impossible that this coral might be transplanted to the American
coast, where the Gulf stream would furnish a suitable temperature beyond
the climatic limits that otherwise confine its growth; and thus a new
source of profit might perhaps be added to the scanty returns of the
hardy fisherman.
In certain geological formations, the diatomaceæ deposit, at the bottom
of fresh-water ponds, beds of silicious shields, valuable as a material
for a species of very light firebrick, in the manufacture of water glass
and of hydraulic cement, and ultimately, doubtless, in many yet
undiscovered industrial processes. An attentive study of the conditions
favorable to the propagation of the diatomaceæ might perhaps help us to
profit directly by the productivity of this organism, and, at the same
time, disclose secrets of nature capable of being turned to valuable
account in dealing with silicious rocks, and the metal which is the base
of them. Our acquaintance with the obscure and infinitesimal life of
which I have now been treating is very recent, and still very imperfect.
We know that it is of vast importance in the economy of nature, but we
are so ambitious to grasp the great, so little accustomed to occupy
ourselves with the minute, that we are not yet prepared to enter
seriously upon the question how far we can control and direct the
operations, not of unembodied physical forces, but of beings, in popular
apprehension, almost as immaterial as they.
Nature has no unit of magnitude by which she measures her works. Man
takes his standards of dimension from himself. The hair's breadth was
his minimum until the microscope told him that there are animated
creatures to which one of the hairs of his head is a larger cylinder
than is the trunk of the giant California redwood to him. He borrows his
inch from the breadth of his thumb, his palm and span from the width of
his hand and the spread of his fingers, his foot from the length of the
organ so named; his cubit is the distance from the tip of his middle
finger to his elbow, and his fathom is the space he can measure with his
outstretched arms. To a being who instinctively finds the standard of
all magnitudes in his own material frame, all objects exceeding his own
dimensions are absolutely great, all falling short of them absolutely
small. Hence we habitually regard the whale and the elephant as
essentially large and therefore important creatures, the animalcule as
an essentially small and therefore unimportant organism. But no
geological formation owes its origin to the labors or the remains of the
huge mammal, while the animalcule composes, or has furnished, the
substance of strata thousands of feet in thickness, and extending, in
unbroken beds, over many degrees of terrestrial surface. If man is
destined to inhabit the earth much longer, and to advance in natural
knowledge with the rapidity which has marked his progress in physical
science for the last two or three centuries, he will learn to put a
wiser estimate on the works of creation, and will derive not only great
instruction from studying the ways of nature in her obscurest, humblest
walks, but great material advantage from stimulating her productive
energies in provinces of her empire hitherto regarded as forever
inaccessible, utterly barren.[111]
CHAPTER III.
THE WOODS.
THE HABITABLE EARTH ORIGINALLY WOODED--THE FOREST DOES NOT FURNISH
FOOD FOR MAN--FIRST REMOVAL OF THE WOODS--EFFECTS OF FIRE ON FOREST
SOIL--EFFECTS OF THE DESTRUCTION OF THE FOREST--ELECTRICAL INFLUENCE
OF TREES--CHEMICAL INFLUENCE OF THE FOREST.
INFLUENCE OF THE FOREST, CONSIDERED AS INORGANIC MATTER, ON TEMPERATURE:
_a_, ABSORBING AND EMITTING SURFACE; _b_, TREES AS CONDUCTORS OF HEAT;
_c_, TREES IN SUMMER AND IN WINTER; _d_, DEAD PRODUCTS OF TREES; _e_,
TREES AS A SHELTER TO GROUNDS TO THE LEEWARD OF THEM; _f_, TREES AS A
PROTECTION AGAINST MALARIA--THE FOREST, AS INORGANIC MATTER, TENDS TO
MITIGATE EXTREMES.
TREES AS ORGANISMS: SPECIFIC TEMPERATURE--TOTAL INFLUENCE OF THE FOREST
ON TEMPERATURE.
INFLUENCE OF FORESTS ON THE HUMIDITY OF THE AIR AND THE EARTH:
_a_, AS INORGANIC MATTER; _b_, AS ORGANIC--WOOD MOSSES AND FUNGI--
FLOW OF SAP--ABSORPTION AND EXHALATION OF MOISTURE BY TREES--BALANCE
OF CONFLICTING INFLUENCES--INFLUENCE OF THE FOREST ON TEMPERATURE AND
PRECIPITATION--INFLUENCE OF THE FOREST ON THE HUMIDITY OF THE SOIL--
ITS INFLUENCE ON THE FLOW OF SPRINGS--GENERAL CONSEQUENCES OF THE
DESTRUCTION OF THE WOODS--LITERATURE AND CONDITION OF THE FOREST IN
DIFFERENT COUNTRIES--THE INFLUENCE OF THE FOREST ON INUNDATIONS--
DESTRUCTIVE ACTION OF TORRENTS--THE PO AND ITS DEPOSITS--MOUNTAIN
SLIDES--PROTECTION AGAINST THE FALL OF ROCKS AND AVALANCHES BY
TREES--PRINCIPAL CAUSES OF THE DESTRUCTION OF THE FOREST--AMERICAN
FOREST TREES--SPECIAL CAUSES OF THE DESTRUCTION OF EUROPEAN WOODS--
ROYAL FORESTS AND GAME LAWS--SMALL FOREST PLANTS, VITALITY OF SEEDS--
UTILITY OF THE FOREST--THE FORESTS OF EUROPE--FORESTS OF THE UNITED
STATES AND CANADA--THE ECONOMY OF THE FOREST--EUROPEAN AND AMERICAN
TREES COMPARED--SYLVICULTURE--INSTABILITY OF AMERICAN LIFE.
_The Habitable Earth Originally Wooded._
There is good reason to believe that the surface of the habitable earth,
in all the climates and regions which have been the abodes of dense and
civilized populations, was, with few exceptions, already covered with a
forest growth when it first became the home of man. This we infer from
the extensive vegetable remains--trunks, branches, roots, fruits, seeds,
and leaves of trees--so often found in conjunction with works of
primitive art, in the boggy soil of districts where no forests appear to
have existed within the eras through which written annals reach; from
ancient historical records, which prove that large provinces, where the
earth has long been wholly bare of trees, were clothed with vast and
almost unbroken woods when first made known to Greek and Roman
civilization;[112] and from the state of much of North and of South
America when they were discovered and colonized by the European
race.[113]
These evidences are strengthened by observation of the natural economy
of our own time; for, whenever a tract of country, once inhabited and
cultivated by man, is abandoned by him and by domestic animals,[114] and
surrendered to the undisturbed influences of spontaneous nature, its
soil sooner or later clothes itself with herbaceous and arborescent
plants, and at no long interval, with a dense forest growth. Indeed,
upon surfaces of a certain stability, and not absolutely precipitous
inclination, the special conditions required for the spontaneous
propagation of trees may all be negatively expressed and reduced to
these three: exemption from defect or excess of moisture, from perpetual
frost, and from the depredations of man and browsing quadrupeds. Where
these requisites are secured, the hardest rock is as certain to be
overgrown with wood as the most fertile plain, though, for obvious
reasons, the process is slower in the former than in the latter case.
Lichens and mosses first prepare the way for a more highly organized
vegetation. They retain the moisture of rains and dews, and bring it to
act, in combination with the gases evolved by their organic processes,
in decomposing the surface of the rocks they cover; they arrest and
confine the dust which the wind scatters over them, and their final
decay adds new material to the soil already half formed beneath and upon
them. A very thin stratum of mould is sufficient for the germination of
seeds of the hardy evergreens and birches, the roots of which are often
found in immediate contact with the rock, supplying their trees with
nourishment from a soil derived from the decomposition of their own
foliage, or sending out long rootlets into the surrounding earth in
search of juices to feed them.
The eruptive matter of volcanoes, forbidding as is its aspect, does not
refuse nutriment to the woods. The refractory lava of Etna, it is true,
remains long barren, and that of the great eruption of 1669 is still
almost wholly devoid of vegetation.[115] But the cactus is making
inroads even here, while the volcanic sand and molten rock thrown out by
Vesuvius soon becomes productive. George Sandys, who visited this
latter mountain in 1611, after it had reposed for several centuries,
found the throat of the volcano at the bottom of the crater "almost
choked with broken rocks and _trees_ that are falne therein." "Next to
this," he continues, "the matter thrown up is ruddy, light, and soft:
more removed, blacke and ponderous: the uttermost brow, that declineth
like the seates in a theater, flourishing with trees and excellent
pasturage. The midst of the hill is shaded with chestnut trees, and
others bearing sundry fruits."[116]
I am convinced that forests would soon cover many parts of the Arabian
and African deserts, if man and domestic animals, especially the goat
and the camel, were banished from them. The hard palate and tongue and
strong teeth and jaws of this latter quadruped enable him to break off
and masticate tough and thorny branches as large as the finger. He is
particularly fond of the smaller twigs, leaves, and seedpods of the
_sont_ and other acacias, which, like the American Robinia, thrive well
on dry and sandy soils, and he spares no tree the branches of which are
within his reach, except, if I remember right, the tamarisk that
produces manna. Young trees sprout plentifully around the springs and
along the winter watercourses of the desert, and these are just the
halting stations of the caravans and their routes of travel. In the
shade of these trees, annual grasses and perennial shrubs shoot up, but
are mown down by the hungry cattle of the Bedouin, as fast as they grow.
A few years of undisturbed vegetation would suffice to cover such points
with groves, and these would gradually extend themselves over soils
where now scarcely any green thing but the bitter colocynth and the
poisonous foxglove is ever seen.
_The Forest does not Furnish Food for Man._
In a region absolutely covered with trees, human life could not long be
sustained, for want of animal and vegetable food. The depths of the
forest seldom furnish either bulb or fruit suited to the nourishment of
man; and the fowls and beasts on which he feeds are scarcely seen except
upon the margin of the wood, for here only grow the shrubs and grasses,
and here only are found the seeds and insects, which form the sustenance
of the non-carnivorous birds and quadrupeds.[117]
_First Removal of the Forest._
As soon as multiplying man had filled the open grounds along the margin
of the rivers, the lakes, and the sea, and sufficiently peopled the
natural meadows and savannas of the interior, where such existed,[118]
he could find room for expansion and further growth, only by the
removal of a portion of the forest that hemmed him in. The destruction
of the woods, then, was man's first geographical conquest, his first
violation of the harmonies of inanimate nature.
Primitive man had little occasion to fell trees for fuel, or, for the
construction of dwellings, boats, and the implements of his rude
agriculture and handicrafts. Windfalls would furnish a thin population
with a sufficient supply of such material, and if occasionally a growing
tree was cut, the injury to the forest would be too insignificant to be
at all appreciable.
The accidental escape and spread of fire, or, possibly, the combustion
of forests by lightning, must have first suggested the advantages to be
derived from the removal of too abundant and extensive woods, and, at
the same time, have pointed out a means by which a large tract of
surface could readily be cleared of much of this natural incumbrance. As
soon as agriculture had commenced at all, it would be observed that the
growth of cultivated plants, as well as of many species of wild
vegetation, was particularly rapid and luxuriant on soils which had been
burned over, and thus a new stimulus would be given to the practice of
destroying the woods by fire, as a means of both extending the open
grounds, and making the acquisition of a yet more productive soil. After
a few harvests had exhausted the first rank fertility of the virgin
mould, or when weeds and briers and the sprouting roots of the trees had
begun to choke the crops of the half-subdued soil, the ground would be
abandoned for new fields won from the forest by the same means, and the
deserted plain or hillock would soon clothe itself anew with shrubs and
trees, to be again subjected to the same destructive process, and again
surrendered to the restorative powers of vegetable nature.[119] This
rude economy would be continued for generations, and wasteful as it is,
is still largely pursued in Northern Sweden, Swedish Lapland, and
sometimes even in France and the United States.[120]
_Effects of Fire on Forest Soil._
Aside from the mechanical and chemical effects of the disturbance of the
soil by agricultural operations, and of the freer admission of sun,
rain, and air to the ground, the fire of itself exerts an important
influence on its texture and condition. It consumes a portion of the
half-decayed vegetable mould which served to hold its mineral particles
together and to retain the water of precipitation, and thus loosens,
pulverizes, and dries the earth; it destroys reptiles, insects, and
worms, with their eggs, and the seeds of trees and of smaller plants; it
supplies, in the ashes which it deposits on the surface, important
elements for the growth of a new forest clothing, as well as of the
usual objects of agricultural industry; and by the changes thus
produced, it fits the ground for the reception of a vegetation different
in character from that which had spontaneously covered it. These new
conditions help to explain the natural succession of forest crops, so
generally observed in all woods cleared by fire and then abandoned.
There is no doubt, however, that other influences contribute to the same
result, because effects more or less analogous follow when the trees are
destroyed by other causes, as by high winds, by the woodman's axe, and
even by natural decay.[121]
_Effects of Destruction of the Forest._
The physico-geographical effects of the destruction of the forests may
be divided into two great classes, each having an important influence on
vegetable and on animal life in all their manifestations, as well as on
every branch of rural economy and productive industry, and, therefore,
on all the material interests of man. The first respects the meteorology
of the countries exposed to the action of these influences; the second,
their superficial geography, or, in other words, configuration,
consistence, and clothing of surface.
For reasons assigned in the first chapter, the meteorological or
climatic branch of the subject is the most obscure, and the conclusions
of physicists respecting it are, in a great degree, inferential only,
not founded on experiment or direct observation. They are, as might be
expected, somewhat discordant, though certain general results are almost
universally accepted, and seem indeed too well supported to admit of
serious question.
_Electrical Influence of Trees._
The properties of trees, singly and in groups, as exciters or conductors
of electricity, and their consequent influence upon the electrical state
of the atmosphere, do not appear to have been much investigated; and the
conditions of the forest itself are so variable and so complicated, that
the solution of any general problem respecting its electrical influence
would be a matter of extreme difficulty. It is, indeed, impossible to
suppose that a dense cloud, a sea of vapor, can pass over miles of
surface bristling with good conductors, without undergoing some change
of electrical condition. Hypothetical cases may be put in which the
character of the change could be deduced from the known laws of
electrical action. But in actual nature, the elements are too numerous
for us to seize. The true electrical condition of neither cloud nor
forest could be known, and it could seldom be predicted whether the
vapors would be dissolved as they floated over the wood, or discharged
upon it in a deluge of rain. With regard to possible electrical
influences of the forest, wider still in their range of action, the
uncertainty is even greater. The data which alone could lead to certain,
or even probable, conclusions are wanting, and we should, therefore,
only embarrass our argument by any attempt to discuss this
meteorological element, important as it may be, in its relations of
cause and effect to more familiar and better understood meteoric
phenomena. It may, however, be observed that hail storms--which were
once generally supposed, and are still held by many, to be produced by a
specific electrical action, and which, at least, are always accompanied
by electrical disturbances--are believed, in all countries particularly
exposed to that scourge, to have become more frequent and destructive in
proportion as the forests have been cleared. Caimi observes: "When the
chains of the Alps and the Apennines had not yet been stripped of their
magnificent crown of woods, the May hail, which now desolates the
fertile plains of Lombardy, was much less frequent; but since the
general prostration of the forest, these tempests are laying waste even
the mountain soils whose older inhabitants scarcely knew this
plague.[122] The _paragrandini_,[123] which the learned curate of
Rivolta advised to erect, with sheaves of straw set up vertically, over
a great extent of cultivated country, are but a Liliputian image of the
vast paragrandini, pines, larches, firs, which nature had planted by
millions on the crests and ridges of the Alps and the Apennines."[124]
"Electrical action being diminished," says Meguscher, "and the rapid
congelation of vapors by the abstraction of heat being impeded by the
influence of the woods, it is rare that hail or waterspouts are
produced, within the precincts of a large forest when it is assailed by
the tempest."[125] Arthur Young was told that since the forests which
covered the mountains between the Riviera and the county of Montferrat
had disappeared, hail had become more destructive in the district of
Acqui,[126] and it appears upon good authority, that a similar increase
in the frequency and violence of hail storms in the neighborhood of
Saluzzo and Mondovì, the lower part of the Valtelline, and the territory
of Verona and Vicenza, is probably to be ascribed to a similar
cause.[127]
_Chemical Influence of the Forest._
We know that the air in a close apartment is appreciably affected
through the inspiration and expiration of gases by plants growing in it.
The same operations are performed on a gigantic scale by the forest, and
it has even been supposed that the absorption of carbon, by the rank
vegetation of earlier geological periods, occasioned a permanent change
in the constitution of the terrestrial atmosphere.[128] To the effects
thus produced, are to be added those of the ultimate gaseous
decomposition of the vast vegetable mass annually shed by trees, and of
their trunks and branches when they fall a prey to time. But the
quantity of gases thus abstracted from and restored to the atmosphere is
inconsiderable--infinitesimal, one might almost say--in comparison with
the ocean of air from which they are drawn and to which they return; and
though the exhalations from bogs, and other low grounds covered with
decaying vegetable matter, are highly deleterious to human health, yet,
in general, the air of the forest is hardly chemically distinguishable
from that of the sand plains, and we can as little trace the influence
of the woods in the analysis of the atmosphere, as we can prove that the
mineral ingredients of land springs sensibly affect the chemistry of
the sea. I may, then, properly dismiss the chemical, as I have done the
electrical influences of the forest, and treat them both alike, if not
as unimportant agencies, at least as quantities of unknown value in our
meteorological equation.[129] Our inquiries upon this branch of the
subject will accordingly be limited to the thermometrical and
hygrometrical influences of the woods.
_Influence of the Forest, considered as Inorganic Matter, on
Temperature._
The evaporation of fluids, and the condensation and expansion of vapors
and gases, are attended with changes of temperature; and the quantity of
moisture which the air is capable of containing, and, of course, the
evaporation, rise and fall with the thermometer. The hygroscopical and
the thermoscopical conditions of the atmosphere are, therefore,
inseparably connected as reciprocally dependent quantities, and neither
can be fully discussed without taking notice of the other. But the
forest, regarded purely as inorganic matter, and without reference to
its living processes of absorption and exhalation of water and gases,
has, as an absorbent, a radiator and a conductor of heat, and as a mere
covering of the ground, an influence on the temperature of the air and
the earth, which may be considered by itself.
a. _Absorbing and Emitting Surface._
A given area of ground, as estimated by the every-day rule of
measurement in yards or acres, presents always the same apparent
quantity of absorbing, radiating, and reflecting surface; but the real
extent of that surface is very variable, depending, as it does, upon its
configuration, and the bulk and form of the adventitious objects it
bears upon it; and, besides, the true superficies remaining the same,
its power of absorption, radiation, reflection, and conduction of heat
will be much affected by its consistence, its greater or less humidity,
and its color, as well as by its inclination of plane and
exposure.[130] An acre of chalk, rolled hard and smooth, would have
great reflecting power, but its radiation would be much increased by
breaking it up into clods, because the actually exposed surface would be
greater, though the outline of the field remained the same. The area of
a triangle being equal to its base multiplied by half the length of a
perpendicular let fall from its apex, it follows that the entire
superficies of the triangular faces of a quadrangular pyramid, the
perpendicular of whose sides should be twice the length of the base,
would be four times the area of the ground it covered, and would add to
the field on which it stood so much surface capable of receiving and
emitting heat, though, in consequence of obliquity and direction of
plane, its actual absorption and emission of heat might not be so great
as that of an additional quantity of level ground containing four times
the area of its base. The lesser inequalities which always occur in the
surface of ordinary earth affect in the same way its quantity of
superficies acting upon the temperature of the atmosphere, and acted on
by it, though the amount of this action and reaction is not susceptible
of measurement.
Analogous effects are produced by other objects, of whatever form or
character, standing or lying upon the earth, and no solid can be placed
upon a flat piece of ground, without itself exposing a greater surface
than it covers. This applies, of course, to forest trees and their
leaves, and indeed to all vegetables, as well as to other prominent
bodies. If we suppose forty trees to be planted on an acre, one being
situated in the centre of every square of two rods the side, and to grow
until their branches and leaves everywhere meet, it is evident that,
when in full foliage, the trunks, branches, and leaves would present an
amount of thermoscopic surface much greater than that of an acre of bare
earth; and besides this, the fallen leaves lying scattered on the
ground, would somewhat augment the sum total.[131] On the other hand,
the growing leaves of trees generally form a succession of stages, or,
loosely speaking, layers, corresponding to the animal growth of the
branches, and more or less overlying each other. This disposition of the
foliage interferes with that free communication between sun and sky
above, and leaf surface below, on which the amount of radiation and
absorption of heat depends. From all these considerations, it appears
that though the effective thermoscopic surface of a forest in full leaf
does not exceed that of bare ground in the same proportion as does its
measured superficies, yet the actual quantity of area capable of
receiving and emitting heat must be greater in the former than in the
latter case.[132]
It must further be remembered that the form and texture of a given
surface are important elements in determining its thermoscopic
character. Leaves are porous, and admit air and light more or less
freely into their substance; they are generally smooth and even glazed
on one surface; they are usually covered on one or both sides with
spiculæ, and they very commonly present one or more acuminated points in
their outline--all circumstances which tend to augment their power of
emitting heat by reflection or radiation. Direct experiment on growing
trees is very difficult, nor is it in any case practicable to
distinguish how far a reduction of temperature produced by vegetation is
due to radiation, and how far to exhalation of the fluids of the plant
in a gaseous form; for both processes usually go on together. But the
frigorific effect of leafy structure is well observed in the deposit of
dew and the occurrence of hoarfrost on the foliage of grasses and other
small vegetables, and on other objects of similar form and consistence,
when the temperature of the air a few yards above has not been brought
down to the dew point, still less to 32°, the degree of cold required to
congeal dew to frost.[133]
b. _Trees as Conductors of Heat._
We are also to take into account the action of the forest as a conductor
of heat between the atmosphere and the earth. In the most important
countries of America and Europe, and especially in those which have
suffered most from the destruction of the woods, the superficial strata
of the earth are colder in winter, and warmer in summer than those a few
inches lower, and their shifting temperature approximates to the
atmospheric mean of the respective seasons. The roots of large trees
penetrate beneath the superficial strata, and reach earth of a nearly
constant temperature, corresponding to the mean for the entire year. As
conductors, they convey the heat of the atmosphere to the earth when the
earth is colder than the air, and transmit it in the contrary direction
when the temperature of the earth is higher than that of the atmosphere.
Of course, then, as conductors, they tend to equalize the temperature of
the earth and the air.
c. _Trees in Summer and Winter._
In countries where the questions I am considering have the greatest
practical importance, a very large proportion, if not a majority, of the
trees are of deciduous foliage, and their radiating as well as their
shading surface is very much greater in summer than in winter. In the
latter season, they little obstruct the reception of heat by the ground
or the radiation from it; whereas, in the former, they often interpose a
complete canopy between the ground and the sky, and materially
interfere with both processes.
d. _Dead Products of Trees._
Besides this various action of standing trees considered as inorganic
matter, the forest exercises, by the annual moulting of its foliage,
still another influence on the temperature of the earth, and,
consequently, of the atmosphere which rests upon it. If you examine the
constitution of the superficial soil in a primitive or an old and
undisturbed artificially planted wood, you find, first, a deposit of
undecayed leaves, twigs, and seeds, lying in loose layers on the
surface; then, more compact beds of the same materials in incipient,
and, as you descend, more and more advanced stages of decomposition;
then, a mass of black mould, in which traces of organic structure are
hardly discoverable except by microscopic examination; then, a stratum
of mineral soil, more or less mixed with vegetable matter carried down
into it by water, or resulting from the decay of roots; and, finally,
the inorganic earth or rock itself. Without this deposit of the dead
products of trees, this latter would be the superficial stratum, and as
its powers of absorption, radiation, and conduction of heat would differ
essentially from those of the layers with which it has been covered by
the droppings of the forest, it would act upon the temperature of the
atmosphere, and be acted on by it, in a very different way from the
leaves and mould which rest upon it. Leaves, still entire, or partially
decayed, are very indifferent conductors of heat, and, therefore, though
they diminish the warming influence of the summer sun on the soil below
them, they, on the other hand, prevent the escape of heat from that soil
in winter, and, consequently, in cold climates, even when the ground is
not covered by a protecting mantle of snow, the earth does not freeze to
as great a depth in the wood as in the open field.
e. _Trees as a Shelter to Ground to the Leeward._
The action of the forest, considered merely as a mechanical shelter to
grounds lying to the leeward of it, would seem to be an influence of too
restricted a character to deserve much notice; but many facts concur to
show that it is an important element in local climate, and that it is
often a valuable means of defence against the spread of miasmatic
effluvia, though, in this last case, it may exercise a chemical as well
as a mechanical agency. In the report of a committee appointed in 1836
to examine an article of the forest code of France, Arago observes: "If
a curtain of forest on the coasts of Normandy and of Brittany were
destroyed, these two provinces would become accessible to the winds from
the west, to the mild breezes of the sea. Hence a decrease of the cold
of winter. If a similar forest were to be cleared on the eastern border
of France, the glacial east wind would prevail with greater strength,
and the winters would become more severe. Thus the removal of a belt of
wood would produce opposite effects in the two regions."[134]
This opinion receives confirmation from an observation of Dr. Dwight,
who remarks, in reference to the woods of New England: "Another effect
of removing the forest will be the free passage of the winds, and among
them of the southern winds, over the surface. This, I think, has been an
increasing fact within my own remembrance. As the cultivation of the
country has extended farther to the north, the winds from the south have
reached distances more remote from the ocean, and imparted their warmth
frequently, and in such degrees as, forty years since, were in the same
places very little known. This fact, also, contributes to lengthen the
summer, and to shorten the winter-half of the year."[135]
It is thought in Italy that the clearing of the Apennines has very
materially affected the climate of the valley of the Po. It is asserted
in Le Alpi che cingono l'Italia that: "In consequence of the felling of
the woods on the Apennines, the sirocco prevails greatly on the right
bank of the Po, in the Parmesan territory, and in a part of Lombardy; it
injures the harvests and the vineyards, and sometimes ruins the crops of
the season. To the same cause many ascribe the meteorological changes in
the precincts of Modena and of Reggio. In the communes of these
districts, where formerly straw roofs resisted the force of the winds,
tiles are now hardly sufficient; in others, where tiles answered for
roofs, large slabs of stone are now ineffectual; and in many neighboring
communes the grapes and the grain are swept off by the blasts of the
south and southwest winds."
On the other hand, according to the same authority, the pinery of Porto,
near Ravenna--which is 33 kilometres long, and is one of the oldest pine
woods in Italy--having been replanted with resinous trees after it was
unfortunately cut, has relieved the city from the sirocco to which it
had become exposed, and in a great degree restored its ancient
climate.[136]
The felling of the woods on the Atlantic coast of Jutland has exposed
the soil not only to drifting sands, but to sharp sea winds, that have
exerted a sensible deteriorating effect on the climate of that
peninsula, which has no mountains to serve at once as a barrier to the
force of the winds, and as a storehouse of moisture received by
precipitation or condensed from atmospheric vapors.[137]
It is evident that the effect of the forest, as a mechanical impediment
to the passage of the wind, would extend to a very considerable distance
above its own height, and hence protect while standing, or lay open when
felled, a much larger surface than might at first thought be supposed.
The atmosphere, movable as are its particles, and light and elastic as
are its masses, is nevertheless held together as a continuous whole by
the gravitation of its atoms and their consequent pressure on each
other, if not by attraction between them, and, therefore, an obstruction
which mechanically impedes the movement of a given stratum of air, will
retard the passage of the strata above and below it. To this effect may
often be added that of an ascending current from the forest itself,
which must always exist when the atmosphere within the wood is warmer
than the stratum of air above it, and must be of almost constant
occurrence in the case of cold winds, from whatever quarter, because the
still air in the forest is slow in taking up the temperature of the
moving columns and currents around and above it. Experience, in fact,
has shown that mere rows of trees, and even much lower obstructions, are
of essential service in defending vegetation against the action of the
wind. Hardy proposes planting, in Algeria, belts of trees at the
distance of one hundred mètres from each other, as a shelter which
experience had proved to be useful in France.[138] "In the valley of the
Rhone," says Becquerel, "a simple hedge, two mètres in height, is a
sufficient protection for a distance of twenty-two mètres."[139] The
mechanical shelter acts, no doubt, chiefly as a defence against the
mechanical force of the wind, but its uses are by no means limited to
this effect. If the current of air which it resists moves horizontally,
it would prevent the access of cold or parching blasts to the ground for
a great distance; and did the wind even descend at a large angle with
the surface, still a considerable extent of ground would be protected by
a forest to the windward of it. If we suppose the trees of a wood to
have a mean height of only twenty yards, they would often beneficially
affect the temperature or the moisture of a belt of land two or three
hundred yards in width, and thus perhaps rescue valuable crops from
destruction.[140]
The local retardation of spring so much complained of in Italy, France,
and Switzerland, and the increased frequency of late frosts at that
season, appear to be ascribable to the admission of cold blasts to the
surface, by the felling of the forests which formerly both screened it
as by a wall, and communicated the warmth of their soil to the air and
earth to the leeward. Caimi states that since the cutting down of the
woods of the Apennines, the cold winds destroy or stunt the vegetation,
and that, in consequence of "the usurpation of winter on the domain of
spring," the district of Mugello has lost all its mulberries, except the
few which find in the lee of buildings a protection like that once
furnished by the forest.[141]
"It is proved," says Clavé, "Études," p. 44, "that the department of
Ardèche, which now contains not a single considerable wood, has
experienced within thirty years a climatic disturbance, of which the
late frosts, formerly unknown in the country, are one of the most
melancholy effects. Similar results have been observed in the plain of
Alsace, in consequence of the denudation of several of the crests of the
Vosges."
Dussard, as quoted by Ribbe,[142] maintains that even the _mistral_, or
northwest wind, whose chilling blasts are so fatal to tender vegetation
in the spring, "is the child of man, the result of his devastations."
"Under the reign of Augustus," continues he, "the forests which
protected the Cévennes were felled, or destroyed by fire, in mass. A
vast country, before covered with impenetrable woods--powerful obstacles
to the movement and even to the formation of hurricanes--was suddenly
denuded, swept bare, stripped, and soon after, a scourge hitherto
unknown struck terror over the land from Avignon to the Bouches du
Rhone, thence to Marseilles, and then extended its ravages, diminished
indeed by a long career which had partially exhausted its force, over
the whole maritime frontier. The people thought this wind a curse sent
of God. They raised altars to it and offered sacrifices to appease its
rage." It seems, however, that this plague was less destructive than at
present, until the close of the sixteenth century, when further
clearings had removed most of the remaining barriers to its course. Up
to that time, the northwest wind appears not to have attained to the
maximum of specific effect which now characterizes it as a local
phenomenon. Extensive districts, from which the rigor of the seasons has
now banished valuable crops, were not then exposed to the loss of their
harvests by tempests, cold, or drought. The deterioration was rapid in
its progress. Under the Consulate, the clearings had exerted so
injurious an effect upon the climate, that the cultivation of the olive
had retreated several leagues, and since the winters and springs of 1820
and 1836, this branch of rural industry has been abandoned in a great
number of localities where it was advantageously pursued before. The
orange now flourishes only at a few sheltered points of the coast, and
it is threatened even at Ilyères, where the clearing of the hills near
the town has proved very prejudicial to this valuable tree.
Marchand informs us that, since the felling of the woods, late spring
frosts are more frequent in many localities north of the Alps; that
fruit trees thrive well no longer, and that it is difficult to raise
young trees.[143]
f. _Trees as a Protection against Malaria._
The influence of forests in preventing the diffusion of miasmatic vapors
is a matter of less familiar observation, and perhaps does not come
strictly within the sphere of the present inquiry, but its importance
will justify me in devoting some space to the subject. "It has been
observed" (I quote again from Becquerel) "that humid air, charged with
miasmata, is deprived of them in passing through the forest. Rigaud de
Lille observed localities in Italy where the interposition of a screen
of trees preserved everything beyond it, while the unprotected grounds
were subject to fevers."[144] Few European countries present better
opportunities for observation on this point than Italy, because in that
kingdom the localities exposed to miasmatic exhalations are numerous,
and belts of trees, if not forests, are of so frequent occurrence that
their efficacy in this respect can be easily tested. The belief that
rows of trees afford an important protection against malarious
influences is very general among Italians best qualified by intelligence
and professional experience to judge upon the subject. The commissioners
appointed to report on the measures to be adopted for the improvement of
the Tuscan Maremme advised the planting of three or four rows of
poplars, _Populus alba_, in such directions as to obstruct the currents
of air from malarious localities, and thus intercept a great proportion
of the pernicious exhalations."[145] Lieutenant Maury even believed that
a few rows of sunflowers, planted between the Washington Observatory and
the marshy banks of the Potomac, had saved the inmates of that
establishment from the intermittent fevers to which they had been
formerly liable. Maury's experiments have been repeated in Italy. Large
plantations of sunflowers have been made upon the alluvial deposits of
the Oglio, above its entrance into the Lake of Iseo near Pisogne, and it
is said with favorable results to the health of the neighborhood.[146]
In fact, the generally beneficial effects of a forest wall or other
vegetable screen, as a protection against noxious exhalations from
marshes or other sources of disease situated to the windward of them,
are very commonly admitted.
It is argued that, in these cases, the foliage of trees and of other
vegetables exercises a chemical as well as a mechanical effect upon the
atmosphere, and some, who allow that forests may intercept the
circulation of the miasmatic effluvia of swampy soils, or even render
them harmless by decomposing them, contend, nevertheless, that they are
themselves active causes of the production of malaria. The subject has
been a good deal discussed in Italy, and there is some reason to think
that under special circumstances the influence of the forest in this
respect may be prejudicial rather than salutary, though this does not
appear to be generally the case.[147] It is, at all events, well known
that the great swamps of Virginia and the Carolinas, in climates nearly
similar to that of Italy, are healthy even to the white man, so long as
the forests in and around them remain, but become very insalubrious when
the woods are felled.[148]
_The Forest, as Inorganic Matter, tends to mitigate Extremes._
The surface which trees and leaves present augments the general
superficies of the earth exposed to the absorption of heat, and
increases the radiating and reflecting area in the same proportion. It
is impossible to measure the relative value of these two
elements--increase of absorbing and increase of emitting surface--as
thermometrical influences, because they exert themselves under
infinitely varied conditions; and it is equally impossible to make a
quantitative estimate of any partial, still more of the total effect of
the forest, considered as dead matter, on the temperature of the
atmosphere, and of the portion of the earth's surface acted on by it.
But it seems probable that its greatest influence in this respect is due
to its character of a screen, or mechanical obstacle to the transmission
of heat between the earth and the air; and this is equally true of the
standing tree and of the dead foliage which it deposits in successive
layers at its foot.
The complicated action of trees and their products, as dead absorbents,
radiators, reflectors, and conductors of heat, and as interceptors of
its transmission, is so intimately connected with their effects upon the
humidity of the air and the earth, and with all their living processes,
that it is difficult to separate the former from the latter class of
influences; but upon the whole, the forest must thus far be regarded as
tending to mitigate extremes, and, therefore, as an equalizer of
temperature.
TREES AS ORGANISMS.
_Specific Heat._
Trees, considered as organisms, produce in themselves, or in the air, a
certain amount of heat, by absorbing and condensing atmospheric vapor,
and they exert an opposite influence by absorbing water and exhaling it
in the form of vapor; but there is still another mode by which their
living processes may warm the air around them, independently of the
thermometric effects of condensation and evaporation. The vital heat of
a dozen persons raises the temperature of a room. If trees possess a
specific temperature of their own, an organic power of generating heat,
like that with which the warm-blooded animals are gifted, though by a
different process, a certain amount of weight is to be ascribed to this
element, in estimating the action of the forest upon atmospheric
temperature.
"Observation shows," says Meguscher, "that the wood of a living tree
maintains a temperature of +12° or 13° Cent. [= 54°, 56° Fahr.] when the
temperature of the air stands at 3°, 7°, and 8° [=37°, 46°, 47° F.]
above zero, and that the internal warmth of the tree does not rise and
fall in proportion to that of the atmosphere. So long as the latter is
below 18° [= 67° Fahr.], that of the tree is always the highest; but if
the temperature of the air rises to 18°, that of the vegetable growth is
the lowest. Since, then, trees maintain at all seasons a constant mean
temperature of 12° [= 54° Fahr.], it is easy to see why the air in
contact with the forest must be warmer in winter, cooler in summer, than
in situations where it is deprived of that influence."[149]
Boussingault remarks: "In many flowers there has been observed a very
considerable evolution of heat, at the approach of fecundation. In
certain _arums_ the temperature rises to 40° or 50° Cent. [= 104° or
122° Fahr.]. It is very probable that this phenomenon is general, and
varies only in the intensity with which it is manifested."[150]
If we suppose the fecundation of the flowers of forest trees to be
attended with a tenth only of this calorific power, they could not fail
to exert an important influence on the warmth of the atmospheric strata
in contact with them.
In a paper on Meteorology by Professor Henry, published in the United
States Patent Office Report for 1857, p. 504, that distinguished
physicist observes: "As a general deduction from chemical and mechanical
principles, we think no change of temperature is ever produced where the
actions belonging to one or both of these principles are not present.
Hence, in midwinter, when all vegetable functions are dormant, we do not
believe that any heat is developed by a tree, or that its interior
differs in temperature from its exterior further than it is protected
from the external air. The experiments which have been made on this
point, we think, have been directed by a false analogy. During the
active circulation of the sap and the production of new tissue,
variations of temperature belonging exclusively to the plant may be
observed; but it is inconsistent with general principles that heat
should be generated where no change is taking place."
There can be no doubt that moisture is given out by trees and evaporated
in extremely cold winter-weather, and unless new fluid were supplied
from the roots, the tree would be exhausted of its juices before winter
was over. But this is not observed to be the fact, and, though the point
is disputed, respectable authorities declare that "wood felled in the
depth of winter is the heaviest and fullest of sap."[151] Warm weather
in winter, of too short continuance to affect the temperature of the
ground sensibly, stimulates a free flow of sap in the maple. Thus, in
the last week of December, 1862, and the first week of January, 1863,
sugar was made from that tree, in various parts of New England. "A
single branch of a tree, admitted into a warm room in winter through an
aperture in a window, opened its buds and developed its leaves while the
rest of the tree in the external air remained in its winter sleep."[152]
The roots of forest trees in temperate climates, remain, for the most
part, in a moist soil, of a temperature not much below the annual mean,
through the whole winter; and we cannot account for the uninterrupted
moisture of the tree, unless we suppose that the roots furnish a
constant supply of water.
Atkinson describes a ravine in a valley in Siberia, which was filled
with ice to the depth of twenty-five feet. Poplars were growing in this
ice, which was thawed to the distance of some inches from the stem. But
the surface of the soil beneath it must have remained still frozen, for
the holes around the trees were full of water resulting from its
melting, and this would have escaped below if the ground had been
thawed. In this case, although the roots had not thawed the thick
covering of earth above them, the trunks must have melted the ice in
contact with them. The trees, when observed by Atkinson, were in full
leaf, but it does not appear at what period the ice around their stems
had melted.
From these facts, and others of the like sort, it would seem that "all
vegetable functions are" not absolutely "dormant" in winter, and,
therefore, that trees may give out _some_ heat at that season. But,
however this may be, the "circulation of the sap" commences at a very
early period in the spring, and the temperature of the air in contact
with trees may then be sufficiently affected by heat evolved in the
vital processes of vegetation, to raise the thermometric mean of wooded
countries for that season, and, of course, for the year.[153]
_Total Influence of the Forest on Temperature._
It has not yet been found practicable to measure, sum up, and equate the
total influence of the forest, its processes and its products, dead and
living, upon temperature, and investigators differ much in their
conclusions on this subject. It seems probable that in every particular
case the result is, if not determined, at least so much modified by
local conditions which are infinitely varied, that no general formula is
applicable to the question.
In the report to which I referred on page 149, Gay-Lussac says: "In my
opinion we have not yet any positive proof that the forest has, in
itself, any real influence on the climate of a great country, or of a
particular locality. By closely examining the effects of clearing off
the woods, we should perhaps find that, far from being an evil, it is an
advantage; but these questions are so complicated when they are examined
in a climatological point of view, that the solution of them is very
difficult, not to say impossible."
Becquerel, on the other hand, considers it certain that in tropical
climates, the destruction of the forests is accompanied with an
elevation of the mean temperature, and he thinks it highly probable that
it has the same effect in the temperate zones. The following is the
substance of his remarks on this subject:--
"Forests act as frigorific causes in three ways:
"1. They shelter the ground against solar irradiation and maintain a
greater humidity.
"2. They produce a cutaneous transpiration by the leaves.
"3. They multiply, by the expansion of their branches, the surfaces
which are cooled by radiation.
"These three causes acting with greater or less force, we must, in the
study of the climatology of a country, take into account the proportion
between the area of the forests and the surface which is bared of trees
and covered with herbs and grasses.
"We should be inclined to believe _à priori_, according to the foregoing
considerations, that the clearing of the woods, by raising the
temperature and increasing the dryness of the air, ought to react on
climate. There is no doubt that, if the vast desert of the Sahara were
to become wooded in the course of ages, the sands would cease to be
heated as much as at the present epoch, when the mean temperature is
twenty-nine degrees [centigrade, = 85° Fahr.]. In that case, the
ascending currents of warm air would cease, or be less warm, and would
not contribute, by descending in our latitudes, to soften the climate of
Western Europe. Thus the clearing of a great country may react on the
climates of regions more or less remote from it.
"The observations by Boussingault leave no doubt on this point. This
writer determined the mean temperature of wooded and of cleared points,
under the same latitude, and at the same elevation above the sea, in
localities comprised between the eleventh degree of north and the fifth
degree of south latitude, that is to say, in the portion of the tropics
nearest to the equator, and where radiation tends powerfully during the
night to lower the temperature under a sky without clouds."[154]
The result of these observations, which has been pretty generally
adopted by physicists, is that the mean temperature of cleared land in
the tropics appears to be about one degree centigrade, or a little less
than two degrees of Fahrenheit, above that of the forest. On page 147 of
the volume just cited, Becquerel argues that, inasmuch as the same and
sometimes a greater difference is found in favor of the open ground, at
points within the tropics so elevated as to have a temperate or even a
polar climate, we must conclude that the forests in Northern America
exert a refrigerating influence equally powerful. But the conditions of
the soil are so different in the two regions compared, that I think we
cannot, with entire confidence, reason from the one to the other, and it
is much to be desired that observations be made on the summer and winter
temperature of both the air and the ground in the depths of the North
American forests, before it is too late.[155]
INFLUENCE OF FORESTS ON THE HUMIDITY OF THE AIR AND THE EARTH.
a. _As Inorganic Matter._
The most important influence of the forest on climate is, no doubt, that
which it exercises on the humidity of the air and the earth, and this
climatic action it exerts partly as dead, partly as living matter. By
its interposition as a curtain between the sky and the ground, it
intercepts a large proportion of the dew and the lighter showers, which
would otherwise moisten the surface of the soil, and restores it to the
atmosphere by evaporation; while in heavier rains, the large drops which
fall upon the leaves and branches are broken into smaller ones, and
consequently strike the ground with less mechanical force, or are
perhaps even dispersed into vapor without reaching it.[156] As a screen,
it prevents the access of the sun's rays to the earth, and, of course,
an elevation of temperature which would occasion a great increase of
evaporation. As a mechanical obstruction, it impedes the passage of air
currents over the ground, which, as is well known, is one of the most
efficient agents in promoting evaporation and the refrigeration
resulting from it.[157] In the forest, the air is almost quiescent, and
moves only as local changes of temperature affect the specific gravity
of its particles. Hence there is often a dead calm in the woods when a
furious blast is raging in the open country at a few yards' distance.
The denser the forest--as for example, where it consists of spike-leaved
trees, or is thickly intermixed with them--the more obvious is its
effect, and no one can have passed from the field to the wood in cold,
windy weather, without having remarked it.[158]
The vegetable mould, resulting from the decomposition of leaves and of
wood, carpets the ground with a spongy covering which obstructs the
evaporation from the mineral earth below, drinks up the rains and
melting snows that would otherwise flow rapidly over the surface and
perhaps be conveyed to the distant sea, and then slowly gives out, by
evaporation, infiltration, and percolation, the moisture thus imbibed.
The roots, too, penetrate far below the superficial soil, conduct the
water along their surface to the lower depths to which they reach, and
thus serve to drain the superior strata and remove the moisture out of
the reach of evaporation.
b. _The Forest as Organic._
These are the principal modes in which the humidity of the atmosphere is
affected by the forest regarded as lifeless matter. Let us inquire how
its organic processes act upon this meteorological element.
The commonest observation shows that the wood and bark of living trees
are always more or less pervaded with watery and other fluids, one of
which, the sap, is very abundant in trees of deciduous foliage when the
buds begin to swell and the leaves to develop themselves in the spring.
The outer bark of most trees is of a corky character, not admitting the
absorption of much moisture from the atmosphere through its pores, and
we can hardly suppose that the buds are able to extract from the air a
much larger supply. The obvious conclusion as to the source from which
the extraordinary quantity of sap at this season is derived, is that to
which scientific investigation leads us, namely, that it is absorbed
from the earth by the roots, and thence distributed to all parts of the
plant. Popular opinion, indeed, supposes that all the vegetable fluids,
during the entire period of growth, are thus drawn from the bosom of the
earth, and that the wood and other products of the tree are wholly
formed from matter held in solution in the water abstracted by the roots
from the ground. This is an error, for, not only is the solid matter of
the tree, in a certain proportion not important to our present inquiry,
received from the atmosphere in a gaseous form, through the pores of the
leaves and of the young shoots, but water in the state of vapor is
absorbed and contributed to the circulation, by the same organs.[159]
The amount of water taken up by the roots, however, is vastly greater
than that imbibed through the leaves, especially at the season when the
juices are most abundant, and when, as we have seen, the leaves are yet
in embryo. The quantity of water thus received from the air and the
earth, in a single year, by a wood of even a hundred acres, is very
great, though experiments are wanting to furnish the data for even an
approximate estimate of its measure; for only the vaguest conclusions
can be drawn from the observations which have been made on the
imbibition and exhalation of water by trees and other plants reared in
artificial conditions diverse from those of the natural forest.[160]
_Wood Mosses and Fungi._
Besides the water drawn by the roots from the earth and the vapor
absorbed by the leaves from the air, the wood mosses and fungi, which
abound in all dense forests, take up a great quantity of moisture from
the atmosphere when it is charged with humidity, and exhale it again
when the air is dry. These humble organizations, which play a more
important part in regulating the humidity of the air than writers on the
forest have usually assigned to them, perish with the trees they grow
on; but, in many situations, nature provides a compensation for the tree
mosses in ground species, which, on cold soils, especially those with a
northern exposure, spring up abundantly both before the woods are
felled, and when the land is cleared and employed for pasturage, or
deserted. These mosses discharge a portion of the functions appropriated
to the wood, and while they render the soil of improved lands much less
fit for agricultural use, they, at the same time, prepare it for the
growth of a new harvest of trees, when the infertility they produce
shall have driven man to abandon it and suffer it to relapse into the
hands of nature.[161]
_Flow of Sap._
The amount of sap which can be withdrawn from living trees furnishes,
not indeed a measure of the quantity of water sucked up by their roots
from the ground--for we cannot extract from a tree its whole
moisture--but numerical data which may aid the imagination to form a
general notion of the powerful action of the forest as an absorbent of
humidity from the earth.
The only forest tree known to Europe and North America, the sap of which
is largely enough applied to economical uses to have made the amount of
its flow a matter of practical importance and popular observation, is
the sugar maple, _Acer saccharinum_, of the Anglo-American Provinces and
States. In the course of a single "sugar season," which lasts ordinarily
from twenty-five to thirty days, a sugar maple two feet in diameter will
yield not less than twenty gallons of sap, and sometimes much more.[162]
This, however, is but a trifling proportion of the water abstracted
from the earth by the roots during this season, when the yet undeveloped
leaves can hardly absorb an appreciable quantity of vapor from the
atmosphere;[163] for all this fluid runs from two or three incisions or
auger holes, so narrow as to intercept the current of comparatively few
sap vessels, and besides, experience shows that large as is the quantity
withdrawn from the circulation, it is relatively too small to affect
very sensibly the growth of the tree.[164] The number of large maple
trees on an acre is frequently not less than fifty,[165] and of course
the quantity of moisture abstracted from the soil by this tree alone is
measured by thousands of gallons to the acre. The sugar orchards, as
they are called, contain also many young maples too small for tapping,
and numerous other trees--two of which, at least, the black birch,
_Betula lenta_, and yellow birch, _Betula excelsa_, both very common in
the same climate, are far more abundant in sap than the maple[166]--are
scattered among the sugar trees; for the North American native forests
are remarkable for the mixture of their crops.
The sap of the maple, and of other trees with deciduous leaves which
grow in the same climate, flows most freely in the early spring, and
especially in clear weather, when the nights are frosty and the days
warm; for it is then that the melting snows supply the earth with
moisture in the justest proportion, and that the absorbent power of the
roots is stimulated to its highest activity.[167]
When the buds are ready to burst, and the green leaves begin to show
themselves beneath their scaly covering, the ground has become drier,
the thirst of the roots is quenched, and the flow of sap from them to
the stem is greatly diminished.[168]
_Absorption and Exhalation of Moisture._
The leaves now commence the process of absorption, and imbibe both
uncombined gases and an unascertained but perhaps considerable quantity
of watery vapor from the humid atmosphere of spring which bathes them.
The organic action of the tree, as thus far described, tends to the
desiccation of air and earth; but when we consider what volumes of water
are daily absorbed by a large tree, and how small a proportion of the
weight of this fluid consists of matter which enters into new
combinations, and becomes a part of the solid framework of the
vegetable, or a component of its deciduous products, it is evident that
the superfluous moisture must somehow be carried off almost as rapidly
as it flows into the tree.[169] At the very commencement of vegetation
in spring, some of this fluid certainly escapes through the buds, the
nascent foliage, and the pores of the barb, and vegetable physiology
tells us that there is a current of sap toward the roots as well as from
them.[170] I do not know that the exudation of water into the earth,
through the bark or at the extremities of these latter organs, has been
directly proved, but the other known modes of carrying off the surplus
do not seem adequate to dispose of it at the almost leafless period when
it is most abundantly received, and it is therefore difficult to believe
that the roots do not, to some extent, drain as well as flood the
watercourses of their stem. Later in the season the roots absorb less,
and the now developed leaves exhale a vastly increased quantity of
moisture into the air. In any event, all the water derived by the
growing tree from the atmosphere and the ground is returned again by
transpiration or exudation, after having surrendered to the plant the
small proportion of matter required for vegetable growth which it held
in solution or suspension.[171] The hygrometrical equilibrium is then
restored, so far as this: the tree yields up again the moisture it had
drawn from the earth and the air, though it does not return it each to
each; for the vapor carried off by transpiration greatly exceeds the
quantity of water absorbed by the foliage from the atmosphere, and the
amount, if any, carried back to the ground by the roots.
The evaporation of the juices of the plant, by whatever process
effected, takes up atmospheric heat and produces refrigeration. This
effect is not less real, though much less sensible, in the forest than
in meadow or pasture land, and it cannot be doubted that the local
temperature is considerably affected by it. But the evaporation that
cools the air diffuses through it, at the same time, a medium which
powerfully resists the escape of heat from the earth by radiation.
Visible vapors or clouds, it is well known, prevent frosts by
obstructing radiation, or rather by reflecting back again the heat
radiated by the earth, just as any mechanical screen would do. On the
other hand, clouds intercept the rays of the sun also, and hinder its
heat from reaching the earth. The invisible vapors given out by leaves
impede the passage of heat reflected and radiated by the earth and by
all terrestrial objects, but oppose much less resistance to the
transmission of direct solar heat, and indeed the beams of the sun seem
more scorching when received through clear air charged with uncondensed
moisture than after passing through a dry atmosphere. Hence the
reduction of temperature by the evaporation of moisture from vegetation,
though sensible, is less than it would be if water in the gaseous state
were as impervious to heat given out by the sun as to that emitted by
terrestrial objects.
The hygroscopicity of vegetable mould is much greater than that of any
mineral earth, and therefore the soil of the forest absorbs more
atmospheric moisture than the open ground. The condensation of the vapor
by absorption disengages heat, and consequently raises the temperature
of the soil which absorbs it. Von Babo found the temperature of sandy
earth thus elevated from 20° to 27° centigrade, making a difference of
nearly thirteen degrees of Fahrenheit, and that of soil rich in humus
from 20° to 31° centigrade, a difference of almost twenty degrees of
Fahrenheit.[172]
_Balance of Conflicting Influences._
We have shown that the forest, considered as dead matter, tends to
diminish the moisture of the air, by preventing the sun's rays from
reaching the ground and evaporating the water that falls upon the
surface, and also by spreading over the earth a spongy mantle which
sucks up and retains the humidity it receives from the atmosphere,
while, at the same time, this covering acts in the contrary direction by
accumulating, in a reservoir not wholly inaccessible to vaporizing
influences, the water of precipitation which might otherwise suddenly
sink deep into the bowels of the earth, or flow by superficial channels
to other climatic regions. We now see that, as a living organism, it
tends, on the one hand, to diminish the humidity of the air by absorbing
moisture from it, and, on the other, to increase that humidity by
pouring out into the atmosphere, in a vaporous form, the water it draws
up through its roots. This last operation, at the same time, lowers the
temperature of the air in contact with or proximity to the wood, by the
same law as in other cases of the conversion of water into vapor.
As I have repeatedly said, we cannot measure the value of any one of
these elements of climatic disturbance, raising or lowering of
temperature, increase or diminution of humidity, nor can we say that in
any one season, any one year, or any one fixed cycle, however long or
short, they balance and compensate each other. They are sometimes, but
certainly not always, contemporaneous in their action, whether their
tendency is in the same or in opposite directions, and, therefore, their
influence is sometimes cumulative, sometimes conflicting; but, upon the
whole, their general effect seems to be to mitigate extremes of
atmospheric heat and cold, moisture and drought. They serve as
equalizers of temperature and humidity, and it is highly probable that,
in analogy with most other works and workings of nature, they, at
certain or uncertain periods, restore the equilibrium which, whether as
lifeless masses or as living organisms, they may have temporarily
disturbed.
When, therefore, man destroyed these natural harmonizers of climatic
discords, he sacrificed an important conservative power, though it is
far from certain that he has thereby affected the mean, however much he
may have exaggerated the extremes of atmospheric temperature and
humidity, or, in other words, may have increased the range and
lengthened the scale of thermometric and hygrometric variation.
_Influence of the Forest on Temperature and Precipitation._
Aside from the question of compensation, it does not seem probable that
the forests sensibly affect the total quantity of precipitation, or the
general mean of atmospheric temperature of the globe, or even that they
had this influence when their extent was vastly greater than at present.
The waters cover about three fourths of the face of the earth,[173] and
if we deduct the frozen zones, the peaks and crests of lofty mountains
and their craggy slopes, the Sahara and other great African and Asiatic
deserts, and all such other portions of the solid surface as are
permanently unfit for the growth of wood, we shall find that probably
not one tenth of the total superficies of our planet was ever, at any
one time in the present geological epoch, covered with forests. Besides
this, the distribution of forest land, of desert, and of water, is such
as to reduce the possible influence of the former to a low expression;
for the forests are, in large proportion, situated in cold or temperate
climates, where the action of the sun is comparatively feeble both in
elevating temperature and in promoting evaporation; while, in the torrid
zone, the desert and the sea--the latter of which always presents an
evaporable surface--enormously preponderate. It is, upon the whole, not
probable that so small an extent of forest, so situated, could produce
an appreciable influence on the _general_ climate of the globe, though
it might appreciably affect the local action of all climatic elements.
The total annual amount of solar heat absorbed and radiated by the
earth, and the sum of terrestrial evaporation and atmospheric
precipitation must be supposed constant; but the distribution of heat
and of humidity is exposed to disturbance in both time and place, by a
multitude of local causes, among which the presence or absence of the
forest is doubtless one.
So far as we are able to sum up the general results, it would appear
that, in countries in the temperate zone still chiefly covered with
wood, the summers would be cooler, moister, shorter, the winters milder,
drier, longer, than in the same regions after the removal of the forest.
The slender historical evidence we possess seems to point to the same
conclusion, though there is some conflict of testimony and of opinion on
this point, and some apparently well-established exceptions to
particular branches of what appears to be the general law.
One of these occurs both in climates where the cold of winter is severe
enough to freeze the ground to a considerable depth, as in Sweden and
the Northern States of the American Union, and in milder zones, where
the face of the earth is exposed to cold mountain winds, as in some
parts of Italy and of France; for there, as we have seen, the winter is
believed to extend itself into the months which belong to the spring,
later than at periods when the forest covered the greater part of the
ground.[174] More causes than one doubtless contribute to this result;
but in the case of Sweden and the United States, the most obvious
explanation of the fact is to be found in the loss of the shelter
afforded to the ground by the thick coating of leaves which the forest
sheds upon it, and the snow which the woods protect from blowing away,
or from melting in the brief thaws of winter. I have already remarked
that bare ground freezes much deeper than that which is covered by beds
of leaves, and when the earth is thickly coated with snow, the strata
frozen before it fell begin to thaw. It is not uncommon to find the
ground in the woods, where the snow lies two or three feet deep,
entirely free from frost, when the atmospheric temperature has been for
several weeks below the freezing point, and for some days even below the
zero of Fahrenheit. When the ground is cleared and brought under
cultivation, the leaves are ploughed into the soil and decomposed, and
the snow, especially upon knolls and eminences, is blown off, or
perhaps half thawed, several times during the winter. The water from the
melting snow runs into the depressions, and when, after a day or two of
warm sunshine or tepid rain, the cold returns, it is consolidated to
ice, and the bared ridges and swells of earth are deeply frozen.[175] It
requires many days of mild weather to raise the temperature of soil in
this condition, and of the air in contact with it, to that of the earth
in the forests of the same climatic region. Flora is already plaiting
her sylvan wreath before the corn flowers which are to deck the garland
of Ceres have waked from their winter's sleep; and it is not a popular
error to believe that, where man has substituted his artificial crops
for the spontaneous harvest of nature, spring delays her coming.
In many cases, the apparent change in the period of the seasons is a
purely local phenomenon, which is probably compensated by a higher
temperature in other months, without any real disturbance of the average
thermometrical equilibrium. We may easily suppose that there are
analogous partial deviations from the general law of precipitation; and,
without insisting that the removal of the forest has diminished the sum
total of snow and rain, we may well admit that it has lessened the
quantity which annually falls within particular limits. Various
theoretical considerations make this probable, the most obvious
argument, perhaps, being that drawn from the generally admitted fact,
that the summer and even the mean temperature of the forest is below
that of the open country in the same latitude. If the air in a wood is
cooler than that around it, it must reduce the temperature of the
atmospheric stratum immediately above it, and, of course, whenever a
saturated current sweeps over it, it must produce precipitation which
would fall upon or near it.
But the subject is so exceedingly complex and difficult, that it is
safer to regard it as a historical problem, or at least as what lawyers
call a mixed question of law and fact, than to attempt to decide it upon
_à priori_ grounds. Unfortunately the evidence is conflicting in
tendency, and sometimes equivocal in interpretation, but I believe that
a majority of the foresters and physicists who have studied the question
are of opinion that in many, if not in all cases, the destruction of the
woods has been followed by a diminution in the annual quantity of rain
and dew. Indeed, it has long been a popularly settled belief that
vegetation and the condensation and fall of atmospheric moisture are
reciprocally necessary to each other, and even the poets sing of
Afric's barren sand,
Where nought can grow, because it raineth not,
And where no rain can fall to bless the land,
Because nought grows there.[176]
Before stating the evidence on the general question and citing the
judgments of the learned upon it, however, it is well to remark that the
comparative variety or frequency of inundations in earlier and later
centuries is not necessarily, in most cases not probably, entitled to
any weight whatever, as a proof that more or less rain fell formerly
than now; because the accumulation of water in the channel of a river
depends far less upon the quantity of precipitation in its valley, than
upon the rapidity with which it is conducted, on or under the surface of
the ground, to the central artery that drains the basin. But this point
will be more fully discussed in a subsequent chapter.
There is another important observation which may properly be introduced
here. It is not universally, or even generally true, that the atmosphere
returns its humidity to the local source from which it receives it. The
air is constantly in motion,
----howling tempests scour amain
From sea to land, from land to sea;[177]
and, therefore, it is always probable that the evaporation drawn up by
the atmosphere from a given river, or sea, or forest, or meadow, will be
discharged by precipitation, not at or near the point where it rose, but
at a distance of miles, leagues, or even degrees. The currents of the
upper air are invisible, and they leave behind them no landmark to
record their track. We know not whence they come, or whither they go. We
have a certain rapidly increasing acquaintance with the laws of general
atmospheric motion, but of the origin and limits, the beginning and end
of that motion, as it manifests itself at any particular time and place,
we know nothing. We cannot say where or when the vapor, exhaled to-day
from the lake on which we float, will be condensed and fall; whether it
will waste itself on a barren desert, refresh upland pastures, descend
in snow on Alpine heights, or contribute to swell a distant torrent
which shall lay waste square miles of fertile corn land; nor do we know
whether the rain which feeds our brooklets is due to the transpiration
from a neighboring forest, or to the evaporation from a far-off sea. If,
therefore, it were proved that the annual quantity of rain and dew is
now as great on the plains of Castile, for example, as it was when they
were covered with the native forest, it would by no means follow that
those woods did not augment the amount of precipitation elsewhere.
But I return to the question. Beginning with the latest authorities, I
cite a passage from Clavé.[178] After arguing that we cannot reason from
the climatic effects of the forest in tropical and sub-tropical
countries as to its influence in temperate latitudes, the author
proceeds: "The action of the forests on rain, a consequence of that
which they exercise on temperature, is difficult to estimate in our
climate, but is very pronounced in hot countries, and is established by
numerous examples. M. Boussingault states that in the region comprised
between the Bay of Cupica and the Gulf of Guayaquil, which is covered
with immense forests, the rains are almost continual, and that the mean
temperature of this humid country rises hardly to twenty-six degrees (=
80° Fahr.). M. Blanqui, in his 'Travels in Bulgaria,' informs us that at
Malta rain has become so rare, since the woods were cleared to make room
for the growth of cotton, that at the time of his visit in October,
1841, not a drop of rain had fallen for three years.[179] The terrible
droughts which desolate the Cape Verd Islands must also be attributed to
the destruction of the forests. In the Island of St. Helena, where the
wooded surface has considerably extended within a few years, it has been
observed that the rain has increased in the same proportion. It is now
in quantity double what it was during the residence of Napoleon. In
Egypt, recent plantations have caused rains, which hitherto were almost
unknown."
Schacht[180] observes: "In wooded countries, the atmosphere is generally
humid, and rain and dew fertilize the soil. As the lightning rod
abstracts the electric fluid from the stormy sky, so the forest attracts
to itself the rain from the clouds, which, in falling, refreshes not it
alone, but extends its benefits to the neighboring fields. * * The
forest, presenting a considerable surface for evaporation, gives to its
own soil and to all the adjacent ground an abundant and enlivening dew.
There falls, it is true, less dew on a tall and thick wood than on the
surrounding meadows, which, being more highly heated during the day by
the influence of insolation, cool with greater rapidity by radiation.
But it must be remarked, that this increased deposition of dew on the
neighboring fields is partly due to the forests themselves; for the
dense, saturated strata of air which hover over the woods descend in
cool, calm evenings, like clouds, to the valley, and in the morning,
beads of dew sparkle on the leaves of the grass and the flowers of the
field. Forests, in a word, exert, in the interior of continents, an
influence like that of the sea on the climate of islands and of coasts:
both water the soil and thereby insure its fertility." In a note upon
this passage, quoting as authority the _Historia de la Conquista de las
siete islas de Gran Canaria, de Juan de Abreu Galindo_, 1632, p. 47, he
adds: "Old historians relate that a celebrated laurel in Ferro formerly
furnished drinkable water to the inhabitants of the island. The water
flowed from its foliage, uninterruptedly, drop by drop, and was
collected in cisterns. Every morning the sea breeze drove a cloud toward
the wonderful tree, which attracted it to its huge top," where it was
condensed to a liquid form.
In a number of the _Missionary Herald_, published at Boston, the date of
which I have mislaid, the Rev. Mr. Van Lennep, well known as a competent
observer, gives the following remarkable account of a similar fact
witnessed by him in an excursion to the east of Tocat in Asia Minor:
"In this region, some 3,000 feet above the sea, the trees are mostly
oak, and attain a large size. I noticed an illustration of the influence
of trees in general in collecting moisture. Despite the fog, of a week's
duration, the ground was everywhere perfectly dry. The dry oak leaves,
however, had gathered the water, and the branches and trunks of the
trees were more or less wet. In many cases the water had run down the
trunk and moistened the soil around the roots of the tree. In two
places, several trees had each furnished a small stream of water, and
these, uniting, had run upon the road, so that travellers had to pass
through the mud; although, as I said, everywhere else the ground was
perfectly dry. Moreover, the collected moisture was not sufficient to
drop directly from the leaves, but in every case it ran down the
branches and trunk to the ground. Farther on we found a grove, and at
the foot of each tree, on the north side, was a lump of ice, the water
having frozen as it reached the ground. This is a most striking
illustration of the acknowledged influence of trees in collecting
moisture; and one cannot for a moment doubt, that the parched regions
which commence at Sivas, and extend in one direction to the Persian
Gulf, and in another to the Red Sea, were once a fertile garden, teeming
with a prosperous population, before the forests which covered the
hillsides were cut down--before the cedar and the fir tree were rooted
up from the sides of Lebanon.
"As we now descended the northern side of the watershed, we passed
through the grove of walnut, oak, and black mulberry trees, which shade
the village of Oktab, whose houses, cattle, and ruddy children were
indicative of prosperity."
Coultas thus argues: "The ocean, winds, and woods may be regarded as the
several parts of a grand distillatory apparatus. The sea is the boiler
in which vapor is raised by the solar heat, the winds are the guiding
tubes which carry the vapor with them to the forests where a lower
temperature prevails. This naturally condenses the vapor, and showers of
rain are thus distilled from the cloud masses which float in the
atmosphere, by the woods beneath them."[181]
Sir John F. W. Herschel enumerates among "the influences unfavorable to
rain," "absence of vegetation in warm climates, and especially of trees.
This is, no doubt," continues he, "one of the reasons of the extreme
aridity of Spain. The hatred of a Spaniard toward a tree is proverbial.
Many districts in France have been materially injured by denudation
(Earl of Lovelace on Climate, etc.), and, on the other hand, rain has
become more frequent in Egypt since the more vigorous cultivation of the
palm tree."
Hohenstein remarks: "With respect to the temperature in the forest, I
have already observed that, at certain times of the day and of the year,
it is less than in the open field. Hence the woods may, in the daytime,
in summer and toward the end of winter, tend to increase the fall of
rain; but it is otherwise in summer nights and at the beginning of
winter, when there is a higher temperature in the forest, which is not
favorable to that effect. * * * The wood is, further, like the mountain,
a mechanical obstruction to the motion of rain clouds, and, as it checks
them in their course, it gives them occasion to deposit their water.
These considerations render it probable that the forest increases the
quantity of rain; but they do not establish the certainty of this
conclusion, because we have no positive numerical data to produce on the
depression of temperature, and the humidity of the air in the
woods."[182]
Barth presents the following view of the subject: "The ground in the
forest, as well as the atmospheric stratum over it, continues humid
after the woodless districts have lost their moisture; and the air,
charged with the humidity drawn from them, is usually carried away by
the winds before it has deposited itself in a condensed form on the
earth. Trees constantly transpire through their leaves a great quantity
of moisture, which they partly absorb again by the same organs, while
the greatest part of their supply is pumped up through their widely
ramifying roots from considerable depths in the ground. Thus a constant
evaporation is produced, which keeps the forest atmosphere moist even in
long droughts, when all other sources of humidity in the forest itself
are dried up. * * * Little is required to compel the stratum of air
resting upon a wood to give up its moisture, which thus, as rain, fog,
or dew, is returned to the forest. * * * The warm, moist currents of
air which come from other regions are cooled as they approach the wood
by its less heated atmosphere, and obliged to let fall the humidity with
which they are charged. The woods contribute to the same effect by
mechanically impeding the motion of fog and rain cloud, whose particles
are thus accumulated and condensed to rain. The forest thus has a
greater power than the open ground to retain within its own limits
already existing humidity, and to preserve it, and it attracts and
collects that which the wind brings it from elsewhere, and forces it to
deposit itself as rain or other precipitation. * * * In consequence of
these relations of the forest to humidity, it follows that wooded
districts have both more frequent and more abundant rain, and in general
are more humid, than woodless regions; for what is true of the woods
themselves, in this respect, is true also of their treeless
neighborhood, which, in consequence of the ready mobility of the air and
its constant changes, receives a share of the characteristics of the
forest atmosphere, coolness and moisture. * * * When the districts
stripped of trees have long been deprived of rain and dew, * * * and the
grass and the fruits of the field are ready to wither, the grounds which
are surrounded by woods are green and flourishing. By night they are
refreshed with dew, which is never wanting in the moist air of the
forest, and in due season they are watered by a beneficent shower, or a
mist which rolls slowly over them."[183]
Asbjörnsen, after adducing the familiar theoretical arguments on this
point, adds: "The rainless territories in Peru and North Africa
establish this conclusion, and numerous other examples show that woods
exert an influence in producing rain, and that rain fails where they are
wanting; for many countries have, by the destruction of the forests,
been deprived of rain, moisture, springs, and watercourses, which are
necessary for vegetable growth. * * * The narratives of travellers show
the deplorable consequences of felling the woods in the Island of
Trinidad, Martinique, San Domingo, and indeed, in almost the entire
West Indian group. * * * In Palestine and many other parts of Asia and
Northern Africa, which in ancient times were the granaries of Europe,
fertile and populous, similar consequences have been experienced. These
lands are now deserts, and it is the destruction of the forests alone
which has produced this desolation. * * * In Southern France, many
districts have, from the same cause, become barren wastes of stone, and
the cultivation of the vine and the olive has suffered severely since
the baring of the neighboring mountains. Since the extensive clearings
between the Spree and the Oder, the inhabitants complain that the clover
crop is much less productive than before. On the other hand, examples of
the beneficial influence of planting and restoring the woods are not
wanting. In Scotland, where many miles square have been planted with
trees, this effect has been manifest, and similar observations have been
made in several places in Southern France. In Lower Egypt, both at Cairo
and near Alexandria, rain rarely fell in considerable quantity--for
example, during the French occupation of Egypt, about 1798, it did not
rain for sixteen months--but since Mehemet Aali and Ibrahim Pacha
executed their vast plantations (the former alone having planted more
than twenty millions of olive and fig trees, cottonwood, oranges,
acacias, planes, &c.), there now falls a good deal of rain, especially
along the coast, in the months of November, December, and January; and
even at Cairo it rains both oftener and more abundantly, so that real
showers are no rarity."[184]
Babinet, in one of his lectures,[185] cites the supposed fact of the
increase of rain in Egypt in consequence of the planting of trees, and
thus remarks upon it: "A few years ago it never rained in Lower Egypt.
The constant north winds, which almost exclusively prevail there, passed
without obstruction over a surface bare of vegetation. Grain was kept
on the roofs in Alexandria, without being covered or otherwise
protected from injury by the atmosphere; but since the making of
plantations, an obstacle has been created which retards the current of
air from the north. The air thus checked, accumulates, dilates, cools,
and yields rain.[186] The forests of the Vosges and Ardennes produce
the same effects in the north east of France, and send us a great river,
the Meuse, which is as remarkable for its volume as for the small extent
of its basin. With respect to the retardation of the atmospheric
currents, and the effects of that retardation, one of my illustrious
colleagues, M. Mignet, who is not less a profound thinker than an
eloquent writer, suggested to me that, to produce rain, a forest was as
good as a mountain, and this is literally true."
Monestier-Savignat arrives at this conclusion: "Forests on the one hand
diminish evaporation; on the other, they act on the atmosphere as
refrigerating causes. The second scale of the balance predominates over
the other, for it is established that in wooded countries it rains
oftener, and that, the quantity of rain being equal, they are more
humid."[187]
Boussingault--whose observations on the drying up of lakes and springs,
from the destruction of the woods, in tropical America, have often been
cited as a conclusive proof that the quantity of rain was thereby
diminished--after examining the question with much care, remarks: "In my
judgment it is settled that very large clearings must diminish the
annual fall of rain in a country;" and on a subsequent page, he
concludes that, "arguing from meteorological facts collected in the
equinoctial regions, there is reason to presume that clearings diminish
the annual fall of rain."[188]
The same eminent author proposes series of observations on the level of
natural lakes, especially on those without outlet, as a means of
determining the increase or diminution of precipitation in their basins,
and, of course, of measuring the effect of clearing when such
operations take place within those basins. But it must be observed that
lakes without a visible outlet are of very rare occurrence, and besides,
where no superficial conduit for the discharge of lacustrine waters
exists, we can seldom or never be sure that nature has not provided
subterranean channels for their escape. Indeed, when we consider that
most earths, and even some rocks under great hydrostatic pressure, are
freely permeable by water, and that fissures are frequent in almost all
rocky strata, it is evident that we cannot know in what proportion the
depression of the level of a lake is to be ascribed to infiltration, to
percolation, or to evaporation.[189] Further, we are, in general, as
little able to affirm that a given lake derives all its water from the
fall of rain within its geographical basin, or that it receives all the
water that falls in that basin except what evaporates from the ground,
as we are to show that all its superfluous water is carried off by
visible channels and by evaporation.
Suppose the strata of the mountains on two sides of a lake, east and
west, to be tilted in the same direction, and that those of the hill on
the east side incline toward the lake, those of that on the west side
from it. In this case a large proportion of the rain which falls on the
eastern slope of the eastern hill may find its way between the strata to
the lake, and an equally large proportion of the precipitation upon the
eastern slope of the western ridge may escape out of the basin by
similar channels. In such case the clearing of the _outer_ slopes of
either or both mountains, while the forests of the _inner_ declivities
remained intact, might affect the quantity of water received by the
lake, and it would always be impossible to know to what territorial
extent influences thus affecting the level of a lake might reach.
Boussingault admits that extensive clearing _below_ an alpine lake, even
at a considerable distance, might affect the level of its waters. How it
would produce this influence he does not inform us, but, as he says
nothing of the natural subterranean drainage of surface waters, it is to
be presumed that he refers to the supposed diminution of the quantity of
rain from the removal of the forest, which might manifest itself at a
point more elevated than the cause which occasioned it. The elevation or
depression of the level of natural lakes, then, cannot be relied upon as
a proof, still less as a measure of an increase or diminution in the
fall of rain within their geographical basins, resulting from the
felling of the woods which covered them; though such phenomena afford
very strong presumptive evidence that the supply of water is somehow
augmented or lessened. The supply is, in most cases, derived much less
from the precipitation which falls directly upon the surface of lakes,
than from waters which flow above or under the ground around them, and
which, in the latter case, often come from districts not comprised
within what superficial geography would regard as belonging to the lake
basins.
It is, upon the whole, evident that the question can hardly be
determined except by the comparison of pluviometrical observations made
at a given station before and after the destruction of the woods. Such
observations, unhappily, are scarcely to be found, and the opportunity
for making them is rapidly passing away, except so far as a converse
series might be collected in countries--France, for example--where
forest plantation is now going on upon a large scale. The Smithsonian
Institution at Washington is well situated for directing the attention
of observers in the newer territory of the United States to this
subject, and it is to be hoped that it will not fail to avail itself of
its facilities for this purpose.
Numerous other authorities might be cited in support of the proposition
that forests tend, at least in certain latitudes and at certain seasons,
to produce rain; but though the arguments of the advocates of this
doctrine are very plausible, not to say convincing, their opinions are
rather _à priori_ conclusions from general meteorological laws, than
deductions from facts of observation, and it is remarkable that there is
so little direct evidence on the subject.
On the other hand, Foissac expresses the opinion that forests have no
influence on precipitation, beyond that of promoting the deposit of dew
in their vicinity, and he states, as a fact of experience, that the
planting of large vegetables, and especially of trees, is a very
efficient means of drying morasses, because the plants draw from the
earth a quantity of water larger than the average annual fall of
rain.[190] Klöden, admitting that the rivers Oder and Elbe have
diminished in quantity of water, the former since 1778, the latter since
1828, denies that the diminution of volume is to be ascribed to a
decrease of precipitation in consequence of the felling of the forests,
and states, what other physicists confirm, that, during the same period,
meteorological records in various parts of Europe show rather an
augmentation than a reduction of rain.[191]
The observations of Belgrand tend to show, contrary to the general
opinion, that less rain falls in wooded than in denuded districts. He
compared the precipitation for the year 1852, at Vezelay in the valley
of the Bouchat, and at Avallon in the valley of the Grenetière. At the
first of these places it was 881 millimètres, at the latter 581
millimètres. The two cities are not more than eight miles apart. They
are at the same altitude, and it is stated that the only difference in
their geographical conditions consists in the different proportions of
forest and cultivated country around them, the basin of the Bouchat
being entirely bare, while that of the Grenetière is well wooded.[192]
Observations in the same valleys, considered with reference to the
seasons, show the following pluviometric results:
FOR LA GRENETIÈRE.
February, 1852, 42.2 millimètres precipitation.
November, " 23.8 " "
January, 1853, 35.4 " "
-----
Total, 106.4 in three cold months.
September, 1851, 27.1 millimètres precipitation.
May, 1852, 20.9 " "
June, " 56.3 " "
July, " 22.8 " "
September, " 22.8 " "
-----
Total, 149.9 in five warm months.
FOR LE BOUCHAT.
February, 1852, 51.3 millimètres precipitation.
November, " 36.6 " "
January, 1853, 92.0 " "
-----
Total, 179.9 in three cold months.
September, 1851, 43.8 millimètres precipitation.
May, 1852, 13.2 " "
June, " 55.5 " "
July, " 19.5 " "
September, " 26.5 " "
-----
Total, 158.5 in five warm months.
These observations, so far as they go, seem to show that more rain falls
in cleared than in wooded countries, but this result is so contrary to
what has been generally accepted as a theoretical conclusion, that
further experiment is required to determine the question.
Becquerel--whose treatise on the climatic effects of the destruction of
the forest is the fullest general discussion of that subject known to
me--does not examine this particular point, and as, in the summary of
the results of his investigations, he does not ascribe to the forest any
influence upon precipitation, the presumption is that he rejects the
doctrine of its importance as an agent in producing the fall of rain.
The effect of the forest on precipitation, then, is not entirely free
from doubt, and we cannot positively affirm that the total annual
quantity of rain is diminished or increased by the destruction of the
woods, though both theoretical considerations and the balance of
testimony strongly favor the opinion that more rain falls in wooded than
in open countries. One important conclusion, at least, upon the
meteorological influence of forests is certain and undisputed: the
proposition, namely, that, within their own limits, and near their own
borders, they maintain a more uniform degree of humidity in the
atmosphere than is observed in cleared grounds. Scarcely less can it be
questioned that they promote the frequency of showers, and, if they do
not augment the amount of precipitation, they equalize its distribution
through the different seasons.
_Influence of the Forest on the Humidity of the Soil._
I have hitherto confined myself to the influence of the forest on
meteorological conditions, a subject, as has been seen, full of
difficulty and uncertainty. Its comparative effects on the temperature,
the humidity, the texture and consistence, the configuration and
distribution of the mould or arable soil, and, very often, of the
mineral strata below, and on the permanence and regularity of springs
and greater superficial watercourses, are much less disputable as well
as more easily estimated, and much more important, than its possible
value as a cause of strictly climatic equilibrium or disturbance.
The action of the forest on the earth is chiefly mechanical, but the
organic process of abstraction of water by its roots affects the
quantity of that fluid contained in the vegetable mould, and in the
mineral strata near the surface, and, consequently, the consistency of
the soil. In treating of the effects of trees on the moisture of the
atmosphere, I have said that the forest, by interposing a canopy between
the sky and the ground, and by covering the surface with a thick mantle
of fallen leaves, at once obstructed insolation and prevented the
radiation of heat from the earth. These influences go far to balance
each other; but familiar observation shows that, in summer, the forest
soil is not raised to so high a temperature as open grounds exposed to
irradiation. For this reason, and in consequence of the mechanical
resistance opposed by the bed of dead leaves to the escape of moisture,
we should expect that, except after recent rains, the superficial strata
of woodland soil would be more humid than that of cleared land. This
agrees with experience. The soil of the forest is always moist, except
in the extremest droughts, and it is exceedingly rare that a primitive
wood suffers from want of humidity. How far this accumulation of water
affects the condition of neighboring grounds by lateral infiltration, we
do not know, but we shall see, in a subsequent chapter, that water is
conveyed to great distances by this process, and we may hence infer that
the influence in question is an important one.
_Influence of the Forest on the Flow of Springs._
It is well established that the protection afforded by the forest
against the escape of moisture from its soil, insures the permanence and
regularity of natural springs, not only within the limits of the wood,
but at some distance beyond its borders, and thus contributes to the
supply of an element essential to both vegetable and animal life. As the
forests are destroyed, the springs which flowed from the woods, and,
consequently, the greater watercourses fed by them, diminish both in
number and in volume. This fact is so familiar throughout the American
States and the British Provinces, that there are few old residents of
the interior of those districts who are not able to testify to its truth
as a matter of personal observation. My own recollection suggests to me
many instances of this sort, and I remember one case where a small
mountain spring, which disappeared soon after the clearing of the ground
where it rose, was recovered about ten or twelve years ago, by simply
allowing the bushes and young trees to grow up on a rocky knoll, not
more than half an acre in extent, immediately above it, and has since
continued to flow uninterruptedly. The uplands in the Atlantic States
formerly abounded in sources and rills, but in many parts of those
States which have been cleared for above a generation or two, the hill
pastures now suffer severely from drought, and in dry seasons no longer
afford either water or herbage for cattle.
Foissac, indeed, quotes from the elder Pliny (_Nat. Hist._, xxxi, c. 30)
a passage affirming that the felling of the woods gives rise to springs
which did not exist before because the water of the soil was absorbed by
the trees; and the same meteorologist declares, as I observed in
treating of the effect of the forest on atmospheric humidity, that the
planting of trees tends to drain marshy ground, because the roots absorb
more water than falls from the air. But Pliny's statement rests on very
doubtful authority, and Foissac cites no evidence in support of his own
proposition.[193] In the American States, it is always observed that
clearing the ground not only causes running springs to disappear, but
dries up the stagnant pools and the spongy soils of the low grounds. The
first roads in those States ran along the ridges, when practicable,
because there only was the earth dry enough to allow of their
construction, and, for the same reason, the cabins of the first settlers
were perched upon the hills. As the forests have been from time to time
removed, and the face of the earth laid open to the air and sun, the
moisture has been evaporated, and the removal of the highways and of
human habitations from the bleak hills to the sheltered valleys, is one
of the most agreeable among the many improvements which later
generations have witnessed in the interior of New England and the other
Northern States.
Almost every treatise on the economy of the forest adduces numerous
facts in support of the doctrine that the clearing of the woods tends to
diminish the flow of springs and the humidity of the soil, and it might
seem unnecessary to bring forward further evidence on this point.[194]
But the subject is of too much practical importance and of too great
philosophical interest to be summarily disposed of; and it ought
particularly to be noticed that there is at least one case--that of some
loose soils which, when bared of wood, very rapidly absorb and transmit
to lower strata the water they receive from the atmosphere, as argued by
Vallès[195]--where the removal of the forest may increase the flow of
springs at levels below it, by exposing to the rain and melted snow a
surface more bibulous, and at the same time less retentive, than its
original covering. Under such circumstances, the water of precipitation,
which had formerly flowed off without penetrating through the
superficial layers of leaves upon the ground--as, in very heavy showers,
it sometimes does--or been absorbed by the vegetable mould and retained
until it was evaporated, might descend through porous earth until it
meets an impermeable stratum, and then be conducted along it, until,
finally, at the outcropping of this stratum, it bursts from a hillside
as a running spring. But such instances are doubtless too rare to form a
frequent or an important exception to the general law, because it is
only under very uncommon circumstances that rain water runs off over the
surface of forest ground instead of sinking into it, and very rarely the
case that such a soil as has just been supposed is covered by a layer of
vegetable earth thick enough to retain, until it is evaporated, all the
rain that falls upon it, without imparting any water to the strata below
it.
If we look at the point under discussion as purely a question of fact,
to be determined by positive evidence and not by argument, the
observations of Boussingault are, both in the circumstances they detail,
and in the weight of authority to be attached to the testimony, among
the most important yet recorded. They are embodied in the fourth section
of the twentieth chapter of that writer's _Économie Rurale_, and I have
already referred to them on page 191 for another purpose. The interest
of the question will justify me in giving, in Boussingault's own words,
the facts and some of the remarks with which he accompanies the details
of them: "In many localities," he observes,[196] "it has been thought
that, within a certain number of years, a sensible diminution has been
perceived in the volume of water of streams utilized as a motive power;
at other points, there are grounds for believing that rivers have become
shallower, and the increasing breadth of the belt of pebbles along their
banks seems to prove the loss of a part of their water; and, finally,
abundant springs have almost dried up. These observations have been
principally made in valleys bounded by high mountains, and it is thought
to have been noticed that this diminution of the waters has immediately
followed the epoch when the inhabitants have begun to destroy,
unsparingly, the woods which were spread over the face of the land.
"These facts would indicate that, where clearings have been made,
it rains less than formerly, and this is the generally received
opinion. * * * But while the facts I have stated have been established,
it has been observed, at the same time, that, since the clearing of the
mountains, the rivers and the torrents, which seemed to have lost a part
of their water, sometimes suddenly swell, and that, occasionally, to a
degree which causes great disasters. Besides, after violent storms,
springs which had become almost exhausted have been observed to burst
out with impetuosity, and soon after to dry up again. These latter
observations, it will be easily conceived, warn us not to admit hastily
the common opinion that the felling of the woods lessens the quantity of
rain; for not only is it very possible that the quantity of rain has not
changed, but the mean volume of running water may have remained the
same, in spite of the appearance of drought presented by the rivers and
springs, at certain periods of the year. Perhaps the only difference
would be that the flow of the same quantity of water becomes more
irregular in consequence of clearing. For instance: if the low water of
the Rhone during one part of the year were exactly compensated by a
sufficient number of floods, it would follow that this river would
convey to the Mediterranean the same volume of water which it carried to
that sea in ancient times, before the period when the countries near its
source were stripped of their woods, and when, probably, its mean depth
was not subject to so great variations as in our days. If this were so,
the forests would have this value--that of regulating, of economizing in
a certain sort, the drainage of the rain water.
"If running streams really become rarer in proportion as clearing is
extended, it follows either that the rain is less abundant, or that
evaporation is greatly favored by a surface which is no longer protected
by trees against the rays of the sun and the wind. These two causes,
acting in the same direction, must often be cumulative in their effects,
and before we attempt to fix the value of each, it is proper to inquire
whether it is an established fact that running waters diminish on the
surface of a country in which extensive clearing is going on; in a word,
to examine whether an apparent fact has not been mistaken for a real
one. And here lies the practical point of the question; for if it is
once established that clearing diminishes the volume of streams, it is
less important to know to what special cause this effect is due. * * * I
shall attach no value except to facts which have taken place under the
eye of man, as it is the influence of his labors on the meteorological
condition of the atmosphere which I propose to estimate. What I am about
to detail has been observed particularly in America, but I shall
endeavor to establish, that what I believe to be true of America would
be equally so for any other continent.
"One of the most interesting parts of Venezuela is, no doubt, the valley
of Aragua. Situated at a short distance from the coast, and endowed,
from its elevation, with various climates and a soil of unexampled
fertility, its agriculture embraces at once the crops suited to tropical
regions and to Europe. Wheat succeeds well on the heights of Victoria.
Bounded on the north by the coast chain, on the south by a system of
mountains connected with the Llanos, the valley is shut in on the east
and the west by lines of hills which completely close it. In consequence
of this singular configuration, the rivers which rise within it, having
no outlet to the ocean, form, by their union, the beautiful Lake of
Tacarigua or Valencia. This lake, according to Humboldt, is larger than
that of Neufchâtel; it is at an elevation of 439 mètres [= 1,460 English
feet] above the sea, and its greatest length does not exceed two leagues
and a half [= seven English miles].
"At the time of Humboldt's visit to the valley of Aragua, the
inhabitants were struck by the gradual diminution which the lake had
been undergoing for thirty years. In fact, by comparing the descriptions
given by historians with its actual condition, even making large
allowance for exaggeration, it was easy to see that the level was
considerably depressed. The facts spoke for themselves. Oviedo, who,
toward the close of the sixteenth century, had often traversed the
valley of Aragua, says positively that New Valencia was founded, in
1555, at half a league from the Lake of Tacarigua; in 1800, Humboldt
found this city 5,260 mètres [= 3-1/3 English miles] from the shore.
"The aspect of the soil furnished new proofs. Many hillocks on the plain
retain the name of islands, which they more justly bore when they were
surrounded by water. The ground laid bare by the retreat of the lake was
converted into admirable plantations of cotton, bananas, and sugar cane;
and buildings erected near the lake showed the sinking of the water from
year to year. In 1796, new islands made their appearance. An important
military point, a fortress built in 1740 on the island of Cabrera, was
now on a peninsula; and, finally, on two granitic islands, those of Cura
and Cabo Blanco, Humboldt observed among the shrubs, some mètres above
the water, fine sand filled with helicites.
"These clear and positive facts suggested numerous explanations, all
assuming a subterranean outlet, which permitted the discharge of the
water to the ocean. Humboldt disposed of these hypotheses, and, after a
careful examination of the locality, the distinguished traveller did not
hesitate to ascribe the diminution of the waters of the lake to the
numerous clearings which had been made in the valley of Aragua within
half a century. * * *
"In 1800, the valley of Aragua possessed a population as dense as that
of any of the best-peopled parts of France. * * * Such was the
prosperous condition of this fine country when Humboldt occupied the
Hacienda de Cura.
"Twenty-two years later, I explored the valley of Aragua, fixing my
residence in the little town of Maracay. For some years previous, the
inhabitants had observed that the waters of the lake were no longer
retiring, but, on the contrary, were sensibly rising. Grounds, not long
before occupied by plantations, were submerged. The islands of Nuevas
Aparecidas, which appeared above the surface in 1796, had again become
shoals dangerous to navigation. Cabrera, a tongue of land on the north
side of the valley, was so narrow that the least rise of the water
completely inundated it. A protracted north wind sufficed to flood the
road between Maracay and New Valencia. The fears which the inhabitants
of the shores had so long entertained were reversed. * * * Those who had
explained the diminution of the lake by the supposition of subterranean
channels were suspected of blocking them up, to prove themselves in the
right.
"During the twenty-two years which had elapsed, important political
events had occurred. Venezuela no longer belonged to Spain. The peaceful
valley of Aragua had been the theatre of bloody struggles, and a war of
extermination had desolated these smiling lands and decimated their
population. At the first cry of independence a great number of slaves
found their liberty by enlisting under the banners of the new republic;
the great plantations were abandoned, and the forest, which in the
tropics so rapidly encroaches, had soon recovered a large proportion of
the soil which man had wrested from it by more than a century of
constant and painful labor.
"At the time of the growing prosperity of the valley of Aragua, the
principal affluents of the lake were diverted, to serve for irrigation,
and the rivers were dry for more than six months of the year. At the
period of my visit, their waters, no longer employed, flowed freely."
Boussingault proceeds to state that two lakes near Ubate in New Granada,
at an elevation of 2,562 mètres (= 8,500 English feet), where there is a
constant temperature of 14° to 16° centigrade [= 57°, 61° Fahrenheit],
had formed but one, a century before his visit; that the waters were
gradually retiring, and the plantations extending over the abandoned
bed; that, by inquiry of old hunters and by examination of parish
records, he found that extensive clearings had been made and were still
going on.
He found, also, that the length of the Lake of Fuquené, in the same
valley, had, within two centuries, been reduced from ten leagues to one
and a half, its breadth from three leagues to one. At the former period,
timber was abundant, and the neighboring mountains were covered, to a
certain height, with American oaks, laurels, and other trees of
indigenous species; but at the time of his visit the mountains had been
almost entirely stripped of their wood, chiefly to furnish fuel for
salt-works. Our author adds that other cases, similar to those already
detailed, might be cited, and he proceeds to show, by several examples,
that the waters of other lakes in the same regions, where the valleys
had always been bare of wood, or where the forests had not been
disturbed, had undergone no change of level.
Boussingault further maintains that the lakes of Switzerland have
sustained a depression of level since the too prevalent destruction of
the woods, and arrives at the general conclusion, that, "in countries
where great clearings have been made, there has most probably been a
diminution in the living waters which flow upon the surface of the
ground." This conclusion he further supports by two examples: one, where
a fine spring, at the foot of a wooded mountain in the Island of
Ascension, dried up when the mountain was cleared, but reappeared when
the wood was replanted; the other at Marmato, in the province of
Popayan, where the streams employed to drive machinery were much
diminished in volume, within two years after the clearing of the heights
from which they derived their supplies. This latter is an interesting
case, because, although the rain gauges, established as soon as the
decrease of water began to excite alarm, showed a greater fall of rain
for the second year of observation than the first, yet there was no
appreciable increase in the flow of the mill streams. From these cases,
the distinguished physicist infers that very restricted local clearings
may diminish and even suppress springs and brooks, without any reduction
in the total quantity of rain.
It will have been noticed that these observations, with the exception of
the last two cases, do not bear directly upon the question of the
diminution of springs by clearings, but they logically infer it from the
subsidence of the natural reservoirs which springs once filled. There
is, however, no want of positive evidence on this subject.
Marschand cites the following instances: "Before the felling of the
woods, within the last few years, in the valley of the Soulce, the
Combe-ès-Mounin and the Little Valley, the Sorne furnished a regular
and sufficient supply of water for the iron works of Unterwyl, which was
almost unaffected by drought or by heavy rains. The Sorne has now become
a torrent, every shower occasions a flood, and after a few days of fine
weather, the current falls so low that it has been necessary to change
the water wheels, because those of the old construction are no longer
able to drive the machinery, and at last to introduce a steam engine to
prevent the stoppage of the works for want of water.
"When the factory of St. Ursanne was established, the river that
furnished its power was abundant, long known and tried, and had, from
time immemorial, sufficed for the machinery of a previous factory.
Afterward, the woods near its sources were cut. The supply of water fell
off in consequence, the factory wanted water for half the year, and was
at last obliged to stop altogether.
"The spring of Combefoulat, in the commune of Seleate, was well known as
one of the best in the country; it was remarkably abundant and
sufficient, in spite of the severest droughts, to supply all the
fountains of the town; but, as soon as considerable forests were felled
in Combe-de-pré Martin and in the valley of Combefoulat, the famous
spring which lies below these woods has become a mere thread of water,
and disappears altogether in times of drought.
"The spring of Varieux, which formerly supplied the castle of Pruntrut,
lost more than half its water after the clearing of Varieux and
Rongeoles. These woods have been replanted, the young trees are growing
well, and with the woods, the waters of the spring are increasing.
"The Dog Spring between Pruntrut and Bressancourt has entirely vanished
since the surrounding forests grounds were brought under cultivation.
"The Wolf Spring, in the commune of Soubey, furnishes a remarkable
example of the influence of the woods upon fountains. A few years ago
this spring did not exist. At the place where it now rises, a small
thread of water was observed after very long rains, but the stream
disappeared with the rain. The spot is in the middle of a very steep
pasture inclining to the south. Eighty years ago, the owner of the land,
perceiving that young firs were shooting up in the upper part of it,
determined to let them grow, and they soon formed a flourishing grove.
As soon as they were well grown, a fine spring appeared in place of the
occasional rill, and furnished abundant water in the longest droughts.
For forty or fifty years, this spring was considered the best in the
Clos du Doubs. A few years since, the grove was felled, and the ground
turned again to a pasture. The spring disappeared with the wood, and is
now as dry as it was ninety years ago."[197]
"The influence of the forest on springs," says Hummel, "is strikingly
shown by an instance at Heilbronn. The woods on the hills surrounding
the town are cut in regular succession every twentieth year. As the
annual cuttings approach a certain point, the springs yield less water,
some of them none at all; but as the young growth shoots up, they now
more and more freely, and at length bubble up again in all their
original abundance."[198]
Piper states the following case: "Within about half a mile of my
residence there is a pond upon which mills have been standing for a long
time, dating back, I believe, to the first settlement of the town. These
have been kept in constant operation until within some twenty or thirty
years, when the supply of water began to fail. The pond owes its
existence to a stream which has its source in the hills which stretch
some miles to the south. Within the time mentioned, these hills, which
were clothed with a dense forest, have been almost entirely stripped of
trees; and to the wonder and loss of the mill owners, the water in the
pond has failed, except in the season of freshets; and, what was never
heard of before, the stream itself has been entirely dry. Within the
last ten years a new growth of wood has sprung up on most of the land
formerly occupied by the old forest; and now the water runs through the
year, notwithstanding the great droughts of the last few years, going
back from 1856."
Dr. Piper quotes from a letter of William C. Bryant the following
remarks: "It is a common observation that our summers are become drier,
and our streams smaller. Take the Cuyahoga as an illustration. Fifty
years ago large barges loaded with goods went up and down that river,
and one of the vessels engaged in the battle of Lake Erie, in which the
gallant Perry was victorious, was built at Old Portage, six miles north
of Albion, and floated down to the lake. Now, in an ordinary stage of
the water, a canoe or skiff can hardly pass down the stream. Many a boat
of fifty tons burden has been built and loaded in the Tuscarawas, at New
Portage, and sailed to New Orleans without breaking bulk. Now, the river
hardly affords a supply of water at New Portage for the canal. The same
may be said of other streams--they are drying up. And from the same
cause--the destruction of our forests--our summers are growing drier,
and our winters colder."[199]
No observer has more carefully studied the influence of the forest upon
the flow of the waters, or reasoned more ably on the ascertained
phenomena than Cantegril. The facts presented in the following case,
communicated by him to the _Ami des Sciences_ for December, 1859, are as
nearly conclusive as any single instance well can be:
"In the territory of the commune of Labruguière, there is a forest of
1,834 hectares [4,530 acres], known by the name of the Forest of
Montaut, and belonging to that commune. It extends along the northern
slope of the Black Mountains. The soil is granitic, the maximum altitude
1,243 mètres [4,140 feet], and the inclination ranges between 15 and 60
to 100.
"A small current of water, the brook of Caunan, takes its rise in this
forest, and receives the waters of two thirds of its surface. At the
lower extremity of the wood and on the stream are several fulleries,
each requiring a force of eight horse-power to drive the water wheels
which work the stampers. The commune of Labruguière had been for a long
time famous for its opposition to forest laws. Trespasses and abuses of
the right of pasturage had converted the wood into an immense waste, so
that this vast property now scarcely sufficed to pay the expense of
protecting it, and to furnish the inhabitants with a meagre supply of
fuel. While the forest was thus ruined, and the soil thus bared, the
water, after every abundant rain, made an eruption into the valley,
brought down a great quantity of pebbles which still clog the current of
the Caunan. The violence of the floods was sometimes such that they were
obliged to stop the machinery for some time. During the summer another
inconvenience was felt. If the dry weather continued a little longer
than usual, the delivery of water became insignificant. Each fullery
could for the most part only employ a single set of stampers, and it was
not unusual to see the work entirely suspended.
"After 1840, the municipal authority succeeded in enlightening the
population as to their true interests. Protected by a more watchful
supervision, aided by well-managed replantation, the forest has
continued to improve to the present day. In proportion to the
restoration of the forest, the condition of the manufactories has become
less and less precarious, and the action of the water is completely
modified. For example, there are, no longer, sudden and violent floods
which make it necessary to stop the machinery. There is no increase in
the delivery until six or eight hours after the beginning of the rain;
the floods follow a regular progression till they reach their maximum,
and decrease in the same manner. Finally, the fulleries are no longer
forced to suspend work in summer; the water is always sufficiently
abundant to allow the employment of two sets of stampers at least, and
often even of three.
"This example is remarkable in this respect, that, all other
circumstances having remained the same, the changes in the action of the
stream can be attributed only to the restoration of the forest--changes
which may be thus summed up: diminution of flood water during
rains--increase of delivery at other seasons."
_The Forest in Winter._
To estimate rightly the importance of the forest as a natural apparatus
for accumulating the water that falls upon the surface and transmitting
it to the subjacent strata, we must compare the condition and properties
of its soil with those of cleared and cultivated earth, and examine the
consequently different action of these soils at different seasons of the
year. The disparity between them is greatest in climates where, as in
the Northern American States and in the North of Europe, the open ground
freezes and remains impervious to water during a considerable part of
the winter; though, even in climates where the earth does not freeze at
all, the woods have still an important influence of the same character.
The difference is yet greater in countries which have regular wet and
dry seasons, rain being very frequent in the former period, while, in
the latter, it scarcely occurs at all. These countries lie chiefly in or
near the tropics, but they are not wanting in higher latitudes; for a
large part of Asiatic and even of European Turkey is almost wholly
deprived of summer rains. In the principal regions occupied by European
cultivation, and where alone the questions discussed in this volume are
recognized as having, at present, any practical importance, rain falls
at all seasons, and it is to these regions that, on this point as well
as others, I chiefly confine my attention.
The influence of the forest upon the waters of the earth has been more
studied in France than in any other part of the civilized world, because
that country has, in recent times, suffered most severely from the
destruction of the woods. But in the southern provinces of that empire,
where the evils resulting from this cause are most sensibly felt, the
winters are not attended with much frost, while, in Northern Europe,
where the winters are rigorous enough to freeze the ground to the depth
of some inches, or even feet, a humid atmosphere and frequent summer
rains prevent the drying up of the springs observed in southern
latitudes when the woods are gone. For these reasons, the specific
character of the forest, as a winter reservoir of moisture in countries
with a cold and dry atmosphere, has not attracted so much attention in
France and Northern Europe as it deserves in the United States, where an
excessive climate renders that function of the woods more important.
In New England, irregular as the climate is, the first autumnal snows
usually fall before the ground is frozen at all, or when the frost
extends at most to the depth of only a few inches. In the woods,
especially those situated upon the elevated ridges which supply the
natural irrigation of the soil and feed the perennial fountains and
streams, the ground remains covered with snow during the winter; for the
trees protect the snow from blowing from the general surface into the
depressions, and new accessions are received before the covering
deposited by the first fall is melted. Snow is of a color unfavorable
for radiation, but, even when it is of considerable thickness, it is not
wholly impervious to the rays of the sun, and for this reason, as well
as from the warmth of lower strata, the frozen crust, if one has been
formed, is soon thawed, and does not again fall below the freezing point
during the winter.
The snow in contact with the earth now begins to melt, with greater or
less rapidity, according to the relative temperature of the earth and
the air, while the water resulting from its dissolution is imbibed by
the vegetable mould, and carried off by infiltration so fast that both
the snow and the layers of leaves in contact with it often seem
comparatively dry, when, in fact, the under surface of the former is in
a state of perpetual thaw. No doubt a certain proportion of the snow is
returned to the atmosphere by direct evaporation, but in the woods it is
partially protected from the action of the sun, and as very little water
runs off in the winter by superficial watercourses, except in rare cases
of sudden thaw, there can be no question that much the greater part of
the snow deposited in the forest is slowly melted and absorbed by the
earth.
The quantity of snow that falls in extensive forests, far from the open
country, has seldom been ascertained by direct observation, because
there are few meteorological stations in such situations. In the
Northeastern border States of the American Union, the ground in the deep
woods is covered with snow four or five months, and the proportion of
water which falls in snow does not exceed one fifth of the total
precipitation for the year.[200] Although, in the open grounds, snow and
ice are evaporated with great rapidity in clear weather, even when the
thermometer stands far below the freezing point, the surface of the snow
in the woods does not indicate much loss in this way. Very small
deposits of snowflakes remain unevaporated in the forest, for many days
after snow let fall at the same time in the cleared field has
disappeared without either a thaw to melt it or a wind powerful enough
to drift it away. Even when bared of their leaves, the trees of a wood
obstruct, in an important degree, both the direct action of the sun's
rays on the snow, and the movement of drying and thawing winds.
Dr. Piper records the following observations: "A body of snow, one foot
in depth, and sixteen feet square, was protected from the wind by a
tight board fence about five feet high, while another body of snow, much
more sheltered from the sun than the first, six feet in depth, and about
sixteen feet square, was fully exposed to the wind. When the thaw came
on, which lasted about a fortnight, the larger body of snow was entirely
dissolved in less than a week, while the smaller body was not wholly
gone at the end of the second week.
"Equal quantities of snow were placed in vessels of the same kind and
capacity, the temperature of the air being seventy degrees. In the one
case, a constant current of air was kept passing over the open vessel,
while the other was protected by a cover. The snow in the first was
dissolved in sixteen minutes, while the latter had a small unthawed
proportion remaining at the end of eighty-five minutes."[201]
The snow in the woods is protected in the same way, though not literally
to the same extent as by the fence in one of these cases and the cover
in the other. Little of the winter precipitation, therefore, is lost by
evaporation, and as it slowly melts at bottom it is absorbed by the
earth, and but a very small quantity of water runs off from the surface.
The immense importance of the forest, as a reservoir of this stock of
moisture, becomes apparent, when we consider that a large proportion of
the summer rain either flows into the valleys and the rivers, because it
falls faster than the ground can imbibe it; or, if absorbed by the warm
superficial strata, is evaporated from them without sinking deep enough
to reach wells and springs, which, of course, depend very much on winter
rains and snows for their entire supply. This observation, though
specially true of cleared and cultivated grounds, is not wholly
inapplicable to the forest, particularly when, as is too often the case
in Europe, the underwood and the decaying leaves are removed.
The general effect of the forest in cold climates is to assimilate the
winter state of the ground to that of wooded regions under softer skies;
and it is a circumstance well worth noting, that in Southern Europe,
where nature has denied to the earth a warm winter-garment of flocculent
snow, she has, by one of those compensations in which her empire is so
rich, clothed the hillsides with umbrella pines, ilexes, cork oaks, and
other trees of persistent foliage, whose evergreen leaves afford to the
soil a protection analogous to that which it derives from snow in more
northern climates.
The water imbibed by the soil in winter sinks until it meets a more or
less impermeable, or a saturated stratum, and then, by unseen conduits,
slowly finds its way to the channels of springs, or oozes out of the
ground in drops which unite in rills, and so all is conveyed to the
larger streams, and by them finally to the sea. The water, in
percolating through the vegetable and mineral layers, acquires their
temperature, and is chemically affected by their action, but it carries
very little matter in mechanical suspension.
The process I have described is a slow one, and the supply of moisture
derived from the snow, augmented by the rains of the following seasons,
keeps the forest ground, where the surface is level or but moderately
inclined, in a state of saturation through almost the whole year. The
rivers fed by springs and shaded by woods are comparatively uniform in
volume, in temperature, and in chemical composition. Their banks are
little abraded, nor are their courses much obstructed by fallen timber,
or by earth and gravel washed down from the highlands. Their channels
are subject only to slow and gradual changes, and they carry down to the
lakes and the sea no accumulation of sand or silt to fill up their
outlets, and, by raising their beds, to force them to spread over the
low grounds near their mouth.[202]
In this state of things, destructive tendencies of all sorts are
arrested or compensated, and tree, bird, beast, and fish, alike, find a
constant uniformity of condition most favorable to the regular and
harmonious coexistence of them all.
_General Consequences of the Destruction of the Forest._
With the disappearance of the forest, all is changed. At one season, the
earth parts with its warmth by radiation to an open sky--receives, at
another, an immoderate heat from the unobstructed rays of the sun. Hence
the climate becomes excessive, and the soil is alternately parched by
the fervors of summer, and seared by the rigors of winter. Bleak winds
sweep unresisted over its surface, drift away the snow that sheltered it
from the frost, and dry up its scanty moisture. The precipitation
becomes as regular as the temperature; the melting snows and vernal
rains, no longer absorbed by a loose and bibulous vegetable mould, rush
over the frozen surface, and pour down the valleys seaward, instead of
filling a retentive bed of absorbent earth, and storing up a supply of
moisture to feed perennial springs. The soil is bared of its covering of
leaves, broken and loosened by the plough, deprived of the fibrous
rootlets which held it together, dried and pulverized by sun and wind,
and at last exhausted by new combinations. The face of the earth is no
longer a sponge, but a dust heap, and the floods which the waters of the
sky pour over it hurry swiftly along its slopes, carrying in suspension
vast quantities of earthy particles which increase the abrading power
and mechanical force of the current, and, augmented by the sand and
gravel of falling banks, fill the beds of the streams, divert them into
new channels and obstruct their outlets. The rivulets, wanting their
former regularity of supply and deprived of the protecting shade of the
woods, are heated, evaporated, and thus reduced in their summer
currents, but swollen to raging torrents in autumn and in spring. From
these causes, there is a constant degradation of the uplands, and a
consequent elevation of the beds of watercourses and of lakes by the
deposition of the mineral and vegetable matter carried down by the
waters. The channels of great rivers become unnavigable, their estuaries
are choked up, and harbors which once sheltered large navies are shoaled
by dangerous sandbars. The earth, stripped of its vegetable glebe, grows
less and less productive, and, consequently, less able to protect itself
by weaving a new network of roots to bind its particles together, a new
carpeting of turf to shield it from wind and sun and scouring rain.
Gradually it becomes altogether barren. The washing of the soil from the
mountains leaves bare ridges of sterile rock, and the rich organic mould
which covered them, now swept down into the dank low grounds, promotes a
luxuriance of aquatic vegetation that breeds fever, and more insidious
forms of mortal disease, by its decay, and thus the earth is rendered no
longer fit for the habitation of man.[203]
To the general truth of this sad picture there are many exceptions, even
in countries of excessive climates. Some of these are due to favorable
conditions of surface, of geological structure, and of the distribution
of rain; in many others, the evil consequences of man's improvidence
have not yet been experienced, only because a sufficient time has not
elapsed, since the felling of the forest, to allow them to develop
themselves. But the vengeance of nature for the violation of her
harmonies, though slow, is sure, and the gradual deterioration of soil
and climate in such exceptional regions is as certain to result from the
destruction of the woods as is any natural effect to follow its cause.
In the vast farrago of crudities which the elder Pliny's ambition of
encyclopædic attainment and his ready credulity have gathered together,
we meet some judicious observations. Among these we must reckon the
remark with which he accompanies his extraordinary statement respecting
the prevention of springs by the growth of forest trees, though, as is
usual with him, his philosophy is wrong. "Destructive torrents are
generally formed when hills are stripped of the trees which formerly
confined and absorbed the rains." The absorption here referred to is not
that of the soil, but of the roots, which, Pliny supposed, drank up the
water to feed the growth of the trees.
Although this particular evil effect of too extensive clearing was so
early noticed, the lesson seems to have been soon forgotten. The
legislation of the Middle Ages in Europe is full of absurd provisions
concerning the forests, which sovereigns sometimes destroyed because
they furnished a retreat for rebels and robbers, sometimes protected
because they were necessary to breed stags and boars for the chase, and
sometimes spared with the more enlightened view of securing a supply of
timber and of fuel to future generations.[204] It was reserved to later
ages to appreciate their geographical importance, and it is only in very
recent times, only in a few European countries, that the too general
felling of the woods has been recognized as the most destructive among
the many causes of the physical deterioration of the earth.
_Condition of the Forest, and its Literature in different Countries._
The literature of the forest, which in England and America has not yet
become sufficiently extensive to be known as a special branch of
authorship, counts its thousands of volumes in Germany, Italy, and
France. It is in the latter country, perhaps, that the relations of the
woods to the regular drainage of the soil, and especially to the
permanence of the natural configuration of terrestrial surface, have
been most thoroughly investigated. On the other hand, the purely
economical aspects of sylviculture have been most satisfactorily
expounded, and that art has been most philosophically discussed, and
most skilfully and successfully practised, in Germany.
The eminence of Italian theoretical hydrographers and the great ability
of Italian hydraulic engineers are well known, but the specific
geographical importance of the woods has not been so clearly recognized
in Italy as in the states bordering it on the north and west. It is true
that the face of nature has been as completely revolutionized by man,
and that the action of torrents has created as wide and as hopeless
devastation in that country as in France; but in the French Empire the
desolation produced by clearing the forests is more recent,[205] has
been more suddenly effected, and, therefore, excites a livelier and more
general interest than in Italy, where public opinion does not so readily
connect the effect with its true cause. Italy, too, from ancient habit,
employs little wood in architectural construction; for generations she
has maintained no military or commercial marine large enough to require
exhaustive quantities of timber,[206] and the mildness of her climate
makes small demands on the woods for fuel. Besides these circumstances,
it must be remembered that the sciences of observation did not become
knowledges of practical application till after the mischief was already
mainly done and even forgotten in Alpine Italy, while its evils were
just beginning to be sensibly felt in France when the claims of natural
philosophy as a liberal study were first acknowledged in modern Europe.
The former political condition of the Italian Peninsula would have
effectually prevented the adoption of a general system of forest
economy, however clearly the importance of a wise administration of this
great public interest might have been understood. The woods which
controlled and regulated the flow of the river sources were very often
in one jurisdiction, the plains to be irrigated, or to be inundated by
floods and desolated by torrents, in another. Concert of action on such
a subject between a multitude of jealous petty sovereignties was
obviously impossible, and nothing but the union of all the Italian
states under a single government can render practicable the
establishment of such arrangements for the conservation and restoration
of the forests and the regulation of the flow of the waters as are
necessary for the full development of the yet unexhausted resources of
that fairest of lands, and even for the permanent maintenance of the
present condition of its physical geography.
The denudation of the Central and Southern Apennines and of the Italian
declivity of the Western Alps began at a period of unknown antiquity,
but it does not seem to have been carried to a very dangerous length
until the foreign conquests and extended commerce of Rome created a
greatly increased demand for wood for the construction of ships and for
military material. The Eastern Alps, the Western Apennines, and the
Maritime Alps retained their forests much later; but even here the want
of wood, and the injury to the plains and the navigation of the rivers
by sediment brought down by the torrents, led to some legislation for
the protection of the forests, by the Republic of Venice in the
fifteenth century, by that of Genoa as early at least as the
seventeenth; and Marschand states that the latter Government passed laws
requiring the proprietors of mountain lands to replant the woods. These,
however, do not seem to have been effectually enforced. It is very
common in Italy to ascribe to the French occupation under the first
Empire all the improvements, and all the abuses of recent times,
according to the political sympathies of the individual; and the French
are often said to have prostrated every forest which has disappeared
within a century.[207] But, however this may be, no energetic system of
repression or restoration was adopted by any of the Italian states after
the downfall of the Empire, and the taxes on forest property in some of
them were so burdensome that rural municipalities sometimes proposed to
cede their common woods to the Government, without any other
compensation than the remission of the taxes imposed on forest
lands.[208] Under such circumstances, woodlands would soon become
disafforested, and where facilities of transportation and a good demand
for timber have increased the inducements to fell it, as upon the
borders of the Mediterranean, the destruction of the forest and all the
evils which attend it have gone on at a seriously alarming rate. It has
even been calculated that four tenths of the area of the Ligurian
provinces have been washed away or rendered incapable of cultivation by
the felling of the woods.[209]
The damp and cold climate of England requires the maintenance of
household fires through a large part of the year. Contrivances for
economizing fuel were of later introduction in that country than on the
Continent. The soil, like the sky, was, in general, charged with
humidity; its natural condition was unfavorable for common roads, and
the transportation of so heavy a material as coal, by land, from the
remote counties where alone it was mined in the Middle Ages, was costly
and difficult. For all these reasons, the consumption of wood was large,
and apprehensions of the exhaustion of the forests were excited at an
early period. Legislation there, as elsewhere, proved ineffectual to
protect them, and many authors of the sixteenth century express fears of
serious evils from the wasteful economy of the people in this respect.
Harrison, in his curious chapter "Of Woods and Marishes" in Holinshed's
compilation, complains of the rapid decrease of the forests, and adds:
"Howbeit thus much I dare affirme, that if woods go so fast to decaie in
the next hundred yeere of Grace, as they haue doone and are like to doo
in this, * * * it is to be feared that the fennie bote, broome, turfe,
gall, heath, firze, brakes, whinnes, ling, dies, hassacks, flags, straw,
sedge, réed, rush, and also _seacole_, will be good merchandize euen
in the citie of London, whereunto some of them euen now haue gotten
readie passage, and taken vp their innes in the greatest merchants'
parlours. * * * I would wish that I might liue no longer than to sée
foure things in this land reformed, that is: the want of discipline in
the church: the couetous dealing of most of our merchants in the
preferment of the commodities of other countries, and hinderance of
their owne: the holding of faires and markets vpon the sundaie to be
abolished and referred to the wednesdaies: and that euerie man, in
whatsoeuer part of the champaine soile enioieth fortie acres of land,
and vpwards, after that rate, either by frée deed, copie hold, or fee
farme, might plant one acre of wood, or sowe the same with oke mast,
hasell, béech, and sufficient prouision be made that it may be cherished
and kept. But I feare me that I should then liue too long, and so long,
that I should either be wearie of the world, or the world of me."[210]
Evelyn's "Silva," the first edition of which appeared in 1664, rendered
an extremely important service to the cause of the woods, and there is
no doubt that the ornamental plantations in which England far surpasses
all other countries, are, in some measure, the fruit of Evelyn's
enthusiasm. In England, however, arboriculture, the planting and nursing
of single trees, has, until recently, been better understood than
sylviculture, the sowing and training of the forest. But this latter
branch of rural improvement is now pursued on a very considerable scale,
though, so far as I know, not by the National Government.
_The Influence of the Forest on Inundations._
Besides the climatic question, which I have already sufficiently
discussed, and the obvious inconveniences of a scanty supply of
charcoal, of fuel, and of timber for architectural and naval
construction and for the thousand other uses to which wood is applied in
rural and domestic economy, and in the various industrial processes of
civilized life, the attention of French foresters and public economists
has been specially drawn to three points, namely: the influence of the
forests on the permanence and regular flow of springs or natural
fountains; on inundations by the overflow of rivers; and on the abrasion
of soil and the transportation of earth, gravel, pebbles, and even of
considerable masses of rock, from higher to lower levels, by torrents.
There are, however, connected with this general subject, several other
topics of minor or strictly local interest, or of more uncertain
character, which I shall have occasion more fully to speak of hereafter.
The first of these three principal subjects--the influence of the woods
on springs and other living waters--has been already considered; and if
the facts stated in that discussion are well established, and the
conclusions I have drawn from them are logically sound, it would seem to
follow, as a necessary corollary, that the action of the forest is as
important in diminishing the frequency and violence of river floods, as
in securing the permanence and equability of natural fountains; for any
cause which promotes the absorption and accumulation of the water of
precipitation by the superficial strata of the soil, to be slowly given
out by infiltration and percolation, must, by preventing the rapid flow
of surface water into the natural channels of drainage, tend to check
the sudden rise of rivers, and, consequently, the overflow of their
banks, which constitutes what is called inundation. The mechanical
resistance, too, offered by the trunks of trees and of undergrowth to
the flow of water over the surface, tends sensibly to retard the
rapidity of its descent down declivities, and to divert and divide
streams which may have already accumulated from smaller threads of
water.[211]
Inundations are produced by the insufficiency of the natural channels of
rivers to carry off the waters of their basins as fast as those waters
flow into them. In accordance with the usual economy of nature, we
should presume that she had everywhere provided the means of
discharging, without disturbance of her general arrangements or abnormal
destruction of her products, the precipitation which she sheds upon the
face of the earth. Observation confirms this presumption, at least in
the countries to which I confine my inquiries; for, so far as we know
the primitive conditions of the regions brought under human occupation
within the historical period, it appears that the overflow of river
banks was much less frequent and destructive than at the present day,
or, at least, that rivers rose and fell less suddenly before man had
removed the natural checks to the too rapid drainage of the basins in
which their tributaries originate. The banks of the rivers and smaller
streams in the North American colonies were formerly little abraded by
the currents. Even now the trees come down almost to the water's edge
along the rivers, in the larger forests of the United States, and the
surface of the streams seems liable to no great change in level or in
rapidity of current. A circumstance almost conclusive as to the
regularity of flow in forest rivers, is that they do not form large
sedimentary deposits, at their points of discharge into lakes or larger
streams, such accumulations beginning, or at least advancing far more
rapidly, after the valleys are cleared.
In the Northern United States, although inundations are sometimes
produced in the height of summer by heavy rains, it will be found
generally true that the most rapid rise of the waters, and, of course,
the most destructive "freshets," as they are called in America, are
produced by the sudden dissolution of the snow before the open ground is
thawed in the spring. It frequently happens that a powerful thaw sets in
after a long period of frost, and the snow which had been months in
accumulating is dissolved and carried off in a few hours. When the snow
is deep, it, to use a popular expression, "takes the frost out of the
ground" in the woods, and, if it lies long enough, in the fields also.
But the heaviest snows usually fall after midwinter, and are succeeded
by warm rains or sunshine, which dissolve the snow on the cleared land
before it has had time to act upon the frost-bound soil beneath it. In
this case, the snow in the woods is absorbed as fast as it melts, by the
soil it has protected from freezing, and does not materially contribute
to swell the current of the rivers. If the mild weather, in which great
snowstorms usually occur, does not continue and become a regular thaw,
it is almost sure to be followed by drifting winds, and the inequality
with which they distribute the snow leaves the ridges comparatively
bare, while the depressions are often filled with drifts to the height
of many feet. The knolls become frozen to a great depth; succeeding
partial thaws melt the surface snow, and the water runs down into the
furrows of ploughed fields, and other artificial and natural hollows,
and then often freezes to solid ice. In this state of things, almost the
entire surface of the cleared land is impervious to water, and from the
absence of trees and the general smoothness of the ground, it offers
little mechanical resistance to superficial currents. If, under these
circumstances, warm weather accompanied by rain occurs, the rain and
melted snow are swiftly hurried to the bottom of the valleys and
gathered to raging torrents.
It ought further to be considered that, though the lighter ploughed
soils readily imbibe a great deal of water, yet the grass lands, and all
the heavy and tenacious earths, absorb it in much smaller quantities,
and less rapidly than the vegetable mould of the forest. Pasture,
meadow, and clayey soils, taken together, greatly predominate over the
sandy ploughed fields, in all large agricultural districts, and hence,
even if, in the case we are supposing, the open ground chance to have
been thawed before the melting of the snow which covers it, it is
already saturated with moisture, or very soon becomes so, and, of
course, cannot relieve the pressure by absorbing more water. The
consequence is that the face of the country is suddenly flooded with a
quantity of melted snow and rain equivalent to a fall of six or eight
inches of the latter, or even more. This runs unobstructed to rivers
often still bound with thick ice, and thus inundations of a fearfully
devastating character are produced. The ice bursts, from the hydrostatic
pressure from below, or is violently torn up by the current, and is
swept by the impetuous stream, in large masses and with resistless fury,
against banks, bridges, dams, and mills erected near them. The bark of
the trees along the rivers is often abraded, at a height of many feet
above the ordinary water level, by cakes of floating ice, which are at
last stranded by the receding flood on meadow or ploughland, to delay,
by their chilling influence, the advent of the tardy spring.
The surface of a forest, in its natural condition, can never pour forth
such deluges of water as flow from cultivated soil. Humus, or vegetable
mould, is capable of absorbing almost twice its own weight of water. The
soil in a forest of deciduous foliage is composed of humus, more or less
unmixed, to the depth of several inches, sometimes even of feet, and
this stratum is usually able to imbibe all the water possibly resulting
from the snow which at any one time covers it. But the vegetable mould
does not cease to absorb water when it becomes saturated, for it then
gives off a portion of its moisture to the mineral earth below, and thus
is ready to receive a new supply; and, besides, the bed of leaves not
yet converted to mould takes up and retains a very considerable
proportion of snow water, as well as of rain.
In the warm climates of Southern Europe, as I have already said, the
functions of the forest, so far as the disposal of the water of
precipitation is concerned, are essentially the same at all seasons, and
are analogous to those which it performs in the Northern United States
in summer. Hence, in the former countries, the winter floods have not
the characteristics which mark them in the latter, nor is the
conservative influence of the woods in winter relatively so important,
though it is equally unquestionable.
If the summer floods in the United States are attended with less
pecuniary damage than those of the Loire and other rivers of France, the
Po and its tributaries in Italy, the Emme and her sister torrents which
devastate the valleys of Switzerland, it is partly because the banks of
American rivers are not yet lined with towns, their shores and the
bottoms which skirt them not yet covered with improvements whose cost is
counted by millions, and, consequently, a smaller amount of property is
exposed to injury by inundation. But the comparative exemption of the
American people from the terrible calamities which the overflow of
rivers has brought on some of the fairest portions of the Old World, is,
in a still greater degree, to be ascribed to the fact that, with all our
thoughtless improvidence, we have not yet bared all the sources of our
streams, not yet overthrown all the barriers which nature has erected to
restrain her own destructive energies. Let us be wise in time, and
profit by the errors of our older brethren!
The influence of the forest in preventing inundations has been very
generally recognized, both as a theoretical inference and as a fact of
observation; but Belgrand and his commentator Vallès have deduced an
opposite result from various facts of experience and from scientific
considerations. They contend that the superficial drainage is more
regular from cleared than from wooded ground, and that clearing
diminishes rather than augments the intensity of inundations. Neither of
these conclusions is warranted by their data or their reasoning, and
they rest partly upon facts, which, truly interpreted, are not
inconsistent with the received opinions on these subjects, partly upon
assumptions which are contradicted by experience. Two of these latter
are, first, that the fallen leaves in the forest constitute an
impermeable covering of the soil over, not through, which the water of
rains and of melting snows flows off, and secondly, that the roots of
trees penetrate and choke up the fissures in the rocks, so as to impede
the passage of water through channels which nature has provided for its
descent to lower strata.
As to the first of these, we may appeal to familiar facts within the
personal knowledge of every man acquainted with the operations of sylvan
nature. I have before me a letter from an acute and experienced
observer, containing this paragraph: "I think that rain water does not
ever, except in very trifling quantities, flow over the leaves in the
woods in summer or autumn. Water runs over them only in the spring, when
they are pressed down smoothly and compactly, a state in which they
remain only until they are dry, when shrinkage and the action of the
wind soon roughen the surface so as effectually to stop, by absorption,
all flow of water." I have observed that when a sudden frost succeeds a
thaw at the close of the winter after the snow has principally
disappeared, the water in and between the layers of leaves sometimes
freezes into a solid crust, which allows the flow of water over it. But
this occurs only in depressions and on a very small scale; and the ice
thus formed is so soon dissolved that no sensible effect is produced on
the escape of water from the general surface.
As to the influence of roots upon drainage, I believe there is no doubt
that they, independently of their action as absorbents, mechanically
promote it. Not only does the water of the soil follow them
downward,[212] but their swelling growth powerfully tends to enlarge the
crevices of rock into which they enter; and as the fissures in rocks are
longitudinal, not mere circular orifices, every line of additional width
gained by the growth of roots within them increases the area of the
crevice in proportion to its length. Consequently, the widening of a
fissure to the extent of one inch might give an additional drainage
equal to a square foot of open tubing.
The observations and reasonings of Belgrand and Vallès, though their
conclusions have not been accepted by many, are very important in one
point of view. These writers insist much on the necessity of taking into
account, in estimating the relations between precipitation and
evaporation, the abstraction of water from the surface and surface
currents, by absorption and infiltration--an element unquestionably of
great value, but hitherto much neglected by meteorological inquirers,
who have very often reasoned as if the surface earth were either
impermeable to water, or already saturated with it; whereas, in fact, it
is a sponge, always imbibing humidity and always giving it off, not by
evaporation only, but by infiltration and percolation.
The destructive effects of inundations considered simply as a mechanical
power by which life is endangered, crops destroyed, and the artificial
constructions of man overthrown, are very terrible. Thus far, however,
the flood is a temporary and by no means an irreparable evil, for if its
ravages end here, the prolific powers of nature and the industry of man
soon restore what had been lost, and the face of the earth no longer
shows traces of the deluge that had overwhelmed it. Inundations have
even their compensations. The structures they destroy are replaced by
better and more secure erections, and if they sweep off a crop of corn,
they not unfrequently leave behind them, as they subside, a fertilizing
deposit which enriches the exhausted field for a succession of
seasons.[213] If, then, the too rapid flow of the surface waters
occasioned no other evil than to produce, once in ten years upon the
average, an inundation which should destroy the harvest of the low
grounds along the rivers, the damage would be too inconsiderable, and of
too transitory a character, to warrant the inconveniences and the
expense involved in the measures which the most competent judges in many
parts of Europe believe the respective governments ought to take to
obviate it.
_Destructive Action of Torrents._
But the great, the irreparable, the appalling mischiefs which have
already resulted, and threaten to ensue on a still more extensive scale
hereafter, from too rapid superficial drainage, are of a properly
geographical character, and consist primarily in erosion, displacement,
and transportation of the superficial strata, vegetable and mineral--of
the integuments, so to speak, with which nature has clothed the skeleton
framework of the globe. It is difficult to convey by description an idea
of the desolation of the regions most exposed to the ravages of torrent
and of flood; and the thousands, who, in these days of travel, are
whirled by steam near or even through the theatres of these calamities,
have but rare and imperfect opportunities of observing the destructive
causes in action. Still more rarely can they compare the past with the
actual condition of the provinces in question, and trace the progress of
their conversion from forest-crowned hills, luxuriant pasture grounds,
and abundant cornfields and vineyards well watered by springs and
fertilizing rivulets, to bald mountain ridges, rocky declivities, and
steep earth banks furrowed by deep ravines with beds now dry, now filled
by torrents of fluid mud and gravel hurrying down to spread themselves
over the plain, and dooming to everlasting barrenness the once
productive fields. In traversing such scenes, it is difficult to resist
the impression that nature pronounced the curse of perpetual sterility
and desolation upon these sublime but fearful wastes, difficult to
believe that they were once, and but for the folly of man might still
be, blessed with all the natural advantages which Providence has
bestowed upon the most favored climes. But the historical evidence is
conclusive as to the destructive changes occasioned by the agency of man
upon the flanks of the Alps, the Apennines, the Pyrenees, and other
mountain ranges in Central and Southern Europe, and the progress of
physical deterioration has been so rapid that, in some localities, a
single generation has witnessed the beginning and the end of the
melancholy revolution.
It is certain that a desolation, like that which has overwhelmed many
once beautiful and fertile regions of Europe, awaits an important part
of the territory of the United States, and of other comparatively new
countries over which European civilization is now extending its sway,
unless prompt measures are taken to check the action of destructive
causes already in operation. It is vain to expect that legislation can
do anything effectual to arrest the progress of the evil in those
countries, except so far as the state is still the proprietor of
extensive forests. Woodlands which have passed into private hands will
everywhere be managed, in spite of legal restrictions, upon the same
economical principles as other possessions, and every proprietor will,
as a general rule, fell his woods, unless he believes that it will be
for his pecuniary interest to preserve them. Few of the new provinces
which the last three centuries have brought under the control of the
European race, would tolerate any interference by the law-making power
with what they regard as the most sacred of civil rights--the right,
namely, of every man to do what he will with his own. In the Old World,
even in France, whose people, of all European nations, love best to be
governed and are least annoyed by bureaucratic supervision, law has been
found impotent to prevent the destruction, or wasteful economy, of
private forests; and in many of the mountainous departments of that
country, man is at this moment so fast laying waste the face of the
earth, that the most serious fears are entertained, not only of the
depopulation of those districts, but of enormous mischiefs to the
provinces contiguous to them.[214] The only legal provisions from which
anything is to be hoped, are such as shall make it a matter of private
advantage to the landholder to spare the trees upon his grounds, and
promote the growth of the young wood. Something may be done by exempting
standing forests from taxation, and by imposing taxes on wood felled for
fuel or for timber, something by premiums or honorary distinctions for
judicious management of the woods. It would be difficult to induce
governments, general or local, to make the necessary appropriations for
such purposes, but there can be no doubt that it would be sound economy
in the end.
In countries where there exist municipalities endowed with an
intelligent public spirit, the purchase and control of forests by such
corporations would often prove advantageous; and in some of the
provinces of Northern Lombardy, experience has shown that such
operations may be conducted with great benefit to all the interests
connected with the proper management of the woods. In Switzerland, on
the other hand, except in some few cases where woods have been preserved
as a defence against avalanches, the forests of the communes have been
productive of little advantage to the public interests, and have very
generally gone to decay. The rights of pasturage, everywhere destructive
to trees, combined with toleration of trespasses, have so reduced their
value, that there is, too often, nothing left that is worth protecting.
In the canton of Ticino, the peasants have very frequently voted to sell
the town woods and divide the proceeds among the corporators. The
sometimes considerable sums thus received are squandered in wild
revelry, and the sacrifice of the forests brings not even a momentary
benefit to the proprietors.[215]
It is evidently a matter of the utmost importance that the public, and
especially land owners, be roused to a sense of the dangers to which the
indiscriminate clearing of the woods may expose not only future
generations, but the very soil itself. Fortunately, some of the American
States, as well as the governments of many European colonies, still
retain the ownership of great tracts of primitive woodland. The State of
New York, for example, has, in its northeastern counties, a vast extent
of territory in which the lumberman has only here and there established
his camp, and where the forest, though interspersed with permanent
settlements, robbed of some of its finest pine groves, and often ravaged
by devastating fires, still covers far the largest proportion of the
surface. Through this territory, the soil is generally poor, and even
the new clearings have little of the luxuriance of harvest which
distinguishes them elsewhere. The value of the land for agricultural
uses is therefore very small, and few purchases are made for any other
purpose than to strip the soil of its timber. It has been often proposed
that the State should declare the remaining forest the inalienable
property of the commonwealth, but I believe the motive of the suggestion
has originated rather in poetical than in economical views of the
subject. Both these classes of considerations have a real worth. It is
desirable that some large and easily accessible region of American soil
should remain, as far as possible, in its primitive condition, at once a
museum for the instruction of the student, a garden for the recreation
of the lover of nature, and an asylum where indigenous tree, and humble
plant that loves the shade, and fish and fowl and four-footed beast, may
dwell and perpetuate their kind, in the enjoyment of such imperfect
protection as the laws of a people jealous of restraint can afford them.
The immediate loss to the public treasury from the adoption of this
policy would be inconsiderable, for these lands are sold at low rates.
The forest alone, economically managed, would, without injury, and even
with benefit to its permanence and growth, soon yield a regular income
larger than the present value of the fee.
The collateral advantages of the preservation of these forests would be
far greater. Nature threw up those mountains and clothed them with lofty
woods, that they might serve as a reservoir to supply with perennial
waters the thousand rivers and rills that are fed by the rains and snows
of the Adirondacks, and as a screen for the fertile plains of the
central counties against the chilling blasts of the north wind, which
meet no other barrier in their sweep from the Arctic pole. The climate
of Northern New York even now presents greater extremes of temperature
than that of Southern France. The long continued cold of winter is far
more intense, the short heats of summer not less fierce than in
Provence, and hence the preservation of every influence that tends to
maintain an equilibrium of temperature and humidity is of cardinal
importance. The felling of the Adirondack woods would ultimately involve
for Northern and Central New York consequences similar to those which
have resulted from the laying bare of the southern and western
declivities of the French Alps and the spurs, ridges, and detached peaks
in front of them.
It is true that the evils to be apprehended from the clearing of the
mountains of New York may be less in degree than those which a similar
cause has produced in Southern France, where the intensity of its action
has been increased by the inclination of the mountain declivities, and
by the peculiar geological constitution of the earth. The degradation of
the soil is, perhaps, not equally promoted by a combination of the same
circumstances, in any of the American Atlantic States, but still they
have rapid slopes and loose and friable soils enough to render
widespread desolation certain, if the further destruction of the woods
is not soon arrested. The effects of clearing are already perceptible in
the comparatively unviolated region of which I am speaking. The rivers
which rise in it flow with diminished currents in dry seasons, and with
augmented volumes of water after heavy rains. They bring down much
larger quantities of sediment, and the increasing obstructions to the
navigation of the Hudson, which are extending themselves down the
channel in proportion as the fields are encroaching upon the forest,
give good grounds for the fear of serious injury to the commerce of the
important towns on the upper waters of that river, unless measures are
taken to prevent the expansion of "improvements" which have already been
carried beyond the demands of a wise economy.
I have stated, in a general way, the nature of the evils in question,
and of the processes by which they are produced; but I shall make their
precise character and magnitude better understood by presenting some
descriptive and statistical details of facts of actual occurrence. I
select for this purpose the southeastern portion of France, not because
that territory has suffered more severely than some others, but because
its deterioration is comparatively recent, and has been watched and
described by very competent and trustworthy observers, whose reports are
more easily accessible than those published in other countries.[216]
The provinces of Dauphiny, Avignon, and Provence comprise a territory of
fourteen or fifteen thousand square miles, bounded northwest by the
Isere, northeast and east by the Alps, south by the Mediterranean, west
by the Rhone, and extending from 42° to about 45° of north latitude. The
surface is generally hilly and even mountainous, and several of the
peaks in Dauphiny rise above the limit of perpetual snow. The climate,
as compared with that of the United States in the same latitude, is
extremely mild. Little snow falls, except upon the higher mountain
ranges, the frosts are light, and the summers long, as might, indeed, be
inferred from the vegetation; for in the cultivated districts, the vine
and the fig everywhere flourish, the olive thrives as far north as
43½°, and upon the coast, grow the orange, the lemon, and the date
palm. The forest trees, too, are of southern type, umbrella pines,
various species of evergreen oaks, and many other trees and shrubs of
persistent broad-leaved foliage, characterizing the landscape.
The rapid slope of the mountains naturally exposed these provinces to
damage by torrents, and the Romans diminished their injurious effects by
erecting, in the beds of ravines, barriers of rocks loosely piled up,
which permitted a slow escape of the water, but compelled it to deposit
above the dikes the earth and gravel with which it was charged.[217] At
a later period the Crusaders brought home from Palestine, with much
other knowledge gathered from the wiser Moslems, the art of securing the
hillsides and making them productive by terracing and irrigation. The
forests which covered the mountains secured an abundant flow of springs,
and the process of clearing the soil went on so slowly that, for
centuries, neither the want of timber and fuel, nor the other evils
about to be depicted, were seriously felt. Indeed, throughout the Middle
Ages, these provinces were well wooded, and famous for the fertility and
abundance, not only of the low grounds, but of the hills.
Such was the state of things at the close of the fifteenth century. The
statistics of the seventeenth show that while there had been an increase
of prosperity and population in Lower Provence, as well as in the
correspondingly situated parts of the other two provinces I have
mentioned, there was an alarming decrease both in the wealth and in the
population of Upper Provence and Dauphiny, although, by the clearing of
the forests, a great extent of plough land and pasturage had been added
to the soil before reduced to cultivation. It was found, in fact, that
the augmented violence of the torrents had swept away, or buried in sand
and gravel, more land than had been reclaimed by clearing; and the taxes
computed by fires or habitations underwent several successive reductions
in consequence of the gradual abandonment of the wasted soil by its
starving occupants. The growth of the large towns on and near the Rhone
and the coast, their advance in commerce and industry, and the
consequently enlarged demand for agricultural products, ought naturally
to have increased the rural population and the value of their lands; but
the physical decay of the uplands was such that considerable tracts were
deserted altogether, and in Upper Provence, the fires which in 1471
counted 897, were reduced to 747 in 1699, to 728 in 1733, and to 635 in
1776.
These facts I take from the _La Provence au point de vue des Bois, des
Torrents et des Inondations_, of Charles de Ribbe, one of the highest
authorities, and I add further details from the same source.
"Commune of Barles, 1707: Two hills have become connected by land
slides, and have formed a lake which covers the best part of the soil.
1746: New slides buried twenty houses composing a village, no trace of
which is left; more than one third of the land had disappeared.
"Monans, 1724: Deserted by its inhabitants and no longer cultivated.
"Gueydan, 1760: It appears by records that the best grounds have been
swept off since 1756, and that ravines occupy their place.
"Digne, 1762: The river Bléone has destroyed the most valuable part of
the territory.
"Malmaison, 1768: The inhabitants have emigrated, all their fields
having been lost."
In the case of the commune of St. Laurent du Var, it appears that, after
clearings in the Alps, succeeded by others in the common woods of the
town, the floods of the torrent Var became more formidable, and had
already carried off much land as early as 1708. "The clearing continued,
and more soil was swept away in 1761. In 1762, after another destructive
inundation, many of the inhabitants emigrated, and in 1765, one half of
the territory had been laid waste.
"In 1766, the assessor Serraire said to the Assembly: 'As to the damage
caused by brooks and torrents, it is impossible to deny its extent.
Upper Provence is in danger of total destruction, and the waters which
lay it waste threaten also the ruin of the most valuable grounds on the
plain below. Villages have been almost submerged by torrents which
formerly had not even names, and large towns are on the point of
destruction from the same cause.'"
In 1776, Viscount Puget thus reported: "The mere aspect of Upper
Provence is calculated to appal the patriotic magistrate. One sees only
lofty mountains, deep valleys with precipitous sides, rivers with broad
beds and little water, impetuous torrents, which in floods lay waste the
cultivated land upon their banks and roll huge rocks along their
channels; steep and parched hillsides, the melancholy consequences of
indiscriminate clearing; villages whose inhabitants, finding no longer
the means of subsistence, are emigrating day by day; houses dilapidated
to huts, and but a miserable remnant of population."
"In a document of the year 1771, the ravages of the torrents were
compared to the effects of an earthquake, half the soil in many communes
seeming to have been swallowed up.
"Our mountains," said the administrators of the province of the Lower
Alps in 1792, "present nothing but a surface of stony tufa; clearing is
still going on, and the little rivulets are becoming torrents. Many
communes have lost their harvests, their flocks, and their houses by
floods. The washing down of the mountains is to be ascribed to the
clearings and the practice of burning them over."
These complaints, it will be seen, all date before the Revolution, but
the desolation they describe has since advanced with still swifter
steps.
Surell--whose valuable work, _Étude sur les Torrents des Hautes Alpes_,
published in 1841, presents the most appalling picture of the
desolations of the torrent, and, at the same time, the most careful
studies of the history and essential character of this great evil--in
speaking of the valley of Dévoluy, on page 152, says: "Everything
concurs to show that it was anciently wooded. In its peat bogs are
found buried trunks of trees, monuments of its former vegetation. In the
framework of old houses, one sees enormous timber, which is no longer to
be found in the district. Many localities, now completely bare, still
retain the name of 'wood,' and one of them is called, in old deeds,
_Comba nigra_ [Black forest or dell], on account of its dense woods.
These and many other proofs confirm the local traditions which are
unanimous on this point.
"There, as everywhere in the Upper Alps, the clearings began on the
flanks of the mountains, and were gradually extended into the valleys
and then to the highest accessible peaks. Then followed the Revolution,
and caused the destruction of the remainder of the trees which had thus
far escaped the woodman's axe."
In a note to this passage, the writer says: "Several persons have told
me that they had lost flocks of sheep, by straying, in the forests of
Mont Auroux, which covered the flanks of the mountain from La Cluse to
Agnères. These declivities are now as bare as the palm of the hand."
The ground upon the steep mountains being once bared of trees, and the
underwood killed by the grazing of horned cattle, sheep, and goats,
every depression becomes a watercourse. "Every storm," says Surell, page
153, "gives rise to a new torrent. Examples of such are shown, which,
though not yet three years old, have laid waste the finest fields of
their valleys, and whole villages have narrowly escaped being swept into
ravines formed in the course of a few hours. Sometimes the flood pours
in a sheet over the surface, without ravine or even bed, and ruins
extensive grounds, which are abandoned forever."
I cannot follow Surell in his description and classification of
torrents, and I must refer the reader to his instructive work for a full
exposition of the theory of the subject. In order, however, to show what
a concentration of destructive energies may be effected by felling the
woods that clothe and support the sides of mountain abysses, I cite his
description of a valley descending from the Col Isoard, which he calls
"a complete type of a basin of reception," that is, a gorge which serves
as a common point of accumulation and discharge for the waters of
several lateral torrents. "The aspect of the monstrous channel," says
he, "is frightful. Within a distance of less than three kilomètres
[= one mile and seven eighths English], more than sixty torrents hurl
into the depths of the gorge the debris torn from its two flanks. The
smallest of these secondary torrents, if transferred to a fertile
valley, would be enough to ruin it."
The eminent political economist Blanqui, in a memoir read before the
Academy of Moral and Political Science on the 25th of November, 1843,
thus expresses himself: "Important as are the causes of impoverishment
already described, they are not to be compared to the consequences which
have followed from the two inveterate evils of the Alpine provinces of
France, the extension of clearing and the ravages of torrents. * * The
most important result of this destruction is this: that the agricultural
capital, or rather the ground itself--which, in a rapidly increasing
degree, is daily swept away by the waters--is totally lost. Signs of
unparalleled destitution are visible in all the mountain zone, and the
solitudes of those districts are assuming an indescribable character of
sterility and desolation. The gradual destruction of the woods has, in a
thousand localities, annihilated at once the springs and the fuel.
Between Grenoble and Briançon in the valley of the Romanche, many
villages are so destitute of wood that they are reduced to the necessity
of baking their bread with sun-dried cowdung, and even this they can
afford to do but once a year. This bread becomes so hard that it can be
cut only with an axe, and I have myself seen a loaf of bread in
September, at the kneading of which I was present the January previous.
"Whoever has visited the valley of Barcelonette, those of Embrun, and of
Verdun, and that Arabia Petræa of the department of the Upper Alps,
called Dévoluy, knows that there is no time to lose, that in fifty years
from this date France will be separated from Savoy, as Egypt from
Syria, by a desert."[218]
It deserves to be specially noticed that the district here referred to,
though now among the most hopelessly waste in France, was very
productive even down to so late a period as the commencement of the
French Revolution. Arthur Young, writing in 1789, says: "About
Barcelonette and in the highest parts of the mountains, the hill
pastures feed a million of sheep, besides large herds of other cattle;"
and he adds: "With such a soil, and in such a climate we are not to
suppose a country barren because it is mountainous. The valleys I have
visited are, in general, beautiful."[219] He ascribes the same character
to the provinces of Dauphiny, Provence, and Auvergne, and, though he
visited, with the eye of an attentive and practised observer, many of
the scenes since blasted with the wild desolation described by Blanqui,
the Durance and a part of the course of the Loire are the only streams
he mentions as inflicting serious injury by their floods. The ravages of
the torrents had, indeed, as we have seen, commenced earlier in some
other localities, but we are authorized to infer that they were, in
Young's time, too limited in range, and relatively too insignificant, to
require notice in a general view of the provinces where they have now
ruined so large a proportion of the soil.
But I resume my citations.
"I do not exaggerate," says Blanqui. "When I shall have finished my
excursion and designated localities by their names, there will rise, I
am sure, more than one voice from the spots themselves, to attest the
rigorous exactness of this picture of their wretchedness. I have never
seen its equal even in the Kabyle villages of the province of
Constantine; for there you can travel on horseback, and you find grass
in the spring, whereas in more than fifty communes in the Alps there is
absolutely nothing.
"The clear, brilliant, Alpine sky of Embrun, of Gap, of Barcelonette,
and of Digne, which for months is without a cloud, produces droughts
interrupted only by diluvial rains like those of the tropics. The abuse
of the right of pasturage and the felling of the woods have stripped the
soil of all its grass and all its trees, and the scorching sun bakes it
to the consistence of porphyry. When moistened by the rain, as it has
neither support nor cohesion, it rolls down to the valleys, sometimes in
floods resembling black, yellow, or reddish lava, sometimes in streams
of pebbles, and even huge blocks of stone, which pour down with a
frightful roar, and in their swift course exhibit the most convulsive
movements. If you overlook from an eminence one of these landscapes
furrowed with so many ravines, it presents only images of desolation and
of death. Vast deposits of flinty pebbles, many feet in thickness, which
have rolled down and spread far over the plain, surround large trees,
bury even their tops, and rise above them, leaving to the husbandman no
longer a ray of hope. One can imagine no sadder spectacle than the deep
fissures in the flanks of the mountains, which seem to have burst forth
in eruption to cover the plains with their ruins. These gorges, under
the influence of the sun which cracks and shivers to fragments the very
rocks, and of the rain which sweeps them down, penetrate deeper and
deeper into the heart of the mountain, while the beds of the torrents
issuing from them are sometimes raised several feet, in a single year,
by the debris, so that they reach the level of the bridges, which, of
course, are then carried off. The torrent beds are recognized at a great
distance, as they issue from the mountains, and they spread themselves
over the low grounds, in fan-shaped expansions, like a mantle of stone,
sometimes ten thousand feet wide, rising high at the centre, and curving
toward the circumference till their lower edges meet the plain.
"Such is their aspect in dry weather. But no tongue can give an adequate
description of their devastations in one of those sudden floods which
resemble, in almost none of their phenomena, the action of ordinary
river water. They are now no longer overflowing brooks, but real seas,
tumbling down in cataracts, and rolling before them blocks of stone,
which are hurled forward by the shock of the waves like balls shot out
by the explosion of gunpowder. Sometimes ridges of pebbles are driven
down when the transporting torrent does not rise high enough to show
itself, and then the movement is accompanied with a roar louder than the
crash of thunder. A furious wind precedes the rushing water and
announces its approach. Then comes a violent eruption, followed by a
flow of muddy waves, and after a few hours all returns to the dreary
silence which at periods of rest marks these abodes of desolation.
"This is but an imperfect sketch of this scourge of the Alps. Its
devastations are increasing with the progress of clearing, and are every
day turning a portion of our frontier departments into barren wastes.
"The unfortunate passion for clearing manifested itself at the beginning
of the French Revolution, and has much increased under the pressure of
immediate want. It has now reached an extreme point, and must be
speedily checked, or the last inhabitant will be compelled to retreat
when the last tree falls.
"The elements of destruction are increasing in violence. Rivers might be
mentioned whose beds have been raised ten feet in a single year. The
devastation advances in geometrical progression as the higher slopes are
bared of their wood, and 'the ruin from above,' to use the words of a
peasant, 'helps to hasten the desolation below.'
"The Alps of Provence present a terrible aspect. In the more equable
climate of Northern France, one can form no conception of those parched
mountain gorges where not even a bush can be found to shelter a bird,
where, at most, the wanderer sees in summer here and there a withered
lavender, where all the springs are dried up, and where a dead silence,
hardly broken by even the hum of an insect, prevails. But if a storm
bursts forth, masses of water suddenly shoot from the mountain heights
into the shattered gulfs, waste without irrigating, deluge without
refreshing the soil they overflow in their swift descent, and leave it
even more seared than it was from want of moisture. Man at last retires
from the fearful desert, and I have, the present season, found not a
living soul in districts where I remember to have enjoyed hospitality
thirty years ago."
In 1853, ten years after the date of Blanqui's memoir, M. de Bonville,
prefect of the Lower Alps, addressed to the Government a report in which
the following passages occur:
"It is certain that the productive mould of the Alps, swept off by the
increasing violence of that curse of the mountains, the torrents, is
daily diminishing with fearful rapidity. All our Alps are wholly, or in
large proportion, bared of wood. Their soil, scorched by the sun of
Provence, cut up by the hoofs of the sheep, which, not finding on the
surface the grass they require for their sustenance, scratch the ground
in search of roots to satisfy their hunger, is periodically washed and
carried off by melting snows and summer storms.
"I will not dwell on the effects of the torrents. For sixty years they
have been too often depicted to require to be further discussed, but it
is important to show that their ravages are daily extending the range of
devastation. The bed of the Durance, which now in some places exceeds
2,000 mètres [about 6,600 feet, or a mile and a quarter] in width, and,
at ordinary times, has a current of water less than 10 mètres [about 33
feet] wide, shows something of the extent of the damage.[220] Where, ten
years ago, there were still woods and cultivated grounds to be seen,
there is now but a vast torrent: there is not one of our mountains which
has not at least one torrent, and new ones are daily forming.
"An indirect proof of the diminution of the soil is to be found in the
depopulation of the country. In 1852, I reported to the General Council
that, according to the census of that year, the population of the
department of the Lower Alps had fallen off no less than 5,000 souls in
the five years between 1846 and 1851.
"Unless prompt and energetic measures are taken, it is easy to fix the
epoch when the French Alps will be but a desert. The interval between
1851 and 1856 will show a further decrease of population. In 1862, the
ministry will announce a continued and progressive reduction in the
number of acres devoted to agriculture; every year will aggravate the
evil, and, in a half century, France will count more ruins, and a
department the less."
Time has verified the predictions of De Bonville. The later census
returns show a progressive diminution in the population of the
departments of the Lower Alps, the Isère, the Drome, Ariège, the Upper
and the Lower Pyrenees, the Lozère, the Ardennes, the Doubs, the Vosges,
and, in short, in all the provinces formerly remarkable for their
forests. This diminution is not to be ascribed to a passion for foreign
emigration, as in Ireland, and in parts of Germany and of Italy; it is
simply a transfer of population from one part of the empire to another,
from soils which human folly has rendered uninhabitable, by ruthlessly
depriving them of their natural advantages and securities, to provinces
where the face of the earth was so formed by nature as to need no such
safeguards, and where, consequently, she preserves her outlines in spite
of the wasteful improvidence of man.[221]
Highly colored as these pictures seem, they are not exaggerated,
although the hasty tourist through Southern France and Northern Italy,
finding little in his high road experiences to justify them, might
suppose them so. The lines of communication by locomotive train and
diligence lead generally over safer ground, and it is only when they
ascend the Alpine passes and traverse the mountain chains, that scenes
somewhat resembling those just described fall under the eye of the
ordinary traveller. But the extension of the sphere of devastation, by
the degradation of the mountains and the transportation of their debris,
is producing analogous effects upon the lower ridges of the Alps and the
plains which skirt them; and even now one needs but an hour's departure
from some great thoroughfares to reach sites where the genius of
destruction revels as wildly as in the most frightful of the abysses
which Blanqui has painted.[222]
There is one effect of the action of torrents which few travellers on
the Continent are heedless enough to pass without notice. I refer to the
elevation of the beds of mountain streams in consequence of the deposit
of the debris with which they are charged. To prevent the spread of sand
and gravel over the fields and the deluging overflow of the raging
waters, the streams are confined by walls and embankments, which are
gradually built higher and higher as the bed of the torrent is raised,
so that, to reach a river, you ascend from the fields beside it; and
sometimes the ordinary level of the stream is above the streets and even
the roofs of the towns through which it passes.[223]
The traveller who visits the depths of an Alpine ravine, observes the
length and width of the gorge and the great height and apparent solidity
of the precipitous walls which bound it, and calculates the mass of rock
required to fill the vacancy, can hardly believe that the humble
brooklet which purls at his feet has been the principal agent in
accomplishing this tremendous erosion. Closer observation will often
teach him, that the seemingly unbroken rock which overhangs the valley
is full of cracks and fissures, and really in such a state of
disintegration that every frost must bring down tons of it. If he
compute the area of the basin which finds here its only discharge, he
will perceive that a sudden thaw of the winter's deposit of snow, or one
of those terrible discharges of rain so common in the Alps, must send
forth a deluge mighty enough to sweep down the largest masses of gravel
and of rock.[224] The simple measurement of the cubical contents of the
semi-circular hillock which he climbed before he entered the gorge, the
structure and composition of which conclusively show that it must have
been washed out of this latter by torrential action, will often account
satisfactorily for the disposal of most of the matter which once filled
the ravine.
It must further be remembered, that every inch of the violent movement
of the rocks is accompanied with crushing concussion, or, at least, with
great abrasion, and, as you follow the deposit along the course of the
waters which transport it, you find the stones gradually rounding off in
form, and diminishing in size until they pass successively into gravel,
sand, impalpable slime.
I do not mean to assert that all the rocky valleys of the Alps have been
produced by the action of torrents resulting from the destruction of the
forests. All the greater, and many of the smaller channels, by which
that chain is drained, owe their origin to higher causes. They are
primitive fissures, ascribable to disruption in upheaval or other
geological convulsion, widened and scarped, and often even polished, so
to speak, by the action of glaciers during the ice period, and but
little changed in form by running water in later eras.[225]
In these valleys of ancient formation, which extend into the very heart
of the mountains, the streams, though rapid, have lost the true
torrential character, if, indeed, they ever possessed it. Their beds
have become approximately constant, and their walls no longer crumble
and fall into the waters that wash their bases. The torrent-worn
ravines, of which I have spoken, are of later date, and belong more
properly to what may be called the crust of the Alps, consisting of
loose rocks, of gravel, and of earth, strewed along the surface of the
great declivities of the central ridge, and accumulated thickly between
their solid buttresses. But it is on this crust that the mountaineer
dwells. Here are his forests, here his pastures, and the ravages of the
torrent both destroy his world, and convert it into a source of
overwhelming desolation to the plains below.
_Transporting Power of Rivers._
An instance that fell under my own observation in 1857, will serve to
show something of the eroding and transporting power of streams which,
in these respects, fall incalculably below the torrents of the Alps. In
a flood of the Ottaquechee, a small river which flows through Woodstock,
Vermont, a milldam on that stream burst, and the sediment with which the
pond was filled, estimated after careful measurement at 13,000 cubic
yards, was carried down by the current. Between this dam and the slack
water of another, four miles below, the bed of the stream, which is
composed of pebbles interspersed in a few places with larger stones, is
about sixty-five feet wide, though, at low water, the breadth of the
current is considerably less. The sand and fine gravel were smoothly and
evenly distributed over the bed to a width of fifty-five or sixty feet,
and for a distance of about two miles, except at two or three
intervening rapids, filled up all the interstices between the stones,
covering them to the depth of nine or ten inches, so as to present a
regularly formed concave channel, lined with sand, and reducing the
depth of water, in some places, from five or six feet to fifteen or
eighteen inches. Observing this deposit after the river had subsided and
become so clear that the bottom could be seen, I supposed that the next
flood would produce an extraordinary erosion of the banks and some
permanent changes in the channel of the stream, in consequence of the
elevation of the bed and the filling up of the spaces between the stones
through which formerly much water had flowed; but no such result
followed. The spring freshet of the next year entirely washed out the
sand its predecessor had deposited, carried it to ponds and still-water
reaches below, and left the bed of the river almost precisely in its
former condition, though, of course, with the slight displacement of the
pebbles which every flood produces in the channels of such streams. The
pond, though often previously discharged by the breakage of the dam, had
then been undisturbed for about twenty-five years, and its contents
consisted almost entirely of sand, the rapidity of the current in floods
being such that it would let fall little lighter sediment, even above an
obstruction like a dam. The quantity I have mentioned evidently bears a
very inconsiderable proportion to the total erosion of the stream
during that period, because the wash of the banks consists chiefly of
fine earth rather than of sand, and after the pond was once filled, or
nearly so, even this material could no longer be deposited in it. The
fact of the complete removal of the deposit I have described between the
two dams in a single freshet, shows that, in spite of considerable
obstruction from roughness of bed, large quantities of sand may be taken
up and carried off by streams of no great rapidity of inclination; for
the whole descent of the bed of the river between the two dams--a
distance of four miles--is but sixty feet, or fifteen feet to the mile.
_The Po and its Deposits._
The current of the river Po, for a considerable distance after its
volume of water is otherwise sufficient for continuous navigation, is
too rapid for that purpose until near Piacenza, where its velocity
becomes too much reduced to transport great quantities of mineral
matter, except in a state of minute division. Its southern affluents
bring down from the Apennines a large quantity of fine earth from
various geological formations, while its Alpine tributaries west of the
Ticino are charged chiefly with rock ground down to sand or
gravel.[226] The bed of the river has been somewhat elevated by the
deposits in its channel, though not by any means above the level of the
adjacent plains as has been so often represented. The dikes, which
confine the current at high water, at the same time augment its velocity
and compel it to carry most of its sediment to the Adriatic. It has,
therefore, raised neither its own channel nor its alluvial shores, as it
would have done if it had remained unconfined. But, as the surface of
the water in floods is from six to fifteen feet above the general level
of its banks, the Po can, at that period, receive no contributions of
earth from the washing of the fields of Lombardy, and there is no doubt
that a large proportion of the sediment it now deposits at its mouth
descended from the Alps in the form of rock, though reduced by the
grinding action of the waters, in its passage seaward, to the condition
of fine sand, and often of silt.[227]
We know little of the history of the Po, or of the geography of the
coast near the point where it enters the Adriatic, at any period more
than twenty centuries before our own. Still less can we say how much of
the plains of Lombardy had been formed by its action, combined with
other causes, before man accelerated its levelling operations by felling
the first woods on the mountains whence its waters are derived. But we
know that since the Roman conquest of Northern Italy, its deposits have
amounted to a quantity which, if recemented into rock, recombined into
gravel, common earth, and vegetable mould, and restored to the
situations where eruption or upheaval originally placed, or vegetation
deposited it, would fill up hundreds of deep ravines in the Alps and
Apennines, change the plan and profile of their chains, and give their
southern and northern faces respectively a geographical aspect very
different from that they now present. Ravenna, forty miles south of the
principal mouth of the Po, was built like Venice, in a lagoon, and the
Adriatic still washed its walls at the commencement of the Christian
era. The mud of the Po has filled up the lagoon, and Ravenna is now four
miles from the sea. The town of Adria, which lies between the Po and the
Adige, at the distance of some four or five miles from each, was once a
harbor famous enough to have given its name to the Adriatic sea, and it
was still a seaport in the time of Augustus. The combined action of the
two rivers has so advanced the coast line that Adria is now about
fourteen miles inland, and, in other places, the deposits made within
the same period by these and other neighboring streams have a width of
twenty miles.
What proportion of the earth with which they are charged these rivers
have borne out into deep water, during the last two thousand years, we
do not know, but as they still transport enormous quantities, as the
North Adriatic appears to have shoaled rapidly, and as long islands,
composed in great part of fluviatile deposits, have formed opposite
their mouths, it must evidently have been very great. The floods of the
Po occur but once, or sometimes twice in a year.[228] At other times,
its waters are comparatively limpid and seem to hold no great amount of
mud or fine sand in mechanical suspension; but at high water it contains
a large proportion of solid matter, and according to Lombardini, it
annually transports to the shores of the Adriatic not less than
42,760,000 cubic mètres, or very nearly 55,000,000 cubic yards, which
carries the coast line out into the sea at the rate of more than 200
feet in a year.[229] The depth of the annual deposit is stated at
eighteen centimètres, or rather more than seven inches, and it would
cover an area of not much less than ninety square miles with a layer of
that thickness. The Adige, also, brings every year to the Adriatic many
million cubic yards of Alpine detritus, and the contributions of the
Brenta from the same source are far from inconsiderable. The Adriatic,
however, receives but a small proportion of the soil and rock washed
away from the Italian slope of the Alps and the northern declivity of
the Apennines by torrents. Nearly the whole of the debris thus removed
from the southern face of the Alps between Monte Rosa and the sources of
the Adda--a length of watershed not less than one hundred and fifty
miles--is arrested by the still waters of the Lakes Maggiore and Como,
and some smaller lacustrine reservoirs, and never reaches the sea. The
Po is not continuously embanked except for the lower half of its course.
Above Piacenza, therefore, it spreads and deposits sediment over a wide
surface, and the water withdrawn from it for irrigation at lower points,
as well as its inundations in the occasional ruptures of its banks,
carry over the adjacent soil a large amount of slime.
If we add to the estimated annual deposits of the Po at its mouth, the
earth and sand transported to the sea by the Adige, the Brenta, and
other less important streams, the prodigious mass of detritus swept into
Lago Maggiore by the Tosa, the Maggia, and the Ticino, into the lake of
Como by the Maira and the Adda, into the lake of Garda by its
affluents, and the yet vaster heaps of pebbles, gravel, and earth
permanently deposited by the torrents near their points of eruption from
mountain gorges, or spread over the wide plains at lower levels, we may
safely assume that we have an aggregate of not less than four times the
quantity carried to the Adriatic by the Po, or 220,000,000 cubic yards
of solid matter, abstracted every year from the Italian Alps and the
Apennines, and removed out of their domain by the force of running
water.[230]
The present rate of deposit at the mouth of the Po has continued since
the year 1600, the previous advance of the coast, after the year 1200,
having been only one third as rapid. The great increase of erosion and
transport is ascribed by Lombardini chiefly to the destruction of the
forests in the basin of that river and the valleys, of its tributaries,
since the beginning of the seventeenth century.[231] We have no data to
show the rate of deposit in any given century before the year 1200, and
it doubtless varied according to the progress of population and the
consequent extension of clearing and cultivation. The transporting power
of torrents is greatest soon after their formation, because at that time
their points of delivery are lower, and, of course, their general slope
and velocity more rapid, than after years of erosion above, and deposit
below, have depressed the beds of their mountain valleys, and elevated
the channels of their lower course. Their eroding action also is most
powerful at the same period, both because their mechanical force is then
greatest, and because the loose earth and stones of freshly cleared
forest ground are most easily removed. Many of the Alpine valleys west
of the Ticino--that of the Dora Baltea for instance--were nearly
stripped of their forests in the days of the Roman empire, others in the
Middle Ages, and, of course, there must have been, at different periods
before the year 1200, epochs when the erosion and transportation of
solid matter from the Alps and the Apennines were as great as since the
year 1600.
Upon the whole, we shall not greatly err if we assume that, for a period
of not less than two thousand years, the walls of the basin of the
Po--the Italian slope of the Alps, and the northern and northeastern
declivities of the Apennines--have annually sent down into the Adriatic,
the lakes, and the plains, not less than 150,000,000 cubic yards of
earth and disintegrated rock. We have, then, an aggregate of
300,000,000,000 cubic yards of such material, which, allowing to the
mountain surface in question an area of 50,000,000,000 square yards,
would cover the whole to the depth of six yards.[232] There are very
large portions of this area, where, as we know from ancient
remains--roads, bridges, and the like--from other direct testimony, and
from geological considerations, very little degradation has taken place
within twenty centuries, and hence the quantity to be assigned to
localities where the destructive causes have been most active is
increased in proportion.
If this vast mass of pulverized rock and earth were restored to the
localities from which it was derived, it certainly would not obliterate
valleys and gorges hollowed out by great geological causes, but it would
reduce the length and diminish the depth of ravines of later formation,
modify the inclination of their walls, reclothe with earth many bare
mountain ridges, essentially change the line of junction between plain
and mountain, and carry back a long reach of the Adriatic coast many
miles to the west.[233]
It is, indeed, not to be supposed that all the degradation of the
mountains is due to the destruction of the forests--that the flanks of
every Alpine valley in Central Europe below the snow line were once
covered with earth and green with woods, but there are not many
particular cases, in which we can, with certainty, or even with strong
probability, affirm the contrary.
We cannot measure the share which human action has had in augmenting the
intensity of causes of mountain degradation, but we know that the
clearing of the woods has, in some cases, produced within two or three
generations, effects as blasting as those generally ascribed to
geological convulsions, and has laid waste the face of the earth more
hopelessly than if it had been buried by a current of lava or a shower
of volcanic sand. Now torrents are forming every year in the Alps.
Tradition, written records, and analogy concur to establish the belief
that the ruin of most of the now desolate valleys in those mountains is
to be ascribed to the same cause, and authentic descriptions of the
irresistible force of the torrent show that, aided by frost and heat, it
is adequate to level Mont Blanc and Monte Rosa themselves, unless new
upheavals shall maintain their elevation.
It has been contended that all rivers which take their rise in mountains
originated in torrents. These, it is said, have lowered the summits by
gradual erosion, and, with the material thus derived, have formed shoals
in the sea which once beat against the cliffs; then, by successive
deposits, gradually raised them above the surface, and finally expanded
them into broad plains traversed by gently flowing streams. If we could
go back to earlier geological periods, we should find this theory often
verified, and we cannot fail to see that the torrents go on at the
present hour, depressing still lower the ridges of the Alps and the
Apennines, raising still higher the plains of Lombardy and Provence,
extending the coast still farther into the Adriatic and the
Mediterranean, reducing the inclination of their own beds and the
rapidity of their flow, and thus tending to become river-like in
character.
There are cases where torrents cease their ravages of themselves, in
consequence of some change in the condition of the basin where they
originate, or of the face of the mountain at a higher level, while the
plain or the sea below remains in substantially the same state as
before. If a torrent rises in a small valley containing no great amount
of earth and of disintegrated or loose rock, it may, in the course of a
certain period, wash out all the transportable material, and if the
valley is then left with solid walls, it will cease to furnish debris to
be carried down by floods. If, in this state of things, a new channel be
formed at an elevation above the head of the valley, it may divert a
part, or even the whole of the rain water and melted snow which would
otherwise have flowed into it, and the once furious torrent now sinks to
the rank of a humble and harmless brooklet. "In traversing this
department," says Surell, "one often sees, at the outlet of a gorge, a
flattened hillock, with a fan-shaped outline and regular slopes; it is
the bed of dejection of an ancient torrent. It sometimes requires long
and careful study to detect the primitive form, masked as it is by
groves of trees, by cultivated fields, and often by houses, but, when
examined closely, and from different points of view, its characteristic
figure manifestly appears, and its true history cannot be mistaken.
Along the hillock flows a streamlet, issuing from the ravine, and
quietly watering the fields. This was originally a torrent, and in the
background may be discovered its mountain basin. Such _extinguished_
torrents, if I may use the expression, are numerous."[234]
But for the intervention of man and domestic animals, these latter
beneficent revolutions would occur more frequently, proceed more
rapidly. The new scarped mountains, the hillocks of debris, the plains
elevated by sand and gravel spread over them, the shores freshly formed
by fluviatile deposits, would clothe themselves with shrubs and trees,
the intensity of the causes of degradation would be diminished, and
nature would thus regain her ancient equilibrium. But these processes,
under ordinary circumstances, demand, not years, generations, but
centuries;[235] and man, who even now finds scarce breathing room on
this vast globe, cannot retire from the Old World to some yet
undiscovered continent, and wait for the slow action of such causes to
replace, by a new creation, the Eden he has wasted.
_Mountain Slides._
I have said that the mountainous regions of the Atlantic States of the
American Union are exposed to similar ravages, and I may add that there
is, in some cases, reason to apprehend from the same cause even more
appalling calamities than those which I have yet described. The slide in
the Notch of the White Mountains, by which the Willey family lost their
lives, is an instance of the sort I refer to, though I am not able to
say that in this particular case, the slip of the earth and rock was
produced by the denudation of the surface. It may have been occasioned
by this cause, or by the construction of the road through the Notch, the
excavations for which, perhaps, cut through the buttresses that
supported the sloping strata above.
Not to speak of the fall of earth when the roots which held it together,
and the bed of leaves and mould which sheltered it both from
disintegrating frost and from sudden drenching and dissolution by heavy
showers, are gone, it is easy to see that, in a climate with severe
winters, the removal of the forest, and, consequently, of the soil it
had contributed to form, might cause the displacement and descent of
great masses of rock. The woods, the vegetable mould, and the soil
beneath, protect the rocks they cover from the direct action of heat and
cold, and from the expansion and contraction which accompany them. Most
rocks, while covered with earth, contain a considerable quantity of
water.[236] A fragment of rock pervaded with moisture cracks and splits,
if thrown into a furnace, and sometimes with a loud detonation; and it
is a familiar observation that the fire, in burning over newly cleared
lands, breaks up and sometimes almost pulverizes the stones. This effect
is due partly to the unequal expansion of the stone, partly to the
action of heat on the water it contains in its pores. The sun, suddenly
let in upon rock which had been covered with moist earth for centuries,
produces more or less disintegration in the same way, and the stone is
also exposed to chemical influences from which it was sheltered before.
But in the climate of the United States as well as of the Alps, frost is
a still more powerful agent in breaking up mountain masses. The soil
that protects the lime and sand stone, the slate and the granite from
the influence of the sun, also prevents the water which filters into
their crevices and between their strata from freezing in the hardest
winters, and the moisture descends, in a liquid form, until it escapes
in springs, or passes off by deep subterranean channels. But when the
ridges are laid bare, the water of the autumnal rains fills the minutest
pores and veins and fissures and lines of separation of the rocks, then
suddenly freezes, and bursts asunder huge, and apparently solid blocks
of adamantine stone.[237] Where the strata are inclined at a
considerable angle, the freezing of a thin film of water over a large
interstratal area might occasion a slide that should cover miles with
its ruins; and similar results might be produced by the simple
hydrostatic pressure of a column of water, admitted by the removal of
the covering of earth to flow into a crevice faster than it could escape
through orifices below.
Earth or rather mountain slides, compared to which the catastrophe that
buried the Willey family in New Hampshire was but a pinch of dust, have
often occurred in the Swiss Italian, and French Alps. The land slip,
which overwhelmed and covered to the depth of seventy feet, the town of
Plurs in the valley of the Maira, on the night of the 4th of September,
1618, sparing not a soul of a population of 2,430 inhabitants, is one of
the most memorable of these catastrophes, and the fall of the Rossberg
or Rufiberg, which destroyed the little town of Goldau in Switzerland,
and 450 of its people, on the 2d of September, 1806, is almost equally
celebrated. In 1771, according to Wessely, the mountain peak Piz, near
Alleghe in the province of Belluno, slipped into the bed of the
Cordevole, a tributary of the Piave, destroying in its fall three
hamlets and sixty lives. The rubbish filled the valley for a distance of
nearly two miles, and, by damming up the waters of the Cordevole, formed
a lake about three miles long, and a hundred and fifty feet deep, which
still subsists, though reduced to half its original length by the
wearing down of its outlet.[238]
On the 14th of February, 1855, the hill of Belmonte, a little below the
parish of San Stefano, in Tuscany, slid into the valley of the Tiber,
which consequently flooded the village to the depth of fifty feet, and
was finally drained off by a tunnel. The mass of debris is stated to
have been about 3,500 feet long, 1,000 wide, and not less than 600
high.[239]
Such displacements of earth and rocky strata rise to the magnitude of
geological convulsions, but they are of so rare occurrence in countries
still covered by the primitive forest, so common where the mountains
have been stripped of their native covering, and, in many cases, so
easily explicable by the drenching of incohesive earth from rain, or the
free admission of water between the strata of rocks--both of which a
coating of vegetation would have prevented--that we are justified in
ascribing them for the most part to the same cause as that to which the
destructive effects of mountain torrents are chiefly due--the felling of
the woods.
In nearly every case of this sort the circumstances of which are known,
the immediate cause of the slip has been, either an earthquake, the
imbibition of water in large quantities by bare earth, or its
introduction between or beneath solid strata. If water insinuates itself
between the strata, it creates a sliding surface, or it may, by its
expansion in freezing, separate beds of rock, which had been nearly
continuous before, widely enough to allow the gravitation of the
superincumbent mass to overcome the resistance afforded by inequalities
of face and by friction; if it finds its way beneath hard earth or rock
reposing on clay or other bedding of similar properties, it converts the
supporting layer into a semi-fluid mud, which opposes no obstacle to the
sliding of the strata above.
The upper part of the mountain which buried Goldau was composed of a
hard but brittle conglomerate, called _nagelflue_, resting on an
unctuous clay, and inclining rapidly toward the village. Much earth
remained upon the rock, in irregular masses, but the woods had been
felled, and the water had free access to the surface, and to the
crevices which sun and frost had already produced in the rock, and of
course, to the slimy stratum beneath. The whole summer of 1806 had been
very wet, and an almost incessant deluge of rain had fallen the day
preceding the catastrophe, as well as on that of its occurrence. All
conditions then, were favorable to the sliding of the rock, and, in
obedience to the laws of gravitation, it precipitated itself into the
valley as soon as its adhesion to the earth beneath it was destroyed by
the conversion of the latter into a viscous paste. The mass that fell
measured between two and a half and three miles in length by one
thousand feet in width, and its average thickness is thought to have
been about a hundred feet. The highest portion of the mountain was more
than three thousand feet above the village, and the momentum acquired by
the rocks and earth in their descent carried huge blocks of stone far up
the opposite slope of the Rigi.
The Piz, which fell into the Cordevole, rested on a steeply inclined
stratum of limestone, with a thin layer of calcareous marl intervening,
which, by long exposure to frost and the infiltration of water, had lost
its original consistence, and become a loose and slippery mass instead
of a cohesive and tenacious bed.
_Protection against fall of Rocks and Avalanches by Trees._
Forests often subserve a valuable purpose in preventing the fall of
rocks, by mere mechanical resistance. Trees, as well as herbaceous
vegetation, grow in the Alps upon declivities of surprising steepness of
inclination, and the traveller sees both luxuriant grass and flourishing
woods on slopes at which the soil, in the dry air of lower regions,
would crumble and fall by the weight of its own particles. When loose
rocks lie scattered on the face of these declivities, they are held in
place by the trunks of the trees, and it is very common to observe a
stone that weighs hundreds of pounds, perhaps even tons, resting against
a tree which has stopped its progress just as it was beginning to slide
down to a lower level. When a forest in such a position is cut, these
blocks lose their support, and a single wet season is enough not only to
bare the face of a considerable extent of rock, but to cover with earth
and stone many acres of fertile soil below.[240]
In Switzerland and other snowy and mountainous countries, forests render
a most important service by preventing the formation and fall of
destructive avalanches, and in many parts of the Alps exposed to this
catastrophe, the woods are protected, though too often ineffectually, by
law. No forest, indeed, could arrest a large avalanche once in motion,
but the mechanical resistance afforded by the trees prevents their
formation, both by obstructing the wind, which gives to the dry snow of
the _Staub-Lawine_, or dust avalanche, its first impulse, and by
checking the disposition of moist snow to gather itself into what is
called the _Rutsch-Lawine_, or sliding avalanche. Marschand states that,
the very first winter after the felling of the trees on the higher part
of a declivity between Saanen and Gsteig where the snow had never been
known to slide, an avalanche formed itself in the clearing, thundered
down the mountain, and overthrew and carried with it a hitherto
unviolated forest to the amount of nearly a million cubic feet of
timber.[241] The path once opened down the flanks of the mountain, the
evil is almost beyond remedy. The snow sometimes carries off the earth
from the face of the rock, or, if the soil is left, fresh slides every
winter destroy the young plantations, and the restoration of the wood
becomes impossible. The track widens with every new avalanche. Dwellings
and their occupants are buried in the snow, or swept away by the rushing
mass, or by the furious blasts it occasions through the displacement of
the air; roads and bridges are destroyed; rivers blocked up, which swell
till they overflow the valley above, and then, bursting their snowy
barrier, flood the fields below with all the horrors of a winter
inundation.[242]
_Principal Causes of the Destruction of the Forest._
The needs of agriculture are the most familiar cause of the destruction
of the forest in new countries; for not only does an increasing
population demand additional acres to grow the vegetables which feed it
and its domestic animals, but the slovenly husbandry of the border
settler soon exhausts the luxuriance of his first fields, and compels
him to remove his household gods to a fresher soil. With growing
numbers, too, come the many arts for which wood is the material. The
demands of the near and the distant market for this product excite the
cupidity of the hardy forester, and a few years of that wild industry of
which Springer's "Forest Life and Forest Trees" so vividly depicts the
dangers and the triumphs, suffice to rob the most inaccessible glens of
their fairest ornaments. The value of timber increases with its
dimensions in almost geometrical proportion, and the tallest, most
vigorous, and most symmetrical trees fall the first sacrifice. This is a
fortunate circumstance for the remainder of the wood; for the impatient
lumberman contents himself with felling a few of the best trees, and
then hurries on to take his tithe of still virgin groves.
The unparalleled facilities for internal navigation, afforded by the
numerous rivers of the present and former British colonial possessions
in North America, have proved very fatal to the forests of that
continent. Quebec has become a centre for a lumber trade, which, in the
bulk of its material, and, consequently, in the tonnage required for its
transportation, rivals the commerce of the greatest European cities.
Immense rafts are collected at Quebec from the great Lakes, from the
Ottawa, and from all the other tributaries which unite to swell the
current of the St. Lawrence and help it to struggle against its mighty
tides.[243] Ships, of burden formerly undreamed of, have been built to
convey the timber to the markets of Europe, and during the summer months
the St. Lawrence is almost as crowded with vessels as the Thames.[244]
Of late, Chicago, in Illinois, has been one of the greatest lumber as
well as grain depots of the United States, and it receives and
distributes contributions from all the forests in the States washed by
Lake Michigan, as well as from some more distant points.
The operations of the lumberman involve other dangers to the woods
besides the loss of the trees felled by him. The narrow clearings around
his _shanties_[245] form openings which let in the wind, and thus
sometimes occasion the overthrow of thousands of trees, the fall of
which dams up small streams, and creates bogs by the spreading of the
waters, while the decaying trunks facilitate the multiplication of the
insects which breed in dead wood, and are, some of them, injurious to
living trees. The escape and spread of camp fires, however, is the most
devastating of all the causes of destruction that find their origin in
the operations of the lumberman. The proportion of trees fit for
industrial uses is small in all primitive woods. Only these fall before
the forester's axe, but the fire destroys, indiscriminately, every age
and every species of tree.[246] While, then, without much injury to the
younger growths, the native forest will bear several "cuttings over" in
a generation--for the increasing value of lumber brings into use, every
four or five years, a quality of timber which had been before rejected
as unmarketable--a fire may render the declivity of a mountain
unproductive for a century.[247]
_American Forest Trees._
The remaining forests of the Northern States and of Canada no longer
boast the mighty pines which almost rivalled the gigantic Sequoia of
California; and the growth of the larger forest trees is so slow, after
they have attained to a certain size, that if every pine and oak were
spared for two centuries, the largest now standing would not reach the
stature of hundreds recorded to have been cut within two or three
generations.[248] Dr. Williams, who wrote about sixty years ago, states
the following as the dimensions of "such trees as are esteemed large
ones of their kind in that part of America" [Vermont], qualifying his
account with the remark that his measurements "do not denote the
greatest which nature has produced of their particular species, but the
greatest which are to be found in most of our towns."
Diameter. Height.
Pine, 6 feet, 247 feet.
Maple, 5 " 9 inches, }
Buttonwood, 5 " 6 " }
Elm, 5 " }
Hemlock, 4 " 9 " }
Oak, 4 " } From 100 to 200 feet.
Basswood, 4 " }
Ash, 4 " }
Birch, 4 " }
He adds a note saying that a white pine was cut in Dunstable, New
Hampshire, in the year 1736, the diameter of which was seven feet and
eight inches. Dr. Dwight says that a fallen pine in Connecticut was
found to measure two hundred and forty-seven feet in height, and adds:
"A few years since, such trees were in great numbers along the northern
parts of Connecticut River." In another letter, he speaks of the white
pine as "frequently six feet in diameter, and two hundred and fifty feet
in height," and states that a pine had been cut in Lancaster, New
Hampshire, which measured two hundred and sixty-four feet. Emerson wrote
in 1846: "Fifty years ago, several trees growing on rather dry land in
Blandford, Massachusetts, measured, after they were felled, two hundred
and twenty-three feet. All these trees are surpassed by a pine felled at
Hanover, New Hampshire, about a hundred years ago, and described as
measuring two hundred and seventy-four feet.[249]
These descriptions, it will be noticed, apply to trees cut from sixty to
one hundred years since. Persons, whom observation has rendered familiar
with the present character of the American forest, will be struck with
the smallness of the diameter which Dr. Williams and Dr. Dwight ascribe
to trees of such extraordinary height. Individuals of the several
species mentioned in Dr. Williams's table, are now hardly to be found in
the same climate, exceeding one half or at most two thirds of the height
which he assigns to them; but, except in the case of the oak and the
pine, the diameter stated by him would not be thought very extraordinary
in trees of far less height, now standing. Even in the species I have
excepted, those diameters, with half the heights of Dr. Williams, might
perhaps be paralleled at the present time; and many elms, transplanted,
at a diameter of six inches, within the memory of persons still living,
measure six, and sometimes even seven feet through. For this change
in the growth of forest trees there are two reasons: the one is,
that the great commercial value of the pine and the oak have
caused the destruction of all the best--that is, the tallest and
straightest--specimens of both; the other, that the thinning of the
woods by the axe of the lumberman has allowed the access of light and
heat and air to trees of humbler worth and lower stature, which have
survived their more towering brethren. These, consequently, have been
able to expand their crowns and swell their stems to a degree not
possible so long as they were overshadowed and stifled by the lordly oak
and pine. While, therefore, the New England forester must search long
before he finds a pine
fit to be the mast
Of some great ammiral,
beeches and elms and birches, as sturdy as the mightiest of their
progenitors, are still no rarity.[250]
Another evil, sometimes of serious magnitude, which attends the
operations of the lumberman, is the injury to the banks of rivers from
the practice of floating. I do not here allude to rafts, which, being
under the control of those who navigate them, may be so guided as to
avoid damage to the shore, but to masts, logs, and other pieces of
timber singly intrusted to the streams, to be conveyed by their currents
to sawmill ponds, or to convenient places for collecting them into
rafts. The lumbermen usually haul the timber to the banks of the rivers
in the winter, and when the spring floods swell the streams and break up
the ice, they roll the logs into the water, leaving them to float down
to their destination. If the transporting stream is too small to furnish
a sufficient channel for this rude navigation, it is sometimes dammed
up, and the timber collected in the pond thus formed above the dam. When
the pond is full, a sluice is opened, or the dam is blown up or
otherwise suddenly broken, and the whole mass of lumber above it is
hurried down with the rolling flood. Both of these modes of proceeding
expose the banks of the rivers employed as channels of flotation to
abrasion,[251] and in some of the American States it has been found
necessary to protect, by special legislation, the lands through which
they flow from the serious injury sometimes received through the
practices I have described.[252]
_Special Causes of the Destruction of European Woods._
The causes of forest waste thus far enumerated are more or less common
to both continents; but in Europe extensive woods have, at different
periods, been deliberately destroyed by fire or the axe, because they
afforded a retreat to enemies, robbers, and outlaws, and this practice
is said to have been resorted to in the Mediterranean provinces of
France as recently as the time of Napoleon I.[253] The severe and even
sanguinary legislation, by which some of the governments of mediæval
Europe, as well as of earlier ages, protected the woods, was dictated by
a love of the chase, or the fear of a scarcity of fuel and timber. The
laws of almost every European state more or less adequately secure the
permanence of the forest; and I believe Spain is the only European land
which has not made some public provision for the protection and
restoration of the woods--the only country whose people systematically
war upon the garden of God.[254]
_Royal Forests and Game Laws._
The French authors I have quoted, as well as many other writers of the
same nation, refer to the French Revolution as having given a new
impulse to destructive causes which were already threatening the total
extermination of the woods.[255] The general crusade against the
forests, which accompanied that important event, is to be ascribed, in a
considerable degree, to political resentments. The forest codes of the
mediæval kings, and the local "coutumes" of feudalism contained many
severe and even inhuman provisions, adopted rather for the preservation
of game than from any enlightened views of the more important functions
of the woods. Ordericus Vitalis informs us that William the Conqueror
destroyed sixty parishes, and drove out their inhabitants, in order that
he might turn their lands into a forest,[256] to be reserved as a
hunting ground for himself and his posterity, and he punished with death
the killing of a deer, wild boar, or even a hare. His successor, William
Rufus, according to the _Histoire des Ducs de Normandie et des Rois
d'Angleterre_, p. 67, "was hunting one day in a new forest, which he had
caused to be made out of eighteen parishes that he had destroyed, when,
by mischance, he was killed by an arrow wherewith Tyreus de Rois [Sir
Walter Tyrell] thought to slay a beast, but missed the beast, and slew
the king, who was beyond it. And in this very same forest, his brother
Richard ran so hard against a tree that he died of it. And men commonly
said that these things were because they had so laid waste and taken the
said parishes."
These barbarous acts, as Bonnemère observes,[257] were simply the
transfer of the customs of the French kings, of their vassals, and even
of inferior gentlemen, to conquered England. "The death of a hare," says
our author, "was a hanging matter, the murder of a plover a capital
crime. Death was inflicted on those who spread nets for pigeons;
wretches who had drawn a bow upon a stag were to be tied to the animal
alive; and among the seigniors it was a standing excuse for having
killed game on forbidden ground, that they aimed at a serf." The feudal
lords enforced these codes with unrelenting rigor, and not unfrequently
took the law into their own hands. In the time of Louis IX, according to
William of Nangis, "three noble children, born in Flanders, who were
sojourning at the abbey of St. Nicholas in the Wood, to learn the speech
of France, went out into the forest of the abbey, with their bows and
iron-headed arrows, to disport them in shooting hares, chased the game,
which they had started in the wood of the abbey, into the forest of
Enguerrand, lord of Coucy, and were taken by the sergeants which kept
the wood. When the fell and pitiless Sir Enguerrand knew this, he had
the children straightway hanged without any manner of trial."[258] The
matter being brought to the notice of good King Louis, Sir Enguerrand
was summoned to appear, and, finally, after many feudal shifts and
dilatory pleas, brought to trial before Louis himself and a special
council. Notwithstanding the opposition of the other seigniors, who, it
is needless to say, spared no efforts to save a peer, probably not a
greater criminal than themselves, the king was much inclined to inflict
the punishment of death on the proud baron. "If he believed," said he,
"that our Lord would be as well content with hanging as with pardoning,
he would hang Sir Enguerrand in spite of all his barons;" but noble and
clerical interests unfortunately prevailed. The king was persuaded to
inflict a milder retribution, and the murderer was condemned to pay ten
thousand livres in coin, and to "build for the souls of the three
children two chapels wherein mass should be said every day."[259] The
hope of shortening the purgatorial term of the young persons, by the
religious rites to be celebrated in the chapels, was doubtless the
consideration which operated most powerfully on the mind of the king;
and Europe lost a great example for the sake of a mass.
The desolation and depopulation, resulting from the extension of the
forest and the enforcement of the game laws, induced several of the
French kings to consent to some relaxation of the severity of these
latter. Francis I, however, revived their barbarous provisions, and,
according to Bonnemère, even so good a monarch as Henry IV reënacted
them, and "signed the sentence of death upon peasants guilty of having
defended their fields against devastation by wild beasts." "A fine of
twenty livres," he continues, "was imposed on every one shooting at
pigeons, which, at that time, swooped down by thousands upon the
new-sown fields and devoured the seed. But let us count even this a
progress, for we have seen that the murder of a pigeon had been a
capital crime."[260]
Not only were the slightest trespasses on the forest domain--the cutting
of an oxgoad, for instance--severely punished, but game animals were
still sacred when they had wandered from their native precincts and were
ravaging the fields of the peasantry. A herd of deer or of wild boars
often consumed or trod down a harvest of grain, the sole hope of the
year for a whole family; and the simple driving out of such animals from
this costly pasturage brought dire vengeance on the head of the rustic,
who had endeavored to save his children's bread from their voracity. "At
all times," says Paul Louis Courier, speaking in the name of the
peasants of Chambord, in the "Simple Discours," "the game has made war
upon us. Paris was blockaded eight hundred years by the deer, and its
environs, now so rich, so fertile, did not yield bread enough to support
the gamekeepers."[261]
In the popular mind, the forest was associated with all the abuses of
feudalism, and the evils the peasantry had suffered from the legislation
which protected both it and the game it sheltered, blinded them to the
still greater physical mischiefs which its destruction was to entail
upon them. No longer protected by law, the crown forests and those of
the great lords were attacked with relentless fury, unscrupulously
plundered and wantonly laid waste, and even the rights of property in
small private woods were no longer respected.[262] Various absurd
theories, some of which are not even yet exploded, were propagated with
regard to the economical advantages of converting the forest into
pasture and ploughland, its injurious effects upon climate, health,
facility of internal communication, and the like. Thus resentful memory
of the wrongs associated with the forest, popular ignorance, and the
cupidity of speculators cunning enough to turn these circumstances to
profitable account, combined to hasten the sacrifice of the remaining
woods, and a waste was produced which hundreds of years and millions of
treasure will hardly repair.
_Small Forest Plants, and Vitality of Seed._
Another function of the woods to which I have barely alluded deserves a
fuller notice than can be bestowed upon it in a treatise the scope of
which is purely economical. The forest is the native habitat of a large
number of humbler plants, to the growth and perpetuation of which its
shade, its humidity, and its vegetable mould appear to be indispensable
necessities.[263] We cannot positively say that the felling of the
woods in a given vegetable province would involve the final extinction
of the smaller plants which are found only within their precincts. Some
of these, though not naturally propagating themselves in the open
ground, may perhaps germinate and grow under artificial stimulation and
protection, and finally become hardy enough to maintain an independent
existence in very different circumstances from those which at present
seem essential to their life.
Besides this, although the accounts of the growth of seeds, which have
lain for ages in the ashy dryness of Egyptian catacombs, are to be
received with great caution, or, more probably, to be rejected
altogether, yet their vitality seems almost imperishable while they
remain in the situations in which nature deposits them. When a forest
old enough to have witnessed the mysteries of the Druids is felled,
trees of other species spring up in its place; and when they, in their
turn, fall before the axe, sometimes even as soon as they have spread
their protecting shade over the surface, the germs which their
predecessors had shed years, perhaps centuries before, sprout up, and in
due time, if not choked by other trees belonging to a later stage in the
order of natural succession, restore again the original wood. In these
cases, the seeds of the new crop may often have been brought by the
wind, by birds, by quadrupeds, or by other causes; but, in many
instances, this explanation is not probable.
When newly cleared ground is burnt over in the United States, the ashes
are hardly cold before they are covered with a crop of fire weed, a tall
herbaceous plant, very seldom seen growing under other circumstances,
and often not to be found for a distance of many miles from the
clearing. Its seeds, whether the fruit of an ancient vegetation or newly
sown by winds or birds, require either a quickening by a heat which
raises to a certain high point the temperature of the stratum where they
lie buried, or a special pabulum furnished only by the combustion of the
vegetable remains that cover the ground in the woods. Earth brought up
from wells or other excavations soon produces a harvest of plants often
very unlike those of the local flora.
Moritz Wagner, as quoted by Wittwer,[264] remarks in his description of
Mount Ararat: "A singular phenomenon to which my guide drew my attention
is the appearance of several plants on the earth-heaps left by the last
catastrophe [an earthquake], which grow nowhere else on the mountain,
and had never been observed in this region before. The seeds of these
plants were probably brought by birds, and found in the loose, clayey
soil remaining from the streams of mud, the conditions of growth which
the other soil of the mountain refused them." This is probable enough,
but it is hardly less so that the flowing mud brought them up to the
influence of air and sun, from depths where a previous convulsion had
buried them ages before. Seeds of small sylvan plants, too deeply buried
by successive layers of forest foliage and the mould resulting from its
decomposition to be reached by the plough when the trees are gone and
the ground brought under cultivation, may, if a wiser posterity replants
the wood which sheltered their parent stems, germinate and grow, after
lying for generations in a state of suspended animation.
Darwin says: "In Staffordshire, on the estate of a relation, where I had
ample means of investigation, there was a large and extremely barren
heath, which had never been touched by the hand of man, but several
hundred acres of exactly the same nature had been enclosed twenty-five
years previously and planted with Scotch fir. The change in the native
vegetation of the planted part of the heath was most remarkable--more
than is generally seen in passing from one quite different soil to
another; not only the proportional numbers of the heath plants were
wholly changed, but _twelve species_ of plants (not counting grasses and
sedges) flourished in the plantation which could not be found on the
heath."[265] Had the author informed us that these twelve plants
belonged to a species whose seeds enter into the nutriment of the birds
which appeared with the young wood, we could easily account for their
presence in the soil; but he says distinctly that the birds were of
insectivorous species, and it therefore seems more probable that the
seeds had been deposited when an ancient forest protected the growth of
the plants which bore them, and that they sprang up to new life when a
return of favorable conditions awaked them from a sleep of centuries.
Darwin indeed says that the heath "had never been touched by the hand
of man." Perhaps not, after it became a heath; but what evidence is
there to control the general presumption that this heath was preceded by
a forest, in whose shade the vegetables which dropped the seeds in
question might have grown?[266]
Although, therefore, the destruction of a wood and the reclaiming of the
soil to agricultural uses suppose the death of its smaller dependent
flora, these revolutions do not exclude the possibility of its
resurrection. In a practical view of the subject, however, we must admit
that when the woodman fells a tree he sacrifices the colony of humbler
growths which had vegetated under its protection. Some wood plants are
known to possess valuable medicinal properties, and experiment may show
that the number of these is greater than we now suppose. Few of them,
however, have any other economical value than that of furnishing a
slender pasturage to cattle allowed to roam in the woods; and even this
small advantage is far more than compensated by the mischief done to the
young trees by browsing animals. Upon the whole, the importance of this
class of vegetables, as physic or as food, is not such as to furnish a
very telling popular argument for the conservation of the forest as a
necessary means of their perpetuation. More potent remedial agents may
supply their place in the _materia medica_, and an acre of grass land
yields more nutriment for cattle than a range of a hundred acres of
forest. But he whose sympathies with nature have taught him to feel that
there is a fellowship between all God's creatures; to love the brilliant
ore better than the dull ingot, iodic silver and crystallized red copper
better than the shillings and the pennies forged from them by the
coiner's cunning; a venerable oak tree than the brandy cask whose staves
are split out from its heart wood; a bed of anemones, hepaticas, or wood
violets than the leeks and onions which he may grow on the soil they
have enriched and in the air they made fragrant--he who has enjoyed that
special training of the heart and intellect which can be acquired only
in the unviolated sanctuaries of nature, "where man is distant, but God
is near"--will not rashly assert his right to extirpate a tribe of
harmless vegetables, barely because their products neither tickle his
palate nor fill his pocket; and his regret at the dwindling area of the
forest solitude will be augmented by the reflection that the nurselings
of the woodland perish with the pines, the oaks, and the beeches that
sheltered them.[267]
Although, as I have said, birds do not frequent the deeper recesses of
the wood,[268] yet a very large proportion of them build their nests in
trees, and find in their foliage and branches a secure retreat from the
inclemencies of the seasons and the pursuit of the reptiles and
quadrupeds which prey upon them. The borders of the forests are vocal
with song; and when the gray morning calls the creeping things of the
earth out of their night cells, it summons from the neighboring wood
legions of their winged enemies, which swoop down upon the fields to
save man's harvests by devouring the destroying worm, and surprising the
lagging beetle in his tardy retreat to the dark cover where he lurks
through the hours of daylight.
The insects most injurious to rural industry do not multiply in or near
the woods. The locust, which ravages the East with its voracious armies,
is bred in vast open plains which admit the full heat of the sun to
hasten the hatching of the eggs, gather no moisture to destroy them, and
harbor no bird to feed upon the larvæ.[269] It is only since the felling
of the forests of Asia Minor and Cyrene that the locust has become so
fearfully destructive in those countries; and the grasshopper, which now
threatens to be almost as great a pest to the agriculture of some North
American soils, breeds in seriously injurious numbers only where a wide
extent of surface is bare of woods.
_Utility of the Forest._
In most parts of Europe, the woods are already so nearly extirpated that
the mere protection of those which now exist is by no means an adequate
remedy for the evils resulting from the want of them; and besides, as I
have already said, abundant experience has shown that no legislation can
secure the permanence of the forest in private hands. Enlightened
individuals in most European states, governments in others, have made
very extensive plantations,[270] and France has now set herself
energetically at work to restore the woods in the southern provinces,
and thereby to prevent the utter depopulation and waste with which that
once fertile soil and delicious climate are threatened.
The objects of the restoration of the forest are as multifarious as the
motives that have led to its destruction, and as the evils which that
destruction has occasioned. It is hoped that the planting of the
mountains will diminish the frequency and violence of river inundations,
prevent the formation of torrents, mitigate the extremes of atmospheric
temperature, humidity, and precipitation, restore dried-up springs,
rivulets, and sources of irrigation, shelter the fields from chilling
and from parching winds, prevent the spread of miasmatic effluvia, and,
finally, furnish an inexhaustible and self-renewing supply of a material
indispensable to so many purposes of domestic comfort, to the successful
exercise of every art of peace, every destructive energy of war.[271]
But our enumeration of the uses of trees is not yet complete. Besides
the influence of the forest, in mountain ranges, as a means of
preventing the scooping out of ravines and the accumulations of water
which fill them, trees subserve a valuable purpose, in lower positions,
as barriers against the spread of floods and of the material they
transport with them; but this will be more appropriately considered in
the chapter on the waters; and another very important use of trees, that
of fixing movable sand-dunes, and reclaiming them to profitable
cultivation, will be pointed out in the chapter on the sands.
The vast extension of railroads, of manufactures and the mechanical
arts, of military armaments, and especially of the commercial fleets and
navies of Christendom within the present century, has greatly augmented
the demand for wood,[272] and, but for improvements in metallurgy which
have facilitated the substitution of iron for that material, the last
twenty-five years would almost have stripped Europe of her only
remaining trees fit for such uses.[273] The walnut trees alone felled in
Europe within two years to furnish the armies of America with
gunstocks, would form a forest of no inconsiderable extent.[274]
_The Forests of Europe._
Mirabeau estimated the forests of France in 1750 at seventeen millions
of hectares [42,000,000 acres]; in 1860 they were reduced to eight
millions [19,769,000 acres]. This would be at the rate of 82,000
hectares [202,600 acres] per year. Troy, from whose valuable pamphlet,
_Étude sur le Reboisement des Montagnes_, I take these statistical
details, supposes that Mirabeau's statement may have been an extravagant
one, but it still remains certain that the waste has been enormous; for
it is known that, in some departments, that of Ariège, for instance,
clearing has gone on during the last half century at the rate of three
thousand acres a year,[275] and in all parts of the empire trees have
been felled faster than they have grown. The total area of France,
excluding Savoy, is about one hundred and thirty-one millions of acres.
The extent of forest supposed by Mirabeau would be about thirty-two per
cent. of the whole territory.[276] In a country and a climate where the
conservative influences of the forest are so necessary as in France,
trees must cover a large surface and be grouped in large masses, in
order to discharge to the best advantage the various functions assigned
to them by nature. The consumption of wood is rapidly increasing in that
empire, and a large part of its territory is mountainous, sterile, and
otherwise such in character or situation that it can be more profitably
devoted to the growth of wood than to any agricultural use. Hence it is
evident that the proportion of forest in 1750, taking even Mirabeau's
large estimate, was not very much too great for permanent maintenance,
though doubtless the distribution was so unequal that it would have been
sound policy to fell the woods and clear land in some provinces, while
large forests should have been planted in others.[277] During the
period in question, France neither exported manufactured wood or rough
timber, nor derived important collateral advantages of any sort from the
destruction of her forests. She is consequently impoverished and
crippled to the extent of the difference between what she actually
possesses of wooded surface and what she ought to have retained.
Italy and Spain are bared of trees in a greater degree than France, and
even Russia, which we habitually consider as substantially a forest
country, is beginning to suffer seriously for want of wood. Jourdier, as
quoted by Clavé, observes: "Instead of a vast territory with immense
forests, which we expect to meet, one sees only scattered groves thinned
by the wind or by the axe of the _moujik_, grounds cut over and more or
less recently cleared for cultivation. There is probably not a single
district in Russia which has not to deplore the ravages of man or of
fire, those two great enemies of Muscovite sylviculture. This is so
true, that clear-sighted men already foresee a crisis which will become
terrible, unless the discovery of great deposits of some new
combustible, as pit coal or anthracite, shall diminish its evils."[278]
Germany, from character of surface and climate, and from the attention
which has long been paid in all the German States to sylviculture, is,
taken as a whole, in a far better condition in this respect than its
more southern neighbors; but in the Alpine provinces of Bavaria and
Austria, the same improvidence which marks the rural economy of the
corresponding districts of Switzerland, Italy, and France, is producing
effects hardly less disastrous. As an instance of the scarcity of fuel
in some parts of the territory of Bavaria, where, not long since, wood
abounded, I may mention the fact that the water of salt springs is, in
some instances, conveyed to the distance of sixty miles, in iron pipes,
to reach a supply of fuel for boiling it down.[279]
_Forests of the United States and Canada._
The vast forests of the United States and Canada cannot long resist the
improvident habits of the backwoodsman and the increased demand for
lumber. According to the census of the former country for 1860, which
gives returns of the "sawed and planed lumber" alone, timber for
framing and for a vast variety of mechanical purposes being omitted
altogether, the value of the former material prepared for market in the
United States was, in 1850, $58,521,976; in 1860, $95,912,286. The
quantity of unsawed lumber is not likely to have increased in the same
proportion, because comparatively little is exported in that condition,
and because masonry is fast taking the place of carpentry in building,
and stone, brick, and iron are used instead of timber more largely than
they were ten years ago. Still a much greater quantity of unsawed lumber
must have been marketed in 1860 than in 1850. It must further be
admitted that the price of lumber rose considerably between those dates,
and consequently that the increase in quantity is not to be measured by
the increase in pecuniary value. Perhaps this rise of prices may even be
sufficient to make the entire difference between the value of "sawed and
planed lumber" produced in the ten years in question by the six New
England States (21 per cent.), and the six Middle States (15 per cent.);
but the amount produced by the Western and by the Southern States had
doubled, and that returned from the Pacific States and Territories had
trebled in value in the same interval, so that there was certainly, in
those States, a large increase in the actual quantity prepared for sale.
I greatly doubt whether any one of the American States, except, perhaps,
Oregon, has, at this moment, more woodland than it ought permanently to
preserve, though, no doubt, a different distribution of the forests in
all of them might be highly advantageous. It is a great misfortune to
the American Union that the State Governments have so generally disposed
of their original domain to private citizens. It is true that public
property is not sufficiently respected in the United States; and it is
also true that, within the memory of almost every man of mature age,
timber was of so little value in that country, that the owners of
private woodlands submitted, almost without complaint, to what would be
regarded elsewhere as very aggravated trespasses upon them.[280] Under
such circumstances, it is difficult to protect the forest, whether it
belong to the state or to individuals. Property of this kind would be
subject to much plunder, as well as to frequent damage by fire. The
destruction from these causes would, indeed, considerably lessen, but
would not wholly annihilate the climatic and geographical influences of
the forest, or ruinously diminish its value as a regular source of
supply of fuel and timber. For prevention of the evils upon which I have
so long dwelt, the American people must look to the diffusion of general
intelligence on this subject, and to the enlightened self interest, for
which they are remarkable, not to the action of their local or general
legislatures. Even in France, government has moved with too slow and
hesitating a pace, and preventive measures do not yet compensate
destructive causes. The judicious remarks of Troy on this point may well
be applied to other countries than France, other measures of public
policy than the preservation of the woods. "To move softly," says he,
"is to commit the most dangerous, the most unpardonable of imprudences;
it diminishes the prestige of authority; it furnishes a triumph to the
sneerer and the incredulous; it strengthens opposition and encourages
resistance; it ruins the administration in the opinion of the people,
weakens its power and depresses its courage."[281]
_The Economy of the Forest._
The legislation of European states upon sylviculture, and the practice
of that art, divide themselves into two great branches--the preservation
of existing forests, and the creation of new. From the long operation of
causes already set forth, what is understood in America and other new
countries by the "primitive forest," no longer exists in the territories
which were the seats of ancient civilization and empire, except upon a
small scale, and in remote and almost inaccessible glens quite out of
the reach of ordinary observation. The oldest European woods, indeed,
are native, that is, sprung from self-sown seed, or from the roots of
trees which have been felled for human purposes; but their growth has
been controlled, in a variety of ways, by man and by domestic animals,
and they always present more or less of an artificial character and
arrangement. Both they and planted forests, which, though certainly not
few, are of recent date in Europe, demand, as well for protection as for
promotion of growth, a treatment different in some respects from that
which would be suited to the character and wants of the virgin wood.
On this latter branch of the subject, experience and observation have
not yet collected a sufficient stock of facts to serve for the
construction of a complete system of sylviculture; but the management of
the forest as it exists in France--the different zones and climates of
which country present many points of analogy with those of the United
States and some of the British colonies--has been carefully studied, and
several manuals of practice have been prepared for the foresters of that
empire. I believe the best of these is the _Cours Élémentaire de Culture
des Bois créé à l'École Forestière de Nancy, par M. Lorentz, complété,
et publié par A. Parade_, with a supplement under the title of _Cours
d'Aménagement des Forêts, par Henri Nanquette_. The _Études sur
l'Économie Forestière, par Jules Clavé_, which I have often quoted,
presents a great number of interesting views on this subject, and well
deserves to be translated for the use of the English and American
reader; but it is not designed as a practical guide, and it does not
profess to be sufficiently specific in its details to serve that
purpose. Notwithstanding the difference of conditions between the
aboriginal and the trained forest, the judicious observer who aims at
the preservation of the former will reap much instruction from the
treatises I have cited, and I believe he will be convinced that the
sooner a natural wood is brought into the state of an artificially
regulated one, the better it is for all the multiplied interests which
depend on the wise administration of this branch of public
economy.[282]
One consideration bearing on this subject has received less attention
than it merits, because most persons interested in such questions have
not opportunities for the comparison I refer to. I mean the great
general superiority of cultivated timber to that of strictly spontaneous
growth. I say _general_ superiority, because there are exceptions to the
rule. The white pine, _Pinus strobus_, for instance, and other trees of
similar character and uses, require, for their perfect growth, a density
of forest vegetation around them, which protects them from too much
agitation by wind, and from the persistence of the lateral branches
which fill the wood with knots. A pine which has grown under those
conditions possesses a tall, straight stem, admirably fitted for masts
and spars, and, at the same time, its wood is almost wholly free from
knots, is regular in annular structure, soft and uniform in texture,
and, consequently, superior to almost all other timber for joinery. If,
while a large pine is spared, the broad-leaved or other smaller trees
around it are felled, the swaying of the tree from the action of the
wind mechanically produces separations between the layers of annual
growth, and greatly diminishes the value of the timber.
The same defect is often observed in pines which, from some accident of
growth, have much overtopped their fellows in the virgin forest. The
white pine, growing in the fields, or in open glades in the woods, is
totally different from the true forest tree, both in general aspect and
in quality of wood. Its stem is much shorter, its top less tapering, its
foliage denser and more inclined to gather into tufts, its branches more
numerous and of larger diameter, its wood shows much more distinctly the
divisions of annual growth, is of coarser grain, harder and more
difficult to work into mitre joints. Intermixed with the most valuable
pines in the American forests, are met many trees of the character I
have just described. The lumbermen call them "saplings," and generally
regard them as different in species from the true white pine, but
botanists are unable to establish a distinction between them, and as
they agree in almost all respects with trees grown in the open grounds
from known white-pine seedlings, I believe their peculiar character is
due to unfavorable circumstances in their early growth. The pine, then,
is an exception to the general rule as to the inferiority of the forest
to the open-ground tree. The pasture oak and pasture beech, on the
contrary, are well known to produce far better timber than those grown
in the woods, and there are few trees to which the remark is not equally
applicable.[283]
Another advantage of the artificially regulated forest is, that it
admits of such grading of the ground as to favor the retention or
discharge of water at will, while the facilities it affords for
selecting and duly proportioning, as well as properly spacing, the trees
which compose it, are too obvious to require to be more than hinted at.
In conducting these operations, we must have a diligent eye to the
requirements of nature, and must remember that a wood is not an
arbitrary assemblage of trees to be selected and disposed according to
the caprice of its owner. "A forest," says Clavé, "is not, as is often
supposed, a simple collection of trees succeeding each other in long
perspective, without bond of union, and capable of isolation from each
other; it is, on the contrary, a whole, the different parts of which are
interdependent upon each other, and it constitutes, so to speak, a true
individuality. Every forest has a special character, determined by the
form of the surface it grows upon, the kinds of trees that compose it,
and the manner in which they are grouped."[284]
_European and American Trees compared._
The woods of North America are strikingly distinguished from those of
Europe by the vastly greater variety of species they contain. According
to Clavé, there are in "France and in most parts of Europe" only about
twenty forest trees, five or six of which are spike-leaved and resinous,
the remainder broad-leaved."[285] Our author, however, doubtless means
genera, though he uses the word _espèces_. Rossmässler enumerates
fifty-seven species of forest trees as found in Germany, but some of
these are mere shrubs, some are fruit and properly garden trees, and
some others are only varieties of familiar species. The valuable manual
of Parade describes about the same number, including, however, two of
American origin--the locust, _Robinia pseudacacia_, and the Weymouth or
white pine, _Pinus strobus_--and the cedar of Lebanon from Asia, though
it is indigenous in Algeria also. We may then safely say that Europe
does not possess above forty or fifty trees of such economical value as
to be worth the special care of the forester, while the oak alone
numbers not less than thirty species in the United States,[286] and some
other North American genera are almost equally diversified.[287]
Few European trees, except those bearing edible fruit, have been
naturalized in the United States, while the American forest flora has
made large contributions to that of Europe. It is a very poor taste
which has led to the substitution of the less picturesque European for
the graceful and majestic American elm, in some public grounds in the
United States. On the other hand, the European mountain ash--which in
beauty and healthfulness of growth is superior to our own--the horse
chestnut, and the abele, or silver poplar, are valuable additions to the
ornamental trees of North America. The Swiss arve or zirbelkiefer,
_Pinus cembra_, which yields a well-flavored edible seed and furnishes
excellent wood for carving, the umbrella pine which also bears a seed
agreeable to the taste, and which, from the color of its foliage and the
beautiful form of its dome-like crown, is among the most elegant of
trees, the white birch of Central Europe, with its pendulous branches
almost rivalling those of the weeping willow in length, flexibility, and
gracefulness of fall, and, especially, the "cypresse funerall," might be
introduced into the United States with great advantage to the landscape.
The European beech and chestnut furnish timber of far better quality
than that of their American congeners. The fruit of the European
chestnut, though inferior to the American in flavor, is larger, and is
an important article of diet among the French and Italian peasantry. The
walnut of Europe, though not equal to some of the American species in
beauty of growth or of wood, or to others in strength and elasticity of
fibre, is valuable for its timber and its oil.[288] The maritime pine,
which has proved of such immense use in fixing drifting sands in France,
may perhaps be better adapted to this purpose than any of the pines of
the New World, and it is of great importance for its turpentine, resin,
and tar. The épicéa, or common fir, _Abies picea_, _Abies excelsa_,
_Picea excelsa_, abundant in the mountains of France and the contiguous
country, is known for its product, Burgundy pitch, and, as it flourishes
in a greater variety of soil and climate than almost any other
spike-leaved tree, it might be well worth transplantation.[289] The cork
oak has been introduced into the United States, I believe, and would
undoubtedly thrive in the Southern section of the Union.[290]
In the walnut, the chestnut, the cork oak, the mulberry, the olive, the
orange, the lemon, the fig, and the multitude of other trees which, by
their fruit, or by other products, yield an annual revenue, nature has
provided Southern Europe with a partial compensation for the loss of
the native forest. It is true that these trees, planted as most of them
are at such distances as to admit of cultivation, or of the growth of
grass among them, are but an inadequate substitute for the thick and
shady wood; but they perform to a certain extent the same offices of
absorption and transpiration, they shade the surface of the ground, they
serve to break the force of the wind, and on many a steep declivity,
many a bleak and barren hillside, the chestnut binds the soil together
with its roots, and prevents tons of earth and gravel from washing down
upon the fields and the gardens. Fruit trees are not wanting, certainly,
north of the Alps. The apple, the pear, and the prune are important in
the economy both of man and of nature, but they are far less numerous in
Switzerland and Northern France than are the trees I have mentioned in
Southern Europe, both because they are in general less remunerative, and
because the climate, in higher latitudes, does not permit the free
introduction of shade trees into grounds occupied for agricultural
purposes.[291]
The multitude of species, intermixed as they are in their spontaneous
growth, gives the American forest landscape a variety of aspect not
often seen in the woods of Europe, and the gorgeous tints, which nature
repeats from the dying dolphin to paint the falling leaf of the American
maples, oaks, and ash trees, clothe the hillsides and fringe the
watercourses with a rainbow splendor of foliage, unsurpassed by the
brightest groupings of the tropical flora. It must be admitted, however,
that both the northern and the southern declivities of the Alps exhibit
a nearer approximation to this rich and multifarious coloring of
autumnal vegetation than most American travellers in Europe are willing
to allow; and, besides, the small deciduous shrubs which often carpet
the forest glades of these mountains are dyed with a ruddy and orange
glow, which, in the distant landscape, is no mean substitute for the
scarlet and crimson and gold and amber of the transatlantic woodland.
No American evergreen known to me resembles the umbrella pine
sufficiently to be a fair object of comparison with it.[292] A cedar,
very common above the Highlands on the Hudson, is extremely like the
cypress, straight, slender, with erect, compressed ramification, and
feathered to the ground, but its foliage is neither so dark nor so
dense, the tree does not attain the majestic height of the cypress, nor
has it the lithe flexibility of that tree. In mere shape, the Lombardy
poplar nearly resembles this latter, but it is almost a profanation to
compare the two, especially when they are agitated by the wind; for
under such circumstances, the one is the most majestic, the other the
most ungraceful, or--if I may apply such an expression to anything but
human affectation of movement--the most awkward of trees. The poplar
trembles before the blast, flutters, struggles wildly, dishevels its
foliage, gropes around with its feeble branches, and hisses as in
impotent passion. The cypress gathers its limbs still more closely to
its stem, bows a gracious salute rather than an humble obeisance to the
tempest, bends to the wind with an elasticity that assures you of its
prompt return to its regal attitude, and sends from its thick leaflets a
murmur like the roar of the far-off ocean.
The cypress and the umbrella pine are not merely conventional types of
the Italian landscape. They are essential elements in a field of rural
beauty which can be seen in perfection only in the basin of the
Mediterranean, and they are as characteristic of this class of scenery
as the date palm is of the oases of the desert. There is, however, this
difference: a single cypress or pine is often enough to shed beauty over
a wide area; the palm is a social tree, and its beauty is not so much
that of the individual as of the group. The frequency of the cypress and
the pine--combined with the fact that the other trees of Southern Europe
which most interest a stranger from the north, the orange and the lemon,
the cork oak, the ilex, the myrtle, and the laurel, are evergreens--goes
far to explain the beauty of the winter scenery of Italy. Indeed it is
only in the winter that a tourist who confines himself to wheel
carriages and high roads can acquire any notion of the face of the
earth, and form any proper geographical image of that country. At other
seasons, not high walls only, but equally impervious hedges, and now,
unhappily, acacias thickly planted along the railway routes, confine the
view so completely, that the arch of a tunnel, or a night cap over the
traveller's eyes, is scarcely a more effectual obstacle to the
gratification of his curiosity.[293]
_Sylviculture._
The art, or, as the Continental foresters call it, the science of
sylviculture has been so little pursued in England and America, that its
nomenclature has not been introduced into the English vocabulary, and I
shall not be able to describe its processes with technical propriety of
language, without occasionally borrowing a word from the forest
literature of France and Germany. A full discussion of the methods of
sylviculture would, indeed, be out of place in a work like the present,
but the almost total want of conveniently accessible means of
information on the subject, in English-speaking countries, will justify
me in presenting it with somewhat more of detail than would otherwise be
pertinent.
The two best known methods are those distinguished as the _taillis_,
copse or coppice treatment,[294] and the _futaie_, for which I find no
English equivalent, but which may not inappropriately be called the
_full-growth_ system. A _taillis_, copse, or coppice, is a wood composed
of shoots from the roots of trees previously cut for fuel and timber.
The shoots are thinned out from time to time, and finally cut, either
after a fixed number of years, or after the young trees have attained to
certain dimensions, their roots being then left to send out a new
progeny as before. This is the cheapest method of management, and
therefore the best wherever the price of labor and of capital bears a
high proportion to that of land and of timber; but it is essentially a
wasteful economy. If the woodland is, in the first place, completely cut
over, as is found most convenient in practice, the young shoots have
neither the shade nor the protection from wind so important to forest
growth, and their progress is comparatively slow, while, at the same
time, the thick clumps they form choke the seedlings that may have
sprouted near them. If domestic animals of any species are allowed to
roam in the wood, they browse upon the terminal buds and the tender
branches, thereby stunting, if they do not kill, the young trees, and
depriving them of all beauty and vigor of growth. The evergreens, once
cut, do not shoot up again,[295] and the mixed character of the
forest--in many respects an important advantage, if not an indispensable
condition of growth--is lost;[296] and besides this, large wood of any
species cannot be grown in this method, because trees which shoot from
decaying stumps and their dying roots, become hollow or otherwise
unsound before they acquire their full dimensions. A more fatal
objection still, is, that the roots of trees will not bear more than two
or three, or at most four cuttings of their shoots before their vitality
is exhausted, and the wood can then be restored only by replanting
entirely. The period of cutting coppices varies in Europe from fifteen
to forty years, according to soil, species, and rapidity of growth.
In the _futaie_, or full-growth system, the trees are allowed to stand
as long as they continue in healthy and vigorous growth. This is a
shorter period than would be at first supposed, when we consider the
advanced age and great dimensions to which, under favorable
circumstances, many forest trees attain in temperate climates. But, as
every observing person familiar with the natural forest is aware, these
are exceptional cases, just as are instances of great longevity or of
gigantic stature among men. Able vegetable physiologists have maintained
that the tree, like most reptiles, has no natural limit of life or of
growth, and that the only reason why our oaks and our pines do not reach
the age of twenty centuries and the height of a hundred fathoms, is,
that in the multitude of accidents to which they are exposed, the
chances of their attaining to such a length of years and to such
dimensions of growth are a million to one against them. But another
explanation of this fact is possible. In trees affected by no
discoverable external cause of death, decay begins at the topmost
branches, which seem to wither and die for want of nutriment. The
mysterious force by which the sap is carried from the roots to the
utmost twigs, cannot be conceived to be unlimited in power, and it is
probable that it differs in different species, so that while it may
suffice to raise the fluid to the height of five hundred feet in the
sequoia, it may not be able to carry it beyond one hundred and fifty in
the oak. The limit may be different, too, in different trees of the same
species, not from defective organization in those of inferior growth,
but from more or less favorable conditions of soil, nourishment, and
exposure. Whenever a tree attains to the limit beyond which its
circulating fluids cannot rise, we may suppose that decay begins, and
death follows, from the same causes which bring about the same results
in animals of limited size--such, for example, as the interruption of
functions essential to life, in consequence of the clogging up of ducts
by matter assimilable in the stage of growth, but no longer so when
increment has ceased.
In the natural woods, we observe that, though, among the myriads of
trees which grow upon a square mile, there are several vegetable giants,
yet the great majority of them begin to decay long before they have
attained their maximum of stature, and this seems to be still more
emphatically true of the artificial forest. In France, according to
Clavé, "oaks, in a suitable soil, may stand, without exhibiting any sign
of decay, for two or three hundred years; the pines hardly exceed one
hundred and twenty, and the soft or white woods [_bois blancs_], in wet
soils, languish and die before reaching the fiftieth year."[297] These
ages are certainly below the average of those of American forest trees,
and are greatly exceeded in very numerous well-attested instances of
isolated trees in Europe.
The former mode of treating the futaie, called the garden system, was to
cut the trees individually as they arrived at maturity, but, in the best
regulated forests, this practice has been abandoned for the German
method, which embraces not only the securing of the largest immediate
profit, but the replanting of the forest, and the care of the young
growth. This is effected in the case of a forest, whether natural or
artificial, which is to be subjected to regular management, by three
operations. The first of these consists in felling about one third of
the wood, in such way as to leave convenient spaces for the growth of
young trees. The remaining two-thirds are relied upon to replant the
vacancies, by natural sowing, which they seldom or never fail to do. The
seedlings are watched, are thinned out when too dense, the ill formed
and sickly, as well as those of inferior value, and the shrubs and
thorns which might otherwise choke or too closely shade them, are pulled
up. When they have attained sufficient strength and development of
foliage to bear or to require more light and air, the second step is
taken, by removing a suitable proportion of the old trees which had been
spared at the first cutting; and when, finally, they are hardened enough
to bear frost and sun without other protection than that which they
mutually give to each other, the remainder of the original forest is
felled, and the wood now consists wholly of young and vigorous trees.
This result is obtained after about twenty years. At convenient periods
afterward, the unhealthy stocks and those injured by wind or other
accidents are removed, and in some instances the growth of the remainder
is promoted by irrigation or by fertilizing applications.[298] When the
forest is approaching to maturity, the original processes already
described are repeated; and as, in different parts of an extensive
forest, they would take place in different zones, it would afford
indefinitely an annual crop of firewood and timber.
The duties of the forester do not end here. It sometimes happens that
the glades left by felling the older trees are not sufficiently seeded,
or that the species, or _essences_, as the French oddly call them, are
not duly proportioned in the new crop. In this case, seed must be
artificially sown, or young trees planted in the vacancies.
One of the most important rules in the administration of the forest is
the absolute exclusion of domestic quadrupeds from every wood which is
not destined to be cleared. No growth of young trees is possible where
cattle are admitted to pasture at any season of the year, though they
are undoubtedly most destructive while trees are in leaf.[299]
It is often necessary to take measures for the protection of young trees
against the rabbit, the mole, and other rodent quadrupeds, and of older
ones against the damage done by the larvæ of insects hatched upon the
surface or in the tissues of the bark, or even in the wood itself. The
much greater liability of the artificial than of the natural forest to
injury from this cause is perhaps the only point in which the
superiority of the former to the latter is not as marked as that of any
domesticated vegetable to its wild representative. But the better
quality of the wood and the much more rapid growth of the trained and
regulated forest are abundant compensations for the loss thus
occasioned, and the progress of entomological science will, perhaps,
suggest new methods of preventing the ravages of insects. Thus far,
however, the collection and destruction of the eggs, by simple but
expensive means, has proved the only effectual remedy.[300]
It is common in Europe to permit the removal of the fallen leaves and
fragments of bark and branches with which the forest soil is covered,
and sometimes the cutting of the lower twigs of evergreens. The leaves
and twigs are principally used as litter for cattle, and finally as
manure, the bark and wind-fallen branches as fuel. By long usage,
sometimes by express grant, this privilege has become a vested right of
the population in the neighborhood of many public, and even large
private forests; but it is generally regarded as a serious evil. To
remove the leaves and fallen twigs is to withdraw much of the pabulum
upon which the tree was destined to feed. The small branches and leaves
are the parts of the tree which yield the largest proportion of ashes on
combustion, and of course they supply a great amount of nutriment for
the young shoots. "A cubic foot of twigs," says Vaupell, "yields four
times as much ashes as a cubic foot of stem wood. * * For every hundred
weight of dried leaves carried off from a beech forest, we sacrifice a
hundred and sixty cubic feet of wood. The leaves and the mosses are a
substitute, not only for manure, but for ploughing. The carbonic acid
given out by decaying leaves, when taken up by water, serves to
dissolve the mineral constituents of the soil, and is particularly
active in disintegrating feldspar and the clay derived from its
decomposition. * * * The leaves belong to the soil. Without them it
cannot preserve its fertility, and cannot furnish nutriment to the
beech. The trees languish, produce seed incapable of germination, and
the spontaneous self-sowing, which is an indispensable element in the
best systems of sylviculture, fails altogether in the bared and
impoverished soil."[301]
Besides these evils, the removal of the leaves deprives the soil of that
spongy character which gives it such immense value as a reservoir of
moisture and a regulator of the flow of springs; and, finally, it
exposes the surface roots to the drying influence of sun and wind, to
accidental mechanical injury from the tread of animals or men, and, in
cold climates, to the destructive effects of frost.
The annual lopping and trimming of trees for fuel, so common in Europe,
is fatal to the higher uses of the forest, but where small groves are
made, or rows of trees planted, for no other purpose than to secure a
supply of firewood, or to serve as supports for the vine, it is often
very advantageous. The willows, and many other trees, bear polling for a
long series of years without apparent diminution of growth of branches,
and though certainly a polled, or, to use an old English word, a
doddered tree, is in general a melancholy object, yet it must be
admitted that the aspect of some species--the American locust, _Robinia
pseudacacia_, for instance--when young, is improved by this
process.[302]
I have spoken of the needs of agriculture as a principal cause of the
destruction of the forest, and of domestic cattle as particularly
injurious to the growth of young trees. But these animals affect the
forest, indirectly, in a still more important way, because the extent of
cleared ground required for agricultural use depends very much on the
number and kinds of the cattle bred. We have seen, in a former chapter,
that, in the United States, the domestic quadrupeds amount to more than
a hundred millions, or three times the number of the human population of
the Union. In many of the Western States, the swine subsist more or less
on acorns, nuts, and other products of the woods, and the prairies, or
natural meadows of the Mississippi valley, yield a large amount of food
for beast, as well as for man. With these exceptions, all this vast army
of quadrupeds is fed wholly on grass, grain, pulse, and roots grown on
soil reclaimed from the forest by European settlers. It is true that the
flesh of domestic quadrupeds enters very largely into the aliment of the
American people, and greatly reduces the quantity of vegetable nutriment
which they would otherwise consume, so that a smaller amount of
agricultural product is required for immediate human food, and, of
course, a smaller extent of cleared land is needed for the growth of
that product, than if no domestic animals existed. But the flesh of the
horse, the ass, and the mule is not consumed by man, and the sheep is
reared rather for its fleece than for food. Besides this, the ground
required to produce the grass and grain consumed in rearing and
fattening a grazing quadruped, would yield a far larger amount of
nutriment, if devoted to the growing of breadstuffs, than is furnished
by his flesh; and, upon the whole, whatever advantages may be reaped
from the breeding of domestic cattle, it is plain that the cleared land
devoted to their sustenance in the originally wooded part of the United
States, after deducting a quantity sufficient to produce an amount of
aliment equal to their flesh, still greatly exceeds that cultivated for
vegetables, directly consumed by the people of the same regions; or, to
express a nearly equivalent idea in other words, the meadow and the
pasture, taken together, much exceed the plough land.[303]
In fertile countries, like the United States, the foreign demand for
animal and vegetable aliment, for cotton, and for tobacco, much enlarges
the sphere of agricultural operations, and, of course, prompts further
encroachments upon the forest. The commerce in these articles,
therefore, constitutes in America a special cause of the destruction of
the woods, which does not exist in the numerous states of the Old World
that derive the raw material of their mechanical industry from distant
lands, and import many articles of vegetable food or luxury which their
own climates cannot advantageously produce.
The growth of arboreal vegetation is so slow that, though he who buries
an acorn may hope to see it shoot up to a miniature resemblance of the
majestic tree which shall shade his remote descendants, yet the longest
life hardly embraces the seedtime and the harvest of a forest. The
planter of a wood must be actuated by higher motives than those of an
investment the profits of which consist in direct pecuniary gain to
himself or even to his posterity; for if, in rare cases, an artificial
forest may, in two or three generations, more than repay its original
cost, still, in general, the value of its timber will not return the
capital expended and the interest accrued.[304] But when we consider the
immense collateral advantages derived from the presence, the terrible
evils necessarily resulting from the destruction of the forest, both the
preservation of existing woods, and the far more costly extension of
them where they have been unduly reduced, are among the most obvious of
the duties which this age owes to those that are to come after it.
Especially is this obligation incumbent upon Americans. No civilized
people profits so largely from the toils and sacrifices of its immediate
predecessors as they; no generations have ever sown so liberally, and,
in their own persons, reaped so scanty a return, as the pioneers of
Anglo-American social life. We can repay our debt to our noble
forefathers only by a like magnanimity, by a like self-forgetting care
for the moral and material interests of our own posterity.
_Instability of American Life._
All human institutions, associate arrangements, modes of life, have
their characteristic imperfections. The natural, perhaps the necessary
defect of ours, is their instability, their want of fixedness, not in
form only, but even in spirit. The face of physical nature in the United
States shares this incessant fluctuation, and the landscape is as
variable as the habits of the population. It is time for some abatement
in the restless love of change which characterizes us, and makes us
almost a nomade rather than a sedentary people.[305] We have now felled
forest enough everywhere, in many districts far too much. Let us restore
this one element of material life to its normal proportions, and devise
means for maintaining the permanence of its relations to the fields, the
meadows, and the pastures, to the rain and the dews of heaven, to the
springs and rivulets with which it waters the earth. The establishment
of an approximately fixed ratio between the two most broadly
characterized distinctions of rural surface--woodland and plough
land--would involve a certain persistence of character in all the
branches of industry, all the occupations and habits of life, which
depend upon or are immediately connected with either, without implying a
rigidity that should exclude flexibility of accommodation to the many
changes of external circumstance which human wisdom can neither prevent
nor foresee, and would thus help us to become, more emphatically, a
well-ordered and stable commonwealth, and, not less conspicuously, a
people of progress.
NOTE on word _watershed_, omitted on p. 257.--Sir John F. W.
Herschel (_Physical Geography_, 137, and elsewhere) spells this
word _water-sched_, because he considers it a translation, or
rather an adoption of the German "Wasser-scheide, separation of
the waters, not water-_shed_, the slope _down which_ the waters
run," As a point of historical etymology, it is probable that the
word in question was suggested to those who first used it by the
German _Wasserscheide_; but the spelling _water-sched_, proposed
by Herschel, is objectionable, both because _sch_ is a
combination of letters wholly unknown to modern English
orthography and properly representing no sound recognized in
English orthoepy, and for the still better reason that
_watershed_, in the sense of _division-of-the-waters_, has a
legitimate English etymology.
The Anglo-Saxon _sceadan_ meant both to separate or divide, and
to shade or shelter. It is the root of the English verbs _to
shed_ and _to shade_, and in the former meaning is the A. S.
equivalent of the German verb _scheiden_.
_Shed_ in Old English had the meaning _to separate_ or
_distinguish_. It is so used in the _Owl and the Nightingale_, v.
197. Palsgrave (_Lesclarcissement, etc._, p. 717) defines _I
shede_, I departe thinges asonder; and the word still means _to
divide_ in several English local dialects. Hence, _watershed_,
the division or separation of the waters, is good English both in
sense and spelling.
CHAPTER IV.
THE WATERS.
LAND ARTIFICIALLY WON FROM THE WATERS: _a_, EXCLUSION OF THE SEA BY
DIKING; _b_, DRAINING OF LAKES AND MARSHES; _c_, GEOGRAPHICAL INFLUENCE
OF SUCH OPERATIONS--LOWERING OF LAKES--MOUNTAIN LAKES--CLIMATIC EFFECTS
OF DRAINING LAKES AND MARSHES--GEOGRAPHICAL AND CLIMATIC EFFECTS OF
AQUEDUCTS, RESERVOIRS, AND CANALS--SURFACE AND UNDERDRAINING, AND THEIR
CLIMATIC AND GEOGRAPHICAL EFFECTS--IRRIGATION AND ITS CLIMATIC AND
GEOGRAPHICAL EFFECTS.
INUNDATIONS AND TORRENTS: _a_, RIVER EMBANKMENTS; _b_, FLOODS OF THE
ARDÈCHE; _c_, CRUSHING FORCE OF TORRENTS; _d_, INUNDATIONS OF 1856 IN
FRANCE; _e_, REMEDIES AGAINST INUNDATIONS--CONSEQUENCES IF THE NILE HAD
BEEN CONFINED BY LATERAL DIKES.
IMPROVEMENTS IN THE VAL DI CHIANA--IMPROVEMENTS IN THE TUSCAN
MAREMME--OBSTRUCTION OF RIVER MOUTHS--SUBTERRANEAN WATERS--ARTESIAN
WELLS--ARTIFICIAL SPRINGS--ECONOMIZING PRECIPITATION.
_Land artificially won from the Waters._
Man, as we have seen, has done much to revolutionize the solid surface
of the globe, and to change the distribution and proportions, if not the
essential character, of the organisms which inhabit the land and even
the waters. Besides the influence thus exerted upon the life which
peoples the sea, his action upon the land has involved a certain amount
of indirect encroachment upon the territorial jurisdiction of the ocean.
So far as he has increased the erosion of running waters by the
destruction of the forest, he has promoted the deposit of solid matter
in the sea, thus reducing its depth, advancing the coast line, and
diminishing the area covered by the waters. He has gone beyond this, and
invaded the realm of the ocean by constructing within its borders
wharves, piers, lighthouses, breakwaters, fortresses, and other
facilities for his commercial and military operations; and in some
countries he has permanently rescued from tidal overflow, and even from
the very bed of the deep, tracts of ground extensive enough to
constitute valuable additions to his agricultural domain. The quantity
of soil gained from the sea by these different modes of acquisition is,
indeed, too inconsiderable to form an appreciable element in the
comparison of the general proportion between the two great forms of
terrestrial surface, land and water; but the results of such operations,
considered in their physical and their moral bearings, are sufficiently
important to entitle them to special notice in every comprehensive view
of the relations between man and nature.
There are cases, as on the western shores of the Baltic, where, in
consequence of the secular elevation of the coast, the sea appears to be
retiring; others, where, from the slow sinking of the land, it seems to
be advancing. These movements depend upon geological causes wholly out
of our reach, and man can neither advance nor retard them. There are
also cases where similar apparent effects are produced by local oceanic
currents, by river deposit or erosion, by tidal action, or by the
influence of the wind upon the waves and the sands of the sea beach. A
regular current may drift suspended earth and seaweed along a coast
until they are caught by an eddy and finally deposited out of the reach
of further disturbance, or it may scoop out the bed of the sea and
undermine promontories and headlands; a powerful river, as the wind
changes the direction of its flow at its outlet, may wash away shores
and sandbanks at one point to deposit their material at another; the
tide or waves, stirred to unusual depths by the wind, may gradually wear
down the line of coast, or they may form shoals and coast dunes by
depositing the sand they have rolled up from the bottom of the ocean.
These latter modes of action are slow in producing effects sufficiently
important to be noticed in general geography, or even to be visible in
the representations of coast line laid down in ordinary maps; but they
nevertheless form conspicuous features in local topography, and they are
attended with consequences of great moment to the material and the moral
interests of men.
The forces which produce these results are all in a considerable degree
subject to control, or rather to direction and resistance, by human
power, and it is in guiding and combating them that man has achieved
some of his most remarkable and honorable conquests over nature. The
triumphs in question, or what we generally call harbor and coast
improvements, whether we estimate their value by the money and labor
expended upon them, or by their bearing upon the interests of commerce
and the arts of civilization, must take a very high rank among the great
works of man, and they are fast assuming a magnitude greatly exceeding
their former relative importance. The extension of commerce and of the
military marine, and especially the introduction of vessels of increased
burden and deeper draught of water, have imposed upon engineers tasks of
a character which a century ago would have been pronounced, and, in
fact, would have been impracticable; but necessity has stimulated an
ingenuity which has contrived means of executing them, and which gives
promise of yet greater performance in time to come.
Men have ceased to admire the power which heaped up the great pyramid to
gratify the pride of a despot with a giant sepulchre; for many great
harbors, many important lines of internal communication, in the
civilized world, now exhibit works which surpass the vastest remains of
ancient architectural art in mass and weight of matter, demand the
exercise of far greater constructive skill, and involve a much heavier
pecuniary expenditure than would now be required for the building of the
tomb of Cheops. It is computed that the great pyramid, the solid
contents of which when complete were about 3,000,000 cubic yards, could
be erected for a million of pounds sterling. The breakwater at
Cherbourg, founded in rough water sixty feet, deep, at an average
distance of more than two miles from the shore, contains double the mass
of the pyramid, and many a comparatively unimportant railroad has been
constructed at twice the cost which would now build that stupendous
monument. Indeed, although man, detached from the solid earth, is almost
powerless to struggle against the sea, he is fast becoming invincible by
it so long as his foot is planted on the shore, or even on the bottom of
the rolling ocean; and though on some battle fields between the waters
and the land, he is obliged slowly to yield his ground, yet he retreats
still facing the foe, and will finally be able to say to the sea: "Thus
far shalt thou come and no farther, and here shall thy proud waves be
stayed!"
The description of works of harbor and coast improvement which have only
an economical value, not a true geographical importance, does not come
within the plan of the present volume, and in treating this branch of my
subject, I shall confine myself to such as are designed either to gain
new soil by excluding the waters from grounds which they had permanently
or occasionally covered, or to resist new encroachments of the sea upon
the land.
a. _Exclusion of the Sea by Diking._
The draining of the Lincolnshire fens in England, which converted about
400,000 acres of marsh, pool, and tide-washed flat into plough land and
pasturage, is a work, or rather series of works, of great magnitude, and
it possesses much economical, and, indeed, no trifling geographical
importance. Its plans and methods were, at least in part, borrowed from
the example of like improvements in Holland, and it is, in difficulty
and extent, inferior to works executed for the same purpose on the
opposite coast of the North Sea, by Dutch, Frisic, and Low German
engineers. The space I can devote to such operations will be better
employed in describing the latter, and I content myself with the simple
statement I have already made of the quantity of worthless and even
pestilential land which has been rendered both productive and salubrious
in Lincolnshire, by diking out the sea, and the rivers which traverse
the fens of that country.
The almost continued prevalence of west winds upon both coasts of the
German Ocean occasions a constant set of the currents of that sea to the
east, and both for this reason and on account of the greater violence of
storms from the former quarter, the English shores are much less exposed
to invasion by the waves than those of the Netherlands and the provinces
contiguous to them on the north. The old Netherlandish chronicles are
filled with the most startling accounts of the damage done by the
irruptions of the ocean, from west winds or extraordinarily high tides,
at times long before any considerable extent of seacoast was diked.
Several hundreds of these terrible inundations are recorded, and in very
many of them the loss of human lives is estimated as high as one hundred
thousand. It is impossible to doubt that there must be enormous
exaggeration in these numbers; for, with all the reckless hardihood
shown by men in braving the dangers and privations attached by nature to
their birthplace, it is inconceivable that so dense a population as such
wholesale destruction of life supposes could find the means of
subsistence, or content itself to dwell, on a territory liable, a dozen
times in a century, to such fearful devastation. There can be no doubt,
however, that the low continental shores of the German Ocean very
frequently suffered immense injury from inundation by the sea, and it is
natural, therefore, that the various arts of resistance to the
encroachments of the ocean, and, finally, of aggressive warfare upon its
domain, and of permanent conquest of its territory, should have been
earlier studied and carried to higher perfection in the latter
countries, than in England, which had much less to lose or to gain by
the incursions or the retreat of the waters.
Indeed, although the confinement of swelling rivers by artificial
embankments is of great antiquity, I do not know that the defence or
acquisition of land from the sea by diking was ever practised on a large
scale until systematically undertaken by the Netherlanders, a few
centuries after the commencement of the Christian era. The silence of
the Roman historians affords a strong presumption that this art was
unknown to the inhabitants of the Netherlands at the time of the Roman
invasion, and the elder Pliny's description of the mode of life along
the coast which has now been long diked in, applies precisely to the
habits of the people who live on the low islands and mainland flats
lying outside of the chain of dikes, and wholly unprotected by
embankments of any sort.
It has been conjectured, and not without probability, that the causeways
built by the Romans across the marshes of the Low Countries, in their
campaigns against the Germanic tribes, gave the natives the first hint
of the utility which might be derived from similar constructions applied
to a different purpose.[306] If this is so, it is one of the most
interesting among the many instances in which the arts and enginery of
war have been so modified as to be eminently promotive of the blessings
of peace, thereby in some measure compensating the wrongs and sufferings
they have inflicted on humanity.[307] The Lowlanders are believed to
have secured some coast and bay islands by ring dikes, and to have
embanked some fresh water channels, as early as the eighth or ninth
century; but it does not appear that sea dikes, important enough to be
noticed in historical records, were constructed on the mainland before
the thirteenth century. The practice of draining inland accumulation of
water, whether fresh or salt, for the purpose of bringing under
cultivation the ground they cover, is of later origin, and is said not
to have been adopted until after the middle of the fifteenth
century.[308]
The total amount of surface gained to the agriculture of the Netherlands
by diking out the sea and by draining shallow bays and lakes, is
estimated by Staring at three hundred and fifty-five thousand _bunder_
or hectares, equal to eight hundred and seventy-seven thousand two
hundred and forty acres, which is one tenth of the area of the
kingdom.[309] In very many instances, the dikes have been partially, in
some particularly exposed localities totally destroyed by the violence
of the sea, and the drained lands again flooded. In some cases, the soil
thus painfully won from the ocean has been entirely lost; in others it
has been recovered by repairing or rebuilding the dikes and pumping out
the water. Besides this, the weight of the dikes gradually sinks them
into the soft soil beneath, and this loss of elevation must be
compensated by raising the surface, while the increased burden thus
added tends to sink them still lower. "Tetens declares," says Kohl,
"that in some places the dikes have gradually sunk to the depth of sixty
or even a hundred feet."[310] For these reasons, the processes of dike
building have been almost everywhere again and again repeated, and thus
the total expenditure of money and of labor upon the works in question
is much greater than would appear from an estimate of the actual cost of
diking-in a given extent of coast land and draining a given area of
water surface.[311]
On the other hand, by erosion of the coast line, the drifting of sand
dunes into the interior, and the drowning of fens and morasses by
incursions of the sea--all caused, or at least greatly aggravated, by
human improvidence--the Netherlands have lost a far larger area of land
since the commencement of the Christian era than they have gained by
diking and draining. Staring despairs of the possibility of calculating
the loss from the first-mentioned two causes of destruction, but he
estimates that not less than six hundred and forty thousand bunder, or
one million five hundred and eighty-one thousand acres, of fen and marsh
have been washed away, or rather deprived of their vegetable surface and
covered by water, and thirty-seven thousand bunder, or ninety-one
thousand four hundred acres of recovered land, have been lost by the
destruction of the dikes which protected them.[312] The average value of
land gained from the sea is estimated at about nineteen pounds sterling,
or ninety dollars, per acre; while the lost fen and morass was not worth
more than one twenty-fifth part of the same price. The ground buried by
the drifting of the dunes appears to have been almost entirely of this
latter character, and, upon the whole, there is no doubt that the soil
added by human industry to the territory of the Netherlands, within the
historical period, greatly exceeds in pecuniary value that which has
fallen a prey to the waves during the same era.
Upon most low and shelving coasts, like those of the Netherlands, the
maritime currents are constantly changing, in consequence of the
variability of the winds, and the shifting of the sandbanks, which the
currents themselves now form and now displace. While, therefore, at one
point the sea is advancing landward, and requiring great effort to
prevent the undermining and washing away of the dikes, it is shoaling at
another by its own deposits, and exposing, at low water, a gradually
widening belt of sands and ooze. The coast lands selected for diking-in
are always at points where the sea is depositing productive soil. The
Eider, the Elbe, the Weser, the Ems, the Rhine, the Maas, and the
Schelde bring down large quantities of fine earth. The prevalence of
west winds prevents the waters from carrying this material far out from
the coast, and it is at last deposited northward or southward from the
mouth of the rivers which contribute it, according to the varying drift
of the currents.
The process of natural deposit which prepares the coast for diking-in is
thus described by Staring: "All sea-deposited soil is composed of the
same constituents. First comes a stratum of sand, with marine shells, or
the shells of mollusks living in brackish water. If there be tides, and,
of course, flowing and ebbing currents, mud is let fall upon the sand
only after the latter has been raised above low-water mark; for then
only, at the change from flood to ebb, is the water still enough to form
a deposit of so light a material. Where mud is found at greater depths,
as, for example, in a large proportion of the Ij, it is a proof that
at this point there was never any considerable tidal flow or other
current. * * * The powerful tidal currents, flowing and ebbing twice a
day, drift sand with them. They scoop out the bottom at one point, raise
it at another, and the sandbanks in the current are continually
shifting. As soon as a bank raises itself above low-water mark, flags
and reeds establish themselves upon it. The mechanical resistance of
these plants checks the retreat of the high water and favors the deposit
of the earth suspended in it, and the formation of land goes on with
surprising rapidity. When it has risen to high-water level, it is soon
covered with grasses, and becomes what is called _schor_ in Zeeland,
_kwelder_ in Friesland. Such grounds are the foundation or starting
point of the process of diking. When they are once elevated to the
flood-tide level, no more mud is deposited upon them except by
extraordinary high tides. Their further rise is, accordingly, very slow,
and it is seldom advantageous to delay longer the operation of
diking."[313]
The formation of new banks by the sea is constantly going on at points
favorable for the deposit of sand and earth, and hence opportunity is
continually afforded for enclosure of new land outside of that already
diked in, the coast is fast advancing seaward, and every new embankment
increases the security of former enclosures. The province of Zeeland
consists of islands washed by the sea on their western coasts, and
separated by the many channels through which the Schelde and some other
rivers find their way to the ocean. In the twelfth century these
islands were much smaller and more numerous than at present. They have
been gradually enlarged, and, in several instances, at last connected by
the extension of their system of dikes. Walcheren is formed of ten
islets united into one about the end of the fourteenth century. At the
middle of the fifteenth century, Goeree and Overflakkee consisted of
separate islands, containing altogether about ten thousand acres; by
means of above sixty successive advances of the dikes, they have been
brought to compose a single island, whose area is not less than sixty
thousand acres.[314]
In the Netherlands--which the first Napoleon characterized as a deposit
of the Rhine, and as, therefore, by natural law, rightfully the property
of him who controlled the sources of that great river--and on the
adjacent Frisic, Low German and Danish shores and islands, sea and river
dikes have been constructed on a grander and more imposing scale than in
any other country. The whole economy of the art has been there most
thoroughly studied, and the literature of the subject is very extensive.
For my present aim, which is concerned with results rather than with
processes, it is not worth while to refer to professional treatises, and
I shall content myself with presenting such information as can be
gathered from works of a more popular character.[315]
The superior strata of the lowlands upon and near the coast are, as we
have seen, principally composed of soil brought down by the great
rivers I have mentioned, and either directly deposited by them upon the
sands of the bottom, or carried out to sea by their currents, and then,
after a shorter or longer exposure to the chemical and mechanical action
of salt water and marine currents, restored again to the land by tidal
overflow and subsidence from the waters in which it was suspended. At a
very remote period, the coast flats were, at many points, raised so high
by successive alluvious or tidal deposits as to be above ordinary high
water level, but they were still liable to occasional inundation from
river floods, and from the sea water also, when heavy or long-continued
west winds drove it landward. The extraordinary fertility of this soil
and its security as a retreat from hostile violence attracted to it a
considerable population, while its want of protection against inundation
exposed it to the devastations of which the chroniclers of the Middle
Ages have left such highly colored pictures. The first permanent
dwellings on the coast flats were erected upon artificial mounds, and
many similar precarious habitations still exist on the unwalled islands
and shores beyond the chain of dikes. River embankments, which, as is
familiarly known, have from the earliest antiquity been employed in many
countries where sea dikes are unknown, were probably the first works of
this character constructed in the Low Countries, and when two
neighboring streams of fresh water had been embanked, the next step in
the process would naturally be to connect the river walls together by a
transverse dike or raised causeway, which would serve to secure the
intermediate ground both against the backwater of river floods and
against overflow by the sea. The oldest true sea dikes described in
historical records, however, are those enclosing islands in the
estuaries of the great rivers, and it is not impossible that the double
character they possess as a security against maritime floods and as a
military rampart, led to their adoption upon those islands before
similar constructions had been attempted upon the mainland.
At some points of the coast, various contrivances, such as piers, piles,
and, in fact, obstructions of all sorts to the ebb of the current, are
employed to facilitate the deposit of slime, before a regular enclosure
is commenced. Usually, however, the first step is to build low and cheap
embankments, extending from an older dike, or from high ground, around
the parcel of flat intended to be secured. These are called summer dikes
(_sommer-deich_, pl. _sommer-deiche_, German; _zomerkaai_, _zomerkade_,
pl. _zomerkaaie_, _zomerkaden_, Dutch). They are erected when a
sufficient extent of ground to repay the cost has been elevated enough
to be covered with coarse vegetation fit for pasturage. They serve both
to secure the ground from overflow by the ordinary flood tides of mild
weather, and to retain the slime deposited by very high water, which
would otherwise be partly carried off by the retreating ebb. The
elevation of the soil goes on slowly after this; but when it has at last
been sufficiently enriched, and raised high enough to justify the
necessary outlay, permanent dikes are constructed by which the water is
excluded at all seasons. These embankments are constructed of sand from
the coast dunes or from sandbanks, and of earth from the mainland or
from flats outside the dikes, bound and strengthened by fascines, and
provided with sluices, which are generally founded on piles and of very
expensive construction, for drainage at low water. The outward slope of
the sea dikes is gentle, experience having shown that this form is least
exposed to injury both from the waves and from floating ice, and the
most modern dikes are even more moderate in the inclination of the
seaward scarp than the older ones.[316] The crown of the dike, however,
for the last three or four feet of its height, is much steeper, being
intended rather as a protection against the spray than against the
waves, and the inner slope is always comparatively abrupt.
The height and thickness of dikes varies according to the elevation of
the ground they enclose, the rise of the tides, the direction of the
prevailing winds, and other special causes of exposure, but it may be
said that they are, in general, raised from fifteen to twenty feet above
ordinary high-water mark. The water slopes of river dikes are protected
by plantations of willows or strong semi-aquatic shrubs or grasses, but
as these will not grow upon banks exposed to salt water, sea dikes must
be faced with stone, fascines, or some other _revêtement_.[317] Upon the
coast of Schleswig and Holstein, where the people have less capital at
their command, they defend their embankments against ice and the waves
by a coating of twisted straw or reeds, which must be renewed as often
as once, sometimes twice a year. The inhabitants of these coasts call
the chain of dikes "the golden border," a name it well deserves, whether
we suppose it to refer to its enormous cost, or, as is more probable, to
its immense value as a protection to their fields and their firesides.
When outlying flats are enclosed by building new embankments, the old
interior dikes are suffered to remain, both as an additional security
against the waves, and because the removal of them would be expensive.
They serve, also, as roads or causeways, a purpose for which the
embankments nearest the sea are seldom employed, because the whole
structure might be endangered from the breaking of the turf by wheels
and the hoofs of horses. Where successive rows of dikes have been thus
constructed, it is observed that the ground defended by the more ancient
embankments is lower than that embraced within the newer enclosures, and
this depression of level has been ascribed to a general subsidence of
the coast from geological causes; but the better opinion seems to be
that it is, in most cases, due merely to the consolidation and settling
of the earth from being more effectually dried, from the weight of the
dikes, from the tread of men and cattle, and from the movement of the
heavy wagons which carry off the crops.[318] Notwithstanding this slow
sinking, most of the land enclosed by dikes is still above low-water
mark, and can, therefore, be wholly or partially freed from rain water,
and from that received by infiltration from higher ground, by sluices
opened at the ebb of the tide. For this purpose, the land is carefully
ditched, and advantage is taken of every favorable occasion for
discharging the water through the sluices. But the ground cannot be
effectually drained by this means, unless it is elevated four or five
feet, at least, above the level of the ebb tide, because the ditches
would not otherwise have a sufficient descent to carry the water off in
the short interval between ebb and flow, and because the moisture of the
saturated subsoil is always rising by capillary attraction. Whenever,
therefore, the soil has sunk below the level I have mentioned, and in
cases where its surface has never been raised above it, pumps, worked by
wind or some other mechanical power, must be very frequently employed to
keep the land dry enough for pasturage and cultivation.[319]
b. _Draining of Lakes and Marshes._
The substitution of steam engines for the feeble and uncertain action of
windmills, in driving pumps, has much facilitated the removal of water
from the polders and the draining of lakes, marshes, and shallow bays,
and thus given such an impulse to these enterprises, that not less than
one hundred and ten thousand acres were reclaimed from the waters, and
added to the agricultural domain of the Netherlands, between 1815 and
1858. The most important of these undertakings was the draining of the
Lake of Haarlem, and for this purpose some of the most powerful
hydraulic engines ever constructed were designed and executed.[320] The
origin of this lake is unknown. It is supposed by some geographers to be
a part of an ancient bed of the Rhine, the channel of which, as there is
good reason to believe, has undergone great changes since the Roman
invasion of the Netherlands; by others it is thought to have once formed
an inland marine channel, separated from the sea by a chain of low
islands, which the sand washed up by the tides has since connected with
the mainland and converted into a continuous line of coast. The best
authorities, however, find geological evidence that the surface occupied
by the lake was originally a marshy tract containing within its limits
little solid ground, but many ponds and inlets, and much floating as
well as fixed fen.
In consequence of the cutting of turf for fuel, and the destruction of
the few trees and shrubs which held the loose soil together with their
roots, the ponds are supposed to have gradually extended themselves,
until the action of the wind upon their enlarged surface gave their
waves sufficient force to overcome the resistance of the feeble barriers
which separated them, and to unite them all into a single lake. Popular
tradition, it is true, ascribes the formation of the Lake of Haarlem to
a single irruption of the sea, at a remote period, and connects it with
one or another of the destructive inundations of which the Netherland
chronicles describe so many; but on a map of the year 1531, a chain of
four smaller waters occupies nearly the ground afterward covered by the
Lake of Haarlem, and they have more probably been united by gradual
encroachments resulting from the improvident practices above referred
to, though no doubt the consummation may have been hastened by floods,
and by the neglect to maintain dikes, or the intentional destruction of
them, in the long wars of the sixteenth century.
The Lake of Haarlem was a body of water not far from fifteen miles in
length, by seven in greatest width, lying between the cities of
Amsterdam and Leyden, running parallel with the coast of Holland at the
distance of about five miles from the sea, and covering an area of about
45,000 acres. By means of the Ij, it communicated with the Zuiderzee,
the Mediterranean of the Netherlands, and its surface was little above
the mean elevation of that of the sea. Whenever, therefore, the waters
of the Zuiderzee were acted upon by strong northwest winds, those of the
Lake of Haarlem were raised proportionally and driven southward, while
winds from the south tended to create a flow in the opposite direction.
The shores of the lake were everywhere low, and though in the course of
the eighty years between 1767 and 1848 more than £350,000 or $1,700,000
had been expended in checking its encroachments, it often burst its
barriers, and produced destructive inundations. On the 29th of November,
1836, a south wind brought its waters to the very gates of Amsterdam,
and on the 26th of December of the same year, in a northwest gale, they
overflowed twenty thousand acres of land at the southern extremity of
the lake, and flooded a part of the city of Leyden. The depth of water
did not, in general, exceed fourteen feet, but the bottom was a
semi-fluid ooze or slime, which partook of the agitation of the waves,
and added considerably to their mechanical force. Serious fears were
entertained that the lake would form a junction with the inland waters
of the Legmeer and Mijdrecht, swallow up a vast extent of valuable soil,
and finally endanger the security of a large proportion of the land
which the industry of Holland had gained in the course of centuries from
the ocean.
For this reason, and for the sake of the large addition the bottom of
the lake would make to the cultivable soil of the state, it was resolved
to drain it, and the preliminary steps for that purpose were commenced
in the year 1840. The first operation was to surround the entire lake
with a ring canal and dike, in order to cut off the communication with
the Ij, and to exclude the water of the streams and morasses which
discharged themselves into it from the land side. The dike was composed
of different materials, according to the means of supply at different
points, such as sand from the coast dunes, earth and turf excavated from
the line of the ring canal, and floating turf,[321] fascines being
everywhere used to bind and compact the mass together. This operation
was completed in 1848, and three steam pumps were then employed for five
years in discharging the water. The whole enterprise was conducted at
the expense of the state, and in 1853 the recovered lands were offered
for sale for its benefit. Up to 1858, forty-two thousand acres had been
sold at not far from sixteen pounds sterling or seventy-seven dollars an
acre, amounting altogether to £661,000 sterling or $3,200,000. The
unsold lands were valued at more than £6,000 or nearly $30,000, and as
the total cost was £764,500 or about $3,700,000, the direct loss to the
state, exclusive of interest on the capital expended, may be stated at
£100,000 or something less than $500,000.
In a country like the United States, of almost boundless extent of
sparsely inhabited territory, such an expenditure for such an object
would be poor economy. But Holland has a narrow domain, great pecuniary
resources, an excessively crowded population, and a consequent need of
enlarged room and opportunity for the exercise of industry. Under such
circumstances, and especially with an exposure to dangers so formidable,
there is no question of the wisdom of the measure. It has already
provided homes and occupation for more than five thousand citizens, and
furnished a profitable investment for a capital of not less than
£400,000 sterling or $2,000,000, which has been expended in improvements
over and above the purchase money of the soil; and the greater part of
this sum, as well as of the cost of drainage, has been paid as a
compensation for labor. The excess of governmental expenditure over the
receipts, if employed in constructing ships of war or fortifications,
would have added little to the military strength of the kingdom; but the
increase of territory, the multiplication of homes and firesides which
the people have an interest in defending, and the augmentation of
agricultural resources, constitute a stronger bulwark against foreign
invasion than a ship of the line or a fortress armed with a hundred
cannon.
The bearing of the works I have noticed, and of others similar in
character, upon the social and moral, as well as the purely economical
interests of the people of the Netherlands, has induced me to describe
them more in detail than the general purpose of this volume may be
thought to justify; but if we consider them simply from a geographical
point of view, we shall find that they are possessed of no small
importance as modifications of the natural condition of terrestrial
surface. There is good reason to believe that before the establishment
of a partially civilized race upon the territory now occupied by Dutch,
Frisic, and Low German communities, the grounds not exposed to
inundation were overgrown with dense woods, that the lowlands between
these forests and the sea coasts were marshes, covered and partially
solidified by a thick matting of peat plants and shrubs interspersed
with trees, and that even the sand dunes of the shore were protected by
a vegetable growth which, in a great measure, prevented the drifting and
translocation of them.
The present causes of river and coast erosion existed, indeed, at the
period in question; but some of them must have acted with less
intensity, there were strong natural safeguards against the influence of
marine and fresh-water currents, and the conflicting tendencies had
arrived at a condition of approximate equilibrium, which permitted but
slow and gradual changes in the face of nature. The destruction of the
forests around the sources and along the valleys of the rivers by man
gave them a more torrential character. The felling of the trees, and the
extirpation of the shrubbery upon the fens by domestic cattle, deprived
the surface of cohesion and consistence, and the cutting of peat for
fuel opened cavities in it, which, filling at once with water, rapidly
extended themselves by abrasion of their borders, and finally enlarged
to pools, lakes, and gulfs, like the Lake of Haarlem and the northern
part of the Zuiderzee. The cutting of the wood and the depasturing of
the grasses upon the sand dunes converted them from solid bulwarks
against the ocean to loose accumulations of dust, which every sea breeze
drove farther landward, burying, perhaps, fertile soil and choking up
watercourses on one side, and exposing the coast to erosion by the sea
upon the other.
c. _Geographical Influence of such Operations._
The changes which human action has produced within twenty centuries in
the Netherlands and the neighboring provinces, are certainly of no small
geographical importance, considered simply as a direct question of loss
and gain of territory. They have also undoubtedly been attended with
some climatic consequences, they have exercised a great influence on the
spontaneous animal and vegetable life of this region, and they cannot
have failed to produce effects upon tidal and other oceanic currents,
the range of which may be very extensive. The force of the tidal wave,
the height to which it rises, the direction of its currents, and, in
fact, all the phenomena which characterize it, as well as all the
effects it produces, depend as much upon the configuration of the coast
it washes, and the depth of water, and form of bottom near the shore, as
upon the attraction which occasions it. Every one of the terrestrial
conditions which affect the character of tidal and other marine currents
has been very sensibly modified by the operations I have described, and
on this coast, at least, man has acted almost as powerfully on the
physical geography of the sea as on that of the land.
_Lowering of Lakes._
The hydraulic works of the Netherlands and of the neighboring states are
of such magnitude, that they quite throw into the shade all other known
artificial arrangements for defending the land against the encroachments
of the rivers and the sea, and for reclaiming to the domain of
agriculture and civilization soil long covered by the waters. But
although the recovery and protection of lands flooded by the sea seems
to be an art wholly of Netherlandish origin, we have abundant evidence,
that in ancient as well as in comparatively modern times, great
enterprises more or less analogous in character have been successfully
undertaken, both in inland Europe and in the less familiar countries of
the East.
One of the best known of these is the tunnel which serves to discharge
the surplus waters of the Lake of Albano, about fourteen miles from
Rome. This lake, about six miles in circuit, occupies one of the craters
of an extinct volcanic range, and the surface of its waters is about
nine hundred feet above the sea. It is fed by rivulets and subterranean
springs originating in the Alban Mount, or Monte Cavo, the most elevated
peak of the volcanic group just mentioned, which rises to the height of
about three thousand feet. At present the lake has no discoverable
natural outlet, but it is not known that the water ever stood at such a
height as to flow regularly over the lip of the crater. It seems that at
the earliest period of which we have any authentic memorials, its level
was usually kept by evaporation, or by discharge through subterranean
channels, considerably below the rim of the basin which encompassed it,
but in the year 397 B. C., the water, either from the obstruction of
such channels, or in consequence of increased supplies from unknown
sources, rose to such a height as to flow over the edge of the crater,
and threaten inundation to the country below by bursting through its
walls. To obviate this danger, a tunnel for carrying off the water was
pierced at a level much below the height to which it had risen. This
gallery, cut entirely with the chisel through the rock for a distance
of six thousand feet, or nearly a mile and one seventh, is still in so
good condition as to serve its original purpose. The fact that this work
was contemporaneous with the siege of Veii, has given to ancient
annalists occasion to connect the two events, but modern critics are
inclined to reject Livy's account of the matter, as one of the many
improbable fables which disfigure the pages of that historian. It is,
however, repeated by Cicero and by Dionysins of Halicarnassus, and it is
by no means impossible that, in an age when priests and soothsayers
monopolized both the arts of natural magic and the little which yet
existed of physical science, the Government of Rome, by their aid,
availed itself at once of the superstition and of the military ardor of
its citizens to obtain their sanction to an enterprise which sounder
arguments might not have induced them to approve.
Still more remarkable is the tunnel cut by the Emperor Claudius to drain
the Lake Fucinus, now Lago di Celano, in the Neapolitan territory, about
fifty miles eastward of Rome. This lake, as far as its history is known,
has varied very considerably in its dimensions at different periods,
according to the character of the seasons. It has no visible outlet, but
was originally either drained by natural subterranean conduits, or kept
within certain extreme limits by evaporation. In years of uncommon
moisture, it spread over the adjacent soil and destroyed the crops; in
dry seasons, it retreated, and produced epidemic disease by poisonous
exhalations from the decay of vegetable and animal matter upon its
exposed bed. Julius Cæsar had proposed the construction of a tunnel to
drain the lake, but the enterprise was not actually undertaken until the
reign of Claudius, when--after a temporary failure, from errors in
levelling by the engineers, as was pretended at the time, or, as now
appears certain, in consequence of frauds by the contractors in the
execution of the work--it was at least partially completed. From this
imperfect construction, it soon got out of repair, but was restored by
Hadrian, and seems to have answered its design for some centuries. In
the barbarism which followed the downfall of the empire, it again fell
into decay, and though numerous attempts were made to repair it during
the Middle Ages, no tolerable success seems to have attended any of
these efforts, until the present generation.
Works have now been some years in progress for restoring, or rather
enlarging and rebuilding this ancient tunnel, upon a scale of grandeur
which does infinite honor to the liberality and public spirit of the
projectors, and with an ingenuity of design and a constructive skill
which reflect the highest credit upon the professional ability of the
engineers who have planned the works and directed their execution. The
length of this tunnel is 18,634 feet, or rather more than three miles
and a half. Of course, it is one of the longest subterranean galleries
yet executed in Europe, and it offers many curious particulars in its
original design which cannot here be described. The difference between
the highest and the lowest known levels of the surface of the lake
amounts to at least forty feet, and the difference of area covered at
these respective stages is not much less than eight thousand acres. The
tunnel will reduce the water to a much lower point, and it is computed
that, including the lands occasionally overflowed, not less than forty
thousand acres of as fertile soil as any in Italy will be recovered from
the lake and permanently secured from inundation by its waters.
Many similar enterprises have been conceived and executed in modern
times, both for the purpose of reclaiming land covered by water and for
sanitary reasons.[322] They are sometimes attended with wholly
unexpected evils, as, for example, in the case of Barton Pond, in
Vermont, and in that of the Lake Storsjö, in Sweden, already mentioned
on a former page. Another still less obvious consequence of the
withdrawal of the waters has occasionally been observed in these
operations. The hydrostatic force with which the water, in virtue of its
specific gravity, presses against the banks that confine it, has a
tendency to sustain them whenever their composition and texture are not
such as to expose them to softening and dissolution by the infiltration
of the water. If then, the slope of the banks is considerable, or if the
earth of which they are composed rests on a smooth and slippery stratum
inclining toward the bed of the lake, they are liable to fall or slide
forward when the mechanical support of the water is removed, and this
sometimes happens on a considerable scale. A few years ago, the surface
of the Lake of Lungern, in the Canton of Unterwalden, in Switzerland,
was lowered by driving a tunnel about a quarter of a mile long through
the narrow ridge, called the Kaiserstuhl, which forms a barrier at the
north end of the basin. When the water was drawn off, the banks, which
are steep, cracked and burst, several acres of ground slid down as low
as the water receded, and even the whole village of Lungern was thought
to be in no small danger.
Other inconveniences of a very serious character have often resulted
from the natural wearing down, or, much more frequently, the imprudent
destruction, of the barriers which confine mountain lakes. In their
natural condition, such basins serve both to receive and retain the
rocks and other detritus brought down by the torrents which empty into
them, and to check the impetus of the rushing waters by bringing them to
a temporary pause; but if the outlets are lowered so as to drain the
reservoirs, the torrents continue their rapid flow through the ancient
bed of the basins, and carry down with them the sand and gravel with
which they are charged, instead of depositing their burden as before in
the still waters of the lakes.
_Mountain Lakes._
It is a common opinion in America that the river meadows, bottoms, or
_intervales_, as they are popularly called, are generally the beds of
ancient lakes which have burst their barriers and left running currents
in their place. It was shown by Dr. Dwight, many years ago, that this is
very far from being universally true; but there is no doubt that
mountain lakes were of much more frequent occurrence in primitive than
in modern geography, and there are many chains of such still existing in
regions where man has yet little disturbed the original features of the
earth. In the long valleys of the Adirondack range in Northern New York,
and in the mountainous parts of Maine, eight, ten, and even more lakes
and lakelets are sometimes found in succession, each emptying into the
next lower pool, and so all at last into some considerable river. When
the mountain slopes which supply these basins shall be stripped of their
woods, the augmented swelling of the lakes will break down their
barriers, their waters will run off, and the valleys will present
successions of flats with rivers running through them, instead of chains
of lakes connected by natural canals.
A similar state of things seems to have existed in the ancient geography
of France. "Nature," says Lavergne, "has not excavated on the flanks of
our Alps reservoirs as magnificent as those of Lombardy; she had,
however, constructed smaller, but more numerous lakes, which the
negligence of man has permitted to disappear. Auguste de Gasparin,
brother of the illustrious agriculturist, demonstrated more than thirty
years ago, in an original paper, that many natural dikes formerly
existed in the mountain valleys, which have been swept away by the
waters. He proposed to rebuild and to multiply them. This interesting
suggestion has reappeared several times since, but has met with strong
opposition from skilful engineers. It would, nevertheless, be well to
try the experiment of creating artificial lakes which should fill
themselves with the water of melting snows and deluging rains, to be
drawn out in times of drought. If this plan has able opposers, it has
also warm advocates. Experience alone can decide the question."[323]
_Climatic Effects of Draining Lakes and Marshes._
The draining of lakes, marshes, and other superficial accumulations of
moisture, reduces the water surface of a country, and, of course, the
evaporation from it. Lakes, too, in elevated positions, lose a part of
their water by infiltration, and thereby supply other lakes, springs,
and rivulets at lower levels. Hence, it is evident that the draining of
such waters, if carried on upon a large scale, must affect both the
humidity and the temperature of the atmosphere, and the permanent supply
of water for extensive districts.[324]
_Geographical and Climatic Effects of Aqueducts, Reservoirs, and
Canals._
Many processes of internal improvement, such as aqueducts for the supply
of great cities, railroad cuts and embankments, and the like, divert
water from its natural channels, and affect its distribution and
ultimate discharge. The collecting of the waters of a considerable
district into reservoirs, to be thence carried off by means of
aqueducts, as, for example, in the forest of Belgrade, near
Constantinople, deprives the grounds originally watered by the springs
and rivulets of the necessary moisture, and reduces them to barrenness.
Similar effects must have followed from the construction of the numerous
aqueducts which supplied ancient Rome with such a profuse abundance of
water. On the other hand, the filtration of water through the banks or
walls of an aqueduct carried upon a high level across low ground, often
injures the adjacent soil, and is prejudicial to the health of the
neighboring population; and it has been observed in Switzerland, that
fevers have been produced by the stagnation of the water in excavations
from which earth had been taken to form embankments for railways.
If we consider only the influence of physical improvements on civilized
life, we shall perhaps ascribe to navigable canals a higher importance,
or at least a more diversified influence, than to any other works of man
designed to control the waters of the earth, and to affect their
distribution, They bind distant regions together by social ties, through
the agency of the commerce they promote; they facilitate the
transportation of military stores and engines, and of other heavy
material connected with the discharge of the functions of government;
they encourage industry by giving marketable value to raw material and
to objects of artificial elaboration which would otherwise be worthless
on account of the cost of conveyance; they supply from their surplus
waters means of irrigation and of mechanical power; and, in many other
ways, they contribute much to advance the prosperity and civilization of
nations. Nor are they wholly without geographical importance. They
sometimes drain lands by conveying off water which would otherwise
stagnate on the surface, and, on the other hand, like aqueducts, they
render the neighboring soil cold and moist by the percolation of water
through their embankments;[325] they dam up, check, and divert the
course of natural currents, and deliver them at points opposite to, or
distant from, their original outlets; they often require extensive
reservoirs to feed them, thus retaining through the year accumulations
of water--which would otherwise run off, or evaporate in the dry
season--and thereby enlarging the evaporable surface of the country; and
we have already seen that they interchange the flora and the fauna of
provinces widely separated by nature. All these modes of action
certainly influence climate and the character of terrestrial surface,
though our means of observation are not yet perfected enough to enable
us to appreciate and measure their effects.
_Climatic and Geographical Effects of Surface and Underground Draining._
I have commenced this chapter with a description of the dikes and other
hydraulic works of the Netherland engineers, because the geographical
results of such operations are more obvious and more easily measured,
though certainly not more important, than those of the older and more
widely diffused modes of resisting or directing the flow of waters,
which have been practised from remote antiquity in the interior of all
civilized countries. Draining and irrigation are habitually regarded as
purely agricultural processes, having little or no relation to technical
geography; but we shall find that they exert a powerful influence on
soil, climate, and animal and vegetable life, and may, therefore, justly
claim to be regarded as geographical elements.
_Surface and Under-draining and their Effects._
Superficial draining is a necessity in all lands newly reclaimed from
the forest. The face of the ground in the woods is never so regularly
inclined as to permit water to flow freely over it. There are, even on
the hillsides, many small ridges and depressions, partly belonging to
the original distribution of the soil, and partly occasioned by
irregularities in the growth and deposit of vegetable matter. These, in
the husbandry of nature, serve as dams and reservoirs to collect a
larger supply of moisture than the spongy earth can at once imbibe.
Besides this, the vegetable mould is, even under the most favorable
circumstances, slow in parting with the humidity it has accumulated
under the protection of the woods, and the infiltration from neighboring
forests contributes to keep the soil of small clearings too wet for the
advantageous cultivation of artificial crops. For these reasons, surface
draining must have commenced with agriculture itself, and there is
probably no cultivated district, one may almost say no single field,
which is not provided with artificial arrangements for facilitating the
escape of superficial water, and thus carrying off moisture which, in
the natural condition of the earth, would have been imbibed by the soil.
The beneficial effects of surface drainage, the necessity of extending
the fields as population increased, and the inconveniences resulting
from the presence of marshes in otherwise improved regions, must have
suggested at a very early period of human industry the expediency of
converting bogs and swamps into dry land by drawing off their waters;
and it would not be long after the introduction of this practice before
further acquisition of agricultural territory would be made by lowering
the outlet of small ponds and lakes, and adding the ground they covered
to the domain of the husbandman.
All these processes belong to the incipient civilization of the
ante-historical periods, but the construction of subterranean channels
for the removal of infiltrated water marks ages and countries
distinguished by a great advance in agricultural theory and practice, a
great accumulation of pecuniary capital, and a density of population
which creates a ready demand and a high price for all products of rural
industry. Under-draining, too, would be most advantageous in damp and
cool climates, where evaporation is slow, and upon soils where the
natural inclination of surface does not promote a very rapid flow of the
surface waters. All the conditions required to make this mode of rural
improvement, if not absolutely necessary, at least apparently
profitable, exist in Great Britain, and it is, therefore, very natural
that the wealthy and intelligent farmers of England should have carried
this practice farther, and reaped a more abundant pecuniary return from
it, than those of any other country.
Besides superficial and subsoil drains, there is another method of
disposing of superfluous surface water, which, however, can rarely be
practised, because the necessary conditions for its employment are not
of frequent occurrence. Whenever a tenacious water-holding stratum rests
on a loose, gravelly bed, so situated as to admit of a free discharge of
water from or through it by means of the outcropping of the bed at a
lower level, or of deep-lying conduits leading to distant points of
discharge, superficial waters may be carried off by opening a passage
for them through the impervious into the permeable stratum. Thus,
according to Bischof, as early as the time of King Réné, in the first
half of the fifteenth century, the plain of Paluns, near Marseilles, was
laid dry by boring, and Wittwer informs us that drainage is effected at
Munich by conducting the superfluous water into large excavations, from
which it filters through into a lower stratum of pebble and gravel lying
a little above the level of the river Isar.[326] So at Washington, in
the western part of the city, which lies high above the rivers Potomac
and Rock Creek, many houses are provided with dry wells for draining
their cellars and foundations. These extend through hard tenacious earth
to the depth of thirty or forty feet, when they strike a stratum of
gravel, through which the water readily passes off.
This practice has been extensively employed at Paris, not merely for
carrying off ordinary surface water, but for the discharge of offensive
and deleterious fluids from chemical and manufacturing establishments. A
well of this sort received, in the winter of 1832-'33, twenty thousand
gallons per day of the foul water from a starch factory, and the same
process was largely used in other factories. The apprehension of injury
to common and artesian wells and springs led to an investigation on this
subject, in behalf of the municipal authorities, by Girard and Parent
Duchatelet, in the latter year. The report of these gentlemen, published
in the _Annales des Ponts et Chaussées_ for 1833, second half year, is
full of curious and instructive facts respecting the position and
distribution of the subterranean waters under and near Paris; but it
must suffice to say that the report came to the conclusion that, in
consequence of the absolute immobility of these waters, and the
relatively small quantity of noxious fluid to be conveyed to them, there
was no danger of the diffusion of this latter, if discharged into them.
This result will not surprise those who know that, in another work,
Duchatelet maintains analogous opinions as to the effect of the
discharge of the city sewers into the Seine upon the waters of that
river. The quantity of matter delivered by them he holds to be so nearly
infinitesimal, as compared with the volume of water of the Seine, that
it cannot possibly affect it to a sensible degree. I would, however,
advise determined water drinkers living at Paris to adopt his
conclusions, without studying his facts and his arguments; for it is
quite possible that he may convert his readers to a faith opposite to
his own, and that they will finally agree with the poet who held water
an "ignoble beverage."
_Climatic and Geographical Effects of Surface Draining._
When we remove water from the surface, we diminish the evaporation from
it, and, of course, the refrigeration which accompanies all evaporation
is diminished in proportion. Hence superficial draining ought to be
attended with an elevation of atmospheric temperature, and, in cold
countries, it might be expected to lessen the frequency of frosts.
Accordingly, it is a fact of experience that, other things being equal,
dry soils, and the air in contact with them, are perceptibly warmer
during the season of vegetation, when evaporation is most rapid, than
moist lands and the atmospheric stratum resting upon them. Instrumental
observation on this special point has not yet been undertaken on a very
large scale, but still we have thermometric data sufficient to warrant
the general conclusion, and the influence of drainage in diminishing the
frequency of frost appears to be even better established than a direct
increase of atmospheric temperature. The steep and dry uplands of the
Green Mountain range in New England often escape frosts when the Indian
corn harvest on moister grounds, five hundred or even a thousand feet
lower, is destroyed or greatly injured by them. The neighborhood of a
marsh is sure to be exposed to late spring and early autumnal frosts,
but they cease to be feared after it is drained, and this is
particularly observable in very cold climates, as, for example, in
Lapland.[327]
In England, under-drains are not generally laid below the reach of daily
variations of temperature, or below a point from which moisture might be
brought to the surface by capillary attraction and evaporated by the
heat of the sun. They, therefore, like surface drains, withdraw from
local solar action much moisture which would otherwise be vaporized by
it, and, at the same time, by drying the soil above them, they increase
its effective hygroscopicity, and it consequently absorbs from the
atmosphere a greater quantity of water than it did when, for want of
under-drainage, the subsoil was always humid, if not saturated.
Under-drains, then, contribute to the dryness as well as to the warmth
of the atmosphere, and, as dry ground is more readily heated by the rays
of the sun than wet, they tend also to raise the mean, and especially
the summer temperature of the soil.
So far as respects the immediate improvement of soil and climate, and
the increased abundance of the harvests, the English system of surface
and subsoil drainage has fully justified the eulogiums of its advocates;
but its extensive adoption appears to have been attended with some
altogether unforeseen and undesirable consequences, very analogous to
those which I have described as resulting from the clearing of the
forests. The under-drains carry off very rapidly the water imbibed by
the soil from precipitation, and through infiltration from neighboring
springs or other sources of supply. Consequently, in wet seasons, or
after heavy rains, a river bordered by artificially drained lands
receives in a few hours, from superficial and from subterranean
conduits, an accession of water which, in the natural state of the
earth, would have reached it only by small instalments after percolating
through hidden paths for weeks or even months, and would have furnished
perennial and comparatively regular contributions, instead of swelling
deluges, to its channel. Thus, when human impatience rashly substitutes
swiftly acting artificial contrivances for the slow methods by which
nature drains the surface and superficial strata of a river basin, the
original equilibrium is disturbed, the waters of the heavens are no
longer stored up in the earth to be gradually given out again, but are
hurried out of man's domain with wasteful haste; and while the
inundations of the river are sudden and disastrous, its current, when
the drains have run dry, is reduced to a rivulet, it ceases to supply
the power to drive the machinery for which it was once amply sufficient,
and scarcely even waters the herds that pasture upon its margin.[328]
_Irrigation and its Climatic and Geographical Effects._
We know little of the history of the extinct civilizations which
preceded the culture of the classic ages, and no nation has, in modern
times, spontaneously emerged from barbarism, and created for itself the
arts of social life.[329] The improvements of the savage races whose
history we can distinctly trace are borrowed and imitative, and our
theories as to the origin and natural development of industrial art are
conjectural. Of course, the relative antiquity of particular branches of
human industry depends much upon the natural character of soil, climate,
and spontaneous vegetable and animal life in different countries; and
while the geographical influence of man would, under given
circumstances, be exerted in one direction, it would, under different
conditions, act in an opposite or a diverging line. I have given some
reasons for thinking that in the climates to which our attention has
been chiefly directed, man's first interference with the natural
arrangement and disposal of the waters was in the way of drainage of
surface. But if we are to judge from existing remains alone, we should
probably conclude that irrigation is older than drainage; for, in the
regions regarded by general tradition as the cradle of the human race,
we find traces of canals evidently constructed for the former purpose at
a period long preceding the ages of which we have any written memorials.
There are, in ancient Armenia, extensive districts which were already
abandoned to desolation at the earliest historical epoch, but which, in
a yet remoter antiquity, had been irrigated by a complicated and highly
artificial system of canals, the lines of which can still be followed;
and there are, in all the highlands where the sources of the Euphrates
rise, in Persia, in Egypt, in India, and in China, works of this sort
which must have been in existence before man had begun to record his own
annals.
In warm countries, such as most of those just mentioned, the effects I
have described as usually resulting from the clearing of the forests
would very soon follow. In such climates, the rains are inclined to be
periodical; they are also violent, and for these reasons the soil would
be parched in summer and liable to wash in winter. In these countries,
therefore, the necessity for irrigation must soon have been felt, and
its introduction into mountainous regions like Armenia must have been
immediately followed by a system of terracing, or at least scarping the
hillsides. Pasture and meadow, indeed, may be irrigated even when the
surface is both steep and irregular, as may be observed abundantly on
the Swiss as well as on the Piedmontese slope of the Alps; but in dry
climates, plough land and gardens on hilly grounds require terracing,
both for supporting the soil and for administering water by irrigation,
and it should be remembered that terracing, of itself, even without
special arrangements for controlling the distribution of water, prevents
or at least checks the flow of rain water, and gives it time to sink
into the ground instead of running off over the surface.
There are few things in Continental husbandry which surprise English or
American observers so much as the extent to which irrigation is employed
in agriculture, and that, too, on soils, and with a temperature, where
their own experience would have led them to suppose it would be
injurious to vegetation rather than beneficial to it. The summers in
Northern Italy, though longer, are very often not warmer than in New
England; and in ordinary years, the summer rains are as frequent and as
abundant in the former country as in the latter. Yet in Piedmont and
Lombardy, irrigation is bestowed upon almost every crop, while in New
England it is never employed at all in farming husbandry, or indeed for
any purpose except in kitchen gardens, and possibly, in rare cases, in
some other small branch of agricultural industry.[330]
The summers in Egypt, in Syria, and in Asia Minor and even Rumelia, are
almost rainless. In such climates, the necessity of irrigation is
obvious, and the loss of the ancient means of furnishing it readily
explains the diminished fertility of most of the countries in
question.[331] The surface of Palestine, for example, is composed, in a
great measure, of rounded limestone hills, once, no doubt, covered with
forests. These were partially removed before the Jewish conquest.[332]
When the soil began to suffer from drought, reservoirs to retain the
waters of winter were hewn in the rock near the tops of the hills, and
the declivities were terraced. So long as the cisterns were in good
order, and the terraces kept up, the fertility of Palestine was
unsurpassed, but when misgovernment and foreign and intestine war
occasioned the neglect or destruction of these works--traces of which
still meet the traveller's eye at every step,--when the reservoirs were
broken and the terrace walls had fallen down, there was no longer water
for irrigation in summer, the rains of winter soon washed away most of
the thin layer of earth upon the rocks, and Palestine was reduced almost
to the condition of a desert.
The course of events has been the same in Idumæa. The observing
traveller discovers everywhere about Petra, particularly if he enters
the city by the route of Wadi Ksheibeh, very extensive traces of ancient
cultivation, and upon the neighboring ridges are the ruins of numerous
cisterns evidently constructed to furnish a supply of water for
irrigation.[333] In primitive ages, the precipitation of winter in
these hilly countries was, in great part, retained for a time in the
superficial soil, first by the vegetable mould of the forests, and then
by the artificial arrangements I have described. The water imbibed by
the earth was partly taken up by direct evaporation, partly absorbed by
vegetation, and partly carried down by infiltration to subjacent strata
which gave it out in springs at lower levels, and thus a fertility of
soil and a condition of the atmosphere were maintained sufficient to
admit of the dense population that once inhabited those now arid wastes.
At present, the rain water runs immediately off from the surface and is
carried down to the sea, or is drunk up by the sands of the wadis, and
the hillsides which once teemed with plenty are bare of vegetation, and
seared by the scorching winds of the desert.
In Southern Europe, in the Turkish Empire, and in many other countries,
a very large proportion of the surface is, if not absolutely flooded, at
least thoroughly moistened by irrigation, a great number of times in the
course of every season, and this, especially, at periods when it would
otherwise be quite dry, and when, too, the power of the sun and the
capacity of the air for absorbing moisture are greatest. Hence it is
obvious that the amount of evaporation from the earth in these
countries, and, of course, the humidity and the temperature of both the
soil and the atmosphere in contact with it, must be much affected by the
practice of irrigation. The cultivable area of Egypt, or the space
accessible to cultivation, between desert and desert, is more than seven
thousand square statute miles. Much of the surface, though not out of
the reach of irrigation, lies too high to be economically watered, and
irrigation and cultivation are therefore confined to an area of five or
six thousand square miles, nearly the whole of which is regularly and
constantly watered when not covered by the inundation, except in the
short interval between the harvest and the rise of the waters. For
nearly half of the year, then, irrigation adds five or six thousand
square miles, or more than a square equatorial degree, to the evaporable
surface of the Nile valley, or, in other words, more than decuples the
area from which an appreciable quantity of moisture would otherwise be
evaporated; for after the Nile has retired within its banks, its waters
by no means cover one tenth of the space just mentioned.[334] The
fresh-water canals now constructing, in connection with the works for
the Suez canal, will not only restore the long abandoned fields east of
the Nile, but add to the arable soil of Egypt hundreds of square miles
of newly reclaimed desert, and thus still further increase the climatic
effects of irrigation.[335]
The Nile receives not a single tributary in its course through Egypt;
there is not so much as one living spring in the whole land,[336] and,
with the exception of a narrow strip of coast, where the annual
precipitation is said to amount to six inches, the fall of rain in the
territory of the Pharaohs is not two inches in the year. The subsoil of
the whole valley is pervaded with moisture by infiltration from the
Nile, and water can everywhere be found at the depth of a few feet. Were
irrigation suspended, and Egypt abandoned, as in that case it must be,
to the operations of nature, there is no doubt that trees, the roots of
which penetrate deeply, would in time establish themselves on the
deserted soil, fill the valley with verdure, and perhaps at last temper
the climate, and even call down abundant rain from the heavens.[337] But
the immediate effect of discontinuing irrigation would be, first, an
immense reduction of the evaporation from the valley in the dry season,
and then a greatly augmented dryness and heat of the atmosphere. Even
the almost constant north wind--the strength of which would be increased
in consequence of these changes--would little reduce the temperature of
the narrow cleft between the burning mountains which hem in the channel
of the Nile, so that a single year would transform the most fertile of
soils to the most barren of deserts, and render uninhabitable a
territory that irrigation makes capable of sustaining as dense a
population as has ever existed in any part of the world.[338] Whether
man found the valley of the Nile a forest, or such a waste as I have
just described, we do not historically know. In either case, he has not
simply converted a wilderness into a garden, but has unquestionably
produced extensive climatic change.[339]
The fields of Egypt are more regularly watered than those of any other
country bordering on the Mediterranean, except the rice grounds in
Italy, and perhaps the _marcite_ or winter meadows of Lombardy; but
irrigation is more or less employed throughout almost the entire basin
of that sea, and is everywhere attended with effects which, if less in
degree, are analogous in character to those resulting from it in Egypt.
In general, it may be said that the soil is nowhere artificially watered
except when it is so dry that little moisture would be evaporated from
it, and, consequently, every acre of irrigated ground is so much added
to the evaporable surface of the country. When the supply of water is
unlimited, it is allowed, after serving its purpose on one field, to run
into drains, canals, or rivers. But in most regions where irrigation is
regularly employed, it is necessary to economize the water; after
passing over or through one parcel of ground, it is conducted to
another; no more is withdrawn from the canals at any one point than is
absorbed by the soil it irrigates, or evaporated from it, and,
consequently, it is not restored to liquid circulation, except by
infiltration or precipitation. We are safe, then, in saying that the
humidity evaporated from any artificially watered soil is increased by a
quantity bearing a large proportion to the whole amount distributed over
it; for most even of that which is absorbed by the earth is immediately
given out again either by vegetables or by evaporation.
It is not easy to ascertain precisely either the extent of surface thus
watered, or the amount of water supplied, in any given country, because
these quantities vary with the character of the season; but there are
not many districts in Southern Europe where the management of the
arrangements for irrigation is not one of the most important branches of
agricultural labor. The eminent engineer Lombardini describes the system
of irrigation in Lombardy as, "every day in summer, diffusing over
550,000 hectares of land 45,000,000 cubic mètres of water, which is
equal to the entire volume of the Seine, at an ordinary flood, or a rise
of three mètres above the hydrometer at the bridge of La Tournelle at
Paris."[340] Niel states the quantity of land irrigated in the former
kingdom of Sardinia, including Savoy, in 1856, at 240,000 hectares, or
not much less than 600,000 acres. This is about four thirteenths of the
cultivable soil of the kingdom. According to the same author, the
irrigated lands in France did not exceed 100,000 hectares, or 247,000
acres, while those in Lombardy amounted to 450,000 hectares, more than
1,100,000 acres.[341] In these three states alone, then, there were more
than three thousand square miles of artificially watered land, and if we
add the irrigated soils of the rest of Italy, of the Mediterranean
islands, of the Spanish peninsula, of Turkey in Europe and in Asia
Minor, of Syria, of Egypt and the remainder of Northern Africa, we shall
see that irrigation increases the evaporable surface of the
Mediterranean basin by a quantity bearing no inconsiderable proportion
to the area naturally covered by water within it. As near as can be
ascertained, the amount of water applied to irrigated lands is scarcely
anywhere less than the total precipitation during the season of
vegetable growth, and in general it much exceeds that quantity. In grass
grounds and in field culture it ranges from 27 or 28 to 60 inches, while
in smaller crops, tilled by hand labor, it is sometimes carried as high
as 300 inches.[342] The rice grounds and the _marcite_ of Lombardy are
not included in these estimates of the amount of water applied.
Arrangements are concluded, and new plans proposed, for an immense
increase of the lands fertilized by irrigation in France and Italy, and
there is every reason to believe that the artificially watered soil of
the latter country will be doubled, that of France quadrupled, before
the end of this century. There can be no doubt that by these operations
man is exercising a powerful influence on soil, on vegetable and animal
life, and on climate, and hence that in this, as in many other fields of
industry, he is truly a geographical agency.[343] The quantity of water
artificially withdrawn from running streams for the purpose of
irrigation is such as very sensibly to affect their volume, and it is,
therefore, an important element in the geography of rivers. Brooks of no
trifling current are often wholly diverted from their natural channels
to supply the canals, and their entire mass of water completely
absorbed, so that it does not reach the river which it naturally feeds,
except in such proportion as it is conveyed to it by infiltration.
Irrigation, therefore, diminishes great rivers in warm countries by
cutting off their sources of supply as well as by direct abstraction of
water from their channels. We have just seen that the system of
irrigation in Lombardy deprives the Po of a quantity of water equal to
the total delivery of the Seine at ordinary flood, or, in other words,
of the equivalent of a tributary navigable for hundreds of miles by
vessels of considerable burden. The new canals commenced and projected
will greatly increase the loss. The water required for irrigation in
Egypt is less than would be supposed from the exceeding rapidity of
evaporation in that arid climate; for the soil is thoroughly saturated
during the inundation, and infiltration from the Nile continues to
supply a considerable amount of humidity in the dryest season. Linant
Bey computed that twenty-nine cubic mètres per day sufficed to irrigate
a hectare in the Delta.[344] This is equivalent to a fall of rain of two
millimètres and nine tenths per day, or, if we suppose water to be
applied for one hundred and fifty days during the dry season, to a total
precipitation of 435 millimètres, about seventeen inches and one third.
Taking the area of actually cultivated soil in Egypt at the low estimate
of 3,600,000 acres, and the average amount of water daily applied in
both Upper and Lower Egypt at twelve hundredths of an inch in depth, we
have an abstraction of 61,000,000 cubic yards, which--the mean daily
delivery of the Nile being in round numbers 320,000,000 cubic yards--is
nearly one fifth of the average quantity of water contributed to the
Mediterranean by that river.
Irrigation, as employed for certain special purposes in Europe and
America, is productive of very prejudicial climatic effects. I refer
particularly to the cultivation of rice in the Slave States of the
American Union and in Italy. The climate of the Southern States is not
necessarily unhealthy for the white man, but he can scarcely sleep a
single night in the vicinity of the rice grounds without being attacked
by a dangerous fever.[345] The neighborhood of the rice fields is less
pestilential in Lombardy and Piedmont than in South Carolina and
Georgia, but still very insalubrious to both man and beast. "Not only
does the population decrease where rice is grown," says Escourrou
Milliago, "but even the flocks are attacked by typhus. In the rice
grounds, the soil is divided into compartments rising in gradual
succession to the level of the irrigating canal, in order that the
water, after having flowed one field, may be drawn off to another, and
thus a single current serve for several compartments, the lowest field,
of course, still being higher than the ditch which at last drains both
it and the adjacent soil. This arrangement gives a certain force of
hydrostatic pressure to the water with which the rice is irrigated, and
the infiltration from these fields is said to extend through neighboring
grounds, sometimes to the distance of not less than a myriamètre, or six
English miles, and to be destructive to crops and even trees reached by
it. Land thus affected can no longer be employed for any purpose but
growing rice, and when prepared for that crop, it propagates still
further the evils under which it had itself suffered, and, of course,
the mischief is a growing one."[346]
The attentive traveller in Egypt and Nubia cannot fail to notice many
localities, generally of small extent, where the soil is rendered
infertile by an excess of saline matter in its composition. In many
cases, perhaps in all, these barren spots lie rather above the level
usually flooded by the inundations of the Nile, and yet they exhibit
traces of former cultivation. Recent observations in India, a notice of
which I find in an account of a meeting of the Asiatic Society in the
Athenæum of December 20, 1862, No. 1834, suggest a possible explanation
of this fact. At this meeting, Professor Medlicott read an essay on "the
saline efflorescence called 'Reh' and 'Kuller,'" which is gradually
invading many of the most fertile districts of Northern and Western
India, and changing them into sterile deserts. It consists principally
of sulphate of soda (Glauber's salts), with varying proportions of
common salt. Mr. Medlicott pronounces "these salts (which, in small
quantities are favorable to fertility of soil) to be the gradual result
of concentration by evaporation of river and canal waters, which contain
them in very minute quantities, and with which the lands are either
irrigated or occasionally overflowed." The river inundations in hot
countries usually take place but once in a year, and, though the banks
remain submerged for days or even weeks, the water at that period, being
derived principally from rains and snows, must be less highly charged
with mineral matter than at lower stages, and besides, it is always in
motion. The water of irrigation, on the other hand, is applied for many
months in succession, it is drawn from rivers at the seasons when their
proportion of salts is greatest, and it either sinks into the
superficial soil, carrying with it the saline substances it holds in
solution, or is evaporated from the surface, leaving them upon it. Hence
irrigation must impart to the soil more salts than natural inundation.
The sterilized grounds in Egypt and Nubia lying above the reach of the
floods, as I have said, we may suppose them to have been first
cultivated in that remote antiquity when the Nile valley received its
earliest inhabitants. They must have been artificially irrigated from
the beginning; they may have been under cultivation many centuries
before the soil at a lower level was invaded by man, and hence it is
natural that they should be more strongly impregnated with saline matter
than fields which are exposed every year, for some weeks, to the action
of running water so nearly pure that it would be more likely to dissolve
salts than to deposit them.
INUNDATIONS AND TORRENTS.
In pointing out in a former chapter the evils which have resulted from
the too extensive destruction of the forests, I dwelt at some length on
the increased violence of river inundations, and especially on the
devastations of torrents, in countries improvidently deprived of their
woods, and I spoke of the replanting of the forests as the only
effectual method of preventing the frequent recurrence of disastrous
floods. There are many regions where, from the loss of the superficial
soil, from financial considerations, and from other causes, the
restoration of the woods is not, under present circumstances, to be
hoped for. Even where that measure is feasible and in actual process of
execution, a great number of years must elapse before the action of the
destructive causes in question can be arrested or perhaps even sensibly
mitigated by it. Besides this, leaving out of view the objections urged
by Belgrand and his followers to the generally received opinions
concerning the beneficial influence of the forest as respects river
inundations--for no one disputes its importance in preventing the
formation and limiting the ravages of mountain torrents--floods will
always occur in years of excessive precipitation, whether the surface of
the soil be generally cleared or generally wooded.
Physical improvement in this respect, then, cannot he confined to
preventive measures, but, in countries subject to damage by inundation,
means must he contrived to obviate dangers and diminish injuries to
which human life and all the works of human industry will occasionally
be exposed, in spite of every effort to lessen the frequency of their
recurrence by acting directly on the causes that produce them. As every
civilized country is, in some degree, subject to inundation by the
overflow of rivers, the evil is a familiar one, and needs no general
description. In discussing this branch of the subject, therefore, I may
confine myself chiefly to the means that have been or may be employed to
resist the force and limit the ravages of floods, which, left wholly
unrestrained, would not only inflict immense injury upon the material
interests of man, but produce geographical revolutions of no little
magnitude.
a. _River Embankments._
The most obvious and doubtless earliest method of preventing the escape
of river waters from their natural channels, and the overflow of fields
and towns by their spread, is that of raised embankments along their
course. The necessity of such embankments usually arises from the
gradual elevation of the bed of running streams in consequence of the
deposit of the earth and gravel they are charged with in high water;
and, as we have seen, this elevation is rapidly accelerated when the
highlands around the headwaters of rivers are cleared of their forests.
When a river is embanked at a given point, and, consequently, the water
of its floods, which would otherwise spread over a wide surface, is
confined within narrow limits, the velocity of the current and its
transporting power are augmented, and its burden of sand and gravel is
deposited at some lower point, where the rapidity of its flow is
checked by a diminution in the inclination of the bed, by a wider
channel, or finally by a lacustrine or marine basin which receives its
waters. Wherever it lets fall solid material, its channel is raised in
consequence, and the declivity of the whole bed between the head of the
embankment and the slack of the stream is reduced. Hence the current, at
first accelerated by confinement, is afterward checked by the mechanical
resistance of the matter deposited, and by the diminished inclination of
its channel, and then begins again to let fall the earth it holds in
suspension, and to raise its bed at the point where its overflow had
been before prevented by embankment. The bank must now be raised in
proportion, and these processes would be repeated and repeated
indefinitely, had not nature provided a remedy in floods, which sweep
out recent deposits, burst the bonds of the river and overwhelm the
adjacent country with final desolation, or divert the current into a new
channel, destined to become, in its turn, the scene of a similar
struggle between man and the waters.
Few rivers, like the Nile, more than compensate by the fertilizing
properties of their water and their slime for the damage they may do in
inundations, and, consequently, there are few whose floods are not an
object of dread, few whose encroachments upon their banks are not a
source of constant anxiety and expense to the proprietors of the lands
through which they flow. River dikes, for confining the spread of
currents at high water, are of great antiquity in the East, and those of
the Po and its tributaries were begun before we have any trustworthy
physical or political annals of the provinces upon their borders. From
the earliest ages, the Italian hydraulic engineers have stood in the
front rank of their profession, and the Italian literature of this
branch of material improvement is exceedingly voluminous. But the
countries for which I write have no rivers like the Po, no plains like
those of Lombardy, and the dangers to which the inhabitants of English
and American river banks are exposed are more nearly analogous to those
that threaten the soil and population in the valleys and plains of
France, than to the perils and losses of the Lombard. The writings of
the Italian hydrographers, too, though rich in professional instruction,
are less accessible to foreigners and less adapted to popular use than
those of French engineers.[347] For these reasons I shall take my
citations principally from French authorities, though I shall
occasionally allude to Italian writers on the floods of the Tiber, of
the Arno, and some other Italian streams which much resemble those of
the rivers of England and the United States.
b. _Floods of the Ardèche._
The floods of mountain streams are attended with greater immediate
danger to life and property than those of rivers of less rapid flow,
because their currents are more impetuous, and they rise more suddenly
and with less previous warning. At the same time, their ravages are
confined within narrower limits, the waters retire sooner to their
accustomed channel, and the danger is more quickly over, than in the
case of inundations of larger rivers. The Ardèche, which has given its
name to a department in France, drains a basin of 600,238 acres, or a
little less than nine hundred and thirty-eight square miles. Its
remotest source is about seventy-five miles, in a straight line, from
its junction with the Rhone, and springs at an elevation of four
thousand feet above that point. At the lowest stage of the river, the
bed of the Chassezac, its largest and longest tributary, is in many
places completely dry on the surface--the water being sufficient only
to supply the subterranean channels of infiltration--and the Ardèche
itself is almost everywhere fordable, even below the mouth of the
Chassezac. But in floods, the river has sometimes risen more than sixty
feet at the Pont d'Arc, a natural arch of two hundred feet chord, which
spans the stream below its junction with all its important affluents. At
the height of the inundation of 1827, the quantity of water passing this
point--after deducting thirty per cent. for material transported with
the current and for irregularity of flow--was estimated at 8,845 cubic
yards to the second, and between twelve at noon on the 10th of September
of that year and ten o'clock the next morning, the water discharged
through the passage in question amounted to more than 450,000,000 cubic
yards. This quantity, distributed equally through the basin of the
river, would cover its entire area to a depth of more than five inches.
The Ardèche rises so suddenly that, in the inundation of 1846, the women
who were washing in the bed of the river had not time to save their
linen, and barely escaped with their lives, though they instantly fled
upon hearing the roar of the approaching flood. Its waters and those of
its affluents fall almost as rapidly, for in less than twenty-four hours
after the rain has ceased in the Cévennes, where it rises, the Ardèche
returns within its ordinary channel, even at its junction with the
Rhone. In the flood of 1772, the water at La Beaume de Ruoms, on the
Beaume, a tributary of the Ardèche, rose thirty-five feet above low
water, but the stream was again fordable on the evening of the same day.
The inundation of 1827 was, in this respect, exceptional, for it
continued three days, during which period the Ardèche poured into the
Rhone 1,305,000,000 cubic yards of water.
The Nile delivers into the sea 101,000 cubic feet or 3,741 cubic yards
per second, on an average of the whole year.[348] This is equal to
323,222,400 cubic yards per day. In a single day of flood, then, the
Ardèche, a river too insignificant to be known except in the local
topography of France, contributed to the Rhone once and a half, and for
three consecutive days once and one third, as much as the average
delivery of the Nile during the same periods, though the basin of the
latter river contains 500,000 square miles of surface, or more than five
hundred times as much as that of the former.
The average annual precipitation in the basin of the Ardèche is not
greater than in many other parts of Europe, but excessive quantities of
rain frequently fall in that valley in the autumn. On the 9th of
October, 1827, there fell at Joyeuse, on the Beaume, no less than
thirty-one inches between three o'clock in the morning and midnight.
Such facts as this explain the extraordinary suddenness and violence of
the floods of the Ardèche, and the basins of many other tributaries of
the Rhone exhibit meteorological phenomena not less remarkable.[349] The
inundation of the 10th September, 1857, was accompanied with a terrific
hurricane, which passed along the eastern slope of the high grounds
where the Ardèche and several other western affluents of the Rhone take
their rise. The wind tore up all the trees in its path, and the rushing
torrents bore their trunks down to the larger streams, which again
transported them to the Rhone in such rafts that one might almost have
crossed that river by stepping from trunk to trunk.[350] The Rhone,
therefore, is naturally subject to great and sudden inundations, and the
same remark may be applied to most of the principal rivers of France,
because the geographical character of all of them is approximately the
same.
The height and violence of the inundations of most great rivers are
determined by the degree in which the floods of the different
tributaries are coincident in time. Were all the affluents of the Rhone
to pour their highest annual floods into its channel at once, were a
dozen Niles to empty themselves into its bed at the same moment, its
water would rise to a height and rush with an impetus that would sweep
into the Mediterranean the entire population of its banks, and all the
works that man has erected upon the plains which border it. But such a
coincidence can never happen. The tributaries of this river run in very
different directions, and some of them are swollen principally by the
melting of the snows about their sources, others almost exclusively by
heavy rains. When a damp southeast wind blows up the valley of the
Ardèche, its moisture is condensed, and precipitated in a deluge upon
the mountains which embosom the headwaters of that stream, thus
producing a flood, while a neighboring basin, the axis of which lies
transversely or obliquely to that of the Ardèche, is not at all
affected.[351]
It is easy to see that the damage occasioned by such floods as I have
described must be almost incalculable, and it is by no means confined to
the effects produced by overflow and the mechanical force of the
superficial currents. In treating of the devastations of torrents in a
former chapter, I confined myself principally to the erosion of surface
and the transportation of mineral matter to lower grounds by them. The
general action of torrents, as there shown, tends to the ultimate
elevation of their beds by the deposit of the earth, gravel, and stone
conveyed by them; but until they have thus raised their outlets so as
sensibly to diminish the inclination of their channels--and sometimes
when extraordinary floods give the torrents momentum enough to sweep
away the accumulations which they have themselves heaped up--the swift
flow of their currents, aided by the abrasion of the rolling rocks and
gravel, scoops their beds constantly deeper, and they consequently not
only undermine their banks, but frequently sap the most solid
foundations which the art of man can build for the support of bridges
and hydraulic structures.[352]
In the inundation of 1857, the Ardèche destroyed a stone bridge near La
Beaume, which had been built about eighty years before. The resistance
of the piers, which were erected on piles, the channel at that point
being of gravel, produced an eddying current that washed away the bed of
the river above them, and the foundation, thus deprived of lateral
support, yielded to the weight of the bridge, and the piles and piers
fell up stream.
By a curious law of compensation, the stream which, at flood, scoops out
cavities in its bed, often fills them up again as soon as the diminished
velocity of the current allows it to let fall the sand and gravel with
which it is charged, so that when the waters return to their usual
channel, the bottom shows no sign of having been disturbed. In a flood
of the Escontay, a tributary of the Rhone, in 1846, piles driven sixteen
feet into its gravelly bed for the foundation of a pier were torn up and
carried off, and yet, when the river had fallen to low-water mark, the
bottom at that point appeared to have been raised higher than it was
before the flood, by new deposits of sand and gravel, while the cut
stones of the half-built pier were found buried to a great depth, in the
excavation which the water had first washed out. The gravel with which
rivers thus restore the level of their beds is principally derived from
the crushing of the rocks brought down by the mountain torrents, and the
destructive effects of inundations are immensely diminished by this
reduction of large stones to minute fragments. If the blocks hurled down
from the cliffs were transported unbroken to the channels of large
rivers, the mechanical force of their movement would be irresistible.
They would overthrow the strongest barriers, spread themselves over a
surface as wide as the flow of the waters, and convert the most smiling
valleys into scenes of the wildest desolation.
c. _Crushing Force of Torrents._
There are few operations of nature where the effect seems more
disproportioned to the cause than in the comminution of rock in the
channel of swift waters. Igneous rocks are generally so hard as to be
wrought with great difficulty, and they bear the weight of enormous
superstructures without yielding to the pressure; but to the torrent
they are as wheat to the millstone. The streams which pour down the
southern scarp of the Mediterranean Alps along the Riviera di Ponente,
near Genoa, have short courses, and a brisk walk of a couple of hours or
even less takes you from the sea beach to the headspring of many of
them. In their heaviest floods, they bring rounded masses of serpentine
quite down to the sea, but at ordinary high water their lower course is
charged only with finely divided particles of that rock. Hence, while,
near their sources, their channels are filled with pebbles and angular
fragments, intermixed with a little gravel, the proportions are reversed
near their mouths, and, just above the points where their outlets are
partially choked by the rolling shingle of the beach, their beds are
composed of sand and gravel to the almost total exclusion of pebbles.
The greatest depth of the basin of the Ardèche is seventy-five miles,
but most of its tributaries have a much shorter course. "These
affluents," says Mardigny, "hurl into the bed of the Ardèche enormous
blocks of rock, which this river, in its turn, bears onward, and grinds
down, at high water, so that its current rolls only gravel at its
confluence with the Rhone."[353]
Guglielmini argued that the gravel and sand of the beds of running
streams were derived from the trituration of rocks by the action of the
currents, and inferred that this action was generally sufficient to
reduce hard rock to sand in its passage from the source to the outlet of
rivers. Frisi controverted this opinion, and maintained that river sand
was of more ancient origin, and he inferred from experiments in
artificially grinding stones that the concussion, friction, and
attrition of rock in the channel of running waters were inadequate to
its comminution, though he admitted that these same causes might reduce
silicious sand to a fine powder capable of transportation to the sea by
the currents.[354] Frisi's experiments were tried upon rounded and
polished river pebbles, and prove nothing with regard to the action of
torrents upon the irregular, more or less weathered, and often cracked
and shattered rocks which lie loose in the ground at the head of
mountain valleys. The fury of the waters and of the wind which
accompanies them in the floods of the French Alpine torrents is such,
that large blocks of stone are hurled out of the bed of the stream to
the height of twelve or thirteen feet. The impulse of masses driven with
such force overthrows the most solid masonry, and their concussion
cannot fail to be attended with the crushing of the rocks
themselves.[355]
d. _Inundations of 1856 in France._
The month of May, 1856, was remarkable for violent and almost
uninterrupted rains, and most of the river basins of France were
inundated to an extraordinary height. In the valleys of the Loire and
its affluents, about a million of acres, including many towns and
villages, were laid under water, and the amount of pecuniary damage was
almost incalculable.[356] The flood was not less destructive in the
valley of the Rhone, and in fact an invasion by a hostile army could
hardly have been more disastrous to the inhabitants of the plains than
was this terrible deluge. There had been a flood of this latter river in
the year 1840, which, for height and quantity of water, was almost as
remarkable as that of 1856, but it took place in the month of November,
when the crops had all been harvested, and the injury inflicted by it
upon agriculturists was, therefore, of a character to be less severely
and less immediately felt than the consequences of the inundation of
1856.[357]
In the fifteen years between these two great floods, the population and
the rural improvements of the river valleys had much increased, common
roads, bridges, and railways had been multiplied and extended, telegraph
lines had been constructed, all of which shared in the general ruin, and
hence greater and more diversified interests were affected by the
catastrophe of 1856 than by any former like calamity. The great flood of
1840 had excited the attention and roused the sympathies of the French
people, and the subject was invested with new interest by the still more
formidable character of the inundations of 1856. It was felt that these
scourges had ceased to be a matter of merely local concern, for,
although they bore most heavily on those whose homes and fields were
situated within the immediate reach of the swelling waters, yet they
frequently destroyed harvests valuable enough to be a matter of national
interest, endangered the personal security of the population of
important political centres, interrupted communication for days and even
weeks together on great lines of traffic and travel--thus severing as
it were all Southwestern France from the rest of the empire--and finally
threatened to produce great and permanent geographical changes. The
well-being of the whole commonwealth was seen to be involved in
preventing the recurrence, and in limiting the range of such
devastations. The Government encouraged scientific investigation of the
phenomena and their laws. Their causes, their history, their immediate
and remote consequences, and the possible safeguards to be employed
against them, have been carefully studied by the most eminent
physicists, as well as by the ablest theoretical and practical engineers
of France. Many hitherto unobserved facts have been collected, many new
hypotheses suggested, and many plans, more or less original in
character, have been devised for combating the evil; but thus far, the
most competent judges are not well agreed as to the mode, or even the
possibility, of applying a remedy.
e. _Remedies against Inundations._
Perhaps no one point has been more prominent in the discussions than the
influence of the forest in equalizing and regulating the flow of the
water of precipitation. As we have already seen, opinion is still
somewhat divided on this subject, but the conservative action of the
woods in this respect has been generally recognized by the public of
France, and the Government of the empire has made this principle the
basis of important legislation for the protection of existing forests,
and for the formation of new. The clearing of woodland, and the
organization and functions of a police for its protection, are regulated
by a law bearing date June 18th, 1859, and provision was made for
promoting the restoration of private woods by a statute adopted on the
28th of July, 1860. The former of these laws passed the legislative body
by a vote of 246 against 4, the latter with but a single negative voice.
The influence of the government, in a country where the throne is so
potent as in France, would account for a large majority, but when it is
considered that both laws, the former especially, interfere very
materially with the rights of private domain, the almost entire
unanimity with which they were adopted is proof of a very general
popular conviction, that the protection and extension of the forests is
a measure more likely than any other to check the violence, if not to
prevent the recurrence, of destructive inundations. The law of July
28th, 1860, appropriated 10,000,000 francs, to be expended, at the rate
of 1,000,000 francs per year, in executing or aiding the replanting of
woods. It is computed that this appropriation will secure the creation
of new forest to the extent of about 250,000 acres, or one eleventh part
of the soil where the restoration of the forest is thought feasible and,
at the same time, specially important as a security against the evils
ascribed in a great measure to its destruction.
The provisions of the laws in question are preventive rather than
remedial; but some immediate effect may be expected to result from them,
particularly if they are accompanied with certain other measures, the
suggestion of which has been favorably received. The strong repugnance
of the mountaineers to the application of a system which deprives them
of a part of their pasturage--for the absolute exclusion of domestic
animals is indispensable to the maintenance of an existing forest and to
the formation of a new--is the most formidable obstacle to the execution
of the laws of 1859-'60. It is proposed to compensate this loss by a
cheap system of irrigation of lower pasture grounds, consisting in
little more than in running horizontal furrows along the hillsides, thus
converting the scarp of the hills into a succession of small terraces
which, when once turfed over, are very permanent. Experience is said to
have demonstrated that this simple process suffices to retain the water
of rains, of snows, and of small springs and rivulets, long enough for
the irrigation of the soil, thus increasing its product of herbage in a
fivefold proportion, and that it partially checks the too rapid flow of
surface water into the valleys, and, consequently, in some measure
obviates one of the most prominent causes of inundations.[358] It is
evident that, if such results are produced by this method, its
introduction upon an extensive scale must also have the same climatic
effects as other systems of irrigation.
Whatever may be the ultimate advantages of reclothing a large extent of
the territory of France with wood, or of so shaping its surface as to
prevent the too rapid flow of water over it, the results to be obtained
by such processes can be realized in an adequate measure only after a
long succession of years. Other steps must be taken, both for the
immediate security of the lives and property of the present generation,
and for the prevention of yet greater and remoter evils which are
inevitable unless means to obviate them are found before it is forever
too late. The frequent recurrence of inundations like those of 1856, for
a single score of years, in the basins of the Rhone and the Loire, with
only the present securities against them, would almost depopulate the
valleys of those rivers, and produce physical revolutions in them,
which, like revolutions in the political world, could never be made to
"go backward."
Destructive inundations are seldom, if ever, produced by precipitation
within the limits of the principal valley, but almost uniformly by
sudden thaws or excessive rains on the mountain ranges where the
tributaries take their rise. It is therefore plain that any measures
which shall check the flow of surface waters into the channels of the
affluents, or which shall retard the delivery of such waters into the
principal stream by its tributaries, will diminish in the same
proportion the dangers and the evils of inundation by great rivers. The
retention of the surface waters upon or in the soil can hardly be
accomplished except by the methods already mentioned, replanting of
forests, and furrowing or terracing. The current of mountain streams can
be checked by various methods, among which the most familiar and obvious
is the erection of barriers or dams across their channels, at points
convenient for forming reservoirs large enough to retain the superfluous
waters of great rains and thaws. Besides the utility of such basins in
preventing floods, the construction of them is recommended by very
strong considerations, such as the meteorological effects of increased
evaporable surface, the furnishing of a constant supply of water for
agricultural and mechanical purposes, and, finally, their value as ponds
for breeding and rearing fish, and, perhaps, for cultivating aquatic
vegetables.
The objections to the general adoption of the system of reservoirs are
these: the expense of their construction and maintenance; the reduction
of cultivable area by the amount of surface they must cover; the
interruption they would occasion to free communication; the probability
that they would soon be filled up with sediment, and the obvious fact
that when full of earth or even water, they would no longer serve their
principal purpose; the great danger to which they would expose the
country below them in case of the bursting of their barriers;[359] the
evil consequences they would occasion by prolonging the flow of
inundations in proportion as they diminished their height; the injurious
effects it is supposed they would produce upon the salubrity of the
neighboring districts; and, lastly, the alleged impossibility of
constructing artificial basins sufficient in capacity to prevent, or in
any considerable measure to mitigate, the evils they are intended to
guard against.
The last argument is more easily reduced to a numerical question than
the others. The mean and extreme annual precipitation of all the basins
where the construction of such works would be seriously proposed is
already approximately known by meteorological tables, and the quantity
of water, delivered by the greatest floods which have occurred within
the memory of man, may be roughly estimated from their visible traces.
From these elements, or from recorded observations, the capacity of the
necessary reservoirs can be calculated. Let us take the case of the
Ardèche. In the inundation of 1857, that river poured into the Rhone
1,305,000,000 cubic yards of water in three days. If we suppose that
half this quantity might have been suffered to flow down its channel
without inconvenience, we shall have about 650,000,000 cubic yards to
provide for by reservoirs. The Ardèche and its principal affluent, the
Chassezac, have, together, about twelve considerable tributaries rising
near the crest of the mountains which bound the basin. If reservoirs of
equal capacity were constructed upon all of them, each reservoir must be
able to contain 54,000,000 cubic yards, or, in other words, must be
equal to a lake 3,000 yards long, 1,000 yards wide, and 18 yards deep,
and besides, in order to render any effectual service, the reservoirs
must all have been empty at the commencement of the rains which produced
the inundation.
Thus far, I have supposed the swelling of the waters to be uniform
throughout the whole basin; but such was by no means the fact in the
inundation of 1857, for the rise of the Chassezac, which is as large as
the Ardèche proper, did not exceed the limits of ordinary floods, and
the dangerous excess came solely from the headwaters of the latter
stream. Hence reservoirs of double the capacity I have supposed would
have been necessary upon the tributaries of that river, to prevent the
injurious effects of the inundation. It is evident that the construction
of reservoirs of such magnitude for such a purpose is financially, if
not physically, impracticable, and when we take into account a point I
have just suggested, namely, that the reservoirs must be empty at all
times of apprehended flood, and, of course, their utility limited almost
solely to the single object of preventing inundations, the total
inapplicability of such a measure in this particular case becomes still
more glaringly manifest.
Another not less conclusive fact is that the valleys of all the upland
tributaries of the Ardèche descend so rapidly, and have so little
lateral expansion, as to render the construction of capacious reservoirs
in them quite impracticable. Indeed, engineers have found but two points
in the whole basin suitable for that purpose, and the reservoirs
admissible at these would have only a joint capacity of about 70,000,000
cubic yards, or less than one ninth part of what I suppose to be
required. The case of the Ardèche is no doubt an extreme one, both in
the topographical character of its basin and in its exposure to
excessive rains; but all destructive inundations are, in a certain
sense, extreme cases also, and this of the Ardèche serves to show that
the construction of reservoirs is not by any means to be regarded as a
universal panacea against floods.
Nor, on the other hand, is this measure to be summarily rejected. Nature
has adopted it on a great scale, on both flanks of the Alps, and on a
smaller, on those of the Adirondacks and lower chains, and in this as in
many other instances, her processes may often be imitated with
advantage. The validity of the remaining objections to the system under
discussion depends on the topography, geology, and special climate of
the regions where it is proposed to establish such reservoirs. Many
upland streams present numerous points where none of these objections,
except those of expense and of danger from the breaking of dams, could
have any application. Reservoirs may be so constructed as to retain the
entire precipitation of the heaviest thaws and rains, leaving only the
ordinary quantity to flow along the channel; they may be raised to such
a height as only partially to obstruct the surface drainage; or they may
be provided with sluices by means of which their whole contents can be
discharged in the dry season and a summer crop be grown upon the ground
they cover at high water. The expediency of employing them and the mode
of construction depend on local conditions, and no rules of universal
applicability can be laid down on the subject.
It is remarkable that nations which we, in the false pride of our modern
civilization, so generally regard as little less than barbarian, should
have long preceded Christian Europe in the systematic employment of
great artificial basins for the various purposes they are calculated to
subserve. The ancient Peruvians built strong walls, of excellent
workmanship, across the channels of the mountain sources of important
streams, and the Arabs executed immense works of similar description,
both in the great Arabian peninsula and in all the provinces of Spain
which had the good fortune to fall under their sway. The Spaniards of
the fifteenth and sixteenth centuries, who, in many points of true
civilization and culture, were far inferior to the races they subdued,
wantonly destroyed these noble monuments of social and political wisdom,
or suffered them to perish, because they were too ignorant to appreciate
their value, or too unskilful as practical engineers to be able to
maintain them, and some of their most important territories were soon
reduced to sterility and poverty in consequence.
Another method of preventing or diminishing the evils of inundation by
torrents and mountain rivers, analogous to that employed for the
drainage of lakes, consists in the permanent or occasional diversion of
their surplus waters, or of their entire currents, from their natural
courses, by tunnels or open channels cut through their banks. Nature, in
many cases, resorts to a similar process. Most great rivers divide
themselves into several arms in their lower course, and enter the sea by
different mouths. There are also cases where rivers send off lateral
branches to convey a part of their waters into the channel of other
streams.[360] The most remarkable of these is the junction between the
Amazon and the Orinoco by the natural canal of the Cassiquiare and the
Rio Negro. In India, the Cambodja and the Menam are connected by the
Anam; the Saluen and the Irawaddi by the Panlaun. There are similar
examples, though on a much smaller scale, in Europe. The Torneå and the
Calix rivers in Lapland communicate by the Tarando, and in Westphalia,
the Else, an arm of the Haase, falls into the Weser.
The change of bed in rivers by gradual erosion of their banks is
familiar to all, but instances of the sudden abandonment of a primitive
channel are by no means wanting. At a period of unknown antiquity, the
Ardèche pierced a tunnel 200 feet wide and 100 high, through a rock, and
sent its whole current through it, deserting its former bed, which
gradually filled up, though its course remained traceable. In the great
inundation of 1827, the tunnel proved insufficient for the discharge of
the water, and the river burst through the obstructions which had now
choked up its ancient channel, and resumed its original course.[361]
It was probably such facts as these that suggested to ancient engineers
the possibility of like artificial operations, and there are numerous
instances of the execution of works for this purpose in very remote
ages. The Bahr Jusef, the great stream which supplies the Fayoum with
water from the Nile, has been supposed, by some writers, to be a natural
channel; but both it and the Bahr el Wady are almost certainly
artificial canals constructed to water that basin, to regulate the level
of Lake Moeris, and possibly, also, to diminish the dangers resulting
from excessive inundations of the Nile, by serving as waste-weirs to
discharge a part of its surplus waters. Several of the seven ancient
mouths of the Nile are believed to be artificial channels, and Herodotus
even asserts that King Menes diverted the entire course of that river
from the Libyan to the Arabian side of the valley. There are traces of
an ancient river bed along the western mountains, which give some
countenance to this statement. But it is much more probable that the
works of Menes were designed rather to prevent a natural, than to
produce an artificial, change in the channel of the river.
Two of the most celebrated cascades in Europe, those of the Teverone at
Tivoli and of the Velino at Terni, owe, if not their existence, at least
their position and character, to the diversion of their waters from
their natural beds into new channels, in order to obviate the evils
produced by their frequent floods. Remarkable works of the same sort
have been executed in Switzerland, in very recent times. Until the year
1714, the Kander, which drains several large Alpine valleys, ran, for a
considerable distance, parallel with the Lake of Thun, and a few miles
below the city of that name emptied into the river Aar. It frequently
flooded the flats along the lower part of its course, and it was
determined to divert it into the Lake of Thun. For this purpose, two
parallel tunnels were cut through the intervening rock, and the river
turned into them. The violence of the current burst up the roof of the
tunnels, and, in a very short time, wore the new channel down not less
than one hundred feet, and even deepened the former bed at least fifty
feet, for a distance of two or three miles above the tunnel. The lake
was two hundred feet deep at the point where the river was conducted
into it, but the gravel and sand carried down by the Kander has formed
at its mouth a delta containing more than a hundred acres, which is
still advancing at the rate of several yards a year. The Linth, which
formerly sent its waters directly to the Lake of Zurich, and often
produced very destructive inundations, was turned into the Wallensee
about forty years ago, and in both these cases a great quantity of
valuable land was rescued both from flood and from insalubrity.
In Switzerland, the most terrible inundations often result from the
damming up of deep valleys by ice slips or by the gradual advance of
glaciers, and the accumulation of great masses of water above the
obstructions. The ice is finally dissolved by the heat of summer or the
flow of warm waters, and when it bursts, the lake formed above is
discharged almost in an instant, and all below is swept down to certain
destruction. In 1595, about a hundred and fifty lives and a great amount
of property were lost by the eruption of a lake formed by the descent of
a glacier into the valley of the Drance, and a similar calamity laid
waste a considerable extent of soil in the year 1818. On this latter
occasion, the barrier of ice and snow was 3,000 feet long, 600 thick,
and 400 high, and the lake which had formed above it contained not less
than 800,000,000 cubic feet. A tunnel was driven through the ice, and
about 300,000,000 cubic feet of water safely drawn off by it, but the
thawing of the walls of the tunnel rapidly enlarged it, and before the
lake was half drained, the barrier gave way and the remaining
500,000,000 cubic feet of water were discharged in half an hour. The
recurrence of these floods has since been prevented by directing streams
of water, warmed by the sun, upon the ice in the bed of the valley, and
thus thawing it before it accumulates in sufficient mass to threaten
serious danger.
In the cases of diversion of streams above mentioned, important
geographical changes have been directly produced by those operations. By
the rarer process of draining glacier lakes, natural eruptions of water,
which would have occasioned not less important changes in the face of
the earth, have been prevented by human agency.
The principal means hitherto relied upon for defence against river
inundations has been the construction of dikes along the banks of the
streams, parallel to the channel and generally separated from each other
by a distance not much greater than the natural width of the bed.[362]
If such walls are high enough to confine the water and strong enough to
resist its pressure, they secure the lands behind them from all the
evils of inundation except those resulting from infiltration; but such
ramparts are enormously costly in original construction and maintenance,
and, as we have already seen, the filling up of the bed of the river in
its lower course, by sand and gravel, involves the necessity of
occasionally incurring new expenditures in increasing the height of the
banks.[363] They are attended, too, with some collateral disadvantages.
They deprive the earth of the fertilizing deposits of the waters, which
are powerful natural restoratives of soils exhausted by cultivation;
they accelerate the rapidity and transporting power of the current at
high water by confining it to a narrower channel, and it consequently
conveys to the sea the earthy matter it holds in suspension, and chokes
up harbors with a deposit which it would otherwise have spread over a
wide surface; they interfere with roads and the convenience of river
navigation, and no amount of cost or care can secure them from
occasional rupture, in case of which the rush of the waters through the
breach is more destructive than the natural flow of the highest
inundation.[364]
For these reasons, many experienced engineers are of opinion that the
system of longitudinal dikes ought to be abandoned, or, where that
cannot be done without involving too great a sacrifice of existing
constructions, their elevation should be much reduced, so as to present
no obstruction to the lateral spread of extraordinary floods, and they
should be provided with sluices to admit the water without violence
whenever they are likely to be overflowed. Where dikes have not been
erected, and where they have been reduced in height, it is proposed to
construct, at convenient intervals, transverse embankments of moderate
height running from the banks of the river across the plains to the
hills which bound them. These measures, it is argued, will diminish the
violence of inundations by permitting the waters to extend themselves
over a greater surface and thus retarding the flow of the river
currents, and will, at the same time, secure the deposit of fertilizing
slime upon all the soil covered by the flood.
Rozet, an eminent French engineer, has proposed a method of diminishing
the ravages of inundations, which aims to combine the advantages of all
other systems, and at the same time to obviate the objections to which
they are all more or less liable.[365] The plan of Rozet is recommended
by its simplicity and cheapness as well as its facility and rapidity of
execution, and is looked upon with favor by many persons very competent
to judge in such matters. He proposes to commence with the amphitheatres
in which mountain torrents so often rise, by covering their slopes and
filling their beds with loose blocks of rock, and by constructing at
their outlets, and at other narrow points in the channels of the
torrents, permeable barriers of the same material promiscuously heaped
up, much according to the method employed by the ancient Romans in their
northern provinces for a similar purpose. By this means, he supposes,
the rapidity of the current would be checked, and the quantity of
transported pebbles and gravel much diminished.
When the stream has reached that part of its course where it is bordered
by soil capable of cultivation, and worth the expense of protection, he
proposes to place along one or both sides of the stream, according to
circumstances, a line of cubical blocks of stone or pillars of masonry
three or four feet high and wide, and at the distance of about eleven
yards from each other. The space between the two lines, or between a
line and the opposite high bank, would, of course, be determined by
observation of the width of the swift-water current at high floods. As
an auxiliary measure, small ditches and banks, or low walls of pebbles,
should be constructed from the line of blocks across the grounds to be
protected, nearly at right angles to the current, but slightly inclining
downward, and at convenient distances from each other. Rozet thinks the
proper interval would be 300 yards, and it is evident that, if he is
right in his main principle, hedges, rows of trees, or even common
fences, would in many cases answer as good a purpose as banks and
trenches or low walls. The blocks or pillars of stone would, he
contends, check the lateral currents so as to compel them to let fall
all their pebbles and gravel in the main channel--where they would be
rolled along until ground down to sand or silt--and the transverse
obstructions would detain the water upon the soil long enough to secure
the deposit of its fertilizing slime. Numerous facts are cited in
support of the author's views, and I imagine there are few residents of
rural districts whose own observation will not furnish testimony
confirmatory of their soundness.[366]
The deposit of slime by rivers upon the flats along their banks not only
contributes greatly to the fertility of the soil thus flowed, but it
subserves a still more important purpose in the general economy of
nature. All running streams begin with excavating channels for
themselves, or deepening the natural depressions in which they
flow;[367] but in proportion as their outlets are raised by the solid
material transported by their currents, their velocity is diminished,
they deposit gravel and sand at constantly higher and higher points, and
so at last elevate, in the middle and lower part of their course, the
beds they had previously scooped out.[368] The raising of the channels
is compensated in part by the simultaneous elevation of their banks and
the flats adjoining them, from the deposit of the finer particles of
earth and vegetable mould brought down from the mountains, without which
elevation the low grounds bordering all rivers would be, as in many
cases they in fact are, mere morasses.
All arrangements which tend to obstruct this process of raising the
flats adjacent to the channel, whether consisting in dikes which confine
the waters, and, at the same time, augment the velocity of the current,
or in other means of producing the last-mentioned effect, interfere with
the restorative economy of nature, and at last occasion the formation of
marshes where, if left to herself, she would have accumulated
inexhaustible stores of the richest soil, and spread them out in plains
above the reach of ordinary floods.[369]
_Consequences if the Nile had been Diked._
If a system of continuous lateral dikes, like those of the Po, had been
adopted in Egypt in the early dynasties, when the power and the will to
undertake the most stupendous material enterprises were so eminently
characteristic of the government of that country, and the waters of the
annual inundation consequently prevented from flooding the land, it is
conceivable that the productiveness of the small area of cultivable soil
in the Nile valley might have been long kept up by artificial irrigation
and the application of manures. But nature would have rebelled at last,
and centuries before our time the mighty river would have burst the
fetters by which impotent man had vainly striven to bind his swelling
floods, the fertile fields of Egypt would have been converted into dank
morasses, and then, perhaps, in some distant future, when the expulsion
of man should have allowed the gradual restoration of the primitive
equilibrium, would be again transformed into luxuriant garden and plough
land. Fortunately, the "wisdom of Egypt" taught her children better
things. They invited and welcomed, not repulsed, the slimy embraces of
Nilus, and his favors have been, from the hoariest antiquity, the
greatest material blessing ever bestowed upon a people.[370]
The valley of the Po has probably not been cultivated or inhabited so
long as that of the Nile, but embankments have been employed on its
lower course for at least two thousand years, and for many centuries
they have been connected in a continuous chain. I have pointed out in a
former chapter the effects produced on the geography of the Adriatic by
the deposit of river sediment in the sea at the mouths of the Po, the
Adige, and the Brenta. If these rivers had been left unconfined, like
the Nile, and allowed to spread their muddy waters at will, according to
the laws of nature, the slime they have carried to the coast would have
been chiefly distributed over the plains of Lombardy. Their banks would
have risen as fast as their beds, the coast line would not have been
extended so far into the Adriatic, and, the current of the streams being
consequently shorter, the inclination of their channel and the rapidity
of their flow would not have been so greatly diminished. Had man spared
a reasonable proportion of the forests of the Alps, and not attempted to
control the natural drainage of the surface, the Po would resemble the
Nile in all its essential characteristics, and, in spite of the
difference of climate, perhaps be regarded as the friend and ally, not
the enemy and the invader, of the population which dwells upon its
banks.[371]
The Nile is larger than all the rivers of Lombardy together,[372] it
drains a basin twenty times as extensive, its banks have been occupied
by man probably twice as long. But its geographical character has not
been much changed in the whole period of recorded history, and, though
its outlets have somewhat fluctuated in number and position, its
historically known encroachments upon the sea are trifling compared with
those of the Po and the neighboring streams. The deposits of the Nile
are naturally greater in Upper than in Lower Egypt. They are found to
have raised the soil at Thebes about seven feet within the last
seventeen hundred years, and in the Delta the rise has been certainly
more than half as great.
We shall, therefore, not exceed the truth if we suppose the annually
inundated surface of Egypt to have been elevated, upon an average, ten
feet, within the last 5,000 years, or twice and a half the period during
which the history of the Po is known to us.[373]
We may estimate the present actually cultivated area of Egypt at about
5,500 square statute miles. As I have computed in a note on page 372,
that area is not more than half as extensive as under the dynasties of
the Pharaohs and the Ptolemies; for--though, in consequence of the
elevation of the river bed, the inundations now have a wider _natural_
spread--the industry of the ancient Egyptians conducted the Nile water
over a great extent of soil it does not now reach. We may, then, adopt a
mean between the two quantities, and we shall probably come near the
truth if we assume the convenient number of 7,920 square statute miles
as the average measure of the inundated land during the historical
period. Taking the deposit on this surface at ten feet, the river
sediment let fall on the soil of Egypt within the last fifty centuries
would amount to fifteen cubic miles.
Had the Nile been banked in, like the Po, all this deposit, except that
contained in the water diverted by canals or otherwise drawn from the
river for irrigation and other purposes, would have been carried out to
sea.[374] This would have been a considerable quantity; for the Nile
holds earth in suspension even at low water, a much larger proportion
during the flood, and irrigation must have been carried on during the
whole year. The precise amount which would have been thus distributed
over the soil is matter of conjecture, but three cubic miles is
certainly a liberal estimate. This would leave twelve cubic miles as the
quantity which embankments would have compelled the Nile to transport to
the Mediterranean over and above what it has actually deposited in that
sea. The Mediterranean is shoal for some miles out to sea along the
whole coast of the Delta, and the large bays or lagoons within the coast
line, which communicate both with the river and the sea, have little
depth of water. These lagoons the river deposits would have filled up,
and there would still have been surplus earth enough to extend the Delta
far into the Mediterranean.[375]
_Deposits of the Tuscan Rivers._
The Arno, and all the rivers rising on the western slopes and spurs of
the Apennines, carry down immense quantities of mud to the
Mediterranean. There can be no doubt that the volume of earth so
transported is very much greater than it would have been had the soil
about the headwaters of those rivers continued to be protected from wash
by forests; and there is as little question that the quantity borne out
to sea by the rivers of Western Italy is much increased by artificial
embankments, because they are thereby prevented from spreading over the
surface the sedimentary matter with which they are charged. The western
coast of Tuscany has advanced some miles seaward within a very few
centuries. The bed of the sea, for a long distance, has been raised, and
of course the relative elevation of the land above it lessened; harbors
have been filled up and destroyed; long lines of coast dunes have been
formed, and the diminished inclination of the beds of the rivers near
their outlets has caused their waters to overflow their banks and
convert them into pestilential marshes. The territorial extent of
Western Italy has thus been considerably increased, but the amount of
soil habitable and cultivable by man has been, in a still higher
proportion, diminished. The coast of ancient Etruria was filled with
great commercial towns, and their rural environs were occupied by a
large and prosperous population. But maritime Tuscany has long been one
of the most unhealthy districts in Christendom; the famous mart of
Populonia has not an inhabitant; the coast is almost absolutely
depopulated, and the malarious fevers have extended their ravages far
into the interior.
These results are certainly not to be ascribed wholly to human action.
They are, in a large proportion, due to geological causes over which man
has no control. The soil of much of Tuscany becomes pasty, almost fluid
even, as soon as it is moistened, and when thoroughly saturated with
water, it flows like a river. Such a soil as this would not be
completely protected by woods, and, indeed, it would now be difficult to
confine it long enough to allow it to cover itself with forest
vegetation. Nevertheless, it certainly was once chiefly wooded, and the
rivers which flow through it must then have been much less charged with
earthy matter than at present, and they must have carried into the sea a
smaller proportion of their sediment when they were free to deposit it
on their banks than since they have been confined by dikes.[376]
It is, in general, true, that the intervention of man has hitherto
seemed to insure the final exhaustion, ruin, and desolation of every
province of nature which he has reduced to his dominion. Attila was only
giving an energetic and picturesque expression to the tendencies of
human action, as personified in himself, when he said that "no grass
grew where his horse's hoofs had trod." The instances are few, where a
second civilization has flourished upon the ruins of an ancient culture,
and lands once rendered uninhabitable by human acts or neglect have
generally been forever abandoned as hopelessly irreclaimable. It is, as
I have before remarked, a question of vast importance, how far it is
practicable to restore the garden we have wasted, and it is a problem on
which experience throws little light, because few deliberate attempts
have yet been made at the work of physical regeneration, on a scale
large enough to warrant general conclusions in any one class of cases.
The valleys and shores of Tuscany form, however, a striking exception to
this remark. The success with which human guidance has made the
operations of nature herself available for the restoration of her
disturbed harmonies, in the Val di Chiana and the Tuscan Maremma, is
among the noblest, if not the most brilliant achievements of modern
engineering, and, regarded in all its bearings on the great question of
which I have just spoken, it is, as an example, of more importance to
the general interests of humanity than the proudest work of internal
improvement that mechanical means have yet constructed. The operations
in the Val di Chiana have consisted chiefly in so regulating the flow of
the surface waters into and through it, as to compel them to deposit
their sedimentary matter at the will of the engineers, and thereby to
raise grounds rendered insalubrious and unfit for agricultural use by
stagnating water; the improvements in the Maremma have embraced both
this method of elevating the level of the soil, and the prevention of
the mixture of salt water with fresh in the coast marshes and shallow
bays, which is a very active cause of the development of malarious
influences.[377]
_Improvements in the Val di Chiana._
For twenty miles or more after the remotest headwaters of the Arno have
united to form a considerable stream, this river flows southeastward to
the vicinity of Arezzo. It here sweeps round to the northwest, and
follows that course to near its junction with the Sieve, a few miles
above Florence, from which point its general direction is westward to
the sea. From the bend at Arezzo, a depression called the Val di Chiana
runs southeastward until it strikes into the valley of the Paglia, a
tributary of the Tiber, and thus connects the basin of the latter river
with that of the Arno. In the Middle Ages, and down to the eighteenth
century, the Val di Chiana was often overflowed and devastated by the
torrents which poured down from the highlands, transporting great
quantities of slime with their currents, stagnating upon its surface,
and gradually converting it into a marshy and unhealthy district, which
was at last very greatly reduced in population and productiveness. It
had, in fact, become so desolate that even the swallow had deserted
it.[378]
The bed of the Arno near Arezzo and that of the Paglia at the southern
extremity of the Val di Chiana did not differ much in level. The
general inclination of the valley was therefore small; it does not
appear to have ever been divided into opposite slopes by a true
watershed, and the position of the summit seems to have shifted
according to the varying amount and place of deposit of the sediment
brought down by the lateral streams which emptied into it. The length of
its principal channel of drainage, and even the direction of its flow at
any given point, were therefore fluctuating. Hence, much difference of
opinion was entertained at different times with regard to the normal
course of this stream, and, consequently, to the question whether it was
to be regarded as properly an affluent of the Tiber or of the Arno.
The bed of the latter river at the bend has been eroded to the depth of
thirty or forty feet, and that, apparently, at no very remote period. If
it were elevated to what was evidently its original height, the current
of the Arno would be so much above that of the Paglia as to allow of a
regular flow from its channel to the latter stream, through the Val di
Chiana, provided the bed of the valley had remained at the level which
excavations prove it to have had a few centuries ago, before it was
raised by the deposits I have mentioned. These facts, together with the
testimony of ancient geographers which scarcely admits of any other
explanation, are thought to prove that all the waters of the Upper Arno
were originally discharged through the Val di Chiana into the Tiber, and
that a part of them still continued to flow, at least occasionally, in
that direction down to the days of the Roman empire, and perhaps for
some time later. The depression of the bed of the Arno, and the raising
of that of the valley by the deposits of the lateral torrents and of the
Arno itself, finally cut off the branch of the river which had flowed to
the Tiber, and all its waters were turned into its present channel,
though the principal drainage of the Val di Chiana appears to have been
in a southeastwardly direction until within a comparatively recent
period.
In the sixteenth century, the elevation of the bed of the valley had
become so considerable, that in 1551, at a point about ten miles south
of the Arno, it was found to be not less than one hundred and thirty
feet above that river; then followed a level of ten miles, and then a
continuous descent to the Paglia. Along the level portion of the valley
was a boatable channel, and lakes, sometimes a mile or even two miles in
breadth, had formed at various points farther south. At this period, the
drainage of the summit level might easily have been determined in either
direction, and the opposite descents of the valley made to culminate at
the north or at the south end of the level. In the former case, the
watershed would have been ten miles south of the Arno; in the latter,
twenty miles, and the division would have been not very unequal.
Various schemes were suggested at this time for drawing off the stagnant
waters, as well as for the future regular drainage of the valley, and
small operations for those purposes were undertaken with partial
success; but it was feared that the discharge of the accumulated waters
into the Tiber would produce a dangerous inundation, while the diversion
of the drainage into the Arno would increase the violence of the floods
to which that river was very subject, and no decisive steps were taken.
In 1606, an engineer whose name has not been preserved proposed, as the
only possible method of improvement, the piercing of a tunnel through
the hills bounding the valley on the west to convey its waters to the
Ombrone, but the expense and other objections prevented the adoption of
this project.[379] The fears of the Roman Government for the security of
the valley of the Tiber had induced it to construct barriers across that
part of the channel which lay within its territory, and these
obstructions, though not specifically intended for that purpose,
naturally promoted the deposit of sediment and the elevation of the bed
of the valley in their neighborhood. The effect of this measure and of
the continued spontaneous action of the torrents was, that the northern
slope, which in 1551 had commenced at the distance of ten miles from the
Arno, was found in 1605 to begin, nearly thirty miles south of that
river, and in 1645 it had been removed about six miles farther in the
same direction.[380]
In the seventeenth century, the Tuscan and Papal Governments consulted
Galileo, Torricelli, Castelli, Cassini, Viviani, and other distinguished
philosophers and engineers, on the possibility of reclaiming the valley
by a regular artificial drainage. Most of these eminent physicists were
of opinion that the measure was impracticable, though not altogether for
the same reasons; but they seem to have agreed in thinking that the
opening of such channels, in either direction, as would give the current
a flow sufficiently rapid to drain the lands properly, would dangerously
augment the inundations of the river--whether the Tiber or the
Arno--into which the waters should be turned. The general improvement of
the valley was now for a long time abandoned, and the waters were
allowed to spread and stagnate until carried off by partial drainage,
infiltration, and evaporation. Torricelli had contended that the slope
of a large part of the valley was too small to allow it to be drained by
ordinary methods, and that no practicable depth and width of canal would
suffice for that purpose. It could be laid dry, he thought, only by
converting its surface into an inclined plane, and he suggested that
this might be accomplished by controlling the flow of the numerous
torrents which pour into it, so as to force them to deposit their
sediment at the pleasure of the engineer, and, consequently, to elevate
the level of the area over which it should be spread.[381] This plan
did not meet with immediate general acceptance, but it was soon adopted
for local purposes at some points in the southern part of the valley,
and it gradually grew in public favor and was extended in application
until its final triumph a hundred years later.
In spite of these encouraging successes, however, the fear of danger to
the valley of the Arno and the Tiber, and the difficulty of an agreement
between Tuscany and Rome--the boundary between which states crossed the
Val di Chiana not far from the halfway point between the two rivers--and
of reconciling other conflicting interests, prevented the resumption of
the projects for the general drainage of the valley until after the
middle of the eighteenth century. In the mean time the science of
hydraulics had become better understood, and the establishment of the
natural law according to which the velocity of a current of water, and
of course the proportional quantity discharged by it in a given time,
are increased by increasing its mass, had diminished if not dissipated
the fear of exposing the banks of the Arno to greater danger from
inundations by draining the Val di Chiana into it.
The suggestion of Torricelli was finally adopted as the basis of a
comprehensive system of improvement, and it was decided to continue and
extend the inversion of the original flow of the waters, and to turn
them into the Arno from a point as far to the south as should be found
practicable. The conduct of the works was committed to a succession of
able engineers who, for a long series of years, were under the general
direction of the celebrated philosopher and statesman Fossombroni, and
the success has fully justified the expectations of the most sanguine
advocates of the scheme. The plan of improvement embraced two branches:
the one, the removal of certain obstructions in the bed of the Arno,
and, consequently, the further depression of the channel of that river,
in certain places, with the view of increasing the rapidity of its
current; the other, the gradual filling up of the ponds and swamps, and
raising of the lower grounds of the Val di Chiana, by directing to
convenient points the flow of the streams which pour down into it, and
there confining their waters by temporary dams until the sediment was
deposited where it was needed. The economical result of these operations
has been, that in 1835 an area of more than four hundred and fifty
square miles of pond, marsh, and damp, sickly low grounds had been
converted into fertile, healthy and well-drained soil, and,
consequently, that so much territory has been added to the agricultural
domain of Tuscany.
But in our present view of the subject, the geographical revolution
which has been accomplished is still more interesting. The climatic
influence of the elevation and draining of the soil must have been
considerable, though I do not know that an increase or a diminution of
the mean temperature or precipitation in the valley has been established
by meteorological observation. There is, however, in the improvement of
the sanitary condition of the Val di Chiana, which was formerly
extremely unhealthy, satisfactory proof of a beneficial climatic change.
The fevers, which not only decimated the population of the low grounds
but infested the adjacent hills, have ceased their ravages, and are now
not more frequent than in other parts of Tuscany. The strictly
topographical effect of the operations in question, besides the
conversion of marsh into dry surface, has been the inversion of the
inclination of the valley for a distance of thirty-five miles, so that
this great plain which, within a comparatively short period, sloped and
drained its waters to the south, now inclines and sends its drainage to
the north. The reversal of the currents of the valley has added to the
Arno a new tributary equal to the largest of its former affluents, and a
most important circumstance connected with this latter fact is, that the
increase of the volume of its waters has accelerated their velocity in a
still greater proportion, and, instead of augmenting the danger from its
inundations, has almost wholly obviated that source of apprehension.
Between the beginning of the fifteenth century and the year 1761,
thirty-one destructive floods of the Arno are recorded; between 1761,
when the principal streams of the Val di Chiana were diverted into that
river, and 1835, not one.[382]
_Improvements in the Tuscan Maremme._
In the improvements of the Tuscan Maremma, more formidable difficulties
have been encountered. The territory to be reclaimed was more extensive;
the salubrious places of retreat for laborers and inspectors were more
remote; the courses of the rivers to be controlled were longer and their
natural inclination less rapid; some of them, rising in wooded regions,
transported comparatively little earthy matter,[383] and above all,
A like example is observed in the Anapus near Syracuse, which, below the
junction of its two branches, is narrower, though swifter than either of
them, and such cases are by no means unfrequent. The immediate effect of
the confluence of two rivers upon the current below depends upon local
circumstances, and especially upon the angle of incidence. If the two
nearly coincide in direction, so as to include a small angle, the joint
current will have a greater velocity than the slower confluent, perhaps
even than either of them. If the two rivers run in transverse, still
more if they flow in more or less opposite directions, the velocity of
the principal branch will be retarded both above and below the junction,
and at high water it may even set back the current of the affluent.
On the other hand, the diversion of a considerable branch from a river
retards its velocity below the point of separation, and here a deposit
of earth in its channel immediately begins, which has a tendency to turn
the whole stream into the new bed. "Theory and the authority of all
hydrographical writers combine to show that the channels of rivers
undergo an elevation of bed below a canal of diversion."--Letter of
FOSSOMBRONI, in SALVAGNOLI, _Raccolta di Documenti_, p. 32. See the
early authorities and discussions on the principle stated in the text,
in FRISI, _Del modo di regolare i Fiumi e i Torrenti_, libro iii, capit.
i. the coast, which is a recent deposit of the waters, is little
elevated above the sea, and admits into its lagoons and the mouths of
its rivers floods of salt water with every western wind, every rising
tide.[384]
The western coast of Tuscany is not supposed to have been an unhealthy
region before the conquest of Etruria by the Romans, but it certainly
became so within a few centuries after that event. This was a natural
consequence of the neglect or wanton destruction of the public
improvements, and especially the hydraulic works in which the Etruscans
were so skilful, and of the felling of the upland forests, to satisfy
the demand for wood at Rome for domestic, industrial, and military
purposes. After the downfall of the Roman empire, the incursions of the
barbarians, and then feudalism, foreign domination, intestine wars, and
temporal and spiritual tyrannies, aggravated still more cruelly the
moral and physical evils which Tuscany and the other Italian States were
doomed to suffer, and from which they have enjoyed but brief respites
during the whole period of modern history. The Maremma was already
proverbially unhealthy in the time of Dante, who refers to the fact in
several familiar passages, and the petty tyrants upon its borders often
sent criminals to places of confinement in its territory, as a slow but
certain mode of execution. Ignorance of the causes of the insalubrity,
and often the interference of private rights,[385] prevented the
adoption of measures to remove it, and the growing political and
commercial importance of the large towns in more healthful localities
absorbed the attention of Government, and deprived the Maremma of its
just share in the systems of physical improvement which were
successfully adopted in interior and Northern Italy.
Before any serious attempts were made to drain or fill up the marshes of
the Maremme, various other sanitary experiments were tried. It was
generally believed that the insalubrity of the province was the
consequence, not the cause, of its depopulation, and that, if it were
once densely inhabited, the ordinary operations of agriculture, and
especially the maintenance of numerous domestic fires, would restore it
to its ancient healthfulness.[386] In accordance with these views,
settlers were invited from various parts of Italy, from Greece, and,
after the accession of the Lorraine princes, from that country also, and
colonized in the Maremme. To strangers coming from soils and skies so
unlike those of the Tuscan marshes, the climate was more fatal than to
the inhabitants of the neighboring districts, whose constitutions had
become in some degree inured to the local influences, or who at least
knew better how to guard against them. The consequence very naturally
was that the experiment totally failed to produce the desired effects,
and was attended with a great sacrifice of life and a heavy loss to the
treasury of the state.
The territory known as the Tuscan Maremma, _ora maritima_, or
Maremme--for the plural form is most generally used--lies upon and near
the western coast of Tuscany, and comprises about 1,900 square miles
English, of which 500 square miles, or 320,000 acres, are plain and
marsh including 45,500 acres of water surface, and about 290,000 acres
are forest. One of the mountain peaks, that of Mount Amiata, rises to
the height of 6,280 feet. The mountains of the Maremma are healthy, the
lower hills much less so, as the malaria is felt at some points at the
height of 1,000 feet, and the plains, with the exception of a few
localities favorably situated on the seacoast, are in a high degree
pestilential. The fixed population is about 80,000, of whom one sixth
live on the plains in the winter and about one tenth in the summer. Nine
or ten thousand laborers come down from the mountains of the Maremma and
the neighboring provinces into the plain, during the latter season, to
cultivate and gather the crops.
Out of this small number of inhabitants and strangers, 35,619 were ill
enough to require medical treatment between the 1st of June, 1840, and
the 1st of June, 1841, and more than one half the cases were of
intermittent, malignant, gastric, or catarrhal fever. Very few
agricultural laborers escaped fever, though the disease did not always
manifest itself until they had returned to the mountains. In the
province of Grosseto, which embraces nearly the whole of the Maremma,
the annual mortality was 3.92 per cent. the average duration of life but
23.18 years, and 75 per cent. of the deaths were among persons engaged
in agriculture.
The filling up of the low grounds and the partial separation of the
waters of the sea and the land, which had been in progress since the
year 1827, now began to show very decided effects upon the sanitary
condition of the population. In the year ending June 1st, 1842, the
number of the sick was reduced by more than 2,000, and the cases of
fever by more than 4,000. The next year, the cases of fever fell to
10,500, and in that ending June 1st, 1844, to 9,200. The political
events of 1848 and the preceding and following years, occasioned the
suspension of the works of improvement in the Maremma, but they were
resumed after the revolution of 1859, and are now in successful
progress.
I have spoken, with some detail, of the improvements in the Val di
Chiana and the Tuscan Maremma, because of their great relative
importance, and because their history is well known; but like operations
have been executed in the territory of Pisa and upon the coast of the
duchy of Lucca. In the latter case, they were confined principally to
prevention of the intermixing of fresh water with that of the sea. In
1741, sluices or lock gates were constructed for this purpose, and the
following year, the fevers, which had been destructive to the coast
population for a long time previous, disappeared altogether. In 1768 and
1769, the works having fallen to decay, the fevers returned in a very
malignant form, but the rebuilding of the gates again restored the
healthfulness of the shore. Similar facts recurred in 1784 and 1785, and
again from 1804 to 1821. This long and repeated experience has at last
impressed upon the people the necessity of vigilant attention to the
sluices, which are now kept in constant repair. The health of the coast
is uninterrupted, and Viareggio, the capital town of the district, is
now much frequented for its sea baths and its general salubrity, at a
season when formerly it was justly shunned as the abode of disease and
death.[387]
It is now a hundred years since the commencement of the improvements in
the Val di Chiana, and those of the Maremma have been in more or less
continued operation for above a generation. They have, as we have seen,
produced important geographical changes in the surface of the earth and
in the flow of considerable rivers, and their effects have been not less
conspicuous in preventing other changes, of a deleterious character,
which would infallibly have taken place if they had not been arrested by
the improvements in question. It has been already stated that, in order
to prevent the overflow of the valley of the Tiber by freely draining
the Val di Chiana into it, the Papal authorities, long before the
commencement of the Tuscan works, constructed strong barriers near the
southern end of the valley, which detained the waters of the wet season
until they could be gradually drawn off into the Paglia. They
consequently deposited most of their sediment in the Val di Chiana and
carried down comparatively little earth to the Tiber. The lateral
streams contributing the largest quantities of sedimentary matter to the
Val di Chiana originally flowed into that valley near its northern end;
and the change of their channels and outlets in a southern direction, so
as to raise that part of the valley by their deposits and thereby
reverse its drainage, was one of the principal steps in the process of
improvement.
We have seen that the north end of the Val di Chiana near the Arno had
been raised by spontaneous deposit of sediment to such a height as to
interpose a sufficient obstacle to all flow in that direction. If, then,
the Roman dam had not been erected, or the works of the Tuscan
Government undertaken, the whole of the earth, which has been arrested
by those works and employed to raise the bed and reverse the declivity
of the valley, would have been carried down to the Tiber and thence into
the sea. The deposit thus created, would, of course, have contributed to
increase the advance of the shore at the mouth of that river, which has
long been going on at the rate of three mètres and nine tenths (twelve
feet and nine inches) per annum.[388] It is evident that a quantity of
earth, sufficient to effect the immense changes I have described in a
wide valley more than thirty miles long, if deposited at the outlet of
the Tiber, would have very considerably modified the outline of the
coast, and have exerted no unimportant influence on the flow of that
river, by raising its point of discharge and lengthening its channel.
The sediment washed into the marshes of the Maremme is not less than
12,000,000 cubic yards per annum. The escape of this quantity into the
sea, which is now almost wholly prevented, would be sufficient to
advance the coast line fourteen yards per year, for a distance of forty
miles, computing the mean depth of the sea near the shore at twelve
yards. It is true that in this case, as well as in that of other rivers,
the sedimentary matter would not be distributed equally along the shore,
and much of it would be carried out into deep water, or perhaps
transported by the currents to distant coasts. The immediate effects of
the deposit, therefore, would not be so palpable as they appear in this
numerical form, but they would be equally certain, and would infallibly
manifest themselves, first, perhaps, at some remote point, and afterward
at or near the outlets of the rivers which produced them.
_Obstruction of River Mouths._
The mouths of a large proportion of the streams known to ancient
internal navigation are already blocked up by sandbars or fluviatile
deposits, and the maritime approaches to river harbors frequented by the
ships of Phenicia and Carthage and Greece and Rome are shoaled to a
considerable distance out to sea. The inclination of almost every known
river bed has been considerably reduced within the historical period,
and nothing but great volume of water, or exceptional rapidity of flow,
now enables a few large streams like the Amazon, the La Plata, the
Ganges, and, in a less degree, the Mississippi, to carry their own
deposits far enough out into deep water to prevent the formation of
serious obstructions to navigation. But the degradation of their banks,
and the transportation of earthy matter to the sea by their currents,
are gradually filling up the estuaries even of these mighty floods, and
unless the threatened evil shall be averted by the action of geological
forces, or by artificial contrivances more efficient than dredging
machines, the destruction of every harbor in the world which receives a
considerable river must inevitably take place at no very distant date.
This result would, perhaps, have followed in some incalculably distant
future, if man had not come to inhabit the earth as soon as the natural
forces which had formed its surface had arrived at such an approximate
equilibrium that his existence on the globe was possible; but the
general effect of his industrial operations has been to accelerate it
immensely. Rivers, in countries planted by nature with forests and never
inhabited by man, employ the little earth and gravel they transport
chiefly to raise their own beds and to form plains in their basins.[389]
In their upper course, where the current is swiftest, they are most
heavily charged with coarse rolled or suspended matter, and this, in
floods, they deposit on their shores in the mountain valleys where they
rise; in their middle course, a lighter earth is spread over the bottom
of their widening basins, and forms plains of moderate extent; the fine
silt which floats farther is deposited over a still broader area, or, if
carried out to sea, is, in great part quickly swept far off by marine
currents and dropped at last in deep water. Man's "improvement" of the
soil increases the erosion from its surface; his arrangements for
confining the lateral spread of the water in floods compel the rivers to
transport to their mouths the earth derived from that erosion even in
their upper course; and, consequently, the sediment they deposit at
their outlets is not only much larger in quantity, but composed of
heavier materials, which sink more readily to the bottom of the sea and
are less easily removed by marine currents.
The tidal movement of the ocean, deep sea currents, and the agitation of
inland waters by the wind, lift up the sands strewn over the bottom by
diluvial streams or sent down by mountain torrents, and throw them up on
dry land, or deposit them in sheltered bays and nooks of the coast--for
the flowing is stronger than the ebbing tide, the affluent than the
refluent wave. This cause of injury to harbors it is not in man's power
to resist by any means at present available; but, as we have seen,
something can be done to prevent the degradation of high grounds, and to
diminish the quantity of earth which is annually abstracted from the
mountains, from table lands, and from river banks, to raise the bottom
of the sea.
This latter cause of harbor obstruction, though an active agent, is,
nevertheless, in many cases, the less powerful of the two. The earth
suspended in the lower course of fluviatile currents is lighter than sea
sand, river water lighter than sea water, and hence, if a land stream
enters the sea with a considerable volume, its water flows over that of
the sea, and bears its slime with it until it lets it fall far from
shore, or, as is more frequently the case, mingles with some marine
current and transports its sediment to a remote point of deposit. The
earth borne out of the mouths of the Nile is in part carried over the
waves which throw up sea sand on the beach, and deposited in deep water,
in part drifted by the current, which sweeps east and north along the
coasts of Egypt and Syria, until it finds a resting place in the
northeastern angle of the Mediterranean.[390] Thus the earth loosened by
the rude Abyssinian ploughshare, and washed down by the rain from the
hills of Ethiopia which man has stripped of their protecting forests,
contributes to raise the plains of Egypt, to shoal the maritime channels
which lead to the city built by Alexander near the mouth of the Nile,
and to fill up the harbors made famous by Phenician commerce.
_Subterranean Waters._
I have frequently alluded to a branch of geography, the importance of
which is but recently adequately recognized--the subterranean waters of
the earth considered as stationary reservoirs, as flowing currents, and
as filtrating fluids. The earth drinks in moisture by direct absorption
from the atmosphere, by the deposition of dew, by rain and snow, by
percolation from rivers and other superficial bodies of water, and
sometimes by currents flowing into caves or smaller visible
apertures.[391] Some of this humidity is exhaled again by the soil,
some is taken up by organic growths and by inorganic compounds, some
poured out upon the surface by springs and either immediately evaporated
or carried down to larger streams and to the sea, some flows by
subterranean courses into the bed of fresh-water rivers[392] or of the
ocean, and some remains, though even here not in forever motionless
repose, to fill deep cavities and underground channels.[393] In every
case the aqueous vapors of the air are the ultimate source of supply,
and all these hidden stores are again returned to the atmosphere by
evaporation.
The proportion of the water of precipitation taken up by direct
evaporation from the surface of the ground seems to have been generally
exaggerated, sufficient allowance not being made for moisture carried
downward, or in a lateral direction, by infiltration or by crevices in
the superior rocky or earthy strata. According to Wittwer, Mariotte
found that but one sixth of the precipitation in the basin of the Seine
was delivered into the sea by that river, "so that five sixths remained
for evaporation and consumption by the organic world."[394]
Lieutenant Maury--whose scientific reputation, though fallen, has not
quite sunk to the level of his patriotism--estimates the annual amount
of precipitation in the valley of the Mississippi at 620 cubic miles,
the discharge of that river into the sea at 107 cubic miles, and
concludes that "this would leave 513 cubic miles of water to be
evaporated from this river basin annually."[395] In these and other like
computations, the water carried down into the earth by capillary and
larger conduits is wholly lost sight of, and no thought is bestowed upon
the supply for springs, for common and artesian wells, and for
underground rivers, like those in the great caves of Kentucky, which may
gush up in fresh-water currents at the bottom of the Caribbean Sea, or
rise to the light of day in the far-off peninsula of Florida.
The progress of the emphatically modern science of geology has corrected
these erroneous views, because the observations on which it depends have
demonstrated not only the existence, but the movement, of water in
nearly all geological formations, have collected evidence of the
presence of large reservoirs at greater or less depths beneath surfaces
of almost every character, and have investigated the rationale of the
attendant phenomena. The distribution of these waters has been minutely
studied with reference to a great number of localities, and though the
actual mode of their vertical and horizontal transmission is still
involved in much doubt, the laws which determine their aggregation are
so well understood, that, when the geology of a given district is known,
it is not difficult to determine at what depth water will be reached by
the borer, and to what height it will rise.
The same principles have been successfully applied to the discovery of
small subterranean collections or currents of water, and some persons
have acquired, by a moderate knowledge of the superficial structure of
the earth combined with long practice, a skill in the selection of
favorable places for digging wells which seems to common observers
little less than miraculous. The Abbé Paramelle--a French ecclesiastic
who devoted himself for some years to this subject and was extensively
employed as a well-finder--states, in his work on Fountains, that in the
course of thirty-four years he had pointed out more than ten thousand
subterranean springs, and though his geological speculations were often
erroneous, the highest scientific authorities in Europe have testified
to the great practical value of his methods, and the almost infallible
certainty of his predictions.[396]
Babinet quotes a French proverb, "Summer rain wets nothing," and
explains it as meaning that the water of such rains is "almost totally
taken up by evaporation." "The rains of summer," he adds, "however
abundant they may be, do not penetrate the soil to a greater depth than
15 or 20 centimètres. In summer the evaporating power of the heat is
five or six times as great as in winter, and this power is exerted by an
atmosphere capable of containing five times as much vapor as in winter."
"A stratum of snow which prevents evaporation [from the soil] causes
almost all the water that composes it to filter down into the earth, and
form a reserve for springs, wells, and rivers which could not be
supplied by any amount of summer rain." "This latter--useful, indeed
like dew, to vegetation--does not penetrate the soil and accumulate a
store to feed springs and to be brought up by them to the open
air."[397] This conclusion, however applicable it may be to the climate
and soil of France, is too broadly stated to be accepted as a general
truth, and in countries where the precipitation is small in the winter
months, familiar observation shows that the quantity of water yielded by
deep wells and natural springs depends not less on the rains of summer
than on those of the rest of the year, and, consequently, that much of
the precipitation of that season must find its way to strata too deep to
lose water by evaporation.
The supply of subterranean reservoirs and currents, as well as of
springs, is undoubtedly derived chiefly from infiltration, and hence it
must be affected by all changes of the natural surface that accelerate
or retard the drainage of the soil, or that either promote or obstruct
evaporation from it. It has sufficiently appeared from what has gone
before, that the spontaneous drainage of cleared ground is more rapid
than that of the forest, and consequently, that the felling of the
woods, as well as the draining of swamps, deprives the subterranean
waters of accessions which would otherwise be conveyed to them by
infiltration. The same effect is produced by artificial contrivances for
drying the soil either by open ditches or by underground pipes or
channels, and in proportion as the sphere of these operations is
extended, the effect of them cannot fail to make itself more and more
sensibly felt in the diminished supply of water furnished by wells and
running springs.[398]
It is undoubtedly true that loose soils, stripped of vegetation and
broken up by the plough or other processes of cultivation, may, until
again carpeted by grasses or other plants, absorb more rain and snow
water than when they were covered by a natural growth; but it is also
true that the evaporation from such soils is augmented in a still
greater proportion. Rain scarcely penetrates beneath the sod of grass
ground, but runs off over the surface; and after the heaviest showers a
ploughed field will often be dried by evaporation before the water can
be carried off by infiltration, while the soil of a neighboring grove
will remain half saturated for weeks together. Sandy soils frequently
rest on a tenacious subsoil, at a moderate depth, as is usually seen in
the pine plains of the United States, where pools of rain water collect
in slight depressions on the surface of earth, the upper stratum of
which is as porous as a sponge. In the open grounds such pools are very
soon dried up by the sun and wind; in the woods they remain unevaporated
long enough for the water to diffuse itself laterally until it finds, in
the subsoil, crevices through which it may escape, or slopes which it
may follow to their outcrop or descend along them to lower strata.
The readiness with which water not obstructed by impermeable strata
diffuses itself through the earth in all directions--and, consequently,
the importance of keeping up the supply of subterranean reservoirs--find
a familiar illustration in the effect of paving the ground about the
stems of vines and trees. The surface earth around the trunk of a tree
may be made perfectly impervious to water, by flag stones and cement,
for a distance greater than the spread of the roots; and yet the tree
will not suffer for want of moisture, except in droughts severe enough
sensibly to affect the supply in deep wells and springs. Both forest and
fruit trees grow well in cities where the streets and courts are closely
paved, and where even the lateral access of water to the roots is more
or less obstructed by deep cellars and foundation walls. The deep-lying
veins and sheets of water, supplied by infiltration from above, send up
moisture by capillary attraction, and the pavement prevents the soil
beneath it from losing its humidity by evaporation. Hence, city-grown
trees find moisture enough for their roots, and though plagued with
smoke and dust, often retain their freshness while those planted in the
open fields, where sun and wind dry up the soil faster than the
subterranean fountains can water it, are withering from drought. Without
the help of artificial conduit or of water carrier, the Thames and the
Seine refresh the ornamental trees that shade the thoroughfares of
London and of Paris, and beneath the hot and reeking mould of Egypt, the
Nile sends currents to the extremest border of its valley.[399]
_Artesian Wells._
The existence of artesian wells depends upon that of subterranean
reservoirs and rivers, and the supply yielded by borings is regulated by
the abundance of such sources. The waters of the earth are, in many
cases, derived from superficial currents which are seen to pour into
chasms opened, as it were, expressly for their reception; and in others
where no apertures in the crust of the earth have been detected, their
existence is proved by the fact that artesian wells sometimes bring up
from great depths seeds, leaves, and even living fish, which must have
been carried down through channels large enough to admit a considerable
stream. But in general, the sheets and currents of water reached by deep
boring appear to be primarily due to infiltration from highlands where
the water is first collected in superficial or subterranean reservoirs.
By means of channels conforming to the dip of the strata, these
reservoirs communicate with the lower basins, and exert upon them a
fluid pressure sufficient to raise a column to the surface, whenever an
orifice is opened.[400] The water delivered by an artesian well is,
therefore, often derived from distant sources, and may be wholly
unaffected by geographical or meteorological changes in its immediate
neighborhood, while the same changes may quite dry up common wells and
springs which are fed only by the local infiltration of their own narrow
basins.
In most cases, artesian wells have been bored for purely economical or
industrial purposes, such as to obtain good water for domestic use or
for driving light machinery, to reach saline or other mineral springs,
and recently, in America, to open fountains of petroleum or rock oil.
The geographical and geological effects of such abstraction of fluids
from the bowels of the earth are too remote and uncertain to be here
noticed;[401] but artesian wells have lately been employed in Algeria
for a purpose which has even now a substantial, and may hereafter
acquire a very great geographical importance. It was observed by many
earlier as well as recent travellers in the East, among whom Shaw
deserves special mention, that the Libyan desert, bordering upon the
cultivated shores of the Mediterranean, appeared in many places to rest
upon a subterranean lake at an accessible distance below the surface.
The Moors are vaguely said to have _bored_ artesian wells down to this
reservoir, to obtain water for domestic use and irrigation, but I do
not find such wells described by any trustworthy traveller, and the
universal astonishment and incredulity with which the native tribes
viewed the operations of the French engineers sent into the desert for
that purpose, are a sufficient proof that this mode of reaching the
subterranean waters was new to them. They were, however, aware of the
existence of water below the sands, and were dexterous in digging
wells--square shafts lined with a framework of palm-tree stems--to the
level of the sheet. The wells so constructed, though not technically
artesian wells, answer the same purpose; for the water rises to the
surface and flows over it as from a spring.[402]
These wells, however, are too few and too scanty in supply to serve any
other purposes than the domestic wells of other countries, and it is but
recently that the transformation of desert into cultivable land by this
means has been seriously attempted. The French Government has bored a
large number of artesian wells in the Algerian desert within a few
years, and the native sheikhs are beginning to avail themselves of the
process. Every well becomes the nucleus of a settlement proportioned to
the supply of water, and before the end of the year 1860, several nomade
tribes had abandoned their wandering life, established themselves around
the wells, and planted more than 30,000 palm trees, besides other
perennial vegetables.[403] The water is found at a small depth,
generally from 100 to 200 feet, and though containing too large a
proportion of mineral matter to be acceptable to a European palate, it
answers well for irrigation, and does not prove unwholesome to the
natives.
The most obvious use of artesian wells in the desert at present is that
of creating stations for the establishment of military posts and halting
places for the desert traveller; but if the supply of water shall prove
adequate for the indefinite extension of the system, it is probably
destined to produce a greater geographical transformation than has ever
been effected by any scheme of human improvement. The most striking
contrast of landscape scenery that nature brings near together in time
or place, is that between the greenery of the tropics, or of a northern
summer, and the snowy pall of leafless winter. Next to this in startling
novelty of effect, we must rank the sudden transition from the shady and
verdant oasis of the desert to the bare and burning party-colored ocean
of sand and rock which surrounds it.[404] The most sanguine believer in
indefinite human progress hardly expects that man's cunning will
accomplish the universal fufilment of the prophecy, "the desert shall
blossom as the rose," in its literal sense; but sober geographers have
thought the future conversion of the sand plains of Northern Africa into
fruitful gardens, by means of artesian wells, not an improbable
expectation. They have gone farther, and argued that, if the soil were
covered with fields and forests, vegetation would call down moisture
from the Libyan sky, and that the showers which are now wasted on the
sea, or so often deluge Southern Europe with destructive inundation,
would in part be condensed over the arid wastes of Africa, and thus,
without further aid from man, bestow abundance on regions which nature
seems to have condemned to perpetual desolation.
An equally bold speculation, founded on the well-known fact, that the
temperature of the earth and of its internal waters increases as we
descend beneath the surface, has suggested that artesian wells might
supply heat for industrial and domestic purposes, for hot-house
cultivation, and even for the local amelioration of climate. The success
with which Count Lardarello has employed natural hot springs for the
evaporation of water charged with boracic acid, and other fortunate
applications of the heat of thermal sources, lend some countenance to
the latter project; but both must, for the present, be ranked among the
vague possibilities of science, not regarded as probable future triumphs
of man over nature.
_Artificial Springs._
A more plausible and inviting scheme is that of the creation of
perennial springs by husbanding rain and snow water, storing it up in
artificial reservoirs of earth, and filtering it through purifying
strata, in analogy with the operations of nature. The sagacious
Palissy--starting from the theory that all springs are primarily derived
from precipitation, and reasoning justly on the accumulation and
movement of water in the earth--proposed to reduce theory to practice,
and to imitate the natural processes by which rain is absorbed by the
earth and given out again in running fountains. "When I had long and
diligently considered the cause of the springing of natural fountains
and the places where they be wont to issue," says he, "I did plainly
perceive, at last, that they do proceed and are engendered of nought but
the rains. And it is this, look you, which hath moved me to enterprise
the gathering together of rain water after the manner of nature, and the
most closely according to her fashion that I am able; and I am well
assured that by following the formulary of the Supreme Contriver of
fountains, I can make springs, the water whereof shall be as good and
pure and clear as of such which be natural."[405] Palissy discusses the
subject of the origin of springs at length and with much ability,
dwelling specially on infiltration, and, among other things, thus
explains the frequency of springs in mountainous regions: "Having well
considered the which, thou mayest plainly see the reason why there be
more springs and rivulets proceeding from the mountains than from the
rest of the earth; which is for no other cause but that the rocks and
mountains do retain the water of the rains like vessels of brass. And
the said waters falling upon the said mountains descend continually
through the earth, and through crevices, and stop not till they find
some place that is bottomed with stone or close and thick rocks; and
they rest upon such bottom until they find some channel or other manner
of issue, and then they flow out in springs or brooks or rivers,
according to the greatness of the reservoirs and of the outlets
thereof."[406]
After a full exposition of his theory, Palissy proceeds to describe his
method of creating springs, which is substantially the same as that
lately proposed by Babinet in the following terms: "Choose a piece of
ground containing four or five acres, with a sandy soil, and with a
gentle slope to determine the flow of the water. Along its upper line,
dig a trench five or six feet deep and six feet wide. Level the bottom
of the trench, and make it impermeable by paving, by macadamizing, by
bitumen, or, more simply and cheaply, by a layer of clay. By the side of
this trench dig another, and throw the earth from it into the first, and
so on until you have rendered the subsoil of the whole parcel
impermeable to rain water. Build a wall along the lower line with an
aperture in the middle for the water, and plant fruit or other low trees
upon the whole, to shade the ground and check the currents of air which
promote evaporation. This will infallibly give you a good spring which
will flow without intermission and supply the wants of a whole hamlet or
a large chateau."[407] Babinet states that the whole amount of
precipitation on a reservoir of the proposed area, in the climate of
Paris, would be about 13,000 cubic yards, not above one half of which,
he thinks, would be lost, and, of course, the other half would remain
available to supply the spring. I much doubt whether this expectation
would be realized in practice, in its whole extent; for if Babinet is
right in supposing that the summer rain is wholly evaporated, the winter
rains, being much less in quantity, would hardly suffice to keep the
earth saturated and give off so large a surplus.
The method of Palissy, though, as I have said, similar in principle to
that of Babinet, would be cheaper of execution, and, at the same time,
more efficient. He proposes the construction of relatively small
filtering receptacles, into which he would conduct the rain falling upon
a large area of rocky hillside, or other sloping ground not readily
absorbing water. This process would, in all probability, be a very
successful, as well as an inexpensive, mode of economizing atmospheric
precipitation, and compelling the rain and snow to form perennial
fountains at will.
_Economizing Precipitation._
The methods suggested by Palissy and by Babinet are of limited
application, and designed only to supply a sufficient quantity of water
for the domestic use of small villages or large private establishments.
Dumas has proposed a much more extensive system for collecting and
retaining the whole precipitation in considerable valleys, and storing
it in reservoirs, whence it is to be drawn for household and mechanical
purposes, for irrigation, and, in short, for all the uses to which the
water of natural springs and brooks is applicable. His plan consists in
draining both surface and subsoil, by means of conduits differing in
construction according to local circumstances, but in the main not
unlike those employed in improved agriculture, collecting the water in a
central channel, securing its proper filterage, checking its too rapid
flow by barriers at convenient points, and finally receiving the whole
in spacious covered reservoirs, from which it may be discharged in a
constant flow or at intervals as convenience may dictate.[408]
There is no reasonable doubt that a very wide employment of these
various contrivances for economizing and supplying water is practicable,
and the expediency of resorting to them is almost purely an economical
question. There appears to be no serious reason to apprehend collateral
evils from them, and in fact all of them, except artesian wells, are
simply indirect methods of returning to the original arrangements of
nature, or, in other words, of restoring the fluid circulation of the
globe; for when the earth was covered with the forest, perennial springs
gushed from the foot of every hill, brooks flowed down the bed of every
valley. The partial recovery of the fountains and rivulets which once
abundantly watered the face of the agricultural world seems practicable
by such means, even without any general replanting of the forests; and
the cost of one year's warfare, if judiciously expended in a combination
of both methods of improvement, would secure, to almost every country
that man has exhausted, an amelioration of climate, a renovated
fertility of soil, and a general physical improvement, which might
almost be characterized as a new creation.
CHAPTER V.
THE SANDS.
ORIGIN OF SAND--SAND NOW CARRIED DOWN TO THE SEA--THE SANDS OF EGYPT AND
THE ADJACENT DESERT----THE SUEZ CANAL----THE SANDS OF EGYPT--COAST DUNES
AND SAND PLAINS--SAND BANKS--DUNES ON COAST OF AMERICA--DUNES OF WESTERN
EUROPE--FORMATION OF DUNES--CHARACTER OF DUNE SAND--INTERIOR STRUCTURE
OF DUNES--FORM OF DUNES--GEOLOGICAL IMPORTANCE OF DUNES--INLAND DUNES--
AGE, CHARACTER, AND PERMANENCE OF DUNES--USE OF DUNES AS BARRIER AGAINST
THE SEA--ENCROACHMENTS OF THE SEA--THE LIIMFJORD--ENCROACHMENTS OF THE
SEA--DRIFTING OF DUNE SANDS--DUNES OF GASCONY--DUNES OF DENMARK--DUNES
OF PRUSSIA--ARTIFICIAL FORMATION OF DUNES--TREES SUITABLE FOR DUNE
PLANTATIONS--EXTENT OF DUNES IN EUROPE--DUNE VINEYARDS OF CAPE BRETON--
REMOVAL OF DUNES--INLAND SAND PLAINS--THE LANDES OF GASCONY--THE BELGIAN
CAMPINE--SANDS AND STEPPES OF EASTERN EUROPE--ADVANTAGES OF RECLAIMING
DUNES--GOVERNMENT WORKS OF IMPROVEMENT.
_Origin of Sand._
Sand, which is found in beds or strata at the bottom of the sea or in
the channels of rivers, as well as in extensive deposits upon or beneath
the surface of the dry land, appears to consist essentially of the
detritus of rocks. It is not always by any means clear through what
agency the solid rock has been reduced to a granular condition; for
there are beds of quartzose sand, where the sharp, angular shape of the
particles renders it highly improbable that they have been formed by
gradual abrasion and attrition, and where the supposition of a crushing
mechanical force seems equally inadmissible. In common sand, the quartz
grains are the most numerous; but this is not a proof that the rocks
from which these particles were derived were wholly, or even chiefly,
quartzose in character; for, in many composite rocks, as, for example,
in the granitic group, the mica, felspar, and hornblende are more easily
decomposed by chemical action, or disintegrated, comminuted, and reduced
to an impalpable state by mechanical force, than the quartz. In the
destruction of such rocks, therefore, the quartz would survive the other
ingredients, and remain unmixed, when they had been decomposed and had
entered into new chemical combinations, or been ground to slime and
washed away by water currents.
The greater or less specific gravity of the different constituents of
rock doubtless aids in separating them into distinct masses when once
disintegrated, though there are veined and stratified beds of sand where
the difference between the upper and lower layers, in this respect, is
too slight to be supposed capable of effecting a complete
separation.[409] In cases where rock has been reduced to sandy fragments
by heat, or by obscure chemical and other molecular forces, the sandbeds
may remain undisturbed, and represent, in the series of geological
strata, the solid formations from which they were derived. The large
masses of sand not found in place have been transported and accumulated
by water or by wind, the former being generally considered the most
important of these agencies; for the extensive deposits of the Sahara,
of the deserts of Persia, and of that of Gobi, are commonly supposed to
have been swept together or distributed by marine currents, and to have
been elevated above the ocean by the same means as other upheaved
strata.
Meteoric and mechanical influences are still active in the reduction of
rocks to a fragmentary state; but the quantity of sand now transported
to the sea seems to be comparatively inconsiderable, because--not to
speak of the absence of diluvial action--the number of torrents emptying
directly into the sea is much less than it was at earlier periods. The
formation of alluvial plains in maritime bays, by the sedimentary matter
brought down from the mountains, has lengthened the flow of such streams
and converted them very generally into rivers, or rather affluents of
rivers much younger than themselves. The filling up of the estuaries has
so reduced the slope of all large and many small rivers, and,
consequently, so checked the current of what the Germans call their
_Unterlauf_, or lower course, that they are much less able to transport
heavy material than at earlier epochs. The slime deposited by rivers at
their junction with the sea, is usually found to be composed of material
too finely ground and too light to be denominated sand, and it can be
abundantly shown that the sandbanks at the outlet of large streams are
of tidal, not of fluviatile origin, or, in lakes and tideless seas, a
result of the concurrent action of waves and of wind.
Large deposits of sand, therefore, must in general be considered as of
ancient, not of recent formation, and many eminent geologists ascribe
them to diluvial action. Staring has discussed this question very fully,
with special reference to the sands of the North Sea, the Zuiderzee, and
the bays and channels of the Dutch coast.[410] His general conclusion
is, that the rivers of the Netherlands "move sand only by a very slow
displacement of sandbanks, and do not carry it with them as a suspended
or floating material." The sands of the German Ocean he holds to be a
product of the "great North German drift," deposited where they now lie
before the commencement of the present geological period, and he
maintains similar opinions with regard to the sands thrown up by the
Mediterranean at the mouths of the Nile and on the Barbary coast.[411]
_Sand now carried to the Sea._
There are, however, cases where mountain streams still bear to the sea
perhaps relatively small, but certainly absolutely large, amounts of
disintegrated rock.[412] The quantity of sand and gravel carried into
the Mediterranean by the torrents of the Maritime Alps, the Ligurian
Apennines, the islands of Corsica, Sardinia, and Sicily, and the
mountains of Calabria, is apparently great. In mere mass, it is
possible, if not probable, that as much rocky material, more or less
comminuted, is contributed to the basin of the Mediterranean by Europe,
even excluding the shores of the Adriatic and the Euxine, as is washed
up from it upon the coasts of Africa and Syria. A great part of this
material is thrown out again by the waves on the European shores of that
sea. The harbors of Luni, Albenga, San Remo, and Savona west of Genoa,
and of Porto Fino on the other side, are filling up, and the coast near
Carrara and Massa is said to have advanced upon the sea to a distance
of 475 feet in thirty-three years.[413] Besides this, we have no
evidence of the existence of deep-water currents in the Mediterranean,
extensive enough and strong enough to transport quartzose sand across
the sea. It may be added that much of the rock from which the torrent
sands of Southern Europe are derived contains little quartz, and hence
the general character of these sands is such that they must be
decomposed or ground down to an impalpable slime, long before they could
be swept over to the African shore.
The torrents of Europe, then, do not at present furnish the material
which composes the beach sands of Northern Africa, and it is equally
certain that those sands are not brought down by the rivers of the
latter continent. They belong to a remote geological period, and have
been accumulated by causes which we cannot at present assign. The wind
does not stir water to great depths with sufficient force to disturb the
bottom,[414] and the sand thrown upon the coast in question must be
derived from a narrow belt of sea. It must hence, in time, become
exhausted, and the formation of new sandbanks and dunes upon the
southern shores of the Mediterranean will cease at last for want of
material.[415]
But even in the cases where the accumulations of sand in extensive
deserts appear to be of marine formation, or rather aggregation, and to
have been brought to their present position by upheaval, they are not
wholly composed of material collected or distributed by the currents of
the sea; for, in all such regions, they continue to receive some small
contributions from the disintegration of the rocks which underlie, or
crop out through, the superficial deposits. In some instances, too, as
in Northern Africa, additions are constantly made to the mass by the
prevalence of sea winds, which transport, or, to speak more precisely,
roll the finer beach sand to considerable distances into the interior.
But this is a very slow process, and the exaggerations of travellers
have diffused a vast deal of popular error on the subject.
_Sands of Egypt._
In the narrow valley of the Nile--which, above its bifurcation near
Cairo, is, throughout Egypt and Nubia, generally bounded by precipitous
cliffs--wherever a ravine or other considerable depression occurs in the
wall of rock, one sees what seems a stream of desert sand pouring down,
and common observers have hence concluded that the whole valley is in
danger of being buried under a stratum of infertile soil. The ancient
Egyptians apprehended this, and erected walls, often of unburnt brick,
across the outlet of gorges and lateral valleys, to check the flow of
the sand streams. In later ages, these walls have mostly fallen into
decay, and no preventive measures against such encroachments are now
resorted to. But the extent of the mischief to the soil of Egypt, and
the future danger from this source, have been much overrated. The sand
on the borders of the Nile is neither elevated so high by the wind, nor
transported by that agency in so great masses, as is popularly supposed;
and of that which is actually lifted or rolled and finally deposited by
air currents, a considerable proportion is either calcareous, and,
therefore, readily decomposable, or in the state of a very fine dust,
and so, in neither case, injurious to the soil. There are, indeed, both
in Africa and in Arabia, considerable tracts of fine silicious sand,
which may be carried far by high winds, but these are exceptional cases,
and in general the progress of the desert sand is by a rolling motion
along the surface.[416] So little is it lifted, and so inconsiderable
is the quantity yet remaining on the borders of Egypt, that a wall four
or five feet high suffices for centuries to check its encroachments.
This is obvious to the eye of every observer who prefers the true to the
marvellous; but the old-world fable of the overwhelming of caravans by
the fearful simoom--which, even the Arabs no longer repeat, if indeed
they are the authors of it--is so thoroughly rooted in the imagination
of Christendom that most desert travellers, of the tourist class, think
they shall disappoint the readers of their journals if they do not
recount the particulars of their escape from being buried alive by a
sand storm, and the popular demand for a "sensation" must be gratified
accordingly.[417]
Another circumstance is necessary to be considered in estimating the
danger to which the arable lands of Egypt are exposed. The prevailing
wind in the valley of the Nile and its borders is from the north, and it
may be said without exaggeration that the north wind blows for three
quarters of the year.[418] The effect of winds blowing up the valley is
to drive the sands of the desert plateau which border it, in a direction
parallel with the axis of the valley, not transversely to it; and if it
ran in a straight line, the north wind would carry no desert sand into
it. There are, however, both curves and angles in its course, and hence,
wherever its direction deviates from that of the wind, it might receive
sand drifts from the desert plain through which it runs. But, in the
course of ages, the winds have, in a great measure, bared the projecting
points of their ancient deposits, and no great accumulations remain in
situations from which either a north or a south wind would carry them
into the valley.[419]
_The Suez Canal._
These considerations apply, with equal force, to the supposed danger of
the obstruction of the Suez Canal by the drifting of the desert sands.
The winds across the isthmus are almost uniformly from the north, and
they swept it clean of flying sands long ages since. The traces of the
ancient canal between the Red Sea and the Nile are easily followed for a
considerable distance from Suez. Had the drifts upon the isthmus been as
formidable as some have feared and others have hoped, those traces would
have been obliterated, and Lake Timsah and the Bitter Lakes filled up,
many centuries ago. The few particles driven by the rare east and west
winds toward the line of the canal, would easily be arrested by
plantations or other simple methods, or removed by dredging. The real
dangers and difficulties of this magnificent enterprise--and they are
great--consist in the nature of the soil to be removed in order to form
the line, and especially in the constantly increasing accumulation of
sea sand at the southern terminus by the tides of the Red Sea, and at
the northern, by the action of the winds. Both seas are shallow for
miles from the shore, and the excavation and maintenance of deep
channels, and of capacious harbors with easy and secure entrances, in
such localities, is doubtless one of the hardest problems offered to
modern engineers for practical solution.
_Sands of Egypt._
The sand let fall in Egypt by the north wind is derived, not from the
desert, but from a very different source--the sea. Considerable
quantities of sand are thrown up by the Mediterranean, at and between
the mouths of the Nile, and indeed along almost the whole southern coast
of that sea, and drifted into the interior to distances varying
according to the force of the wind and the abundance and quality of the
material. The sand so transported contributes to the gradual elevation
of the Delta, and of the banks and bed of the river itself. But just in
proportion as the bed of the stream is elevated, the height of the water
in the annual inundations is increased also, and as the inclination of
the channel is diminished, the rapidity of the current is checked, and
the deposition of the slime it holds in suspension consequently
promoted. Thus the winds and the water, moving in contrary directions,
join in producing a common effect.
The sand, blown over the Delta and the cultivated land higher up the
stream during the inundation, is covered or mixed with the fertile earth
brought down by the river, and no serious injury is sustained from it.
That spread over the same ground after the water has subsided, and
during the short period when the soil is not stirred by cultivation or
covered by the flood, forms a thin pellicle over the surface as far as
it extends, and serves to divide and distinguish the successive layers
of slime deposited by the annual inundations. The particles taken up by
the wind on the sea beach are borne onward, by a hopping motion, or
rolled along the surface, until they are arrested by the temporary
cessation of the wind, by vegetation, or by some other obstruction, and
they may, in process of time, accumulate in large masses, under the lee
of rocky projections, buildings, or other barriers which break the force
of the wind.
In these facts we find the true explanation of the sand drifts, which
have half buried the Sphinx and so many other ancient monuments in that
part of Egypt. These drifts, as I have said, are not primarily from the
desert, but from the sea; and, as might be supposed from the distance
they have travelled, they have been long in gathering. While Egypt was a
great and flourishing kingdom, measures were taken to protect its
territory against the encroachment of sand, whether from the desert or
from the sea; but the foreign conquerors, who destroyed so many of its
religious monuments, did not spare its public works, and the process of
physical degradation undoubtedly began as early as the Persian invasion.
The urgent necessity, which has compelled all the successive tyrannies
of Egypt to keep up some of the canals and other arrangements for
irrigation, was not felt with respect to the advancement of the sands;
for their progress was so slow as hardly to be perceptible in the course
of a single reign, and long experience has shown that, from the natural
effect of the inundations, the cultivable soil of the valley is, on the
whole, trenching upon the domain of the desert, not retreating before
it.
The oases of the Libyan, as well as of many Asiatic deserts, have no
such safeguards. The sands are fast encroaching upon them, and threaten
soon to engulf them, unless man shall resort to artesian wells and
plantations, or to some other efficient means of checking the advance of
this formidable enemy, in time to save these islands of the waste from
final destruction.
Accumulations of sand are, in certain cases, beneficial as a protection
against the ravages of the sea; but, in general, the vicinity, and
especially the shifting of bodies of this material, are destructive to
human industry, and hence, in civilized countries, measures are taken to
prevent its spread. This, however, can be done only where the population
is large and enlightened, and the value of the soil, or of the
artificial erections and improvements upon it, is considerable. Hence in
the deserts of Africa and of Asia, and the inhabited lands which border
on them, no pains are usually taken to check the drifts, and when once
the fields, the houses, the springs, or the canals of irrigation are
covered or choked, the district is abandoned without a struggle, and
surrendered to perpetual desolation.[420]
_Sand Dunes and Sand Plains._
Two forms of sand deposit are specially important in European and
American geography. The one is that of dune or shifting hillock upon the
coast, the other that of barren plain in the interior. The coast dunes
are composed of sand washed up from the depths of the sea by the waves,
and heaped in knolls and ridges by the winds. The sand with which many
plains are covered, appears sometimes to have been deposited upon them
while they were yet submerged, sometimes to have been drifted from the
sea coast, and scattered over them by wind currents, sometimes to have
been washed upon them by running water. In these latter cases, the
deposit, though in itself considerable, is comparatively narrow in
extent and irregular in distribution, while, in the former, it is often
evenly spread over a very wide surface. In all great bodies of either
sort, the silicious grains are the principal constituent, though, when
not resulting from the disintegration of silicious rock and still
remaining in place, they are generally accompanied with a greater or
less admixture of other mineral particles, and of animal and vegetable
remains,[421] and they are, also, usually somewhat changed in
consistence by the ever-varying conditions of temperature and moisture
to which they have been exposed since their deposit. Unless the
proportion of these latter ingredients is so large as to create a
certain adhesiveness in the mass--in which case it can no longer
properly be called sand--it is infertile, and, if not charged with
water, partially agglutinated by iron, lime, or other cement, or
confined by alluvion resting upon it, it is much inclined to drift,
whenever, by any chance, the vegetable network which, in most cases,
thinly clothes and at the same time confines it, is broken.
Human industry has not only fixed the flying dunes, but, by mixing clay
and other tenacious earths with the superficial stratum of extensive
sand plains, and by the application of fertilizing substances, it has
made them abundantly productive of vegetable life. These latter
processes belong to agriculture and not to geography, and, therefore,
are not embraced within the scope of the present subject. But the
preliminary steps, whereby wastes of loose, drifting barren sands are
transformed into wooded knolls and plains, and finally, through the
accumulation of vegetable mould, into arable ground, constitute a
conquest over nature which precedes agriculture--a geographical
revolution--and, therefore, an account of the means by which the change
has been effected belongs properly to the history of man's influence on
the great features of physical geography. I proceed, then, to examine
the structure of dunes, and to describe the warfare man wages with the
sand hills, striving on the one hand to maintain and even extend them,
as a natural barrier against encroachments of the sea, and, on the
other, to check their moving and wandering propensities, and prevent
them from trespassing upon the fields he has planted and the habitations
in which he dwells.
_Coast Dunes._
Coast dunes are oblong ridges or round hillocks, formed by the action of
the wind upon sands thrown up by the waves on the beach of seas, and
sometimes of fresh-water lakes. On most coasts, the supply of sand for
the formation of dunes is derived from tidal waves. The flow of the tide
is more rapid, and consequently its transporting power greater, than
that of the ebb; the momentum, acquired by the heavy particles in
rolling in with the water, tends to carry them even beyond the flow of
the waves; and at the turn of the tide, the water is in a state of
repose long enough to allow it to let fall much of the solid matter it
holds in suspension. Hence, on all low, tide-washed coasts of seas with
sandy bottoms, there exist several conditions favorable to the formation
of sand deposits along high-water mark.[422] If the land winds are of
greater frequency, duration, or strength than the sea winds, the sands
left by the retreating wave will be constantly blown back into the
water; but if the prevailing air currents are in the opposite direction,
the sands will soon be carried out of the reach of the highest waves,
and transported continually farther and farther into the interior of the
land, unless obstructed by high grounds, vegetation, or other obstacles.
The tide, though a usual, is by no means a necessary condition for the
accumulations of sand out of which dunes are formed. The Baltic and the
Mediterranean are almost tideless seas, but there are dunes on the
Russian and Prussian coasts of the Baltic, and at the mouths of the Nile
and many other points on the shores of the Mediterranean. The vast
shoals in the latter sea, known to the ancients as the Greater and
Lesser Syrtis, are of marine origin. They are still filling up with
sand, washed up from greater depths, or sometimes drifted from the coast
in small quantities, and will probably be converted, at some future
period, into dry land covered with sand hills. There are also extensive
ranges of dunes upon the eastern shores of the Caspian, and at the
southern, or rather southeastern extremity of Lake Michigan.[423] There
is no doubt that this latter lake formerly extended much farther in that
direction, but its southern portion has gradually shoaled and at last
been converted into solid land, in consequence of the prevalence of the
northwest winds. These blow over the lake a large part of the year, and
create a southwardly set of the currents, which wash up sand from the
bed of the lake and throw it on shore. Sand is taken up from the beach
at Michigan City by every wind from that quarter, and, after a heavy
blow of some hours' duration, sand ridges may be observed on the north
side of the fences, like the snow wreaths deposited by a drifting wind
in winter. Some of the particles are carried back by contrary winds, but
most of them lodge on or behind the dunes, or in the moist soil near the
lake, or are entangled by vegetables, and tend permanently to elevate
the level. Like effects are produced by constant sea winds, and dunes
will generally be formed on all low coasts where such prevail, whether
in tideless or in tidal waters.
Jobard thus describes the _modus operandi_, under ordinary
circumstances, at the mouths of the Nile, where a tide can scarcely be
detected: "When a wave breaks, it deposits an almost imperceptible line
of fine sand. The next wave brings also its contribution, and shoves the
preceding line a little higher. As soon as the particles are fairly out
of the reach of the water they are dried by the heat of the burning sun,
and immediately seized by the wind and rolled or borne farther inland.
The gravel is not thrown out by the waves, but rolls backward and
forward until it is worn down to the state of fine sand, when it, in its
turn, is cast upon the land and taken up by the wind."[424] This
description applies only to the common every-day action of wind and
water; but just in proportion to the increasing force of the wind and
the waves, there is an increase in the quantity of sand, and in the
magnitude of the particles carried off from the beach by it, and, of
course, every storm in a landward direction adds sensibly to the
accumulation upon the shore.
_Sand Banks._
Although dunes, properly so called, are found only on dry land and above
ordinary high-water mark, and owe their elevation and structure to the
action of the wind, yet, upon many shelving coasts, accumulations of
sand much resembling dunes are formed under water at some distance from
the shore by the oscillations of the waves, and are well known by the
name of sand banks. They are usually rather ridges than banks, of
moderate inclination, and with the steepest slope seaward; and their
form differs from that of dunes only in being lower and more continuous.
Upon the western coast of the island of Amrum, for example, there are
three rows of such banks, the summits of which are at a distance of
perhaps a couple of miles from each other; so that, including the width
of the banks themselves, the spaces between them, and the breadth of the
zone of dunes upon the land, the belt of moving sands on that coast is
probably not less than eight miles wide.
Under ordinary circumstances, sand banks are always rolling landward,
and they compose the magazine from which the material for the dunes is
derived. The dunes, in fact, are but aquatic sand banks transferred to
dry land. The laws of their formation are closely analogous, because the
action of the two fluids, by which they are respectively accumulated and
built up, is very similar when brought to bear upon loose particles of
solid matter. It would, indeed, seem that the slow and comparatively
regular movements of the heavy, unelastic water ought to affect such
particles very differently from the sudden and fitful impulses of the
light and elastic air. But the velocity of the wind currents gives them
a mechanical force approximating to that of the slower waves, and,
however difficult it may be to explain all the phenomena that
characterize the structure of the dunes, observation has proved that it
is nearly identical with that of submerged sand banks. The differences
of form are generally ascribable to the greater number and variety of
surface accidents of the ground on which the sand hills of the land are
built up, and to the more frequent changes, and wider variety of
direction, in the courses of the wind.
_Dunes on the Coast of America._
Upon the Atlantic coast of the United States, the prevalence of western
or off-shore winds is unfavorable to the formation of dunes, and, though
marine currents lodge vast quantities of sand, in the form of banks, on
that coast, its shores are proportionally more free from sand hills than
some others of lesser extent. There are, however, very important
exceptions. The action of the tide throws much sand upon some points of
the New England coast, as well as upon the beaches of Long Island and
other more southern shores, and here dunes resembling those of Europe
are formed. There are also extensive ranges of dunes on the Pacific
coast of the United States, and at San Francisco they border some of the
streets of the city.
The dunes of America are far older than her civilization, and the soil
they threaten or protect possesses, in general, too little value to
justify any great expenditure in measures for arresting their progress
or preventing their destruction. Hence, great as is their extent and
their geographical importance, they have, at present, no such intimate
relations to human life as to render them objects of special interest in
the point of view I am taking, and I do not know that the laws of their
formation and motion have been made a subject of original investigation
by any American observer.
_Dunes of Western Europe._
Upon the western coast of Europe, on the contrary, the ravages
occasioned by the movement of sand dunes, and the serious consequences
often resulting from the destruction of them, have long engaged the
earnest attention of governments and of scientific men, and for nearly a
century persevering and systematic effort has been made to bring them
under human control. The subject has been carefully studied in Denmark
and the adjacent duchies, in Western Prussia, in the Netherlands, and in
France; and the experiments in the way of arresting the drifting of the
dunes, and of securing them, and the lands they shelter, from the
encroachments of the sea, have resulted in the adoption of a system of
coast improvement substantially the same in all these countries. The
sands, like the forests, have now their special literature, and the
volumes and memoirs, which describe them and the processes employed to
subdue them, are full of scientific interest and of practical
instruction.[425]
_Formation of Dunes._
The laws which govern the formation of dunes are substantially these. We
have seen that, under certain conditions, sand is accumulated above
high-water mark on low sea and lake shores. So long as the sand is kept
wet by the spray or by capillary attraction, it is not disturbed by air
currents, but as soon as the waves retire sufficiently to allow it to
dry, it becomes the sport of the wind, and is driven up the gently
sloping beach until it is arrested by stones, vegetables, or other
obstructions, and thus an accumulation is formed which constitutes the
foundation of a dune. However slight the elevation thus created, it
serves to stop or retard the progress of the sand grains which are
driven against its shoreward face, and to protect from the further
influence of the wind the particles which are borne beyond it, or rolled
over its crest, and fall down behind it. If the shore above the beach
line were perfectly level and straight, the grass or bushes upon it of
equal height, the sand thrown up by the waves uniform in size and weight
of particles as well as in distribution, and if the action of the wind
were steady and regular, a continuous bank would be formed, everywhere
alike in height and cross section. But no such constant conditions
anywhere exist. The banks are curved, broken, unequal in elevation; they
are sometimes bare, sometimes clothed with vegetables of different
structure and dimensions; the sand thrown up is variable in quantity and
character; and the winds are shifting, gusty, vortical, and often
blowing in very narrow currents. From all these causes, instead of
uniform hills, there rise irregular rows of sand heaps, and these, as
would naturally be expected, are of a pyramidal, or rather conical
shape, and connected at bottom by more or less continuous ridges of the
same material.
On a receding coast, dunes will not attain so great a height as on more
secure shores, because they are undermined and carried off before they
have time to reach their greatest dimensions. Hence, while at sheltered
points in Southwestern France, there are dunes three hundred feet or
more in height, those on the Frisic Islands and the exposed parts of the
coast of Schleswig-Holstein range only from twenty to one hundred feet.
On the western shores of Africa, it is said that they sometimes attain
an elevation of six hundred feet. This is one of the very few points
known to geographers where desert sands are advancing seaward, and here
they rise to the greatest altitude to which sand grains can be carried
by the wind.
The hillocks, once deposited, are held together and kept in shape,
partly by mere gravity, and partly by the slight cohesion of the lime,
clay, and organic matter mixed with the sand; and it is observed that,
from capillary attraction, evaporation from lower strata, and retention
of rain water, they are always moist a little below the surface.[426] By
successive accumulations, they gradually rise to the height of thirty,
fifty, sixty, or a hundred feet, and sometimes even much higher. Strong
winds, instead of adding to their elevation, sweep off loose particles
from their surface, and these, with others blown over or between them,
build up a second row of dunes, and so on according to the character of
the wind, the supply and consistence of the sand, and the face of the
country. In this way is formed a belt of sand dunes, irregularly
dispersed and varying much in height and dimensions, and some times many
miles in breadth. On the Island of Sylt, in the German Sea, where there
are several rows, the width of the belt is from half a mile to a mile.
There are similar ranges on the coast of Holland, exceeding two miles in
breadth, while at the mouths of the Nile they form a zone not less than
ten miles wide. The base of some of the dunes in the Delta of the Nile
is reached by the river during the annual inundation, and the
infiltration of the water, which contains lime, has converted the lower
strata into a silicious limestone, or rather a calcareous sandstone, and
thus afforded an opportunity of studying the structure of that rock in a
locality where its origin and mode of aggregation and solidification are
known.
_Character of Dune Sand._
"Dune sand," says Staring, "consists of well-rounded grains of quartz,
more or less colored by iron, and often mingled with fragments of
shells, small indeed, but still visible to the naked eye.[427] These
fragments are not constant constituents of dune sand. They are sometimes
found at the very summits of the hillocks, as at Overveen; in the King's
Dune, near Egmond, they form a coarse calcareous gravel very largely
distributed through the sand, while the interior dunes between Haarlem
and Warmond exhibit no trace of them. It is yet undecided whether the
presence or absence of these fragments is determined by the period of
the formation of the dunes, or whether it depends on a difference in the
process by which different dunes have been accumulated. Land shells,
such as snails, for example, are found on the surface of the dunes in
abundance, and many of the shelly fragments in the interior of the
hillocks may be derived from the same source."[428]
J. G. Kohl has some poetical thoughts upon the origin and character of
the dune sands, which are worth quoting:
"The sand was composed of pure transparent quartz. I could not observe
this sand without the greatest admiration. If it is the product of the
waves, breaking and crushing flints and fragments of quartz against each
other, it is a result which could be brought about only in the course of
countless ages. We need not lift ourselves to the stars, to their
incalculable magnitudes and distances and numbers, in order to feel the
giddiness of astonishment. Here, upon earth, in the simple sand, we find
miracle enough. Think of the number of sand grains contained in a single
dune, then of all the dunes upon this widely extended coast--not to
speak of the innumerable grains in the Arabian, African, and Prussian
deserts--this, of itself, is sufficient to overwhelm a thoughtful fancy.
How long, how many times must the waves have risen and sunk in order to
reduce these vast heaps to powder!
"During the whole time I spent on this coast, I had always some sand in
my fingers, was rubbing and rolling it about, examining it on all sides,
holding a little shining grain on the tip of my finger, and thinking to
myself how, in its corners, its angles, its whole configuration, it
might very probably have a history longer than that of the old German
nation--possibly longer than that of the human race. Where was the
original quartz crystal, of which this is a fragment, first formed? To
what was it once fixed? What power broke it loose? How was it beaten
smaller and ever smaller by the waves? They tossed it, for æons, to and
fro upon the beach, rolled it up and down, forced it to make thousands
and thousands of daily voyages for millions and millions of days. Then
the wind bore it away, and used it in building up a dune; there it lay
for centuries, packed in with its fellows, protecting the marshes and
cherished by the inhabitants, till, seized again by the pursuing sea, it
fell once more into the water, there to begin the endless dance
anew--and again to be swept away by the wind--and again to find rest in
the dunes, a protection and a blessing to the coast. There is something
mysterious about such a grain of sand, and at last I went so far as to
fancy a little immortal spark linked with each one, presiding over its
destiny, and sharing its vicissitudes. Could we arm our eyes with a
microscope, and then dive, like a sparling, into one of these dunes, the
pile, which is in fact only a heap of countless little crystal blocks,
would strike us as the most marvellous building upon earth. The sunbeams
would pass, with illuminating power, through all these little
crystalline bodies. We should see how every sand grain is formed, by
what multifarious little facets it is bounded, we should even discover
that it is itself composed of many distinct particles."[429]
Sand concretions form within the dunes and especially in the depressions
between them. These are sometimes so extensive and impervious as to
retain a sufficient supply of water to feed perennial springs, and to
form small permanent ponds, and they are a great impediment to the
penetration of roots, and consequently to the growth of trees planted,
or germinating from self-sown seeds, upon the dunes.[430]
_Interior Structure of Dunes._
The interior structure of the dunes, the arrangement of their particles,
is not, as might be expected, that of an unorganized, confused heap, but
they show a strong tendency to stratification. This is a point of much
geological interest, because it indicates that sandstone may owe its
stratified character to the action of wind as well as of water. The
origin and peculiar character of these layers are due to a variety of
causes. A southwest wind and current may deposit upon a dune a stratum
of a given color and mineral composition, and this may be succeeded by a
northwest wind and current, bringing with them particles of a different
hue, constitution, and origin.
Again, if we suppose a violent tempest to strew the beach with sand
grains very different in magnitude and specific gravity, and, after the
sand is dry, to be succeeded by a gentle breeze, it is evident that only
the lighter particles will be taken up and carried to the dunes. If,
after some time, the wind freshens, heavier grains will be transported
and deposited on the former, and a still stronger succeeding gale will
roll up yet larger kernels. Each of these deposits will form a stratum.
If we suppose the tempest to be followed, after the sand is dry, not by
a gentle breeze, but by a wind powerful enough to lift at the same time
particles of very various magnitudes and weights, the heaviest will
often lodge on the dune while the lighter will be carried farther. This
would produce a stratum of coarse sand, and the same effect might result
from the blowing away of light particles out of a mixed layer, while the
heavier remained undisturbed.[431] Still another cause of
stratification may be found in the occasional interposition of a thin
layer of leaves or other vegetable remains between successive deposits,
and this I imagine to be more frequent than has been generally supposed.
The eddies of strong winds between the hillocks must also occasion
disturbances and re-arrangements of the sand layers, and it seems
possible that the irregular thickness and the strange contortions of the
strata of the sandstone at Petra may be due to some such cause. A
curious observation of Professor Forchhammer suggests an explanation of
another peculiarity in the structure of the sandstone of Mount Seir. He
describes dunes in Jutland, composed of yellow quartzose sand intermixed
with black titanian iron. When the wind blows over the surface of the
dunes, it furrows the sand with alternate ridges and depressions,
ripples, in short, like those of water. The swells, the dividing ridges
of the system of sand ripples, are composed of the light grains of
quartz, while the heavier iron rolls into the depressions between, and
thus the whole surface of the dune appears as if covered with a fine
black network.
_Form of Dunes._
The sea side of dunes, being more exposed to the caprices of the wind,
is more irregular in form than the lee or land side, where the
arrangement of the particles is affected by fewer disturbing and
conflicting influences. Hence, the stratification of the windward slope
is somewhat confused, while the sand on the lee side is found to be
disposed in more regular beds, inclining landward, and with the largest
particles lowest, where their greater weight would naturally carry them.
The lee side of the dunes, being thus formed of sand deposited according
to the laws of gravity, is very uniform in its slope, which, according
to Forchhammer, varies little from an angle of 30° with the horizon,
while the more exposed and irregular weather side lies at an inclination
of from 5° to 10°. When, however, the outer tier of dunes is formed so
near the waterline as to be exposed to the immediate action of the
waves, it is undermined, and the face of the hill is very steep and
sometimes nearly perpendicular.
_Geological Importance of Dunes._
These observations, and other facts which a more attentive study on the
spot would detect, might furnish the means of determining interesting
and important questions concerning geological formations in localities
very unlike those where dunes are now thrown up. For example, Studer
supposes that the drifting sand hills of the African desert were
originally coast dunes, and that they have been transported to their
present position far in the interior, by the rolling and shifting
leeward movement to which all dunes not covered with vegetation are
subject. The present general drift of the sands of that desert appears
to be to the southwest and west, the prevailing winds blowing from the
northeast and east; but it has been doubted whether the shoals of the
western coast of Northern Africa, and the sands upon that shore, are
derived from the bottom of the Atlantic, in the usual manner, or, by an
inverse process, from those of the Sahara. The latter, as has been
before remarked, is probably the truth, though observations are wanting
to decide the question.[432] There is nothing violently improbable in
the supposition that they may have been first thrown up by the
Mediterranean on its Libyan coast, and thence blown south and west over
the vast space they now cover. But whatever has been their source and
movement, they can hardly fail to have left on their route some
sandstone monuments to mark their progress, such, for example, as we
have seen are formed from the dune sand at the mouth of the Nile; and it
is conceivable that the character of the drifting sands themselves, and
of the conglomerates and sandstones to whose formation they have
contributed, might furnish satisfactory evidence as to their origin,
their starting point, and the course by which they have wandered so far
from the sea.[433]
If the sand of coast dunes is, as Staring describes it, composed chiefly
of well-rounded quartzose grains, fragments of shells, and other
constant ingredients, it would often be recognizable as coast sand, in
its agglutinate state of sandstone. The texture of this rock varies from
an almost imperceptible fineness of grain to great coarseness, and
affords good facilities for microscopic observation of its structure.
There are sandstones, such, for example, as are used for grindstones,
where the grit, as it is called, is of exceeding sharpness; others where
the angles of the grains are so obtuse that they scarcely act at all on
hard metals. The former may be composed of grains of rock, disintegrated
indeed, and recemented together, but not, in the meanwhile, much rolled;
the latter, of sands long washed by the sea, and drifted by land winds.
There is, indeed, so much resemblance between the effects of driving
winds and of rolling water upon light bodies, that there would be
difficulty in distinguishing them;[434] but after all, it is not
probable that sandstone, composed of grains thrown up from the salt sea,
and long tossed by the winds, would be identical in its structure with
that formed from fragments of rock crushed by mechanical force, or
disintegrated by heat, and again agglutinated without much exposure to
the action of moving water.[435]
_Inland Dunes._
I have met with some observations indicating a structural difference
between interior and coast dunes, which might perhaps be recognized in
the sandstones formed from these two species of sand hills respectively.
In the great American desert between the Andes and the Pacific, Meyen
found sand heaps of a perfect falciform shape.[436] They were from seven
to fifteen feet high, the chord of their arc measuring from twenty to
seventy paces. The slope of the convex face is described as very small,
that of the concave as high as 70° or 80°, and their surfaces were
rippled. No smaller dunes were observed, nor any in the process of
formation. The concave side uniformly faced the northwest, except toward
the centre of the desert, where, for a distance of one or two hundred
paces, they gradually opened to the west, and then again gradually
resumed the former position.
Pöppig ascribes a falciform shape to the movable, a conical to the fixed
dunes, or _medanos_, of the same desert. "The medanos," he observes,
"are hillock-like elevations of sand, some having a firm, others a loose
base. The former [latter], which are always crescent shaped, are from
ten to twenty feet high, and have an acute crest. The inner side is
perpendicular, and the outer or bow side forms an angle with a steep
inclination downward. When driven by violent winds, the medanos pass
rapidly over the plains. The smaller and lighter ones move quickly
forward, before the larger; but the latter soon overtake and crush them,
whilst they are themselves shivered by the collision. These medanos
assume all sorts of extraordinary figures, and sometimes move along the
plain in rows forming most intricate labyrinths. * * A plain often
appears to be covered with a row of medanos, and some days afterward it
is again restored to its level and uniform aspect. * * *
"The medanos with immovable bases are formed on the blocks of rocks
which are scattered about the plain. The sand is driven against them by
the wind, and as soon as it reaches the top point, it descends on the
other side until that is likewise covered; thus gradually arises a
conical-formed hill. Entire hillock chains with acute crests are formed
in a similar manner. * * * On their southern declivities are found vast
masses of sand, drifted thither by the mid-day gales. The northern
declivity, though not steeper than the southern, is only sparingly
covered with sand. If a hillock chain somewhat distant from the sea
extends in a line parallel with the Andes, namely, from S. S. E. to N.
N. W., the western declivity is almost entirely free of sand, as it is
driven to the plain below by the southeast wind, which constantly
alternates with the wind from the south."[437]
It is difficult to reconcile this description with that of Meyen, but if
confidence is to be reposed in the accuracy of either observer, the
formation of the sand hills in question must be governed by very
different laws from those which determine the structure of coast dunes.
Captain Gilliss, of the American navy, found the sand hills of the
Peruvian desert to be in general crescent shaped, as described by Meyen,
and a similar structure is said to characterize the inland dunes of the
Llano Estacado and other plateaus of the North American desert, though
these latter are of greater height and other dimensions than those
described by Meyen. There is no very obvious explanation of this
difference in form between maritime and inland sand hills, and the
subject merits investigation.[438]
_Age, Character, and Permanence of Dunes._
The origin of most great lines of dunes goes back past all history.
There are on many coasts, several distinct ranges of sand hills which
seem to be of very different ages, and to have been formed under
different relative conditions of land and water.[439] In some cases,
there has been an upheaval of the coast line since the formation of the
oldest hillocks, and these have become inland dunes, while younger rows
have been thrown up on the new beach laid bare by elevation of the sea
bed. Our knowledge of the mode of their first accumulation is derived
from observation of the action of wind and water in the few instances
where, with or without the aid of man, new coast dunes have been
accumulated, and of the influence of wind alone in elevating new sand
heaps inland of the coast tier, when the outer rows are destroyed by the
sea, as also when the sodded surface of ancient sands has been broken,
and the subjacent strata laid open to the air.
It is a question of much interest, in what degree the naked condition of
most dunes is to be ascribed to the improvidence and indiscretion of
man. There are, in Western France, extensive ranges of dunes covered
with ancient and dense forests, while the recently formed sand hills
between them and the sea are bare of vegetation, and are rapidly
advancing upon the wooded dunes, which they threaten to bury beneath
their drifts. Between the old dunes and the new, there is no
discoverable difference in material or in structure; but the modern sand
hills are naked and shifting, the ancient, clothed with vegetation and
fixed. It has been conjectured that artificial methods of confinement
and plantation were employed by the primitive inhabitants of Gaul; and
Laval, basing his calculations on the rate of annual movement of the
shifting dunes, assigns the fifth century of the Christian era as the
period when these processes were abandoned.[440]
There is no historical evidence that the Gauls were acquainted with
artificial methods of fixing the sands of the coast, and we have little
reason to suppose that they were advanced enough in civilization to be
likely to resort to such processes, especially at a period when land
could have had but a moderate value.
In other countries, dunes have spontaneously clothed themselves with
forests, and the rapidity with which their surface is covered by various
species of sand plants, and finally by trees, where man and cattle and
burrowing animals are excluded from them, renders it highly probable
that they would, as a general rule, protect themselves, if left to the
undisturbed action of natural causes. The sand hills of the Frische
Nehrung, on the coast of Prussia, were formerly wooded down to the
water's edge, and it was only in the last century that, in consequence
of the destruction of their forests, they became moving sands.[441]
There is every reason to believe that the dunes of the Netherlands were
clothed with trees until after the Roman invasion. The old geographers,
in describing these countries, speak of vast forests extending to the
very brink of the sea; but drifting coast dunes are first mentioned by
the chroniclers of the Middle Ages, and so far as we know they have
assumed a destructive character in consequence of the improvidence of
man.[442] The history of the dunes of Michigan, so far as I have been
able to learn from my own observation, or that of others, is the same.
Thirty years ago, when that region was scarcely inhabited, they were
generally covered with a thick growth of trees, chiefly pines, and
underwood, and there was little appearance of undermining and wash on
the lake side, or of shifting of the sands, except where the trees had
been cut or turned up by the roots.[443]
Nature, as she builds up dunes for the protection of the sea shore,
provides, with similar conservatism, for the preservation of the dunes
themselves; so that, without the interference of man, these hillocks
would be, not perhaps absolutely perpetual, but very lasting in
duration, and very slowly altered in form or position. When once covered
with the trees, shrubs, and herbaceous growths adapted to such
localities, dunes undergo no apparent change, except the slow occasional
undermining of the outer tier, and accidental destruction by the
exposure of the interior, from the burrowing of animals, or the
upturning of trees with their roots, and all these causes of
displacement are very much less destructive when a vegetable covering
exists in the immediate neighborhood of the breach.
Before the occupation of the coasts by civilized and therefore
destructive man, dunes, at all points where they have been observed,
seem to have been protected in their rear by forests, which served to
break the force of the winds in both directions,[444] and to have
spontaneously clothed themselves with a dense growth of the various
plants, grasses, shrubs, and trees, which nature has assigned to such
soils. It is observed in Europe that dunes, though now without the
shelter of a forest country behind them, begin to protect themselves as
soon as human trespassers are excluded, and grazing animals denied
access to them. Herbaceous and arborescent plants spring up almost at
once, first in the depressions, and then upon the surface of the sand
hills. Every seed that sprouts, binds together a certain amount of sand
by its roots, shades a little ground with its leaves, and furnishes food
and shelter for still younger or smaller growths. A succession of a very
few favorable seasons suffices to bind the whole surface together with a
vegetable network, and the power of resistance possessed by the dunes
themselves, and the protection they afford to the fields behind them,
are just in proportion to the abundance and density of the plants they
support.
The growth of the vegetable covering can, of course, be much accelerated
by judicious planting and watchful care, and this species of improvement
is now carried on upon a vast scale, wherever the value of land is
considerable and the population dense. In the main, the dunes on the
coast of the German Sea, notwithstanding the great quantity of often
fertile land they cover, and the evils which result from their
movement, are, upon the whole, a protective and beneficial agent, and
their maintenance is an object of solicitude with the governments and
people of the shores they protect.[445]
_Use of Dunes as a Barrier against the Sea._
Although the sea throws up large quantities of sand on flat lee-shores,
there are, as we have seen, many cases where it continually encroaches
on those same shores and washes them away. At all points of the shallow
North Sea where the agitation of the waves extends to the bottom, banks
are forming and rolling eastward. Hence the sea sand tends to accumulate
upon the coast of Schleswig-Holstein and Jutland, and were there no
conflicting influences, the shore would rapidly extend itself westward.
But the same waves which wash the sand to the coast undermine the beach
they cover, and still more rapidly degrade the shore at points where it
is too high to receive partial protection by the formation of dunes upon
it. The earth of the coast is generally composed of particles finer,
lighter, and more transportable by water than the sea sand. While,
therefore, the billows raised by a heavy west wind may roll up and
deposit along the beach thousands of tons of sand, the same waves may
swallow up even a larger quantity of fine shore earth. This earth, with
a portion of the sand, is swept off by northwardly and southwardly
currents, and let fall at other points of the coast, or carried off,
altogether, out of the reach of causes which might bring it back to its
former position.
Although, then, the eastern shore of the German Ocean here and there
advances into the sea, it in general retreats before it, and but for the
protection afforded it by natural arrangements seconded by the art and
industry of man, whole provinces would soon be engulfed by the waters.
This protection consists in an almost unbroken chain of sand banks and
dunes, extending from the northernmost point of Jutland to the Elbe, a
distance of not much less than three hundred miles, and from the Elbe
again, though with more frequent and wider interruptions, to the
Atlantic borders of France and Spain.[446] So long as the dunes are
maintained by nature or by human art, they serve, like any other
embankment or dike, as a partial or a complete protection against the
encroachments of the sea; and on the other hand, when their drifts are
not checked by natural processes, or by the industry of man, they become
a cause of as certain, if not of as sudden, destruction as the ocean
itself whose advance they retard.
_Encroachments of the Sea._
The eastward progress of the sea on the Danish and Netherlandish coast,
and on certain shores of the Atlantic, depends so much on local
geological structure, on the force and direction of tidal and other
marine currents, on the volume and rapidity of coast rivers, on the
contingencies of the weather and on other varying circumstances, that no
general rate can he assigned to it.
At Agger, near the western end of the Liimfjord, in Jutland, the coast
was washed away, between the years 1815 and 1839, at the rate of more
than eighteen feet a year. The advance of the sea appears to have been
something less rapid for a century before; but from 1840 to 1857, it
gained upon the land no less than thirty feet a year. At other points of
the shore of Jutland, the loss is smaller, but the sea is encroaching
generally upon the whole line of the coast.[447]
_The Liimfjord._
The irruption of the sea into the fresh-water lagoon of Liimfjord in
Jutland, in 1825--one of the most remarkable encroachments of the ocean
in modern times--is expressly ascribed to "mismanagement of the dunes"
on the narrow neck of land which separated the fjord from the North Sea.
At earlier periods, the sea had swept across the isthmus, and even burst
through it, but the channel had been filled up again, sometimes by
artificial means, sometimes by the operation of natural causes, and on
all these occasions effects were produced very similar to those
resulting from the formation of the new channel in 1825, which still
remains open.[448] Within comparatively recent historical ages, the
Liimfjord has thus been several times alternately filled with fresh and
with salt water, and man has produced, by neglecting the dunes, or at
least might have prevented by maintaining them, changes identical with
those which are usually ascribed to the action of great geological
causes, and sometimes supposed to have required vast periods of time for
their accomplishment.
"This breach," says Forchhammer, "which converted the Liimfjord into a
sound, and the northern part of Jutland into an island, occasioned
remarkable changes. The first and most striking phenomenon was the
sudden destruction of almost all the fresh-water fish previously
inhabiting this lagoon, which was famous for its abundant fisheries.
Millions of fresh-water fish were thrown on shore, partly dead and
partly dying, and were carted off by the people. A few only survived,
and still frequent the shores at the mouth of the brooks. The eel,
however, has gradually accommodated itself to the change of
circumstances, and is found in all parts of the fjord, while to all
other fresh-water fish, the salt water of the ocean seems to have been
fatal. It is more than probable that the sand washed in by the irruption
covers, in many places, a layer of dead fish, and has thus prepared the
way for a petrified stratum similar to those observed in so many older
formations.
"As it seems to be a law of nature that animals whose life is suddenly
extinguished while yet in full vigor, are the most likely to be
preserved by petrification, we find here one of the conditions favorable
to the formation of such a petrified stratum. The bottom of the
Liimfjord was covered with a vigorous growth of aquatic plants,
belonging both to fresh and to salt water, especially _Zostera marina_.
This vegetation totally disappeared after the irruption, and, in some
instances, was buried by the sand; and here again we have a familiar
phenomenon often observed in ancient strata--the indication of a given
formation by a particular vegetable species--and when the strata
deposited at the time of the breach shall be accessible by upheaval, the
period of eruption will be marked by a stratum of _Zostera_, and
probably by impressions of fresh-water fishes.
"It is very remarkable that the _Zostera marina_, a sea plant, was
destroyed even where no sand was deposited. This was probably in
consequence of the sudden change from brackish to salt water. * * It is
well established that the Liimfjord communicated with the German Ocean
at some former period. To that era belong the deep beds of oyster shells
and _Cardium edule_, which are still found at the bottom of the fjord.
And now, after an interval of centuries, during which the lagoon
contained no salt-water shell fish, it again produces great numbers of
_Mytilus edulis_. Could we obtain a deep section of the bottom, we
should find beds of _Ostrea edulis_ and _Cardium edule_, then a layer of
_Zostera marina_ with fresh-water fish, and then a bed of _Mytilus
edulis_. If, in course of time, the new channel should be closed, the
brooks would fill the lagoon again with fresh water; fresh-water fish
and shell fish would reappear, and thus we should have a repeated
alternation of organic inhabitants of the sea and of the waters of the
land.
"These events have been accompanied with but a comparatively
insignificant change of land surface, while the formations in the bed of
this inland sea have been totally revolutionized in character."[449]
_Coasts of Schleswig-Holstein, Holland, and France._
On the islands on the coast of Schleswig-Holstein, the advance of the
sea has been more unequivocal and more rapid. Near the beginning of the
last century, the dunes which had protected the western coast of the
island of Sylt began to roll to the east, and the sea followed closely
as they retired. In 1757, the church of Rantum, a village upon that
island, was obliged to be taken down in consequence of the advance of
the sand hills; in 1791, these hills had passed beyond its site, the
waves had swallowed up its foundations, and the sea gained so rapidly,
that, fifty years later, the spot where they lay was seven hundred feet
from the shore.[450]
The most prominent geological landmark on the coast of Holland is the
Huis te Britten, _Arx Britannica_, a fortress built by the Romans, in
the time of Caligula, on the main land near the mouth of the Rhine. At
the close of the seventeenth century, the sea had advanced sixteen
hundred paces beyond it. The older Dutch annalists record, with much
parade of numerical accuracy, frequent encroachments of the sea upon
many parts of the Netherlandish coast. But though the general fact of an
advance of the ocean upon the land is established beyond dispute, the
precision of the measurements which have been given is open to question.
Staring, however, who thinks the erosion of the coast much exaggerated
by popular geographers, admits a loss of more than a million and a half
acres, chiefly worthless morass;[451] and it is certain that but for the
resistance of man, but for his erection of dikes and protection of
dunes, there would now be left of Holland little but the name. It is, as
has been already seen, still a debated question among geologists whether
the coast of Holland now is, and for centuries has been, subsiding. I
believe most investigators maintain the affirmative; and if the fact is
so, the advance of the sea upon the land is, in part, due to this cause.
But the rate of subsidence is at all events very small, and therefore
the encroachments of the ocean upon the coast are mainly to be ascribed
to the erosion and transportation of the soil by marine waves and
currents.
The sea is fast advancing at several points of the western coast of
France, and unknown causes have given a new impulse to its ravages since
the commencement of the present century. Between 1830 and 1842, the
Point de Grave, on the north side of the Gironde, retreated one hundred
and eighty mètres, or about fifty feet per year; from the latter year to
1846, the rate was increased to more than three times that quantity, and
the loss in those four years was above six hundred feet. All the
buildings at the extremity of the peninsula have been taken down and
rebuilt farther landward, and the lighthouse of the Grave now occupies
its third position. The sea attacked the base of the peninsula also, and
the Point de Grave and the adjacent coasts have been for twenty years
the scene of one of the most obstinately contested struggles between man
and the ocean recorded in the annals of modern engineering.
It cannot, indeed, be affirmed that human power is able to arrest
altogether the incursions of the waves on sandy coasts, by planting the
beach, and clothing the dunes with wood. On the contrary, both in
Holland and on the French coast, it has been found necessary to protect
the dunes themselves by piling and by piers and sea walls of heavy
masonry. But experience has amply shown that the processes referred to
are entirely successful in preventing the movement of the dunes, and the
drifting of their sands over cultivated lands behind them; and that, at
the same time, the plantations very much retard the landward progress of
the waters.[452]
_Drifting of Dune Sands._
Besides their importance as a barrier against the inroads of the ocean,
dunes are useful by sheltering the cultivated ground behind them from
the violence of the sea wind, from salt spray, and from the drifts of
beach sand which would otherwise overwhelm them. But the dunes
themselves, unless their surface sands are kept moist, and confined by
the growth of plants, or at least by a crust of vegetable earth, are
constantly rolling inward; and thus, while, on one side, they lay bare
the traces of ancient human habitations or other evidences of the social
life of primitive man, they are, on the other, burying fields, houses,
churches, and converting populous districts into barren and deserted
wastes.
Especially destructive are they when, by any accident, a cavity is
opened into them to a considerable depth, thereby giving the wind access
to the interior, where the sand is thus first dried, and then scooped
out and scattered far over the neighboring soil. The dune is now a
magazine of sand, no longer a rampart against it, and mischief from this
source seems more difficult to resist than from almost any other drift,
because the supply of material at the command of the wind, is more
abundant and more concentrated than in its original thin and widespread
deposits on the beach. The burrowing of conies in the dunes is, in this
way, not unfrequently a cause of their destruction and of great injury
to the fields behind them. Drifts, and even inland sand hills, sometimes
result from breaking the surface of more level sand deposits, far within
the range of the coast dunes. Thus we learn from Staring, that one of
the highest inland dunes in Friesland owes its origin to the opening of
the drift sand by the uprooting of a large oak.[453]
Great as are the ravages produced by the encroachment of the sea upon
the western shores of continental Europe, they have been in some degree
compensated by spontaneous marine deposits at other points of the coast,
and we have seen in a former chapter that the industry of man has
reclaimed a large territory from the bosom of the ocean. These latter
triumphs are not of recent origin, and the incipient victories which
paved the way for them date back perhaps as far as ten centuries. In the
mean time, the dunes had been left to the operation of the laws of
nature, or rather freed, by human imprudence, from the fetters with
which nature had bound them, and it is scarcely three generations since
man first attempted to check their destructive movements. As they
advanced, he unresistingly yielded and retreated before them, and they
have buried under their sandy billows many hundreds of square miles of
luxuriant cornfields and vineyards and forests.
_Dunes of Gascony._
On the west coast of France, a belt of dunes, varying in width from a
quarter of a mile to five miles, extends from the Adour to the estuary
of the Gironde, and covers an area of three hundred and seventy-five
square miles. When not fixed by vegetable growths, they advance eastward
at a mean rate of about one rod, or sixteen and a half feet, a year. We
do not know historically when they began to drift, but if we suppose
their motion to have been always the same as at present, they would have
passed over the space between the sea coast and their eastern boundary,
and covered the large area above mentioned, in fourteen hundred years.
We know, from written records, that they have buried extensive fields
and forests and thriving villages, and changed the courses of rivers,
and that the lighter particles carried from them by the winds, even
where not transported in sufficient quantities to form sand hills, have
rendered sterile much land formerly fertile.[454] They have also
injuriously obstructed the natural drainage of the maritime districts by
choking up the beds of the streams, and forming lakes and pestilential
swamps of no inconsiderable extent. In fact, so completely do they
embank the coast, that between the Gironde and the village of Mimizan, a
distance of one hundred miles, there are but two outlets for the
discharge of all the waters which flow from the land to the sea; and the
eastern front of the dunes is bordered by a succession of stagnant
pools, some of which are more than six miles in length and breadth.[455]
_The Dunes of Denmark and Prussia._
In the small kingdom of Denmark, inclusive of the duchies of Schleswig
and Holstein, the dunes cover an area of more than two hundred and sixty
square miles. The breadth of the chain is very various, and in some
places it consists only of a single row of sand hills, while in others,
it is more than six miles wide. The general rate of eastward movement of
the drifting dunes is from three to twenty-four feet per annum. If we
adopt the mean of thirteen feet and a half for the annual motion, the
dunes have traversed the widest part of the belt in about twenty-five
hundred years. Historical data are wanting as to the period of the
formation of these dunes and of the commencement of their drifting; but
there is recorded evidence that they have buried a vast extent of
valuable land within three or four centuries, and further proof is found
in the fact that the movement of the sands is constantly uncovering
ruins of ancient buildings, and other evidences of human occupation, at
points far within the present limits of the uninhabitable desert.
Andresen estimates the average depth of the sand deposited over this
area at thirty feet, which would give a cubic mile and a half for the
total quantity.[456]
The drifting of the dunes on the coast of Prussia commenced not much
more than a hundred years ago. The Frische Nehrung is separated from the
mainland by the Frische Haff, and there is but a narrow strip of arable
land along its eastern borders. Hence its rolling sands have covered a
comparatively small extent of dry land, but fields and villages have
been buried and valuable forests laid waste by them. The loose coast row
has drifted over the inland ranges, which, as was noticed in the
description of these dunes on a former page, were protected by a surface
of different composition, and the sand has thus been raised to a height
which it could not have reached upon level ground. This elevation has
enabled it to advance upon and overwhelm woods, which, upon a plain,
would have checked its progress, and, in one instance, a forest of many
hundred acres of tall pines was destroyed by the drifts between 1804 and
1827.
_Control of Dunes by Man._
There are three principal modes in which the industry of man is brought
to bear upon the dunes. First, the creation of them, at points where,
from changes in the currents or other causes, new encroachments of the
sea are threatened; second, the maintenance and protection of them where
they have been naturally formed; and third, the removal of the inner
rows where the belt is so broad that no danger is to be apprehended from
the loss of them.
_Artificial Formation of Dunes._
In describing the natural formation of dunes, it was said that they
began with an accumulation of sand around some vegetable or other
accidental obstruction to the drifting of the particles. A high,
perpendicular cliff, which deadens the wind altogether, prevents all
accumulation of sand; but, up to a certain point, the higher and broader
the obstruction, the more sand will heap up in front of it, and the more
will that which falls behind it be protected from drifting farther. This
familiar observation has taught the inhabitants of the coast that an
artificial wall or dike will, in many situations, give rise to a broad
belt of dunes. Thus a sand dike or wall, of three or four miles in
length, thrown in 1610 across the Koegras, a tide-washed flat between
the Zuiderzee and the North Sea, has occasioned the formation of rows of
dunes a mile in breadth, and thus excluded the sea altogether from the
Koegras. A similar dike, called the Zijperzeedijk, has produced another
scarcely less extensive belt in the course of two centuries.
A few years since, the sea was threatening to cut through the island of
Ameland, and, by encroachment on the southern side and the blowing off
of the sand from a low flat which connected the two higher parts of the
island, it had made such progress, that in heavy storms the waves
sometimes rolled quite across the isthmus. The construction of a
breakwater and a sand dike have already checked the advance of the sea,
and a large number of sand hills has been formed, the rapid growth of
which promises complete future security against both wind and wave.
Similar effects have been produced by the erection of plank fences, and
even of simple screens of wattling and reeds.[457]
_Protection of Dunes._
The dunes of Holland are sometimes protected from the dashing of the
waves by a _revêtement_ of stone, or by piles; and the lateral
high-water currents, which wash away their base, are occasionally
checked by transverse walls running from the foot of the dunes to
low-water mark; but the great expense of such constructions has
prevented their adoption on a large scale.[458] The principal means
relied on for the protection of the sand hills are the planting of their
surfaces and the exclusion of burrowing and grazing animals. There are
grasses, creeping plants, and shrubs of spontaneous growth, which
flourish in loose sand, and, if protected, spread over considerable
tracts, and finally convert their face into a soil capable of
cultivation, or, at least, of producing forest trees. Krause enumerates
one hundred and seventy-one plants as native to the coast sands of
Prussia, and the observations of Andresen in Jutland carry the number of
these vegetables up to two hundred and thirty-four.
Some of these plants, especially the _Arundo arenaria_ or _arenosa_, or
_Psamma_ or _Psammophila arenaria_--Klittetag, or Hjelme in Danish, helm
in Dutch, Dünenhalm, Sandschilf, or Hügelrohr in German, gourbet in
French, and marram in English--are exclusively confined to sandy soils,
and thrive well only in a saline atmosphere.[459] The arundo grows to
the height of about twenty-four inches, but sends its strong roots with
their many rootlets to a distance of forty or fifty feet. It has the
peculiar property of nourishing best in the loosest soil, and a sand
shower seems to refresh it as the rain revives the thirsty plants of the
common earth. Its roots bind together the dunes, and its leaves protect
their surface. When the sand ceases to drift, the arundo dies, its
decaying roots fertilizing the sand, and the decomposition of its leaves
forming a layer of vegetable earth over it. Then follows a succession of
other plants which gradually fit the sand hills, by growth and decay,
for forest planting, for pasturage, and sometimes for ordinary
agricultural use.
But the protection and gradual transformation of the dunes is not the
only service rendered by this valuable plant. Its leaves are nutritious
food for sheep and cattle, its seeds for poultry;[460] cordage and
netting twine are manufactured from its fibres, it makes a good material
for thatching, and its dried roots furnish excellent fuel. These useful
qualities, unfortunately, are too often prejudicial to its growth. The
peasants feed it down with their cattle, cut it for rope making, or dig
it up for fuel, and it has been found necessary to resort to severe
legislation to prevent them from bringing ruin upon themselves by thus
improvidently sacrificing their most effectual safeguard against the
drifting of the sands.[461]
In 1539, a decree of Christian III, king of Denmark, imposed a fine upon
persons convicted of destroying certain species of sand plants upon the
west coast of Jutland. This ordinance was renewed and made more
comprehensive in 1558, and in 1569 the inhabitants of several districts
were required, by royal rescript, to do their best to check the sand
drifts, though the specific measures to be adopted for that purpose are
not indicated. Various laws against stripping the dunes of their
vegetation were enacted in the following century, but no active measures
were taken for the subjugation of the sand drifts until 1779, when a
preliminary system of operation for that purpose was adopted. This
consisted in little more than the planting of the _Arundo arenaria_ and
other sand plants, and the exclusion of animals destructive to these
vegetables.[462] Ten years later, plantations of forest trees, which
have since proved so valuable a means of fixing the dunes and rendering
them productive, were commenced, and have been continued ever
since.[463] During this latter period, Brémontier, without any knowledge
of what was doing in Denmark, experimented upon the cultivation of
forest trees on the dunes of Gascony, and perfected a system, which,
with some improvements in matters of detail, is still largely pursued
on those shores. The example of Denmark was soon followed in the
neighboring kingdom of Prussia, and in the Netherlands; and, as we shall
see hereafter, these improvements have been everywhere crowned with most
flattering success.
Under the administration of Reventlov, a little before the close of the
last century, the Danish Government organized a regular system of
improvement in the economy of the dunes. They were planted with the
arundo and other vegetables of similar habits, protected against
trespassers, and at last partly covered with forest trees. By these
means much waste soil has been converted into arable ground, a large
growth of valuable timber obtained, and the further spread of the
drifts, which threatened to lay waste the whole peninsula of Jutland, to
a considerable extent arrested.
In France, the operations for fixing and reclaiming the dunes--which
began under the direction of Brémontier about the same time as in
Denmark, and which are, in principle and in many of their details,
similar to those employed in the latter kingdom--have been conducted on
a far larger scale, and with greater success, than in any other country.
This is partly owing to a climate more favorable to the growth of
suitable forest trees than that of Northern Europe, and partly to the
liberality of the Government, which, having more important landed
interests to protect, has put larger means at the disposal of the
engineers than Denmark and Prussia have found it convenient to
appropriate to that purpose. The area of the dunes already secured from
drifting, and planted by the processes invented by Brémontier and
perfected by his successors, is about 100,000 acres.[464] This amount of
productive soil, then, has been added to the resources of France, and a
still greater quantity of valuable land has been thereby rescued from
the otherwise certain destruction with which it was threatened by the
advance of the rolling sand hills.
The improvements of the dunes on the coast of West Prussia began in
1795, under Sören Björn, a native of Denmark, and, with the exception of
the ten years between 1807 and 1817, they have been prosecuted ever
since. The methods do not differ essentially from those employed in
Denmark and France, though they are modified by local circumstances,
and, with respect to the trees selected for planting, by climate. In
1850, between the mouth of the Vistula and Kahlberg, 6,300 acres,
including about 1,900 acres planted with pines and birches, had been
secured from drifting; between Kahlberg and the eastern boundary of
West-Prussia, 8,000 acres; and important preliminary operations had been
carried on for subduing the dunes on the west coast.[465]
_Trees suited to Dune Plantations._
The tree which has been found to thrive best upon the sand hills of the
French coast, and at the same time to confine the sand most firmly and
yield the largest pecuniary returns, is the maritime pine, _Pinus
maritima_, a species valuable both for its timber and for its resinous
products. It is always grown from seed, and the young shoots require to
be protected for several seasons, by the branches of other trees,
planted in rows, or spread over the surface and staked down, by the
growth of the _Arundo arenaria_ and other small sand plants, or by
wattled hedges. The beach, from which the sand is derived, has been
generally planted with the arundo, because the pine does not thrive well
so near the sea; but it is thought that a species of tamarisk is likely
to succeed in that latitude even better than the arundo. The shade and
the protection offered by the branching top of this pine are favorable
to the growth of deciduous trees, and, while still young, of shrubs and
smaller plants, which contribute more rapidly to the formation of
vegetable mould, and thus, when the pine has once taken root, the
redemption of the waste is considered as effectually secured.
In France, the maritime pine is planted on the sands of the interior as
well as on the dunes of the sea coast, and with equal advantage. This
tree resembles the pitch pine of the Southern American States in its
habits, and is applied to the same uses. The extraction of turpentine
from it begins at the age of about twenty years, or when it has attained
a diameter of from nine to twelve inches. Incisions are made up and down
the trunk, to the depth of about half an inch in the wood, and it is
insisted that if not more than two such slits are cut, the tree is not
sensibly injured by the process. The growth, indeed, is somewhat
checked, but the wood becomes superior to that of trees from which the
turpentine is not extracted. Thus treated, the pine continues to
flourish to the age of one hundred or one hundred and twenty years, and
up to this age the trees on a hectare yield annually 350 kilogrammes of
essence of turpentine, and 280 kilogrammes of resin, worth together 110
francs. The expense of extraction and distillation is calculated at 44
francs, and a clear profit of 66 francs per hectare, or more than five
dollars per acre, is left.[466] This is exclusive of the value of the
timber, when finally cut, which, of course, amounts to a very
considerable sum.
In Denmark, where the climate is much colder, hardier conifers, as well
as the birch and other northern trees, are found to answer a better
purpose than the maritime pine, and it is doubtful whether this tree
would be able to resist the winter on the dunes of Massachusetts.
Probably the pitch pine of the Northern States, in conjunction with some
of the American oaks, birches, and poplars, and especially the robinia
or locust, would prove very suitable to be employed on the sand hills of
Cape Cod and Long Island. The ailanthus, now coming into notice as a
sand-loving tree, may, perhaps, serve a better purpose than any of them.
_Extent of Dunes in Europe._
The dunes of Denmark, as we have seen, cover an area of two hundred and
sixty square miles, or one hundred and sixty-six thousand acres; those
of the Prussian coast are vaguely estimated at from eighty-five to one
hundred and ten thousand acres; those of Holland at one hundred and
forty thousand acres;[467] those of Gascony at about three hundred
thousand acres.[468] I do not find any estimate of their extent in other
provinces of France, in the duchies of Schleswig and Holstein, or in the
Baltic provinces of Russia, but it is probable that the entire quantity
of dune land upon the eastern shores of the Atlantic and the Baltic does
not fall much short of a million of acres.[469] This vast deposit of sea
sand extends along the coast for a distance of several hundred miles,
and from the time of the destruction of the forests which covered it, to
the year 1789, the whole line was rolling inward and burying the soil
beneath it, or rendering the fields unproductive by the sand which
drifted from it. At the same time, as the sand hills moved eastward, the
ocean was closely following their retreat and swallowing up the ground
they had covered, as fast as their movement left it bare.
Planting the dunes has completely prevented the surface sands from
blowing over the soil to the leeward of the plantations, and though it
has not, in all cases, arrested the encroachments of the sea, it has so
greatly retarded the rapidity of their advance, that sandy coasts, when
once covered with forests, may be considered as substantially secure, so
long as proper measures are taken for the protection of the woods.
_Dune Vineyards of Cap Breton._
In the vicinity of Cap Breton in France, a peculiar process is
successfully employed, both for preventing the drifting of dunes, and
for rendering the sands themselves immediately productive; but this
method is applicable only in exceptional cases of favorable climate and
exposure. It consists in planting vineyards upon the dunes, and
protecting them by hedges of broom, _Erica scoparia_, so disposed as to
form rectangles about thirty feet by forty. The vines planted in these
enclosures thrive admirably, and the grapes produced by them are among
the best grown in France. The dunes are so far from being an unfavorable
soil for the vine, that fresh sea-sand is regularly employed as a
fertilizer for it, alternating every other season with ordinary manure.
The quantity of sand thus applied every second year, raises the surface
of the vineyard about four or five inches. The vines are cut down every
year to three or four shoots, and the raising of the soil rapidly
covers the old stocks. As fast as buried, they send out new roots near
the surface, and thus the vineyard is constantly renewed, and has always
a youthful appearance, though it may have been already planted a couple
of generations. This practice is ascertained to have been followed for
two centuries, and is among the oldest well-authenticated attempts of
man to resist and vanquish the dunes.[470]
_Removal of Dunes._
The artificial removal of dunes, no longer necessary as a protection,
does not appear to have been practised upon a large scale except in the
Netherlands, where the numerous canals furnish an easy and economical
means of transporting the sand, and where the construction and
maintenance of sea and river dikes, and of causeways and other
embankments and fillings, create a great demand for that material. Sand
is also employed in Holland, in large quantities, for improving the
consistence of the tough clay bordering upon or underlying diluvial
deposits, and for forming an artificial soil for the growth of certain
garden and ornamental vegetables. When the dunes are removed, the ground
they covered is restored to the domain of industry; and the quantity of
land, recovered in the Netherlands by the removal of the barren sands
which encumbered it, amounts to hundreds and perhaps thousands of
acres.[471]
_Inland Sand Plains._
The inland sand plains of Europe are either derived from the drifting of
dunes or other beach sands, or consist of diluvial deposits. As we have
seen, when once the interior of a dune is laid open to the wind, its
contents are soon scattered far and wide over the adjacent country, and
the beach sands, no longer checked by the rampart which nature had
constrained them to build against their own encroachments, are also
carried to considerable distances from the coast. Few regions have
suffered so much from this cause in proportion to their extent, as the
peninsula of Jutland. So long as the woods, with which nature had
planted the Danish dunes, were spared, they seem to have been
stationary, and we have no historical evidence, of an earlier date than
the sixteenth century, that they had become in any way injurious. From
that period, there are frequent notices of the invasions of cultivated
grounds by the sands; and excavations are constantly bringing to light
proof of human habitation and of agricultural industry, in former ages,
on soils now buried beneath deep drifts from the dunes and beaches of
the sea coast.[472]
Extensive tracts of valuable plain land in the Netherlands and in France
have been covered in the same way with a layer of sand deep enough to
render them infertile, and they can be restored to cultivation only by
processes analogous to those employed for fixing and improving the
dunes.[473] Diluvial sand plains, also, have been reclaimed by these
methods in the Duchy of Austria, between Vienna and the Semmering ridge,
in Jutland, and in the great champaign country of Northern Germany,
especially the Mark Brandenburg, where artificial forests can be
propagated with great ease, and where, consequently, this branch of
industry has been pursued on a great scale, and with highly beneficial
results, both as respects the supply of forest products and the
preparation of the soil for agricultural use.
As a general rule, inland sands are looser, dryer, and more inclined to
drift, than those of the sea coast, where the moist and saline
atmosphere of the ocean keeps them always more or less humid and
cohesive. No shore dunes are so movable as the medanos of Peru described
in a passage quoted from Pöppig on a former page, or as the sand hills
of Poland, both of which seem better entitled to the appellation of sand
waves than those of the Sahara or of the Arabian desert. The sands of
the valley of the Lower Euphrates--themselves probably of submarine
origin, and not derived from dunes--are advancing to the northwest with
a rapidity which seems fabulous when compared with the slow movement of
the sand hills of Gascony and the Low German coasts. Loftus, speaking of
Niliyya, an old Arab town a few miles east of the ruins of Babylon, says
that, "in 1848, the sand began to accumulate around it, and in six
years, the desert, within a radius of six miles, was covered with
little, undulating domes, while the ruins of the city were so buried
that it is now impossible to trace their original form or extent."[474]
Loftus considers this sand flood as the "vanguard of those vast drifts
which, advancing from the southeast, threaten eventually to overwhelm
Babylon and Baghdad."
An observation of Layard, cited by Loftus, appears to me to furnish a
possible explanation of this irruption. He "passed two or three places
where the sand, issuing from the earth like water, is called
'Aioun-er-rummal,' sand springs." These "springs" are very probably
merely the drifting of sand from the ancient subsoil, where the
protecting crust of aquatic deposit and vegetable earth has been broken
through, as in the case of the drift which arose from the upturning of
an oak mentioned on a former page. When the valley of the Euphrates was
regularly irrigated and cultivated, the underlying sands were bound by
moisture, alluvial slime, and vegetation; but now, that all improvement
is neglected, and the surface, no longer watered, has become parched,
powdery, and naked, a mere accidental fissure in the superficial stratum
may soon be enlarged to a wide opening, that will let loose sand enough
to overwhelm a province.
_The Landes of Gascony._
The most remarkable sand plain of France lies at the southwestern
extremity of the empire, and is generally known as the Landes, or
heaths, of Gascony. Clavé thus describes it: "Composed of pure sand,
resting on an impermeable stratum called _alios_, the soil of the Landes
was, for centuries, considered incapable of cultivation. Parched in
summer, drowned in winter, it produced only ferns, rushes, and heath,
and scarcely furnished pasturage for a few half-starved flocks. To crown
its miseries, this plain was continually threatened by the encroachments
of the dunes. Vast ridges of sand, thrown up by the waves, for a
distance of more than fifty leagues along the coast, and continually
renewed, were driven inland by the west wind, and, as they rolled over
the plain, they buried the soil and the hamlets, overcame all
resistance, and advanced with fearful regularity. The whole province
seemed devoted to certain destruction, when Brémontier invented his
method of fixing the dunes by plantations of the maritime pine."[475]
Although the Landes had been almost abandoned for ages, they show
numerous traces of ancient cultivation and prosperity, and it is
principally by means of the encroachments of the sands that they have
become reduced to their present desolate condition. The destruction of
the coast towns and harbors, which furnished markets for the products of
the plains, the damming up of the rivers, and the obstruction of the
smaller channels of natural drainage by the advance of the dunes, were
no doubt very influential causes; and if we add the drifting of the sea
sand over the soil, we have at least a partial explanation of the
decayed agriculture and diminished population of this great waste. When
the dunes were once arrested, and the soil to the east of them was felt
to be secure against invasion by them, experiments, in the way of
agricultural improvement, by drainage and plantation, were commenced,
and they have been attended with such signal success, that the complete
recovery of one of the dreariest and most extensive wastes in Europe may
be considered as both a probable and a near event.[476]
_The Belgian Campine._
In the northern part of Belgium, and extending across the confines of
Holland, is another very similar heath plain, called the Campine. This
is a vast sand flat, interspersed with marshes and inland dunes, and,
until recently, considered wholly incapable of cultivation. Enormous
sums have been expended in reclaiming it by draining and other familiar
agricultural processes, but without results at all proportional to the
capital invested. In 1849, the unimproved portion of the Campine was
estimated at little less than three hundred and fifty thousand acres.
The example of France has prompted experiments in the planting of trees,
especially the maritime pine, upon this barren waste, and the results
have been such as to show that its sands may both be fixed and made
productive, not only without loss, but with positive pecuniary
advantage.[477]
_Sands and Steppes of Eastern Europe._
There are still unsubdued sand wastes in many parts of interior Europe
not familiarly known to tourists or even geographers. "Olkuez and
Schiewier in Poland," says Naumann, "lie in true sand deserts, and a
boundless plain of sand stretches around Ozenstockau, on which there
grows neither tree nor shrub. In heavy winds, this plain resembles a
rolling sea, and the sand hills rise and disappear like the waves of the
ocean. The heaps of waste from the Olkuez mines are covered with sand to
the depth of four fathoms."[478] No attempts have yet been made to
subdue the sands of Poland, but when peace and prosperity shall be
restored to that unhappy country, there is no reasonable doubt that the
measures, which have proved so successful on similar formations in
Germany, may be employed with advantage in the Polish deserts.
There are sand drifts in parts of the steppes of Russia, but in general
the soil of those vast plains is of a different, though very varied,
composition, and is covered with vegetation. The steppes, however, have
many points of analogy with the sand plains of Northern Germany, and if
they are ever fitted for civilized occupation, it must be by the same
means, that is, by planting forests. It is disputed whether the steppes
were ever wooded. They were certainly bare of forest growth at a very
remote period; for Herodotus describes the country of the Scythians
between the Ister and the Tanais as woodless, with the exception of the
small province of Xylæa between the Dnieper and the Gulf of Perekop.
They are known to have been occupied by a large nomade and pastoral
population down to the sixteenth century, though these tribes are now
much reduced in numbers. The habits of such races are scarcely less
destructive to the forest than those of civilized life. Pastoral tribes
do not employ much wood for fuel or for construction, but they
carelessly or recklessly burn down the forests, and their cattle
effectually check the growth of young trees wherever their range
extends.
At present, the furious winds which sweep over the plains, the droughts
of summer, and the rights and abuses of pasturage, constitute very
formidable obstacles to the employment of measures which have been
attended with so valuable results on the sand wastes of France and
Germany. The Russian Government has, however, attempted the wooding of
the steppes, and there are thriving plantations in the neighborhood of
Odessa, where the soil is of a particularly loose and sandy
character.[479] The trees best suited to this locality, and, as there is
good reason to suppose, to sand plains in general, is the _Ailanthus
glandulosa_, or Japan varnish tree.[480] The remarkable success which
has crowned the experiments with the ailanthus at Odessa, will, no
doubt, stimulate to similar trials elsewhere, and it seems not
improbable that the arundo and the maritime pine, which have fixed so
many thousand acres of drifting sands in Western Europe, will be,
partially at least, superseded by the tamarisk and the varnish tree.
_Advantages of Reclaiming the Sands._
If we consider the quantity of waste land which has been made productive
by the planting of the sand hills and plains, and the extent of fertile
soil, the number of villages and other human improvements, and the value
of the harbors, which the same process has saved from being buried under
the rolling dunes, and at last swallowed up forever by the invasions of
the sea, we shall be inclined to rank Brémontier and Reventlov among the
greatest benefactors of their race. With the exception of the dikes of
the Netherlands, their labors are the first deliberate and direct
attempts of man to make himself, on a great scale, a geographical power,
to restore natural balances which earlier generations had disturbed, and
to atone, by acts guided by foreseeing and settled purpose, for the
waste which thoughtless improvidence had created.
_Government Works._
There is an important political difference between these latter works
and the diking system of the Netherlandish and German coasts. The dikes
originally were, and in modern times very generally have been, private
enterprises, undertaken with no other aim than to add a certain quantity
of cultivable soil to the former possessions of their proprietor, or
sometimes of the state. In short, with few exceptions, they have been
merely a pecuniary investment, a mode of acquiring land not economically
different from purchase. The planting of the dunes, on the contrary, has
always been a public work, executed, not with the expectation of reaping
a regular direct percentage of income from the expenditure, but dictated
by higher views of state economy--by the same governmental principles,
in fact, which animate all commonwealths in repelling invasion by
hostile armies, or in repairing the damages that invading forces may
have inflicted on the general interests of the people. The restoration
of the forests in the southern part of France, as now conducted by the
Government of that empire, is a measure of the same elevated character
as the fixing of the dunes. In former ages, forests were formed or
protected simply for the sake of the shelter they afforded to game, or
for the timber they yielded; but the recent legislation of France, and
of some other Continental countries, on this subject, looks to more
distant as well as nobler ends, and these are among the public acts
which most strongly encourage the hope that the rulers of Christendom
are coming better to understand the true duties and interests of
civilized government.
CHAPTER VI.
PROJECTED OR POSSIBLE GEOGRAPHICAL CHANGES BY MAN.
CUTTING OF MARINE ISTHMUSES--THE SUEZ CANAL--CANAL ACROSS ISTHMUS OF
DARIEN--CANALS TO THE DEAD SEA--MARITIME CANALS IN GREECE--CANAL OF
SAROS--CAPE COD CANAL--DIVERSION OF THE NILE--CHANGES IN THE CASPIAN--
IMPROVEMENTS IN NORTH AMERICAN HYDROGRAPHY--DIVERSION OF RHINE--
DRAINING OF THE ZUIDERZEE--WATERS OF THE KARST--SUBTERRANEAN WATERS
OF GREECE--SOIL BELOW ROCK--COVERING ROCKS WITH EARTH--WADIES OF ARABIA
PETRÆA--INCIDENTAL EFFECTS OF HUMAN ACTION--RESISTANCE TO GREAT NATURAL
FORCES--EFFECTS OF MINING--ESPY'S THEORIES--RIVER SEDIMENT--NOTHING
SMALL IN NATURE.
_Cutting of Marine Isthmuses._
Besides the great enterprises of physical transformation of which I have
already spoken, other works of internal improvement or change have been
projected in ancient and modern times, the execution of which would
produce considerable, and, in some cases, extremely important,
revolutions in the face of the earth. Some of the schemes to which I
refer are evidently chimerical; others are difficult, indeed, but cannot
be said to be impracticable, though discouraged by the apprehension of
disastrous consequences from the disturbance of existing natural or
artificial arrangements; and there are still others, the accomplishment
of which is ultimately certain, though for the present forbidden by
economical considerations.
When we consider the number of narrow necks or isthmuses which separate
gulfs and bays of the sea from each other, or from the main ocean, and
take into account the time and cost, and risks of navigation which
would be saved by executing channels to connect such waters, and thus
avoiding the necessity of doubling long capes and promontories, or even
continents, it seems strange that more of the enterprise and money which
have been so lavishly expended in forming artificial rivers for internal
navigation should not have been bestowed upon the construction of
maritime canals. Many such have been projected in early and in recent
ages, and some trifling cuts between marine waters have been actually
made, but no work of this sort, possessing real geographical or even
commercial importance, has yet been effected.
These enterprises are attended with difficulties and open to objections,
which are not, at first sight, obvious. Nature guards well the chains by
which she connects promontories with mainlands, and binds continents
together. Isthmuses are usually composed of adamantine rock or of
shifting sands--the latter being much the more refractory material to
deal with. In all such works there is a necessity for deep excavation
below low-water mark--always a matter of great difficulty; the
dimensions of channels for sea-going ships must be much greater than
those of canals of inland navigation; the height of the masts or smoke
pipes of that class of vessels would often render bridging impossible,
and thus a ship canal might obstruct a communication more important than
that which it was intended to promote; the securing of the entrances of
marine canals and the construction of ports at their termini would in
general be difficult and expensive, and the harbors and the channel
which connected them would be extremely liable to fill up by deposits
washed in from sea and shore. Besides all this, there is, in many cases,
an alarming uncertainty as to the effects of joining together waters
which nature has put asunder. A new channel may deflect strong currents
from safe courses, and thus occasion destructive erosion of shores
otherwise secure, or promote the transportation of sand or slime to
block up important harbors, or it may furnish a powerful enemy with
dangerous facilities for hostile operations along the coast.
Nature sometimes mocks the cunning and the power of man by spontaneously
performing, for his benefit, works which he shrinks from undertaking,
and the execution of which by him she would resist with unconquerable
obstinacy. A dangerous sand bank, that all the enginery of the world
could not dredge out in a generation, may be carried off in a night by a
strong river flood, or a current impelled by a violent wind from an
unusual quarter, and a passage scarcely navigable by fishing boats may
be thus converted into a commodious channel for the largest ship that
floats upon the ocean. In the remarkable gulf of Liimfjord in Jutland,
nature has given a singular example of a canal which she alternately
opens as a marine strait, and, by shutting again, converts into a
fresh-water lagoon. The Liimfjord was doubtless originally an open
channel from the Atlantic to the Baltic between two islands, but the
sand washed up by the sea blocked up the western entrance, and built a
wall of dunes to close it more firmly. This natural dike, as we have
seen, has been more than once broken through, and it is perhaps in the
power of man, either permanently to maintain the barrier, or to remove
it and keep a navigable channel constantly open. If the Liimfjord
becomes an open strait, the washing of sea sand through it would perhaps
block up some of the belts and small channels now important for the
navigation of the Baltic, and the direct introduction of a tidal current
might produce very perceptible effects on the hydrography of the
Cattegat.
_The Suez Canal._
If the Suez Canal--the greatest and most truly cosmopolite physical
improvement ever undertaken by man--shall prove successful, it will
considerably affect the basins of the Mediterranean and of the Red Sea,
though in a different manner, and probably in a less degree than the
diversion of the current of the Nile from the one to the other--to which
I shall presently refer--would do. It is, indeed, conceivable, that if a
free channel be once cut from sea to sea, the coincidence of a high tide
and a heavy south wind might produce a hydraulic force that would
convert the narrow canal into an open strait. In such a case, it is
impossible to estimate, or even to foresee, the consequences which might
result from the unobstructed mingling of the flowing and ebbing currents
of the Red Sea with the almost tideless waters of the Mediterranean.
There can be no doubt, however, that they would be of a most important
character as respects the simply geographical features and the organic
life of both. But the shallowness of the two seas at the termini of the
canal, the action of the tides of the one and the currents of the other,
and the nature of the intervening isthmus, render the occurrence of such
a cataclysm in the highest degree improbable. The obstruction of the
canal by sea sand at both ends is a danger far more difficult to guard
against and avert, than an irruption of the waters of either sea.
There is, then, no reason to expect any change of coast lines or of
natural navigable channels as a direct consequence of the opening of the
Suez Canal, but it will, no doubt, produce very interesting revolutions
in the animal and vegetable population of both basins. The
Mediterranean, with some local exceptions--such as the bays of
Calabria, and the coast of Sicily so picturesquely described by
Quatrefages[481]--is comparatively poor in marine vegetation, and in
shell as well as in fin fish. The scarcity of fish in some of its gulfs
is proverbial, and you may scrutinize long stretches of beach on its
northern shores, after every south wind for a whole winter, without
finding a dozen shells to reward your search. But no one who has not
looked down into tropical or subtropical seas can conceive the amazing
wealth of the Red Sea in organic life. Its bottom is carpeted or paved
with marine plants, with zoophytes and with shells, while its waters are
teeming with infinitely varied forms of moving life. Most of its
vegetables and its animals, no doubt, are confined by the laws of their
organization to warmer temperatures than that of the Mediterranean, but
among them there must be many, whose habitat is of a wider range, many
whose powers of accommodation would enable them to acclimate themselves
in a colder sea.
We may suppose the less numerous aquatic fauna and flora of the
Mediterranean to be equally capable of climatic adaptation, and hence,
when the canal shall be opened, there will be an interchange of the
organic population not already common to both seas. Destructive species,
thus newly introduced, may diminish the numbers of their proper prey in
either basin, and, on the other hand, the increased supply of
appropriate food may greatly multiply the abundance of others, and at
the same time add important contributions to the aliment of man in the
countries bordering on the Mediterranean.
A collateral feature of this great project deserves notice as possessing
no inconsiderable geographical importance. I refer to the conduit or
conduits constructed from the Nile to the isthmus, primarily to supply
fresh water to the laborers on the great canal, and ultimately to serve
as aqueducts for the city of Suez, and for the irrigation and
reclamation of a large extent of desert soil. In the flourishing days of
the Egyptian empire, the waters of the Nile were carried over important
districts east of the river. In later ages, most of this territory
relapsed into a desert, from the decay of the canals which once
fertilized it. There is no difficulty in restoring the ancient channels,
or in constructing new, and thus watering not only all the soil that the
wisdom of the Pharaohs had improved, but much additional land. Hundreds
of square miles of arid sand waste would thus be converted into fields
of perennial verdure, and the geography of Lower Egypt would be thereby
sensibly changed. If the canal succeeds, considerable towns will grow up
at once at both ends of the channel, and at intermediate points, all
depending on the maintenance of aqueducts from the Nile, both for water
and for the irrigation of the neighboring fields which are to supply
them with bread. Important interests will thus be created, which will
secure the permanence of the hydraulic works and of the geographical
changes produced by them, and Suez, or Port Said, or the city at Lake
Timsah, may become the capital of the government which has been so long
established at Cairo.
_Canal across the Isthmus of Darien._
The most colossal project of canalization ever suggested, whether we
consider the physical difficulties of its execution, the magnitude and
importance of the waters proposed to be united, or the distance which
would be saved in navigation, is that of a channel between the Gulf of
Mexico and the Pacific, across the Isthmus of Darien. I do not now speak
of a lock canal, by way of the Lake of Nicaragua or any other route--for
such a work would not differ essentially from other canals, and would
scarcely possess a geographical character--but of an open cut between
the two seas. It has been by no means shown that the construction of
such a channel is possible, and, if it were opened, it is highly
probable that sand bars would accumulate at both entrances, so as to
obstruct any powerful current through it. But if we suppose the work to
be actually accomplished, there would be, in the first place, such a
mixture of the animal and vegetable life of the two great oceans as I
have stated to be likely to result from the opening of the Suez Canal
between two much smaller basins. In the next place, if the channel were
not obstructed by sand bars, it might sooner or later be greatly widened
and deepened by the mechanical action of the current through it, and
consequences, not inferior in magnitude to any physical revolution which
has taken place since man appeared upon the earth, might result from it.
What those consequences would be is in a great degree matter of pure
conjecture, and there is much room for the exercise of the imagination
on the subject; but, as more than one geographer has suggested, there is
one possible result which throws all other conceivable effects of such a
work quite into the shade. I refer to changes in the course of the two
great oceanic rivers, the Gulf Stream and the corresponding current on
the Pacific side of the isthmus. The warm waters which the Gulf Stream
transports to high latitudes and then spreads out, like an expanded
hand, along the eastern shores of the Atlantic, give out, as they cool,
heat enough to raise the mean temperature of Western Europe several
degrees. In fact, the Gulf Stream is the principal cause of the
superiority of the climate of Western Europe over those of Eastern
America and Eastern Asia in the corresponding latitudes. All the
meteorological conditions of the former region are in a great measure
regulated by it, and hence it is the grandest and most beneficent of all
purely geographical phenomena. We do not yet know enough of the laws
which govern the movements of this mighty flood of warmth and life to be
able to say whether its current would be perceptibly affected by the
severance of the Isthmus of Darien; but as it enters and sweeps round
the Gulf of Mexico, it is possible that the removal of the resistance of
the land which forms the western shore of that sea, might allow the
stream to maintain its original westward direction, and join itself to
the tropical current of the Pacific.
The effect of such a change would be an immediate depression of the mean
temperature of Western Europe to the level of that of Eastern America,
and perhaps the climate of the former continent might become as
excessive as that of the latter, or even a new "ice period" be
occasioned by the withdrawal of so important a source of warmth from the
northern zones. Hence would result the extinction of vast multitudes of
land and sea plants and animals, and a total revolution in the domestic
and rural economy of human life in all those countries from which the
New World has received its civilized population. Other scarcely less
startling consequences may be imagined as possible; but the whole
speculation is too dreary, distant, and improbable to deserve to be long
indulged in.[482]
_Canals to the Dead Sea._
The project of Captain Allen for opening a new route to India by cuts
between the Mediterranean and the Dead Sea, and between the Dead Sea and
the Red Sea, presents many interesting considerations.[483] The
hypsometrical observations of Bertou, Roth, and others, render it highly
probable, if not certain, that the watershed in the Wadi-el-Araba
between the Dead Sea and the Red Sea is not less than three hundred feet
above the mean level of the latter, and if this is so, the execution of
a canal from the one sea to the other is quite out of the question. But
the summit level between the Mediterranean and the Jordan, near Jezreel,
is believed to be little, if at all, more than one hundred feet above
the sea, and the distance is so short that the cutting of a channel
through the dividing ridge would probably be found by no means an
impracticable undertaking. Although, therefore, we have no reason to
believe it possible to open a navigable channel to the east by way of
the Dead Sea, there is not much doubt that the basin of the latter might
be made accessible from the Mediterranean.
The level of the Dead Sea lies 1,316.7 feet below that of the ocean. It
is bounded east and west by mountain ridges, rising to the height of
from 2,000 to 4,000 feet above the ocean. From its southern end, a
depression called the Wadi-el-Araba extends to the Gulf of Akaba, the
eastern arm of the Red Sea. The Jordan empties into its northern
extremity, after having passed through the Lake of Tiberias at an
elevation of 663.4 feet above the Dead Sea, or 653.3 below the
Mediterranean, and drains a considerable valley north of the lake, as
well as the plain of Jericho, which lies between the lake and the sea.
If the waters of the Mediterranean were admitted freely into the basin
of the Dead Sea, they would raise its surface to the general level of
the ocean, and consequently flood all the dry land below that level
within the basin.
I do not know that accurate levels have been taken in the valley of the
Jordan above the Lake of Tiberias, and our information is very vague as
to the hypsometry of the northern part of the Wadi-el-Araba. As little
do we know where a contour line, carried around the basin at the level
of the Mediterranean, would strike its eastern and western borders. We
cannot, therefore, accurately compute the extent of now dry land which
would be covered by the admission of the waters of the Mediterranean, or
the area of the inland sea which would be thus created. Its length,
however, would certainly exceed one hundred and fifty miles, and its
mean breadth, including its gulfs and bays, could scarcely be less than
fifteen, perhaps even twenty. It would cover very little ground now
occupied by civilized or even uncivilized man, though some of the soil
which would be submerged--for instance, that watered by the Fountain of
Elisha and other neighboring sources--is of great fertility, and, under
a wiser government and better civil institutions, might rise to
importance, because, from its depression, it possesses a very warm
climate, and might supply Southeastern Europe with tropical products
more readily than they can be obtained from any other source. Such a
canal and sea would be of no present commercial importance, because they
would give access to no new markets or sources of supply; but when the
fertile valleys and the deserted plains east of the Jordan shall be
reclaimed to agriculture and civilization, these waters would furnish a
channel of communication which might become the medium of a very
extensive trade.
Whatever might be the economical results of the opening and filling of
the Dead Sea basin, the creation of a new evaporable area, adding not
less than 2,000 or perhaps 3,000 square miles to the present fluid
surface of Syria, could not fail to produce important meteorological
effects. The climate of Syria would be tempered, its precipitation and
its fertility increased, the courses of its winds and the electrical
condition of its atmosphere modified. The present organic life of the
valley would be extinguished, and many tribes of plants and animals
would emigrate from the Mediterranean to the new home which human art
had prepared for them. It is possible, too, that the addition of 1,300
feet, or forty atmospheres, of hydrostatic pressure upon the bottom of
the basin might disturb the equilibrium between the internal and the
external forces of the crust of the earth at this point of abnormal
configuration, and thus produce geological convulsions the intensity of
which cannot be even conjectured.
_Maritime Canals in Greece._
A maritime canal executed and another projected in ancient times, the
latter of which is again beginning to excite attention, deserve some
notice, though their importance is of a commercial rather than a
geographical character. The first of these is the cut made by Xerxes
through the rock which connects the promontory of Mount Athos with the
mainland; the other, a navigable canal through the Isthmus of Corinth.
In spite of the testimony of Herodotus and Thucydides, the Romans
classed the canal of Xerxes among the fables of "mendacious Greece," and
yet traces of it are perfectly distinct at the present day through its
whole extent, except at a single point where, after it had become so
choked as to be no longer navigable, it was probably filled up to
facilitate communication by land between the promontory and the country
in the rear of it.
If the fancy kingdom of Greece shall ever become a sober reality, escape
from its tutelage and acquire such a moral as well as political status
that its own capitalists--who now prefer to establish themselves and
employ their funds anywhere else rather than in their native land--have
any confidence in the permanency of its institutions, a navigable
channel will no doubt be opened between the gulfs of Lepanto and Ægina.
The annexation of the Ionian Islands to Greece will make such a work
almost a political necessity, and it would not only furnish valuable
facilities for domestic intercourse, but become an important channel of
communication between the Levant and the countries bordering on the
Adriatic, or conducting their trade through that sea.
As I have said, the importance of this latter canal and of a navigable
channel between Mount Athos and the continent would be chiefly
commercial, but both of them would be conspicuous instances of the
control of man over nature in a field where he has thus far done little
to interfere with her spontaneous arrangements. If they were constructed
upon such a scale as to admit of the free passage of the water through
them, in either direction, as the prevailing winds should impel it, they
would exercise a certain influence on the coast currents, which are
important as hydrographical elements, and also as producing abrasion of
the coast and a drift at the bottom of seas, and hence would be entitled
to a higher rank than simply as artificial means of transit.
_Canal of Saros._
It has been thought practicable to cut a canal across the peninsula of
Gallipoli from the outlet of the Sea of Marmora into the Gulf of Saros.
It may be doubted whether the mechanical difficulties of such a work
would not be found insuperable; but when Constantinople shall recover
the important political and commercial rank which naturally belongs to
her, the execution of such a canal will be recommended by strong reasons
of military expediency, as well as by the interests of trade. An open
channel across the peninsula would divert a portion of the water which
now flows through the Dardanelles, diminish the rapidity of that
powerful current, and thus in part remove the difficulties which
obstruct the navigation of the strait. It would considerably abridge the
distance by water between Constantinople and the northern coast of the
Ægean, and it would have the important advantage of obliging an enemy to
maintain two blockading fleets instead of one.
_Cape Cod Canal._
The opening of a navigable cut through the narrow neck which separates
the southern part of Cape Cod Bay in Massachusetts from the Atlantic,
was long ago suggested, and there are few coast improvements on the
Atlantic shores of the United States which are recommended by higher
considerations of utility. It would save the most important coasting
trade of the United States the long and dangerous navigation around Cape
Cod, afford a new and safer entrance to Boston harbor for vessels from
Southern ports, secure a choice of passages, thus permitting arrivals
upon the coast and departures from it at periods when wind and weather
might otherwise prevent them, and furnish a most valuable internal
communication in case of coast blockade by a foreign power. The
difficulties of the undertaking are no doubt formidable, but the expense
of maintenance and the uncertainty of the effects of currents setting
through the new strait are still more serious objections.
_Diversion of the Nile._
Perhaps the most remarkable project of great physical change, proposed
or threatened in earlier ages, is that of the diversion of the Nile from
its natural channel, and the turning of its current into either the
Libyan desert or the Red Sea. The Ethiopian or Abyssinian princes more
than once menaced the Memlouk sultans with the execution of this
alarming project, and the fear of so serious an evil is said to have
induced the Moslems to conciliate the Abyssinian kings by large
presents, and by some concessions to the oppressed Christians of
Egypt.[484] Indeed, Arabic historians affirm that in the tenth century
the Ethiopians dammed the river, and, for a whole year, cut off its
waters from Egypt. The probable explanation of this story is to be found
in a season of extreme drought, such as have sometimes occurred in the
valley of the Nile. About the beginning of the sixteenth century,
Albuquerque the "Terrible" revived the scheme of turning the Nile into
the Red Sea, with the hope of destroying the transit trade through Egypt
by way of Kesseir. In 1525 the King of Portugal was requested by the
Emperor of Abyssinia to send him engineers for that purpose; a successor
of that prince threatened to attempt the project about the year 1700,
and even as late as the French occupation of Egypt, the possibility of
driving out the intruder by this means was suggested in England.
It cannot be positively affirmed that the diversion of the waters of the
Nile to the Red Sea is impossible. In the chain of mountains which
separates the two valleys, Brown found a deep depression or wadi,
extending from the one to the other, at no great elevation above the bed
of the river. The Libyan desert is so much higher than the Nile below
the junction of the two principal branches at Khartum, that there is no
reason to believe a new channel for their united waters could be found
in that direction; but the Bahr-el-Abiad flows through, if it does not
rise in, a great table land, and some of its tributaries are supposed to
communicate in the rainy season with branches of great rivers flowing in
quite another direction. Hence it is probable that a portion at least of
the waters of this great arm of the Nile--and perhaps a quantity the
abstraction of which would be sensibly felt in Egypt--might be sent to
the Atlantic by the Niger, lost in the inland lakes of Central Africa,
or employed to fertilize the Libyan sand wastes.
Admitting the possibility of turning the whole river into the Red Sea,
let us consider the probable effect of the change. First and most
obvious is the total destruction of the fertility of Middle and Lower
Egypt, the conversion of that part of the valley into a desert, and the
extinction of its imperfect civilization, if not the absolute
extirpation of its inhabitants. This is the calamity threatened by the
Abyssinian princes and the ferocious Portuguese warrior, and feared by
the sultans of Egypt. Beyond these immediate and palpable consequences
neither party then looked; but a far wider geographical area, and far
more extensive and various human interests, would be affected by the
measure. The spread of the Nile during the annual inundation covers, for
many weeks, several thousand square miles with water, and at other
seasons of the year pervades the same and even a larger area with
moisture by infiltration. The abstraction of so large an evaporable
surface from the southern shores of the Mediterranean could not but
produce important effects on many meteorological phenomena, and the
humidity, the temperature, the electrical condition and the atmospheric
currents of Northeastern Africa might be modified to a degree that would
sensibly affect the climate of Europe.
The Mediterranean, deprived of the contributions of the Nile, would
require a larger supply, and of course a stronger current, of water from
the Atlantic through the Straits of Gibraltar; the proportion of salt it
contains would be increased, and the animal life of at least its
southern borders would be consequently modified; the current which winds
along its southern, eastern, and northeastern shores would be diminished
in force and volume, if not destroyed altogether, and its basin and its
harbors would be shoaled by no new deposits from the highlands of inner
Africa.
In the much smaller Red Sea, more immediately perceptible, if not
greater, effects, would be produced. The deposits of slime would reduce
its depth, and perhaps, in the course of ages, divide it into an inland
and an open sea; its waters would be more or less freshened, and its
immensely rich marine fauna and flora changed in character and
proportion, and, near the mouth of the river, perhaps even destroyed
altogether; its navigable channels would be altered in position and
often quite obstructed; the flow of its tides would be modified by the
new geographical conditions; the sediment of the river would form new
coast lines and lowlands, which would be covered with vegetation, and
probably thereby produce sensible climatic changes.
_Changes in the Caspian._
The Russian Government has contemplated the establishment of a nearly
direct water communication between the Caspian Sea and the Sea of Azoff,
partly by natural and partly by artificial channels, and there are now
navigable canals between the Don and the Volga; but these works, though
not wanting in commercial and political interest, do not possess any
geographical importance. It is, however, very possible to produce
appreciable geographical changes in the basin of the Caspian by the
diversion of the great rivers which flow from Central Russia. The
surface of the Caspian is eighty-three feet below the level of the Sea
of Azoff, and its depression has been explained upon the hypothesis that
the evaporation exceeds the supply derived, directly and indirectly,
from precipitation, though able physicists now maintain that the sinking
of this sea is due to a subsidence of its bottom from geological causes.
At Tsaritsin, the Don, which empties into the Sea of Azoff, and the
Volga, which pours into the Caspian, approach each other within ten
miles. Near this point, by means of open or subterranean canals, the Don
might be turned into the Volga, or the Volga into the Don. If we suppose
the whole or a large proportion of the waters of the Don to be thus
diverted from their natural outlet and sent down to the Caspian, the
equilibrium between the evaporation from that sea and its supply of
water might be restored, or its level even raised above its ancient
limits. If the Volga were turned into the Sea of Azoff, the Caspian
would be reduced in dimensions until the balance between loss and gain
should be reëstablished, and it would occupy a much smaller area than at
present. Such changes in the proportion of solid and fluid surface would
have some climatic effects in the territory which drains into the
Caspian, and on the other hand, the introduction of a greater quantity
of fresh water into the Sea of Azoff would render that gulf less saline,
affect the character and numbers of its fish, and perhaps be not wholly
without sensible influence on the water of the Black Sea.
_Improvements in North American Hydrography._
We are not yet well enough acquainted with the geography of Central
Africa, or of the interior of South America, to conjecture what
hydrographical revolutions might there be wrought; but from the fact
that many important rivers in both continents drain extensive table
lands, of very moderate inclination, there is reason to suppose that
important changes in the course of rivers might be accomplished. Our
knowledge of the drainage of North America is much more complete, and it
is certain that there are numerous points where the courses of great
rivers, or the discharge of considerable lakes, might be completely
diverted, or at least partially directed into different channels.
The surface of Lake Erie is 565 feet above that of the Hudson at Albany,
and it is so near the level of the great plain lying east of it, that it
was found practicable to supply the western section of the canal, which
unites it with the Hudson, with water from the lake, or rather from the
Niagara which flows out of it. Hence a channel might be constructed,
which would draw off into the valley of the Genesee any desirable
proportion of the water naturally discharged by the Niagara. The
greatest depth of water yet sounded in Lake Erie is but two hundred and
seventy feet, the mean depth one hundred and twenty. Open canals
parallel with the Niagara, or directly toward the Genesee, might be
executed upon a scale which would exercise an important influence on the
drainage of the lake, if there were any adequate motive for such an
undertaking. Still easier would it be to create additional outlets for
the waters of Lake Superior at the Saut St. Mary--where the river which
drains the lake descends twenty-two feet in a single mile--and thus
produce incalculable effects, both upon that lake and upon the great
chain of inland waters which communicate with it.
The summit level between Lake Michigan and the Des Plaines, a tributary
of the Mississippi, is only twenty-seven feet above the lake, and the
intervening distance is but a very few miles. It has often been proposed
to cut an open channel across this ridge, and there is no doubt of the
practicability of the project. Were this accomplished, although such a
cut would not, of itself, form a navigable canal, a part of the waters
of Lake Michigan would be contributed to the Gulf of Mexico, instead of
to that of St. Lawrence, and the flow might be so regulated as to keep
the Illinois and the Mississippi at flood at all seasons of the year.
The increase in the volume of these rivers would augment their velocity
and their transporting power, and consequently, the erosion of their
banks and the deposit of slime in the Gulf of Mexico, while the
introduction of a larger body of cold water into the beds of these
rivers would very probably produce a considerable effect on the animal
life that peoples them. The diversion of water from the common basin of
the great lakes through a new channel, in a direction opposite to their
natural discharge, would not be absolutely without influence on the St.
Lawrence, though probably the effect would be too small to be in any way
perceptible.
_Diversion of the Rhine._
The interference of physical improvements with vested rights and ancient
arrangements, is a more formidable obstacle in old countries than in
new, to enterprises involving anything approaching to a geographical
revolution. Hence such projects meet with stronger opposition in Europe
than in America, and the number of probable changes in the face of
nature in the former continent is proportionally less. I have noticed
some important hydraulic improvements as already executed or in progress
in Europe, and I may refer to some others as contemplated or suggested.
One of these is the diversion of the Rhine from its present channel
below Ragatz, by a cut through the narrow ridge near Sargans, and the
consequent turning of its current into the Lake of Wallenstadt. This
would be an extremely easy undertaking, for the ridge is but twenty
feet above the level of the Rhine, and hardly two hundred yards wide.
There is no present adequate motive for this diversion, but it is easy
to suppose that it may become advisable within no long period. The
navigation of the Lake of Constance is rapidly increasing in importance,
and the shoaling of the eastern end of that lake by the deposits of the
Rhine may require a remedy which can be found by no other so ready means
as the discharge of that river into the Lake of Wallenstadt. The
navigation of this latter lake is not important, nor is it ever likely
to become so, because the rocky and precipitous character of its shores
renders their cultivation impossible. It is of great depth, and its
basin is capacious enough to receive and retain all the sediment which
the Rhine would carry into it for thousands of years.
_Draining of the Zuiderzee._
I have referred to the draining of the Lake of Haarlem as an operation
of great geographical as well as economical and mechanical interest. A
much more gigantic project, of a similar character, is now engaging the
attention of the Netherlandish engineers. It is proposed to drain the
great salt-water basin called the Zuiderzee. This inland sea covers an
area of not less than two thousand square miles, or about one million
three hundred thousand acres. The seaward half, or that portion lying
northwest of a line drawn from Enkhuizen to Stavoren, is believed to
have been converted from a marsh to an open bay since the fifth century
after Christ, and this change is ascribed, partly if not wholly, to the
interference of man with the order of nature. The Zuiderzee communicates
with the sea by at least six considerable channels, separated from each
other by low islands, and the tide rises within the basin to the height
of three feet. To drain the Zuiderzee, these channels must first be
closed and the passage of the tidal flood through them cut off. If this
be done, the coast currents will be restored approximately to the lines
they followed fourteen or fifteen centuries ago, and there can be little
doubt that an appreciable effect will thus be produced upon all the
tidal phenomena of that coast, and, of course, upon the maritime
geography of Holland.
A ring dike and canal must then be constructed around the landward side
of the basin, to exclude and carry off the fresh-water streams which now
empty into it. One of these, the Ijssel, a considerable river, has a
course of eighty miles, and is, in fact, one of the outlets of the
Rhine, though augmented by the waters of several independent
tributaries. These preparations being made, and perhaps transverse dikes
erected at convenient points for dividing the gulf into smaller
portions, the water must be pumped out by machinery, in substantially
the same way as in the case of the Lake of Haarlem. No safe calculations
can be made as to the expenditure of time and money required for the
execution of this stupendous enterprise, but I believe its
practicability is not denied by competent judges, though doubts are
entertained as to its financial expediency. The geographical results of
this improvement would be analogous to those of the draining of the Lake
of Haarlem, but many times multiplied in extent, and its meteorological
effects, though perhaps not perceptible on the coast, could hardly fail
to be appreciable in the interior of Holland.
_Waters of the Karst._
The singular structure of the Karst, the great limestone plateau lying
to the north of Trieste, has suggested some engineering operations which
might be attended with sensible effects upon the geography of the
province. I have described this table land as, though now bare of
forests, and almost of vegetation, having once been covered with woods,
and as being completely honeycombed by caves through which the drainage
of that region is conducted. Schmidl has spent years in studying the
subterranean geography and hydrography of this singular district, and
his discoveries, and those of earlier cave-hunters, have led to various
proposals of physical improvement of a novel character. Many of the
underground water courses of the Karst are without visible outlet, and,
in some instances at least, they, no doubt, send their waters, by deep
channels, to the Adriatic.[485] The city of Trieste is very
insufficiently provided with fresh water. It has been thought
practicable to supply this want by tunnelling through the wall of the
plateau, which rises abruptly in the rear of the town, until some
subterranean stream is encountered, the current of which can be
conducted to the city. More visionary projectors have gone further, and
imagined that advantage might be taken of the natural tunnels under the
Karst for the passage of roads, railways, and even navigable canals. But
however chimerical these latter schemes may seem, there is every reason
to believe that art might avail itself of these galleries for improving
the imperfect drainage of the champaign country bounded by the Karst,
and that stopping or opening the natural channels might very much modify
the hydrography of an extensive region.
_Subterranean Waters of Greece._
There are parts of continental Greece which resemble the Karst and the
adjacent plains in being provided with a natural subterranean drainage.
The superfluous waters run off into limestone caves called _catavothra_
([Greek: katabothra]). In ancient times, the entrances to the catavothra
were enlarged or partially closed as the convenience of drainage or
irrigation required, and there is no doubt that similar measures might
be adopted at the present day with great advantage both to the salubrity
and the productiveness of the regions so drained.
_Soil below Rock._
One of the most singular changes of natural surface effected by man is
that observed by Beechey and by Barth at Lîn Tefla, and near Gebel
Genûnes, in the district of Ben Gâsi, in Northern Africa. In this region
the superficial stratum originally consisted of a thin sheet of rock
covering a layer of fertile earth. This rock has been broken up, and,
when not practicable to find use for it in fences, fortresses, or
dwellings, heaped together in high piles, and the soil, thus bared of
its stony shell, has been employed for agricultural purposes.[486] If we
remember that gunpowder was unknown at the period when these remarkable
improvements were executed, and of course that the rock could have been
broken only with the chisel and wedge, we must infer that land had at
that time a very great pecuniary value, and, of course, that the
province, though now exhausted, and almost entirely deserted by man, had
once a dense population.
_Covering Rock with Earth._
If man has, in some cases, broken up rock to reach productive ground
beneath, he has, in many other instances, covered bare ledges, and
sometimes extensive surfaces of solid stone, with fruitful earth,
brought from no inconsiderable distance. Not to speak of the Campo Santo
at Pisa, filled, or at least coated, with earth from the Holy Land, for
quite a different purpose, it is affirmed that the garden of the
monastery of St. Catherine at Mount Sinai is composed of Nile mud,
transported on the backs of camels from the banks of that river. Parthey
and older authors state that all the productive soil of the Island of
Malta was brought over from Sicily.[487] The accuracy of the
information may be questioned in both cases, but similar practices, on a
smaller scale, are matter of daily observation in many parts of Southern
Europe. Much of the wine of the Moselle is derived from grapes grown on
earth carried high up the cliffs on the shoulders of men. In China, too,
rock has been artificially covered with earth to an extent which gives
such operations a real geographical importance, and the accounts of the
importation of earth at Malta, and the fertilization of the rocks on
Mount Sinai with slime from the Nile, may be not wholly without
foundation.
_Wadies of Arabia, Petræa._
In the latter case, indeed, river sediment might be very useful as a
manure, but it could hardly be needed as a soil; for the growth of
vegetation in the wadies of the Sinaitic Peninsula shows that the
disintegrated rock of its mountains requires only water to stimulate it
to considerable productiveness. The wadies present, not unfrequently,
narrow gorges, which might easily be closed, and thus accumulations of
earth, and reservoirs of water to irrigate it, might be formed which
would convert many a square mile of desert into flourishing date gardens
and cornfields. Not far from Wadi Feiran, on the most direct route to
Wadi Esh-Sheikh, is a very narrow pass called by the Arabs El Bueb (El
Bab) or, The Gate, which might be securely closed to a very considerable
height, with little labor or expense. Above this pass is a wide and
nearly level expanse, containing a hundred acres, perhaps much more.
This is filled up to a certain regular level with deposits brought down
by torrents before the Gate, or Bueb, was broken through, and they have
now worn down a channel in the deposits to the bed of the wadi. If a dam
were constructed at the pass, and reservoirs built to retain the winter
rains, a great extent of valley might be rendered cultivable.
_Incidental Effects of Human Action._
I have more than once alluded to the collateral and unsought
consequences of human action as being often more momentous than the
direct and desired results. There are cases where such incidental, or,
in popular speech, accidental, consequences, though of minor importance
in themselves, serve to illustrate natural processes; others, where, by
the magnitude and character of the material traces they leave behind
them, they prove that man, in primary or in more advanced stages of
social life, must have occupied particular districts for a longer period
than has been supposed by popular chronology. "On the coast of Jutland,"
says Forchhammer, "wherever a bolt from a wreck or any other fragment of
iron is deposited in the beach sand, the particles are cemented
together, and form a very solid mass around the iron. A remarkable
formation of this sort was observed a few years ago in constructing the
sea wall of the harbor of Elsineur. This stratum, which seldom exceeded
a foot in thickness, rested upon common beach sand, and was found at
various depths, less near the shore, greater at some distance from it.
It was composed of pebbles and sand, and contained a great quantity of
pins, and some coins of the reign of Christian IV, between the beginning
and the middle of the seventeenth century. Here and there, a coating of
metallic copper had been deposited by galvanic action, and the presence
of completely oxydized metallic iron was often detected. An
investigation undertaken by Councillor Reinhard and myself, at the
instance of the Society of Science, made it in the highest degree
probable that this formation owed its origin to the street sweepings of
the town, which had been thrown upon the beach, and carried off and
distributed by the waves over the bottom of the harbor."[488] These and
other familiar observations of the like sort show that a sandstone reef,
of no inconsiderable magnitude, might originate from the stranding of a
ship with a cargo of iron,[489] or from throwing the waste of an
establishment for working metals into running water which might carry it
to the sea.
Parthey records a singular instance of unforeseen mischief from an
interference with the arrangements of nature. A landowner at Malta
possessed a rocky plateau sloping gradually toward the sea, and
terminating in a precipice forty or fifty feet high, through natural
openings in which the sea water flowed into a large cave under the rock.
The proprietor attempted to establish salt works on the surface, and cut
shallow pools in the rock for the evaporation of the water. In order to
fill the salt pans more readily, he sank a well down to the cave
beneath, through which he drew up water by a windlass and buckets. The
speculation proved a failure, because the water filtered through the
porous bottom of the pans, leaving little salt behind. But this was a
small evil, compared with other destructive consequences that followed.
When the sea was driven into the cave by violent west or northwest
winds, it shot a _jet d'eau_ through the well to the height of sixty
feet, the spray of which was scattered far and wide over the neighboring
gardens and blasted the crops. The well was now closed with stones, but
the next winter's storms hurled them out again, and spread the salt
spray over the grounds in the vicinity as before. Repeated attempts were
made to stop the orifice, but at the time of Parthey's visit the sea had
thrice burst through, and it was feared that the evil was without
remedy.[490]
I have mentioned the great extent of the heaps of oyster and other
shells left by the American Indians on the Atlantic coast of the United
States. Some of the Danish kitchen-middens, which closely resemble them,
are a thousand feet long, from one hundred and fifty to two hundred
wide, and from six to ten high. These piles have an importance as
geological witnesses, independent of their bearing upon human history.
Wherever the coast line appears, from other evidence, to have remained
unchanged in outline and elevation since they were accumulated, they are
found near the sea, and not more than about ten feet above its level. In
some cases they are at a considerable distance from the beach, and in
these instances, so far as yet examined, there are proofs that the coast
has advanced in consequence of upheaval or of fluviatile or marine
deposit. Where they are altogether wanting, the coast seems to have sunk
or been washed away by the sea. The constancy of these observations
justifies geologists in arguing, where other evidence is wanting, the
advance of land or sea respectively, or the elevation or depression of
the former, from the position or the absence of these heaps alone.
Every traveller in Italy is familiar with Monte Testaccio, the mountain
of potsherds, at Rome; but this deposit, large as it is, shrinks into
insignificance when compared with masses of similar origin in the
neighborhood of older cities. The castaway pottery of ancient towns in
Magna Græcia composes strata of such extent and thickness that they have
been dignified with the appellation of the ceramic formation. The Nile,
as it slowly changes its bed, exposes in its banks masses of the same
material, so vast that the population of the world during the whole
historical period would seem to have chosen this valley as a general
deposit for its broken vessels.
The fertility imparted to the banks of the Nile by the water and the
slime of the inundations, is such that manures are little employed.
Hence much domestic waste, which would elsewhere be employed to enrich
the soil, is thrown out into vacant places near the town. Hills of
rubbish are thus piled up which astonish the traveller almost as much as
the solid pyramids themselves. The heaps of ashes and other household
refuse collected on the borders and within the limits of Cairo were so
large, that the removal of them by Ibrahim Pacha has been looked upon as
one of the great works of the age.
The soil near cities, the street sweepings of which are spread upon the
ground as manure, is perceptibly raised by them and by other effects of
human industry, and in spite of all efforts to remove the waste, the
level of the ground on which large towns stand is constantly elevated.
The present streets of Rome are twenty feet above those of the ancient
city. The Appian way between Rome and Albano, when cleared out a few
years ago, was found buried four or five feet deep, and the fields along
the road were elevated nearly or quite as much. The floors of many
churches in Italy, not more than six or seven centuries old, are now
three or four feet below the adjacent streets, though it is proved by
excavations that they were built as many feet above them.
_Resistance to Great Natural Forces._
I have often spoken of the greater and more subtile natural forces, and
especially of geological agencies, as powers beyond human guidance or
resistance. This is no doubt at present true in the main, but man has
shown that he is not altogether impotent to struggle with even these
mighty servants of nature, and his unconscious as well as his deliberate
action may in some cases have increased or diminished the intensity of
their energies. It is a very ancient belief that earthquakes are more
destructive in districts where the crust of the earth is solid and
homogeneous, than where it is of a looser and more interrupted
structure. Aristotle, Pliny the elder, and Seneca believed that not only
natural ravines and caves, but quarries, wells, and other human
excavations, which break the continuity of the terrestrial strata and
facilitate the escape of elastic vapors, have a sensible influence in
diminishing the violence and preventing the propagation of the earth
waves. In all countries subject to earthquakes this opinion is still
maintained, and it is asserted that, both in ancient and in modern
times, buildings protected by deep wells under or near them have
suffered less from earthquakes than those the architects of which have
neglected this precaution.[491]
If the commonly received theory of the cause of earthquakes is
true--that, namely, which ascribes them to the elastic force of gases
accumulated or generated in subterranean reservoirs--it is evident that
open channels of communication between such reservoirs and the
atmosphere might serve as a harmless discharge of gases that would
otherwise acquire destructive energy. The doubt is whether artificial
excavations can be carried deep enough to reach the laboratory where the
elastic fluids are distilled. There are, in many places, small natural
crevices through which such fluids escape, and the source of them
sometimes lies at so moderate a depth that they pervade the superficial
soil and, as it were, transpire from it, over a considerable area. When
the borer of an ordinary artesian well strikes into a cavity in the
earth, imprisoned air often rushes out with great violence, and this has
been still more frequently observed in sinking mineral-oil wells. In
this latter case, the discharge of a vehement current of inflammable
fluid sometimes continues for hours and even longer periods. These facts
seem to render it not wholly improbable that the popular belief of the
efficacy of deep wells in mitigating the violence of earthquakes is well
founded.
In general, light, wooden buildings are less injured by earthquakes than
more solid structures of stone or brick, and it is commonly supposed
that the power put forth by the earth wave is too great to be resisted
by any amount of weight or solidity of mass that man can pile up upon
the surface. But the fact that in countries subject to earthquakes many
very large and strongly constructed palaces, temples, and other
monuments have stood for centuries, comparatively uninjured, suggests a
doubt whether this opinion is sound. The earthquake of the first of
November, 1755, which was felt over a twelfth part of the earth's
surface, was probably the most violent of which we have any clear and
distinct account, and it seems to have exerted its most destructive
force at Lisbon. It has often been noticed as a remarkable fact, that
the mint, a building of great solidity, was almost wholly unaffected by
the shock which shattered every house and church in the city, and its
escape from the common ruin can hardly be accounted for except upon the
supposition that its weight, compactness, and strength of material
enabled it to resist an agitation of the earth which overthrew all
weaker structures. On the other hand, a stone pier in the harbor of
Lisbon, on which thousands of people had taken refuge, sank with its
foundations to a great depth during the same earthquake; and it is plain
that where subterranean cavities exist, at moderate depths, the erection
of heavy masses upon them would tend to promote the breaking down of the
strata which roof them over.
No physicist, I believe, has supposed that man can avert the eruption of
a volcano or diminish the quantity of melted rock which it pours out of
the bowels of the earth; but it is not always impossible to divert the
course of even a large current of lava. "The smaller streams of lava
near Catania," says Ferrara, in describing the great eruption of 1669,
"were turned from their course by building dry walls of stone as a
barrier against them. * * * It was proposed to divert the main current
from Catania, and fifty men, protected by hides, were sent with hooks
and iron bars to break the flank of the stream near Belpasso.[492] When
the opening was made, fluid lava poured forth and flowed rapidly toward
Paterno; but the inhabitants of that place, not caring to sacrifice
their own town to save Catania, rushed out in arms and put a stop to the
operation."[493] In the eruption of Vesuvius in 1794, the viceroy saved
from impending destruction the town of Portici, and the valuable
collection of antiquities then deposited there but since removed to
Naples, by employing several thousand men to dig a ditch above the town,
by which the lava current was carried off in another direction.[494]
_Effects of Mining._
The excavations made by man, for mining and other purposes, may
sometimes occasion disturbance of the surface by the subsidence of the
strata above them, as in the case of the mine of Fahlun, but such
accidents must always be too inconsiderable in extent to deserve notice
in a geographical point of view. Such excavations, however, may
interfere materially with the course of subterranean waters, and it has
even been conjectured that the removal of large bodies of metallic ore
from their original deposits might, at least locally, affect the
magnetic and electrical condition of the earth's crust to a sensible
degree.
Accidental fires in mines of coal or lignite sometimes lead to
consequences not only destructive to large quantities of valuable
material, but may, directly or indirectly, produce results important in
geography. The coal occasionally takes fire from the miners' lights or
other fires used by them, and, if long exposed to air in deserted
galleries, may be spontaneously kindled. Under favorable circumstances,
a stratum of coal will burn till it is exhausted, and a cavity may be
burnt out in a few months which human labor could not excavate in many
years. Wittwer informs us that a coal mine at St. Etienne in Dauphiny
has been burning ever since the fourteenth century, and that a mine near
Duttweiler, another near Epterode, and a third at Zwickau, have been on
fire for two hundred years. Such conflagrations not only produce
cavities in the earth, but communicate a perceptible degree of heat to
the surface, and the author just quoted cites cases where this heat has
been advantageously employed in forcing vegetation.[495]
_Espy's Theories._
Espy's well known suggestion of the possibility of causing rain
artificially, by kindling great fires, is not likely to be turned to
practical account, but the speculations of this able meteorologist are
not, for that reason, to be rejected as worthless. His labors exhibit
great industry in the collection of facts, much ingenuity in dealing
with them, remarkable insight into the laws of nature, and a ready
perception of analogies and relations not obvious to minds less
philosophically constituted. They have unquestionably contributed very
essentially to the advancement of meteorological science. The
possibility that the distribution and action of electricity may be
considerably modified by long lines of iron railways and telegraph
wires, is a kindred thought, and in fact rests much on the same
foundation as the belief in the utility of lightning rods, but such
influence is too obscure and too small to have been yet detected.
_River Sediment._
The manifestation of the internal heat of the earth at any given point
is conditioned by the thickness of the crust at such point. The deposits
of rivers tend to augment that thickness at their estuaries. The
sediment of slowly flowing rivers emptying into shallow seas is spread
over so great a surface that we can hardly imagine the foot or two of
slime they let fall over a wide area in a century to form an element
among even the infinitesimal quantities which compose the terms of the
equations of nature. But some swift rivers, rolling mountains of fine
earth, discharge themselves into deeply scooped gulfs or bays, and in
such cases the deposit amounts, in the course of a few years, to a mass
the transfer of which from the surface of a large basin, and its
accumulation at a single point, may be supposed to produce other
effects than those measurable by the sounding line. Now, almost all the
operations of rural life, as I have abundantly shown, increase the
liability of the soil to erosion by water. Hence, the clearing of the
valley of the Ganges by man must have much augmented the quantity of
earth transported by that river to the sea, and of course have
strengthened the effects, whatever they may be, of thickening the crust
of the earth in the Bay of Bengal. In such cases, then, human action
must rank among geological influences.
_Nothing Small in Nature._
It is a legal maxim that "the law concerneth not itself with trifles,"
_de minimus non curat lex_; but in the vocabulary of nature, little and
great are terms of comparison only; she knows no trifles, and her laws
are as inflexible in dealing with an atom as with a continent or a
planet.[496] The human operations mentioned in the last few paragraphs,
therefore, do act in the ways ascribed to them, though our limited
faculties are at present, perhaps forever, incapable of weighing their
immediate, still more their ultimate consequences. But our inability to
assign definite values to these causes of the disturbance of natural
arrangements is not a reason for ignoring the existence of such causes
in any general view of the relations between man and nature, and we are
never justified in assuming a force to be insignificant because its
measure is unknown, or even because no physical effect can now be traced
to it as its origin. The collection of phenomena must precede the
analysis of them, and every new fact, illustrative of the action and
reaction between humanity and the material world around it, is another
step toward the determination of the great question, whether man is of
nature or above her.
FOOTNOTES:
[1] In the Middle Ages, feudalism, and a nominal Christianity whose
corruptions had converted the most beneficent of religions into the most
baneful of superstitions, perpetuated every abuse of Roman tyranny, and
added new oppressions and new methods of extortion to those invented by
older despotisms. The burdens in question fell most heavily on the
provinces that had been longest colonized by the Latin race, and these
are the portions of Europe which have suffered the greatest physical
degradation. "Feudalism," says Blanqui, "was a concentration of
scourges. The peasant, stripped of the inheritance of his fathers,
became the property of inflexible, ignorant, indolent masters; he was
obliged to travel fifty leagues with their carts whenever they required
it; he labored for them three days in the week, and surrendered to them
half the product of his earnings during the other three; without their
consent he could not change his residence, or marry. And why, indeed,
should he wish to marry, when he could scarcely save enough to maintain
himself? The Abbot Alcuin had twenty thousand slaves, called _serfs_,
who were forever attached to the soil. This is the great cause of the
rapid depopulation observed in the Middle Ages, and of the prodigious
multitude of monasteries which sprang up on every side. It was doubtless
a relief to such miserable men to find in the cloisters a retreat from
oppression; but the human race never suffered a more cruel outrage,
industry never received a wound better calculated to plunge the world
again into the darkness of the rudest antiquity. It suffices to say that
the prediction of the approaching end of the world, industriously spread
by the rapacious monks at this time, was received without
terror."--_Résumé de l'Histoire du Commerce_, p. 156.
The abbey of Saint-Germain-des-Prés, which, in the time of Charlemagne,
had possessed a million of acres, was, down to the Revolution,
still so wealthy, that the personal income of the abbot was 300,000
livres. The abbey of Saint-Denis was nearly as rich as that of
Saint-Germain-des-Prés.--LAVERGNE, _Économie Rurale de la France_,
p. 104.
Paul Louis Courier quotes from La Bruyère the following striking picture
of the condition of the French peasantry in his time: "One sees certain
dark, livid, naked, sunburnt, wild animals, male and female, scattered
over the country and attached to the soil, which they root and turn over
with indomitable perseverance. They have, as it were, an articulate
voice, and when they rise to their feet, they show a human face. They
are, in fact, men; they creep at night into dens, where they live on
black bread, water, and roots. They spare other men the labor of
ploughing, sowing, and harvesting, and therefore deserve some small
share of the bread they have grown." "These are his own words," adds
Courier; "he is speaking of the fortunate peasants, of those who had
work and bread, and they were then the few."--_Pétition à la Chambre des
Députís pour les Villageois que l'on empêche de danser._
Arthur Young, who travelled in France from 1787 to 1789, gives, in the
twenty-first chapter of his Travels, a frightful account of the burdens
of the rural population even at that late period. Besides the regular
governmental taxes, and a multitude of heavy fines imposed for trifling
offences, he enumerates about thirty seignorial rights, the very origin
and nature of some of which are now unknown, while those of some others,
claimed and enforced by ecclesiastical as well as by temporal lords, are
as repulsive to humanity and morality, as the worst abuses ever
practised by heathen despotism. Most of these, indeed, had been commuted
for money payments, and were levied on the peasantry as pecuniary
imposts for the benefit of prelates and lay lords, who, by virtue of
their nobility, were exempt from taxation. Who can wonder at the
hostility of the French plebeian classes toward the aristocracy in the
days of the Revolution?
[2] The temporary depopulation of an exhausted soil may be, in some
cases, a physical, though, like fallows in agriculture, a dear-bought
advantage. Under favorable circumstances, the withdrawal of man and his
flocks allows the earth to clothe itself again with forests, and in a
few generations to recover its ancient productiveness. In the Middle
Ages, worn-out fields were depopulated, in many parts of the Continent,
by civil and ecclesiastical tyrannies, which insisted on the surrender
of the half of a loaf already too small to sustain its producer. Thus
abandoned, these lands often relapsed into the forest state, and, some
centuries later, were again brought under cultivation with renovated
fertility.
[3] The subject of climatic change, with and without reference to human
action as a cause, has been much discussed by Moreau de Jonnes, Dureau,
de la Malle, Arago, Humboldt, Fuster, Gasparin, Becquerel, and many
other writers in Europe, and by Noah Webster, Forry, Drake, and others
in America. Fraas has endeavored to show, by the history of vegetation
in Greece, not merely that clearing and cultivation have affected
climate, but that change of climate has essentially modified the
character of vegetable life. See his _Klima und Pflanzenwelt in der
Zeit_.
[4]
Gods Almagt wenkte van den troon,
En schiep elk volk een land ter woon:
Hier vestte Zij een grondgebied,
Dat Zij ons zelven scheppen liet.
[5] The udometric measurements of Belgrand, reported in the _Annales
Forestières_ for 1854, and discussed by Vallès in chap. vi of his
_Études sur les Inondations_, constitute the earliest, and, in some
respects, the most remarkable series known to me, of persevering and
systematic observations bearing directly and exclusively upon the
influence of human action on climate, or, to speak more accurately,
on precipitation and natural drainage. The conclusions of Belgrand,
however, and of Vallès, who adopts them, have not been generally
accepted by the scientific world, and they seem to have been, in part
at least, refuted by the arguments of Héricourt and the observations
of Cantegril, Jeandel, and Belland. See chapter iii: _The Woods_.
[6] Verses addressed by G. C. to Sir Walter Raleigh.--HAKLUYT, i, p.
668.
[7]
----I troer, at Synets Sands er lagt i Öiet,
Mens dette kun er Redskab. Synet strömmer
Fra Sjælens Dyb, og Öiets fine Nerver
Gaae ud fra Hjernens hemmelige Værksted.
HENRIK HERTZ, _Kong René's Datter_, sc. ii.
In the material eye, you think, sight lodgeth!
The _eye_ is but an organ. _Seeing_ streameth
From the soul's inmost depths. The fine perceptive
Nerve springeth from the brain's mysterious workshop.
[8] Skill in marksmanship, whether with firearms or with other
projectile weapons, depends more upon the training of the eye than is
generally supposed, and I have often found particularly good shots to
possess an almost telescopic vision. In the ordinary use of the rifle,
the barrel serves as a guide to the eye, but there are sportsmen who
fire with the but of the gun at the hip. In this case, as in the use of
the sling, the lasso, and the bolas, in hurling the knife (see BABINET,
_Lectures_, vii, p. 84), in throwing the boomerang, the javelin, or a
stone, and in the employment of the blow pipe and the bow, the movements
of the hand and arm are guided by that mysterious sympathy which exists
between the eye and the unseeing organs of the body.
In shooting the tortoises of the Amazon and its tributaries, the Indians
use an arrow with a long twine and a float attached to it. Avé-Lallemant
(_Die Benutzung der Palmen am Amazonenstrom_, p. 32) thus describes
their mode of aiming: "As the arrow, if aimed directly at the floating
tortoise, would strike it at a small angle, and glance from its flat and
wet shell, the archers have a peculiar method of shooting. They are able
to calculate exactly their own muscular effort, the velocity of the
stream, the distance and size of the tortoise, and they shoot the arrow
directly up into the air, so that it falls almost vertically upon the
shell of the tortoise, and sticks in it." Analogous calculations--if
such physico-mental operations can properly be so called--are made in
the use of other missiles; for no projectile flies in a right line to
its mark. But the exact training of the eye lies at the bottom of all of
them, and marksmanship depends almost wholly upon the power of that
organ, whose directions the blind muscles implicitly follow. It is
perhaps not out of place to observe here that our English word aim comes
from the Latin æstimo, I calculate or estimate. See WEDGWOOD'S
_Dictionary of English Etymology_, and the note to the American edition,
under _Aim_.
Another proof of the control of the limbs by the eye has been observed
in deaf-and-dumb schools, and others where pupils are first taught to
write on large slates or blackboards. The writing is in large
characters, the small letters being an inch or more high. They are
formed with chalk or a slate pencil firmly grasped in the fingers, and
by appropriate motions of the wrist, elbow, and shoulder, not of the
finger joints. Nevertheless, when a pen is put into the hand of a pupil
thus taught, his handwriting, though produced by a totally different set
of muscles and muscular movements, is identical in character with that
which he has practised on the blackboard.
It has been much doubted whether the artists of the classic ages
possessed a more perfect sight than those of modern times, or whether,
in executing their minute mosaics and gem engravings, they used
magnifiers. Glasses ground convex have been found at Pompeii, but they
are too rudely fashioned and too imperfectly polished to have been of
any practical use for optical purposes. But though the ancient artists
may have had a microscopic vision, their astronomers cannot have had a
telescopic power of sight; for they did not discover the satellites of
Jupiter, which are often seen with the naked eye at Oormeeah, in Persia,
and sometimes, as I can testify by personal observation, at Cairo.
For a very remarkable account of the restoration of vision impaired from
age, by judicious training, see _Lessons in Life_, by TIMOTHY TITCOMB,
lesson xi.
[9] _Antiquity of Man_, p. 377.
[10] "One of them [the Indians] seated himself near me, and made from a
fragment of quartz, with a simple piece of round bone, one end of which
was hemispherical, with a small crease in it (as if worn by a thread)
the sixteenth of an inch deep, an arrow head which was very sharp and
piercing, and such as they use on all their arrows. The skill and
rapidity with which it was made, without a blow, but by simply breaking
the sharp edges with the creased bone by the strength of his hands--for
the crease merely served to prevent the instrument from slipping,
affording no leverage--was remarkable."--_Reports of Explorations and
Surveys for Pacific Railroad_, vol. ii, 1855, _Lieut._ BECKWITH'S
_Report_, p. 43.
It has been said that stone weapons are not found in Sicily, except in
certain caves half filled with the skeletons of extinct animals. If they
have not been found in that island in more easily accessible localities,
I suspect it is because eyes familiar with such objects have not sought
for them. In January, 1854, I picked up an arrow head of quartz in a
little ravine or furrow just washed out by a heavy rain, in a field near
the Simeto. It is rudely fashioned, but its artificial character and its
special purpose are quite unequivocal.
[11] Probably no cultivated vegetable affords so good an opportunity of
studying the laws of acclimation of plants as maize or Indian corn.
Maize is grown from the tropics to at least lat. 47° in Northeastern
America, and farther north in Europe. Every two or three degrees of
latitude brings you to a new variety, with new climatic adaptations, and
the capacity of the plant to accommodate itself to new conditions of
temperature and season seems almost unlimited. We may easily suppose a
variety of this grain, which had become acclimated in still higher
latitudes, to have been lost, and in such case the failure to raise a
crop from seed brought from some distance to the south would not prove
that the climate had become colder.
Many persons now living remember that, when the common tomato was first
introduced into Northern New England, it often failed to ripen; but, in
the course of a very few years, it completely adapted itself to the
climate, and now not only matures both its fruit and its seeds with as
much certainty as any cultivated vegetable, but regularly propagates
itself by self-sown seed. Meteorological observations, however, do not
show any amelioration of the summer climate in those States within that
period. See _Appendix_, No. 1.
Maize and the tomato, if not new to human use, have not been long known
to civilization, and were, very probably, reclaimed and domesticated at
a much more recent period than the plants which form the great staples
of agricultural husbandry in Europe and Asia. Is the great power of
accomodation to climate possessed by them due to this circumstance?
There is some reason to suppose that the character of maize has been
sensibly changed by cultivation in South America; for, according to
Pöppig, the ears of this grain found in old Peruvian tombs belong to
varieties not now known in Peru.--_Travels in Peru_, chap. vii.
[12] The cultivation of madder is said to have been introduced into
Europe by an Oriental in the year 1765, and it was first planted in the
neighborhood of Avignon. Of course, it has been grown in that district
for less than a century; but upon soils where it has been a frequent
crop, it is already losing much of its coloring properties.--LAVERGNE,
_Économie Rurale de la France_, pp. 259-291.
I believe there is no doubt that the cultivation of madder in the
vicinity of Avignon is of recent introduction; but it appears from
Fuller and other evidence, that this plant was grown in Europe before
the middle of the seventeenth century. The madder brought to France from
Persia may be of a different species, or, at least, variety. "Some two
years since," says Fuller, "madder was sown by Sir Nicholas Crispe at
Debtford, and I hope will have good success; first because it groweth in
Zeland in the same (if not a more _northern_) _latitude_. Secondly,
because _wild madder_ grows here in abundance; and why may not _tame
madder_ if _cicurated_ by art. Lastly, because as good as any grew some
thirty years since at Barn-Elms, in Surrey, though it quit not cost
through some error in the first planter thereof, which now we hope will
be rectified."--FULLER, _Worthies of England_, ii, pp. 57, 58.
Perhaps the recent diseases of the olive, the vine, and the
silkworm--the prevailing malady of which insect is supposed by some to
be the effect of an incipient decay of the mulberry tree--may be, in
part, due to changes produced in the character of the soil by exhaustion
through long cultivation.
[13] In many parts of New England there are tracts, miles in extent, and
presenting all varieties of surface and exposure, which were partially
cleared sixty or seventy years ago, and where little or no change in the
proportion of cultivated ground, pasturage, and woodland has taken place
since. In some cases, these tracts compose basins apparently scarcely at
all exposed to any local influence in the way of percolation or
infiltration of water toward or from neighboring valleys. But in such
situations, apart from accidental disturbances, the ground is growing
drier and drier, from year to year, springs are still disappearing, and
rivulets still diminishing in their summer supply of water. A probable
explanation of this is to be found in the rapid drainage of the surface
of cleared ground, which prevents the subterranean natural reservoirs,
whether cavities or merely strata of bibulous earth, from filling up.
How long this process is to last before an equilibrium is reached, none
can say. It may be, for years; it may be, for centuries.
Livingstone states facts which favor the supposition that a secular
desiccation is still going on in central Africa. When the regions where
the earth is growing drier were cleared of wood, or, indeed, whether
forests ever grew there, we are unable to say, but the change appears to
have been long in progress. There is reason to suspect a similar
revolution in Arabia Petræa. In many of the wadis, and particularly in
the gorges between Wadi Feiran and Wadi Esh Sheikh, there are water-worn
banks showing that, at no very remote period, the winter floods must
have risen fifty feet in channels where the growth of acacias and
tamarisks and the testimony of the Arabs concur to prove that they have
not risen six feet within the memory or tradition of the present
inhabitants. There is little probability that any considerable part of
the Sinaitic peninsula has been wooded since its first occupation by
man, and we must seek the cause of its increasing dryness elsewhere than
in the removal of the forest.
[14] The soil of newly subdued countries is generally in a high degree
favorable to the growth of the fruits of the garden and the orchard, but
usually becomes much less so in a very few years. Plums, of many
varieties, were formerly grown, in great perfection and abundance, in
many parts of New England where at present they can scarcely be reared
at all; and the peach, which, a generation or two ago, succeeded
admirably in the southern portion of the same States, has almost ceased
to be cultivated there. The disappearance of these fruits is partly due
to the ravages of insects, which have in later years attacked them; but
this is evidently by no means the sole, or even the principal cause of
their decay. In these cases, it is not to the exhaustion of the
particular acres on which the fruit trees have grown that we are to
ascribe their degeneracy, but to a general change in the condition of
the soil or the air; for it is equally impossible to rear them
successfully on absolutely new land in the neighborhood of grounds
where, not long since, they bore the finest fruit.
I remember being told, many years ago, by one of the earliest settlers
of the State of Ohio, a very intelligent and observing person, that the
apple trees raised there from seed sown soon after the land was cleared,
bore fruit in less than half the time required to bring to bearing those
reared from seed sown when the ground had been twenty years under
cultivation.
In the peat mosses of Denmark, Scotch firs and other trees not now
growing in the same localities, are found in abundance. Every generation
of trees leaves the soil in a different state from that in which it
found it; every tree that springs up in a group of trees of another
species than its own, grows under different influences of light and
shade and atmosphere from its predecessors. Hence the succession of
crops, which occurs in all natural forests, seems to be due rather to
changes of condition than of climate. See chapter iii, _post_.
[15] The nomenclature of meteorology is vague and sometimes equivocal.
Not long since, it was suspected that the observers reporting to a
scientific institution did not agree in their understanding of the mode
of expressing the direction of the wind prescribed by their
instructions. It was found, upon inquiry, that very many of them used
the names of the compass-points to indicate the quarter _from_ which the
wind blew, while others employed them to signify the quarter _toward_
which the atmospheric currents were moving. In some instances, the
observers were no longer within the reach of inquiry, and of course
their tables of the wind were of no value.
"Winds," says Mrs. Somerville, "are named from the points whence they
blow, currents exactly the reverse. An easterly wind comes from the
east; whereas an easterly current comes from the west, and flows toward
the east."--_Physical Geography_, p. 229.
There is no philological ground for this distinction, and it probably
originated in a confusion of the terminations _-wardly_ and _-erly_,
both of which are modern. The root of the former ending implies the
direction _to_ or _to-ward_ which motion is supposed. It corresponds to,
and is probably allied with, the Latin _versus_. The termination _-erly_
is a corruption or softening of _-ernly_, easterly for easternly, and
many authors of the seventeenth century so write it. In Hakluyt (i, p.
2), _easterly_ is applied to place, "_easterly_ bounds," and means
_eastern_. In a passage in Drayton, "_easterly_ winds" must mean winds
_from_ the east; but the same author, in speaking of nations, uses
_northerly_ for _northern_. Hakewell says: "The sonne cannot goe more
_southernely_ from vs, nor come more _northernely_ towards vs." Holland,
in his translation of Pliny, referring to the moon has: "When shee is
_northerly_," and "shee is gone _southerly_." Richardson, to whom I am
indebted for the above citations, quotes a passage from Dampier where
_westerly_ is applied to the wind, but the context does not determine
the direction. The only example of the termination in _-wardly_ given by
this lexicographer is from Donne, where it means _toward_ the west.
Shakspeare, in _Hamlet_ (v. ii), uses _northerly_ wind for wind _from_
the north. Milton does not employ either of these terminations, nor were
they known to the Anglo-Saxons, who, however, had adjectives of
direction in _-an_ or _-en_, _-ern_ and _-weard_, the last always
meaning the point _toward_ which motion is supposed, the others that
_from_ which it proceeds.
We use an _east_ wind, an _eastern_ wind, and an _easterly_ wind, to
signify the same thing. The two former expressions are old, and constant
in meaning; the last is recent, superfluous, and equivocal. See
_Appendix_, No. 2.
[16] I do not here speak of the vast prairie region of the Mississippi
valley, which cannot properly be said ever to have been a field of
British colonization; but of the original colonies, and their
dependencies in the territory of the present United States, and in
Canada. It is, however, equally true of the Western prairies as of the
Eastern forest land, that they had arrived at a state of equilibrium,
though under very different conditions.
[17] The great fire of Miramichi in 1825, probably the most extensive
and terrific conflagration recorded in authentic history, spread its
ravages over nearly six thousand square miles, chiefly of woodland, and
was of such intensity that it seemed to consume the very soil itself.
But so great are the recuperative powers of nature, that, in twenty-five
years, the ground was thickly covered again with trees of fair
dimensions, except where cultivation and pasturage kept down the forest
growth.
[18] The English nomenclature of this geographical feature does not seem
well settled. We have _bog_, _swamp_, _marsh_, _morass_,_ moor_, _fen_,
_turf moss_, _peat moss_, _quagmire_, all of which, though sometimes
more or less accurately discriminated, are often used interchangeably,
or are perhaps employed, each exclusively, in a particular district. In
Sweden, where, especially in the Lappish provinces, this terr-aqueous
formation is very extensive and important, the names of its different
kinds are more specific in their application. The general designation of
all soils permanently pervaded with water is _Kärr_. The elder Læstadius
divides the _Kärr_ into two genera: _Myror_ (sing. _myra_), and _Mossar_
(sing. _mosse_). "The former," he observes, "are grass-grown, and
overflowed with water through almost the whole summer; the latter are
covered with mosses and always moist, but very seldom overflowed." He
enumerates the following species of _Myra_, the character of which will
perhaps be sufficiently understood by the Latin terms into which he
translates the vernacular names, for the benefit of strangers not
altogether familiar with the language and the subject: 1. _Hömyror_,
paludes graminosæ. 2. _Dy_, paludes profundæ. 3. _Flarkmyror_, or proper
_kärr_, paludes limosæ. 4. _Fjällmyror_, paludes uliginosæ. 5.
_Tufmyror_, paludes cæspitosæ. 6. _Rismyror_, paludes virgatæ. 7.
_Starrängar_, prata irrigata, with their subdivisions, dry _starrängar_
or _risängar_, wet _starrängar_ and _fräkengropar_. 8. _Pölar_, laeunæ.
9. _Gölar_, fossæ inundatæ. The _Mossar_, paludes turfosæ, which are of
great extent, have but two species: 1. _Torfmossar_, called also
_Mossmyror_ and _Snottermyror_, and, 2. _Björnmossar_.
The accumulations of stagnant or stagnating water originating in bogs
are distinguished into _Tr[=a]sk_, stagna, and _Tjernar_ or _Tjärnar_
(sing. _Tjern_ or _Tjärn_), stagnatiles. _Tr[=a]sk_ are pools fed by
bogs, or water emanating from them, and their bottoms are slimy;
_Tjernar_ are small _Träsk_ situated within the limits of _Mossar_.--L.
L. LÆSTADIUS, _om Möjligheten af Uppodlingar i Lappmarken_, pp. 23, 24.
[19] Although the quantity of bog land in New England is less than in
many other regions of equal area, yet there is a considerable extent of
this formation in some of the Northeastern States. Dana (_Manual of
Geology_, p. 614) states that the quantity of peat in Massachusetts is
estimated at 120,000,000 cords, or nearly 569,000,000 cubic yards, but
he does not give either the area or the depth of the deposits. In any
event, however, bogs cover but a small percentage of the territory in
any of the Northern States, while it is said that one tenth of the whole
surface of Ireland is composed of bogs, and there are still extensive
tracts of undrained marsh in England.
Bogs, independently of their importance in geology as explaining the
origin of some kinds of mineral coal, have a present value as
repositories of fuel. Peat beds have sometimes a thickness of ten or
twelve yards, or even more. A depth of ten yards would give 48,000 cubic
yards to the acre. The greatest quantity of firewood yielded by the
forests of New England to the acre is 100 cords solid measure, or 474
cubic yards; but this comprises only the trunks and larger branches. If
we add the small branches and twigs, it is possible that 600 cubic yards
might, in some cases, be cut on an acre. This is only one eightieth part
of the quantity of peat sometimes found on the same area. It is true
that a yard of peat and a yard of wood are not the equivalents of each
other, but the fuel on an acre of deep peat is worth much more than that
on an acre of the best woodland. Besides this, wood is perishable, and
the quantity on an acre cannot be increased beyond the amount just
stated; peat is indestructible, and the beds are always growing.
[20] "Aquatic plants have a utility in raising the level of marshy
grounds, which renders them very valuable, and may well be called a
geological function. * * *
"The engineer drains ponds at a great expense by lowering the surface of
the water; nature attains the same end, gratuitously, by raising the
level of the soil without depressing that of the water; but she proceeds
more slowly. There are, in the Landes, marshes where this natural
filling has a thickness of four mètres, and some of them, at first lower
than the sea, have been thus raised and drained so as to grow summer
crops, such, for example, as maize."--BOITEL, _Mise en valeur des Terres
pauvres_, p. 227.
The bogs of Denmark--the examination of which by Steenstrup and Vaupell
has presented such curious results with respect to the natural
succession of forest trees--appear to have gone through this gradual
process of drying, and the birch, which grows freely in very wet soils,
has contributed very effectually by its annual deposits to raise the
surface above the water level, and thus to prepare the ground for the
oak.--VAUPELL, _Bögens Indvandring_, pp. 39, 40.
[21] Careful examination of the peat mosses in North Sjælland--which are
so abundant in fossil wood that, within thirty years, they have yielded
above a million of trees--shows that the trees have generally fallen
from age and not from wind. They are found in depressions on the
declivities of which they grew, and they lie with the top lowest, always
falling toward the bottom of the valley.--VAUPELL, _Bögens Indvandring i
de Danske Skove_, pp. 10, 14.
[22] The locust insect, _Clitus pictus_, which deposits its eggs in the
American locust, _Robinia pseudacacia_, is one of these, and its ravages
have been and still are most destructive to that very valuable tree, so
remarkable for combining rapidity of growth with strength and durability
of wood. This insect, I believe, has not yet appeared in Europe, where,
since the so general employment of the _Robinia_ to clothe and protect
embankments and the scarps of deep cuts on railroads, it would do
incalculable mischief. As a traveller, however, I should find some
compensation for this evil in the destruction of these acacia hedges,
which as completely obstruct the view on hundreds of miles of French and
Italian railways, as the garden walls of the same countries do on the
ordinary roads. See _Appendix_, No. 4.
[23] In the artificial woods of Europe, insects are far more numerous
and destructive to trees than in the primitive forests of America, and
the same remark may be made of the smaller rodents, such as moles, mice,
and squirrels. In the dense native wood, the ground and the air are too
humid, the depth of shade too great for many tribes of these creatures,
while near the natural meadows and other open grounds, where
circumstances are otherwise more favorable for their existence and
multiplication, their numbers are kept down by birds, serpents, foxes,
and smaller predacious quadrupeds. In civilized countries, these natural
enemies of the worm, the beetle and the mole, are persecuted, sometimes
almost exterminated, by man, who also removes from his plantations the
decayed or wind-fallen trees, the shrubs and underwood, which, in a
state of nature, furnished food and shelter to the borer and the rodent,
and often also to the animals that preyed upon them. Hence the insect
and the gnawing quadruped are allowed to increase, from the expulsion of
the police which, in the natural wood, prevent their excessive
multiplication, and they become destructive to the forest because they
are driven to the living tree for nutriment and cover. The forest of
Fontainebleau is almost wholly without birds, and their absence is
ascribed by some writers to the want of water, which, in the thirsty
sands of that wood, does not gather into running brooks; but the want of
undergrowth is perhaps an equally good reason for their scarcity. In a
wood of spontaneous growth, ordered and governed by nature, the squirrel
does not attack trees, or at least the injury he may do is too trifling
to be perceptible, but he is a formidable enemy to the plantation. "The
squirrels bite the cones of the pine and consume the seed which might
serve to restock the wood; they do still more mischief by gnawing off,
near the leading shoot, a strip of bark, and thus often completely
girdling the tree. Trees so injured must be felled, as they would never
acquire a vigorous growth. The squirrel is especially destructive to the
pine in Sologne, where he gnaws the bark of tress twenty or twenty-five
years old." But even here, nature sometimes provides a compensation, by
making the appetite of this quadruped serve to prevent an excessive
production of seed cones, which tends to obstruct the due growth of the
leading shoot. "In some of the pineries of Brittany which produce cones
so abundantly as to strangle the development of the leading shoot of the
maritime pine, it has been observed that the pines are most vigorous
where the squirrels are most numerous, a result attributed to the
repression of the cones by this rodent."--BOITEL, _Mise en valeur des
Terres pauvres_, p. 50. See _Appendix_, No. 5.
[24] The terrible destructiveness of man is remarkably exemplified in
the chase of large mammalia and birds for single products, attended with
the entire waste of enormous quantities of flesh, and of other parts of
the animal, which are capable of valuable uses. The wild cattle of South
America are slaughtered by millions for their hides and horns; the
buffalo of North America for his skin or his tongue; the elephant, the
walrus, and the narwhal for their tusks; the cetacea, and some other
marine animals, for their oil and whalebone; the ostrich and other large
birds, for their plumage. Within a few years, sheep have been killed in
New England by whole flocks, for their pelts and suet alone, the flesh
being thrown away; and it is even said that the bodies of the same
quadrupeds have been used in Australia as fuel for limekilns. What a
vast amount of human nutriment, of bone, and of other animal products
valuable in the arts, is thus recklessly squandered! In nearly all these
cases, the part which constitutes the motive for this wholesale
destruction, and is alone saved, is essentially of insignificant value
as compared with what is thrown away. The horns and hide of an ox are
not economically worth a tenth part as much as the entire carcass.
One of the greatest benefits to be expected from the improvements of
civilization is, that increased facilities of communication will render
it possible to transport to places of consumption much valuable material
that is now wasted because the price at the nearest market will not pay
freight. The cattle slaughtered in South America for their hides would
feed millions of the starving population of the Old World, if their
flesh could be economically preserved and transported across the ocean.
We are beginning to learn a better economy in dealing with the inorganic
world. The utilization--or, as the Germans more happily call it, the
Verwerthung, the _beworthing_--of waste from metallurgical, chemical,
and manufacturing establishments, is among the most important results of
the application of science to industrial purposes. The incidental
products from the laboratories of manufacturing chemists often become
more valuable than those for the preparation of which they were erected.
The slags from silver refineries, and even from smelting houses of the
coarser metals, have not unfrequently yielded to a second operator a
better return than the first had derived from dealing with the natural
ore; and the saving of lead carried off in the smoke of furnaces has, of
itself, given a large profit on the capital invested in the works. A few
years ago, an officer of an American mint was charged with embezzling
gold committed to him for coinage. He insisted, in his defence, that
much of the metal was volatilized and lost in refining and melting, and
upon scraping the chimneys of the melting furnaces and the roofs of the
adjacent houses, gold enough was found in the soot to account for no
small part of the deficiency.
[25] It is an interesting and not hitherto sufficiently noticed fact,
that the domestication of the organic world, so far as it has yet been
achieved, belongs, not indeed to the savage state, but to the earliest
dawn of civilization, the conquest of inorganic nature almost as
exclusively to the most advanced stages of artificial culture. It is
familiarly known to all who have occupied themselves with the psychology
and habits of the ruder races, and of persons with imperfectly developed
intellects in civilized life, that although these humble tribes and
individuals sacrifice, without scruple, the lives of the lower animals
to the gratification of their appetites and the supply of their other
physical wants, yet they nevertheless seem to cherish with brutes, and
even with vegetable life, sympathies which are much more feebly felt by
civilized men. The popular traditions of the simpler peoples recognize a
certain community of nature between man, brute animals, and even plants;
and this serves to explain why the apologue or fable, which ascribes the
power of speech and the faculty of reason to birds, quadrupeds, insects,
flowers, and trees, is one of the earliest forms of literary
composition.
In almost every wild tribe, some particular quadruped or bird, though
persecuted as a destroyer of more domestic beasts, or hunted for food,
is regarded with peculiar respect, one might almost say, affection. Some
of the North American aboriginal nations celebrate a propitiatory feast
to the manes of the intended victim before they commence a bear hunt;
and the Norwegian peasantry have not only retained an old proverb which
ascribes to the same animal "_ti M[oe]nds Styrke og tolv M[oe]nds Vid_,"
ten men's strength and twelve men's cunning, but they still pay to him
something of the reverence with which ancient superstition invested him.
The student of Icelandic literature will find in the saga of _Finnbogi
hinn rami_ a curious illustration of this feeling, in an account of a
dialogue between a Norwegian bear and an Icelandic champion--dumb show
on the part of Bruin, and chivalric words on that of Finnbogi--followed
by a duel, in which the latter, who had thrown away his arms and armor
in order that the combatants might meet on equal terms, was victorious.
Drummond Hay's very interesting work on Morocco contains many amusing
notices of a similar feeling entertained by the Moors toward the
redoubtable enemy of their flocks--the lion.
This sympathy helps us to understand how it is that most if not all the
domestic animals--if indeed they ever existed in a wild state--were
appropriated, reclaimed and trained before men had been gathered into
organized and fixed communities, that almost every known esculent plant
had acquired substantially its present artificial character, and that
the properties of nearly all vegetable drugs and poisons were known at
the remotest period to which historical records reach. Did nature bestow
upon primitive man some instinct akin to that by which she teaches the
brute to select the nutritious and to reject the noxious vegetables
indiscriminately mixed in forest and pasture?
This instinct, it must be admitted, is far from infallible, and, as has
been hundreds of times remarked by naturalists, it is in many cases not
an original faculty but an acquired and transmitted habit. It is a fact
familiar to persons engaged in sheep husbandry in New England--and I
have seen it confirmed by personal observation--that sheep bred where
the common laurel, as it is called, _Kalmia angustifolia_, abounds,
almost always avoid browsing upon the leaves of that plant, while those
brought from districts where laurel is unknown, and turned into pastures
where it grows, very often feed upon it and are poisoned by it. A
curious acquired and hereditary instinct, of a different character, may
not improperly be noticed here. I refer to that by which horses bred in
provinces where quicksands are common avoid their dangers or extricate
themselves from them. See BRÉMONTIER, _Mémoire sur les Dunes, Annales
des Ponts et Chaussées_, 1833: _premier sémestre_, pp. 155-157.
It is commonly said in New England, and I believe with reason, that the
crows of this generation are wiser than their ancestors. Scarecrows
which were effectual fifty years ago are no longer respected by the
plunderers of the cornfield, and new terrors must from time to time be
invented for its protection. See _Appendix_, No. 6.
Civilization has added little to the number of vegetable or animal
species grown in our fields or bred in our folds, while, on the
contrary, the subjugation of the inorganic forces, and the consequent
extension of man's sway over, not the annual products of the earth only,
but her substance and her springs of action, is almost entirely the work
of highly refined and cultivated ages. The employment of the elasticity
of wood and of horn, as a projectile power in the bow, is nearly
universal among the rudest savages. The application of compressed air to
the same purpose, in the blowpipe, is more restricted, and the use of
the mechanical powers, the inclined plane, the wheel and axle, and even
the wedge and lever, seems almost unknown except to civilized man. I
have myself seen European peasants to whom one of the simplest
applications of this latter power was a revelation.
[26] The difference between the relations of savage life, and of
incipient civilization, to nature, is well seen in that part of the
valley of the Mississippi which was once occupied by the mound builders
and afterward by the far less developed Indian tribes. When the tillers
of the fields, which must have been cultivated to sustain the large
population that once inhabited those regions perished, or were driven
out, the soil fell back to the normal forest state, and the savages who
succeeded the more advanced race interfered very little, if at all, with
the ordinary course of spontaneous nature.
[27] There is a possible--but only a possible--exception in the case of
the American bison. See note on that subject in chap. iii, _post_.
[28] Whatever may be thought of the modification of organic species by
natural selection, there is certainly no evidence that animals have
exerted upon any form of life an influence analogous to that of
domestication upon plants, quadrupeds, and birds reared artificially by
man; and this is as true of unforeseen as of purposely effected
improvements accomplished by voluntary selection of breeding animals.
[29] ----"And it may be remarked that, as the world has passed through
these several stages of strife to produce a Christendom, so by relaxing
in the enterprises it has learnt, does it tend downwards, through
inverted steps, to wildness and the waste again. Let a people give up
their contest with moral evil; disregard the injustice, the ignorance,
the greediness, that may prevail among them, and part more and more with
the Christian element of their civilization; and in declining this
battle with sin, they will inevitably get embroiled with men. Threats of
war and revolution punish their unfaithfulness; and if then, instead of
retracing their steps, they yield again, and are driven before the
storm, the very arts they had created, the structures they had raised,
the usages they had established, are swept away; 'in that very day their
thoughts perish.' The portion they had reclaimed from the young earth's
ruggedness is lost; and failing to stand fast against man, they finally
get embroiled with nature, and are thrust down beneath her ever-living
hand."--MARTINEAU'S _Sermon_, "_The Good Soldier of Jesus Christ_."
[30] The dependence of man upon the aid of spontaneous nature, in his
most arduous material works, is curiously illustrated by the fact that
one of the most serious difficulties to be encountered in executing the
proposed gigantic scheme of draining the Zuiderzee in Holland, is that
of procuring brushwood for the fascines to be employed in the
embankments. See DIGGELEN'S pamphlet, "_Groote Werken in Nederland_."
[31] In heavy storms, the force of the waves as they strike against a
sea wall is from one and a half to two tons to the square foot, and
Stevenson, in one instance at Skerryvore, found this force equal to
three tons per foot.
The seaward front of the breakwater at Cherbourg exposes a surface of
about 2,500,000 square feet. In rough weather the waves beat against
this whole face, though at the depth of twenty-two yards, which is the
height of the breakwater, they exert a very much less violent motive
force than at and near the surface of the sea, because this force
diminishes in geometrical, as the distance below the surface increases
in arithmetical proportion. The shock of the waves is received several
thousand times in the course of twenty-four hours, and hence the sum of
impulse which the breakwater resists in one stormy day amounts to many
thousands of millions of tons. The breakwater is entirely an artificial
construction. If then man could accumulate and control the forces which
he is able effectually to resist, he might be said to be, physically
speaking, omnipotent.
[32] Some well known experiments show that it is quite possible to
accumulate the solar heat by a simple apparatus, and thus to obtain a
temperature which might be economically important even in the climate of
Switzerland. Saussure, by receiving the sun's rays in a nest of boxes
blackened within and covered with glass, raised a thermometer enclosed
in the inner box to the boiling point; and under the more powerful sun
of the cape of Good Hope, Sir John Herschel cooked the materials for a
family dinner by a similar process, using, however, but a single box,
surrounded with dry sand and covered with two glasses. Why should not so
easy a method of economizing fuel be resorted to in Italy, and even in
more northerly climates?
The unfortunate John Davidson records in his journal that he saved fuel
in Morocco by exposing his teakettle to the sun on the roof of his
house, where the water rose to the temperature of one hundred and forty
degrees, and, of course, needed little fire to bring it to boil. But
this was the direct and simple, not the accumulated heat of the sun.
[33] In the successive stages of social progress, the most destructive
periods of human action upon nature are the pastoral condition, and that
of incipient stationary civilization, or, in the newly discovered
countries of modern geography, the colonial, which corresponds to the
era of early civilization in older lands. In more advanced states of
culture, conservative influences make themselves felt; and if highly
civilized communities do not always restore the works of nature, they at
least use a less wasteful expenditure than their predecessors in
consuming them.
[34] The character of geological formation is an element of very great
importance in determining the amount of erosion produced by running
water, and, of course, in measuring the consequences of clearing off the
forests. The soil of the French Alps yields very readily to the force of
currents, and the declivities of the northern Apennines are covered with
earth which becomes itself a fluid when saturated with water. Hence the
erosion of such surfaces is vastly greater than on many other mountains
of equal steepness of inclination. This point is fully considered by the
authors referred to in chap. iii, _post_.
[35] The Travels of Dr. Dwight, president of Yale College, which embody
the results of his personal observations, and of his inquiries among the
early settlers, in his vacation excursions in the Northern States of the
American Union, though presenting few instrumental measurements or
tabulated results, are of value for the powers of observation they
exhibit, and for the sound common sense with which many natural
phenomena, such for instance as the formation of the river meadows,
called "intervales," in New England, are explained. They present a true
and interesting picture of physical conditions, many of which have long
ceased to exist in the theatre of his researches, and of which few other
records are extant.
[36] The general law of temperature is that it decreases as we ascend.
But, in hilly regions, the law is reversed in cold, still weather, the
cold air descending, by reason of its greater gravity, into the valleys.
If there be wind enough, however, to produce a disturbance and
intermixture of higher and lower atmospheric strata, this exception to
the general law does not take place. These facts have long been familiar
to the common people of Switzerland and of New England, but their
importance has not been sufficiently taken into account in the
discussion of meteorological observations. The descent of the cold air
and the rise of the warm affect the relative temperatures of hills and
valleys to a much greater extent than has been usually supposed. A
gentleman well known to me kept a thermometrical record for nearly half
a century, in a New England country town, at an elevation of at least
1,500 feet above the sea. During these years his thermometer never fell
lower than 26° Fahrenheit, while at the shire town of the county,
situated in a basin one thousand feet lower, and ten miles distant, as
well as at other points in similar positions, the mercury froze several
times in the same period.
[37] Railroad surveys must be received with great caution where any
motive exists for _cooking_ them. Capitalists are shy of investments in
roads with steep grades, and of course it is important to make a fair
show of facilities in obtaining funds for new routes. Joint-stock
companies have no souls; their managers, in general, no consciences.
Cases can be cited where engineers and directors of railroads, with long
grades above one hundred feet to the mile, have regularly sworn in their
annual reports, for years in succession, that there were no grades upon
their routes exceeding half that elevation. In fact, every person
conversant with the history of these enterprises knows that in their
public statements falsehood is the rule, truth the exception.
What I am about to remark is not exactly relevant to my subject; but it
is hard to "get the floor" in the world's great debating society, and
when a speaker who has anything to say once finds access to the public
ear, he must make the most of his opportunity, without inquiring too
nicely whether his observations are "in order." I shall harm no honest
man by endeavoring, as I have often done elsewhere, to excite the
attention of thinking and conscientious men to the dangers which
threaten the great moral and even political interests of Christendom,
from the unscrupulousness of the private associations that now control
the monetary affairs, and regulate the transit of persons and property,
in almost every civilized country. More than one American State is
literally governed by unprincipled corporations, which not only defy the
legislative power, but have, too often, corrupted even the
administration of justice. Similar evils have become almost equally rife
in England, and on the Continent; and I believe the decay of commercial
morality, and indeed of the sense of all higher obligations than those
of a pecuniary nature, on both sides of the Atlantic, is to be ascribed
more to the influence of joint-stock banks and manufacturing and railway
companies, to the workings, in short, of what is called the principle of
"associate action," than to any other one cause of demoralization.
The apophthegm, "the world is governed too much," though unhappily too
truly spoken of many countries--and perhaps, in some aspects, true of
all--has done much mischief whenever it has been too unconditionally
accepted as a political axiom. The popular apprehension of being
over-governed, and, I am afraid, more emphatically the fear of being
over-taxed, has had much to do with the general abandonment of certain
governmental duties by the ruling powers of most modern states. It is
theoretically the duty of government to provide all those public
facilities of intercommunication and commerce, which are essential to
the prosperity of civilized commonwealths, but which individual means
are inadequate to furnish, and for the due administration of which
individual guaranties are insufficient. Hence public roads, canals,
railroads, postal communications, the circulating medium of exchange,
whether metallic or representative, armies, navies, being all matters in
which the nation at large has a vastly deeper interest than any private
association can have, ought legitimately to be constructed and provided
only by that which is the visible personification and embodiment of the
nation, namely, its legislative head. No doubt the organization and
management of these institutions by government are liable, as are all
things human, to great abuses. The multiplication of public
placeholders, which they imply, is a serious evil. But the corruption
thus engendered, foul as it is, does not strike so deep as the
rottenness of private corporations; and official rank, position, and
duty have, in practice, proved better securities for fidelity and
pecuniary integrity in the conduct of the interests in question, than
the suretyships of private corporate agents, whose bondsmen so often
fail or abscond before their principal is detected.
Many theoretical statesmen have thought that voluntary associations for
strictly pecuniary and industrial purposes, and for the construction and
control of public works, might furnish, in democratic countries, a
compensation for the small and doubtful advantages, and at the same time
secure an exemption from the great and certain evils, of aristocratic
institutions. The example of the American States shows that private
corporations--whose rule of action is the interest of the association,
not the conscience of the individual--though composed of
ultra-democratic elements, may become most dangerous enemies to rational
liberty, to the moral interests of the commonwealth, to the purity of
legislation and of judicial action, and to the sacredness of private
rights.
[38] It is impossible to say how far the abstraction of water from the
earth by broad-leaved field and garden plants--such as maize, the gourd
family, the cabbage, &c.--is compensated by the condensation of dew,
which sometimes pours from them in a stream, by the exhalation of
aqueous vapor from their leaves, which is directly absorbed by the
ground, and by the shelter they afford the soil from sun and wind, thus
preventing evaporation. American farmers often say that after the leaves
of Indian corn are large enough to "shade the ground," there is little
danger that the plants will suffer from drought; but it is probable that
the comparative security of the fields from this evil is in part due to
the fact that, at this period of growth, the roots penetrate down to a
permanently humid stratum of soil, and draw from it the moisture they
require. Stirring the ground between the rows of maize with a light
harrow or cultivator, in very dry seasons, is often recommended as a
preventive of injury by drought. It would seem, indeed, that loosening
and turning over the surface earth might aggravate the evil by promoting
the evaporation of the little remaining moisture; but the practice is
founded partly on the belief that the hygroscopicity of the soil is
increased by it to such a degree that it gains more by absorption than
it loses by evaporation, and partly on the doctrine that to admit air to
the rootlets, or at least to the earth near them, is to supply directly
elements of vegetable growth.
[39] The vine-wood planks of the ancient great door of the cathedral at
Ravenna, which measured thirteen feet in length by a foot and a quarter
in width, are traditionally said to have been brought from the Black
Sea, by way of Constantinople, about the eleventh or twelfth century. No
vines of such dimensions are now found in any other part of the East,
and, though I have taken some pains on the subject, I never found in
Syria or in Turkey a vine stock exceeding six inches in diameter, bark
excluded.
[40] The Northmen who--as I think it has been indisputably established
by Professor Rafn of Copenhagen--visited the coast of Massachusetts
about the year 1000, found grapes growing there in profusion, and the
vine still flourishes in great variety and abundance in the southeastern
counties of that State. The townships in the vicinity of the Dighton
rock, supposed by many--with whom, however, I am sorry I cannot
agree--to bear a Scandinavian inscription, abound in wild vines, and I
have never seen a region which produced them so freely. I have no doubt
that the cultivation of the grape will become, at no distant day, one of
the most important branches of rural industry in that district.
[41] _Les États Unis d'Amérique en 1863_, p. 360. By "improved" land, in
the reports on the census of the United States, is meant "cleared land
used for grazing, grass, or tillage, or which is now fallow, connected
with or belonging to a farm."--_Instructions to Marshals and Assistants,
Census of 1850_, schedule 4, §§ 2, 3.
[42] Cotton, though cultivated in Asia and Africa from the remotest
antiquity, and known as a rare and costly product to the Latins and the
Greeks, was not used by them to any considerable extent, nor did it
enter into their commerce as a regular article of importation. The early
voyagers found it in common use in the West Indies and in the provinces
first colonized by the Spaniards; but it was introduced into the
territory of the United States by European settlers, and did not become
of any importance until after the Revolution. Cotton seed was sown in
Virginia as early as 1621, but was not cultivated with a view to profit
for more than a century afterward. Sea-island cotton was first grown on
the coast of Georgia in 1786, the seed having been brought from the
Bahamas, where it had been introduced from Anguilla.--BIGELOW, _Les
États Unis en 1863_, p. 370.
[43] The sugar cane was introduced by the Arabs into Sicily and Spain as
early as the ninth century, and though it is now scarcely grown in those
localities, I am not aware of any reason to doubt that its cultivation
might be revived with advantage. From Spain it was carried to the West
Indies, though different varieties have since been introduced into those
islands from other sources. Tea is now cultivated with a certain success
in Brazil, and promises to become an important crop in the Southern
States of the American Union. The lemon is, I think, readily
recognizable, by Pliny's description, as known to the ancients, but it
does not satisfactorily appear that they were acquainted with the
orange.
[44] John Smith mentions, in his _Historie of Virginia_, 1624, pease and
beans as having been cultivated by the natives before the arrival of the
whites, and there is no doubt, I believe, that the pumpkin and several
other cucurbitaceous plants are of American origin; but most, if not all
the varieties of pease, beans, and other pod fruits now grown in
American gardens, are from European and other foreign seed. See
_Appendix_, No, 8.
[45] There are some usages of polite society which are inherently low in
themselves, and debasing in their influence and tendency, and which no
custom or fashion can make respectable or fit to be followed by
self-respecting persons. It is essentially vulgar to smoke or chew
tobacco, and especially to take snuff; it is unbecoming a gentleman, to
perform the duties of his coachman; it is indelicate in a lady to wear
in the street skirts so long that she cannot walk without grossly
soiling them. Not that all these things are not practised by persons
justly regarded as gentlemen and ladies; but the same individuals would
be, and feel themselves to be, much more emphatically gentlemen and
ladies, if they abstained from them.
[46] The name _portogallo_, so generally applied to the orange in Italy,
seems to favor this claim. The orange, however, was known in Europe
before the discovery of the Cape of Good Hope, and, therefore, before
the establishment of direct relations between Portugal and the East.
A correspondent of the _Athenæum_, in describing the newly excavated
villa, which has been named Livia's Villa, near the Porta del Popolo at
Rome, states that: "The walls of one of the rooms are, singularly
enough, decorated with landscape paintings, a grove of palm and _orange_
trees, with fruits and birds on the branches--the colors all as fresh
and lively as if painted yesterday." The writer remarks on the character
of this decoration as something very unusual in Roman architecture; and
if the trees in question are really orange, and not lemon trees, this
circumstance may throw some doubt on the antiquity of the painting. If,
on the other hand, it proves really ancient, it shows that the orange
was known to the Roman painters, if not gardeners. The landscape may
perhaps represent Oriental, not European scenery. The accessories of the
picture would probably determine that question.--_Athenæum_, No. 1859,
June 13, 1863.
MÜLLER, _Das Buch der Pflanzenwelt_, p. 86, asserts that in 1802 the
ancestor of all the mulberries in France, planted in 1500, was still
standing in a garden in the village of Allan-Montélimart.
[47] The vegetables which, so far as we know their history, seem to have
been longest the objects of human care, can, by painstaking industry, be
made to grow under a great variety of circumstances, and some of
them--the vine for instance--prosper nearly equally well, when planted
and tended, on soils of almost any geological character; but their seeds
vegetate only in artificially prepared ground, they have little
self-sustaining power, and they soon perish when the nursing hand of man
is withdrawn from them. In range of climate, wild plants are much more
limited than domestic, but much less so with regard to the state of the
soil in which they germinate and grow. See _Appendix_, No. 9.
Dr. Dwight remarks that the seeds of American forest trees will not
vegetate when dropped on grassland. This is one of the very few errors
of personal observation to be found in that author's writings. There are
seasons, indeed, when few tree seeds germinate in the meadows and the
pastures, and years favorable to one species are not always propitious
to another; but there is no American forest tree known to me which does
not readily propagate itself by seed in the thickest greensward, if its
germs are not disturbed by man or animals.
[48] Some years ago I made a collection of weeds in the wheatfields of
Upper Egypt, and another in the gardens on the Bosphorus. Nearly all the
plants were identical with those which grow under the same conditions in
New England. I do not remember to have seen in America the scarlet wild
poppy so common in European grainfields. I have heard, however, that it
has lately crossed the Atlantic, and I am not sorry for it. With our
abundant harvests of wheat, we can well afford to pay now and then a
loaf of bread for the cheerful radiance of this brilliant flower.
[49] Josselyn, who wrote about fifty years after the foundation of the
first British colony in New England, says that the settlers at Plymouth
had observed more than twenty English plants springing up spontaneously
near their improvements.
Every country has many plants not now, if ever, made use of by man, and
therefore not designedly propagated by him, but which cluster around his
dwelling, and continue to grow luxuriantly on the ruins of his rural
habitation after he has abandoned it. The site of a cottage, the very
foundation stones of which have been carried off, may often be
recognized, years afterward, by the rank weeds which cover it, though no
others of the same species are found for miles.
"Mediæval Catholicism," says Vaupell, "brought us the red
horsehoof--whose reddish-brown flower buds shoot up from the ground when
the snow melts, and are followed by the large leaves--_lægekulsukker_
and snake-root, which grow only where there were convents and other
dwellings in the Middle Ages."--_Bögens Indvandring i de Danske Skove_,
pp. 1, 2.
[50] VAUPELL, _Bögens Indvandring i de Danske Skove_, p. 2.
[51] It is, I believe, nearly certain that the Turks inflicted tobacco
upon Hungary, and probable that they in some measure compensated the
injury by introducing maize also, which, as well as tobacco, has been
claimed as Hungarian by patriotic Magyars.
[52] Accidents sometimes limit, as well as promote, the propagation of
foreign vegetables in countries new to them. The Lombardy poplar is a
di[oe]cious tree, and is very easily grown from cuttings. In most of the
countries into which it has been introduced the cuttings have been taken
from the male, and as, consequently, males only have grown from them,
the poplar does not produce seed in those regions. This is a fortunate
circumstance, for otherwise this most worthless and least ornamental of
trees would spread with a rapidity that would make it an annoyance to
the agriculturist. See _Appendix_, No. 10.
[53] Tempests, violent enough to destroy all cultivated plants, often
spare those of spontaneous growth. During the present summer, I have
seen in Northern Italy, vineyards, maize fields, mulberry and fruit
trees completely stripped of their foliage by hail, while the forest
trees scattered through the meadows, and the shrubs and brambles which
sprang up by the wayside, passed through the ordeal with scarcely the
loss of a leaflet.
[54] The boar spear is provided with a short crossbar, to enable the
hunter to keep the infuriated animal at bay after he has transfixed him.
[55] Some botanists think that a species of water lily represented in
many Egyptian tombs has become extinct, and the papyrus, which must have
once been abundant in Egypt, is now found only in a very few localities
near the mouth of the Nile. It grows very well and ripens its seeds in
the waters of the Anapus near Syracuse, and I have seen it in garden
ponds at Messina and in Malta. There is no apparent reason for believing
that it could not be easily cultivated in Egypt, to any extent, if there
were any special motive for encouraging its growth.
[56] Although it is not known that man has extirpated any vegetable, the
mysterious diseases which have, for the last twenty years, so
injuriously affected the potato, the vine, the orange, the olive, and
silk husbandry--whether in this case the malady resides in the mulberry
or in the insect--are ascribed by some to a climatic deterioration
produced by excessive destruction of the woods. As will be seen in the
next chapter, a retardation in the period of spring has been observed in
numerous localities in Southern Europe, as well as in the United States.
This change has been thought to favor the multiplication of the obscure
parasites which cause the injury to the vegetables just mentioned.
Babinet supposes the parasites which attack the grape and the potato to
be animal, not vegetable, and he ascribes their multiplication to
excessive manuring and stimulation of the growth of the plants on which
they live. They are now generally, if not universally, regarded as
vegetable, and if they are so, Babinet's theory would be even more
plausible than on his own supposition.--_Études et Lectures_, ii, p.
269.
It is a fact of some interest in agricultural economy, that the oidium,
which is so destructive to the grape, has produced no pecuniary loss to
the proprietors of the vineyards in France. "The price of wine," says
Lavergne, "has quintupled, and as the product of the vintage has not
diminished in the same proportion, the crisis has been, on the whole,
rather advantageous than detrimental to the country."--_Économie Rurale
de la France_, pp. 263, 264.
France produces a considerable surplus of wines for exportation, and the
sales to foreign consumers are the principal source of profit to French
vinegrowers. In Northern Italy, on the contrary, which exports little
wine, there has been no such increase in the price of wine as to
compensate the great diminution in the yield of the vines, and the loss
of this harvest is severely felt. In Sicily, however, which exports much
wine, prices have risen as rapidly as in France. Waltershausen informs
us that in the years 1838-'42, the red wine of Mount Etna sold at the
rate of one kreuzer and a half, or one cent the bottle, and sometimes
even at but two thirds that price, but that at present it commands five
or six times as much.
The grape disease has operated severely on small cultivators whose
vineyards only furnished a supply for domestic use, but Sicily has
received a compensation in the immense increase which it has occasioned
in both the product and the profits of the sulphur mines. Flour of
sulphur is applied to the vine as a remedy against the disease, and the
operation is repeated from two to three or four--and even, it is said,
eight or ten times--in a season. Hence there is a great demand for
sulphur in all the vine-growing countries of Europe, and Waltershausen
estimates the annual consumption of that mineral for this single purpose
at 850,000 _centner_, or more than forty thousand tons. The price of
sulphur has risen in about the same proportion as that of
wine.--WALTERSHAUSEN, _Ueber den Sicilianischen Ackerbau_, pp. 19, 20.
[57] Some recent observations of the learned traveller Wetzstein are
worthy of special notice. "The soil of the Haurân," he remarks,
"produces, in its primitive condition, much wild rye, which is not known
as a cultivated plant in Syria, and much wild barley and oats. These
cereals precisely resemble the corresponding cultivated plants in leaf,
ear, size, and height of straw, but their grains are sensibly flatter
and poorer in flour."--_Reisebericht über Haurân und die Trachonen_, p.
40.
[58] This remark is much less applicable to fruit trees than to garden
vegetables and the cerealia. The wild orange of Florida, though once
considered indigenous, is now generally thought by botanists to be
descended from the European orange introduced by the early colonists.
The fig and the olive are found growing wild in every country where
those trees are cultivated. The wild fig differs from the domesticated
in its habits, its season of fructification, and its insect population,
but is, I believe, not specifically distinguishable from the garden fig,
though I do not know that it is reclaimable by cultivation. The wild
olive, which is so abundant in the Tuscan Maremma, produces good fruit
without further care, when thinned out and freed from the shade of other
trees, and is particularly suited for grafting. See SALVAGNOLI, _Memorie
sulle Maremme_, pp. 63-73. See _Appendix_, No. 12.
FRAAS, _Klima und Pflanzenwelt in der Zeit_, pp. 35-38, gives, upon the
authority of Link and other botanical writers, a list of the native
habitats of most cereals and of many fruits, or at least of localities
where these plants are said to be now found wild; but the data do not
appear to rest, in general, upon very trustworthy evidence.
Theoretically, there can be little doubt that all our cultivated plants
are modified forms of spontaneous vegetation, but the connection is not
historically shown, nor are we able to say that the originals of some
domesticated vegetables may not be now extinct and unrepresented in the
existing wild flora. See, on this subject, HUMBOLDT, _Ansichten der
Natur_, i, pp. 208, 209. The following are interesting incidents: "A
negro slave of the great Cortez was the first who sowed wheat in New
Spain. He found three grains of it among the rice which had been brought
from Spain as food for the soldiers. In the Franciscan monastery at
Quito, I saw the earthen pot which contained the first wheat sown there
by Friar Jodoco Rixi, of Ghent. It was preserved as a relic."
The Adams of modern botany and zoology have been put to hard shifts in
finding names for the multiplied organisms which the Creator has brought
before them, "to see what they would call them;" and naturalists and
philosophers have shown much moral courage in setting at naught the laws
of philology in the coinage of uncouth words to express scientific
ideas. It is much to be wished that some bold neologist would devise
English technical equivalents for the German _verwildert_, run-wild, and
_veredelt_, improved by cultivation.
[59] Could the bones and other relics of the domestic quadrupeds
destroyed by disease or slaughtered for human use in civilized countries
be collected into large deposits, as obscure causes have gathered
together those of extinct animals, they would soon form aggregations
which might almost be called mountains. There were in the United States,
in 1860, as we shall see hereafter, nearly one hundred and two millions
of horses, black cattle, sheep, and swine. There are great numbers of
all the same animals in the British American Provinces, and in Mexico,
and there are large herds of wild horses on the plains, and of tamed
among the independent Indian tribes of North America. It would perhaps
not be extravagant to suppose that all those cattle may amount to two
thirds as many as those of the United States, and thus we have in North
America a total of 170,000,000 domestic quadrupeds belonging to species
introduced by European colonization, besides dogs, cats, and other
four-footed household pets and pests, also of foreign origin.
If we allow half a solid foot to the skeleton and other slowly
destructible parts of each animal, the remains of these herds would form
a cubical mass measuring not much short of four hundred and fifty feet
to the side, or a pyramid equal in dimensions to that of Cheops, and as
the average life of these animals does not exceed six or seven years,
the accumulations of their bones, horns, hoofs, and other durable
remains would amount to at least fifteen times as great a volume in a
single century. It is true that the actual mass of solid matter, left by
the decay of dead domestic quadrupeds and permanently added to the crust
of the earth, is not so great as this calculation makes it. The greatest
proportion of the soft parts of domestic animals, and even of the bones,
is soon decomposed, through direct consumption by man and other
carnivora, industrial use, and employment as manure, and enters into new
combinations in which its animal origin is scarcely traceable; there is,
nevertheless, a large annual residuum, which, like decayed vegetable
matter, becomes a part of the superficial mould; and in any event, brute
life immensely changes the form and character of the superficial strata,
if it does not sensibly augment the quantity of the matter composing
them.
The remains of man, too, add to the earthy coating that covers the face
of the globe. The human bodies deposited in the catacombs during the
long, long ages of Egyptian history, would perhaps build as large a pile
as one generation of the quadrupeds of the United States. In the
barbarous days of old Moslem warfare, the conquerors erected large
pyramids of human skulls. The soil of cemeteries in the great cities of
Europe has sometimes been raised several feet by the deposit of the dead
during a few generations. In the East, Turks and Christians alike bury
bodies but a couple of feet beneath the surface. The grave is respected
as long as the tombstone remains, but the sepultures of the ignoble
poor, and of those whose monuments time or accident has removed, are
opened again and again to receive fresh occupants. Hence the ground in
Oriental cemeteries is pervaded with relics of humanity, if not wholly
composed of them; and an examination of the soil of the lower part of
the _Petit Champ des Morts_ at Pera, by the naked eye alone, shows the
observer that it consists almost exclusively of the comminuted bones of
his fellow man.
[60] It is asserted that the bones of mammoths and mastodons, in many
instances, appear to have been grazed or cut by flint arrow-heads or
other stone weapons. These accounts have often been discredited, because
it has been assumed that the extinction of these animals was more
ancient than the existence of man. Recent discoveries render it highly
probable, if not certain, that this conclusion has been too hastily
adopted. Lyell observes: "These stories * * must in future be more
carefully inquired into, for we can scarcely doubt that the mastodon in
North America lived down to a period when the mammoth coexisted with man
in Europe."--_Antiquity of Man_, p. 354.
On page 143 of the volume just quoted, the same very distinguished
writer remarks that man "no doubt played his part in hastening the era
of the extinction" of the large pachyderms and beasts of prey; but, as
contemporaneous species of other animals, which man cannot be supposed,
to have extirpated, have also become extinct, he argues that the
disappearance of the quadrupeds in question cannot be ascribed to human
action alone.
On this point it may be observed that, as we cannot know what precise
physical conditions were necessary to the existence of a given extinct
organism, we cannot say how far such conditions may have been modified
by the action of man, and he may therefore have influenced the life of
such organisms in ways, and to an extent, of which we can form no just
idea.
[61] Evelyn thought the depasturing of grass by cattle serviceable to
its growth. "The biting of cattle," he remarks, "gives a gentle
loosening to the roots of the herbage, and makes it to grow fine and
sweet, and their very breath and treading as well as soil, and the
comfort of their warm bodies, is wholesome and marvellously
cherishing."--_Terra, or Philosophical Discourse of Earth_, p. 36.
In a note upon this passage, Hunter observes: "Nice farmers consider the
lying of a beast upon the ground, for one night only, as a sufficient
tilth for the year. The breath of graminivorous quadrupeds does
certainly enrich the roots of grass; a circumstance worthy of the
attention of the philosophical farmer."--_Terra_, same page.
The "philosophical farmer" of the present day will not adopt these
opinions without some qualification.
[62] The rat and the mouse, though not voluntarily transported, are
passengers by every ship that sails from Europe to a foreign port, and
several species of these quadrupeds have, consequently, much extended
their range and increased their numbers in modern times. From a story of
Heliogabalus related by Lampridius, _Hist. Aug. Scriptores_, ed.
Casaubon, 1690, p. 110, it would seem that mice at least were not very
common in ancient Rome. Among the capricious freaks of that emperor, it
is said that he undertook to investigate the statistics of the arachnoid
population of the capital, and that 10,000 pounds of spiders (or
spiders' webs--for aranea is equivocal) were readily collected; but when
he got up a mouse show, he thought ten thousand mice a very fair number.
I believe as many might almost be found in a single palace in modern
Rome. Rats are not less numerous in all great cities, and in Paris,
where their skins are used for gloves, and their flesh, it is whispered,
in some very complex and equivocal dishes, they are caught by legions. I
have read of a manufacturer who contracted to buy of the rat catchers,
at a high price, all the rat skins they could furnish before a certain
date, and failed, within a week, for want of capital, when the stock of
peltry had run up to 600,000.
[63] BIGELOW, _Les États Unis en_ 1863, pp. 379, 380. In the same
paragraph this volume states the number of animals slaughtered in the
United States by butchers, in 1859, at 212,871,653. This is an error of
the press. Number is confounded with value. A reference to the tables of
the census shows that the animals slaughtered that year were estimated
at 212,871,653 _dollars_; the number of head is not given. The wild
horses and horned cattle of the prairies and the horses of the Indians
are not included in the returns.
[64] Of this total number, 2,240,000, or nearly nine per cent., are
reported as working oxen. This would strike European, and especially
English agriculturists, as a large proportion; but it is explained by
the difference between a new country and an old, in the conditions which
determine the employment of animal labor. Oxen are very generally used
in the United States and Canada for hauling timber and firewood through
and from the forests; for ploughing in ground still full of rocks,
stumps, and roots; for breaking up the new soil of the prairies with its
strong matting of native grasses, and for the transportation of heavy
loads over the rough roads of the interior. In all these cases, the
frequent obstructions to the passage of the timber, the plough, and the
sled or cart, are a source of constant danger to the animals, the
vehicles, and the harness, and the slow and steady step of the ox is
attended with much less risk than the swift and sudden movements of the
impatient horse. It is surprising to see the sagacity with which the
dull and clumsy ox--hampered as he is by the rigid yoke, the most absurd
implement of draught ever contrived by man--picks his way, when once
trained to forest work, among rocks and roots, and even climbs over
fallen trees, not only moving safely, but drawing timber over ground
wholly impracticable for the light and agile horse.
Cows, so constantly employed for draught in Italy, are never yoked or
otherwise used for labor in America, except in the Slave States.
[65] "About five miles from camp we ascended to the top of a high hill,
and for a great distance ahead every square mile seemed to have a herd
of buffalo upon it. Their number was variously estimated by the members
of the party; by some as high as half a million. I do not think it any
exaggeration to set it down at 200,000."--STEVENS'S _Narrative and Final
Report. Reports of Explorations and Surveys for Railroad to Pacific_,
vol. xii, book i, 1860.
The next day, the party fell in with a "buffalo trail," where at least
100,000 were thought to have crossed a slough.
[66] The most zealous and successful New England hunter of whom I have
any personal knowledge, and who continued to indulge his favorite
passion much beyond the age which generally terminates exploits in
woodcraft, lamented on his deathbed that he had not lived long enough to
carry up the record of his slaughtered deer to the number of one
thousand, which he had fixed as the limit of his ambition. He was able
to handle the rifle, for sixty years, at a period when the game was
still nearly as abundant as ever, but had killed only nine hundred and
sixty of these quadrupeds, of all species. The exploits of this Nimrod
have been far exceeded by prairie hunters, but I doubt whether, in the
originally wooded territory of the Union, any single marksman has
brought down a larger number.
[67] _Erdkunde_, viii. _Asien, 1ste Abtheilung_, pp. 660, 758.
[68] See chapter iii, _post_; also HUMBOLDT, _Ansichten der Natur_, i,
p. 71. From the anatomical character of the bones of the urus, or
auerochs, found among the relics of the lacustrine population of ancient
Switzerland, and from other circumstances, it is inferred that this
animal had been domesticated by that people; and it is stated, I know
not upon what authority, in _Le Alpi che cingono l'Italia_, that it had
been tamed by the Veneti also. See LYELL, _Antiquity of Man_, pp. 24,
25, and the last-named work, p. 489. This is a fact of much interest,
because it is, I believe, the only known instance of the extinction of a
domestic quadruped, and the extreme improbability of such an event gives
some countenance to the theory of the identity of the domestic ox with,
and its descent from, the urus.
[69] In maintaining the recent existence of the lion in the countries
named in the text, naturalists have, perhaps, laid too much weight on
the frequent occurrence of representations of this animal in sculptures
apparently of a historical character. It will not do to argue, twenty
centuries hence, that the lion and the unicorn were common in Great
Britain in Queen Victoria's time, because they are often seen "fighting
for the crown" in the carvings and paintings of that period.
[70]
Dar nach sloger schiere, einen wisent bat elch.
Starcher bore biere. but einen grimmen schelch.
_XVI Auentiure._
The testimony of the _Nibelungen-Lied_ is not conclusive evidence that
these quadrupeds existed in Germany at the time of the composition of
that poem. It proves too much; for, a few lines above those just quoted,
Sigfrid is said to have killed a lion, an animal which the most
patriotic Teuton will hardly claim as a denizen of mediæval Germany.
[71] The wild turkey takes readily to the water, and is able to cross
rivers of very considerable width by swimming. By way of giving me an
idea of the former abundance of this bird, an old and highly respectable
gentleman who was among the early white settlers of the West, told me
that he once counted, in walking down the northern bank of the Ohio
River, within a distance of four miles, eighty-four turkeys as they
landed singly, or at most in pairs, after swimming over from the
Kentucky side.
[72] The wood pigeon has been observed to increase in numbers in Europe
also, when pains have been taken to exterminate the hawk. The pigeons,
which migrated in flocks so numerous that they were whole days in
passing a given point, were no doubt injurious to the grain, but
probably less so than is generally supposed; for they did not confine
themselves exclusively to the harvests for their nourishment.
[73] Pigeons were shot near Albany, in New York, a few years ago, with
green rice in their crops, which it was thought must have been growing,
a very few hours before, at the distance of seven or eight hundred
miles.
[74] Professor Treadwell, of Massachusetts, found that a half-grown
American robin in confinement ate in one day sixty-eight earthworms,
weighing together nearly once and a half as much as the bird himself,
and another had previously starved upon a daily allowance of eight or
ten worms, or about twenty per cent. of his own weight. The largest of
these numbers appeared, so far as could be judged by watching parent
birds of the same species, as they brought food to their young, to be
much greater than that supplied to them when fed in the nest; for the
old birds did not return with worms or insects oftener than once in ten
minutes on an average. If we suppose the parents to hunt for food twelve
hours in a day, and a nest to contain four young, we should have
seventy-two worms, or eighteen each, as the daily supply of the brood.
It is probable enough that some of the food collected by the parents may
be more nutritious than the earthworms, and consequently that a smaller
quantity sufficed for the young in the nest than when reared under
artificial conditions.
The supply required by growing birds is not the measure of their wants
after they have arrived at maturity, and it is not by any means certain
that great muscular exertion always increases the demand for
nourishment, either in the lower animals or in man. The members of the
English Alpine Club are not distinguished for appetites which would make
them unwelcome guests to Swiss landlords, and I think every man who has
had the personal charge of field or railway hands, must have observed
that laborers who spare their strength the least are not the most
valiant trencher champions. During the period when imprisonment for debt
was permitted in New England, persons confined in country jails had no
specific allowance, and they were commonly fed without stint. I have
often inquired concerning their diet, and been assured by the jailers
that their prisoners, who were not provided with work or other means of
exercise, consumed a considerably larger supply of food than common
out-door laborers.
[75] I hope Michelet has good authority for this statement, but I am
unable to confirm it.
[76] Apropos of the sparrow--a single pair of which, according to
Michelet, p. 315, carries to the nest four thousand and three hundred
caterpillars or coleoptera in a week--I take from the _Record_, an
English religious newspaper, of December 15, 1862, the following article
communicated to a country paper by a person who signs himself "A real
friend to the farmer:"
"_Crawley Sparrow Club._--The annual dinner took place at the George Inn
on Wednesday last. The first prize was awarded to Mr. I. Redford, Worth,
having destroyed within the last year 1,467. Mr. Heayman took the second
with 1,448 destroyed. Mr. Stone, third, with 982 affixed. Total
destroyed, 11,944. Old birds, 8,663; young ditto, 722; eggs, 2,556."
This trio of valiant fowlers, and their less fortunate--or rather less
unfortunate, but not therefore less guilty--associates, have rescued by
their prowess, it may be, a score of pecks of grain from being devoured
by the voracious sparrow, but every one of the twelve thousand hatched
and unhatched birds, thus sacrificed to puerile vanity and ignorant
prejudice, would have saved his bushel of wheat by preying upon insects
that destroy the grain. Mr. Redford, Mr. Heayman, and Mr. Stone ought to
contribute the value of the bread they have wasted to the fund for the
benefit of the Lancashire weavers; and it is to be hoped that the next
Byron will satirize the sparrowcide as severely as the first did the
prince of anglers, Walton, in the well known lines:
"The quaint, old, cruel coxcomb in his gullet
Should have a hook, and a small trout to pull it."
[77] SALVAGNOLI, _Memorie sulle Maremme Toscane_, p. 143. The country
about Naples is filled with slender towers fifteen or twenty feet high,
which are a standing puzzle to strangers. They are the stations of the
fowlers who watch from them the flocks of small birds and drive them
down in to the nets by throwing stones over them. See _Appendix_, No.
14.
Tschudi has collected in his little work, _Ueber die
Landwirthschaftliche Bedeutung der Vögel_, many interesting facts
respecting the utility of birds, and the wanton destruction of them in
Italy and elsewhere. Not only the owl, but many other birds more
familiarly known as predacious in their habits, are useful by destroying
great numbers of mice and moles. The importance of this last service
becomes strikingly apparent when it is known that the burrows of the
mole are among the most frequent causes of rupture in the dikes of the
Po, and, consequently, of inundations which lay many square miles under
water.--_Annales des Ponts et Chaussées_, 1847, 1re sémestre, p. 150.
See also VOGT, _Nützliche u. schädliche Thiere_.
[78] Wild birds are very tenacious in their habits. The extension of
particular branches of agriculture introduces new birds; but unless in
the case of such changes in physical conditions, particular species seem
indissolubly attached to particular localities. The migrating tribes
follow almost undeviatingly the same precise line of flight in their
annual journeys, and establish themselves in the same breeding places
from year to year. The stork is a strong-winged bird and roves far for
food, but very rarely establishes new colonies. He is common in Holland,
but unknown in England. Not above five or six pairs of storks commonly
breed in the suburbs of Constantinople along the European shore of the
narrow Bosphorus, while--much to the satisfaction of the Moslems, who
are justly proud of the marked partiality of so orthodox a bird--dozens
of chimneys of the true believers on the Asiatic side are crowned with
his nests. See _App._ No. 15.
[79] It is not the unfledged and the nursing bird alone that are exposed
to destruction by severe weather. Whole flocks of adult and
strong-winged tribes are killed by hail. Severe winters are usually
followed by a sensible diminution in the numbers of the non-migrating
birds, and a cold storm in summer often proves fatal to the more
delicate species. On the 10th of June, 184-, five or six inches of snow
fell in Northern Vermont. The next morning I found a humming bird killed
by the cold, and hanging by its claws just below a loose clapboard on
the wall of a small wooden building where it had sought shelter.
[80] LYELL, _Antiquity of Man_, p. 409, observes: "Of birds it is
estimated that the number of those which die every year equals the
aggregate number by which the species to which they respectively belong
is, on the average, permanently represented."
A remarkable instance of the influence of new circumstances upon birds
was observed upon the establishment of a lighthouse on Cape Cod some
years since. The morning after the lamps were lighted for the first
time, more than a hundred dead birds of several different species,
chiefly water fowl, were found at the foot of the tower. They had been
killed in the course of the night by flying against the thick glass or
grating of the lantern. See _Appendix_, No. 16.
Migrating birds, whether for greater security from eagles, hawks, and
other enemies, or for some unknown reason, perform a great part of their
annual journeys by night; and it is observed in the Alps that they
follow the high roads in their passage across the mountains. This is
partly because the food in search of which they must sometimes descend
is principally found near the roads. It is, however, not altogether for
the sake of consorting with man, or of profiting by his labors, that
their line of flight conforms to the paths he has traced, but rather
because the great roads are carried through the natural depressions in
the chain, and hence the birds can cross the summit by these routes
without rising to a height where at the seasons of migration the cold
would be excessive.
The instinct which guides migratory birds in their course is not in all
cases infallible, and it seems to be confounded by changes in the
condition of the surface. I am familiar with a village in New England,
at the junction of two valleys, each drained by a mill stream, where the
flocks of wild geese which formerly passed, every spring and autumn,
were very frequently lost, as it was popularly phrased, and I have often
heard their screams in the night as they flew wildly about in perplexity
as to the proper course. Perhaps the village lights embarrassed them, or
perhaps the constant changes in the face of the country, from the
clearings then going on, introduced into the landscape features not
according with the ideal map handed down in the anserine family, and
thus deranged its traditional geography.
[81] The cappercailzie, or tjäder, as he is called in Sweden, is a bird
of singular habits, and seems to want some of the protective instincts
which secure most other wild birds from destruction. The younger
Læstadius frequently notices the tjäder, in his very remarkable account
of the Swedish Laplanders--a work wholly unsurpassed as a genial picture
of semi-barbarian life, and not inferior in minuteness of detail to
Schlatter's description of the manners of the Nogai Tartars, or even to
Lane's admirable and exhaustive work on the Modern Egyptians. The
tjäder, though not a bird of passage, is migratory, or rather wandering
in domicile, and appears to undertake very purposeless and absurd
journeys. "When he flits," says Læstadius, "he follows a straight
course, and sometimes pursues it quite out of the country. It is said
that, in foggy weather, he sometimes flies out to sea, and, when tired,
falls into the water and is drowned. It is accordingly observed that,
when he flies westwardly, toward the mountains, he soon comes back
again; but when he takes an eastwardly course, he returns no more, and
for a long time is very scarce in Lapland. From this it would seem that
he turns back from the bald mountains, when he discovers that he has
strayed from his proper home, the wood; but when he finds himself over
the Baltic, where he cannot alight to rest and collect himself, he flies
on until he is exhausted and falls into the sea."--PETRUS LÆSTADIUS,
_Journal af första året, etc._, p. 325.
[82] _Die Herzogthümer Schleswig und Holstein_, i, p. 203.
[83] Gulls hover about ships in port, and often far out at sea,
diligently watching for the waste of the caboose. "While the four great
fleets, English, French, Turkish, and Egyptian, were lying in the
Bosphorus, in the summer and autumn of 1853, a young lady of my family
called my attention to the fact that the gulls were far more numerous
about the ships of one of the fleets than about the others. This was
verified by repeated observation, and the difference was owing no doubt
to the greater abundance of the refuse from the cookrooms of the naval
squadron most frequented by the birds. Persons acquainted with the
economy of the navies of the states in question, will be able to
conjecture which fleet was most favored with these delicate attentions.
[84] Birds do not often voluntarily take passage on board ships bound
for foreign countries, but I can testify to one such case. A stork,
which had nested near one of the palaces on the Bosphorus, had, by some
accident, injured a wing, and was unable to join his follows when they
commenced their winter migration to the banks of the Nile. Before he was
able to fly again, he was caught, and the flag of the nation to which
the palace belonged was tied to his leg, so that he was easily
identified at a considerable distance. As his wing grow stronger, he
made several unsatisfactory experiments at flight, and at last, by a
vigorous effort, succeeded in reaching a passing ship bound southward,
and perched himself on a topsail yard. I happened to witness this
movement, and observed him quietly maintaining his position as long as I
could discern him with a spyglass. I suppose he finished the voyage, for
he certainly did not return to the palace.
[85] The enthusiasm of naturalists is not always proportioned to the
magnitude or importance of the organisms they concern themselves with.
It is not recorded that Adams, who found the colossal antediluvian
pachyderm in a thick-ribbed mountain of Siberian ice, ran wild over his
_trouvaille_; but Schmidl, in describing the natural history of the
caves of the Karst, speaks of an eminent entomologist as "_der
glückliche Entdecker_," the _happy_ discoverer of a new coleopteron, in
one of those dim caverns. How various are the sources of happiness!
Think of a learned German professor, the bare enumeration of whose
Rath-ships and scientific Mitglied-ships fills a page, made famous in
the annals of science, immortal, happy, by the discovery of a beetle!
Had that imperial _ennuyé_, who offered a premium for the invention of a
new pleasure, but read Schmidl's _Höhlen des Karstes_, what splendid
rewards would he not have heaped upon Kirby and Spence!
[86] I believe there is no foundation for the supposition that
earthworms attack the tuber of the potato. Some of them, especially one
or two species employed by anglers as bait, if natives of the woods, are
at least rare in shaded grounds, but multiply very rapidly after the
soil is brought under cultivation. Forty or fifty years ago they were so
scarce in the newer parts of New England, that the rustic fishermen of
every village kept secret the few places where they were to be found in
their neighborhood, as a professional mystery, but at present one can
hardly turn over a shovelful of rich moist soil anywhere, without
unearthing several of them. A very intelligent lady, born in the woods
of Northern New England, told me that, in her childhood, these worms
were almost unknown in that region, though anxiously sought for by the
anglers, but that they increased as the country was cleared, and at last
became so numerous in some places, that the water of springs, and even
of shallow wells, which had formerly been excellent, was rendered
undrinkable by the quantity of dead worms that fell into them. The
increase of the robin and other small birds which follow the settler
when he has prepared a suitable home for them, at last checked the
excessive multiplication of the worms, and abated the nuisance.
[87] I have already remarked that the remains of extant animals are
rarely, if ever, gathered in sufficient quantities to possess any
geographical importance by their mere mass; but the decayed exuviæ of
even the smaller and humbler forms of life are sometimes abundant enough
to exercise a perceptible influence on soil and atmosphere. "The plain
of Cumana," says Humboldt, "presents a remarkable phenomenon, after
heavy rains. The moistened earth, when heated by the rays of the sun,
diffuses the musky odor common in the torrid zone to animals of very
different classes, to the jaguar, the small species of tiger cat, the
cabiaï, the gallinazo vulture, the crocodile, the viper, and the
rattlesnake. The gaseous emanations, the vehicles of this aroma, appear
to be disengaged in proportion as the soil, which contains the remains
of an innumerable multitude of reptiles, worms, and insects, begins to
be impregnated with water. Wherever we stir the earth, we are struck
with the mass of organic substances which in turn are developed and
become transformed or decomposed. Nature in these climes seems more
active, more prolific, and so to speak, more prodigal of life."
[88] It is remarkable that Palissy, to whose great merits as an acute
observer I am happy to have frequent occasion to bear testimony, had
noticed that vegetation was necessary to maintain the purity of water in
artificial reservoirs, though he mistook the rationale of its influence,
which he ascribed to the elemental "salt" supposed by him to play an
important part in all the operations of nature. In his treatise upon
Waters and Fountains, p. 174, of the reprint of 1844, he says: "And in
special, thou shalt note one point, the which is understood of few: that
is to say, that the leaves of the trees which fall upon the parterre,
and the herbs growing beneath, and singularly the fruits, if any there
be upon the trees, being decayed, the waters of the parterre shall draw
unto them the salt of the said fruits, leaves, and herbs, the which
shall greatly better the water of thy fountains, and hinder the
putrefaction thereof."
[89] Between the years 1851 and 1853, both inclusive, the United States
exported 2,665,857 pounds of beeswax, besides a considerable quantity
employed in the manufacture of candles for exportation. This is an
average of more than 330,000 pounds per year. The census of 1850 gave
the total production of wax and honey for that year at 14,853,128
pounds. In 1860, it amounted to 26,370,813 pounds, the increase being
partly due to the introduction of improved races of bees from Italy and
Switzerland.--BIGELOW, _Les États Unis en 1863_, p. 376.
[90] A few years ago, a laborer, employed at a North American port in
discharging a cargo of hides from the opposite extremity of the
continent, was fatally poisoned by the bite or the sting of an unknown
insect, which ran out from a hide he was handling.
[91] In many insects, some of the stages of life regularly continue for
several years, and they may, under peculiar circumstances, be almost
indefinitely prolonged. Dr. Dwight mentions the following remarkable
case of this sort, which may be new to many readers: "While I was here
[at Williamstown, Mass.], Dr. Fitch showed me an insect, about an inch
in length, of a brown color tinged with orange, with two antennæ, not
unlike a rosebug. This insect came out of a tea table, made of the
boards of an apple tree." Dr. Dwight examined the table, and found the
"cavity whence the insect had emerged into the light," to be "about two
inches in length, nearly horizontal, and inclining upward very little,
except at the mouth. Between the hole, and the outside of the leaf of
the table, there were forty grains of the wood." It was supposed that
the sawyer and the cabinet maker must have removed at least thirteen
grains more, and the table had been in the possession of its proprietor
for twenty years.
[92] It does not appear to be quite settled whether the termites of
France are indigenous or imported. See QUATREFAGES, _Souvenirs d'un
Naturaliste_, ii, pp. 400, 542, 543.
[93] I have seen the larva of the dragon fly in an aquarium, bite off
the head of a young fish as long as itself.
[94] Insects and fish--which prey upon and feed each other--are the only
forms of animal life that are numerous in the native woods, and their
range is, of course, limited by the extent of the waters. The great
abundance of the trout, and of other more or less allied genera in the
lakes of Lapland, seems to be due to the supply of food provided for
them by the swarms of insects which in the larva state inhabit the
waters, or, in other stages of their life, are accidentally swept into
them. All travellers in the north of Europe speak of the gnat and the
mosquito as very serious drawbacks upon the enjoyments of the summer
tourist, who visits the head of the Gulf of Bothnia to see the midnight
sun, and the brothers Læstadius regard them as one of the great plagues
of sub-Arctic life. "The persecutions of these insects," says Lars Levi
Læstadius [_Culex pipiens_, _Culex reptans_, and _Culex pulicaris_],
"leave not a moment's peace, by day or night, to any living creature.
Not only man, but cattle, and even birds and wild beasts, suffer
intolerably from their bite." He adds in a note, "I will not affirm that
they have ever devoured a living man, but many young cattle, such as
lambs and calves, have been worried out of their lives by them. All the
people of Lapland declare that young birds are killed by them, and this
is not improbable, for birds are scarce after seasons when the midge,
the gnat, and the mosquito are numerous."--_Om Uppodlingar i
Lappmarken_, p. 50.
Petrus Læstadius makes similar statements in his _Journal för första
året_, p. 285.
[95] It is very questionable whether there is any foundation for the
popular belief in the hostility of swine and of deer to the rattlesnake,
and careful experiments as to the former quadruped seem to show that the
supposed enmity is wholly imaginary. Observing that the starlings,
_stornelli_, which bred in an old tower in Piedmont, carried something
from their nests and dropped it upon the ground, about as often as they
brought food to their young, I watched their proceedings, and found
every day lying near the tower numbers of dead or dying slowworms, and,
in a few cases, small lizards, which had, in every instance, lost about
two inches of the tail. This part I believe the starlings gave to their
nestlings, and threw away the remainder.
[96] Russell denies the existence of poisonous snakes in Northern Syria,
and states that the last instance of death known to have occurred from
the bite of a serpent near Aleppo took place a hundred years before his
time. In Palestine, the climate, the thinness of population, the
multitude of insects and of lizards, all circumstances, in fact, seem
very favorable to the multiplication of serpents, but the venomous
species, at least, are extremely rare, if at all known, in that country.
I have, however, been assured by persons very familiar with Mount
Lebanon, that cases of poisoning from the bite of snakes had occurred
within a few years, near Hasbeiyeh, and at other places on the southern
declivities of Lebanon and Hermon. In Egypt, on the other hand, the
cobra, the asp, and the cerastes are as numerous as ever, and are much
dreaded by all the natives, except the professional snake charmers. See
_Appendix_, No. 18.
[97] I use _whale_ not in a technical sense, but as a generic term for
all the large inhabitants of the sea popularly grouped under that name.
[98] From the narrative of Ohther, introduced by King Alfred into his
translation of Orosius, it is clear that the Northmen pursued the whale
fishery in the ninth century, and it appears, both from the poem called
The Whale, in the Codex Exoniensis, and from the dialogue with the
fisherman in the Colloquies of Aelfric, that the Anglo-Saxons followed
this dangerous chase at a period not much later. I am not aware of any
evidence to show that any of the Latin nations engaged in this fishery
until a century or two afterward, though it may not be easy to disprove
their earlier participation in it. In mediæval literature, Latin and
Romance, very frequent mention is made of a species of vessel called in
Latin, _baleneria_, _balenerium_, _balenerius_, _balaneria_, etc.; in
Catalan, _balener_; in French, _balenier_; all of which words occur in
many other forms. The most obvious etymology of these words would
suggest the meaning, _whaler_, _baleinier_; but some have supposed that
the name was descriptive of the great size of the ships, and others have
referred it to a different root. From the fourteenth century, the word
occurs oftener, perhaps, in old Catalan, than in any other language; but
Capmany does not notice the whale fishery as one of the maritime
pursuits of the very enterprising Catalan people, nor do I find any of
the products of the whale mentioned in the old Catalan tariffs. The
_whalebone_ of the mediæval writers, which is described as very white,
is doubtless the ivory of the walrus or of the narwhale.
[99] In consequence of the great scarcity of the whale, the use of coal
gas for illumination, the substitution of other fatty and oleaginous
substances, such as lard, palm oil, and petroleum, for right-whale oil
and spermaceti, the whale fishery has rapidly fallen off within a few
years. The great supply of petroleum, which is much used for lubricating
machinery as well as for numerous other purposes, has produced a more
perceptible effect on the whale fishery than any other single
circumstance. According to Bigelow, _Les États Unis en 1863_, p. 346,
the American whaling fleet was diminished by 29 in 1858, 57 in 1860, 94
in 1861, and 65 in 1862. The present number of American ships employed
in that fishery is 353.
[100] The Origin and History of the English Language, &c., pp. 423, 424.
[101] Among the unexpected results of human action, the destruction or
multiplication of fish, as well as of other animals, is a not unfrequent
occurrence. I shall have occasion to mention on a following page the
extermination of the fish in a Swedish river by a flood occasioned by
the sudden discharge of the waters of a pond. Williams, in his _History
of Vermont_, i, p. 149, quoted in Thompson's _Natural History of
Vermont_, p. 142, records a case of the increase of trout from an
opposite cause. In a pond formed by damming a small stream to obtain
water power for a sawmill, and covering one thousand acres of primitive
forest, the increased supply of food brought within reach of the fish
multiplied them to that degree, that, at the head of the pond, where, in
the spring, they crowded together in the brook which supplied it, they
were taken by the hands at pleasure, and swine caught them without
difficulty. A single sweep of a small scoopnet would bring up half a
bushel, carts were filled with them as fast as if picked up on dry land,
and in the fishing season they were commonly sold at a shilling
(eightpence halfpenny, or about seventeen cents) a bushel. The increase
in the size of the trout was as remarkable as the multiplication of
their numbers.
[102] BABINET, _Études et Lectures_, ii, pp. 108, 110.
[103] THOMPSON, _Natural History of Vermont_, p. 38, and Appendix,
p. 13. There is no reason to believe that the seal breeds in Lake
Champlain, but the individual last taken there must have been some
weeks, at least, in its waters. It was killed on the ice in the widest
part of the lake, on the 23d of February, thirteen days after the
surface was entirely frozen, except the usual small cracks, and a month
or two after the ice closed at all points north of the place where the
seal was found.
[104] See page 89, note, _ante_.
[105] According to Hartwig, the United Provinces of Holland had, in
1618, three thousand herring busses and nine thousand vessels engaged in
the transport of these fish to market. The whole number of persons
employed in the Dutch herring fishery was computed at 200,000.
In the latter part of the eighteenth century, this fishery was most
successfully prosecuted by the Swedes, and in 1781, the town of
Gottenburg alone exported 136,649 barrels, each containing 1,200
herrings, making a total of about 164,000,000; but so rapid was the
exhaustion of the fish, from this keen pursuit, that in 1799 it was
found necessary to prohibit the exportation of them altogether.--_Das
Leben des Meeres_, p. 182.
In 1855, the British fisheries produced 900,000 barrels, or enough to
supply a fish to every human inhabitant of the globe.
On the shores of Long Island Sound, the white fish, a species of herring
too bony to be easily eaten, is used as manure in very great quantities.
Ten thousand are employed as a dressing for an acre, and a single net
has sometimes taken 200,000 in a day.--DWIGHT's _Travels_, ii, pp. 512,
515.
[106] The indiscriminate hostility of man to inferior forms of animated
life is little creditable to modern civilization, and it is painful to
reflect that it becomes keener and more unsparing in proportion to the
refinement of the race. The savage slays no animal, not even the
rattlesnake, wantonly; and the Turk, whom we call a barbarian, treats
the dumb beast as gently as a child. One cannot live many weeks in
Turkey without witnessing touching instances of the kindness of the
people to the lower animals, and I have found it very difficult to
induce even the boys to catch lizards and other reptiles for
preservation as specimens. See _Appendix_, No. 19.
The fearless confidence in man, so generally manifested by wild animals
in newly discovered islands, ought to have inspired a gentler treatment
of them; but a very few years of the relentless pursuit, to which they
are immediately subjected, suffice to make them as timid as the wildest
inhabitants of the European forest. This timidity, however, may easily
be overcome. The squirrels introduced by Mayor Smith into the public
parks of Boston are so tame as to feed from the hands of passengers, and
they not unfrequently enter the neighboring houses.
[107] A fact mentioned by Schubert--and which in its causes and many of
its results corresponds almost precisely with those connected with the
escape of Barton Pond in Vermont, so well known to geological
students--is important, as showing that the diminution of the fish in
rivers exposed to inundations is chiefly to be ascribed to the
mechanical action of the current, and not mainly, as some have supposed,
to changes of temperature occasioned by clearing. Our author states
that, in 1796, a terrible inundation was produced in the Indalself,
which rises in the Storsjö in Jemtland, by drawing off into it the
waters of another lake near Ragunda. The flood destroyed houses and
fields; much earth was swept into the channel, and the water made turbid
and muddy; the salmon and the smaller fish forsook the river altogether,
and never returned. The banks of the river have never regained their
former solidity, and portions of their soil are still continually
falling into the water.--_Resa genom Sverge_, ii, p. 51.
[108] WITTWER, _Physikalische Geographie_, p. 142.
[109] To vary the phrase, I make occasional use of _animalcule_, which,
as a popular designation, embraces all microscopic organisms. The name
is founded on the now exploded supposition that all of them are
animated, which was the general belief of naturalists when attention was
first drawn to them. It was soon discovered that many of them were
unquestionably vegetable, and there are numerous genera the true
classification of which is matter of dispute among the ablest observers.
There are cases in which objects formerly taken for living animalcules
turn out to be products of the decomposition of matter once animated,
and it is admitted that neither spontaneous motion nor even apparent
irritability are sure signs of animal life.
[110] See an interesting report on the coral fishery, by Sant' Agabio,
Italian Consul-General at Algiers, in the _Bollettino Consolare_,
published by the Department of Foreign Affairs, 1862, pp. 139, 151, and
in the _Annali di Agricoltura, Industria e Commercio_, No. ii, pp. 360,
373.
[111] The fermentation of liquids, and in many cases the decomposition
of semi-solids, formerly supposed to be owing purely to chemical action,
are now ascertained to be due to vital processes of living minute
organisms both vegetable and animal, and consequently to physiological,
as well as to chemical forces. Even alcohol is stated to be an animal
product. See an interesting article by Auguste Laugel on the recent
researches of Pasteur, in the _Revue des Deux Mondes_, for September
15th, 1863.
[112] The recorded evidence in support of the proposition in the text
has been collected by L. F. Alfred Maury, in his _Histoire des grandes
Forêts de la Gaule et de l'ancienne France_, and by Becquerel, in his
important work, _Des climats et de l'Influence qu'exercent les Sols
boisés et non boisés_, livre ii, chap. i to iv.
We may rank among historical evidences on this point, if not technically
among historical records, old geographical names and terminations
etymologically indicating forest or grove, which are so common in many
parts of the Eastern Continent now entirely stripped of woods--such as,
in Southern Europe, Breuil, Broglio, Brolio, Brolo; in Northern, Brühl,
-wald, -wold, -wood, -shaw, -skeg, and -skov.
[113] The island of Madeira, whose noble forests were devastated by fire
not long after its colonization by European settlers, derives its name
from the Portuguese word for wood.
[114] Browsing animals, and most of all the goat, are considered by
foresters as more injurious to the growth of young trees, and,
therefore, to the reproduction of the forest, than almost any other
destructive cause. "According to Beatson's _Saint Helena_, introductory
chapter, and Darwin's _Journal of Researches in Geology and Natural
History_, pp. 582, 583," says Emsmann, in the notes to his translation
of Foissac, p. 654, "it was the goats which destroyed the beautiful
forests that, three hundred and fifty years ago, covered a continuous
surface of not less than two thousand acres in the interior of the
island [of St. Helena], not to mention scattered groups of trees. Darwin
observes: 'During our stay at Valparaiso, I was most positively assured
that sandal wood formerly grew in abundance on the island of Juan
Fernandez, but that this tree had now become entirely extinct there,
having been extirpated by the goats which early navigators had
introduced. The neighboring islands, to which goats have not been
carried, still abound in sandal wood.'"
In the winter, the deer tribe, especially the great American moose deer,
subsists much on the buds and young sprouts of trees; yet--though from
the destruction of the wolves or from some not easily explained cause,
these latter animals have recently multiplied so rapidly in some parts
of North America, that, not long since, four hundred of them are said to
have been killed, in one season, on a territory in Maine not comprising
more than one hundred and fifty square miles--the wild browsing
quadrupeds are rarely, if ever, numerous enough in regions uninhabited
by man to produce any sensible effect on the condition of the forest. A
reason why they are less injurious than the goat to young trees may be
that they resort to this nutriment only in the winter, when the grasses
and shrubs are leafless or covered with snow, whereas the goat feeds
upon buds and young shoots principally in the season of growth. However
this may be, the natural law of consumption and supply keeps the forest
growth, and the wild animals which live on its products, in such a state
of equilibrium as to insure the indefinite continuance of both, and the
perpetuity of neither is endangered until man, who is above natural law,
interferes and destroys the balance.
When, however, deer are bred and protected in parks, they multiply like
domestic cattle, and become equally injurious to trees. "A few years
ago," says Clavé, "there were not less than two thousand deer of
different ages in the forest of Fontainebleau. For want of grass, they
are driven to the trees, and they do not spare them. * * It is
calculated that the browsing of these animals, and the consequent
retardation of the growth of the wood, diminishes the annual product
of the forest to the amount of two hundred thousand cubic feet per
year, * * and besides this, the trees thus mutilated are soon exhausted
and die. The deer attack the pines, too, tearing off the bark in long
strips, or rubbing their heads against them when shedding their horns;
and sometimes, in groves of more than a hundred hectares, not one pine
is found uninjured by them."--_Revue des Deux Mondes_, Mai, 1863, p.
157. See also _Appendix_, No. 21.
Beckstein computes that a park of 2,500 acres, containing 250 acres of
marsh, 250 of fields and meadows, and the remaining 2,000 of wood, may
keep 364 deer of different species, 47 wild boars, 200 hares, 100
rabbits, and an indefinite number of pheasants. These animals would
require, in winter, 123,000 pounds of hay, and 22,000 pounds of
potatoes, besides what they would pick up themselves. The natural forest
most thickly peopled with wild animals would not, in temperate climates,
contain, upon the average, one tenth of these numbers to the same extent
of surface.
[115] Even the volcanic dust of Etna remains very long unproductive.
Near Nicolosi is a great extent of coarse black sand, thrown out in
1669, which, for almost two centuries, lay entirely bare, and can be
made to grow plants only by artificial mixtures and much labor.
The increase in the price of wines, in consequence of the diminution of
the product from the grape disease, however, has brought even these
ashes under cultivation. "I found," says Waltershausen, referring to the
years 1861-'62, "plains of volcanic sand and half-subdued lava streams,
which twenty years ago lay utterly waste, now covered with fine
vineyards. The ashfield of ten square miles above Nicolosi, created by
the eruption of 1669, which was entirely barren in 1835, is now planted
with vines almost to the summits of Monte Rosso, at a height of three
thousand feet."--_Ueber den Sicilianischen Ackerbau_, p. 19.
[116] _A Relation of a Journey Begun An. Dom._ 1610, lib. 4, p. 260,
edition of 1627. The testimony of Sandys on this point is confirmed by
that of Pighio, Braccini, Magliocco, Salimbeni, and Nicola di Rubeo, all
cited by Roth, _Der Vesuv._, p. 9. There is some uncertainty about the
date of the last eruption previous to the great one of 1631. Ashes,
though not lava, appear to have been thrown out about the year 1500, and
some chroniclers have recorded an eruption in the year 1306; but this
seems to be an error for 1036, when a great quantity of lava was
ejected. In 1139, ashes were thrown out for many days. I take those
dates from the work of Roth just cited.
[117] Except upon the banks of rivers or of lakes, the woods of the
interior of North America, far from the habitations of man, are almost
destitute of animal life. Dr. Newberry, describing the vast forests of
the yellow pine of the West, _Pinus ponderosa_, remarks: "In the arid
and desert regions of the interior basin, we made whole days' marches in
forests of yellow pine, of which neither the monotony was broken by
other forms of vegetation, nor its stillness by the flutter of a bird or
the hum of an insect."--_Pacific Railroad Report_, vol. vi, 1857. Dr.
NEWBERRY's _Report on Botany_, p. 37.
The wild fruit and nut trees, the Canada plum, the cherries, the many
species of walnut, the butternut, the hazel, yield very little,
frequently nothing, so long as they grow in the woods; and it is only
when the trees around them are cut down, or when they grow in pastures,
that they become productive. The berries, too--the strawberry, the
blackberry, the raspberry, the whortleberry, scarcely bear fruit at all
except in cleared ground.
The North American Indians did not inhabit the interior of the forests.
Their settlements were upon the shores of rivers and lakes, and their
weapons and other relics are found only in the narrow open grounds which
they had burned over and cultivated, or in the margin of the woods
around their villages.
The rank forests of the tropics are as unproductive of human aliment as
the less luxuriant woods of the temperate zone. In Strain's unfortunate
expedition across the great American isthmus, where the journey lay
principally through thick woods, several of the party died of
starvation, and for many days the survivors were forced to subsist on
the scantiest supplies of unnutritious vegetables perhaps never before
employed for food by man. See the interesting account of that expedition
in _Harper's Magazine_ for March, April, and May, 1855.
Clavé, as well as many earlier writers, supposes that primitive man
derived his nutriment from the spontaneous productions of the wood. "It
is to the forests," says he, "that man was first indebted for the means
of subsistence. Exposed alone, without defence, to the rigor of the
seasons, as well as to the attacks of animals stronger and swifter than
himself, he found in them his first shelter, drew from them his first
weapons. In the first period of humanity, they provided for all his
wants: they furnished him wood for warmth, fruits for food, garments to
cover his nakedness, arms for his defence."--_Études sur l'Économie
Forestière_, p. 13.
But the history of savage life, as far as it is known to us, presents
man in that condition as inhabiting only the borders of the forest and
the open grounds that skirt the waters and the woods, and as finding
only there the aliments which make up his daily bread.
[118] The origin of the great natural meadows, or prairies as they are
called, of the valley of the Mississippi, is obscure. There is, of
course, no historical evidence on the subject, and I believe that
remains of forest vegetation are seldom or never found beneath the
surface, even in the _sloughs_, where the perpetual moisture would
preserve such remains indefinitely. The want of trees upon them has been
ascribed to the occasional long-continued droughts of summer, and the
excessive humidity of the soil in winter; but it is, in very many
instances, certain that, by whatever means the growth of forests upon
them was first prevented or destroyed, the trees have been since kept
out of them only by the annual burning of the grass, by grazing animals,
or by cultivation. The groves and belts of trees which are found upon
the prairies, though their seedlings are occasionally killed by drought,
or by excess of moisture, extend themselves rapidly over them when the
seeds and shoots are protected against fire, cattle, and the plough. The
prairies, though of vast extent, must be considered as a local, and, so
far as our present knowledge extends, abnormal exception to the law
which clothes all suitable surfaces with forest; for there are many
parts of the United States--Ohio, for example--where the physical
conditions appear to be nearly identical with those of the States lying
farther west, but where there were comparatively few natural meadows.
The prairies were the proper feeding grounds of the bison, and the vast
number of those animals is connected, as cause or consequence, with the
existence of those vast pastures. The bison, indeed, could not convert
the forest into a pasture, but he would do much to prevent the pasture
from becoming a forest.
There is positive evidence that some of the American tribes possessed
large herds of domesticated bisons. See HUMBOLDT, _Ansichten der Natur_,
i, pp. 71-73. What authorizes us to affirm that this was simply the wild
bison reclaimed, and why may we not, with equal probability, believe
that the migratory prairie buffalo is the progeny of the domestic animal
run wild?
There are, both on the prairies, as in Wisconsin, and in deep forests,
as in Ohio, extensive remains of a primitive people, who must have been
more numerous and more advanced in art than the present Indian tribes.
There can be no doubt that the woods where such earthworks are found in
Ohio were cleared by them, and that the vicinity of these fortresses or
temples was inhabited by a large population. Nothing forbids the
supposition that the prairies were cleared by the same or a similar
people, and that the growth of trees upon them has been prevented by
fires and grazing, while the restoration of the woods in Ohio may be due
to the abandonment of that region by its original inhabitants. The
climatic conditions unfavorable to the spontaneous growth of trees on
the prairies may be an effect of too extensive clearings, rather than a
cause of the want of woods. See _Appendix_, No. 22.
[119] In many parts of the North American States, the first white
settlers found extensive tracts of thin woods, of a very park-like
character, called "oak openings," from the predominance of different
species of that tree upon them. These were the semi-artificial pasture
grounds of the Indians, brought into that state, and so kept, by partial
clearing, and by the annual burning of the grass. The object of this
operation was to attract the deer to the fresh herbage which sprang up
after the fire. The oaks bore the annual scorching, at least for a
certain time; but if it had been indefinitely continued, they would very
probably have been destroyed at last. The soil would have then been much
in the prairie condition, and would have needed nothing but grazing for
a long succession of years to make the resemblance perfect. That the
annual fires alone occasioned the peculiar character of the oak
openings, is proved by the fact, that as soon as the Indians had left
the country, young trees of many species sprang up and grew luxuriantly
upon them. See a very interesting account of the oak openings in
DWIGHT's _Travels_, iv, pp. 58-63.
[120] The practice of burning over woodland, at once to clear and manure
the ground, is called in Swedish _svedjande_, a participial noun from
the verb _att svedja_, to burn over. Though used in Sweden as a
preparation for crops of rye or other grain, it is employed in Lapland
more frequently to secure an abundant growth of pasturage, which follows
in two or three years after the fire; and it is sometimes resorted to as
a mode of driving the Laplanders and their reindeer from the vicinity of
the Swedish backwoodsman's grass grounds and haystacks, to which they
are dangerous neighbors. The forest, indeed, rapidly recovers itself,
but it is a generation or more before the reindeer moss grows again.
When the forest consists of pine, _tall_, the ground, instead of being
rendered fertile by this process, becomes hopelessly barren, and for a
long time afterward produces nothing but weeds and briers.--LÆSTADIUS,
_Om Uppodlingar i Lappmarken_, p. 15. See also SCHUBERT, _Resa i
Sverge_, ii, p. 375.
In some parts of France this practice is so general that Clavé says: "In
the department of Ardennes it (_le sartage_) is the basis of
agriculture. The northern part of the department, comprising the
arrondissements of Rocroi and Mézières, is covered by steep wooded
mountains with an argillaceous, compact, moist and cold soil; it is
furrowed by three valleys, or rather three deep ravines, at the bottom
of which roll the waters of the Meuse, the Semoy, and the Sormonne, and
villages show themselves wherever the walls of the valleys retreat
sufficiently from the rivers to give room to establish them. Deprived of
arable soil, since the nature of the ground permits neither regular
clearing nor cultivation, the peasant of the Ardennes, by means of
burning, obtains from the forest a subsistence which, without this
resource, would fail him. After the removal of the disposable wood, he
spreads over the soil the branches, twigs, briars, and heath, sets fire
to them in the dry weather of July and August, and sows in September a
crop of rye, which he covers by a light ploughing. Thus prepared, the
ground yields from seventeen to twenty bushels an acre, besides a ton
and a half or two tons of straw of the best quality for the manufacture
of straw hats."--CLAVÉ, _Études sur l'Économie Forestière_, p. 21.
Clavé does not expressly condemn the _sartage_, which indeed seems the
only practicable method of obtaining crops from the soil he describes,
but, as we shall see hereafter, it is regarded by most writers as a
highly pernicious practice.
[121] The remarkable mounds and other earthworks constructed in the
valley of the Ohio and elsewhere in the territory of the United States,
by a people apparently more advanced in culture than the modern Indian,
were overgrown with a dense clothing of forest when first discovered by
the whites. But though the ground where they were erected must have been
occupied by a large population for a considerable length of time, and
therefore entirely cleared, the trees which grew upon the ancient
fortresses and the adjacent lands were not distinguishable in species,
or even in dimensions and character of growth, from the neighboring
forests, where the soil seemed never to have been disturbed. This
apparent exception to the law of change of crop in natural forest growth
was ingeniously explained by General Harrison's suggestion, that the
lapse of time since the era of the mound builders was so great as to
have embraced several successive generations of trees, and occasioned,
by their rotation, a return to the original vegetation.
The successive changes in the spontaneous growth of the forest, as
proved by the character of the wood found in bogs, is not unfrequently
such as to suggest the theory of a considerable change of climate during
the human period. But the laws which govern the germination and growth
of forest trees must be further studied, and the primitive local
conditions of the sites where ancient woods lie buried must be better
ascertained, before this theory can be admitted upon the evidence in
question. In fact, the order of succession--for a rotation or
alternation is not yet proved--may move in opposite directions in
different countries with the same climate and at the same time. Thus in
Denmark and in Holland the spike-leaved firs have given place to the
broad-leaved beech, while in Northern Germany the process has been
reversed, and evergreens have supplanted the oaks and birches of
deciduous foliage. The principal determining cause seems to be the
influence of light upon the germination of the seeds and the growth of
the young tree. In a forest of firs, for instance, the distribution of
the light and shade, to the influence of which seeds and shoots are
exposed, is by no means the same as in a wood of beeches or of oaks, and
hence the growth of different species will be stimulated in the two
forests. See BERG, _Das Verdrängen der Laubwälder im Nördlichen
Deutschland_, 1844. HEYER, _Das Verhalten der Waldbäume gegen Licht und
Schatten_, 1852. STARING, _De Bodem van Nederland_, 1856, i, pp.
120-200. VAUPELL, _Om Bögens Indvandring i de Danske Skove_, 1857.
KNORR, _Studien über die Buchen-Wirthschaft_, 1863.
[122] There are, in Northern Italy and in Switzerland, joint-stock
companies which insure against damage by hail, as well as by fire and
lightning. Between the years 1854 and 1861, a single one of these
companies, La Riunione Adriatica, paid, for damage by hail in Piedmont,
Venetian Lombardy, and the Duchy of Parma, above 6,500,000 francs, or
nearly $200,000 per year.
[123] The _paragrandine_, or, as it is called in French, the
_paragrêle_, is a species of conductor by which it has been hoped to
protect the harvests in countries particularly exposed to damage by
hail. It was at first proposed to employ for this purpose poles
supporting sheaves of straw connected with the ground by the same
material; but the experiment was afterward tried in Lombardy on a large
scale, with more perfect electrical conductors, consisting of poles
secured to the top of tall trees and provided with a pointed wire
entering the ground and reaching above the top of the pole. It was at
first thought that this apparatus, erected at numerous points over an
extent of several miles, was of some service as a protection against
hail, but this opinion was soon disputed, and does not appear to be
supported by well-ascertained facts. The question of a repetition of the
experiment over a wide area has been again agitated within a very few
years in Lombardy; but the doubts expressed by very able physicists as
to its efficacy, and as to the point whether hail is an electrical
phenomenon, have discouraged its advocates from attempting it.
[124] _Cenni sulla Importanza e Coltura dei Boschi_, p. 6.
[125] _Memoria sui Boschi, etc._, p. 44.
[126] _Travels in Italy_, chap. iii.
[127] _Le Alpi che cingono l'Italia_, i, p. 377.
[128] "Long before the appearance of man, * * * they [the forests] had
robbed the atmosphere of the enormous quantity of carbonic acid it
contained, and thereby transformed it into respirable air. Trees heaped
upon trees had already filled up the ponds and marshes, and buried with
them in the bowels of the earth--to restore it to us after thousands of
ages in the form of bituminous coal and of anthracite--the carbon which
was destined to become, by this wonderful condensation, a precious store
of future wealth."--CLAVÉ, _Études sur l'Économie Forestière_, p. 13.
This opinion of the modification of the atmosphere by vegetation is
contested.
[129] Schacht ascribes to the forest a specific, if not a measurable,
influence upon the constitution of the atmosphere. "Plants imbibe from
the air carbonic acid and other gaseous or volatile products exhaled by
animals or developed by the natural phenomena of decomposition. On the
other hand, the vegetable pours into the atmosphere oxygen, which is
taken up by animals and appropriated by them. The tree, by means of its
leaves and its young herbaceous twigs, presents a considerable surface
for absorption and evaporation; it abstracts the carbon of carbonic
acid, and solidifies it in wood, fecula, and a multitude of other
compounds. The result is that a forest withdraws from the air, by its
great absorbent surface, much more gas than meadows or cultivated
fields, and exhales proportionally a considerably greater quantity of
oxygen. The influence of the forests on the chemical composition of the
atmosphere is, in a word, of the highest importance."--_Les Arbres_, p.
111. See _Appendix_, No. 23.
[130] Composition, texture and color of soil are important elements to
be considered in estimating the effects of the removal of the forest
upon its thermoscopic action. "Experience has proved," says Becquerel,
"that when the soil is bared, it becomes more or less heated [by the
rays of the sun] according to the nature and the color of the particles
which compose it, and according to its humidity, and that, in the
refrigeration resulting from radiation, we must take into the account
the conducting power of those particles also. Other things being equal,
silicious and calcareous sands, compared in equal volumes with different
argillaceous earths, with calcareous powder or dust, with humus, with
arable and with garden earth, are the soils which least conduct heat. It
is for this reason that sandy ground, in summer, maintains a high
temperature even during the night. We may hence conclude that when a
sandy soil is stripped of wood, the local temperature will be raised.
After the sands follow successively argillaceous, arable, and garden
ground, then humus, which occupies the lowest rank. If we represent the
power of calcareous sand to retain heat by 100, we have, according to
Schubler,
For [silicious?] sand 95.6
" arable calcareous soil 74.8
" argillaceous earth 68.4
" garden earth 64.8
" humus 49.0
"The retentive power of humus, then, is but half as great as that of
calcareous sand. We will add that the power of retaining heat is
proportional to the density. It has also a relation to the magnitude of
the particles. It is for this reason that ground covered with silicious
pebbles cools more slowly than silicious sand, and that pebbly soils are
best suited to the cultivation of the vine, because they advance the
ripening of the grape more rapidly than chalky and clayey earths, which
cool quickly. Hence we see that in examining the calorific effects of
clearing forests, it is important to take into account the properties of
the soil laid bare."--BECQUEREL, _Des Climats et des Sols boisés_, p.
137.
[131] "The Washington elm at Cambridge--a tree of no extraordinary
size--was some years ago estimated to produce a crop of seven millions
of leaves, exposing a surface of two hundred thousand square feet, or
about five acres of foliage."--GRAY, _First Lessons in Botany and
Vegetable Physiology_, as quoted by COULTAS, _What may be learned from a
Tree_, p. 34.
[132] See, on this particular point, and on the general influence of the
forest on temperature, HUMBOLDT, _Ansichten der Natur_, i, 158.
[133] The radiating and refrigerating power of objects by no means
depends on their form alone. Melloni cut sheets of metal into the shape
of leaves and grasses, and found that they produced little cooling
effect, and were not moistened under atmospheric conditions which
determined a plentiful deposit of dew on the leaves of vegetables.
[134] BECQUEREL, _Des Climats, etc., Discours Prélim._ vi.
[135] _Travels_, i, p. 61.
[136] _Le Alpi che cingono l'Italia_, pp. 370, 371.
[137] BERGSÖE, _Reventlovs Virksomhed_, ii, p. 125.
[138] BECQUEREL, _Des Climats, etc._, p. 179.
[139] Ibid., p. 116.
[140] The following well-attested instance of a local change of climate
is probably to be referred to the influence of the forest as a shelter
against cold winds. To supply the extraordinary demand for Italian iron
occasioned by the exclusion of English iron in the time of Napoleon I,
the furnaces of the valleys of Bergamo were stimulated to great
activity. "The ordinary production of charcoal not sufficing to feed the
furnaces and the forges, the woods were felled, the copses cut before
their time, and the whole economy of the forest was deranged. At
Piazzatorre there was such a devastation of the woods, and consequently
such an increased severity of climate, that maize no longer ripened.
An association, formed for the purpose, effected the restoration
of the forest, and maize flourishes again in the fields of
Piazzatorre."--Report by G. ROSA, in _Il Politecnico_, Dicembre, 1861,
p. 614.
Similar ameliorations have been produced by plantations in Belgium. In
an interesting series of articles by Baude, entitled "Les Cotes de la
Manche," in the _Revue des Deux Mondes_, I find this statement: "A
spectator placed on the famous bell tower of the cathedral of Antwerp,
saw, not long since, on the opposite side of the Schelde only a vast
desert plain; now he sees a forest, the limits of which are confounded
with the horizon. Let him enter within its shade. The supposed forest is
but a system of regular rows of trees, the oldest of which is not forty
years of age. These plantations have ameliorated the climate which had
doomed to sterility the soil where they are planted. While the tempest
is violently agitating their tops, the air a little below is still, and
sands far more barren than the plateau of La Hague have been
transformed, under their protection, into fertile fields."--_Revue des
Deux Mondes_, January, 1859, p. 277.
[141] _Cenni sulla Importanza e Coltura dei Boschi_, p. 31.
[142] _La Provence au point de vue des Torrents et des Inondations_, p.
19.
[143] _Ueber die Entwaldung der Gebirge_, p. 28.
[144] BECQUEREL, _Des Climats, etc._, p. 9.
[145] SALVAGNOLI, _Rapporto sul Bonificamento delle Maremme Toscane_,
pp. xli, 124.
[146] _Il Politecnico, Milano, Aprile e Maggio_, 1863, p. 35.
[147] SALVAGNOLI, _Memorie sulle Maremme Toscane_, pp. 213, 214.
[148] Except in the seething marshes of the tropics, where vegetable
decay is extremely rapid, the uniformity of temperature and of
atmospheric humidity renders all forests eminently healthful. See
HOHENSTEIN's observations on this subject, _Der Wald_, p. 41.
There is no question that open squares and parks conduce to the
salubrity of cities, and many observers are of opinion that the trees
and other vegetables with which such grounds are planted contribute
essentially to their beneficial influence. See an article in _Aus der
Natur_, xxii, p. 813.
[149] _Memoria sui Boschi di Lombardia_, p. 45.
[150] _Économie Rurale_, i, p. 22.
[151] ROSSMÄSSLER, _Der Wald_, p. 158.
[152] Ibid., p. 160.
[153] The low temperature of air and soil at which, in the frigid zone,
as well as in warmer latitudes under special circumstances, the
processes of vegetation go on, seems to necessitate the supposition that
all the manifestations of vegetable life are attended with an evolution
of heat. In the United States, it is common to protect ice, in
icehouses, by a covering of straw, which naturally sometimes contains
kernels of grain. These often sprout, and even throw out roots and
leaves to a considerable length, in a temperature very little above the
freezing point. Three or four years since, I saw a lump of very clear
and apparently solid ice, about eight inches long by six thick, on which
a kernel of grain had sprouted in an icehouse, and sent half a dozen or
more very slender roots into the pores of the ice and through the whole
length of the lump. The young plant must have thrown out a considerable
quantity of heat; for though the ice was, as I have said, otherwise
solid, the pores through which the roots passed were enlarged to perhaps
double the diameter of the fibres, but still not so much as to prevent
the retention of water in them by capillary attraction. See _App._ 24.
[154] BECQUEREL, _Des Climats, etc._, pp. 139-141.
[155] Dr. Williams made some observations on this subject in 1789, and
in 1791, but they generally belonged to the warmer months, and I do not
know that any extensive series of comparisons between the temperature of
the ground in the woods and the fields has been attempted in America.
Dr. Williams's thermometer was sunk to the depth of ten inches, and gave
the following results:
+-------------+--------------+--------------+-------------+
| | Temperature | Temperature | |
| TIME. | of ground in | of ground in | Difference. |
| | pasture. | woods. | |
+-------------+--------------+--------------+-------------+
| May 23 | 52 | 46 | 6 |
| " 28 | 57 | 48 | 9 |
| June 15 | 64 | 51 | 13 |
| " 27 | 62 | 51 | 11 |
| July 16 | 62 | 51 | 11 |
| " 30 | 65½ | 55½ | 10 |
| Aug. 15 | 68 | 58 | 10 |
| " 31 | 59½ | 55 | 4½ |
| Sept. 15 | 59½ | 55 | 4½ |
| Oct. 1 | 59½ | 55 | 4½ |
| " 15 | 49 | 49 | 0 |
| Nov. 1 | 43 | 43 | 0 |
| " 16 | 43½ | 43½ | 0 |
+-------------+--------------+--------------+-------------+
On the 14th of January, 1791, in a winter remarkable for its extreme
severity, he found the ground, on a plain open field where the snow had
been blown away, frozen to the depth of three feet and five inches; in
the woods where the snow was three feet deep, and where the soil had
frozen to the depth of six inches before the snow fell, the thermometer,
at six inches below the surface of the ground, stood at 39°. In
consequence of the covering of the snow, therefore, the previously
frozen ground had been thawed and raised to seven degrees above the
freezing point.--WILLIAMS'S _Vermont_, i, p. 74.
Bodies of fresh water, so large as not to be sensibly affected by local
influences of narrow reach or short duration, would afford climatic
indications well worthy of special observation. Lake Champlain, which
forms the boundary between the States of New York and Vermont, presents
very favorable conditions for this purpose. This lake, which drains a
basin of about 6,000 square miles, covers an area, excluding its
islands, of about 500 square miles. It extends from lat. 43° 30' to 45°
20', in very nearly a meridian line, has a mean width of four and a half
miles, with an extreme breadth, excluding bays almost land-locked, of
thirteen miles. Its mean depth is not well known. It is, however, 400
feet deep in some places, and from 100 to 200 in many, and has few
shoals or flats. The climate is of such severity that it rarely fails to
freeze completely over, and to be safely crossed upon the ice, with
heavy teams, for several weeks every winter. THOMPSON (_Vermont_, p. 14,
and Appendix, p. 9) gives the following table of the times of the
complete closing and opening of the ice, opposite Burlington, about the
centre of the lake, and where it is ten miles wide.
+------+-------------+------------+-------+
| Year.| Closing. | Opening. | Days |
| | | |closed.|
+------+-------------+------------+-------+
| 1816 | February 9 | | |
| 1817 | January 29 | April 16 | 78 |
| 1818 | February 2 | April 15 | 72 |
| 1819 | March 4 | April 17 | 44 |
| 1820 |{February 3 | February | } 4 |
| |{March 8 | March 12 | } |
| 1821 | January 15 | April 21 | 95 |
| 1822 | January 24 | March 30 | 75 |
| 1823 | February 7 | April 5 | 57 |
| 1824 | January 22 | February 11| 20 |
| 1825 | February 9 | | |
| 1826 | February 1 | March 24 | 51 |
| 1827 | January 21 | March 31 | 68 |
| 1828 | not closed | | |
| 1829 | January 31 | April | |
| 1832 | February 6 | April 17 | 70 |
| 1833 | February 2 | April 6 | 63 |
| 1834 | February 13 | February 20| 7 |
| 1835 |{January 10 | January 23 | 18 |
| |{February 7 | April 12 | 64 |
| 1836 | January 27 | April 21 | 85 |
| 1837 | January 15 | April 26 | 101 |
| 1838 | February 2 | April 13 | 70 |
| 1839 | January 25 | April 6 | 71 |
| 1840 | January 25 | February 20| 26 |
| 1841 | February 18 | April 19 | 61 |
| 1842 | not closed | | |
| 1843 | February 16 | April 22 | 65 |
| 1844 | January 25 | April 11 | 77 |
| 1845 | February 3 | March 26 | 51 |
| 1846 | February 10 | March 26 | 44 |
| 1847 | February 15 | April 23 | 68 |
| 1848 | February 13 | February 26| 13 |
| 1849 | February 7 | March 23 | 44 |
| 1850 | not closed | | |
| 1851 | February 1 | March 12 | 89 |
| 1852 | January 18 | April 10 | 92 |
+------+-------------+------------+-------+
In 1847, although, at the point indicated, the ice broke up on the 23d
of April, it remained frozen much later at the North, and steamers were
not able to traverse the whole length of the lake until May 6th.
[156] We are not, indeed, to suppose that condensation of vapor and
evaporation of water are going on in the same stratum of air at the same
time, or, in other words, that vapor is condensed into raindrops, and
raindrops evaporated, under the same conditions; but rain formed in one
stratum, may fall through another, where vapor would not be condensed.
Two saturated strata of different temperatures may be brought into
contact in the higher regions, and discharge large raindrops, which, if
not divided by some obstruction, will reach the ground, though passing
all the time through strata which would vaporize them if they were in a
state of more minute division.
[157] It is perhaps too much to say that the influence of trees upon the
wind is strictly limited to the mechanical resistance of their trunks,
branches, and foliage. So far as the forest, by dead or by living
action, raises or lowers the temperature of the air within it, so far it
creates upward or downward currents in the atmosphere above it, and,
consequently, a flow of air toward or from itself. These air streams
have a certain, though doubtless a very small influence on the force and
direction of greater atmospheric movements.
[158] As a familiar illustration of the influence of the forest in
checking the movement of winds, I may mention the well-known fact, that
the sensible cold is never extreme in thick woods, where the motion of
the air is little felt. The lumbermen in Canada and the Northern United
States labor in the woods, without inconvenience, when the mercury
stands many degrees below the zero of Fahrenheit, while in the open
grounds, with only a moderate breeze, the same temperature is almost
insupportable. The engineers and firemen of locomotives, employed on
railways running through forests of any considerable extent, observe
that, in very cold weather, it is much easier to keep up the steam while
the engine is passing through the woods than in the open ground. As soon
as the train emerges from the shelter of the trees the steam gauge
falls, and the stoker is obliged to throw in a liberal supply of fuel to
bring it up again.
Another less frequently noticed fact, due, no doubt, in a great measure
to the immobility of the air, is, that sounds are transmitted to
incredible distances in the unbroken forest. Many instances of this have
fallen under my own observation, and others, yet more striking, have
been related to me by credible and competent witnesses familiar with a
more primitive condition of the Anglo-American world. An acute observer
of natural phenomena, whose childhood and youth were spent in the
interior of one of the newer New England States, has often told me that
when he established his home in the forest, he always distinctly heard,
in still weather, the plash of horses' feet, when they forded a small
brook nearly seven-eighths of a mile from his house, though a portion of
the wood that intervened consisted of a ridge seventy or eighty feet
higher than either the house or the ford.
I have no doubt that, in such cases, the stillness of the air is the
most important element in the extraordinary transmissibility of sound;
but it must be admitted that the absence of the multiplied and confused
noises, which accompany human industry in countries thickly peopled by
man, contributes to the same result. We become, by habit, almost
insensible to the familiar and never-resting voices of civilization in
cities and towns; but the indistinguishable drone, which sometimes
escapes even the ear of him who listens for it, deadens and often quite
obstructs the transmission of sounds which would otherwise be clearly
audible. An observer, who wishes to appreciate that hum of civic life
which he cannot analyze, will find an excellent opportunity by placing
himself on the hill of Capo di Monte at Naples, in the line of
prolongation of the street called Spaccanapoli.
It is probably to the stillness of which I have spoken, that we are to
ascribe the transmission of sound to great distances at sea in calm
weather. In June, 1853, I and my family were passengers on board a ship
of war bound up the Ægean. On the evening of the 27th of that month, as
we were discussing, at the tea table, some observations of Humboldt on
this subject, the captain of the ship told us that he had once heard a
single gun at sea at the distance of ninety nautical miles. The nest
morning, though a light breeze had sprung up from the north, the sea was
of glassy smoothness when we went on deck. As we came up, an officer
told us that he had heard a gun at sunrise, and the conversation of the
previous evening suggested the inquiry whether it could have been fired
from the combined French and English fleet then lying at Beshika Bay.
Upon examination of our position we were found to have been, at sunrise,
ninety sea miles from that point. We continued beating up northward, and
between sunrise and twelve o'clock meridian of the 28th, we had made
twelve miles northing, reducing our distance from Beshika Bay to
seventy-eight sea miles. At noon we heard several guns so distinctly
that we were able to count the number. On the 29th we came up with the
fleet, and learned from an officer who came on board that a royal salute
had been fired at noon on the 28th, in honor of the day as the
anniversary of the Queen of England's coronation. The report at sunrise
was evidently the morning gun, those at noon the salute.
Such cases are rare, because the sea is seldom still, and the
[Greek: kymatôn anêrithmon gelasma] rarely silent, over so great a space
as ninety or even seventy-eight nautical miles. I apply the epithet
_silent_ to [Greek: gelasma] advisedly. I am convinced that Æschylus
meant the audible laugh of the waves, which is indeed of _countless_
multiplicity, not the visible smile of the sea, which, belonging to the
great expanse as one impersonation, is single, though, like the human
smile, made up of the play of many features.
[159] "The presence of watery vapor in the air is general. * * *
Vegetable surfaces are endowed with the power of absorbing gases,
vapors, and also, no doubt, the various soluble bodies which are
presented to them. The inhalation of humidity is carried on by the
leaves upon a large scale; the dew of a cold summer night revives the
groves and the meadows, and a single shower of rain suffices to refresh
the verdure of a forest which a long drought had parched."--SCHACHT,
_Les Arbres_, ix, p. 340.
The absorption of the vapor of water by leaves is disputed. "The
absorption of watery vapor by the leaves of plants is, according to
Unger's experiments, inadmissible."--WILHELM, _Der Boden und das
Wasser_, p. 19. If this latter view is correct, the apparently
refreshing effects of atmospheric humidity upon vegetation must be
ascribed to moisture absorbed by the ground from the air and supplied to
the roots. In some recent experiments by Dr. Sachs, a porous flower-pot,
with a plant growing in it, was left unwatered until the earth was dry,
and the plant began to languish. The pot was then placed in a glass case
containing air, which was kept always saturated with humidity, but no
water was supplied, and the leaves of the plant were exposed to the open
atmosphere. The soil in the flower pot absorbed from the air moisture
enough to revive the foliage, and keep it a long time green, but not
enough to promote development of new leaves.--Id., ibid., p. 18.
[160] The experiments of Hales and others, on the absorption and
exhalation of water by vegetables, are of the highest physiological
interest; but observations on sunflowers, cabbages, hops, and single
branches of isolated trees, growing in artificially prepared soils and
under artificial conditions, furnish no trustworthy data for computing
the quantity of water received and given off by the natural wood.
[161] In the primitive forest, except where the soil is too wet for the
dense growth of trees, the ground is generally too thickly covered with
leaves to allow much room for ground mosses. In the more open woods of
Europe, this form of vegetation is more frequent--as, indeed, are many
other small plants of a more inviting character--than in the native
American forest. See, on the cryptogams and wood plants, ROSSMÄSSLER,
_Der Wald_, pp. 33 _et seqq._
[162] Emerson (_Trees of Massachusetts_, p. 493) mentions a maple six
feet in diameter, as having yielded a barrel, or thirty-one and a half
gallons of sap in twenty-four hours, and another, the dimensions of
which are not stated, as having yielded one hundred and seventy-five
gallons in the course of the season. The _Cultivator_, an American
agricultural journal, for June, 1842, states that twenty gallons of sap
were drawn in eighteen hours from a single maple, two and a half feet in
diameter, in the town of Warner, New Hampshire, and the truth of this
account has been verified by personal inquiry made in my behalf. This
tree was of the original forest growth, and had been left standing when
the ground around it was cleared. It was tapped only every other year,
and then with six or eight incisions. Dr. Williams (_History of
Vermont_, i, p. 91) says: "A man much employed in making maple sugar,
found that, for twenty-one days together, a maple tree discharged seven
and a half gallons per day."
An intelligent correspondent, of much experience in the manufacture of
maple sugar, writes me that a second-growth maple, of about two feet in
diameter, standing in open ground, tapped with four incisions, has, for
several seasons, generally run eight gallons per day in fair weather. He
speaks of a very large tree, from which sixty gallons were drawn in the
course of a season, and of another, something more than three feet
through, which made forty-two pounds of wet sugar, and must have yielded
not less than one hundred and fifty gallons.
[163] "The buds of the maple," says the same correspondent, "do not
start till toward the close of the sugar season. As soon as they begin
to swell, the sap seems less sweet, and the sugar made from it is of a
darker color, and with less of the distinctive maple flavor."
[164] "In this region, maples are usually tapped with a three-quarter
inch bit, boring to the depth of one and a half or two inches. In the
smaller trees, one incision only is made, two in those of eighteen
inches in diameter, and four in trees of larger size. Two 3/4-inch holes
in a tree twenty-two inches in diameter = 1/46 of the circumference, and
1/169 of the area of section."
"Tapping does not check the growth, but does injure the quality of the
wood of maples. The wood of trees often tapped is lighter and less dense
than that of trees which have not been tapped, and gives less heat in
burning. No difference has been observed in the starting of the buds of
tapped and untapped trees."--_Same correspondent._
[165] Dr. Rush, in a letter to Jefferson, states the number of maples
fit for tapping on an acre at from thirty to fifty. "This," observes my
correspondent, "is correct with regard to the original growth, which is
always more or less intermixed with other trees; but in second growth,
composed of maples alone, the number greatly exceeds this. I have had
the maples on a quarter of an acre, which I thought about an average of
second-growth 'maple orchards,' counted. The number was found to be
fifty-two, of which thirty-two were ten inches or more in diameter, and,
of course, large enough to tap. This gives two hundred and eight trees
to the acre, one hundred and twenty-eight of which were of proper size
for tapping."
According to the census returns, the quantity of maple sugar made
in the United States in 1850 was 34,253,436 pounds; in 1860, it was
38,863,884 pounds, besides 1,944,594 gallons of molasses. The cane
sugar made in 1850 amounted to 237,133,000 pounds; in 1859, to
302,205,000.--_Preliminary Report on the Eighth Census_, p. 88.
According to Bigelow, _Les États Unis d'Amérique en 1863_, chap. iv, the
sugar product of Louisiana alone for 1862 is estimated at 528,321,500
pounds.
[166] The correspondent already referred to informs me that a black
birch, tapped about noon with two incisions, was found the next morning
to have yielded sixteen gallons. Dr. Williams (_History of Vermont_, i,
p. 91) says: "A large birch, tapped in the spring, ran at the rate of
five gallons an hour when first tapped. Eight or nine days after, it was
found to run at the rate of about two and a half gallons an hour, and at
the end of fifteen days the discharge continued in nearly the same
quantity. The sap continued to flow for four or five weeks, and it was
the opinion of the observers that it must have yielded as much as sixty
barrels [1,890 gallons]."
[167] "The best state of weather for a good run," says my correspondent,
"is clear days, thawing fast in the daytime and freezing well at night,
with a gentle west or northwest wind; though we sometimes have clear,
fine, thawing days followed by frosty nights, without a good run of sap,
I have thought it probable that the irregular flow of sap on different
days in the same season is connected with the variation in atmospheric
pressure; for the atmospheric conditions above mentioned as those most
favorable to a free flow of sap are also those in which the barometer
usually indicates pressure considerably above the mean. With a south or
southeast wind, and in lowering weather, which causes a fall in the
barometer, the flow generally ceases, though the sap sometimes runs till
after the beginning of the storm. With a _gentle_ wind, south of west,
maples sometimes run all night. When this occurs, it is oftenest shortly
before a storm. Last spring, the sap of a sugar orchard in a neighboring
town flowed the greater part of the time for two days and two nights
successively, and did not cease till after the commencement of a rain
storm."
The cessation of the flow of sap at night is perhaps in part to be
ascribed to the nocturnal frost, which checks the melting of the snow,
of course diminishing the supply of moisture in the ground, and
sometimes congeals the strata from which the rootlets suck in water.
From the facts already mentioned, however, and from other well-known
circumstances--such, for example, as the more liberal flow of sap from
incisions on the south side of the trunk--it is evident that the
withdrawal of the stimulating influences of the sun's light and heat is
the principal cause of the suspension of the circulation in the night.
[168] "The flow ceases altogether soon after the buds begin to
swell."--_Letter before quoted._
[169] We might obtain a contribution to an approximate estimate of the
quantity of moisture abstracted by forest vegetation from the earth and
the air, by ascertaining, as nearly as possible, the quantity of wood on
a given area, the proportion of assimilable matter contained in the
fluids of the tree at different seasons of the year, the ages of the
trees respectively, and the quantity of leaf and seed annually shed by
them. The results would, indeed, be very vague, but they might serve to
check or confirm estimates arrived at by other processes. The following
facts are items too loose perhaps to be employed as elements in such a
computation.
Dr. Williams, who wrote when the woods of Northern New England were
generally in their primitive condition, states the number of trees
growing on an acre at from one hundred and fifty to six hundred and
fifty, according to their size and the quality of the soil; the quantity
of wood, at from fifty to two hundred cords, or from 238 to 952 cubic
yards, but adds that on land covered with pines, the quantity of wood
would be much greater. Whether he means to give the entire solid
contents of the tree, or, as is usual in ordinary estimates in New
England, the marketable wood only, the trunks and larger branches, does
not appear. Next to the pine, the maple would probably yield a larger
amount to a given area than any of the other trees mentioned by Dr.
Williams, but mixed wood, in general, measures most. In a good deal of
observation on this subject, the largest quantity of marketable wood I
have ever known cut on an acre of virgin forest was one hundred and four
cords, or 493 cubic yards, and half that amount is considered a very
fair yield. The smaller trees, branches, and twigs would not increase
the quantity more than twenty-five per cent., and if we add as much more
for the roots, we should have a total of about 750 cubic yards. I think
Dr. Williams's estimate too large, though it would fall much below the
product of the great trees of the Mississippi Valley, of Oregon, and of
California. It should be observed that these measurements are those of
the wood as it lies when 'corded' or piled up for market, and exceed the
real solid contents by not less than fifteen per cent.
"In a soil of medium quality," says Clavé, quoting the estimates of
Pfeil, for the climate of Prussia, "the volume of a hectare of pines
twenty years old, would exceed 80 cubic mètres [42½ cubic yards to
the acre]; it would amount to but 24 in a meagre soil. This tree attains
its maximum of mean growth at the age of seventy-five years. At that
age, in the sandy earth of Prussia, it produces annually about 5 cubic
mètres, with a total volume of 311 cubic mètres per hectare [166 cubic
yards per acre]. After this age the volume increases, but the mean rate
of growth diminishes. At eighty years, for instance, the volume is 335
cubic mètres, the annual production 4 only. The beech reaches its
maximum of annual growth at one hundred and twenty years. It then has a
total volume of 633 cubic mètres to the hectare [335 cubic yards to the
acre], and produces 5 cubic mètres per year."--CLAVÉ, _Études_, p. 151.
These measures, I believe, include the entire ligneous product of the
tree, exclusive of the roots, and express the actual solid contents. The
specific gravity of maple wood is stated to be 75. Maple sap yields
sugar at the rate of about one pound _wet_ sugar to three gallons of
sap, and wet sugar is to dry sugar in about the proportion of nineteen
to sixteen. Besides the sugar, there is a small residuum of "sand,"
composed of phosphate of lime, with a little silex, and it is certain
that by the ordinary hasty process of manufacture, a good deal of sugar
is lost; for the drops, condensed from the vapor of the boilers on the
rafters of the rude sheds where the sap is boiled, have a decidedly
sweet taste.
[170] "The elaborated sap, passing out of the leaves, is received into
the inner bark, * * * and a part of what descends finds its way even to
the ends of the roots, and is all along diffused laterally into the
stem, where it meets and mingles with the ascending crude sap or raw
material. So there is no separate circulation of the two kinds of sap;
and no crude sap exists separately in any part of the plant. Even in the
root, where it enters, this mingles at once with some elaborated sap
already there."--GRAY, _How Plants Grow_, § 273.
[171] Ward's tight glazed cases for raising, and especially for
transporting plants, go far to prove that water only circulates through
vegetables, and is again and again absorbed and transpired by organs
appropriated to these functions. Seeds, growing grasses, shrubs, or
trees planted in proper earth, moderately watered and covered with a
glass bell or close frame of glass, live for months and even years, with
only the original store of air and water. In one of Ward's early
experiments, a spire of grass and a fern, which sprang up in a corked
bottle containing a little moist earth introduced as a bed for a snail,
lived and flourished for eighteen years without a new supply of either
fluid. In these boxes the plants grow till the enclosed air is exhausted
of the gaseous constituents of vegetation, and till the water has
yielded up the assimilable matter it held in solution, and dissolved and
supplied to the roots the nutriment contained in the earth in which they
are planted. After this, they continue for a long time in a state of
vegetable sleep, but if fresh air and water be introduced into the
cases, or the plants be transplanted into open ground, they rouse
themselves to renewed life, and grow vigorously, without appearing to
have suffered from their long imprisonment. The water transpired by the
leaves is partly absorbed by the earth directly from the air, partly
condensed on the glass, along which it trickles down to the earth,
enters the roots again, and thus continually repeats the circuit. See
_Aus der Natur_, 21, B. S. 537.
[172] WILHELM, _Der Boden und das Wasser_, p. 18. It is not ascertained
in what proportions the dew is evaporated, and in what it is absorbed by
the earth, in actual nature, but there can be no doubt that the amount
of water taken up by the ground, both from vapor suspended in the air
and from dew, is large. The annual fall of dew in England is estimated
at five inches, but this quantity is much exceeded in many countries
with a clearer sky. "In many of our Algerian campaigns," says Babinet,
"when it was wished to punish the brigandage of the unsubdued tribes, it
was impossible to set their grain fields on fire until a late hour of
the day; for the plants were so wet with the night dew that it was
necessary to wait until the sun had dried them."--_Études et Lectures_,
ii, p. 212.
[173] "It has been concluded that the dry land occupies about 49,800,000
square statute miles. This does not include the recently discovered
tracts of land in the vicinity of the poles, and allowing for yet
undiscovered land (which, however, can only exist in small quantity), if
we assign 51,000,000 to the land, there will remain about 146,000,000 of
square miles for the extent of surface occupied by the ocean."--Sir J.
F. W. HERSCHEL, _Physical Geography_, 1861, p. 19.
It does not appear to which category Herschel assigns the inland seas
and the fresh-water lakes and rivers of the earth; and Mrs. Somerville,
who states that the "dry land occupies an area of 38,000,000 of square
miles," and that "the ocean covers nearly three fourths of the surface
of the globe," is equally silent on this point.--_Physical Geography_,
fifth edition, p. 30. On the following page, Mrs. Somerville, in a note,
cites Mr. Gardner as her authority, and says that, "according to his
computation, the extent of land is about 37,673,000 square British
miles, independently of Victoria Continent; and the sea occupies
110,849,000. Hence the land is to the sea as 1 to 4 nearly." Sir John F.
W. Herschel makes the area of dry land and ocean together 197,000,000
square miles; Mrs. Somerville, or rather Mr. Gardner, 148,522,000. I
suppose Sir John Herschel includes the islands in his aggregate of the
"dry land," and the inland waters under the general designation of the
"ocean," and that Mrs. Somerville excludes both.
[174] It has been observed in Sweden that the spring, in many districts
where the forests have been cleared off, now comes on a fortnight later
than in the last century.--ASBJÖRNSEN, _Om Skovene i Norge_, p. 101.
The conclusion arrived at by Noah Webster, in his very learned and able
paper on the supposed change in the temperature of winter, read before
the Connecticut Academy of Arts and Sciences in 1799, was as follows:
"From a careful comparison of these facts, it appears that the weather,
in modern winters, in the United States, is more inconstant than when
the earth was covered with woods, at the first settlement of Europeans
in the country; that the warm weather of autumn extends further into the
winter months, and the cold weather of winter and spring encroaches upon
the summer; that, the wind being more variable, snow is less permanent,
and perhaps the same remark may be applicable to the ice of the rivers.
These effects seem to result necessarily from the greater quantity of
heat accumulated in the earth in summer since the ground has been
cleared of wood and exposed to the rays of the sun, and to the greater
depth of frost in the earth in winter by the exposure of its uncovered
surface to the cold atmosphere."--_Collection of Papers by_ NOAH
WEBSTER, p. 162.
[175] I have seen, in Northern New England, the surface of the open
ground frozen to the depth of twenty-two inches, in the month of
November, when in the forest earth no frost was discoverable; and later
in the winter, I have known an exposed sand knoll to remain frozen six
feet deep, after the ground in the woods was completely thawed.
[176]
----Det golde Strög i Afrika,
Der Intet voxe kan, da ei det regner,
Og, omvendt, ingen Regn kan falde, da
Der Intet voxer.
PALUDAN-MÜLLER, _Adam Homo_, ii, 408.
[177]
Und Stürme brausen um die Wette
Vom Meer aufs Land, vom Land aufs Meer.
GOETHE, _Faust, Song of the Archangels_.
[178] _Études sur l'Économie Forestière_, pp. 45, 46.
[179] I am not aware of any evidence to show that Malta had any woods of
importance at any time since the cultivation of cotton was introduced
there; and if it is true, as has been often asserted, that its present
soil was imported from Sicily, it can certainly have possessed no
forests since a very remote period. In Sandys's time, 1611, there were
no woods in the island, and it produced little cotton. He describes it
as "a country altogether champion, being no other than a rocke couered
ouer with earth, but two feete deepe where the deepest; hauing but few
trees but such as beare fruite. * * * So that their wood they haue from
Sicilia." They have "an indifferent quantity of cotton wooll, but that
the best of all other."--SANDYS, _Travels_, p. 228.
[180] SCHACHT, _Les Arbres_, p. 412.
[181] _What may be learned from a Tree_, p. 117.
[182] _Der Wald_, p. 13.
[183] _Om Skovene og deres Forhold til National[oe]conomien_, pp.
131-133.
[184] _Om Skovene og om et ordnet Skovbrug i Norge_, p. 106.
[185] _Études et Lectures_, iv. p. 114.
[186] The supposed increase in the frequency and quantity of rain in
Lower Egypt is by no means established. I have heard it disputed on the
spot by intelligent Franks, whose residence in that country began before
the plantations of Mehemet Aali and Ibrahim Pacha, and I have been
assured by them that meteorological observations, made at Alexandria
about the beginning of this century, show an annual fall of rain as
great as is usual at this day. The mere fact, that it did not rain
during the French occupation, is not conclusive. Having experienced a
gentle shower of nearly twenty-four hours' duration in Upper Egypt, I
inquired of the local governor in relation to the frequency of this
phenomenon, and was told by him that not a drop of rain had fallen at
that point for more than two years previous.
The belief in the increase of rain in Egypt rests almost entirely on the
observations of Marshal Marmont, and the evidence collected by him in
1836. His conclusions have been disputed, if not confuted, by Jomard and
others, and are probably erroneous. See, FOISSAC, _Météorologie_, German
translation, pp. 634-639.
It certainly sometimes rains briskly at Cairo, but evaporation is
exceedingly rapid in Egypt--as any one, who ever saw a Fellah woman wash
a napkin in the Nile, and dry it by shaking it a few moments in the air,
can testify; and a heap of grain, wet a few inches below the surface,
would probably dry again without injury. At any rate, the Egyptian
Government often has vast quantities of wheat stored at Boulak, in
uncovered yards through the winter, though it must be admitted that the
slovenliness and want of foresight in Oriental life, public and private,
are such that we cannot infer the safety of any practice followed in the
East, merely from its long continuance.
Grain, however, may be long kept in the open air in climates much less
dry than that of Egypt, without injury, except to the superficial
layers; for moisture does not penetrate to a great depth in a heap of
grain once well dried, and kept well aired. When Louis IX was making his
preparations for his campaign in the East, he had large quantities of
wine and grain purchased in the Island of Cyprus, and stored up, for two
years, to await his arrival. "When we were come to Cyprus," says
Joinville, _Histoire de Saint Louis_, §§ 72, 73, "we found there greate
foison of the Kynge's purveyance. * * The wheate and the barley they had
piled up in greate heapes in the feeldes, and to looke vpon, they were
like vnto mountaynes; for the raine, the whyche hadde beaten vpon the
wheate now a longe whyle, had made it to sproute on the toppe, so that
it seemed as greene grasse. And whanne they were mynded to carrie it to
Egypte, they brake that sod of greene herbe, and dyd finde under the
same the wheate and the barley, as freshe as yf menne hadde but nowe
thrashed it."
[187] _Étude sur les Eaux au point de vue des Inondations_, p. 91.
[188] _Économie Rurale_, ii, chap. xx, § 4, pp. 756-759. See also p.
733.
[189] Jacini, speaking of the great Italian lakes, says: "A large
proportion of the water of the lakes, instead of discharging itself by
the Ticino, the Adda, the Oglio, the Mincio, filters through the
silicious strata which underlie the hills, and follows subterranean
channels to the plain, where it collects in the _fontanili_, and being
thence conducted into the canals of irrigation, becomes a source of
great fertility."--_La Proprietà Fondiaria, etc._, p. 144.
[190] _Météorologie_, German translation by EMSMANN, p. 605.
[191] _Handbuch der Physischen Geographie_, p. 658.
[192] _Annales des Ponts et Chaussées_, 1854, 1st sémestre, pp. 21 _et
seqq._ See the comments of VALLÈS on these observations, in his _Études
sur les Inondations_, pp. 441 _et seqq._
[193] The passage in Pliny is as follows: "Nascuntur fontes, decisis
plerumque silvis, quos arborum alimenta consumebant, sicut in Hæmo,
obsidente Gallos Cassandro, quum valli gratia cecidissent. Plerumque
vero damnosi torrentes corrivantur, detracta collibus silva continere
nimbos ac digerere consueta."--_Nat. Hist._, xxxi, 30.
Seneca cites this case, and another similar one said to have been
observed at Magnesia, from a passage in Theophrastus, not to be found in
the extant works of that author; but he adds that the stories are
incredible, because shaded grounds abound most in water: ferè
aquosissima sunt quæcumque umbrosissima.--_Quæst. Nat._, iii, 11. _See
Appendix_, No. 26.
[194] "Why go so far for the proof of a phenomenon that is repeated
every day under our own eyes, and of which every Parisian may convince
himself, without venturing beyond the Bois de Boulogne or the forest of
Meudon? Let him, after a few rainy days, pass along the Chevreuse road,
which is bordered on the right by the wood, on the left by cultivated
fields. The fall of water and the continuance of the rain have been the
same on both sides; but the ditch on the side of the forest will remain
filled with water proceeding from the infiltration through the wooded
soil, long after the other, contiguous to the open ground, has performed
its office of drainage and become dry. The ditch on the left will have
discharged in a few hours a quantity of water, which the ditch on the
right requires several days to receive and carry down to the
valley."--CLAVÉ, _Études, etc._, pp. 53, 54.
[195] VALLÈS, _Études sur les Inondations_, p. 472.
[196] _Économie Rurale_, p. 730.
[197] _Ueber die Entwaldung der Gebirge_, pp. 20 _et seqq._
[198] _Physische Geographie_, p. 32.
[199] _The Trees of America_, pp. 50, 51.
[200] THOMPSON's _Vermont_, appendix, p. 8.
[201] _Trees of America_, p. 48.
[202] Dumont, following Dansse, gives an interesting extract from the
Misopogon of the Emperor Julian, showing that, in the fourth century,
the Seine--the level of which now varies to the extent of thirty feet
between extreme high and extreme low water mark--was almost wholly
exempt from inundations, and flowed with a uniform current through the
whole year. "Ego olim eram in hibernis apud caram Lutetiam, [sic] enim
Galli Parisiorum oppidum appellant, quæ insula est non magna, in fluvio
sita, qui eam omni ex parte eingit. Pontes sublicii utrinque ad eam
ferunt, raròque fluvius minuitur ae crescit; sed qualis æstate, talis
esse solet hyeme."--_Des Travaux Publics dans leur Rapports avec
l'Agriculture_, p. 361, note.
As Julian was six years in Gaul, and his principal residence was at
Paris, his testimony as to the habitual condition of the Seine, at a
period when the provinces where its sources originate were well wooded,
is very valuable.
[203] Almost every narrative of travel in those countries which were the
earliest seats of civilization, contains evidence of the truth of these
general statements, and this evidence is presented with more or less
detail in most of the special works on the forest which I have occasion
to cite. I may refer particularly to HOHENSTEIN, _Der Wald_, 1860, as
full of important facts on this subject. See also CAIMI, _Cenni sulla
Importanza dei Boschi_, for some statistics not readily found elsewhere,
on this and other topics connected with the forest.
[204] Stanley, citing SELDEN, _De Jure Naturali_, book vi, and
FABRICIUS, _Cod. Pseudap._ V. T., i, 874, mentions a remarkable Jewish
tradition of uncertain but unquestionably ancient date, which is among
the oldest evidences of public respect for the woods, and of enlightened
views of their importance and proper treatment:
"To Joshua a fixed Jewish tradition ascribed ten decrees, laying down
precise rules, which were instituted to protect the property of each
tribe and of each householder from lawless depredation. Cattle, of a
smaller kind, were to be allowed to graze in thick woods, not in thin
woods; in woods, no kind of cattle without the owner's consent. Sticks
and branches might be gathered by any Hebrew, but not cut. * * * Woods
might be pruned, provided they were not olives or fruit trees, and that
there was sufficient shade in the place."--_Lectures on the History of
the Jewish Church_, part i, p. 271.
[205] There seems to have been a tendency to excessive clearing in
Central and Western, earlier than in Southeastern France. Wise and good
Bernard Palissy--one of those persecuted Protestants of the sixteenth
century, whose heroism, virtue, refinement, and taste shine out in such
splendid contrast to the brutality, corruption, grossness, and barbarism
of their oppressors--in the _Recepte Véritable_, first printed in 1563,
thus complains: "When I consider the value of the least clump of trees,
or even of thorns, I much marvel at the great ignorance of men, who, as
it seemeth, do nowadays study only to break down, fell, and waste the
fair forests which their forefathers did guard so choicely. I would
think no evil of them for cutting down the woods, did they but replant
again some part of them; but they care nought for the time to come,
neither reck they of the great damage they do to their children which
shall come after them."--_[OE]uvres Complètes de Bernard Palissy_, 1844,
p. 88.
[206] The great naval and commercial marines of Venice and of Genoa must
have occasioned an immense consumption of lumber in the Middle Ages, and
the centuries immediately succeeding those commonly embraced in that
designation. The marine construction of that period employed larger
timbers than the modern naval architecture of most commercial countries,
but apparently without a proportional increase of strength. The old
modes of ship building have been, to a considerable extent, handed down
to the present day in the Mediterranean, and an American or an
Englishman looks with astonishment at the huge beams and thick planks so
often employed in the construction of very small vessels navigating that
sea. According to Hummel, the desolation of the Karst, the high plateau
lying north of Trieste, now one of the most parched and barren districts
in Europe, is owing to the felling of its woods to build the navies of
Venice. "Where the miserable peasant of the Karst now sees nothing but
bare rock swept and scoured by the raging Bora, the fury of this wind
was once subdued by mighty firs, which Venice recklessly cut down to
build her fleets."--_Physische Geographie_, p. 32. See _Appendix_, No.
27.
[207] _Le Alpi che cingono l'Italia_, i, p. 367.
[208] See the periodical _Politecnico_, published at Milan, for the
month of May, 1862, p. 234.
[209] _Annali di Agricoltura, Industria e Commercio_, vol. i, p. 77.
[210] HOLINSHED, reprint of 1807, i, pp. 357, 358. It is evident from
this passage, and from another on page 397 of the same volume, that,
though sea coal was largely exported to the Continent, it had not yet
come into general use in England. It is a question of much interest,
when coal was first employed in England for fuel. I can find no evidence
that it was used as a combustible until more than a century after the
Norman conquest. It has been said that it was known to the Anglo-Saxon
population, but I am acquainted with no passage in the literature of
that people which proves this. The dictionaries explain the Anglo-Saxon
word _græfa_ by sea coal. I have met with this word in no Anglo-Saxon
work, except in the _Chronicle_, A. D. 852, from a manuscript certainly
not older than the twelfth century, and in that passage it may as
probably mean peat as coal, and quite as probably something else as
either. Coal is not mentioned in King Alfred's Bede, in Glanville, or in
Robert of Gloucester, though all these writers speak of jet as found in
England, and are full in their enumeration of the mineral products of
the island.
England was anciently remarkable for its forests, but Cæsar says it
wanted the _fagus_ and the _abies_. There can be no doubt that _fagus_
means the beech, which, as the remains in the Danish peat mosses show,
is a tree of late introduction into Denmark, where it succeeded the fir,
a tree not now native to that country. The succession of forest crops
seems to have been the same in England; for Harrison, p. 359, speaks of
the "great store of firre" found lying "at their whole lengths" in the
"fens and marises" of Lancashire and other counties, where not even
bushes grew in his time. We cannot be sure what species of evergreen
Cæsar intended by _abies_. The popular designations of spike-leaved
trees are always more vague and uncertain in their application than
those of broad-leaved trees. _Pinus_, _pine_, has been very loosely
employed even in botanical nomenclature, and _Kiefer_, _Fichte_, and
_Tanne_ are often confounded in German.--ROSSMÄSSLER, _Der Wald_, pp.
256, 289, 324. If it were certain that the _abies_ of Cæsar was the fir
formerly and still found in peat mosses, and that he was right in
denying the existence of the beech in England in his time, the
observation would be very important, because it would fix a date at
which the fir had become extinct, and the beech had not yet appeared in
the island.
The English oak, though strong and durable, was not considered generally
suitable for finer work in the sixteenth century. There were, however,
exceptions. "Of all in Essex," observes HARRISON, _Holinshed_, i, p.
357, "that growing in Bardfield parke is the finest for ioiners craft:
for oftentimes haue I seene of their workes made of that oke so fine and
faire, as most of the wainescot that is brought hither out of Danske;
for our wainescot is not made in England. Yet diuerse haue assaied to
deale without [with our] okes to that end, but not with so good successe
as they haue hoped, bicause the ab or iuice will not so soone be remoued
and cleane drawne out, which some attribute to want of time in the salt
water."
This passage is also of interest as showing that soaking in salt water,
as a mode of seasoning, was practised in Harrison's time.
But the importation of wainscot, or boards for ceiling, panelling, and
otherwise finishing rooms, which was generally of oak, commenced three
centuries before the time of Harrison. On page 204 of the _Liber
Albus_--a book which could have been far more valuable if the editor had
given us the texts, with his learned notes, instead of a
translation--mention is made of "squared oak timber," brought in from
the country by carts, and of course of domestic growth, as free of city
duty or octroi, and of "planks of oak" coming in in the same way as
paying one plank a cartload. But in the chapter on the "Customs of
Billyngesgate," pp. 208, 209, relating to goods imported from foreign
countries, a duty of one halfpenny is imposed on every hundred of boards
called "weynscotte," and of one penny on every hundred of boards called
"Rygholt." The editor explains "Rygholt" as "wood of Riga." This was
doubtless pine or fir. The year in which these provisions were made does
not appear, but they belong to the reign of Henry III.
[211] In a letter addressed to the Minister of Public Works, after the
terrible inundations of 1857, the Emperor thus happily expressed
himself: "Before we seek the remedy for an evil, we inquire into its
cause. Whence come the sudden floods of our rivers? From the water which
falls on the mountains, not from that which falls on the plains. The
waters which fall on our fields produce but few rivulets, but those
which fall on our roofs and are collected in the gutters, form small
streams at once. Now, the roofs are mountains--the gutters are valleys."
"To continue the comparison," observes D'Héricourt, "roofs are smooth
and impermeable, and the rain water pours rapidly off from their
surfaces; but this rapidity of flow would be greatly diminished if the
roofs were carpeted with mosses and grasses; more still, if they were
covered with dry leaves, little shrubs, strewn branches, and other
impediments--in short, if they were wooded."--_Annales Forestières,
Déc._, 1857, p. 311.
[212] "The roots of vegetables," says D'Héricourt, "perform the office
of a perpendicular drainage analogous to that which has been practised
with success in Holland and in some parts of the British Islands. This
system consists in driving down three or four thousand stakes upon a
hectare; the rain water filters down along the stakes, and, in certain
cases, as favorable results are obtained by this method as by horizontal
drains."--_Annales Forestières_, 1857, p. 312.
[213] The productiveness of Egypt has been attributed too exclusively to
the fertilizing effects of the slime deposited by the inundations of the
Nile; for in that climate a liberal supply of water would produce good
crops on almost any ordinary sand, while, without water, the richest
soil would yield nothing. The sediment deposited annually is but a very
small fraction of an inch in thickness. It is alleged that in quantity
it would be hardly sufficient for a good top dressing, and that in
quality it is not chemically distinguishable from the soil inches or
feet below the surface. But to deny, as some writers have done, that the
slime has any fertilizing properties at all, is as great an error as the
opposite one of ascribing all the agricultural wealth of Egypt to that
single cause of productiveness. Fine soils deposited by water are almost
uniformly rich in all climates; those brought down by rivers, carried
out into salt water, and then returned again by the tide, seem to be
more permanently fertile than any others. The polders of the Netherland
coast are of this character, and the meadows in Lincolnshire, which have
been covered with slime by _warping_, as it is called, or admitting
water over them at high tide, are remarkably productive. See _Appendix_,
No. 28.
[214] "The laws against clearing have never been able to prevent these
operations when the proprietor found his advantage in them, and the long
series of royal ordinances and decrees of parliaments, proclaimed from
the days of Charlemagne to our own, with a view of securing forest
property, have served only to show the impotence of legislative notion
on this subject."--CLAVÉ, _Études sur l'Économie Forestière_, p. 32.
"A proprietor can always contrive to clear his woods, whatever may be
done to prevent him; it is a mere question of time, and a few imprudent
cuttings, a few abuses of the right of pasturage, suffice to destroy a
forest in spite of all regulations to the contrary."--DUNOYER, _De la
Liberté du Travail_, ii, p. 452, as quoted by Clavé, p. 353.
Both authors agree that the preservation of the forests in France is
practicable only by their transfer to the state, which alone can protect
them and secure their proper treatment. It is much to be feared that
even this measure would be inadequate to save the forests of the
American Union. There is little respect for public property in America,
and the Federal Government, certainly, would not be the proper agent of
the nation for this purpose. It proved itself unable to protect the
live-oak woods of Florida, which were intended to be preserved for the
use of the navy, and it more than once paid contractors a high price for
timber stolen from its own forests. The authorities of the individual
States might be more efficient.
[215] See the lively account of the sale of a communal wood in
BERLEPSCH, _Die Alpen, Holzschläger und Flösser_.
[216] Streffleur (_Ueber die Natur und die Wirkungen der Wildbäche_, p.
3) maintains that all the observations and speculations of French
authors on the nature of torrents had been anticipated by Austrian
writers. In proof of this assertion he refers to the works of Franz von
Zallinger, 1778, Von Arretin, 1808, Franz Duile, 1826, all published at
Innsbruck, and HAGEN's _Beschreibung neuerer Wasserbauwerke_,
Königsberg, 1826, none of which works are known to me. It is evident,
however, that the conclusions of Surell and other French writers whom I
cite, are original results of personal investigation, and not borrowed
opinions.
[217] Whether Palissy was acquainted with this ancient practice, or
whether it was one of those original suggestions of which his works are
so full, I know not; but in his treatise, _Des Eaux et Fontaines_, he
thus recommends it, by way of reply to the objections of "Théorique,"
who had expressed the fear that "the waters which rush violently down
from the heights of the mountain would bring with them much earth, sand,
and other things," and thus spoil the artificial fountain that
"Practique" was teaching him to make: "And for hindrance of the
mischiefs of great waters which may be gathered in few hours by great
storms, when thou shalt have made ready thy parterre to receive the
water, thou must lay great stones athwart the deep channels which
lead to thy parterre. And so the force of the rushing currents
shall be deadened, and thy water shall flow peacefully into his
cisterns."--_[OE]uvres Complètes_, p. 173.
[218] Ladoucette says the peasant of Dévoluy "often goes a distance of
five hours over rocks and precipices for a single [man's] load of wood;"
and he remarks on another page, that "the justice of peace of that
canton had, in the course of forty-three years, but once heard the voice
of the nightingale."--_Histoire, etc., des Hautes Alpes_, pp. 220, 434.
[219] The valley of Embrun, now almost completely devastated, was once
remarkable for its fertility. In 1806, Héricart de Thury said of it: "In
this magnificent valley nature had been prodigal of her gifts. Its
inhabitants have blindly revelled in her favors, and fallen asleep in
the midst of her profusion."--BECQUEREL, _Des Climats, etc._, p. 314.
[220] In the days of the Roman empire the Durance was a navigable river,
with a commerce so important that the boatmen upon it formed a distinct
corporation.--LADOUCETTE, _Histoire, etc., des Hautes Alpes_, p. 354.
Even as early as 1789, the Durance was computed to have already covered
with gravel and pebbles not less than 130,000 acres, "which, but for its
inundations, would have been the finest land in the province."--ARTHUR
YOUNG, _Travels in France_, vol. i, ch. i.
[221] Between 1851 and 1856 the population of Languedoc and Provence had
increased by 101,000 souls. The augmentation, however, was wholly in the
provinces of the plains, where all the principal cities are found. In
these provinces the increase was 204,000, while in the mountain
provinces there was a diminution of 103,000. The reduction of the area
of arable land is perhaps even more striking. In 1842, the department of
the Lower Alps possessed 99,000 hectares, or nearly 245,000 acres, of
cultivated soil. In 1852, it had but 74,000 hectares. In other words, in
ten years 25,000 hectares, or 61,000 acres, had been washed away or
rendered worthless for cultivation, by torrents and the abuses of
pasturage.--CLAVÉ, _Études_, pp. 66, 67.
[222] The Skalära-Tobel, for instance, near Coire. See the description
in BERLEPSCH, _Die Alpen_, pp. 169 _et seqq_, or in Stephen's English
translation.
The recent change in the character of the Mella--a river anciently so
remarkable for the gentleness of its current that it was specially
noticed by Catullus as flowing _molli flumine_--deserves more than a
passing remark. This river rises in the mountain chain east of Lake
Iseo, and traversing the district of Brescia, empties into the Oglio
after a course of about seventy miles. The iron works in the upper
valley of the Mella had long created a considerable demand for wood, but
their operations were not so extensive as to occasion any very sudden or
general destruction of the forests, and the only evil experienced from
the clearings was the gradual diminution of the volume of the river.
Within the last twenty years, the superior quality of the arms
manufactured at Brescia has greatly enlarged the sale of them, and very
naturally stimulated the activity of both the forges and of the colliers
who supply them, and the hillsides have been rapidly stripped of their
timber. Up to 1850, no destructive inundation of the Mella had been
recorded. Buildings in great numbers had been erected upon its margin,
and its valley was conspicuous for its rural beauty and its fertility.
But when the denudation of the mountains had reached a certain point,
avenging nature began the work of retribution. In the spring and summer
of 1850 several new torrents were suddenly formed in the upper tributary
valleys, and on the 14th and 15th of August in that year, a fall of
rain, not heavier than had been often experienced, produced a flood
which not only inundated much ground never before overflowed, but
destroyed a great number of bridges, dams, factories, and other valuable
structures, and, what was a far more serious evil, swept off from the
rocks an incredible extent of soil, and converted one of the most
beautiful valleys of the Italian Alps into a ravine almost as bare and
as barren as the savagest gorge of Southern France. The pecuniary damage
was estimated at many millions of francs, and the violence of the
catastrophe was deemed so extraordinary, even in a country subject to
similar visitations, that the sympathy excited for the sufferers
produced, in five months, voluntary contributions for their relief to
the amount of nearly $200,000--_Delle Inondazioni del Mella, etc., nella
notte del 14 al 15 Agosto_, 1850.
The author of this remarkable pamphlet has chosen as a motto a passage
from the Vulgate translation of Job, which is interesting as showing
accurate observation of the action of the torrent: "Mons cadens definit,
et saxum transfertur de loco suo; lapides excavant aquæ et alluvione
paullatim terra consumitur."--_Job_ xiv, 18, 19.
The English version is much less striking, and gives a different sense.
[223] Streffleur quotes from Duile the following observations: "The
channel of the Tyrolese brooks is often raised much above the valleys
through which they flow. The bed of the Fersina is elevated high above
the city of Trient, which lies near it. The Villerbach flows at a much
more elevated level than that of the market place of Neumarkt and Vill,
and threatens to overwhelm both of them with its waters. The Talfer at
Botzen is at least even with the roofs of the adjacent town, if not
above them. The tower steeples of the villages of Schlanders, Kortsch,
and Laas, are lower than the surface of the Gadribach. The Saldurbach at
Schluderns menaces the far lower village with destruction, and the chief
town, Schwaz, is in similar danger from the Lahnbach."--STREFFLEUR,
_Ueber die Wildbäche, etc._, p. 7.
[224] The snow drifts into the ravines and accumulates to incredible
depths, and the water resulting from its dissolution and from the
deluging rains which fall in spring, and sometimes in the summer, being
confined by rocky walls on both sides, rises to a very great height, and
of course acquires an immense velocity and transporting power in its
rapid descent to its outlet from the mountain. In the winter of
1842--'3, the valley of the Doveria, along which the Simplon road
passes, was filled with solid snowdrifts to the depth of a hundred feet
above the carriage road, and the sledge track by which passengers and
the mails were carried ran at that height.
Other things being equal, the transporting power of the water is
greatest where its flow is most rapid. This is usually in the direction
of the axis of the ravine. As the current pours out of the gorge and
escapes from the lateral confinement of its walls, it spreads and
divides itself into numerous smaller streams, which shoot out from the
mouth of the valley, as from a centre, in different directions, like the
ribs of a fan from the pivot, each carrying with it its quota of stones
and gravel. The plain below the point of issue from the mountain is
rapidly raised by newly formed torrents, the elevation depending on the
inclination of the bed and the form and weight of the matter
transported. Every flood both increases the height of this central point
and extends the entire circumference of the deposit. The stream
retaining most nearly the original direction moves with the greatest
momentum, and consequently transports the solid matter with which it is
charged to the greatest distance.
The untravelled reader will comprehend this the better when he is
informed that the southern slope of the Alps generally rises suddenly
out of the plain, with no intervening hill to break the abruptness of
the transition, except those consisting of comparatively small heaps of
its own debris brought down by ancient glaciers or recent torrents. The
torrents do not wind down valleys gradually widening to the rivers or
the sea, but leap at once from the flanks of the mountains upon the
plains below. This arrangement of surfaces naturally facilitates the
formation of vast deposits at their points of emergence, and the centre
of the accumulation in the case of very small torrents is not
unfrequently a hundred feet high, and sometimes very much more.
Torrents and the rivers that receive them transport mountain debris to
almost incredible distances. Lorentz, in an official report on this
subject, as quoted by Marschand from the Memoirs of the Agricultural
Society of Lyons, says: "The felling of the woods produces torrents
which cover the cultivated soil with pebbles and fragments of rock, and
they do not confine their ravages to the vicinity of the mountains, but
extend them into the fertile fields of Provence and other departments,
to the distance of forty or fifty leagues."--_Entwaldung der Gebirge_,
p. 17.
[225] The precipitous walls of the Val de Lys, and more especially of
the Val Doveria, though here and there shattered, show in many places a
smoothness of face over a large vertical plane, at the height of
hundreds of feet above the bottom of the valley, which no known agency
but glacier ice is capable of producing, and of course they can have
undergone no sensible change at those points for a vast length of time.
The beds of the rivers which flow through those valleys suffer lateral
displacement occasionally, where there is room for the shifting of the
channel; but if any elevation or depression takes place in them, it is
too slow to be perceptible except in case of some merely temporary
obstruction.
[226] Lombardini found, twenty years ago, that the mineral matter
brought down to the Po by its tributaries was, in general, comminuted to
about the same degree of fineness as the sands of its bed at their
points of discharge. In the case of the Trebbia, which rises high in the
Apennines and empties into the Po at Piacenza, it was otherwise, that
river rolling pebbles and coarse gravel into the channel of the
principal stream. The banks of the other affluents--excepting some of
those which discharge their waters into the great lakes--then either
retained their woods, or had been so long clear of them, that the
torrents had removed most of the disintegrated and loose rock in their
upper basins. The valley of the Trebbia had been recently cleared, and
all the forces which tend to the degradation and transportation of rock
were in full activity.--_Notice sur les Rivières de la Lombardie,
Annales des Ponts et Chaussées_, 1847, 1er sémestre, p. 131.
Since the date of Lombardini's observations, many Alpine valleys have
been stripped of their woods. It would be interesting to know whether
any sensible change has been produced in the character or quantity of
the matter transported by them to the Po.
[227] In proportion as the dikes are improved, and breaches and the
escape of the water through them are less frequent, the height of the
annual inundations is increased. Many towns on the banks of the river,
and of course within the system of parallel embankments, were formerly
secure from flood by the height of the artificial mounds on which they
were built; but they have recently been obliged to construct ring dikes
for their protection.--BAUMGARTEN, after LOMBARDINI, in the paper last
quoted, pp. 141, 147.
[228] Three centuries ago, when the declivities of the mountains still
retained a much larger proportion of their woods, the moderate annual
floods of the Po were occasioned by the melting of the snows, and, as
appears by a passage of Tasso quoted by Castellani (_Dell' Influenza
delle Selve_, i, p. 58, note), they took place in May. The much more
violent inundations of the present century are due to rains, the waters
of which are no longer retained by a forest soil, but conveyed at once
to the rivers--and they occur almost uniformly in the autumn or late
summer. Castellani, on the page just quoted, says that even so late as
about 1780, the Po required a heavy rain of a week to overflow its
banks, but that forty years later, it was sometimes raised to full flood
in a single day.
[229] This change of coast line cannot be ascribed to upheaval, for a
comparison of the level of old buildings--as, for instance, the church
of San Vitale and the tomb of Theodoric at Ravenna--with that of the
sea, tends to prove a depression rather than an elevation of their
foundations.
A computation by a different method makes the deposits at the mouth of
the Po 2,123,000 mètres less; but as both of them omit the gravel and
silt rolled, if not floated, down at ordinary and low water, we are safe
in assuming the larger quantity.--_Article last quoted_, p. 174. (See
note, p. 329)
[230] Mengotti estimated the mass of solid matter annually "united to
the waters of the Po" at 822,000,000 cubic mètres, or nearly twenty
times as much as, according to Lombardini, that river delivers into the
Adriatic. Castellani supposes the computation of Mengotti to fall much
below the truth, and there can be no doubt that a vastly larger quantity
of earth and gravel is washed down from the Alps and the Apennines than
is carried to the sea.--CASTELLANI, _Dell' Immediata Influenza delle
Selve sul corso delle Acque_, i, pp. 42, 43.
I have contented myself with assuming less than one fifth of Mengotti's
estimate.
[231] BAUMGARTEN, _An. des Ponts et Chaussées_, 1847, 1er sémestre, p.
175.
[232] The total superficies of the basin of the Po, down to Ponte
Lagoscuro [Ferrara]--a point where it has received all its affluents--is
6,938,200 hectares, that is, 4,105,600 in mountain lands, 2,832,600 in
plain lands.--DUMONT, _Travaux Publics, etc._, p. 272.
These latter two quantities are equal respectively to 10,145,348, and
6,999,638 acres, or 15,852 and 10,937 square miles.
[233] I do not use the numbers I have borrowed or assumed as factors the
value of which is precisely ascertained; nor, for the purposes of the
present argument, is quantitative exactness important. I employ
numerical statements simply as a means of aiding the imagination to form
a general and certainly not extravagant idea of the extent of
geographical revolutions which man has done much to accelerate, if not,
strictly speaking, to produce.
There is an old proverb, _Dolus latet in generalibus_, and Arthur Young
is not the only public economist who has warned his readers against the
deceitfulness of round numbers. I think, on the contrary, that vastly
more error has been produced by the affectation of precision in cases
where precision is impossible. In all the great operations of
terrestrial nature, the elements are so numerous and so difficult of
exact appreciation, that, until the means of scientific observation and
measurement are much more perfected than they now are, we must content
ourselves with general approximations. I say _terrestrial_ nature,
because in cosmical movements we have fewer elements to deal with, and
may therefore arrive at much more rigorous accuracy in determination of
time and place than we can in fixing and predicting the quantities and
the epochs of variable natural phenomena on the earth's surface.
The value of a high standard of accuracy in scientific observation can
hardly be overrated; but habits of rigorous exactness will never be
formed by an investigator who allows himself to trust implicitly to the
numerical precision of the results of a few experiments. The wonderful
accuracy of geodetic measurements in modern times is, in general,
attained by taking the mean of a great number of observations at every
station, and this final precision is but the mutual balance and
compensation of numerous errors.
Travellers are often misled by local habits in the use of what may be
called representative numbers, where a definite is put for an indefinite
quantity. A Greek, who wished to express the notion of a great, but
undetermined number, used "myriad, or ten thousand;" a Roman, "six
hundred;" an Oriental, "forty," or, at present, very commonly, "fifteen
thousand." Many a tourist has gravely repeated, as an ascertained fact,
the vague statement of the Arabs and the monks of Mount Sinai, that the
ascent from the convent of St. Catherine to the summit of Gebel Moosa
counts "fifteen thousand" steps, though the difference of level is
barely two thousand feet, and the "Forty" Thieves, the "forty" martyr
monks of the convent of El Arbain--not to speak of a similar use of this
numeral in more important cases--have often been understood as
expressions of a known number, when in fact they mean simply _many_. The
number "fifteen thousand" has found its way to Rome, and De Quincey
seriously informs us, on the authority of a lady who had been at much
pains to ascertain the _exact_ truth, that, including closets large
enough for a bed, the Vatican contains fifteen thousand rooms. Any one
who has observed the vast dimensions of most of the apartments of that
structure will admit that we make a very small allowance of space when
we assign a square rod, sixteen and a half feet square, to each room
upon the average. On an acre, there might be one hundred and sixty such
rooms, including partition walls; and, to contain fifteen thousand of
them, a building must cover more than nine acres, and be ten stories
high, or possess other equivalent dimensions, which, as every traveller
knows, many times exceeds the truth.
That most entertaining writer, About, reduces the number of rooms in the
Vatican, but he compensates this reduction by increased dimensions, for
he uses the word _salle_, which cannot be applied to closets barely
large enough to contain a bed. According to him, there are in that
"presbytère," as he irreverently calls it, twelve thousand large rooms
[_salles_], thirty courts, and three hundred staircases.--_Rome
Contemporaire_, p. 68.
The pretended exactness of statistical tables is generally little better
than an imposture; and those founded not on direct estimation by
competent observers, but on the report of persons who have no particular
interest in knowing, but often have a motive for distorting, the
truth--such as census returns--are commonly to be regarded as but vague
guesses at the actual fact.
Fuller, who, for the combination of wit, wisdom, fancy, and personal
goodness, stands first in English literature, thus remarks on the
pretentious exactness of historical and statistical writers: "I approve
the plain, country By-word, as containing much Innocent Simplicity
therein,
_'Almost and very nigh
Have saved many a Lie.'_
So have the Latines their _prope_, _fere_, _juxta_, _circiter_, _plus
minus_, used in matters of fact by the most authentic Historians. Yea,
we may observe that the Spirit of Truth itself, where _Numbers_ and
_Measures_ are concerned, in Times, Places, and Persons, useth the
aforesaid Modifications, save in such cases where some mystery contained
in the number requireth a particular specification thereof:
In Times. | In Places. | In Person.
| |
Daniel, 5:33. | Luke, 24:13. | Exodus, 12:37.
Luke, 3:23. | John, 6:19. | Acts, 2:41.
None therefore can justly find fault with me, if, on the like occasion,
I have secured myself with the same Qualifications. Indeed, such
Historians who grind their Intelligence to the _powder of fraction_,
pretending to _cleave the pin_, do sometimes _misse the But_. Thus, one
reporteth, how in the Persecution under _Dioeletian_, there were neither
under nor over, but just _nine hundred ninety-nine_ martyrs. Yea,
generally those that trade in such _Retail-ware_, and deal in such small
parcells, may by the ignorant be commended for their _care_, but
condemned by the judicious for their ridiculous _curiosity_."--_The
History of the Worthies of England_, i, p. 59.
[234] SURELL, _Les Torrents des Hautes Alpes_, chap. xxiv. In such
cases, the clearing of the ground, which, in consequence of a temporary
diversion of the waters, or from some other cause, has become rewooded,
sometimes renews the ravages of the torrent. Thus, on the left bank of
the Durance, a wooded declivity had been formed by the debris brought
down by torrents, which had extinguished themselves after having swept
off much of the superficial strata of the mountain of Morgon. "All this
district was covered with woods, which have now been thinned out and are
perishing from day to day; consequently, the torrents have recommenced
their devastations, and if the clearings continue, this declivity, now
fertile, will be ruined, like so many others."--Id., p. 155.
[235] Where a torrent has not been long in operation, and earth still
remains mixed with the rocks and gravel it heaps up at its point of
eruption, vegetation soon starts up and prospers, if protected from
encroachment. In Provence, "several communes determined, about ten years
ago, to reserve the soils thus wasted, that is, to abandon them for a
certain time, to spontaneous vegetation, which was not slow in making
its appearance."--BECQUEREL, _Des Climats_, p. 315.
[236] Rock is permeable by water to a greater extent than is generally
supposed. Freshly quarried marble, and even granite, as well as most
other stones, are sensibly heavier, as well as softer and more easily
wrought, than after they are dried and hardened by air-seasoning. Many
sandstones are porous enough to serve as filters for liquids, and much
of that of Upper Egypt and Nubia hisses audibly when thrown into water,
from the escape of the air forced out of it by hydrostatic pressure and
the capillary attraction of the pores for water. See _Appendix_, No. 29.
[237] Palissy had observed the action of frost in disintegrating rock,
and he thus describes it, in his essay on the formation of ice: "I know
that the stones of the mountains of Ardennes be harder than marble.
Nevertheless, the people of that country do not quarry the said stones
in winter, for that they be subject to frost; and many times the rocks
have been seen to fall without being cut, by means whereof many people
have been killed, when the said rocks were thawing." Palissy was
ignorant of the expansion of water in freezing--in fact he supposed that
the mechanical force exerted by freezing water was due to compression,
not dilatation--and therefore he ascribes to thawing alone effects
resulting not less from congelation.
Various forces combine to produce the stone avalanches of the higher
Alps, the fall of which is one of the greatest dangers incurred by the
adventurous explorers of those regions--the direct action of the sun
upon the stone, the expansion of freezing water, and the loosening of
masses of rock by the thawing of the ice which supported them or held
them together.
[238] WESSELY, _Die Oesterreichischen Alpenländer und ihre Forste_, pp.
125, 126. Wessely records several other more or less similar occurrences
in the Austrian Alps. Some of them, certainly, are not to be ascribed to
the removal of the woods, but in most cases they are clearly traceable
to that cause.
[239] BIANCHI, Appendix to the Italian translation of Mrs. SOMERVILLE's
_Physical Geography_, p. xxxvi.
[240] See in KOHL, _Alpenreisen_, i, 120, an account of the ruin of
fields and pastures, and even of the destruction of a broad belt of
forest, by the fall of rocks in consequence of cutting a few large
trees. Cattle are very often killed in Switzerland by rock avalanches,
and their owners secure themselves from loss by insurance against this
risk as against damage by fire or hail.
[241] _Entwaldung der Gebirge_, p. 41.
[242] The importance of the wood in preventing avalanches is well
illustrated by the fact that, where the forest is wanting, the
inhabitants of localities exposed to snow slides often supply the place
of the trees by driving stakes through the snow into the ground, and
thus checking its propensity to slip. The woods themselves are sometimes
thus protected against avalanches originating on slopes above them, and
as a further security, small trees are cut down along the upper line of
the forest, and laid against the trunks of larger trees, transversely to
the path of the slide, to serve as a fence or dam to the motion of an
incipient avalanche, which may by this means be arrested before it
acquires a destructive velocity and force.
[243] The tide rises at Quebec to the height of twenty-five feet, and
when it is aided by a northeast wind, it flows with almost irresistible
violence. Rafts containing several hundred thousand cubic feet of timber
are often caught by the flood tide, torn to pieces, and dispersed for
miles along the shores.
[244] One of these, the Baron of Renfrew--so named from one of the
titles of the kings of England--built thirty or forty years ago,
measured 5,000 tons. They were little else than rafts, being almost
solid masses of timber designed to be taken to pieces and sold as lumber
on arriving at their port of destination.
The lumber trade at Quebec is still very large. According to a recent
article in the _Revue des Deux Mondes_, that city exported, in 1860,
30,000,000 cubic feet of squared timber, and 400,000,000 square feet of
"planches." The thickness of the boards is not stated, but I believe
they are generally cut an inch and a quarter thick for the Quebec trade,
and as they shrink somewhat in drying, we may estimate ten square for
one cubic foot of boards. This gives a total of 70,000,000 cubic feet.
The specific gravity of white pine is .554, and the weight of this
quantity of lumber, very little of which is thoroughly seasoned, would
exceed a million of tons, even supposing it to consist wholly of wood as
light as pine. New Brunswick, too, exports a large amount of lumber.
[245] This name, from the French _chantier_, which has a wider meaning,
is applied in America to temporary huts or habitations erected for the
convenience of forest life, or in connection with works of material
improvement.
[246] Trees differ much in their power of resisting the action of forest
fires. Different woods vary greatly in combustibility, and even when
their bark is scarcely scorched, they are, partly in consequence of
physiological character, and partly from the greater or less depth at
which their roots habitually lie below the surface, very differently
affected by running fires. The white pine, _Pinus strobus_, as it is the
most valuable, is also perhaps the most delicate tree of the American
forest, while its congener, the Northern pitch pine, _Pinus rigida_, is
less injured by fire than any other tree of that country. I have heard
experienced lumbermen maintain that the growth of this pine was even
accelerated by a fire brisk enough to destroy all other trees, and I
have myself seen it still flourishing after a conflagration which had
left not a green leaf but its own in the wood, and actually throwing out
fresh foliage, when the old had been quite burnt off and the bark almost
converted into charcoal. The wood of the pitch pine is of comparatively
little value for the joiner, but it is useful for very many purposes.
Its rapidity of growth in even poor soils, its hardihood, and its
abundant yield of resinous products, entitle it to much more
consideration, as a plantation tree, than it has hitherto received in
Europe or America.
[247] Between fifty and sixty years ago, a steep mountain with which I
am very familiar, composed of metamorphic rock, and at that time covered
with a thick coating of soil and a dense primeval forest, was
accidentally burnt over. The fire took place in a very dry season, the
slope of the mountain was too rapid to retain much water, and the
conflagration was of an extraordinarily fierce character, consuming the
wood almost entirely, burning the leaves and combustible portion of the
mould, and in many places cracking and disintegrating the rock beneath.
The rains of the following autumn carried off much of the remaining
soil, and the mountain side was nearly bare of wood for two or three
years afterward. At length, a new crop of trees sprang up and grew
vigorously, and the mountain is now thickly covered again. But the depth
of mould and earth is too small to allow the trees to reach maturity.
When they attain to the diameter of about six inches, they uniformly
die, and this they will no doubt continue to do until the decay of
leaves and wood on the surface, and the decomposition of the subjacent
rock, shall have formed, perhaps hundreds of years hence, a stratum of
soil thick enough to support a full-grown forest.
[248] The growth of the white pine, on a good soil and in open ground,
is rather rapid until it reaches the diameter of a couple of feet, after
which it is much slower. The favorite habitat of this tree is light
sandy earth. On this soil, and in a dense wood, it requires a century to
attain the diameter of a yard. Emerson (_Trees of Massachusetts_, p.
65), says that a pine of this species, near Paris, "thirty years
planted, is eighty feet high, with a diameter of three feet." He also
states that ten white pines planted at Cambridge, Massachusetts, in 1809
or 1810, exhibited, in the winter of 1841 and 1842, an average of twenty
inches diameter at the ground, the two largest measuring, at the height
of three feet, four feet eight inches in circumference; and he mentions
another pine growing in a rocky swamp, which, at the age of thirty-two
years, "gave seven feet in circumference at the but, with a height of
sixty-two feet six inches." This latter I suppose to be a seedling, the
others _transplanted_ trees, which might have been some years old when
placed where they finally grew.
The following case came under my own observation: In 1824, a pine tree,
so small that a young lady, with the help of a lad, took it up from the
ground and carried it a quarter of a mile, was planted near a house in a
town in Vermont. It was occasionally watered, but received no other
special treatment. I measured this tree in 1860, and found it, at four
feet from the ground, and entirely above the spread of the roots, two
feet and four inches in diameter. It could not have been more than three
inches through when transplanted, and must have increased its diameter
twenty-five inches in thirty-six years.
[249] WILLIAMS, _History of Vermont_, ii, p. 53. DWIGHT's _Travels_, iv,
p. 21, and iii, p. 36. EMERSON, _Trees of Massachusetts_, p. 61. PARISH,
_Life of President Wheelock_, p. 56.
[250] The forest trees of the Northern States do not attain to extreme
longevity in the dense woods. Dr. Williams found that none of the huge
pines, the age of which he ascertained, exceeded three hundred and fifty
or four hundred years, though he quotes a friend who thought he had
noticed trees considerably older. The oak lives longer than the pine,
and the hemlock spruce is perhaps equally long lived. A tree of this
latter species, cut within my knowledge in a thick wood, counted four
hundred and eighty-six, or, according to another observer, five hundred
annual circles.
Great luxuriance of animal and vegetable production is not commonly
accompanied by long duration of the individual. The oldest men are not
found in the crowded city; and in the tropics, where life is prolific
and precocious, it is also short. The most ancient forest trees of which
we have accounts have not been those growing in thick woods, but
isolated specimens, with no taller neighbor to intercept the light and
heat and air, and no rival to share the nutriment afforded by the soil.
The more rapid growth and greater dimensions of trees standing near the
boundary of the forest, are matters of familiar observation. "Long
experience has shown that trees growing on the confines of the wood may
be cut at sixty years of age as advantageously as others of the same
species, reared in the depth of the forest, at a hundred and twenty. We
have often remarked, in our Alps, that the trunk of trees upon the
border of a grove is most developed or enlarged upon the outer or open
side, where the branches extend themselves farthest, while the
concentric circles of growth are most uniform in those entirely
surrounded by other trees, or standing entirely alone."--A. and G.
VILLA, _Necessità dei Boschi_, pp. 17, 18.
[251] Caimi states that "a single flotation in the Valtelline in 1839,
caused damages alleged to amount to more than $800,000, and actually
appraised at $250,000."--_Cenni sulla Importanza e Coltura dei Boschi_,
p. 65.
[252] Most physicists who have investigated the laws of natural
hydraulics maintain that, in consequence of direct obstruction and
frictional resistance to the flow of the water of rivers along their
banks, there is both an increased rapidity of current and an elevation
of the water in the middle of the channel, so that a river presents
always a convex surface. The lumbermen deny this. They affirm that,
while rivers are rising, the water is highest in the middle of the
channel, and tends to throw floating objects shoreward; while they are
falling, it is lowest in the middle, and floating objects incline toward
the centre. Logs, they say, rolled into the water during the rise, are
very apt to lodge on the banks, while those set afloat during the
falling of the waters keep in the current, and are carried without
hindrance to their destination.
Foresters and lumbermen, like sailors and other persons whose daily
occupations bring them into contact, and often, into conflict, with
great natural forces, have many peculiar opinions, not to say
superstitions. In one of these categories we must rank the universal
belief of lumbermen, that with a given head of water, and in a given
number of hours, a sawmill cuts more lumber by night than by day. Having
been personally interested in several sawmills, I have frequently
conversed with sawyers on this subject, and have always been assured by
them that their uniform experience established the fact that, other
things being equal, the action of the machinery of sawmills is more
rapid by night than by day. I am sorry--perhaps I ought to be
ashamed--to say that my scepticism has been too strong to allow me to
avail myself of my opportunities of testing this question by passing a
night, watch in hand, counting the strokes of a millsaw. More
unprejudiced, and I must add, very intelligent and credible persons have
informed me that they have done so, and found the report of the sawyers
abundantly confirmed. A land surveyor, who was also an experienced
lumberman, sawyer, and machinist, a good mathematician and an exact
observer, has repeatedly told me, that he had very often "timed"
sawmills, and found the difference in favor of night work above thirty
per cent. _Sed quære._
[253] For many instances of this sort, see BECQUEREL, _Des Climats,
etc._, pp. 301-303. In 1664, the Swedes made an incursion into Jutland
and felled a considerable extent of forest. After they retired, a survey
of the damage was had, and the report is still extant. The number of
trees cut was found to be 120,000, and as an account was kept of the
numbers of each species of tree, the document is of interest in the
history of the forest, as showing the relative proportions between the
different trees which composed the wood. See VAUPELL. _Bögens
Indvandring_, p. 35, and _Notes_, p. 55.
[254] Since writing this paragraph, I have fallen upon--and that in a
Spanish author--one of those odd coincidences of thought which every man
of miscellaneous reading so often meets with. Antonio Ponz (_Viage de
España_, i, prólogo, p. lxiii), says: "Nor would this be so great an
evil, were not some of them declaimers against _trees_, thereby
proclaiming themselves, in some sort, enemies of the works of God, who
gave us the leafy abode of Paradise to dwell in, where we should be even
now sojourning, but for the first sin, which expelled us from it."
I do not know at what period the two Castiles were bared of their woods,
but the Spaniard's proverbial "hatred of a tree" is of long standing.
Herrera vigorously combats this foolish prejudice; and Ponz, in the
prologue to the ninth volume of his journey, says that many carried it
so far as wantonly to destroy the shade and ornamental trees planted by
the municipal authorities. "Trees," they contended, and still believe,
"breed birds, and birds eat up the grain." Our author argues against the
supposition of the "breeding of birds by trees," which, he says, is as
absurd as to believe that an elm tree can yield pears; and he charitably
suggests that the expression is, perhaps, a _manière de dire_, a popular
phrase, signifying simply that trees harbor birds.
[255] Religious intolerance had produced similar effects in France
at an earlier period. "The revocation of the edict of Nantes and
the dragonnades occasioned the sale of the forests of the unhappy
Protestants, who fled to seek in foreign lands the liberty of
conscience which was refused to them in France. The forests were
soon felled by the purchasers, and the soil in part brought under
cultivation."'--BECQUEREL, _Des Climats, etc._, p. 303.
[256] The American reader must be reminded that, in the language of the
chase and of the English law, a "forest" is not necessarily a wood. Any
large extent of ground, withdrawn from cultivation, reserved for the
pleasures of the chase, and allowed to clothe itself with a spontaneous
growth, serving as what is technically called "cover" for wild animals,
is, in the dialects I have mentioned, a forest. When, therefore, the
Norman kings afforested the grounds referred to in the text, it is not
to be supposed that they planted them with trees, though the protection
afforded to them by the game laws would, if cattle had been kept out,
soon have converted them into real woods.
[257] _Histoire des Paysans_, ii, p. 190. The work of Bonnemère is of
great value to those who study the history of mediæval Europe from a
desire to know its real character, and not in the hope of finding
apparent facts to sustain a false and dangerous theory. Bonnemère is one
of the few writers who, like Michelet, have been honest enough and bold
enough to speak the truth with regard to the relations between the
church and the people in the Middle Ages.
[258] It is painful to add that a similar outrage was perpetrated a very
few years ago, in one of the European states, by a prince of a family
now dethroned. In this case, however, the prince killed the trespasser
with his own hand, his sergeants refusing to execute his mandate.
[259] GUILLAUME DE NANGIS, as quoted in the notes to JOINVILLE,
_Nouvelle Collection des Mémoires, etc._, par Michaud et Poujoulat,
première série, i, p. 335.
Persons acquainted with the character and influence of the mediæval
clergy will hardly need to be informed that the ten thousand livres
never found their way to the royal exchequer. It was easy to prove to
the simple-minded king that, as the profits of sin were a monopoly of
the church, he ought not to derive advantage from the commission of a
crime by one of his subjects; and the priests were cunning enough both
to secure to themselves the amount of the fine, and to extort from Louis
large additional grants to carry out the purposes to which they devoted
the money. "And though the king did take the moneys," says the
chronicler, "he put them not into his treasury, but turned them into
good works; for he builded therewith the maison-Dieu of Pontoise, and
endowed the same with rents and lands; also the schools and the
dormitory of the friars preachers of Paris, and the monastery of the
Minorite friars."
[260] _Histoire des Paysans_, ii, p. 200.
[261] The following details from Bonnemère will serve to give a more
complete idea of the vexatious and irritating nature of the game laws of
France. The officers of the chase went so far as to forbid the pulling
up of thistles and weeds, or the mowing of any unenclosed ground before
St. John's day [24th June], in order that the nests of game birds might
not be disturbed. It was unlawful to fence-in any grounds in the plains
where royal residences were situated; thorns were ordered to be planted
in all fields of wheat, barley, or oats, to prevent the use of ground
nets for catching the birds which consumed, or were believed to consume,
the grain, and it was forbidden to cut or pull stubble before the first
of October, lest the partridge and the quail might be deprived of their
cover. For destroying the eggs of the quail, a fine of one hundred
livres was imposed for the first offence, double that amount for the
second, and for the third the culprit was flogged and banished for five
years to a distance of six leagues from the forest.--_Histoire des
Paysans_, ii, p. 202, text and notes.
Neither these severe penalties, nor any provisions devised by the
ingenuity of modern legislation, have been able effectually to repress
poaching. "The game laws," says Clavé, "have not delivered us from the
poachers, who kill twenty times as much game as the sportsmen. In the
forest of Fontainebleau, as in all those belonging to the state,
poaching is a very common and a very profitable offence. It is in vain
that the gamekeepers are on the alert night and day, they cannot prevent
it. Those who follow the trade begin by carefully studying the habits of
the game. They will lie motionless on the ground, by the roadside or in
thickets, for whole days, watching the paths most frequented by the
animals," &c.--_Revue des Deux Mondes_, Mai, 1863, p. 160.
The writer adds many details on this subject, and it appears that, as
there are "beggars on horseback" in South America, there are poachers in
carriages in France.
[262] "Whole trees were sacrificed for the most insignificant purposes;
the peasants would cut down two firs to make a single pair of wooden
shoes."--MICHELET, as quoted by CLAVÉ, _Études_, p. 24.
A similar wastefulness formerly prevailed in Russia, though not from the
same cause. In St. Pierre's time, the planks brought to St. Petersburg
were not sawn, but hewn with the axe, and a tree furnished but a single
plank.
[263] "A hundred and fifty paces from my house is a hill of drift sand,
on which stood a few scattered pines. _Pinus sylvestris_, and
_Sempervivum tectorum_ in abundance, _Statice armeria_, _Ammone
vernalis_, _Dianthus carthusianorum_, with other sand plants, were
growing there. I planted the hill with a few birches, and all the plants
I have mentioned completely disappeared, though there were many naked
spots of sand between the trees. It should be added, however, that the
hillock is more thickly wooded than before. * * * It seems then that
_Sempervivum tectorum_, &c., will not bear the neighborhood of the
birch, though growing well near the _Pinus sylvestris_. I have found the
large red variety of _Agaricus deliciosus_ only among the roots of the
pine; the greenish-blue _Agaricus deliciosus_ among alder roots, but not
near any other tree. Birds have their partialities among trees and
shrubs. The _Silviæ_ prefer the _Pinus Larix_ to other trees. In my
garden this _Pinus_ is never without them, but I never saw a bird perch
on _Thuja occidenialis_ or _Juniperus sabina_, although the thick
foliage of these latter trees affords birds a better shelter than the
loose leafage of other trees. Not even a wren ever finds its way to one
of them. Perhaps the scent of the _Thuja_ and the _Juniperus_ is
offensive to them. I have spoiled one of my meadows by cutting away the
bushes. It formerly bore grass four feet high, because many
umbelliferous plants, such as _Heracleum spondylium_, _Spiræa ulmaria_,
_Laserpitium latifolia_, &c., grew in it. Under the shelter of the
bushes these plants ripened and bore seed, but they gradually
disappeared as the shrubs were extirpated, and the grass now does not
grow to the height of more than two feet, because it is no longer
obliged to keep pace with the umbellifera which flourished among it."
See a paper by J. G. BÜTTNER, of Kurland, in BERGHAUS' _Geographisches
Jahrbuch_, 1852, No. 4, pp. 14, 15.
These facts are interesting as illustrating the multitude of often
obscure conditions upon which the life or vigorous growth of smaller
organisms depends. Particular species of truffles and of mushrooms are
found associated with particular trees, without being, as is popularly
supposed, parasites deriving their nutriment from the dying or dead
roots of those trees. The success of Rousseau's experiments seem
decisive on this point, for he obtains larger crops of truffles from
ground covered with young seedling oaks than from that filled with roots
of old trees. See an article on Mont Ventoux, by Charles Martins, in the
_Revue des Deux Mondes_, Avril, 1863, p. 626.
It ought to be much more generally known than it is that most, if not,
all mushrooms, even of the species reputed poisonous, may be rendered
harmless and healthful as food by soaking them for two hours in
acidulated or salt water. The water requires two or three spoonfuls of
vinegar or two spoonfuls of gray salt to the quart, and a quart of water
is enough for a pound of sliced mushrooms. After thus soaking, they are
well washed in fresh water, thrown into cold water, which is raised to
the boiling point, and, after remaining half an hour, taken out and
again washed. Gérard, to prove that "crumpets is wholesome," ate one
hundred and seventy-five pounds of the most poisonous mushrooms thus
prepared, in a single month, fed his family _ad libitum_ with the same,
and finally administered them, in heroic doses, to the members of a
committee appointed by the Council of Health of the city of Paris. See
FIGUIER, _L'Année Scientifique_, 1862, pp. 353, 384. See _Appendix_, No.
31.
It has long been known that the Russian peasantry eat, with impunity,
mushrooms of species everywhere else regarded as very poisonous. Is it
not probable that the secret of rendering them harmless--which was known
to Pliny, though since forgotten in Italy--is possessed by the rustic
Muscovites?
[264] _Physikalische Geographie_, p. 486.
[265] _Origin of Species_, American edition, p. 69.
[266] Writers on vegetable physiology record numerous instances where
seeds have grown after lying dormant for ages. The following cases,
mentioned by Dr. Dwight (_Travels_, ii, pp. 438, 439), may be new to
many readers:
"The lands [in Panton, Vermont], which have here been once cultivated,
and again permitted to lie waste for several years, yield a rich and
fine growth of hickory [_Carya porcina_]. Of this wood there is not, I
believe, a single tree in any original forest within fifty miles from
this spot. The native growth was here white pine, of which I did not see
a single stem in a whole grove of hickory."
The hickory is a walnut, bearing a fruit too heavy to be likely to be
carried fifty miles by birds, and besides, I believe it is not eaten by
any bird indigenous to Vermont.
"A field, about five miles from Northampton, on an eminence called Rail
Hill, was cultivated about a century ago. The native growth here, and in
all the surrounding region, was wholly oak, chestnut, &c. As the field
belonged to my grandfather, I had the best opportunity of learning its
history. It contained about five acres, in the form of an irregular
parallelogram. As the savages rendered the cultivation dangerous, it was
given up. On this ground there sprang up a grove of white pines covering
the field and retaining its figure exactly. So far as I remember, there
was not in it a single oak or chestnut tree. * * * There was not a
single pine whose seeds were, or, probably, had for ages been,
sufficiently near to have been planted on this spot. The fact that these
white pines covered this field exactly, so as to preserve both its
extent and its figure, and that there were none in the neighborhood, are
decisive proofs that cultivation brought up the seeds of a former forest
within the limits of vegetation, and gave them an opportunity to
germinate."
[267] Quaint old Valvasor had observed the subduing influence of
nature's solitudes. In describing the lonely Canker-Thal, which, though
rocky, was in his time well wooded with "fir, larches, beeches, and
other trees," he says: "Gladsomeness and beauty, which dwell in many
valleys, may not be looked for there. The journey through it is
cheerless, melancholy, wearisome, and serveth to temper and mortify
over-joyousness of thought. * * * In sum it is a very wild, wherein the
wildness of human pride doth grow tame."--_Ehre der Crain_, i, p. 136,
b.
[268] Valvasor says, in the same paragraph from which I have just
quoted, "In my many journeys through this valley, I did never have sight
of so much as a single bird."
[269] Smela, in the government of Kiew, has, for some years, not
suffered at all from the locusts, which formerly came every year in vast
swarms, and the curculio, so injurious to the turnip crops, is less
destructive there than in other parts of the province. This improvement
is owing partly to the more thorough cultivation of the soil, partly to
the groves which are interspersed among the plough lands. * * * When in
the midst of the plains woods shall be planted and filled with
insectivorous birds, the locusts will cease to be a plague and a terror
to the farmer.--RENTZSCH, _Der Wald_, pp. 45, 46.
[270] England is, I believe, the only country where private enterprise
has pursued sylviculture on a really great scale, though admirable
examples have been set in many others on both sides of the Atlantic. In
England the law of primogeniture, and other institutions and national
customs which tend to keep large estates long undivided and in the same
line of inheritance, the wealth of the landholders, and the difficulty
of finding safe and profitable investments of capital, combine to afford
encouragements for the plantation of forests, which nowhere else exist
in the same degree. The climate of England, too, is very favorable to
the growth of forest trees, though the character of surface secures a
large part of the island from the evils which have resulted from the
destruction of the woods elsewhere, and therefore their restoration is a
matter of less geographical importance in England than on the Continent.
[271] The preservation of the woods on the eastern frontier of France,
as a kind of natural abattis, is also recognized by the Government of
that country as an important measure of military defence, though there
have been conflicting opinions on the subject.
[272] Let us take the supply of timber for railroad ties. According to
Clavé (p. 248), France has 9,000 kilomètres of railway in operation,
7,000 in construction, half of which is built with a double track.
Adding turnouts and extra tracks at stations, the number of ties
required for a single track is stated at 1,200 to the kilomètre, or, as
Clavé computes, for the entire network of France, 58,000,000. As the
schoolboys say, "this sum does not prove;" for 16,000 + 8,000 for the
double track halfway = 24,000, and 24,000 × 1,200 = 28,800,000.
According to Bigelow (_Les États Unis en 1863_, p. 439), the United
States had in operation or construction on the first of January, 1862,
51,000 miles, or about 81,000 kilomètres of railroad, and the military
operations of the present civil war are rapidly extending the system.
Allowing the same proportion as in France, the American railroads
required 97,200,000 ties in 1862. The consumption of timber in Europe
and America during the present generation, occasioned by this demand,
has required the sacrifice of many hundred thousand acres of forest, and
if we add the quantity employed for telegraph posts, we have an amount
of destruction, for entirely new purposes, which is really appalling.
The consumption of wood for lucifer matches is enormous, and I have
heard of several instances where tracts of pine forest, hundreds and
even thousands of acres in extent, have been purchased and felled,
solely to supply timber for this purpose.
The demand for wood for small carvings and for children's toys is
incredibly large. Rentzsch states the export of such objects from the
town of Sonneberg alone to have amounted, in 1853, to 60,000 centner, or
three thousand tons' weight.--_Der Wald_, p. 68. See _Appendix_, No. 33.
The importance of so managing the forest that it may continue
indefinitely to furnish an adequate supply of material for naval
architecture is well illustrated by some remarks of the same author in
the valuable little work just cited. He suggests that the prosperity of
modern England is due, in no small degree, to the supplies of wood and
other material for building and equipping ships, received from the
forests of her colonies and of other countries with which she has
maintained close commercial relations, and he adds: "Spain, which by her
position seemed destined for universal power, and once, in fact,
possessed it, has lost her political rank, because during the unwise
administration of the successors of Philip II, the empty exchequer could
not furnish the means of building new fleets; for the destruction of the
forests had raised the price of timber above the resources of the
state."--_Der Wald_, p. 63.
The market price of timber, like that of all other commodities, may be
said, in a general way, to be regulated by the laws of demand and
supply, but it is also controlled by those seemingly unrelated accidents
which so often disappoint the calculations of political economists in
other branches of commerce. A curious case of this sort is noticed by
CERINI, _Dell' Impianto e Conservazione dei Boschi_, p. 17: "In the
mountains on the Lago Maggiore, in years when maize is cheap, the
woodcutters can provide themselves with corn meal enough for a week by
three days' labor, and they refuse to work the remaining four. Hence the
dealers in wood, not being able to supply the demand, for want of
laborers, are obliged to raise the price for the following season, both
for timber and for firewood; so that a low price of grain occasions a
high price of building lumber and of fuel. The consequence is, that
though the poor have supplied themselves cheaply with food, they must
pay dear for firewood, and they cannot get work, because the high price
of lumber has discouraged repairs and building, the expense of which
landed proprietors cannot undertake when their incomes have been reduced
by sales of grain at low rates, and hence there is not demand enough for
lumber to induce the timber merchants to furnish employment to the
woodmen."
[273] Besides the substitution of iron for wood, a great saving of
consumption of this latter material has been effected by the revival of
ancient methods of increasing its durability, and the invention of new
processes for the same purpose. The most effectual preservative yet
discovered for wood employed on land, is sulphate of copper, a solution
of which is introduced into the pores of the wood while green, by
soaking, by forcing-pumps, or, most economically, by the simple pressure
of a column of the fluid in a small pipe connected with the end of the
piece of timber subjected to the treatment. Clavé (_Études Forestières_,
pp. 240-249) gives an interesting account of the various processes
employed for rendering wood imperishable, and states that railroad ties
injected with sulphate of copper in 1846, were found absolutely
unaltered in 1855; and telegraphic posts prepared two years earlier, are
now in a state of perfect preservation.
For many purposes, the method of injection is too expensive, and some
simpler process is much to be desired. The question of the proper time
of felling timber is not settled, and the best modes of air, water, and
steam seasoning are not yet fully ascertained. Experiments on these
subjects would be well worth the patronage of governments in new
countries, where they can be very easily made, without the necessity of
much waste of valuable material, and without expensive arrangements for
observation.
The practice of stripping living trees of their bark some years before
they are felled, is as old as the time of Vitruvius, but is much less
followed than it deserves, partly because the timber of trees so treated
inclines to crack and split, and partly because it becomes so hard as to
be wrought with considerable difficulty.
In America, economy in the consumption of fuel has been much promoted by
the substitution of coal for wood, the general use of stoves both for
wood and coal, and recently by the employment of anthracite in the
furnaces of stationary and locomotive steam-engines. All the objections
to the use of anthracite for this latter purpose appear to have been
overcome, and the improvements in its combustion have been attended with
a great pecuniary saving, and with much advantage to the preservation of
the woods.
The employment of coal has produced a great reduction in the consumption
of fire wood in Paris. In 1815, the supply of fire wood for the city
required 1,200,000 stères, or cubic mètres; in 1859, it had fallen to
501,805, while, in the mean time, the consumption of coal had risen from
600,000 to 432,000,000 metrical quintals. See CLAVÉ, _Études_, p. 212.
I think there must be some error in this last sum, as 432 millions of
metrical quintals would amount to 43 millions of tons, a quantity which
it is difficult to suppose could be consumed in the city of Paris. The
price of fire wood has scarcely advanced at all in Paris for half a
century, though that of timber generally has risen enormously.
[274] In the first two years of the present civil war in the United
States, twenty-eight thousand walnut trees were felled to supply a
single European manufactory of gunstocks for the American market.
[275] Among the indirect proofs of the comparatively recent existence of
extensive forests in France, may be mentioned the fact, that wolves were
abundant, not very long since, in parts of the empire where there are
now neither wolves nor woods to shelter them. Arthur Young more than
once speaks of the "innumerable multitudes" of these animals which
infested France in 1789, and George Sand states, in the _Histoire de ma
Vie_, that some years after the restoration of the Bourbons, they chased
travellers on horseback in the Southern provinces, and literally knocked
at the doors of her father-in-law's country seat.
[276] In the _Recepte Véritable_, Palissy having expressed his
indignation at the folly of men in destroying the woods, his
interlocutor defends the policy of felling them, by citing the example
of "divers bishops, cardinals, priors, abbots, monkeries, and chapters,
which, by cutting their woods, have made three profits," the sale of the
timber, the rent of the ground, and the "good portion" they received of
the grain grown by the peasants upon it. To this argument, Palissy
replies: "I cannot enough detest this thing, and I call it not an error,
but a curse and a calamity to all France; for when forests shall be cut,
all arts shall cease, and they which practise them shall be driven out
to eat grass with Nebuchadnezzar and the beasts of the field. I have
divers times thought to set down in writing the arts which shall perish
when there shall be no more wood; but when I had written down a great
number, I did perceive that there could be no end of my writing, and
having diligently considered, I found there was not any which could be
followed without wood." * * "And truly I could well allege to thee a
thousand reasons, but 'tis so cheap a philosophy, that the very chamber
wenches, if they do but think, may see that without wood, it is not
possible to exercise any manner of human art or cunning."--_[OE]uvres
de_ BERNARD PALISSY, p. 89.
[277] Since writing the above paragraph, I have found the view I have
taken of this point confirmed by the careful investigations of Rentzsch,
who estimates the proper proportion of woodland to entire surface at
twenty-three per cent. for the interior of Germany, and supposes that
near the coast, where the air is supplied with humidity by evaporation
from the sea, it might safely be reduced to twenty per cent. See
Rentzsch's very valuable prize essay, _Der Wald im Haushalt der Natur
und der Volkswirthschaft_, cap. viii.
The due proportion in France would considerably exceed that for the
German States, because France has relatively more surface unfit for any
growth but that of wood, because the form and geological character of
her mountains expose her territory to much greater injury from torrents,
and because at least her southern provinces are more frequently visited
both by extreme drought and by deluging rains.
[278] _Études sur l'Économie Forestière_, p. 261. Clavé adds (p. 262):
"The Russian forests are very unequally distributed through the
territory of this vast empire. In the north they form immense masses,
and cover whole provinces, while in the south they are so completely
wanting that the inhabitants have no other fuel than straw, dung,
rushes, and heath." * * * "At Moscow, firewood costs thirty per cent.
more than at Paris, while, at the distance of a few leagues, it sells
for a tenth of that price."
This state of things is partly due to the want of facilities of
transportation, and some parts of the United States are in a similar
condition. During a severe winter, six or seven years ago, the sudden
freezing of the canals and rivers, before a large American town had
received its usual supply of fuel, occasioned an enormous rise in the
price of wood and coal, and the poor suffered severely for want of it.
Within a few hours of the city were large forests and an abundant stock
of firewood felled and prepared for burning. This might easily have been
carried to town by the railroads which passed through the woods; but the
managers of the roads refused to receive it as freight, because the
opening of a new market for wood might raise the price of the fuel they
employed for their locomotives.
Hohenstein, who was long professionally employed as a forester in
Russia, describes the consequences of the general war upon the woods in
that country as already most disastrous, and as threatening still more
ruinous evils. The river Volga, the life artery of Russian internal
commerce, is drying up from this cause, and the great Muscovite plains
are fast advancing to a desolation like that of Persia.--_Der Wald_, p.
223.
The level of the Caspian Sea is eighty-three feet lower than that of the
Sea of Azoff, and the surface of Lake Aral is fast sinking. Von Baer
maintains that the depression of the Caspian was produced by a sudden
subsidence, from geological causes, and not gradually by excess of
evaporation over supply. See _Kaspische Studien_, p. 25. But this
subsidence diminished the area and consequently the evaporation of that
sea, and the rivers which once maintained its ancient equilibrium ought
to raise it to its former level, if their own flow had not been
diminished. It is, indeed, not proved that the laying bare of a wooded
country diminishes the total annual precipitation upon it; but it is
certain that the summer evaporation from the surface of a champaign
region, like that through which the Volga, its tributaries, and the
feeders of Lake Aral flow, is increased by the removal of its woods.
Hence, though as much rain may still fall in the valleys of those rivers
as when their whole surface was covered with forests, a less quantity of
water may be delivered by them since their basins were cleared, and
therefore the present condition of the inland waters in question may be
due to the removal of the forests in their basins.
[279] Rentzsch _(Der Wald, etc._, pp. 123, 124) states the proportions
of woodland in different European countries as follows:
---------------+----------+-----------
| |Acres per
| Per cent.| head of
| |population.
---------------+----------+-----------
Germany | 26.58 | 0.6638
Great Britain | 5. | 0.1
France | 16.79 | 0.3766
Russia | 30.90 | 4.28
Sweden | 60. | 8.55
Norway | 66. | 24.61
Denmark | 5.50 | 0.22
Switzerland | 15. | 0.396
Holland | 7.10 | 0.12
Belgium | 18.52 | 0.186
Spain | 5.52 | 0.291
Portugal | 4.40 | 0.182
Sardinia | 12.29 | 0.223
Naples | 9.43 | 0.138
---------------+----------+-----------
Probably no European countries can so well dispense with the forests, in
their capacity of conservative influences, as England and Ireland. Their
insular position and latitude secure an abundance of atmospheric
moisture, and the general inclination of surface is not such as to
expose it to special injury from torrents. The due proportion of
woodland in England and Ireland is, therefore, almost purely an
economical question, to be decided by the comparative direct pecuniary
return from forest growth, pasturage, and plough land.
In Scotland, where the country is for the most part more broken and
mountainous, the general destruction of the forests has been attended
with very serious evils, and it is in Scotland that many of the most
extensive British forest plantations have now been formed. But although
the inclination of surface in Scotland is rapid, the geological
constitution of the soil is not of a character to promote such
destructive degradation by running water as in Southern France, and it
has not to contend with the parching droughts by which the devastations
of the torrents are rendered more injurious in that part of the French
empire.
In giving the proportion of woodland to population, I compute Rentzsch's
Morgen at .3882 of an English acre, because I find, by Alexander's most
accurate and valuable Dictionary of Weights and Measures, that this is
the value of the Dresden Morgen, and Rentzsch is a Saxon writer. In the
different German States, there are more than twenty different land
measures known by the name of Morgen, varying from about one third of an
acre to more than three acres in value. When will the world be wise
enough to unite in adopting the French metrical and monetary systems? As
to the latter, never while Christendom continues to be ruled by money
changers, who can compel you to part with your sovereigns in France at
twenty-five francs, and in England to accept fifteen shillings for your
napoleons. I speak as a sufferer. _Experto crede Roberto._
[280] According to the maxims of English jurisprudence, the common law
consists of general customs so long established that "the memory of man
runneth not to the contrary." In other words, long custom makes law. In
new countries, the change of circumstances creates new customs, and, in
time, new law, without the aid of legislation. Had the American
colonists observed a more sparing economy in the treatment of their
woods, a new code of customary forest law would have sprung up and
acquired the force of a statute. Popular habit was fast elaborating the
fundamental principles of such a code, when the rapid increase in the
value of timber, in consequence of the reckless devastation of the
woodlands, made it the interest of the proprietors to interfere with
this incipient system of forest jurisprudence, and appeal to the rules
of English law for the protection of their woods. The courts have
sustained these appeals, and forest property is now legally as
inviolable as any other, though common opinion still combats the course
of judicial decision on such questions.
In the United States, swarms of honey bees, on leaving the parent hive,
often take up their quarters in hollow trees in the neighboring woods.
By the early customs of New England, the finder of a "bee tree" on the
land of another owner was regarded as entitled to the honey by right of
discovery; and as a necessary incident of that right, he might cut the
tree, at the proper season, without asking permission of the proprietor
of the soil. The quantity of "wild honey" in a tree was often large, and
"bee hunting" was so profitable that it became almost a regular
profession. The "bee hunter" sallied forth with a small box containing
honey and a little vermilion. The bees which were attracted by the honey
marked themselves with the vermilion, and hence were more readily
followed in their homeward flight, and recognized when they returned a
second time for booty. When loaded with spoil, this insect returns to
his hive by the shortest route, and hence a straight line is popularly
called in America a "bee line." By such a line, the hunter followed the
bees to their sylvan hive, marked the tree with his initials, and
returned to secure his prize in the autumn. When the right of the "bee
hunter" was at last disputed by the land proprietors, it was with
difficulty that judgments could be obtained, in inferior courts, in
favor of the latter, and it was only after repeated decisions of the
higher legal tribunals that the superior right of the owner of the soil
was at last acquiesced in.
[281] _Étude sur le Reboisement des Montagnes_, p. 5.
[282] "In America," says Clavé (p. 124, 125), "where there is a vast
extent of land almost without pecuniary value, but where labor is dear
and the rate of interest high, it is profitable to till a large surface
at the least possible cost; _extensive_ cultivation is there the most
advantageous. In England, France, and Germany, where every corner of
soil is occupied, and the least bit of ground is sold at a high price,
but where labor and capital are comparatively cheap, it is wisest to
employ _intensive_ cultivation. * * * All the efforts of the cultivator
ought to be directed to the obtaining of a given result with the least
sacrifice, and there is equally a loss to the commonwealth if the
application of improved agricultural processes be neglected where
they are advantageous, or if they be employed where they are not
required. * * * In this point of view, sylviculture must follow the same
laws as agriculture, and, like it, be modified according to the
economical conditions of different states. In countries abounding in
good forests, and thinly peopled, elementary and cheap methods must be
pursued; in civilized regions, where a dense population requires that
the soil shall be made to produce all it can yield, the regular
artificial forest, with all the processes that science teaches, should
be cultivated. It would be absurd to apply to the endless woods of
Brazil and of Canada the method of the Spessart by "double stages," and
not less so in our country, where every yard of ground has a high value,
to leave to nature the task of propagating trees, and to content
ourselves with cutting, every twenty or twenty-five years, the meagre
growths that chance may have produced."
[283] It is often laid down as a universal law, that the wood of trees
of slow vegetation is superior to that of quick growth. This is one of
those commonplaces by which men love to shield themselves from the labor
of painstaking observation. It has, in fact, so many exceptions, that it
may be doubted whether it is in any sense true. Most of the cedars are
slow of growth; but while the timber of some of them is firm and
durable, that of others is light, brittle, and perishable. The hemlock
spruce is slower of growth than the pines, but its wood is of very
little value. The pasture oak and beech show a breadth of grain--and, of
course, an annual increment--twice as great as trees of the same species
grown in the woods; and the American locust, _Robinia pseudacacia_, the
wood of which is of extreme toughness and durability, is, of all trees
indigenous to Northeastern America, by far the most rapid in growth.
As an illustration of the mutual interdependence of the mechanic arts, I
may mention that in Italy, where stone, brick, and plaster are almost
the only materials used in architecture, and where the "hollow ware"
kitchen implements are of copper or of clay, the ordinary tools for
working wood are of a very inferior description, and the locust timber
is found too hard for their temper. Southey informs us, in "Espriella's
Letters," that when a small quantity of mahogany was brought to England,
early in the last century, the cabinetmakers were unable to use it, from
the defective temper of their tools, until the demand for furniture from
the new wood compelled them to improve the quality of their implements.
In America, the cheapness of wood long made it the preferable material
for almost all purposes to which it could by any possibility be applied.
The mechanical cutlery and artisans' tools of the United States are of
admirable temper, finish, and convenience, and no wood is too hard, or
otherwise too refractory, to be wrought with great facility, both by
hand tools and by the multitude of ingenious machines which the
Americans have invented for this purpose.
[284] _Études Forestières_, p. 7.
[285] _Études Forestières_, p. 7.
[286] For very full catalogues of American forest trees, and remarks on
their geographical distribution, consult papers on the subject by Dr. J.
G. Cooper, in the Report of the Smithsonian Institution for 1858, and
the Report of the United States Patent Office, Agricultural Division,
for 1860.
[287] Although Spenser's catalogue of trees occurs in the first canto of
the first book of the "Faëry Queene"--the only canto of that exquisite
poem actually read by most students of English literature--it is not so
generally familiar as to make the quotation of it altogether
superfluous:
VII.
Enforst to seeke some covert nigh at hand,
A shadie grove not farr away they spide,
That promist ayde the tempest to withstand;
Whose loftie trees, yelad with sommers pride,
Did spred so broad, that heavens light did hide,
Not perceable with power of any starr:
And all within were pathes and alleies wide,
With footing worne, and leading inward farr;
Faire harbour that them seems; so in they entred ar.
VIII.
And foorth they passe, with pleasure forward led,
Joying to heare the birdes sweete harmony,
Which therein shrouded from the tempest dred,
Seemd in their song to scorne the cruell sky.
Much can they praise the trees so straight and hy,
The sayling pine; the cedar stout and tall;
The vine-propp elm; the poplar never dry;
The builder oake, sole king of forrests all;
The aspine good for staves; the cypresse funerall;
IX.
The laurell, meed of mightie conquerours
And poets sage; the firre that weepeth still;
The willow, worne of forlorn paramours;
The eugh, obedient to the benders will;
The birch for shaftes; the sallow for the mill;
The mirrhe sweete-bleeding in the bitter wound;
The warlike beech; the ash for nothing ill;
The fruitfull olive; and the platane round;
The carver holme; the maple seeldom inward sound.
[288] The walnut is a more valuable tree than is generally supposed. It
yields one third of the oil produced in France, and in this respect
occupies an intermediate position between the olive of the south, and
the oleaginous seeds of the north. A hectare (about two and a half
acres), will produce nuts to the value of five hundred francs a year,
which cost nothing but the gathering. Unfortunately, its maturity must
be long waited for, and more nut-trees are felled than planted. The
demand for its wood in cabinet work is the principal cause of its
destruction. See LAVERGNE, _Économie Rurale de la France_, p. 253.
According to Cosimo Ridolfi (Lezioni Orali, ii. p. 424), France obtains
three times as much oil from the walnut as from the olive, and nearly as
much as from all oleaginous seeds together. He states that the walnut
bears nuts at the age of twenty years, and yields its maximum product at
seventy, and that a hectare of ground, with thirty trees, or twelve to
the acre, is equal to a capital of twenty-five hundred francs.
The nut of this tree is known in the United States as the "English
walnut." The fruit and the wood much resemble those of the American
black walnut, _Juglans nigra_, but for cabinet work the American is the
more beautiful material, especially when the large knots are employed.
The timber of the European species, when straight grained, and _clear_,
or free from knots, is, for ordinary purposes, better than that of the
American black walnut, but bears no comparison with the wood of the
hickory, when strength combined with elasticity is required, and its nut
is very inferior in taste to that of the shagbark, as well as to the
butternut, which it somewhat resembles.
"The chestnut is more valuable still, for it produces on a sterile soil,
which, without it, would yield only ferns and heaths, an abundant
nutriment for man."--LAVERGNE, _Économie Rurale de la France_, p. 253.
I believe the varieties developed by cultivation are less numerous in
the walnut than in the chestnut, which latter tree is often grafted in
Southern Europe.
[289] This fir is remarkable for its tendency to cicatrize or heal over
its stumps, a property which it possesses in common with some other
firs, the maritime pine, and the European larch. When these trees grow
in thick clumps, their roots are apt to unite by a species of natural
grafting, and if one of them be felled, although its own proper rootlets
die, the stump may continue, sometimes for a century, to receive
nourishment from the radicles of the surrounding trees, and a dome of
wood and bark of considerable thickness be formed over it. The
cicatrization is, however, only apparent, for the entire stump, except
the outside ring of annual growth, soon dies, and even decays within its
covering, without sending out new shoots.
[290] At the age of twelve or fifteen years, the cork tree is stripped
of its outer bark for the first time. This first yield is of inferior
quality, and is employed for floats for nets and buoys, or burnt for
lampblack. After this, a new layer of cork, an inch or an inch and a
quarter in thickness, is formed about once in ten years, and is removed
in large sheets without injury to the tree, which lives a hundred and
fifty years or more. According to Clavé (p. 252), the annual product of
a forest of cork oaks is calculated at about 660 kilogrammes, worth 150
francs, to the hectare, which, deducting expenses, leaves a profit of
100 francs. This is about equal to 250 pound weight, and eight dollars
profit to the acre. The cork oaks of the national domain in Algeria
cover about 500,000 acres, and are let to individuals at rates which are
expected, when the whole is rented, to yield to the state a revenue of
about $2,000,000.
George Sand, in the _Histoire de ma Vie_, speaks of the cork forests in
Southern France as among the most profitable of rural possessions, and
states, what I do not remember to have seen noticed elsewhere, that
Russia is the best customer for cork. The large sheets taken from the
trees are slit into thin plates, and used to line the walls of
apartments in that cold climate.
[291] The walnut, the chestnut, the apple, and the pear are common to
the border between the countries I have mentioned, but the range of the
other trees is bounded by the Alps, and by a well-defined and sharply
drawn line to the west of those mountains. I cannot give statistical
details as to the number of any of the trees in question, or as to the
area they would cover if brought together in a given country. From some
peculiarity in the sky of Europe, cultivated plants will thrive, in
Northern Italy, in Southern France, and even in Switzerland, under a
depth of shade where no crop, not even grass, worth harvesting, would
grow in the United States with an equally high summer temperature. Hence
the cultivation of all these trees is practicable in Europe to a greater
extent than would be supposed reconcilable with the interests of
agriculture. Some idea of the importance of the olive orchards may be
formed from the fact that Sicily alone, an island scarcely exceeding
10,000 square miles in area, of which one third at least is absolutely
barren, has exported to the single port of Marseilles more than
2,000,000 pounds weight of olive oil per year, for the last twenty
years.
[292] It is hard to say how far the peculiar form of the graceful crown
of this pine is due to pruning. It is true that the extremities of the
topmost branches are rarely lopped, but the lateral boughs are almost
uniformly removed to a very considerable height, and it is not
improbable that the shape of the top is thereby affected.
[293] Besides this, in a country so diversified in surface--I wish we
could with the French say _accidented_--as Italy with the exception of
the champaign region drained by the Po, every new field of view requires
either an extraordinary _coup d'[oe]il_ in the spectator, or a long
study, in order to master its relief, its plans, its salient and
retreating angles. In summer, the universal greenery confounds light and
shade, distance and foreground; and though the impression upon a
traveller, who journeys for the sake of "sensations," may be
strengthened by the mysterious annihilation of all standards for the
measurement of space, yet the superior intelligibility of the winter
scenery of Italy is more profitable to those who see with a view to
analyze.
[294] Copse, or coppice, from the French _couper_, to cut, signifies
properly a wood the trees of which are cut at certain periods of
immature growth, and allowed to shoot up again from the roots; but it
has come to signify, very commonly, a young wood, grove, or thicket,
without reference to its origin, or to its character of a forest crop.
[295] It has been recently stated, upon the evidence of the Government
foresters of Greece, and of the queen's gardener, that a large wood has
been discovered in Arcadia, consisting of a fir which has the property
of sending up both vertical and lateral shoots from the stump of felled
trees and forming a new crown. It was at first supposed that this forest
grew only on the "mountains," of which the hero of About's most amusing
story, _Le Roi des Montagnes_, was "king;" but it is now said that small
stumps, with the shoots attached, have been sent to Germany, and
recognized by able botanists as true natural products.
[296] Natural forests are rarely, if ever, composed of trees of a single
species, and experience has shown that oaks and other broad-leaved
trees, planted as artificial woods, require to be mixed, or associated
with others of different habits.
In the forest of Fontainebleau, "oaks, mingled with beeches in due
proportion," says Clavé, "may arrive at the age of five or six hundred
years in full vigor, and attain dimensions which I have never seen
surpassed; when, however, they are wholly unmixed with other trees, they
begin to decay and die at the top, at the age of forty or fifty years,
like men, old before their time, weary of the world, and longing only to
quit it. This has been observed in most of the oak plantations of which
I have spoken, and they have not been able to attain to full growth.
When the vegetation was perceived to languish, they were cut, in the
hope that this operation would restore their vigor, and that the new
shoots would succeed better than the original trees; and, in fact, they
seemed to be recovering for the first few years. But the shoots were
soon attacked by the same decay, and the operation had to be renewed at
shorter and shorter intervals, until at last it was found necessary to
treat as coppices plantations originally designed for the full-growth
system. Nor was this all: the soil, periodically bared by these
cuttings, became impoverished, and less and less suited to the growth of
the oak. * * * It was then proposed to introduce the pine and plant with
it the vacancies and glades. * * * By this means, the forest was saved
from the ruin which threatened it, and now more than 10,000 acres of
pines, from fifteen to thirty years old, are disseminated at various
points, sometimes intermixed with broad-leaved trees, sometimes forming
groves by themselves."--_Revue des Deux Mondes_, Mai, 1863, pp. 153,
154.
The forests of Denmark, which, in modern times, have been succeeded by
the beech--a species more inclined to be exclusive than any other
broad-leaved tree--were composed of birches, oaks, firs, aspens,
willows, hazel, and maple, the first three being the leading species. At
present, the beech greatly predominates.--VAUPELL, _Bögens Indvandring_,
pp. 19, 20.
[297] _Études Forestières_, p. 89.
[298] The grounds which it is most important to clothe with wood as a
conservative influence, and which, also, can best be spared from
agricultural use, are steep hillsides. But the performance of all the
offices of the forester to the tree--seeding, planting, thinning, and
finally felling and removing for consumption--is more laborious upon a
rapid declivity than on a level soil, and at the same time it is
difficult to apply irrigation or manures to trees so situated.
Experience has shown that there is great advantage in terracing the face
of a hill before planting it, both as preventing the wash of the earth
by checking the flow of water down its slope, and as presenting a
surface favorable for irrigation, as well as for manuring and
cultivating the tree. But even without so expensive a process, very
important results have been obtained by simply ditching declivities. "In
order to hasten the growth of wood on the flanks of a mountain, Mr.
Eugène Chevandier divided the slope into zones forty or fifty feet wide,
by horizontal ditches closed at both ends, and thereby obtained, from
firs of different ages, shoots double the dimensions of those which grew
on a dry soil of the same character, where the water was allowed to run
off without obstruction."--DUMONT, _Des Travaux Publics, etc._, pp.
94-96.
The ditches were about two feet and a half deep, and three feet and a
half wide, and they cost about forty francs the hectare, or three
dollars the acre. This extraordinary growth was produced wholly by the
retention of the rain water in the ditches, whence it filtered through
the whole soil and supplied moisture to the roots of the trees. It may
be doubted whether in a climate cold enough to freeze the entire
contents of the ditches in winter, it would not be expedient to draw off
the water in the autumn, as the presence of so large a quantity of ice
in the soil might prove injurious to trees too young and small to
shelter the ground effectually against frost.
Chevandier computes that, if the annual growth of the pine in the marshy
soil of the Vosges be represented by one, it will equal two in dry
ground, four or five on slopes so ditched or graded as to retain the
water flowing upon them from roads or steep declivities, and six where
the earth is kept constantly moist by infiltration from running
brooks.--_Comptes Rendus à l'Académie des Sciences_--t. xix, Juillet,
Dec., 1844, p. 167.
The effect of accidental irrigation is well shown in the growth of the
trees planted along the canals of irrigation which traverse the fields
in many parts of Italy. They flourish most luxuriantly, in spite of
continual lopping, and yield a very important contribution to the stock
of fuel for domestic use; while trees, situated so far from canals as to
be out of the reach of infiltration from them, are of much slower
growth, under circumstances otherwise equally favorable.
In other experiments of Chevandier, under better conditions, the yield
of wood was increased, by judicious irrigation, in the ratio of seven to
one, the profits in that of twelve to one. At the Exposition of 1855,
Chambrelent exhibited young trees, which, in four years from the seed,
had grown to the height of sixteen and twenty feet, and the diameter of
ten and twelve inches. Chevandier experimented with various manures, and
found that some of them might be profitably applied to young, but not to
old trees, the quantity required in the latter case being too great.
Wood ashes and the refuse of soda factories are particularly
recommended. I have seen an extraordinary growth produced in fir trees
by the application of soapsuds.
[299] Although the economy of the forest has received little attention
in the United States, no lover of American nature can have failed to
observe a marked difference between a native wood from which cattle are
excluded and one where they are permitted to browse. A few seasons
suffice for the total extirpation of the "underbrush," including the
young trees on which alone the reproduction of the forest depends, and
all the branches of those of larger growth which hang within reach of
the cattle are stripped of their buds and leaves, and soon wither and
fall off. These effects are observable at a great distance, and a wood
pasture is recognized, almost as far as it can be seen, by the
regularity with which its lower foliage terminates at what Ruskin
somewhere calls the "cattle line." This always runs parallel to the
surface of the ground, and is determined by the height to which domestic
quadrupeds can reach to feed upon the leaves. In describing a visit to
the grand-ducal farm of San Rossore near Pisa, where a large herd of
camels is kept, Chateauvieux says: "In passing through a wood of
evergreen oaks, I observed that all the twigs and foliage of the trees
were clipped up to the height of about twelve feet above the ground,
without leaving a single spray below that level. I was informed that the
browsing of the camels had trimmed the trees as high as they could
reach."--LULLIN DE CHATEAUVIEUX, _Lettres sur l'Italie_, p. 113.
The removal of the shelter afforded by the brushwood and the pendulous
branches of trees permits drying and chilling winds to parch and cool
the ground, and of course injuriously affects the growth of the wood.
But this is not all. The tread of quadrupeds exposes and bruises the
roots of the trees, which often die from this cause, as any one may
observe by following the paths made by cattle through woodlands.
[300] I have remarked elsewhere that most insects which deposit and
hatch their eggs in the wood of the natural forest confine themselves to
dead trees. Not only is this the fact, but it is also true that many of
the borers attack only freshly cut timber. Their season of labor is a
short one, and unless the tree is cut during this period, it is safe
from them. In summer you may hear them plying their augers in the wood
of a young pine with soft green bark, as you sit upon its trunk, within
a week after it has been felled, but the windfalls of the winter lie
uninjured by the worm and even undecayed for centuries. In the pine
woods of New England, after the regular lumberman has removed the
standing trees, these old trunks are hauled out from the mosses and
leaves which half cover them, and often furnish excellent timber. The
slow decay of such timber in the woods, it may be remarked, furnishes
another proof of the uniformity of temperature and humidity in the
forest, for the trunk of a tree lying on grass or plough land, and of
course exposed to all the alternations of climate, hardly resists
complete decomposition for a generation. The forests of Europe exhibit
similar facts. Wessely, in a description of the primitive wood of
Neuwald in Lower Austria, says that the windfalls required from 150 to
200 years for entire decay.-_-Die Oesterreichischen Alpenländer und ihre
Forste_, p. 312.
[301] VAUPELL, _Bögens Indvandring i de Danske Skove_, pp. 29, 46.
Vaupell further observes, on the page last quoted: "The removal of
leaves is injurious to the forest, not only because it retards the
growth of trees, but still more because it disqualifies the soil for the
production of particular species. When the beech languishes, and the
development of its branches is less vigorous and its crown less
spreading, it becomes unable to resist the encroachments of the fir.
This latter tree thrives in an inferior soil, and being no longer
stifled by the thick foliage of the beech, it spreads gradually through
the wood, while the beech retreats before it and finally perishes."
The study of the natural order of succession in forest trees is of the
utmost importance in sylviculture, because it guides us in the selection
of the species to be employed in planting a new or restoring a decayed
forest. When ground is laid bare both of trees and of vegetable mould,
and left to the action of unaided and unobstructed nature, she first
propagates trees which germinate and grow only under the influence of a
full supply of light and air, and then, in succession, other species,
according to their ability to bear the shade and their demand for more
abundant nutriment. In Northern Europe, the larch, the white birch, the
aspen, first appear; then follow the maple, the alder, the ash, the fir;
then the oak and the linden; and then the beech. The trees called by
these respective names in the United States are not specifically the
same as their European namesakes, nor are they always even the
equivalents of these latter, and therefore the order of succession in
America would not be precisely as indicated by the foregoing list, but
it nevertheless very nearly corresponds to it.
It is thought important to encourage the growth of the beech in Denmark
and Northern Germany, because it upon the whole yields better returns
than other trees, and particularly because it appears not to exhaust,
but on the contrary to enrich the soil; for by shedding its leaves it
returns to it most of the nutriment it has drawn from it, and at the
same time furnishes a solvent which aids materially in the decomposition
of its mineral constituents.
When the forest is left to itself, the order of succession is constant,
and its occasional inversion is always explicable by some human
interference. It is curious that the trees which require most light are
content with the poorest soils, and _vice versa_. The trees which first
appear are also those which propagate themselves farthest to the north.
The birch, the larch, and the fir bear a severer climate than the oak,
the oak than the beech. "These parallelisms," says Vaupell, "are very
interesting, because they are entirely independent of each other," and
each prescribes the same order of succession.--_Bögens Indvandring_, p.
42.
[302] When vigorous young locusts, of two or three inches in diameter,
are polled, they throw out a great number of very thick-leaved shoots,
which arrange themselves in a globular head, so unlike the natural crown
of the acacia, that persons familiar only with the untrained tree often
take them for a different species.
[303] The two ideas expressed in the text are not exactly equivalent,
because, though the consumption of animal food diminishes the amount of
vegetable aliment required for human use, yet the animals themselves
consume a great quantity of grain and roots grown on ground ploughed and
cultivated as regularly and as laboriously as any other.
The 170,000,000 bushels of oats raised in the United States in 1860, and
fed to the 6,000,000 horses, the potatoes, the turnips, and the maize
employed in fattening the oxen, the sheep, and the swine slaughtered the
same year, occupied an extent of ground which, cultivated by hand labor
and with Chinese industry and skill, would probably have produced a
quantity of vegetable food equal in alimentary power to the flesh of the
quadrupeds killed for domestic use. Hence, so far as the naked question
of _amount_ of aliment is concerned, the meadows and the pastures might
as well have remained in the forest condition.
[304] According to Clavé (_Études_, p. 159), the net revenue from the
forests of the state in France, making no allowance for interest on the
capital represented by the forest, is two dollars per acre. In Saxony it
is about the same, though the cost of administration is twice as much as
in France; in Würtemberg it is about a dollar an acre; and in Prussia,
where half the income is consumed in the expenses of administration, it
sinks to less than half a dollar. This low rate in Prussia is partly
explained by the fact that a considerable proportion of the annual
product of wood is either conceded to persons claiming prescriptive
rights, or sold, at a very small price, to the poor. Taking into account
the capital invested in forest land, and adding interest upon it,
Pressler calculates that a pine wood, managed with a view to felling it
when eighty years old, would yield only one eighth of one per cent.
annual profit; a fir wood, at one hundred years, one sixth of one per
cent.; a beech wood, at one hundred and twenty years, one fourth of one
per cent. The same author (p. 335) gives the net income of the New
forest in England, over and above expenses, interest not computed, at
twenty-five cents per acre only. In America, where no expense is
bestowed upon the woods, the annual growth would generally be estimated
much higher.
[305] It is rare that a middle-aged American dies in the house where he
was born, or an old man even in that which he has built; and this is
scarcely less true of the rural districts, where every man owns his
habitation, than of the city, where the majority live in hired houses.
This life of incessant flitting is unfavorable for the execution of
permanent improvements of every sort, and especially of those which,
like the forest, are slow in repaying any part of the capital expended
in them. It requires a very generous spirit in a landholder to plant a
wood on a farm he expects to sell, or which he knows will pass out of
the hands of his descendants at his death. But the very fact of having
begun a plantation would attach the proprietor more strongly to the soil
for which he had made such a sacrifice; and the paternal acres would
have a greater value in the eyes of a succeeding generation, if thus
improved and beautified by the labors of those from whom they were
inherited. Landed property, therefore, the transfer of which is happily
free from every legal impediment or restriction in the United States,
would find, in the feelings thus prompted, a moral check against a too
frequent change of owners, and would tend to remain long enough in one
proprietor or one family to admit of gradual improvements which would
increase its value both to the possessor and to the state.
[306] It has been often asserted by eminent writers that a part of the
fens in Lincolnshire was reclaimed by sea dikes under the government of
the Romans. I have found no ancient authority in support of this
allegation, nor can I refer to any passage in Roman literature in which
sea dikes are expressly mentioned otherwise than as walls or piers,
except that in Pliny (_Hist. Nat._ xxxvi, 24), where it is said that the
Tyrrhenian sea was excluded from the Lucrine lake by dikes.
[307] A friend has recently suggested to me an interesting illustration
of the applicability of military instrumentalities to pacific art. The
sale of gunpowder in the United States, he informs me, is smaller since
the commencement of the present rebellion than before, because the war
has caused the suspension of many public and private improvements, in
the execution of which great quantities of powder were used for
blasting.
It is alleged that the same observation was made in France during the
Crimean war, and that, in general, not ten per cent. of the powder
manufactured on either side of the Atlantic is employed for military
purposes.
It is a fact not creditable to the moral sense of modern civilization,
that very many of the most important improvements in machinery and the
working of metals have originated in the necessities of war, and that
man's highest ingenuity has been shown, and many of his most remarkable
triumphs over natural forces achieved, in the contrivance of engines for
the destruction of his fellow man. The military material employed by the
first Napoleon has become, in less than two generations, nearly as
obsolete as the sling and stone of the shepherd, and attack and defence
now begin at distances to which, half a century ago, military
reconnoissances hardly extended. Upon a partial view of the subject, the
human race seems destined to become its own executioner--on the one
hand, exhausting the capacity of the earth to furnish sustenance to her
taskmaster; on the other, compensating diminished production by
inventing more efficient methods of exterminating the consumer.
But war develops great civil virtues, and brings into action a degree
and kind of physical energy which seldom fails to awaken a new
intellectual life in a people that achieves great moral and political
results through great heroism and endurance and perseverance. Domestic
corruption has destroyed more nations than foreign invasion, and a
people is rarely conquered till it has deserved subjugation.
[308] STARING, _Voormaals en Thans_, p. 150.
[309] Idem, p. 163. Much the largest proportion of the lands so
reclaimed, though for the most part lying above low-water tidemark, are
at a lower level than the Lincolnshire fens, and more subject to
inundation from the irruptions of the sea.
[310] _Die Inseln und Marschen der Herzogthümer Schleswig und Holstein_,
iii, p. 151.
[311] The purely agricultural island of Pelworm, off the coast of
Schleswig, containing about 10,000 acres, annually expends for the
maintenance of its dikes not less than £6,000 sterling, or nearly
$30,000.--J. G. KOHL, _Inseln und Marschen Schleswig's und Holstein's_,
ii, p. 394.
The original cost of the dikes of Pelworm is not stated.
"The greatest part of the province of Zeeland is protected by dikes
measuring 250 miles in length, the maintenance of which costs, in
ordinary years, more than a million guilders [above $400,000]. * * * The
annual expenditure for dikes and hydraulic works in Holland is from five
to seven million guilders" [$2,000,000 to $2,800,000].--WILD, _Die
Niederlande_, i, p. 62.
One is not sorry to learn that the Spanish tyranny in the Netherlands
had some compensations. The great chain of ring dikes which surrounds a
large part of Zeeland is due to the energy of Caspar de Robles, the
Spanish governor of that province, who in 1570 ordered the construction
of these works at the public expense, as a substitute for the private
embankments which had previously partially served the same
purpose.--WILD, _Die Niederlande_, i, p. 62.
[312] STARING, _Voormaals en Thans_, p. 163.
[313] _Voormaals en Thans_, pp. 150, 151.
[314] STARING, _Voormaals en Thans_, p. 152. Kohl states that the
peninsula of Diksand on the coast of Holstein consisted, at the close of
the last century, of several islands measuring together less than five
thousand acres. In 1837 they had been connected with the mainland, and
had nearly doubled in area.--_Inseln u. Marschen Schlesw. Holst._, iii,
p. 262.
[315] The most instructive and entertaining of tourists, J. G. Kohl--so
aptly characterized by Davies as the "Herodotus of modern
Europe"--furnishes a great amount of interesting information on the
dikes of the Low German seacoast, in his _Inseln und Marschen der
Herzogthümer Schleswig und Holstein_. I am acquainted with no popular
work on this subject which the reader can consult with greater profit.
See also STARING, _Voormaals en Thans_, and _De Bodem van Nederland_, on
the dikes of the Netherlands.
[316] The inclination varies from one foot rise in four of base to one
foot in fourteen.--KOHL, iii, p. 210.
[317] The dikes are sometimes founded upon piles, and sometimes
protected by one or more rows of piles driven deeply down into the bed
of the sea in front of them. "Triple rows of piles of Scandinavian
pine," says Wild, "have been driven down along the coast of Friesland,
where there are no dunes, for a distance of one hundred and fifty miles.
The piles are bound together by strong cross timbers and iron clamps,
and the interstices filled with stones. The ground adjacent to the
piling is secured with fascines, and at exposed points heavy blocks of
stone are heaped up as an additional protection. The earth dike is built
behind the mighty bulwark of this breakwater, and its foot also is
fortified with stones." * * * "The great Helder dike is about five miles
long and forty feet wide at the top, along which runs a good road. It
slopes down two hundred feet into the sea, at an angle of forty degrees.
The highest waves do not reach the summit, the lowest always cover its
base. At certain distances, immense buttresses, of a height and width
proportioned to those of the dike, and even more strongly built, run
several hundred feet out into the rolling sea. This gigantic artificial
coast is entirely composed of Norwegian granite."--WILD, _Die
Niederlande_, i, pp. 61, 62.
[318] The shaking of the ground, even when loaded with large buildings,
by the passage of heavy carriages or artillery, or by the march of a
body of cavalry or even infantry, shows that such causes may produce
important mechanical effects on the condition of the soil. The bogs in
the Netherlands, as in most other countries, contain large numbers of
fallen trees, buried to a certain depth by earth and vegetable mould.
When the bogs are dry enough to serve as pastures, it is observed that
trunks of these ancient trees rise of themselves to the surface. Staring
ascribes this singular phenomenon to the agitation of the ground by the
tread of cattle. "When roadbeds," observes he, "are constructed of
gravel and pebbles of different sizes, and these latter are placed at
the bottom without being broken and rolled hard together, they are soon
brought to the top by the effect of travel on the road. Lying loosely,
they undergo some motion from the passage of every wagon wheel and the
tread of every horse that passes over them. This motion is an
oscillation or partial rolling, and as one side of a pebble is raised, a
little fine sand or earth is forced under it, and the frequent
repetition of this process by cattle or carriages moving in opposite
directions brings it at last to the surface. We may suppose that a
similar effect is produced on the stems of trees in the bogs by the
tread of animals."--_De Bodem van Nederland_, i, pp. 75, 76.
It is observed in the Northern United States, that when soils containing
pebbles are cleared and cultivated, and the stones removed from the
surface, new pebbles, and even bowlders of many pounds weight, continue
to show themselves above the ground, every spring, for a long series of
years. In clayey soils the fence posts are thrown up in a similar way,
and it is not uncommon to see the lower rail of a fence thus gradually
raised a foot or even two feet above the ground. This rising of stones
and fences is popularly ascribed to the action of the severe frosts of
that climate. The expansion of the ground, in freezing, it is said,
raises its surface, and, with the surface, objects lying near or
connected with it. When the soil thaws in the spring, it settles back
again to its former level, while the pebbles and posts are prevented
from sinking as low as before by loose earth which has fallen under
them. The fact that the elevation spoken of is observed only in the
spring, gives countenance to this theory, which is perhaps applicable
also to the cases stated by Staring, and it is probable that the two
causes above assigned concur in producing the effect.
The question of the subsidence of the Netherlandish coast has been much
discussed. Not to mention earlier geologists, Venema, in several essays,
and particularly in _Het Dalen van de Noordelijke Kuststreken van ons
Land_, 1854, adduces many facts and arguments to prove a slow sinking of
the northern provinces of Holland. Laveleye (_Affaissement du sol et
envasement des fleuves survenus dans les temps historiques_, 1859), upon
a still fuller investigation, arrives at the same conclusion. The
eminent geologist Staring, however, who briefly refers to the subject in
_De Bodem van Nederland_, i, p. 356 _et seqq._, does not consider the
evidence sufficient to prove anything more than the sinking of the
surface of the polders from drying and consolidation.
[319] The elevation of the lands enclosed by dikes--or _polders_, as
they are called in Holland--above low water mark, depends upon the
height of the tides, or, in other words, upon, the difference between
ebb and flood. The tide cannot deposit earth higher than it flows, and
after the ground is once enclosed, the decay of the vegetables grown
upon it and the addition of manures do not compensate the depression
occasioned by drying and consolidation. On the coast of Zeeland and the
islands of South Holland, the tides, and of course the surface of the
lands deposited by them, are so high that the polders can be drained by
ditching and sluices, but at other points, as in the enclosed grounds of
North Holland on the Zuiderzee, where the tide rises but three feet or
even less, pumping is necessary from the beginning.--STARING, _Voormaals
en Thans_, p. 152.
[320] The principal engine--called the Leeghwater, from the name of an
engineer who had proposed the draining of the lake in 1641--was of 500
horse power, and drove eleven pumps making six strokes per minute. Each
pump raised six cubic mètres, or nearly eight cubic yards of water to
the stroke, amounting in all to 23,760 cubic mètres, or above 31,000
cubic yards, the hour.--WILD, _Die Niederlande_, i, p. 87.
[321] In England and New England, where the marshes have been already
drained or are of comparatively small extent, the existence of large
floating islands seems incredible, and has sometimes been treated as a
fable, but no geographical fact is better established. Kohl (_Inseln und
Marschen Schleswig-Holsteins_, iii, p. 309) reminds us that Pliny
mentions among the wonders of Germany the floating islands, covered with
trees, which met the Roman fleets at the mouths of the Elbe and the
Weser. Our author speaks also of having visited, in the territory of
Bremen, floating moors, bearing not only houses but whole villages. At
low stages of the water these moors rest upon a bed of sand, but are
raised from six to ten feet by the high water of spring, and remain
afloat until, in the course of the summer, the water beneath is
exhausted by evaporation and drainage, when they sink down upon the sand
again. See _Appendix_, No. 40.
Staring explains, in an interesting way, the whole growth, formation,
and functions of floating fens or bogs, in his very valuable work, _De
Bodem van_ _Nederland_, i, pp. 36-43. The substance of his account is as
follows: The first condition for the growth of the plants which compose
the substance of turf and the surface of the fens, is stillness of the
water. Hence they are not found in running streams, nor in pools so
large as to be subject to frequent agitation by the wind. For example,
not a single plant grew in the open part of the Lake of Haarlem, and
fens cease to form in all pools as soon as, by the cutting of the turf
for fuel or other purposes, their area is sufficiently enlarged to be
much acted on by wind. When still water above a yard deep is left
undisturbed, aquatic plants of various genera, such us Nuphar, Nymphæa,
Limnanthemum, Stratiotes, Polygonum, and Potamogeton, fill the bottom
with roots and cover the surface with leaves. Many of the plants die
every year, and prepare at the bottom a soil fit for the growth of a
higher order of vegetation, Phragmites, Acorus, Sparganium, Rumex,
Lythrum, Pedicularis, Spiræa, Polystichum, Comarum, Caltha, &c., &c. In
the course of twenty or thirty years the muddy bottom is filled with
roots of aquatic and marsh plants, which are lighter than water, and if
the depth is great enough to give room for detaching this vegetable
network, a couple of yards for example, it rises to the surface, bearing
with it, of course, the soil formed above it by decay of stems and
leaves. New genera now appear upon the mass, such as Carex, Menyanthes,
and others, and soon thickly cover it. The turf has now acquired a
thickness of from two to four feet, and is called in Groningen _lad_; in
Friesland, _til_, _tilland_, or _drijftil_; in Overijssel, _krag_; and
in Holland, _rietzod_. It floats about as driven by the wind, gradually
increasing in thickness by the decay of its annual crops of vegetation,
and in about half a century reaches the bottom and becomes fixed. If it
has not been invaded in the mean time by men or cattle, trees and
arborescent plants, Alnus, Salix, Myrica, &c. appear, and these
contribute to hasten the attachment of the turf to the bottom, both by
their weight and by sending their roots quite through into the ground.
This is the regular method employed by nature for the gradual filling up
of shallow lakes and pools, and converting them first into morass and
then into dry land. Whenever therefore man removes the peat or turf, he
exerts an injurious geographical agency, and, as I have already said,
there is no doubt that the immense extension of the inland seas of
Holland in modern times is owing to this and other human imprudences.
"Hundreds of hectares of floating pastures," says our author, "which
have nothing in their appearance to distinguish them from grass lands
resting on solid bog, are found in Overijssel, in North Holland and near
Utrecht. In short, they occur in all deep bogs, and wherever deep water
is left long undisturbed."
In one case, a floating island, which had attached itself to the shore,
continued to float about for a long time after it was torn off by a
flood, and was solid enough to keep a pond of fresh water upon it sweet,
though the water in which it was swimming had become brackish from the
irruption of the sea. After the hay is cut, cattle are pastured upon
those islands, and they sometimes have large trees growing upon them.
When the turf or peat has been cut, leaving water less than a yard deep,
Equisetum limosum grows at once, and is followed by the second class of
marsh plants mentioned above. Their roots do not become detached from
the bottom in such shallow water, but form ordinary turf or peat. These
processes are so rapid that a thickness of from three to six feet of
turf is formed in half a century, and many men have lived to mow grass
where they had fished in their boyhood, and to cut turf twice in the
same spot.
Captain Gilliss says that before Lake Taguataga in Chili was drained,
there were in it islands composed of dead plants matted together to a
thickness of from four to six feet, and with trees of medium size
growing upon them. These islands floated before the wind "with their
trees and browsing cattle."--_United States Naval Astronomical
Expedition to the Southern Hemisphere_, i, pp. 16, 17.
[322] A considerable work of this character is mentioned by Captain
Gilliss as having been executed in Chili, a country to which we should
have hardly looked for an improvement of such a nature. The Lake
Taguataga was partially drained by cutting through a narrow ridge of
land, not at the natural outlet, but upon one side of the lake, and
eight thousand acres of land covered by it were gained for
cultivation.--_U. S. Naval Astronomical Expedition to the Southern
Hemisphere_, i, pp. 16, 17.
[323] _Économie Rurale de la France_, p. 289.
[324] In a note on a former page of this volume I noticed an observation
of Jacini, to the effect that the great Italian lakes discharge
themselves partly by infiltration beneath the hills which bound them.
The amount of such infiltration must depend much upon the hydrostatic
pressure on the walls of the lake basins, and, of course, the lowering
of the surface of these lakes, by diminishing that pressure, would
diminish also the infiltration. It is now proposed to lower the level of
the Lake of Como some feet by deepening its outlet. It is possible that
the effect of this may manifest itself in a diminution of the water in
springs and _fontanili_ or artesian wells in Lombardy. See _Appendix_,
No. 43.
[325] Simonde, speaking of the Tuscan canals, observes: "But inundations
are not the only damage caused by the waters to the plains of Tuscany.
Raised, as the canals are, above the soil, the water percolates through
their banks, penetrates every obstruction, and, in spite of all the
efforts of industry, sterilizes and turns to morasses fields which
nature and the richness of the soil seemed to have designed for the most
abundant harvests. In ground thus pervaded with moisture, or rendered
_cold_, as the Tuscans express it, by the filtration of the canal water,
the vines and the mulberries, after having for a few years yielded fruit
of a saltish taste, rot and perish. The wheat decays in the ground, or
dies as soon as it sprouts. Winter crops are given up, and summer
cultivation tried for a time; but the increasing humidity, and the
saline matter communicated to the earth--which affects the taste of all
its products, even to the grasses, which the cattle refuse to touch--at
last compel the husbandman to abandon his fields, and leave uncultivated
a soil that no longer repays his labor."--_Tableau de l'Agriculture
Toscane._ pp. 11, 12.
[326] _Physikalische Geographie_, p. 288. Draining by driving down
stakes, mentioned in a note in a chapter on the woods, _ante_, is a
process of the same nature.
[327] "The simplest backwoodsman knows by experience that all
cultivation is impossible in the neighborhood of bogs and marshes. Why
is a crop near the borders of a marsh cut off by frost, while a field
upon a hillock, a few stone's throws from it, is spared?"--LARS LEVI
LÆSTADIUS, _Om Uppodlingar i Lappmarken_, pp. 69, 74.
[328] Babinet condemns even the general draining of marshes. "Draining,"
says he, "has been much in fashion for some years. It has been a special
object to dry and fertilize marshy grounds. My opinion has always been
that excessive dryness is thus produced, and that other soils in the
neighborhood are sterilized in proportion."
[329] I ought perhaps to except the Mexicans and the Peruvians, whose
arts and institutions are not yet shown to be historically connected
with those of any more ancient people. The lamentable destruction of so
many memorials of these tribes, by the ignorance and bigotry of the
so-called Christian barbarians who conquered them, has left us much in
the dark as to many points of their civilization; but they seem to have
reached that stage where continued progress in knowledge and in power
over nature is secure, and a few more centuries of independence might
have brought them to originate for themselves most of the great
inventions which the last four centuries have bestowed upon man.
[330] The necessity of irrigation in the great alluvial plain of
Northern Italy is partly explained by the fact that the superficial
stratum of fine earth and vegetable mould is very extensively underlaid
by beds of pebbles and gravel brought down by mountain torrents at a
remote epoch. The water of the surface soil drains rapidly down into
these loose beds, and passes off by subterranean channels to some
unknown point of discharge; but this circumstance alone is not a
sufficient solution. Is it not possible that the habits of vegetables,
grown in countries where irrigation has been immemorially employed, have
been so changed that they require water under conditions of soil and
climate where their congeners, which have not been thus indulgently
treated, do not?
There are some atmospheric phenomena in Northern Italy, which an
American finds it hard to reconcile with what he has observed in the
United States. To an American eye, for instance, the sky of Piedmont,
Lombardy, and the northern coast of the Mediterranean, is always whitish
and curdled, and it never has the intensity and fathomless depth of the
blue of his native heavens. And yet the heat of the sun's rays, as
measured by sensation, and, at the same time, the evaporation, are
greater than they would be with the thermometer at the same point in
America. I have frequently felt in Italy, with the mercury below 60°
Fahrenheit, and with a mottled and almost opaque sky, a heat of solar
irradiation which I can compare to nothing but the scorching sensation
experienced in America at a temperature twenty degrees higher, during
the intervals between showers, or before a rain, when the clear blue of
the sky seems infinite in depth and transparency. Such circumstances may
create a necessity for irrigation where it would otherwise be
superfluous, if not absolutely injurious.
In speaking of the superior apparent clearness of the _sky_ in America,
I confine myself to the concave vault of the heavens, and do not mean to
assert that terrestrial objects are generally visible at greater
distances in the United States than in Italy. Indeed I am rather
disposed to maintain the contrary; for though I know that the lower
strata of the atmosphere in Europe never equal in transparency the air
near the earth in New Mexico, Peru, and Chili, yet I think the accidents
of the coast line of the Riviera, as, for example, between Nice and La
Spezia, and those of the incomparable Alpine panorama seen from Turin,
are distinguishable at greater distances than they would be in the
United States.
[331] In Egypt, evaporation and absorption by the earth are so rapid,
that all annual crops require irrigation during the whole period of
their growth. As fast as the water retires by the subsidence of the
annual inundation, the seed is sown upon the still moist uncovered soil,
and irrigation begins at once. Upon the Nile, you hear the creaking of
the water wheels, and sometimes the movement of steam pumps, through the
whole night, while the poorer cultivators unceasingly ply the simple
_shadoof_, or bucket-and-sweep, laboriously raising the water from
trough to trough by as many as six or seven stages when the river is
low. The bucket is of flexible leather, with a stiff rim, and is emptied
into the trough, not by inverting it like a wooden bucket, but by
putting the hand beneath and pushing the bottom up till the water all
runs out over the brim, or, in other words, by turning the vessel inside
out.
The quantity of water thus withdrawn from the Nile is enormous. Most of
this is evaporated directly from the surface or the superficial strata,
but some moisture percolates down and oozes through the banks into the
river again, while a larger quantity sinks till it joins the slow
current of infiltration by which the Nile water pervades the earth of
the valley to the distance, at some points, of not less than fifty
miles.
[332] "Forests," "woods," and "groves," are very frequently mentioned in
the Old Testament as existing at particular places, and they are often
referred to by way of illustration, as familiar objects. "Wood" is twice
spoken of as a material in the New Testament, but otherwise--at least
according to Cruden--not one of the above words occurs in that volume.
This interesting fact, were other evidence wanting, would go far to
prove that a great change had taken place in this respect between the
periods when the Old Testament and the New were respectively composed;
for the scriptural writers, and the speakers introduced into their
narratives, are remarkable for their frequent allusions to the natural
objects and the social and industrial habits which characterized their
ages and their country. See _Appendix_, No. 44.
Solomon anticipated Chevandier in the irrigation of forest trees: "I
made me pools of water, to water therewith the wood that bringeth forth
trees."--_Ecclesiastes_ ii, 6.
[333] One of these, upon Mount Hor, two stories in height, is still in
such preservation that I found not less than ten feet of water in it in
the month of June, 1851.
The brook Ain Musa, which runs through the city of Petra and finally
disappears in the sands of Wadi el Araba, is a considerable river in
winter, and the inhabitants of that town were obliged to excavate a
tunnel through the rock near the right bank, just above the upper
entrance of the Sik, to discharge a part of its swollen current. The
sagacity of Dr. Robinson detected the necessity of this measure, though
the tunnel, the mouth of which was hidden by brushwood, was not
discovered till some time after his visit. I even noticed unequivocal
remains of a sluice by which the water was diverted to the tunnel near
the arch that crosses the Sik. Immense labor was also expended in
widening the natural channel at several points below the town, to
prevent the damming up and setting back of the water--a fact I believe
not hitherto noticed by travellers.
The Fellahheen above Petra still employ the waters of Ain Musa for
irrigation, and in summer the superficial current is wholly diverted
from its natural channel for that purpose. At this season, the bed of
the brook, which is composed of pebbles, gravel, and sand, is dry in the
Sik and through the town; but the infiltration is such that water is
generally found by digging to a small depth in the channel. Observing
these facts in a visit to Petra in the summer, I was curious to know
whether the subterranean waters escaped again to daylight, and I
followed the ravine below the town for a long distance. Not very far
from the upper entrance of the ravine, arborescent vegetation appeared
upon its bottom, and as soon as the ground was well shaded, a thread of
water burst out. This was joined by others a little lower down, and, at
the distance of a mile from the town, a strong current was formed and
ran down toward Wadi el Araba.
[334] The authorities differ as to the extent of the cultivable and the
cultivated soil of Egypt. Lippincott's, or rather Thomas and Baldwin's,
_Gazetteer_--a work of careful research--estimates "the whole area
comprised in the valley [below the first cataract] and delta," at 11,000
square miles. Smith's _Dictionary of the Bible_, article "Egypt," says:
"Egypt has a superficies of about 9,582 square geographical miles of
soil, which the Nile either does or can water and fertilize. This
computation includes the river and lakes as well as sundry tracts which
can be inundated, and the whole space either cultivated or fit for
cultivation is no more than about 5,626 square miles." By geographical
mile is here meant, I suppose, the nautical mile of sixty to an
equatorial degree, or about 2,025 yards. The whole area, then, by this
estimate, is 12,682 square statute or English miles, that of the space
"cultivated or fit for cultivation," 7,447. Smith's _Dictionary of Greek
and Roman Geography_, article "Ægyptus," gives 2,255 square miles as the
area of the valley between Syene and the bifurcation of the Nile,
exclusive of the Fayoom, which is estimated at 340. The area of the
Delta is stated at 1,976 square miles between the main branches of the
river, and, including the irrigated lands east and west of those
branches, at 4,500 square miles. This latter work does not inform us
whether these are statute or nautical miles, but nautical miles must be
intended.
Other writers give estimates differing considerably from those just
cited. The latest computations I have seen are those in the first volume
of Kremer's _Ægypten_, 1863. This author (pp. 6, 7) assigns to the Delta
an area of 200 square German geographical miles (fifteen to the degree);
to all Lower Egypt, including, of course, the Delta, 400 such miles.
These numbers are equal, respectively, to 4,239 and 8,478 square statute
miles, and the great lagoons are embraced in the areas computed. Upper
Egypt (above Cairo) is said (p. 11) to contain 4,000,000 feddan of
_culturfläche_, or cultivable land. The feddan is stated (p. 37) to
contain 7,333 square piks, the pik being 75 centimètres, and it
therefore corresponds almost exactly to the English acre. Hence,
according to Kremer, the cultivable soil of Upper Egypt is 6,250 square
statute miles, or twice as much as the whole area of the valley between
Syene and the bifurcation of the Nile, according to Smith's _Dictionary
of Greek and Roman Geography_. I suspect that 4,000,000 feddan is
erroneously given as the cultivable area of Upper Egypt alone, when in
fact it should be taken for the arable surface of both Lower and Upper
Egypt; for from the statistical tables in the same volume, it appears
that 3,317,125 feddan, or 5,253 square statute miles, were cultivated,
in both geographical divisions, in the year referred to in the tables,
the date of which is not stated.
The area which the Nile would now cover at high water, if left to
itself, is greater than in ancient times, because the bed of the river
has been elevated, and consequently the lateral spread of the inundation
increased. See SMITH'S _Dictionary of Geography_, article "Ægyptus." But
the industry of the Egyptians in the days of the Pharaohs and the
Ptolomies carried the Nile-water to large provinces which have now been
long abandoned and have relapsed into the condition of a desert.
"Anciently," observes the writer of the article "Egypt" in Smith's
_Dictionary of the Bible_, "2,735 square miles more [about 3,700 square
statute miles] may have been cultivated. In the best days of Egypt,
probably all the land was cultivated that could be made available for
agricultural purposes, and hence we may estimate the ancient arable area
of that country at not less than 11,000 square statute miles, or fully
double its present extent."
[335] A canal has been constructed, and new ones are in progress, to
convey water from the Nile to the city of Suez, and to various points on
the line of the ship canal, with the double purpose of supplying fresh
water to the inhabitants and laborers, and of irrigating the adjacent
soil. The area of land which may be thus reclaimed and fertilized is
very large, but the actual quantity which it will be found economically
expedient to bring under cultivation cannot now be determined.
[336] The so-called spring at Heliopolis is only a thread of water
infiltrated from the Nile or the canals.
[337] The date and the doum palm, the _sont_ and many other acacias, the
caroub, the sycamore, and other trees, grow well in Egypt without
irrigation, and would doubtless spread through the entire valley in a
few years.
[338] Wilkinson has shown that the cultivable soil of Egypt has not been
diminished by encroachment of the desert sands, or otherwise, but that,
on the contrary, it must have been increased since the age of the
Pharaohs. The Gotha _Almanac_ for 1862 states the population of Egypt in
1859 at 5,125,000 souls; but this must be a great exaggeration, even
supposing the estimate to include the inhabitants of Nubia, and of much
other territory not geographically belonging to Egypt. In general, the
population of that country has been estimated at something more than
three millions, or about six hundred to the square mile; but with a
better government and better social institutions, the soil would sustain
a much greater number, and in fact it is believed that in ancient times
its inhabitants were twice, perhaps even thrice, as numerous as at
present.
Wilkinson (_Handbook for Travellers in Egypt_, p. 10) observes that the
total population, which two hundred years ago was estimated at
4,000,000, amounted till lately only to about 1,800,000 souls, having
been reduced since 1800 from 2,500,000 to that number.
[339] Ritter supposes Egypt to have been a sandy desert when it was
first occupied by man. "The first inhabitant of the sandy valley of the
Nile was a desert dweller, as his neighbors right and left, the Libyan,
the nomade Arab, still are. But the civilized people of Egypt
transformed, by canals, the waste into the richest granary of the world;
they liberated themselves from the shackles of the rock and sand desert,
in the midst of which, by a wise distribution of the fluid through the
solid geographical form, by irrigation in short, they created a region
of culture most rich in historical monuments."--_Einleitung zur
allgemeinen vergleichenden Geographie_, pp. 165, 166.
This view seems to me highly improbable; for though, by canals and
embankments, man has done much to modify the natural distribution of the
waters of the Nile, and possibly has even transferred its channel from
one side of the valley to the other, yet the annual inundation is not
his work, and the river must have overflowed its banks and carried
spontaneous vegetation with its waters, as well before as since Egypt
was first occupied by the human family. There is, indeed, some reason to
suppose that man lived upon the banks of the Nile when its channel was
much lower, and the spread of its inundations much narrower than at
present; but wherever its flood reached, there the forest would
propagate itself, and its shores are much more likely to have been
morasses than sands.
[340] _Memorie sui progetti per l'estensione dell' Irrigazione, etc., il
Politecnico_, for January, 1863, p. 6.
[341] NIEL, _L'Agriculture des États Sardes_, p. 232.
[342] NIEL, _Agriculture des États Sardes_, p. 237. Lombardini's
computation just given allows eighty-one cubic mètres per day to the
hectare, which, supposing the season of irrigation to be one hundred
days, is equal to a precipitation of thirty-two inches. But in Lombardy,
water is applied to some crops during a longer period than one hundred
days; and in the _marcite_ it flows over the ground even in winter.
According to Boussingault (_Économie Rurale_, ii, p. 246) grass grounds
ought to receive, in Germany, twenty-one centimètres of water per week,
and with less than half that quantity it is not advisable to incur the
expense of supplying it. The ground is irrigated twenty-five or thirty
times, and if the full quantity of twenty-one centimètres is applied, it
receives about two hundred inches of water, or six times the total
amount of precipitation. Puvis, quoted by Boussingault, after much
research comes to the conclusion that a proper quantity is twenty
centimètres applied twenty-five or thirty times, which corresponds with
the estimate just stated. Puvis adds--and, as our author thinks, with
reason--that this amount might be doubled without disadvantage.
Boussingault observes that rain water is vastly more fertilizing than
the water of irrigating canals, and therefore the supply of the latter
must be greater. This is explained partly by the different character of
the substances held in solution or suspension by the waters of the earth
and of the sky, partly by the higher temperature of the latter, and,
possibly, partly also by the mode of application--the rain being finely
divided in its fall or by striking plants on the ground, river water
flowing in a continuous sheet.
The temperature of the water is thought even more important than its
composition. The sources which irrigate the _marcite_ of
Lombardy--meadows so fertile that less than an acre furnishes grass for
a cow the whole year--are very warm. The ground watered by them never
freezes, and a first crop, for soiling, is cut from it in January or
February. The Canal Cavour, just now commenced--which is to take its
supply from the Po at Chivasso, fourteen or fifteen miles below
Turin--will furnish water of much higher fertilizing power than that
derived from the Dora Baltea and the Sesia, both because it is warmer,
and because it transports a more abundant and a richer sediment than the
latter streams, which are fed by Alpine icefields and melting snows, and
which flow, for long distances, in channels ground smooth and bare by
ancient glaciers, and not now contributing much vegetable mould or fine
slime to their waters.
[343] It belongs rather to agriculture than to geography to discuss the
quality of the crops obtained by irrigation, or the permanent effects
produced by it on the productiveness of the soil. There is no doubt,
however, that all crops which can be raised without watering are
superior in flavor and in nutritive power to those grown by the aid of
irrigation. Garden vegetables, particularly, profusely watered, are so
insipid as to be hardly eatable. Wherever irrigation is practised, there
is an almost irresistible tendency, especially among ignorant
cultivators, to carry it to excess; and in Piedmont and Lombardy, if the
supply of water is abundant, it is so liberally applied as sometimes not
only to injure the quality of the product, but to drown the plants and
diminish the actual weight of the crop.
Professor Liebig, in his _Modern Agriculture_, says: "There is not to be
found in chemistry a more wonderful phenomenon, one which more confounds
all human wisdom, than is presented by the soil of a garden or field. By
the simplest experiment, any one may satisfy himself that rain water
filtered through field or garden soil does not dissolve out a trace of
potash, silicic acid, ammonia, or phosphoric acid. The soil does not
give up to the water one particle of the food of plants which it
contains. The most continuous rains cannot remove from the field, except
mechanically, any of the essential constituents of its fertility."
"The soil not only retains firmly all the food of plants which is
actually in it, but its power to preserve all that may be useful to them
extends much farther. If rain or other water holding in solution
ammonia, potash, and phosphoric and silicic acids, be brought in contact
with soil, these substances disappear almost immediately from the
solution; the soil withdraws them from the water. Only such substances
are completely withdrawn by the soil as are indispensable articles of
food for plants; all others remain wholly or in part in solution."
The first of the paragraphs just quoted is not in accordance with the
alleged experience of agriculturists in those parts of Italy where
irrigation is most successfully applied. They believe that the
constituents of vegetable growth are washed out of the soil by excessive
and long-continued watering. They consider it also established as a fact
of observation, that water which has flowed through or over rich ground
is far more valuable for irrigation than water from the same source,
which has not been impregnated with fertilizing substances by passing
through soils containing them; and, on the other hand, that water, rich
in the elements of vegetation, parts with them in serving to irrigate a
poor soil, and is therefore less valuable as a fertilizer of lower
grounds to which it may afterward be conducted.
The practice of irrigation--except in mountainous countries where
springs and rivulets are numerous--is attended with very serious
economical, social, and political evils. The construction of canals and
their immensely ramified branches, and the grading and scarping of the
ground to be watered, are always expensive operations, and they very
often require an amount of capital which can be commanded only by the
state, by moneyed corporations, or by very wealthy proprietors; the
capacity of the canals must be calculated with reference to the area
intended to be irrigated, and when they and their branches are once
constructed, it is very difficult to extend them, or to accommodate any
of their original arrangements to changes in the condition of the soil,
or in the modes or objects of cultivation; the flow of the water being
limited by the abundance of the source or the capacity of the canals,
the individual proprietor cannot be allowed to withdraw water at will,
according to his own private interest or convenience, but both the time
and the quantity of supply must be regulated by a general system
applicable, as far as may be, to the whole area irrigated by the same
canal, and every cultivator must conform his industry to a plan which
may be quite at variance with his special objects or with his views of
good husbandry. The clashing interests and the jealousies of proprietors
depending on the same means of supply are a source of incessant
contention and litigation, and the caprices or partialities of the
officers who control, or of contractors who farm the canals, lead not
unfrequently to ruinous injustice toward individual landholders. These
circumstances discourage the division of the soil into small properties,
and there is a constant tendency to the accumulation of large estates of
irrigated land in the hands of great capitalists, and consequently to
the dispossession of the small cultivators, who pass from the condition
of owners of the land to that of hireling tillers. The farmers are no
longer yeomen, but peasants. Having no interest in the soil which
composes their country, they are virtually expatriated, and the middle
class, which ought to constitute the real physical and moral strength of
the land, ceases to exist as a rural estate, and is found only among the
professional, the mercantile, and the industrial population of the
cities.
[344] BOUSSINGAULT, _Économie Rurale_, ii, pp. 248, 249.
[345] The cultivation of rice is so prejudicial to health everywhere
that nothing but the necessities of a dense population can justify the
sacrifice of life it costs in countries where it is pursued.
It has been demonstrated by actual experiment, that even in Mississippi,
cotton can be advantageously raised by the white man without danger to
health; and in fact, a great deal of the cotton brought to the Vicksburg
market for some years past has been grown exclusively by white labor.
There is no reason why the cultivation of cotton should be a more
unhealthy occupation in America than it is in other countries where it
was never dreamed of as dangerous, and no well-informed American, in the
Slave States or out of them, believes that the abolition of slavery in
the South would permanently diminish the cotton crop of those States.
[346] _L'Italie à propos de l'Exposition de Paris_, p. 92.
[347] The very valuable memoirs of Lombardini, _Cenni idrografi sulla
Lombardia, Intorno al sistema idraulico del Po_, and other papers on
similar subjects, were published in periodicals little known out of
Italy; and the _Idraulica Pratica_ of Mari has not, I believe, been
translated into French or English. These works, and other sources of
information equally inaccessible out of Italy, have been freely used by
Baumgarten, in a memoir entitled _Notice sur les Rivières de la
Lombardie_, in the _Annales des Ponts et Chaussées_, 1847, 1er sémestre,
pp. 129 _et seqq._, and by Dumont, _Des Travaux Publics dans leurs
Rapports avec l'Agriculture_, note, viii, pp. 269 _et seqq._ For the
convenience of my readers, I shall use these two articles instead of the
original authorities on which they are founded.
[348] Sir John F. W. Herschel, citing Talabot as his authority,
_Physical Geography_ (24).
In an elaborate paper on "Irrigation," printed in the _United States
Patent Report_ for 1860, p. 169, it is stated that the volume of water
poured into the Mediterranean by the Nile in twenty-four hours, at low
water, is 150,566,392,368 cubic mètres; at high water, 705,514,667,440
cubic mètres. Taking the mean of these two numbers, the average daily
delivery of the Nile would be 428,081,059,808 cubic mètres, or more than
550,000,000,000 cubic yards. There is some enormous mistake, probably a
typographical error, in this statement, which makes the delivery of the
Nile seventeen hundred times as great as computed by Talabot, and many
times more than any physical geographer has ever estimated the quantity
supplied by all the rivers on the face of the globe.
[349] The Drac, a torrent emptying into the Isère a little below
Grenoble, has discharged 5,200, the Isère, which receives it,
7,800 cubic yards, and the Durance an equal quantity, per
second.--MONTLUISANT, _Note sur les Desséchements, etc., Annales
des Ponts et Chaussées_, 1833, 2me sémestre, p. 288.
The floods of some other French rivers scarcely fall behind those of the
Rhone. The Loire, above Roanne, has a basin of 2,471 square miles, or
about twice and a half the area of that of the Ardèche. In some of its
inundations it has delivered above 9,500 cubic yards per
second.--BELGRAND, _De l'Influence des Forêts, etc., Annales des Ponts
et Chaussées_, 1854, 1er sémestre, p. 15, note.
[350] The original forests in which the basin of the Ardèche was rich
have been rapidly disappearing, for many years, and the terrific
violence of the inundations which are now laying it waste is ascribed,
by the ablest investigators, to that cause. In an article inserted in
the _Annales Forestières_ for 1843, quoted by Hohenstein, _Der Wald_, p.
177, it is said that about one third of the area of the department had
already become absolutely barren, in consequence of clearing, and that
the destruction of the woods was still going on with great rapidity. New
torrents were constantly forming, and they were estimated to have
covered more than 70,000 acres of good land, or one eighth of the
surface of the department, with sand and gravel.
[351] "There is no example of a coincidence between great floods of the
Ardèche and of the Rhone, all the known inundations of the former having
taken place when the latter was very low."--MARDIGNY, _Mémoire sur les
Inondations des Rivières de l'Ardèche_, p. 26.
I take this occasion to acknowledge myself indebted to the interesting
memoir just quoted for all the statements I make respecting the floods
of the Ardèche, except the comparison of the volume of its waters with
that of the Nile, and the computation with respect to the capacity
required for reservoirs to be constructed in its basin.
[352] In some cases where the bed of rapid Alpine streams is composed of
very hard rock--as is the case in many of the valleys once filled by
ancient glaciers--and especially where they are fed by glaciers not
overhung by crumbling cliffs, the channel may remain almost unchanged
for centuries. This is observable in many of the tributaries of the Dora
Baltea, which drains the valley of the Aosta. Several of these small
rivers are spanned by more or less perfect Roman bridges--one of which,
that over the Lys at Pont St. Martin, is still in good repair and in
constant use. An examination of the rocks on which the abutments of this
and some other similar structures are founded, and of the channels of
the rivers they cross, shows that the beds of the streams cannot have
been much elevated or depressed since the bridges were built. In other
cases, as at the outlet of the Val Tournanche at Chatillon, where a
single rib of a Roman bridge still remains, there is nothing to forbid
the supposition that the deep excavation of the channel may have been
partly effected at a much later period. See _App._, No. 45.
[353] _Mémoire sur les Inondations des Rivières de l'Ardèche_, p. 16.
"The terrific roar, the thunder of the raging torrents proceeds
principally from the stones which are rolled along in the bed of the
stream. This movement is attended with such powerful attrition that, in
the Southern Alps, the atmosphere of valleys where the limestone
contains bitumen, has, at the time of floods, the marked bituminous
smell produced by rubbing pieces of such limestone together."--WESSELY,
_Die Oesterreichischien Alpenländer_, i, p. 113. See _Appendix_, No. 48.
[354] FRISI, _Del modo di regolare i Fiumi e i Torrenti_, pp. 4-19.
[355] SURELL, _Étude sur les Torrents_, pp. 31-36.
[356] CHAMPION, _Les Inondations en France_, iii, p. 156, note.
[357] Notwithstanding this favorable circumstance, the damage done by
the inundation of 1840 in the valley of the Rhone was estimated at
seventy-two millions of francs.--CHAMPION, _Les Inondations en France_,
iv, p. 124.
Several smaller floods of the Rhone, experienced at a somewhat earlier
season of the year in 1846, occasioned a loss of forty-five millions of
francs. "What if," says Dumont, "instead of happening in October, that
is between harvest and seedtime, they had occurred before the crops were
secured? The damage would have been counted by hundreds of
millions."--_Des Travaux Publics_, p. 99, note.
[358] TROY, _Étude sur le Reboisement des Montagnes_, §§ 6, 7, 21.
[359] For accounts of damage from the bursting of reservoirs, see
VALLÉE, _Mémoire sur les Reservoirs d'Alimentation des Canaux, Annales
des Ponts et Chaussées_, 1833, 1er sémestre, p. 261.
[360] Some geographical writers apply the term _bifurcation_ exclusively
to this intercommunication of rivers; others, with more etymological
propriety, use it to express the division of great rivers into branches
at the head of their deltas. A technical term is wanting to designate
the phenomenon mentioned in the text.
[361] MARDIGNY, _Mémoire sur les Inondations de l'Ardèche_, p. 13.
[362] In the case of rivers flowing through wide alluvial plains and
much inclined to shift their beds, like the Po, the embankments often
leave a very wide space between them. The dikes of the Po are sometimes
three or four miles apart.--BAUMGARTEN, after LOMBARDINI, _Annales des
Ponts et Chaussées_, 1847, 1er sémestre, p. 149.
[363] It appears from the investigations of Lombardini that the rate of
elevation of the bed of the Po has been much exaggerated by earlier
writers, and in some parts of its course the change is so slow that its
level may be regarded as nearly constant.--BAUMGARTEN, volume before
cited, pp. 175, et seqq. See _Appendix_, No. 49.
If the western coast of the Adriatic is undergoing a secular depression,
as many circumstances concur to prove, the sinking of the plain near the
coast may both tend to prevent the deposit of sediment in the river bed
by increasing the velocity of its current, and compensate the elevation
really produced by deposits, so that no sensible elevation would result,
though much gravel and slime might be let fall.
[364] To secure the city of Sacramento in California from the
inundations to which it is subject, a dike or levée was built upon the
bank of the river and raised to an elevation above that of the highest
known floods, and it was connected, below the town, with grounds lying
considerably above the river. On one occasion a breach in the dike
occurred above the town at a very high stage of the flood. The water
poured in behind it, and overflowed the lower part of the city, which
remained submerged for some time after the river had retired to its
ordinary level, because the dike, which had been built to keep the water
_out_, now kept it _in_.
According to Arthur Young, on the lower Po, where the surface of the
river has been elevated much above the level of the adjacent fields by
diking, the peasants in his time frequently endeavored to secure their
grounds against threatened devastation through the bursting of the
dikes, by crossing the river when the danger became imminent and opening
a cut in the opposite bank, thus saving their own property by flooding
their neighbors'. He adds, that at high water the navigation of the
river was absolutely interdicted, except to mail and passenger boats,
and that the guards fired upon all others; the object of the prohibition
being to prevent the peasants from resorting to this measure of
self-defence.--_Travels in Italy and Spain_, Nov. 7, 1789.
In a flood of the Po in 1839, a breach of the embankment took place at
Bonizzo. The water poured through and inundated 116,000 acres, or 181
square miles, of the plain, to the depth of from twenty to twenty-three
feet in its lower parts.--BAUMGARTEN, after LOMBARDINI, volume before
cited, p. 152.
[365] MOYENS _de forcer les Torrents de rendre une partie du sol qu'ils
ravagent, et d'empêcher les grandes Inondations_.
[366] The effect of trees and other detached obstructions in checking
the flow of water is particularly noticed by Palissy in his essay on
_Waters and Fountains_, p. 173, edition of 1844. "There be," says he,
"in divers parts of France, and specially at Nantes, wooden bridges,
where, to break the force of the waters and of the floating ice, which
might endamage the piers of the said bridges, they have driven upright
timbers into the bed of the rivers above the said piers, without the
which they should abide but little. And in like wise, the trees which be
planted along the mountains do much deaden the violence of the waters
that flow from them."
[367] I do not mean to say that all rivers excavate their own valleys,
for I have no doubt that in the majority of cases such depressions of
the surface originate in higher geological causes, and hence the valley
makes the river, not the river the valley. But even if we suppose a
basin of the hardest rock to be elevated at once, completely formed,
from the submarine abyss where it was fashioned, the first shower of
rain that falls upon it after it rises to the air, while its waters will
follow the lowest lines of the surface, will cut those lines deeper, and
so on with every successive rain. The disintegrated rock from the upper
part of the basin forms the lower by alluvial deposit, which is
constantly transported farther and farther until the resistance of
gravitation and cohesion balances the mechanical force of the running
water. Thus plains, more or less steeply inclined, are formed, in which
the river is constantly changing its bed, according to the perpetually
varying force and direction of its currents, modified as they are by
ever-fluctuating conditions. Thus the Po is said to have long inclined
to move its channel southward in consequence of the superior mechanical
force of its northern affluents. A diversion of these tributaries from
their present beds, so that they should enter the main stream at other
points and in different directions, might modify the whole course of
that great river. But the mechanical force of the tributary is not the
only element of its influence on the course of the principal stream. The
deposits it lodges in the bed of the latter, acting as simple
obstructions or causes of diversion, are not less important agents of
change.
[368] The distance to which a new obstruction to the flow of a river,
whether by a dam or by a deposit in its channel, will retard its
current, or, in popular phrase, "set back the water," is a problem of
more difficult practical solution than almost any other in hydraulics.
The elements--such as straightness or crookedness of channel, character
of bottom and banks, volume and previous velocity of current, mass of
water far above the obstruction, extraordinary drought or humidity of
seasons, relative extent to which the river may be affected by the
precipitation in its own basin, and by supplies received through
subterranean channels from sources so distant as to be exposed to very
different meteorological influences, effects of clearing and other
improvements always going on in new countries--are all extremely
difficult, and some of them impossible, to be known and measured. In the
American States, very numerous watermills have been erected within a few
years, and there is scarcely a stream in the settled portion of the
country which has not several milldams upon it. When a dam is raised--a
process which the gradual diminution of the summer currents renders
frequently necessary--or when a new dam is built, it often happens that
the meadows above are flowed, or that the retardation of the stream
extends back to the dam next above. This leads to frequent lawsuits.
From the great uncertainty of the facts, the testimony is more
conflicting in these than in any other class of cases, and the obstinacy
with which "water causes" are disputed has become proverbial.
The subterranean courses of the waters form a subject very difficult of
investigation, and it is only recently that its vast importance has been
recognized. The interesting observations of Schmidt on the caves of the
Karst and their rivers throw much light on the underground hydrography
of limestone districts, and serve to explain how, in the low peninsula
of Florida, rivers, which must have their sources in mountains a hundred
or more miles distant, can pour out of the earth in currents large
enough to admit of steamboat navigation to their very basins of
eruption. Artesian wells are revealing to us the existence of
subterranean lakes and rivers sometimes superposed one above another in
successive sheets; but the still more important subject of the
absorption of water by earth and its transmission by infiltration is yet
wrapped in great obscurity.
[369] The sediment of the Po has filled up some lagoons and swamps in
its delta, and converted them into comparatively dry land; but, on the
other hand, the retardation of the current from the lengthening of its
course, and the diminution of its velocity by the deposits at its mouth,
have forced its waters at some higher points to spread in spite of
embankments, and thus fertile fields have been turned into unhealthy and
unproductive marshes.--See BOTTER, _Sulla condizione dei Terreni
Maremmani nel Ferrarese. Annali di Agricoltura, etc._, Fasc. v, 1863.
[370] Deep borings have not detected any essential difference in the
quantity or quality of the deposits of the Nile for forty or fifty, or,
as some compute, for a hundred centuries. From what vast store of rich
earth does this river derive the three or four inches of fertilizing
material which it spreads over the soil of Egypt every hundred years?
Not from the White Nile, for that river drops nearly all its suspended
matter in the broad expansions and slow current of its channel south of
the tenth degree of north latitude. Nor does it appear that much
sediment is contributed by the Bahr-el-Azrek, which flows through
forests for a great part of its course. I have been informed by an old
European resident of Egypt who is very familiar with the Upper Nile,
that almost the whole of the earth with which its waters are charged is
brought down by the Takazzé.
[371] It is very probably true that, as Lombardini supposes, the plain
of Lombardy was anciently covered with forests and morasses (Baumgarten,
l. c. p. 156); but, had the Po remained unconfined, its deposits would
have raised its banks as fast as its bed, and there is no obvious reason
why this plain should be more marshy than other alluvial flats traversed
by great rivers. Its lower course would possibly have become more marshy
than at present, but the banks of its middle and upper course would have
been in a better condition for agricultural use than they now are.
[372] From daily measurements during a period of fourteen years--1827 to
1840--the mean delivery of the Po at Ponte Lagoscuro, below the entrance
of its last tributary, is found to be 1,720 cubic mètres, or 60,745
cubic feet, per second. Its smallest delivery is 186 cubic mètres, or
6,569 cubic feet, its greatest 5,156 cubic mètres, or 182,094 cubic
feet.--BAUMGARTEN, following LOMBARDINI, volume before cited, p. 159.
The average delivery of the Nile being 101,000 cubic feet per second, it
follows that the Po contributes to the Adriatic six tenths as much water
as the Nile to the Mediterranean--a result which will surprise most
readers.
[373] We are quite safe in supposing that the valley of the Nile has
been occupied by man at least 5,000 years. The dates of Egyptian
chronology are uncertain, but I believe no inquirer estimates the age of
the great pyramids at less than forty centuries, and the construction of
such works implies an already ancient civilization.
[374] There are many dikes in Egypt, but they are employed in but a very
few cases to exclude the waters of the inundation. Their office is to
retain the water received at high Nile into the inclosures formed by
them until it shall have deposited its sediment or been drawn out for
irrigation; and they serve also as causeways for interior communication
during the floods. The Egyptian dikes, therefore, instead of forcing the
river, like those of the Po, to transport its sediment to the sea, help
to retain the slime, which, if the flow of the current over the land
were not obstructed, might be carried back into the channel, and at last
to the Mediterranean.
[375] The Mediterranean front of the Delta may be estimated at one
hundred and fifty miles in length. Two cubic miles of earth would more
than fill up the lagoons on the coast, and the remaining ten, even
allowing the mean depth of the water to be twenty fathoms, which is
beyond the truth, would have been sufficient to extend the coast line
about three miles farther seaward, and thus, including the land gained
by the filling up of the lagoons, to add more than five hundred square
miles to the area of Egypt. Nor is this all; for the retardation of the
current, by lengthening the course and consequently diminishing the
inclination of the channel, would have increased the deposit of
suspended matter, and proportionally augmented the total effect of the
embankment.
[376] For the convenience of navigation, and to lessen the danger of
inundation by giving greater directness, and, of course, rapidity to the
current, bends in rivers are sometimes cut off and winding channels made
straight. This process has the same general effects as diking, and
therefore cannot be employed without many of the same results.
This practice has often been resorted to on the Mississippi with
advantage to navigation, but it is quite another question whether that
advantage has not been too dearly purchased by the injury to the banks
at lower points. If we suppose a river to have a navigable course of
1,600 miles as measured by its natural channel, with a descent of 800
feet, we shall have a fall of six inches to the mile. If the length of
channel be reduced to 1,200 miles by cutting off bends, the fall is
increased to eight inches per mile. The augmentation of velocity
consequent upon this increase of inclination is not computable without
taking into account other elements, such as depth and volume of water,
diminution of direct resistance, and the like, but in almost any
supposable case, it would be sufficient to produce great effects on the
height of floods, the deposit of sediment in the channel, on the shores,
and at the outlet, the erosion of banks and other points of much
geographical importance.
The Po, in those parts of its course where the embankments leave a wide
space between, often cuts off bends in its channel and straightens its
course. These short cuts are called _salti_, or leaps, and sometimes
reduce the distance between their termini by several miles. In 1777, the
salto of Cottaro shortened a distance of 7,000 mètres by 5,000, or, in
other words, reduced the length of the channel more than three miles;
and in 1807 and 1810 the two salti of Mezzanone effected a reduction of
distance to the amount of between seven and eight miles.--BAUMGARTEN, l.
c. p. 38.
[377] The fact, that the mixing of salt and fresh water in coast marshes
and lagoons is deleterious to the sanitary condition of the vicinity,
seems almost universally admitted, though the precise reason why a
mixture of both should be more injurious than either alone, is not
altogether clear. It has been suggested that the admission of salt water
to the lagoons and rivers kills many fresh water plants and animals,
while the fresh water is equally fatal to many marine organisms, and
that the decomposition of the remains originates poisonous miasmata.
Other theories however have been proposed. The whole subject is fully
and ably discussed by Dr. Salvagnoli Marchetti in the appendix to his
valuable _Rapporto sul Bonificamento delle Maremme Toscane_. See also
the _Memorie Economico-Statistiche sulle Maremme Toscane_, of the same
author.
[378] This curious fact is thus stated in the preface to Fossombroni
(_Memorie sopra la Val di Chiana_, edition of 1835, p. xiii), from which
also I borrow most of the data hereafter given with respect to that
valley: "It is perhaps not universally known, that the swallows, which
come from the north [south] to spend the summer in our climate, do not
frequent marshy districts with a malarious atmosphere. A proof of the
restoration of salubrity in the Val di Chiana is furnished by these
aerial visitors, which had never before been seen in those low grounds,
but which have appeared within a few years at Forano and other points
similarly situated."
Is the air of swamps destructive to the swallows, or is their absence in
such localities merely due to the want of human habitations, near which
this half-domestic bird loves to breed, perhaps because the house fly
and other insects which follow man are found only in the vicinity of his
dwellings?
In almost all European countries, the swallow is protected, by popular
opinion or superstition, from the persecution to which almost all other
birds are subject. It is possible that this respect for the swallow is
founded upon ancient observation of the fact just stated on the
authority of Fossombroni. Ignorance mistakes the effect for the cause,
and the absence of this bird may have been supposed to be the occasion,
not the consequence, of the unhealthiness of particular localities. This
opinion once adopted, the swallow would become a sacred bird, and in
process of time fables and legends would be invented to give additional
sanction to the prejudices which protected it. The Romans considered the
swallow as consecrated to the Penates, or household gods, and according
to Peretti (_Le Serate del Villaggio_, p. 168) the Lombard peasantry
think it a sin to kill them, because they are _le gallinelle del
Signore_, the chickens of the Lord.
The following little Tuscan _rispetto_ from Gradi (_Racconti Popolari_,
p. 33) well expresses the feeling of the peasantry toward this bird:
O rondinella che passi lo mare
Torna 'ndietro, vo' dirti du' parole;
Dammi 'na penna delle tue bell' ale,
Vo' scrivere 'na lettera al mi' amore;
E quando l' avrò scritta 'n carta bella,
Ti renderò la penna, o rondinella;
E quando l' avrò scritta 'n carta bianca,
Ti renderò la penna che ti manca;
E quando l' avrò scritta in carta d' oro,
Ti renderò la penna al tuo bel volo.
O swallow, that fliest beyond the sea,
Turn back! I would fain have a word with thee.
A feather oh grant, from thy wing so bright!
For I to my sweetheart a letter would write;
And when it is written on paper fine
I'll give thee, O swallow, that feather of thine;
--On paper so white, and I'll give thee back,
O pretty swallow, the pen thou dost lack;
--On paper of gold, and then I'll restore
To thy beautiful pinion the feather once more.
Popular traditions and superstitions are so closely connected with
localities, that, though an emigrant people may carry them to a foreign
land, they seldom survive a second generation. The swallow, however, is
still protected in New England by prejudices of transatlantic origin;
and I remember hearing, in my childhood, that if the swallows were
killed, the cows would give bloody milk.
[379] MOROZZI, _Dello stato antico e moderno del fiume Arno_, ii, p. 42.
[380] MOROZZI, _Dello stato, etc., dell' Arno_, ii, pp. 39, 40.
[381] Torricelli thus expressed himself on this point: "If we content
ourselves with what nature has made practicable to human industry, we
shall endeavor to control, as far as possible, the outlets of these
streams, which, by raising the bed of the valley with their deposits,
will realize the fable of the Tagus and the Pactolus, and truly roll
golden sands for him that is wise enough to avail himself of
them."--FOSSOMBRONI, _Memorie sopra la Val di Chiana_, p. 219.
[382] Arrian observes that at the junction of the Hydaspes and the
Acesines, both of which are described as wide streams, "one very narrow
river is formed of two confluents, and its current is very
swift."--ARRIAN, _Alex. Anab._, vi, 4.
[383] This difficulty has been remedied as to one important river of the
Maremma, the Pecora, by clearings recently executed along its upper
course. "The condition of this marsh and of its affluents are now,
November, 1859, much changed, and it is advisable to prosecute its
improvement by deposits. In consequence of the extensive felling of the
woods upon the plains, hills, and mountains of the territory of Massa
and Scarlino, within the last ten years, the Pecora and other affluents
of the marsh receive, during the rains, water abundantly charged with
slime, so that the deposits within the first division of the marsh are
already considerable, and we may now hope to see the whole marsh and
pond filled up in a much shorter time than we had a right to expect
before 1850. This circumstance totally changes the terms of the
question, because the filling of the marsh and pond, which then seemed
almost impossible on account of the small amount of sediment deposited
by the Pecora, has now become practicable."--SALVAGNOLI, _Rapporto sul
Bonificamento delle Maremme Toscane_, pp. li, lii.
The annual amount of sediment brought down by the rivers of the Maremma
is computed at more than 12,000,000 cubic yards, or enough to raise an
area of four square miles one yard. Between 1830 and 1859 more than
three times that quantity was deposited in the marsh and shoal water
lake of Castiglione alone.--SALVAGNOLI, _Raccolta di Documenti_, pp. 74,
75.
[384] The tide rises ten inches on the coast of Tuscany. See Memoir by
FANTONI, in the appendix to SALVAGNOLI, _Rapporto_, p. 189.
On the tides of the Mediterranean, see BÖTTGER, _Das Mittelmeer_, p.
190. Not having Admiral Smyth's Mediterranean--on which Böttger's work
is founded--at hand, I do not know how far credit is due to the former
author for the matter contained in the chapter referred to.
[385] In Catholic countries, the discipline of the church requires a
_meagre_ diet at certain seasons, and as fish is not flesh, there is a
great demand for that article of food at those periods. For the
convenience of monasteries and their patrons, and as a source of
pecuniary emolument to ecclesiastical establishments and sometimes to
lay proprietors, great numbers of artificial fish ponds were created
during the Middle Ages. They were generally shallow pools formed by
damming up the outlet of marshes, and they were among the most fruitful
sources of endemic disease, and of the peculiar malignity of the
epidemics which so often ravaged Europe in those centuries. These ponds,
in religious hands, were too sacred to be infringed upon for sanitary
purposes, and when belonging to powerful lay lords they were almost as
inviolable. The rights of fishery were a standing obstacle to every
proposal of hydraulic improvement, and to this day large and fertile
districts in Southern Europe remain sickly and almost unimproved and
uninhabited, because the draining of the ponds upon them would reduce
the income of proprietors who derive large profits by supplying the
faithful, in Lent, with fish, and with various species of waterfowl
which, though very fat, are, ecclesiastically speaking, meagre.
[386] Macchiavelli advised the Government of Tuscany "to provide that
men should restore the wholesomeness of the soil by cultivation, and
purify the air by fires."--SALVAGNOLI, _Memorie_, p. 111.
[387] GIORGINI, _Sur les causes de l'Insalubrité de l'air dans le
voisinage des marais, etc., lue à l'Académie des Sciences à Paris_, le
12 Juillet, 1825. Reprinted in SALVAGNOLI, _Rapporto, etc._, appendice,
p. 5, _et seqq._
[388] See the careful estimates of ROSET, _Moyens de forcer les
Torrents, etc._, pp. 42, 44.
[389] Rivers which transport sand, gravel, pebbles, heavy mineral matter
in short, tend to raise their own beds; those charged only with fine,
light earth, to cut them deeper. The prairie rivers of the West have
deep channels, because the mineral matter they carry down is not heavy
enough to resist the impulse of even a moderate current, and those
tributaries of the Po which deposit their sediment in the lakes--the
Ticino, the Adda, the Oglio, and the Mincio--flow, in deep cuts, for the
same reason.--BAUMGARTEN, l. c., p. 132.
[390] "The stream carries this mud, &c., at first farther to the east,
and only lets it fall where the force of the current becomes weakened.
This explains the continual advance of the land seaward along the Syrian
coast, in consequence of which Tyre and Sidon no longer lie on the
shore, but some distance inland. That the Nile contributes to this
deposit may easily be seen, even by the unscientific observer, from the
stained and turbid character of the water for many miles from its
mouths. A somewhat alarming phenomenon was observed in this neighborhood
in 1801, on board the English frigate Romulus, Captain Culverhouse, on a
voyage from Acre to Abukir. Dr. E. D. Clarke, who was a passenger on
board this ship, thus describes it:
"'26th July.--To-day, Sunday, we accompanied the captain to the wardroom
to dine, as usual, with his officers. While we were at table, we heard
the sailors who were throwing the lead suddenly cry out: "Three and a
half!" The captain sprang up, was on deck in an instant, and, almost at
the same moment, the ship slackened her way, and veered about. Every
sailor on board supposed she would ground at once. Meanwhile, however,
as the ship came round, the whole surface of the water was seen to be
covered with thick, black mud, which extended so far that it appeared
like an island. At the same time, actual land was nowhere to be
seen--not even from the masthead--nor was any notice of such a shoal to
be found on any chart on board. The fact is, as we learned afterward,
that a stratum of mud, stretching from the mouths of the Nile for many
miles out into the open sea, forms a movable deposit along the Egyptian
coast. If this deposit is driven forward by powerful currents, it
sometimes rises to the surface, and disturbs the mariner by the sudden
appearance of shoals where the charts lead him to expect a considerable
depth of water. But these strata of mud are, in reality, not in the
least dangerous. As soon as a ship strikes them they break up at once,
and a frigate may hold her course in perfect safety where an
inexperienced pilot, misled by his soundings, would every moment expect
to be stranded.'"--BÖTTGER, _Das Mittelmeer_, pp. 188, 189.
[391] The caves of Carniola receive considerable rivers from the surface
of the earth, which cannot, in all cases, be identified with streams
flowing out of them at other points, and like phenomena are not uncommon
in other limestone countries.
The cases are certainly not numerous where marine currents are known to
pour continuously into cavities beneath the surface of the earth, but
there is at least one well-authenticated instance of this sort--that of
the mill streams at Argostoli in the island of Cephalonia. It had been
long observed that the sea water flowed into several rifts and cavities
in the limestone rocks of the coast, but the phenomenon has excited
little attention until very recently. In 1833, three of the entrances
were closed, and a regular channel, sixteen feet long and three feet
wide, with a fall of three feet, was cut into the mouth of a larger
cavity. The sea water flowed into this canal, and could be followed
eighteen or twenty feet beyond its inner terminus, when it disappeared
in holes and clefts in the rock.
In 1858, the canal had been enlarged to the width of five feet and a
half, and a depth of a foot. The water pours rapidly through the canal
into an irregular depression and forms a pool, the surface of which is
three or four feet below the adjacent soil, and about two and a half or
three feet below the level of the sea. From this pool it escapes through
several holes and clefts in the rock, and has not yet been found to
emerge elsewhere.
There is a tide at Argostoli of about six inches in still weather, but
it is considerably higher with a south wind. I do not find it stated
whether water flows through the canal into the cavity at low tide, but
it distinctly appears that there is no refluent current, as of course
there could not be from a basin so much below the sea. Mousson found the
delivery through the canal to be at the rate of 24.88 cubic feet to the
second; at what stage of the tide does not appear. Other mills of the
same sort have been erected, and there appear to be several points on
the coast where the sea flows into the land.
Various hypotheses have been suggested to explain this phenomenon, some
of which assume that the water descends to a great depth beneath the
crust of the earth, but the supposition of a difference of level in the
surface of the sea on the opposite sides of the island, which seems
confirmed by other circumstances, is the most obvious method of
explaining these singular facts. If we suppose the level of the water on
one side of the island to be raised by the action of currents three or
four feet higher than on the other, the existence of cavities and
channels in the rock would easily account for a subterranean current
beneath the island, and the apertures of escape might be so deep or so
small as to elude observation. See _Aus der Natur_, vol. 19, pp. 129,
_et seqq._ See _Appendix_, No. 53.
[392] "The affluents received by the Seine below Rouen are so
inconsiderable, that the augmentation of the volume of that river must
be ascribed principally to springs rising in its bed. This is a point of
which engineers now take notice, and M. Belgrand, the able officer
charged with the improvement of the navigation of the Seine between
Paris and Rouen, has devoted much attention to it."--BABINET, _Études et
Lectures_, iii, p. 185.
On page 232 of the volume just quoted, the same author observes: "In the
lower part of its course, from the falls of the Oise, the Seine receives
so few important affluents, that evaporation alone would suffice to
exhaust all the water which passes under the bridges of Paris."
This supposes a much greater amount of evaporation than has been usually
computed, but I believe it is well settled that the Seine conveys to the
sea much more water than is discharged into it by all its superficial
branches.
[393] Girard and Duchatelet maintain that the subterranean waters of
Paris are absolutely stagnant. See their report on drainage by artesian
wells, _Annales des Ponts et Chaussées_, 1833, 2me sémestre, pp. 313,
_et seqq._
This opinion, if locally true, cannot be generally so, for it is
inconsistent with the well-known fact that the very first eruption of
water from a boring often brings up leaves and other objects which must
have been carried into the underground reservoirs by currents.
[394] _Physikalische Geographie_, p. 286. It does not appear whether
this inference is Mariotte's or Wittwer's. I suppose it is a conclusion
of the latter.
[395] _Physical Geography of the Sea._ Tenth edition. London, 1861, §
274.
[396] PARAMELLE, _Quellenkunde, mit einem Vorwort von_ B. COTTA, 1856.
[397] _Études et Lectures_, vi, p. 118.
[398] "The area of soil dried by draining is constantly increasing, and
the water received by the surface from atmospheric precipitation is
thereby partly conducted into new channels, and, in general, carried off
more rapidly than before. Will not this fact exert an influence on the
condition of many springs, whose basin of supply thus undergoes a
partial or complete transformation? I am convinced that it will, and it
is important to collect data for solving the question." BERNHARD COTTA,
Preface to PARAMELLE, _Quellenkunde_ (German translation), pp. vii,
viii. See _Appendix_, No. 54.
[399] See the interesting observations of KRIEGK on this subject,
_Schriften zur allgemeinen Erdkunde_, cap. iii, § 6, and especially the
passages in RITTER'S _Erdkunde_, vol. i, there referred to.
Laurent, (_Mémoires sur le Sahara Oriental_, pp. 8, 9), in speaking of a
river at El-Faid, "which, like all those of the desert, is, most of the
time, without water," observes, that many wells are dug in the bed of
the river in the dry season, and that the subterranean current thus
reached appears to extend itself laterally, at about the same level, at
least a kilomètre from the river, as water is found by digging to the
depth of twelve or fifteen mètres at a village situated at that distance
from the bank.
The most remarkable case of infiltration known to me by personal
observation is the occurrence of fresh water in the beach sand on the
eastern side of the Gulf of Akaba, the eastern arm of the Red Sea. If
you dig a cavity in the beach near the sea level, it soon fills with
water so fresh as not to be undrinkable, though the sea water two or
three yards from it contains even more than the average quantity of
salt. It cannot be maintained that this is sea water freshened by
filtration through a few feet or inches of sand, for salt water cannot
be deprived of its salt by that process. It can only come from the
highlands of Arabia, and it would seem that there must exist some large
reservoir in the interior to furnish a supply which, in spite of
evaporation, holds out for months after the last rains of winter, and
perhaps even through the year. I observed the fact in the month of June.
The precipitation in the mountains that border the Red Sea is not known
by pluviometric measurement, but the mass of debris brought down the
ravines by the torrents proves that their volume must be large. The
proportion of surface covered by sand and absorbent earth, in Arabia
Petræa and the neighboring countries, is small, and the mountains drain
themselves rapidly into the wadies or ravines where the torrents are
formed; but the beds of earth and disintegrated rock at the bottom of
the valleys are of so loose and porous texture, that a great quantity of
water is absorbed in saturating them before a visible current is formed
on their surface. In a heavy thunder storm, accompanied by a deluging
rain, which I witnessed at Mount Sinai in the month of May, a large
stream of water poured, in an almost continuous cascade, down the steep
ravine north of the convent, by which travellers sometimes descend from
the plateau between the two peaks, but after reaching the foot of the
mountain, it flowed but a few yards before it was swallowed up in the
sands.
[400] It is conceivable that in large and shallow subterranean basins
the superincumbent earth may rest upon the water and be partly supported
by it. In such case the weight of the earth would be an additional, if
not the sole, cause of the ascent of the water through the tubes of
artesian wells. The elasticity of gases in the cavities may also aid in
forcing up water.
A French engineer, M. Mullot, invented a simple method of bringing to
the surface water from any one of several successive accumulations at
different depths, or of raising it, unmixed, from two or more of them at
once. It consists in employing concentric tubes, one within the other,
leaving a space for the rise of water between them, and reaching each to
the sheet from which it is intended to draw.
[401] Many more or less probable conjectures have been made on this
subject, but thus far I am not aware that any of the apprehended results
have been actually shown to have happened. In an article in the _Annales
des Ponts et Chaussées_ for July and August, 1839, p. 131, it was
suggested that the sinking of the piers of a bridge at Tours in France
was occasioned by the abstraction of water from the earth by artesian
wells, and the consequent withdrawal of the mechanical support it had
previously given to the strata containing it. A reply to this article
will be found in VIOLETT, _Théorie des Puits Artésiens_, p. 217.
In some instances the water has rushed up with a force which seemed to
threaten the inundation of the neighborhood, and even the washing away
of much soil; but in those cases the partial exhaustion of the supply,
or the relief of hydrostatic or elastic pressure, has generally produced
a diminution of the flow in a short time, and I do not know that any
serious evil has ever been occasioned in this way.
[402] See a very interesting account of these wells, and of the workmen
who clean them out when obstructed by sand brought up with the water, in
Laurent's memoir on the artesian wells recently bored by the French
Government in the Algerian desert, _Mémoire sur le Sahara Oriental,
etc._, pp. 19, _et seqq._ Some of the men remained under water from two
minutes to two minutes and forty seconds. Several officers are quoted as
having observed immersions of three minutes' duration, and M. Berbrugger
alleges that he witnessed one of five minutes and fifty-five seconds.
The shortest of these periods is longer than the best pearl diver can
remain below the surface of salt water. The wells of the Sahara are from
twenty to eighty mètres deep.
It has often been asserted that the ancient Egyptians were acquainted
with the art of boring artesian wells. Parthey, describing the Little
Oasis, mentions ruins of a Roman aqueduct, and observes: "It appears
from the recent researches of Aim, a French engineer, that these
aqueducts are connected with old artesian wells, the restoration of
which would render it practicable to extend cultivation much beyond its
present limits. This agrees with ancient testimony. It is asserted that
the inhabitants of the oases sunk wells to the depth of 200, 300, and
even 500 ells, from which affluent streams of water poured out. See
OLYMPIODORUS in _Photii Bibl._, cod. 80, p. 61, l. 17, ed.
Bekk."--PARTHEY, _Wanderungen_, ii, p. 528.
In a paper entitled, _Note relative à l'execution d'un Puits Artésien en
Egypte sous la XVIII dynastie_, presented to the Académie des
Inscriptions et Belles Lettres, on the 12th of November, 1852, M.
Lenormant endeavors to show that a hieroglyphic inscription found at
Contrapscelcis proves the execution of a work of this sort in the Nubian
desert, at the period indicated in the title to his paper. The
interpretation of the inscription is a question for Egyptologists; but
if wells were actually bored through the rock by the Egyptians after the
Chinese or the European fashion, it is singular that among the numerous
and minute representations of their industrial operations, painted or
carved on the walls of their tombs, no trace of the processes employed
for so remarkable and important a purpose should have been discovered.
See _Appendix_, No. 56.
It is certain that artesian wells have been common in China from a very
remote antiquity, and the simple method used by the Chinese--where the
borer is raised and let fall by a rope, instead of a rigid rod--has been
lately been employed in Europe with advantage. Some of the Chinese wells
are said to be 3,000 feet deep; that of Neusalzwerk in Silesia--the
deepest in Europe--is 2,300. A well was bored at St. Louis, in Missouri,
a few years ago, to supply a sugar refinery, to the depth of 2,199 feet.
This was executed by a private firm in three years, at the expense of
only $10,000. Another has since been bored at the State capitol at
Columbus, Ohio, 2,500 feet deep, but without obtaining the desired
supply of water.
[403] "In the anticipation of our success at Oum-Thiour, every thing had
been prepared to take advantage of this new source of wealth without a
moment's delay. A division of the tribe of the Selmia, and their sheikh,
Aïssa ben Shâ, laid the foundation of a village as soon as the water
flowed, and planted twelve hundred date palms, renouncing their
wandering life to attach themselves to the soil. In this arid spot, life
had taken the place of solitude, and presented itself, with its smiling
images, to the astonished traveller. Young girls were drawing water at
the fountain; the flocks, the great dromedaries with their slow pace,
the horses led by the halter, were moving to the watering trough; the
hounds and the falcons enlivened the group of party-colored tents, and
living voices and animated movement had succeeded to silence and
desolation."--LAURENT, _Mémoires sur le Sahara_, p. 85.
[404] The variety of hues and tones in the local color of the desert is,
I think, one of the phenomena which most surprise and interest a
stranger to those regions. In England and the United States, rock is so
generally covered with moss or earth, and earth with vegetation, that
untravelled Englishmen and Americans are not very familiar with naked
rock as a conspicuous element of landscape. Hence, in their conception
of a bare cliff or precipice, they hardly ascribe definite color to it,
but depict it to their imagination as wearing a neutral tint not
assimilable to any of the hues with which nature tinges her atmospheric
or paints her organic creations. There are certainly extensive desert
ranges, chiefly limestone formations, where the surface is either white,
or has weathered down to a dull uniformity of tone which can hardly be
called color at all; and there are sand plains and drifting hills of
wearisome monotony of tint. But the chemistry of the air, though it may
tame the glitter of the limestone to a dusky gray, brings out the green
and brown and purple of the igneous rocks, and the white and red and
blue and violet and yellow of the sandstone. Many a cliff in Arabia
Petræa is as manifold in color as the rainbow, and the veins are so
variable in thickness and inclination, so contorted and involved in
arrangement, as to bewilder the eye of the spectator like a disk of
party-colored glass in rapid revolution.
In the narrower wadies, the mirage is not common; but on broad expanses,
as at many points between Cairo and Suez, and in Wadi el Araba, it mocks
you with lakes and land-locked bays, studded with islands and fringed
with trees, all painted with an illusory truth of representation
absolutely indistinguishable from the reality. The checkered earth, too,
is canopied with a heaven as variegated as itself. You see, high up in
the sky, rosy clouds at noonday, colored probably by reflection from the
ruddy mountains, while near the horizon float cumuli of a transparent
ethereal blue, seemingly balled up out of the clear cerulean substance
of the firmament, and detached from the heavenly vault, not by color or
consistence, but solely by the light and shade of their prominences.
[405] _[OE]uvres de Palissy, Des Eaux et Fontaines_, p. 157.
[406] Id., p. 166. See _Appendix_, No. 57.
[407] BABINET, _Études et Lectures sur les Sciences d'Observation_, ii,
p. 225. Our author precedes his account of his method with a complaint
which most men who indulge in thinking have occasion to repeat many
times in the course of their lives. "I will explain to my readers the
construction of artificial fountains according to the plan of the famous
Bernard de Palissy, who, a hundred and fifty [three hundred] years ago,
came and took away from me, a humble academician of the nineteenth
century, this discovery which I had taken a great deal of pains to make.
It is enough to discourage all invention when one finds plagiarists in
the past as well as in the future!" (P. 224.)
[408] M. G. DUMAS, _La Science des Fontaines_, 1857.
[409] In the curiously variegated sandstone of Arabia Petræa--which is
certainly a reaggregation of loose sand derived from particles of older
rocks--the contiguous veins frequently differ very widely in color, but
not sensibly in specific gravity or in texture; and the singular way in
which they are now alternated, now confusedly intermixed, must be
explained otherwise than by the weight of the respective grains which
compose them. They seem, in fact, to have been let fall by water in
violent ebullition or tumultuous mechanical agitation, or by a
succession of sudden aquatic or aerial currents flowing in different
directions and charged with differently colored matter.
[410] _De Bodem van Nederland_, i, pp. 243, 246-377, _et seqq._ See also
the arguments of Brémontier as to the origin of the dune sands of
Gascony, _Annales des Ponts et Chaussées_, 1833, 1er sémestre, pp. 158,
161. Brémontier estimates the sand annually thrown up on that coast at
five cubic toises and two feet to the running toise (ubi supra, p. 162),
or rather more than two hundred and twenty cubic feet to the running
foot. Laval, upon observations continued through seven years, found the
quantity to be twenty-five mètres per running mètre, which is equal to
two hundred and sixty-eight cubic feet to the running foot.--_Annales
des Ponts et Chaussées_, 1842, 2me sémestre, p. 229. These computations
make the proportion of sand deposited on the coast of Gascony three or
four times as great as that observed by Andresen on the shores of
Jutland. Laval estimates the total quantity of sand annually thrown up
on the coast of Gascony at 6,000,000 cubic mètres, or more than
7,800,000 cubic yards.
[411] _De Bodem van Nederland_, i, p. 339.
[412] The conditions favorable to the production of sand from
disintegrated rock, by causes now in action, are perhaps nowhere more
perfectly realized than in the Sinaitic Peninsula. The mountains are
steep and lofty, unprotected by vegetation or even by a coating of
earth, and the rocks which compose them are in a shattered and
fragmentary condition. They are furrowed by deep and precipitous
ravines, with beds sufficiently inclined for the rapid flow of water,
and generally without basins in which the larger blocks of stone rolled
by the torrents can be dropped and left in repose; there are severe
frosts and much snow on the higher summits and ridges, and the winter
rains are abundant and heavy. The mountains are principally of igneous
formation, but many of the less elevated peaks are capped with
sandstone, and on the eastern slope of the peninsula you may sometimes
see, at a single glance, several lofty pyramids of granite, separated by
considerable intervals, and all surmounted by horizontally stratified
deposits of sandstone often only a few yards square, which correspond to
each other in height, are evidently contemporaneous in origin, and were
once connected in continuous beds. The degradation of the rock on which
this formation rests is constantly bringing down masses of it, and
mingling them with the basaltic, porphyritic, granitic, and calcareous
fragments which the torrents carry down to the valleys, and, through
them, in a state of greater or less disintegration, to the sea. The
quantity of sand annually washed into the Red Sea by the larger torrents
of the Lesser Peninsula, is probably at least equal to that contributed
to the ocean by any streams draining basins of no greater extent.
Absolutely considered, then, the mass may be said to be large, but it is
apparently very small as compared with the sand thrown up by the German
Ocean and the Atlantic on the coasts of Denmark and of France. There
are, indeed, in Arabia Petræa, many torrents with very short courses,
for the sea waves in many parts of the peninsular coast wash the base of
the mountains. In these cases, the debris of the rocks do not reach the
sea in a sufficiently comminuted condition to be entitled to the
appellation of sand, or even in the form of well-rounded pebbles. The
fragments retain their angular shape, and, at some points on the coast,
they become cemented together by lime or other binding substances held
in solution or mechanical suspension in the sea water, and are so
rapidly converted into a singularly heterogeneous conglomerate, that one
deposit seems to be consolidated into a breccia before the next winter's
torrents cover it with another.
In the northern part of the peninsula there are extensive deposits of
sand intermingled with agate pebbles and petrified wood, but these are
evidently neither derived from the Sinaitic group, nor products of local
causes known to be now in action.
I may here notice the often repeated but mistaken assertion, that the
petrified wood of the Western Arabian desert consists wholly of the
stems of palms, or at least of endogenous vegetables. This is an error.
I have myself picked up in that desert, within the space of a very few
square yards, fragments both of fossil palms, and of at least two
petrified trees distinctly marked as of exogenous growth both by annular
structure and by knots. In ligneous character, one of these almost
precisely resembles the grain of the extant beech, and this specimen was
wormeaten before it was converted into silex.
[413] BÖTTGER, _Das Mittelmeer_, p. 128.
[414] The testimony of divers and of other observers on this point is
conflicting, as might be expected from the infinite variety of
conditions by which the movement of water is affected. It is generally
believed that the action of the wind upon the water is not perceptible
at greater depths than from fifteen feet in ordinary, to eighty or
ninety in extreme cases; but these estimates are probably very
considerably below the truth. Andresen quotes Brémontier as stating that
the movement of the waves sometimes extends to the depth of five hundred
feet, and he adds that others think it may reach to six or even seven
hundred feet below the surface.--ANDRESEN, _Om Klitformationen_, p. 20.
Many physicists now suppose that the undulations of great bodies of
water reach even deeper. But a movement of undulation is not necessarily
a movement of translation, and besides, there is very frequently an
undertow, which tends to carry suspended bodies out to sea as powerfully
as the superficial waves to throw them on shore. Sandbanks sometimes
recede from the coast, instead of rolling toward it. Reclus informs us
that the Mauvaise, a sandbank near the Point de Grave, on the Atlantic
coast of France, has moved five miles to the west in less than a
century.--_Revue des Deux Mondes_, for December, 1862, p. 905.
The action of currents may, in some cases, have been confounded with
that of the waves. Sea currents, strong enough, possibly, to transport
sand for some distance, flow far below the surface in parts of the open
ocean, and in narrow straits they have great force and velocity. The
divers employed at Constantinople in 1853 found in the Bosphorus, at the
depth of twenty-five fathoms and at a point much exposed to the wash
from Galata and Pera, a number of bronze guns supposed to have belonged
to a ship of war blown up about a hundred and fifty years before. These
guns were not covered by sand or slime, though a crust of earthy matter,
an inch in thickness, adhered to their upper surfaces, and the bottom of
the strait appeared to be wholly free from sediment. The current was so
powerful at this depth that the divers were hardly able to stand, and a
keg of nails, purposely dropped into the water, in order that its
movements might serve as a guide in the search for a bag of coin
accidentally lost overboard from a ship in the harbor, was rolled by the
stream several hundred yards before it stopped.
[415] Few seas have thrown up so much sand as the shallow German Ocean;
but there is some reason to think that the amount of this material now
cast upon its northern shores is less than at some former periods,
though no extensive series of observations on this subject has been
recorded. On the Spit of Agger, at the present outlet of the Liimfjord,
Andresen found the quantity during ten years, on a beach about five
hundred and seventy feet broad, equal to an annual deposit of an inch
and a half over the whole surface.--_Om Klitformationen_, p. 56.
This gives seventy-one and a quarter cubic feet to the running foot--a
quantity certainly much smaller than that cast up by the same sea on the
shores of the Dano-German duchies and of Holland, and, as we have seen,
scarcely one fourth of that deposited by the Atlantic on the coast of
Gascony. See _ante_, p. 453, note.
[416] Sand heaps, three and even six hundred feet high, are indeed
formed by the wind, but this is effected by driving the particles up an
inclined plane, not by lifting them. Brémontier, speaking of the sand
hills on the western coast of France, says: "The particles of sand
composing them are not large enough to resist wind of a certain force,
nor small enough to be taken up by it, like dust; they only roll along
the surface from which they are detached, and, though moving with great
velocity, they rarely rise to a greater height than three or four
inches."--_Mémoire sur les Dunes, Annales des Ponts et Chaussées_, 1833,
1er sémestre, p. 148.
Andresen says that a wind, having a velocity of forty feet per second,
is strong enough to raise particles of sand as high as the face and eyes
of a man, but that, in general, it rolls along the ground, and is
scarcely ever thrown more than to the height of a couple of yards from
the surface. Even in these cases, it is carried forward by a hopping,
not a continuous, motion; for a very narrow sheet or channel of water
stops the drift entirely, all the sand dropping into it until it is
filled up.
The character of the motion of sand drifts is well illustrated by an
interesting fact not much noticed hitherto by travellers in the East. In
situations where the sand is driven through depressions in rock beds, or
over deposits of silicious pebbles, the surface of the stone is worn and
smoothed much more effectually than it could be by running water, and
you may pick up, in such localities, rounded, irregularly broken
fragments of agate, which have received from the attrition of the sand
as fine a polish as could be given them by the wheel of the lapidary.
Very interesting observations on the polishing of hard stones by
drifting sand will be found in the Geological Report of William P.
Blake: _Pacific Railroad Report_, vol. v, pp. 92, 230, 231. The same
geologist observes, p. 242, that the sand of the Colorado desert does
not rise high in the air, but bounds along on the surface or only a few
inches above it.
[417] Wilkinson says that, in much experience in the most sandy parts of
the Libyan desert, and much inquiry of the best native sources, he never
saw or heard of any instance of danger to man or beast from the mere
accumulation of sand transported by the wind. Chesney's observations in
Arabia, and the testimony of the Bedouins he consulted, are to the same
purpose. The dangers of the simoom are of a different character, though
they are certainly aggravated by the blinding effects of the light
particles of dust and sand borne along by it, and by that of the
inhalation of them upon the respiration.
[418] In the narrow valley of the Nile, bounded as it is, above the
Delta, by high cliffs, all air currents from the northern quarter become
north winds, though, of course varying in partial direction, in
conformity with the sinuosities of the valley. Upon the desert plateau
they incline westward, and have already borne into the valley the sands
of the eastern banks, and driven those of the western quite out of the
Egyptian portion of the Nile basin.
[419] "The North African desert falls into two divisions: the Sahel, or
western, and the Sahar, or eastern. The sands of the Sahar were, at a
remote period, drifted to the west. In the Sahel, the prevailing east
winds drive the sand-ocean with a progressive westward motion. The
eastern half of the desert is swept clean."--NAUMANN, _Geognosie_, ii,
p. 1173.
[420] In parts of the Algerian desert, some efforts are made to retard
the advance of sand dunes which threaten to overwhelm villages. "At
Debila," says Laurent, "the lower parts of the lofty dunes are planted
with palms, * * * but they are constantly menaced with burial by the
sands. The only remedy employed by the natives consists in little dry
walls of crystallized gypsum, built on the crests of the dunes, together
with hedges of dead palm leaves. These defensive measures are aided by
incessant labor; for every day the people take up in baskets the sand
blown over to them the night before and carry it back to the other side
of the dune."--_Mémoires sur le Sahara_, p. 14.
[421] Organic constituents, such as comminuted shells, and silicious and
calcareous exuviæ of infusorial animals and plants, are sometimes found
mingled in considerable quantities with mineral sands. These are usually
the remains of aquatic vegetables or animals, but not uniformly so, for
the microscopic organisms, whose flinty cases enter so largely into the
sandbeds of the Mark of Brandenburg, are still living and prolific in
the dry earth. See WITTWER, _Physikalische Geographie_, p. 142.
The desert on both sides of the Nile is inhabited by a land snail, and
thousands of its shells are swept along and finally buried in the drifts
by every wind. Every handful of the sand contains fragments of them.
FORCHHAMMER, in LEONHARD Und BRONN's _Jahrbuch_, 1841, p. 8, says of the
sand hills of the Danish coast: "It is not rare to find, high in the
knolls, marine shells, and especially those of the oyster. They are due
to the oyster eater [_Hæmalopus ostralegus_], which carries his prey to
the top of the dunes to devour it." See also STARING, _De Bodem van_, N.
I. p. 321.
[422] There are various reasons why the formation of dunes is confined
to low shores, and this law is so universal, that when bluffs are
surmounted by them, there is always cause to suspect upheaval, or the
removal of a sloping beach in front of the bluff, after the dunes were
formed. Bold shores are usually without a sufficient beach for the
accumulation of large deposits; they are commonly washed by a sea too
deep to bring up sand from its bottom; their abrupt elevation, even if
moderate in amount, would still be too great to allow ordinary winds to
lift the sand above them; and their influence in deadening the wind
which blows toward them would even more effectually prevent the raising
of sand from the beach at their foot.
Forchhammer, describing the coast of Jutland, says that, in high winds,
"one can hardly stand upon the dunes, except when they are near the
water line and have been cut down perpendicularly by the waves. Then the
wind is little or not at all felt--a fact of experience very common on
our coasts, observed on all the steep shore bluffs of two hundred feet
in height, and, in the Faroe Islands, on precipices two thousand feet
high. In heavy gales in those islands, the cattle fly to the very edge
of the cliffs for shelter, and frequently fall over. The wind, impinging
against the vertical wall, creates an ascending current which shoots
somewhat past the crest of the rock, and thus the observer or the animal
is protected against the tempest by a barrier of air."--LEONHARD und
BRONN, _Jahrbuch_, 1841, p. 3.
The calming, or rather diversion, of the wind by cliffs extends to a
considerable distance in front of them, and no wind would have
sufficient force to raise the sand vertically, parallel to the face of a
bluff, even to the height of twenty feet.
It is very commonly believed that it is impossible to grow forest trees
on sea-shore bluffs, or points much exposed to strong winds. The
observations just cited tend to show that it would not be difficult to
protect trees from the mechanical effect of the wind, by screens much
lower than the height to which they are expected to grow. Recent
experiments confirm this, and it is found that, though the outer row or
rows may suffer from the wind, every tree shelters a taller one behind
it. Extensive groves have thus been formed in situations where an
isolated tree would not grow at all.
Piper, in his _Trees of America_, p. 19, gives an interesting account of
Mr. Tudor's success in planting trees on the bleak and barren shore of
Nahant. "Mr. Tudor," observes he, "has planted more than ten thousand
trees at Nahant, and, by the results of his experiments, has fully
demonstrated that trees, properly cared for in the beginning, may be
made to grow up to the very bounds of the ocean, exposed to the biting
of the wind and the spray of the sea. The only shelter they require is,
at first, some interruption to break the current of the wind, such as
fences, houses, or other trees."
[423] The careful observations of Colonel J. D. Graham, of the United
States Army, show a tide of about three inches in Lake Michigan. See "A
Lunar Tidal Wave in the North American Lakes," demonstrated by
Lieut.-Colonel J. D. Graham, in the fourteenth volume of the
_Proceedings of the American Association for the Advancement of
Science_.
[424] STARING, _De Bodem van Nederland_, i, p. 327, note.
[425] The principal special works and essays on this subject known to me
are:
BRÉMONTIER, _Mémoire sur les Dunes, etc._, 1790, reprinted in _Annales
des Ponts et Chaussées_, 1833, 1er sémestre, pp. 145-186.
_Rapport sur les differents Mémoires de M. Brémontier_, par LAUMONT et
autres, 1806, same volume, pp. 192, 224.
LEFORT, _Notice sur les Travaux de Fixation des Dunes, Annales des Ponts
et Chaussées_, 1831, 2me sémestre, pp. 320-332.
FORCHHAMMER, _Geognostische Studien am Meeres Ufer_, in LEONHARD und
BRONN, _Jahrbuch, etc._, 1841, pp. 1, 38.
J. G. KOHL, _Die Inseln und Marschen der Herzogthümer Schleswig und
Holstein_, 1846, vol. ii, pp. 112-162, 193-204.
LAVAL, _Mémoire sur les Dunes du Golfe de Gascogne, Annales des Ponts et
Chaussées_, 1847, 2me sémestre, pp. 218-268.
G. C. A. KRAUSE, _Der Dünenbau auf den Ostsee-Küsten West-Preussens_,
1850, 1 vol. 8vo.
W. C. H. STARING, _De Bodem van Nederland_, 1856, vol. i, pp. 310-341,
and 424-431.
Same author, _Voormaals en Thans_, 1858, pages cited.
C. C. ANDRESEN, _Om Klitformationen og Klittens Behandling og
Bestyrelse_, 1861, 1 vol. 8vo, x, 392 pp., much the most complete
treatise on the subject.
ANDRESEN cites, upon the origin of the dunes: HULL, _Over den Oorsprong
en de Geschiedenis der Hollandsche Duinen_, 1838, and GROSS's
_Veiledning ved Behandlingen af Sandflugtstrækningerne_, 1847; and upon
the improvement of sand plains by planting, PANNEWITZ, _Anleitung zum
Anbau der Sandflächen_, 1832. I am not acquainted with either of the
latter two works but I have consulted with advantage, on this subject,
DELAMARRE, _Historique de la Création d'une Richesse millionaire par la
culture des Pins_, 1827; BOITEL, _Mise en valeur des terres pauvres par
le Pin maritime_, 1857; and BRINCKEN, _Ansichten über die Bewaldung der
Steppen des Europäischen Russlands_, 1854.
[426] "Dunes are always full of water, from the action of capillary
attraction. Upon the summits, one seldom needs to dig more than a foot
to find the sand moist, and in the depressions, fresh water is met with
near the surface."--FORCHHAMMER, in LEONHARD und BRONN, for 1841, p. 5,
note.
On the other hand, Andresen, who has very carefully investigated this as
well as all other dune phenomena, maintains that the humidity of the
sand ridges cannot be derived from capillary attraction. He found by
experiment that drift sand was not moistened to a greater height than
eight and a half inches, after standing a whole night in water. He
states the minimum of water contained by the sand of the dunes, one foot
below the surface, after a long drought, at two per cent., the maximum,
after a rainy month, at four per cent. At greater depths the quantity is
larger. The hygroscopicity of the sand of the coast of Jutland he found
to be thirty-three per cent. by measure, or 21.5 by weight. The annual
precipitation on that coast is twenty-seven inches, and, as the
evaporation is about the same, he argues that rain water does not
penetrate far beneath the surface of the dunes, and concludes that their
humidity can be explained only by evaporation from below.--_Om
Klitformationen_, pp. 106-110.
In the dunes of Algeria, water is so abundant that wells are constantly
dug in them at high points on their surface. They are sunk to the depth
of three or four mètres only, and the water rises to the height of a
mètre in them.--LAURENT, _Mémoire sur le Sahara_, pp. 11, 12, 13.
The same writer observes (p. 14) that the hollows in the dunes are
planted with palms which find moisture enough a little below the
surface. It would hence seem that the proposal to fix the dunes which
are supposed to threaten the Suez Canal, by planting the maritime pine
and other trees upon them, is not altogether so absurd as it is thought
to be by some of those disinterested philanthropists of other nations
who are distressed with fears that French capitalists will lose the
money they have invested in that great undertaking.
Ponds of water are often found in the depressions between the sand hills
of the dune chains in the North American desert.
[427] According to the French authorities, the dunes of France are not
always composed of quartzose sand. "The dune sands" of different
characters, says Brémontier, "partake of the nature of the different
materials which compose them. At certain points on the coast of Normandy
they are found to be purely calcareous; they are of mixed composition on
the shores of Brittany and Saintonge, and generally quartzose between
the mouth of the Gironde and that of the Adour."--_Mémoire sur les
Dunes, Annales des Ponts et Chaussées_, t. vii, 1833, 1er sémestre, p.
146.
In the dunes of Long Island and of Jutland, there are considerable veins
composed almost wholly of garnet. For a very full examination of the
mechanical and chemical composition of the dune sands of Jutland, see
ANDRESEN, _Om Klitformationen_, p. 110.
[428] _De Bodem van Nederland_, i, p. 323.
[429] J. G. KOHL, _Die Inseln und Marschen der Herzogthümer Schleswig
und Holstein_, ii, p. 200.
[430] STARING, _De Bodem van Nederland_, i, p. 317. See also, BERGSÖE,
_Reventov's Virksomhed_, ii, p. 11.
"In the sand-hill ponds mentioned in the text, there is a vigorous
growth of bog plants accompanied with the formation of peat, which goes
on regularly as long as the dune sand does not drift. But if the surface
of the dunes is broken, the sand blows into the ponds, covers the peat,
and puts an end to its formation. When, in the course of time, marine
currents cut away the coast, the dunes move landward and fill up the
ponds, and thus are formed the remarkable strata of fossile peat called
Martörv, which appears to be unknown to the geologists of other parts of
Europe."--FORCHHAMMER, in LEONHARD und BRONN, 1841, p. 13.
[431] The lower strata must be older than the superficial layers, and
the particles which compose them may in time become more disintegrated,
and therefore finer than those deposited later and above them.
[432] "On the west coast of Africa the dunes are drifting seawards, and
always receiving new accessions from the Sahara. They are constantly
advancing out into the sea." See _ante_, p. 16, note.--NAUMANN,
_Geognosie_, ii, p. 1172. See _Appendix_, No. 58.
[433] Forchhammer, after pointing out the coincidence between the
inclined stratification of dunes and the structure of ancient tilted
rocks, says: "But I am not able to point out a sandstone formation
corresponding to the dunes. Probably most ancient dunes have been
destroyed by submersion before the loose sand became cemented to solid
stone, but we may suppose that circumstances have existed somewhere
which have preserved the characteristics of this formation."--LEONHARD
und BRONN, 1841, p. 8, 9.
Such formations, however, certainly exist. I find from Laurent (_Mémoire
sur le Sahara, etc._, p. 12), that in the Algerian desert there exist
"sandstone formations" not only "corresponding to the dunes," but
actually consolidated within them. "A place called El-Mouia-Tadjer
presents a repetition of what we saw at El-Baya; one of the funnels
formed in the middle of the dunes contains wells from two mètres to two
and a half in depth, dug in a sand which pressure, and probably the
presence of certain salts, have cemented so as to form true sandstone,
soft indeed, but which does not yield except to the pickaxe. These
sandstones exhibit an inclination which seems to be the effect of wind;
for they conform to the direction of the sands which roll down a scarp
occasioned by the primitive obstacle." See _Appendix_, No. 59.
The dunes near the mouth of the Nile, the lower sands of which have been
cemented together by the infiltration of Nile water, would probably show
a similar stratification in the sandstone which now forms their base.
[434] Forchhammer ascribes the resemblance between the furrowing of the
dune sands and the beach ripples, not to the similarity of the effect of
wind and water upon sand, but wholly to the action of the former fluid;
in the first instance, directly, in the latter, through the water. "The
wind ripples on the surface of the dunes precisely resemble the water
ripples of sand flats occasionally overflowed by the sea; and with the
closest scrutiny, I have never been able to detect the slightest
difference between them. This is easily explained by the fact, that the
water ripples are produced by the action of light wind on the water
which only transmits the air waves to the sand."--LEONHARD und BRONN,
1841, pp. 7, 8.
[435] American observers do not agree in their descriptions of the form
and character of the sand grains which compose the interior dunes of the
North American desert. C. C. Parry, geologist to the Mexican Boundary
Commission, in describing the dunes near the station at a spring
thirty-two miles west from the Rio Grande at El Paso, says: "The
separate grains of the sand composing the sand hills are seen under a
lens to be angular, and not rounded, as would be the case in regular
beach deposits."--_U. S. Mexican Boundary Survey, Report of_, vol. i,
_Geological Report of C. C. Parry_, p. 10.
In the general description of the country traversed, same volume, p. 47,
Colonel Emory says that on an "examination of the sand with a microscope
of sufficient power," the grains are seen to be angular, not rounded by
rolling in water.
On the other hand, Blake, in _Geological Report, Pacific Railroad Rep._,
vol. v, p. 119, observes that the grains of the dune sand, consisting of
quartz, chalcedony, carnelian, agate, rose quartz, and probably
chrysolite, were much rounded; and on page 241, he says that many of the
sand grains of the Colorado desert are perfect spheres.
On page 20 of a report in vol. ii of the _Pacific Railroad Report_, by
the same observer, it is said that an examination of dune sands brought
from the Llano Estacado by Captain Pope, showed the grains to be "much
rounded by attrition."
The sands described by Mr. Parry and Colonel Emory are not from the same
localities as those examined by Mr. Blake, and the difference in their
character may denote a difference of origin or of age.
[436] LAURENT (_Mémoire sur le Sahara_, pp. 11, 12, and elsewhere)
speaks of a funnel-shaped depression at a high point in the dunes, as a
characteristic feature of the sand hills of the Algerian desert. This
seems to be an approximation to the crescent form noticed by Meyen and
Pöppig in the inland dunes of Peru.
[437] _Travels in Peru_, New York, 1848, chap. ix.
[438] Notwithstanding the general tendency of isolated coast dunes and
of the peaks of the sand ridges to assume a conical form, Andresen
states that the hills of the inner or landward rows are sometimes
_bow-shaped_, and sometimes undulating in outline.--_Om
Klitformationen_, p. 84. He says further that: "Before an obstruction,
two or three feet high and considerably longer, lying perpendicularly to
the direction of the wind, the sand is deposited with a windward angle
of from 6° to 12°, and the bank presents a concave face to the wind,
while, behind the obstruction, the outline is convex;" and he lays it
down as a general rule, that a slope, _from_ which sand is blown, is
left with a concavity of about one inch of depth to four feet of
distance; a slope, _upon_ which sand is dropped by the wind, is convex.
It appears from Andresen's figures, however, that the concavity and
convexity referred to, apply, not to the _horizontal longitudinal_
section of the sand bank, as his language unexplained by the drawings
might be supposed to mean, but to the _vertical cross-section_, and
hence the dunes he describes, with the exception above noted, do not
correspond to those of the American deserts.--_Om Klitformationen_, p.
86.
The dunes of Gascony, which sometimes exceed three hundred feet in
height, present the same concavity and convexity of _vertical_
cross-section. The slopes of these dunes are much steeper than those of
the Netherlands and the Danish coast; for while all observers agree in
assigning to the seaward and landward faces of those latter,
respectively, angles of from 5° to 12°, and 30° with the horizon, the
corresponding faces of the dunes of Gascony present angles of from 10°
to 25°, and 50° to 60°.--LAVAL, _Mémoire sur les Dunes de Gascogne,
Annales des Ponts et Chaussées_, 1847, 2me sémestre.
[439] Krause, speaking of the dunes on the coast of Prussia, says:
"Their origin belongs to three different periods, in which important
changes in the relative level of sea and land have unquestionably taken
place. * * * Except in the deep depressions between them, the dunes are
everywhere sprinkled, to a considerable height, with brown oxydulated
iron, which has penetrated into the sand to the depth of from three to
eighteen inches, and colored it red. * * * Above the iron is a stratum
of sand differing in composition from ordinary sea sand, and on this,
growing woods are always found. * * * The gradually accumulated forest
soil occurs in beds of from one to three feet thick, and changes,
proceeding upward, from gray sand to black humus." Even on the third or
seaward range, the sand grasses appear and thrive luxuriantly, at least
on the west coast, though. Krause doubts whether the dunes of the east
coast were ever thus protected.--_Der Dünenbau_, pp. 8, 11.
[440] LAVAL, _Mémoire sur les Dunes de Gascogne, Annales des Ponts et
Chaussées_, 1847, 2me sémestre, p. 231. The same opinion had been
expressed by BRÉMONTIER, _Annales des Ponts et Chaussées_, 1833, 1er
sémestre, p. 185.
[441] "In the Middle Ages," says Willibald Alexis, as quoted by Müller,
_Das Buch der Pflanzenwelt_ i, p. 16, "the Nehrung was extending itself
further, and the narrow opening near Lochstadt had filled itself up with
sand. A great pine forest bound with its roots the dune sand and the
heath uninterruptedly from Danzig to Pillau. King Frederick William I
was once in want of money. A certain Herr von Korff promised to procure
it for him, without loan or taxes, if he could be allowed to remove
something quite useless. He thinned out the forests of Prussia, which
then, indeed, possessed little pecuniary value; but he felled the entire
woods of the Frische Nehrung, so far as they lay within the Prussian
territory. The financial operation was a success. The king had money,
but in the elementary operation which resulted from it, the state
received irreparable injury. The sea winds rush over the bared hills;
the Frische Haff is half-choked with sand; the channel between Elbing,
the sea, and Königsberg is endangered, and the fisheries in the Haff
injured. The operation of Herr von Korff brought the king 200,000
thalers. The state would now willingly expend millions to restore the
forests again."
[442] STARING, _Voormaals en Thans_, p. 231. Had the dunes of the
Netherlandish and French coasts, at the period of the Roman invasion,
resembled the moving sand hills of the present day, it is inconceivable
that they could have escaped the notice of so acute a physical
geographer as Strabo; and the absolute silence of Cæsar, Ptolemy, and
the encyclopædic Pliny, respecting them, would be not less inexplicable.
The Old Northern language, the ancient tongue of Denmark, though rich in
terms descriptive of natural scenery, had no name for dune, nor do I
think the sand hills of the coast are anywhere noticed in Icelandic
literature. The modern Icelanders, in treating of the dunes of Jutland,
call them _klettr_, hill, cliff, and the Danish _klit_ is from that
source. The word Düne is also of recent introduction into German. Had
the dunes been distinguished from other hillocks, in ancient times, by
so remarkable a feature as the propensity to drift, they would certainly
have acquired a specific name in both Old Northern and German. So long
as they were wooded knolls, they needed no peculiar name; when they
became formidable, from the destruction of the woods which confined
them, they acquired a designation.
[443] The sands of Cape Cod were partially, if not completely, covered
with vegetation by nature. Dr. Dwight, describing the dunes as they were
in 1800, says: "Some of them are covered with beach grass; some fringed
with whortleberry bushes; and some tufted with a small and singular
growth of oaks. * * * The parts of this barrier, which are covered with
whortleberry bushes and with oaks, have been either not at all, or very
little blown. The oaks, particularly, appear to be the continuation of
the forests originally formed on this spot. * * * They wore all the
marks of extreme age; were, in some instances, already decayed, and in
others decaying; were hoary with moss, and were deformed by branches,
broken and wasted, not by violence, but by time."--_Travels_, iii, p.
91.
[444] Bergsöe (_Reventlovs Virksomhed_, ii, 3) states that the dunes on
the west coast of Jutland were stationary before the destruction of the
forests to the east of them. The felling of the tall trees removed the
resistance to the lower currents of the westerly winds, and the sands
have since buried a great extent of fertile soil. See also same work,
ii, p. 124.
[445] "We must, therefore, not be surprised to see the people here deal
as gingerly with their dunes, as if treading among eggs. He who is lucky
enough to own a molehill of dune pets it affectionately, and spends his
substance in cherishing and fattening it. That fair, fertile, rich
province, the peninsula of Eiderstädt in the south of Friesland, has, on
the point toward the sea, only a tiny row of dunes, some six miles long
or so; but the people talk of their fringe of sand hills as if it were a
border set with pearls. They look upon it as their best defence against
Neptune. They have connected it with their system of dikes, and for
years have kept sentries posted to protect it against wanton
injury."--J. G. KOHL, _Die Inseln u. Marschen Schleswig-Holsteins_, ii,
p. 115.
[446] Sand banks sometimes connect themselves with the coast at both
ends, and thus cut off a portion of the sea. In this case, as well as
when salt water is enclosed by sea dikes, the water thus separated from
the ocean gradually becomes fresh, or at least brackish. The Haffs, or
large expanses of fresh water in Eastern Prussia--which are divided from
the Baltic by narrow sand banks called Nehrungen, or, at sheltered
points of the coast, by fluviatile deposits called Werders--all have one
or more open passages, through which the water of the rivers that supply
them at last finds its way to the sea.
[447] ANDRESEN, _Om Klitformationen_, pp. 68-72.
[448] Id., pp. 231, 232. Andresen's work, though printed in 1861, was
finished in 1859. Lyell (_Antiquity of Man_, 1863, p. 14) says: "Even in
the course of the present century, the salt waters have made one
eruption into the Baltic by the Liimfjord, although they have been now
again excluded."
[449] FORCHHAMMER, _Geognostische Studien am Meeres-Ufer_. LEONHARD und
BRONN, _Jahrbuch_, 1841, pp. 11, 13.
[450] ANDRESEN, _Om Klitformationen_, pp. 68, 72.
[451] _Voormaals en Thans_, pp. 126, 170.
[452] See a very interesting article entitled "Le Littoral de la
France," by ÉLISÉE RECLUS, in the _Revue des Deux Mondes_, for December,
1862, pp. 901, 936.
[453] _De Bodem van Nederland_, i, p. 425. See _Appendix_, No. 60.
[454] The movement of the dunes has been hardly less destructive on the
north side of the Gironde. Sea the valuable article of ÉLISÉE RECLUS
already referred to, in the _Revue des Deux Mondes_, for December, 1862,
entitled "Le Littoral de la France."
[455] LAVAL, _Mémoire sur les Dunes du Golfe de Gascogne, Annales des
Ponts et Chaussées_, 1847, p. 223. The author adds, as a curious and
unexplained fact, that some of these pools, though evidently not
original formations but mere accumulations of water dammed up by the
dunes, have, along their western shore, near the base of the sand hills,
a depth of more than one hundred and thirty feet, and hence their
bottoms are not less than eighty feet below the level of the lowest
tides. Their western banks descend steeply, conforming nearly to the
slope of the dunes, while on the northeast and south the inclination of
their beds is very gradual. The greatest depth of these pools
corresponds to that of the sea ten miles from the shore. Is it possible
that the weight of the sands has pressed together the soil on which they
rest, and thus occasioned a subsidence of the surface extending beyond
their base? See _Appendix_, No. 61.
[456] ANDRESEN, _Om Klitformationem_, pp. 56, 79, 82.
[457] STARING, _De Bodem van Nederland_, i, pp. 329-331. Id., _Voormaals
en Thans_, p. 163. ANDRESEN, _Om Klitformationen_, pp. 280, 295.
The creation of new dunes, by the processes mentioned in the text, seems
to be much older in Europe than the adoption of measures for securing
them by planting. Dr. Dwight mentions a case in Massachusetts, where a
beach was restored, and new dunes formed, by planting beach grass.
"Within the memory of my informant, the sea broke over the beach which
connects Truro with Province Town, and swept the body of it away for
some distance. The beach grass was immediately planted on the spot; in
consequence of which the beach was again raised to a sufficient height,
and in various places into hills."--_Dwight's Travels_, iii, p. 93.
[458] STARING, i, pp. 310, 332.
[459] There is some confusion in the popular use of these names, and in
the scientific designations of sand plants, and they are possibly
applied to different plants in different places. Some writers style the
gourbet _Calamagrostis arenaria_, and distinguish it from the Danish
Klittetag or Hjelme.
[460] Bread, not indeed very palatable, has been made of the seeds of
the arundo, but the quantity which can be gathered is not sufficient to
form an important economical resource.----ANDRESEN, _Om
Klitformationen_, p. 160.
[461] BERGSÖE, _Reventlovs Virksomhed_, ii, p. 4.
[462] Measures were taken for the protection of the dunes of Cape Cod,
in Massachusetts, during the colonial period, though I believe they are
now substantially abandoned. A hundred years ago, before the valley of
the Mississippi, or even the rich plains of Central and Western New
York, were opened to the white settler, the value of land was relatively
much greater in New England than it is at present, and consequently some
rural improvements were then worth making, which would not now yield
sufficient returns to tempt the investment of capital. The money and the
time required to subdue and render productive twenty acres of sea sand
on Cape Cod, would buy a "section" and rear a family in Illinois. The
son of the Pilgrims, therefore, abandons the sand hills, and seeks a
better fortune on the fertile prairies of the West.
Dr. Dwight, who visited Cape Cod in the year 1800, after describing the
"beach grass, a vegetable bearing a general resemblance to sedge, but of
a light bluish-green, and of a coarse appearance," which "flourishes
with a strong and rapid vegetation on the sands," observes that he
received "from a Mr. Collins, formerly of Truro, the following
information:" "When he lived at Truro, the inhabitants were, under the
authority of law, regularly warned in the month of April, yearly, to
plant beach grass, as, in other towns of New England, they are warned to
repair highways. It was required by the laws of the State, and under the
proper penalties for disobedience; being as regular a public tax as any
other. The people, therefore, generally attended and performed the
labor. The grass was dug in bunches, as it naturally grows; and each
bunch divided into a number of smaller ones. These were set out in the
sand at distances of three feet. After one row was set, others were
placed behind it in such a manner as to shut up the interstices; or, as
a carpenter would say, so as to break the joints. * * * When it is once
set, it grows and spreads with rapidity. * * * The seeds are so heavy
that they bend down the heads of the grass; and when ripe, drop directly
down by its side, where they immediately vegetate. Thus in a short time
the ground is covered.
"Where this covering is found, none of the sand is blown. On the
contrary, it is accumulated and raised continually as snow gathers and
rises among bushes, or branches of trees cut and spread upon the earth.
Nor does the grass merely defend the surface on which it is planted; but
rises, as that rises by new accumulations; and always overtops the sand,
however high that may be raised by the wind."--_Dwight's Travels in New
England and New York_, ii, p. 92, 93.
This information was received in 1800, and it relates to a former state
of things, probably more than twenty years previous, and earlier than
1779, when the Government of Denmark first seriously attempted the
conquest of the dunes.
The depasturing of the beach grass--a plant allied in habits, if not in
botanical character, to the arundo--has been attended with very
injurious effects in Massachusetts. Dr. Dwight, after referring to the
laws for its propagation, already cited, says: "The benefit of this
useful plant, and of these prudent regulations, is, however, in some
measure lost. There are in Province Town, as I was informed, one hundred
and forty cows. These animals, being stinted in their means of
subsistence, are permitted to wander, at times, in search of food. In
every such case, they make depredations on the beach grass, and prevent
its seeds from being formed. In this manner the plant is ultimately
destroyed."--_Travels_, iii, p. 94.
On page 101 of the same volume, the author mentions an instance of great
injury from this cause. "Here, about one thousand acres were entirely
blown away to the depth, in many places, of ten feet. * * * Not a green
thing was visible except the whortleberries, which tufted a few lonely
hillocks rising to the height of the original surface and prevented by
this defence from being blown away also. These, although they varied the
prospect, added to the gloom by their strongly picturesque appearance,
by marking exactly the original level of the plain, and by showing us in
this manner the immensity of the mass which had been thus carried away
by the wind. The beach grass had been planted here, and the ground had
been formerly enclosed; but the gates had been left open, and the cattle
had destroyed this invaluable plant."
[463] ANDRESEN, _Om Klitformationen_, pp. 237, 240.
[464] "These plantations, perseveringly continued from the time of
Brémontier now cover more than 40,000 hectares, and compose forests
which are not only the salvation of the department, but constitute its
wealth."--CLAVÉ, _Études Forestières_, p. 254.
Other authors have stated the plantations of the French dunes to be much
more extensive.
[465] KRUSE, _Dünenbau_, pp. 34, 38, 40.
[466] These processes are substantially similar to those employed in the
pineries of the Carolinas, but they are better systematized and more
economically conducted in France. In the latter country, all the
products of the pine, even to the cones, find a remunerating market,
while, in America, the price of resin is so low, that in the fierce
steamboat races on the great rivers, large quantities of it are thrown
into the furnaces to increase the intensity of the fires. In a carefully
prepared article on the Southern pineries published in an American
magazine--I think Harper's--a few years ago, it was stated that the
resin from the turpentine distilleries was sometimes allowed to run to
waste; and the writer, in one instance, observed a mass, thus rejected
as rubbish, which was estimated to amount to two thousand barrels. See
_Appendix_, No. 62.
[467] ANDRESEN, _Om Klitformationen_, pp. 78, 262, 275.
[468] LAVAL, _Mémoire sur les Dunes du Golfe de Gascogne, Annales des
Ponts et Chaussées_, 1847, 2me sémestre, p. 261. See _Appendix_, No.
63.
[469] There are extensive ranges of dunes on various parts of the coasts
of the British Islands, but I find no estimate of their area. Pannewitz
(_Anleitung zam Anbau der Sandflächen_), as cited by Andresen (_Om
Klitformationen_, p. 45), states that the drifting sands of Europe,
including, of course, sand plains as well as dunes, cover an extent of
21,000 square miles. This is, perhaps, an exaggeration, though there is,
undoubtedly, much more desert land of this description on the European
continent than has been generally supposed. There is no question that
most of this waste is capable of reclamation by simple planting, and no
mode of physical improvement is better worth the attention of civilized
Governments than this.
There are often serious objections to extensive forest planting on soils
capable of being otherwise made productive, but they do not apply to
sand wastes, which, until covered by woods, are not only a useless
incumbrance, but a source of serious danger to all human improvements in
the neighborhood of them.
[470] BOITEL, _Mise en valeur des Terres pauvres par le Pin maritime_,
pp. 212, 218.
[471] See _Appendix_, No. .
[472] For details, consult ANDRESEN, _Om Klitformationen_, pp. 223, 236.
[473] When the deposit is not very deep, and the adjacent land lying to
the leeward of the prevailing winds is covered with water, or otherwise
worthless, the surface is sometimes freed from the drifts by repeated
harrowings, which loosen the sand, so that the wind takes it up and
transports it to grounds where accumulations of it are less injurious.
[474] _Travels and Researches in Chaldæa_, chap. ix.
[475] _Études Forestières_, p. 253.
[476] LAVERGNE, _Économie Rurale de la France_, p. 300, estimates the
area of the Landes of Gascony at 700,000 hectares, or about 1,700,000
acres. The same author states (p. 304), that when the Moors were driven
from Spain by the blind cupidity and brutal intolerance of the age, they
demanded permission to establish themselves in this desert; but
political and religious prejudices prevented the granting of this
liberty. At this period the Moors were a far more cultivated people than
their Christian persecutors, and they had carried many arts, that of
agriculture especially, to a higher pitch than any other European
nation. But France was not wise enough to accept what Spain had cast
out, and the Landes remained a waste for three centuries longer. See
_Appendix_, No. 64.
The forest of Fontainebleau, which contains above 40,000 acres, is not a
plain, but its soil is composed almost wholly of sand, interspersed with
ledges of rock. The sand forms not less than ninety-eight per cent. of
the earth, and, as it is almost without water, it would be a drifting
desert but for the artificial propagation of forest trees upon it.
[477] _Économie Rurale de la Belgique, par_ EMILE DE LAVELEYE, _Revue
des Deux Mondes_, Juin, 1861, pp. 617-644.
[478] _Geognosie_, ii, p. 1173.
[479] According to HOHENSTEIN, _Der Wald_, pp. 228, 229, an extensive
plantation of pines--a tree new to Southern Russia--was commenced in
1842, on the barren and sandy banks of the Ingula, near Elisabethgrod,
and has met with very flattering success. Other experiments in
sylviculture at different points on the steppes promise valuable
results.
[480] "Sixteen years ago," says an Odessa landholder, "I attempted to
fix the sand of the steppes, which covers the rocky ground to the depth
of a foot, and forms moving hillocks with every change of wind. I tried
acacias and pines in vain; nothing would grow in such a soil. At length
I planted the varnish tree, or _ailanthus_, which succeeded completely
in binding the sand." This result encouraged the proprietor to extend
his plantations over both dunes and sand steppes, and in the course of
sixteen years this rapidly growing tree had formed real forests. Other
landowners have imitated his example with great advantage.--RENTSCH,
_Der Wald_, p. 44, 45.
[481] _Souvenirs d'un Naturaliste_, i, pp. 204 _et seqq._
[482] "If we suppose the narrow isthmus of Central America to be sunk in
the ocean, the warm equatorial current would no longer follow its
circuitous route around the Gulf of Mexico, but pour itself through the
new opening directly into the Pacific. We should then lose the warmth of
the Gulf Stream, and cold polar currents flowing farther southward would
take its place and be driven upon our coasts by the western winds. The
North Sea would resemble Hudson's Bay, and its harbors be free from ice
at best only in summer. The power and prosperity of its coasts would
shrivel under the breath of winter, as a medusa thrown on shore shrinks
to an insignificant film under the influence of the destructive
atmosphere. Commerce, industry, fertility of soil, population, would
disappear, and the vast waste--a new Labrador--would become a worthless
appendage of some clime more favored by nature."--HARTWIG, _Das Leben
des Meeres_, p. 70.
[483] I know nothing of Captain Allen's work but its title and its
subject. Very probably he may have anticipated many of the following
speculations, and thrown light on points upon which I am ignorant.
[484] "Some haue writt[=e], that by certain kings inhabiting aboue, the
_Nilus_ should there be stopped; & at a time prefixt, let loose vpon a
certaine tribute payd them by the _Aegyptians_. The error springing
perhaps fr[=o] a truth (as all wandring reports for the most part doe)
in that the _Sultan_ doth pay a certaine annuall summe to the _Abissin_
Emperour for not diuerting the course of the Riuer, which (they say) he
may, or impouerish it at the least."--GEORGE SANDYS, _A Relation of a
Journey, etc._, p. 98.
[485] The Recca, a river with a considerable current, has been
satisfactorily identified with a stream flowing through the cave of
Trebich, and with the Timavo--the Timavus of Virgil and the ancient
geographers--which empties through several mouths into the Adriatic
between Trieste and Aquileia. The distance from Trieste to a suitable
point in the grotto of Trebich is thought to be less than three miles,
and the difficulties in the way of constructing a tunnel do not seem
formidable. The works of Schmidl, _Die Höhlen des Karstes_, and _Der
unterirdische Lauf der Recca_, are not common out of Germany, but the
reader will find many interesting facts derived from them in two
articles entitled _Der unterirdische Lauf der Recca_, in _Aus der
Natur_, xx, pp. 250-254, 263-266.
[486] BARTH, _Wanderungen durch die Küsten des Mittelmeeres_, i, p. 353.
In a note on page 380, of the same volume, Barth cites Strabo as
asserting that a similar practice prevailed in Iapygia; but it may be
questioned whether the epithet [Greek: tracheia], applied by Strabo to
the original surface, necessarily implies that it was covered with a
continuous stratum of rock.
[487] PARTHEY, _Wanderungen durch Sicilien und die Levante_, i, p. 404.
[488] _Geognostische Studien am Meeres Ufer_, LEONHARD und BRONN,
_Jahrbuch_, 1841, pp. 25, 26.
[489] KOHL, _Schleswig-Holstein_, ii, p. 45.
[490] _Wanderungen durch Sicilien und die Levante_, i, p. 406.
[491] LANDGREBE, _Naturgeschichte der Vulkane_, ii, pp. 19, 20.
[492] Soon after the current issues from the volcano, it is covered
above and at its sides, and finally in front, with scoriæ, formed by the
cooling of the exposed surface, which bury and conceal the fluid mass.
The stream rolls on under the coating, and between the walls of scoriæ,
and it was the lateral crust which was broken through by the workmen
mentioned in the text.
The distance to which lava flows, before its surface begins to solidify,
depends on its volume, its composition, its temperature and that of the
air, the force with which it is ejected, and the inclination of the
declivity over which it runs. In most cases it is difficult to approach
the current at points where it is still entirely fluid, and hence
opportunities of observing it in that condition are not very frequent.
In the eruption of February, 1850, on the east side of Vesuvius, I went
quite up to one of the outlets. The lava shot out of the orifice upward
with great velocity, like the water from a spring, in a stream eight or
ten feet in diameter, throwing up occasionally volcanic bombs, but it
immediately spread out on the declivity down which it flowed, to the
width of several yards. It continued red hot in broad daylight, and
without a particle of scoriæ on its surface, for a course of at least
one hundred yards. At this distance, the suffocating, sulphurous vapors
became so dense that I could follow the current no farther. The
undulations of the surface were like those of a brook swollen by rain. I
estimated the height of the waves at five or six inches by a breadth of
eighteen or twenty. To the eye, the fluidity of the lava seemed as
perfect as that of water, but masses of cold lava weighing ten or
fifteen pounds floated upon it like cork.
The heat emitted by lava currents seems extremely small when we consider
the temperature required to fuse such materials and the great length of
time they take in cooling. I saw at Nicolosi ancient oil jars, holding a
hundred gallons or more, which had been dug out from under a stream of
old lava above that town. They had been very slightly covered with
volcanic ashes before the lava flowed over them, but the lead with which
holes in them had been plugged was not melted. The current that buried
Mompiliere in 1669 was thirty-five feet thick, but marble statues, in a
church over which the lava formed an arch, were found uncalcined and
uninjured in 1704. See SCROPE, _Volcanoes_, chap. VI. § 6.
[493] FERRARA, _Descrizione dell' Etna_, p. 108.
[494] LANGREBE, _Naturgeschichte der Vulkane_, ii, p. 82.
[495] _Physikalische Geographie_, p. 168. Beds of peat, accidentally set
on fire, sometimes continue to burn for months. I take the following
account of a case of this sort from a recent American journal:
"A CURIOUS PHENOMENON.--When the track of the railroad between Brunswick
and Bath was being graded, in crossing a meadow near the populous
portion of the latter city, the 'dump' suddenly took on a sinking
symptom, and down went the twenty feet fill of gravel, clay, and broken
rocks, out of sight, and it was a long, _long_ time before dirt trains
could fill the capacious stomach that seemed ready to receive all the
solid material that could be turned into it. The difficulty was at
length overcome, but all along the side of the sinkage the earth was
thrown up, broken into yawning chasms, and the surface was thus elevated
above its old watery level. Since that time this ground, thus slightly
elevated, has been cultivated, and has yielded enormously of whatever
the owner seemed disposed to plant upon it. Some three months ago, by
some means unknown to us, the underlying peat took fire, and for weeks,
as we had occasion to pass it, we noticed the smoke arising from the
smouldering combustion beneath the surface. Rains fell, but the fire
burned, and the smoke continued to arise. Monday we had occasion to pass
the spot, and though nearly a week's rain had been drenching the ground,
and though the surface was whitened with snow, and though pools of water
were standing upon the surface in the immediate neighborhood, still the
everlasting subterranean fire was burning, and the smoke arising through
the snow."
[496] One of the sublimest, and at the same time most fearful
suggestions that have been prompted by the researches of modern science,
was made by Babbage in the ninth chapter of his _Ninth Bridgewater
Treatise_. I have not the volume at hand, but the following explanation
will recall to the reader, if it does not otherwise make intelligible,
the suggestion I refer to.
No atom can be disturbed in place, or undergo any change of temperature,
of electrical state, or other material condition, without affecting, by
attraction or repulsion or other communication, the surrounding atoms.
These, again, by the same law, transmit the influence to other atoms,
and the impulse thus given extends through the whole material universe.
Every human movement, every organic act, every volition, passion, or
emotion, every intellectual process, is accompanied with atomic
disturbance, and hence every such movement, every such act or process
affects all the atoms of universal matter. Though action and reaction
are equal, yet reaction does not restore disturbed atoms to their former
place and condition, and consequently the effects of the least material
change are never cancelled, but in some way perpetuated, so that no
action can take place in physical, moral, or intellectual nature,
without leaving all matter in a different state from what it would have
been if such action had not occurred. Hence, to use language which I
have employed on another occasion: there exists, not alone in the human
conscience or in the omniscience of the Creator, but in external
material nature, an ineffaceable, imperishable record, possibly legible
even to created intelligence, of every act done, every word uttered,
nay, of every wish and purpose and thought conceived by mortal man, from
the birth of our first parent to the final extinction of our race; so
that the physical traces of our most secret sins shall last until time
shall be merged in that eternity of which not science, but religion
alone, assumes to take cognizance.
APPENDIX.
No. 1 (page 19, _note_). It may be said that the cases referred to in
the note on p. 19--and indeed all cases of a supposed acclimation
consisting in physiological changes--are instances of the origination of
new varieties by natural selection, the hardier maize, tomato, and other
vegetables of the North, being the progeny of seeds of individuals
endowed, exceptionally, with greater power of resisting cold than
belongs in general to the species which produced them. But, so far as
the evidence of change of climate, from a difference in vegetable
growth, is concerned, it is immaterial whether we adopt this view or
maintain the older and more familiar doctrine of a local modification of
character in the plants in question.
No. 2 (page 24, _note_). The adjectives of direction in _-erly_ are not
unfrequently used to indicate, in a loose way, the course of winds
blowing from unspecified points between N.E. and S.E.; S.E. and S.W.;
S.W. and N.W. or N.W. and N.E. If the employment of these words were
understood to be limited to thus expressing a direction nearer to the
cardinal point from whose name the adjective is taken than to any other
cardinal point, they would be valuable elements of English
meteorological nomenclature.
No. 3 (page 31). I find a confirmation of my observations on the habits
of the beaver as a geographical agency, in a report of the proceedings
of the British Association, in the London Athenæum of October 8, 1864,
p. 469. It is there stated that Viscount Milton and Dr. Cheadle, in an
expedition across the Rocky Mountains by the Yellow Head, or Leather
Pass, observed that "a great portion of the country to the east of the
mountains" had been "completely changed in character by the agency of
the beaver, which formerly existed here in enormous numbers. The shallow
valleys were formerly traversed by rivers and chains of lakes which,
dammed up along their course at numerous points, by the work of those
animals, have become a series of marshes in various stages of
consolidation. So complete has this change been, that hardly a stream is
found for a distance of two hundred miles, with the exception of the
large rivers. The animals have thus destroyed, by their own labors, the
waters necessary to their own existence."
When the process of "consolidation" shall have been completed, and the
forest reëstablished upon the marshes, the water now diffused through
them will be collected in the lower or more yielding portions, cut new
channels for their flow, become running brooks, and thus restore the
ancient aspect of the surface.
No. 4 (page 33, _note_). The lignivorous insects that attack living
trees almost uniformly confine their ravages to trees already unsound or
diseased in growth from the depredations of leaf-eaters, such as
caterpillars and the like, or from other causes. The decay of the tree,
therefore, is the cause not the consequence of the invasions of the
borer. This subject has been discussed by Perris in the _Annales de la
Société Entomologique de la France_, for 1851 (?), and his conclusions
are confirmed by the observations of Samanos, who quotes, at some
length, the views of Perris. "Having, for fifteen years," says the
latter author, "incessantly studied the habits of lignivorous insects in
one of the best wooded regions of France, I have observed facts enough
to feel myself warranted in expressing my conclusions, which are: that
insects in general--I am not speaking of those which confine their
voracity to the leaf--do not attack trees in sound health, and they
assail those only whose normal conditions and functions have been by
some cause impaired."
See, more fully, Samanos, _Traité de la Culture du Pin Maritime_, Paris,
1864, pp. 140-145.
No. 5 (page 34, _note_). Very interesting observations, on the agency of
the squirrel and other small animals in planting and in destroying nuts
and other seeds of trees, may be found in a paper on the Succession of
Forests in Thoreau's _Excursions_, pp. 135 _et seqq._
I once saw several quarts of beech-nuts taken from the winter quarters
of a family of flying squirrels in a hollow tree. The kernels were
neatly stripped of their shells and carefully stored in a dry cavity.
No. 6 (page 40, _note_). Schroeder van der Kolk, in _Het Verschil
tusschen den Psychischen Aanleg van het Dier en van den Mensch_, cites
from Burdach and other authorities many interesting facts respecting
instincts lost, or newly developed and become hereditary, in the lower
animals, and he quotes Aristotle and Pliny as evidence that the common
quadrupeds and fowls of our fields and our poultry yards were much less
perfectly domesticated in their times than long, long ages of servitude
have now made them.
Perhaps the half-wild character ascribed by P. Læstadius and other
Swedish writers to the reindeer of Lapland, may be in some degree due to
the comparative shortness of the period during which he has been
partially tamed. The domestic swine bred in the woods of Hungary and
the buffaloes of Southern Italy are so wild and savage as to be very
dangerous to all but their keepers. The former have relapsed into their
original condition, the latter have not yet been reclaimed from it.
Among other instances of obliterated instincts, Schroeder van der Kolk
states that in Holland, where, for centuries, the young of the cow has
been usually taken from the dam at birth and fed by hand, calves, even
if left with the mother, make no attempt to suck; while in England,
where calves are not weaned until several weeks old, they resort to the
udder as naturally as the young of wild quadrupeds.--_Ziel en Ligchaam_,
p. 128, _n._
No. 7 (page 60, _first note_). At Piè di Mulera, at the outlet of the
Val Anzasca, near the principal hotel, is a vine measuring thirty-one
inches in circumference. The door of the chapter-hall in the cloister of
the church of San Giovanni, at Saluzzo, is of vine wood, and the boards
of which the panels were made could not have been less than ten inches
wide. Statues and other objects of considerable dimensions, of vine
wood, are mentioned by ancient writers.
No. 8 (page 63, _second note_). Cartier, A. D. 1535-'6, mentions "vines,
great melons, cucumbers, gourds [courges], pease, beans of various
colors, but not like ours," as common among the Indians of the banks of
the St. Lawrence.--_Bref Recit_, etc., reprint. Paris, 1863, pp. 13, a;
14, b; 20, b; 31, a.
No. 8 (page 65, _second paragraph_). It may be considered very highly
probable, if not certain, that the undiscriminating herbalists of the
sixteenth century must have overlooked many plants native to this
island. An English botanist, in an hour's visit to Aden, discovered
several species of plants on rocks always reported, even by scientific
travellers, as absolutely barren. But after all, it appears to be well
established that the original flora of St. Helena was extremely limited,
though now counting hundreds of species.
No. 9 (page 66, _first note_). Although the vine _genus_ is very
catholic and cosmopolite in its habits, yet particular _varieties_ are
extremely fastidious and exclusive in their requirements as to soil and
climate. The stocks of many celebrated vineyards lose their peculiar
qualities by transplantation, and the most famous wines are capable of
production only in certain well-defined, and for the most part narrow
districts. The Ionian vine which bears the little stoneless grape known
in commerce as the Zante currant, has resisted almost all efforts to
naturalize it elsewhere, and is scarcely grown except in two or three of
the Ionian islands and in a narrow territory on the northern shores of
the Morea.
No. 10 (page 68, _first note_). In most of the countries of Southern
Europe, sheep and beeves are wintered upon the plains, but driven in the
summer to mountain pastures at many days' distance from the homesteads
of their owners. They transport seeds in their coats in both directions,
and hence Alpine plants often shoot up at the foot of the mountains, the
grasses of the plain on the borders of the glaciers; but in both cases,
they usually fail to propagate themselves by ripening their seed. This
explains the scattered tufts of common clover, with pale and flaccid
blossoms, which are sometimes seen at heights exceeding 7,000 feet above
the sea.
No. 11 (page 73, _last paragraph_). The poisonous wild parsnip, which is
very common in New England, is popularly believed to be identical with
the garden parsnip, and differenced only by conditions of growth, a
richer soil depriving it, it is said, of its noxious properties. Many
wild medicinal plants, such as pennyroyal for example, are so much less
aromatic and powerful, when cultivated in gardens, than when self-sown
on meagre soils, as to be hardly fit for use.
No. 12 (page 74, _second note_). See in Thoreau's _Excursions_, an
interesting description of the wild apple-trees of Massachusetts.
No. 13 (page 86, _first paragraph_). It is said at Courmayeur that a
very few ibexes of a larger variety than those of the Cogne mountains,
still linger about the Grande Jorasse.
No. 14 (page 92, _first note_). In Northern and Central Italy, one often
sees hillocks crowned with grove-like plantations of small trees, much
resembling large arbors. These serve to collect birds, which are
entrapped in nets in great numbers. These plantations are called
_ragnaje_, and the reader will find, in Bindi's edition of Davanzati, a
very pleasant description of a ragnaja, though its authorship is not now
ascribed to that eminent writer.
No. 15 (page 93, _second note_). The appearance of the dove-like grouse,
_Tetrao paradoxus_, or _Syrrhaptes Pallasii_, in various parts of
Europe, in 1859 and the following years, is a noticeable exception to
the law of regularity which seems to govern the movements and determine
the habitat of birds. The proper home of this bird is the steppes of
Tartary, and it is not recorded to have been observed in Europe, or at
least west of Russia, until the year abovementioned, when many flocks of
twenty or thirty, and even a hundred individuals, were seen in Bohemia,
Germany, Holland, Denmark, England, Ireland, and France. A considerable
flock frequented the Frisian island of Borkum for more than five months.
It was hoped they would breed and remain permanently in the island, but
this expectation has been disappointed, and the steppe-grouse seems to
have disappeared again altogether.
No. 16 (page 94, _note_). From an article by A. Esquiros, in the _Revue
des Deux Mondes_ for Sept. 1, 1864, entitled, _La vie Anglaise_, p. 119,
it appears that such occurrences as that stated in the note are not
unfrequent on the British coast.
No. 17 (page 100, _first paragraph_). I cannot learn that caprification
is now practised in Italy, but it is still in use in Greece.
No. 18 (page 112, _first note_). The recent great multiplication of
vipers in some parts of France, is a singular and startling fact.
Toussenel, quoting from official documents, states, that upon the offer
of a reward of fifty centimes, or ten cents, a head, _twelve thousand_
vipers were brought to the prefect of a single department, and that in
1859 fifteen hundred snakes and twenty quarts of snakes' eggs were found
under a farm-house hearthstone. The granary, the stables, the roof, the
very beds swarmed with serpents, and the family were obliged to abandon
its habitation. Dr. Viaugrandmarais, of Nantes, reported to the prefect
of his department more than two hundred recent cases of viper bites,
twenty-four of which proved fatal.--_Tristia_, p. 176 _et seqq._
No. 19 (page 121, _first note_). The Beduins are little given to the
chase, and seldom make war on the game birds and quadrupeds of the
desert. Hence the wild animals of Arabia are less timid than those of
Europe. On one occasion, when I was encamped during a sand storm of some
violence in Arabia Petræa, a wild pigeon took refuge in one of our tents
which had not been blown down, and remained quietly perched on a boy in
the midst of four or five persons, until the storm was over, and then
took his departure, _insalutato hospite_.
No. 20 (page 122). It is possible that time may modify the habits of the
fresh water fish of the North American States, and accommodate them to
the now physical conditions of their native waters. Hence it may be
hoped that nature, even unaided by art, will do something toward
restoring the ancient plenty of our lakes and rivers. The decrease of
our fresh water fish cannot be ascribed alone to exhaustion by fishing,
for in the waters of the valleys and flanks of the Alps, which have been
inhabited and fished ten times as long by a denser population, fish are
still very abundant, and they thrive and multiply under circumstances
where no American species could live at all. On the southern slope of
those mountains, trout are caught in great numbers, in the swift streams
which rush from the glaciers, and where the water is of icy coldness,
and so turbid with particles of fine-ground rock, that you cannot see an
inch below the surface. The glacier streams of Switzerland, however, are
less abundant in fish.
No. 21 (page 131, _note_). Vaupell, though agreeing with other writers
as to the injury done to the forest by most domestic animals--which he
illustrates in an interesting way in his posthumous work, _The Danish
Woods_--thinks, nevertheless, that at the season when the mast is
falling swine are rather useful than otherwise to forests of beech and
oak, by treading into the ground and thus sowing beechnuts and acorns,
and by destroying moles and mice.--_De Danske Skore_, p. 12.
No. 22 (page 135, _note_). The able authors of Humphreys and Abbot's
most valuable Report on the Physics and Hydraulics of the Mississippi,
conclude that the delta of that river began its encroachments on the
Gulf of Mexico not more than 4,400 years ago, before which period they
suppose the Mississippi to have been "a comparatively clear stream,"
conveying very little sediment to the sea. The present rate of advance
of the delta is 262 feet a year, and there are reasons for thinking that
the amount of deposit has long been approximately constant.--_Report_,
pp. 435, 436.
The change in the character of the river must, if this opinion is well
founded, be due to some geological revolution, or at least convulsion,
and the hypothesis of the former existence of one or more great lakes in
its upper valley, whose bottoms are occupied by the present prairie
region, has been suggested. The shores of these supposed lakes have not,
I believe, been traced, or even detected, and we cannot admit the truth
of this hypothesis without supposing changes much more extensive than
the mere bursting of the barrier which confined the waters.
No. 23 (page 143, _note_). See on this subject a paper by J. Jamin, in
the _Revue des Deux Mondes_ for Sept. 15, 1864; and, on the effects of
human industry on the atmosphere, an article in _Aus der Natur_, vol.
29, 1864, pp. 443, 449, 465 _et seqq._
No. 24 (page 159, _second paragraph_). All evergreens, even the
broad-leaved trees, resist frosts of extraordinary severity better than
the deciduous trees of the same climates. Is not this because the vital
processes of trees of persistent foliage are less interrupted during
winter than those of trees which annually shed their leaves, and
therefore more organic heat is developed?
No. 25 (page 191, _first paragraph_). In discussing the influence of
mountains on precipitation, meteorologists have generally treated the
popular belief, that mountains "attract" to them clouds floating within
a certain distance from them, as an ignorant prejudice, and they ascribe
the appearance of clouds about high peaks solely to the condensation of
the humidity of the air carried by atmospheric currents up the slopes of
the mountain to a colder temperature. But if mountains do not really
draw clouds and invisible vapors to them, they are an exception to the
universal law of attraction. The attraction of the small Mount
Shehallien was found sufficient to deflect from the perpendicular, by a
measurable quantity, a plummet weighing but a few ounces. Why, then,
should not greater masses attract to them volumes of vapor weighing
hundreds of tons, and floating freely in the atmosphere within moderate
distances of the mountains?
No. 26 (page 198, _note_). Élisée Redus ascribes the diminution of the
ponds which border the dunes of Gascony to the absorption of their water
by the trees which have been planted upon the sands.--_Revue des Deux
Mondes_, 1 Aug., 1863, p. 694.
No. 27 (page 219, _note_). The waste of wood in European carpentry was
formerly enormous, the beams of houses being both larger and more
numerous than permanence or stability required. In examining the
construction of the houses occupied by the eighty families which inhabit
the village of Faucigny, in Savoy, in 1834, the forest inspector found
that _fifty thousand_ trees had been employed in building them. The
builders "seemed," says Hudry-Menos, "to have tried to solve the problem
of piling upon the walls the largest quantity of timber possible without
crushing them."--_Revue des Deux Mondes_, 1 June, 1864, p. 601.
No. 28 (page 231, _note_). In a remarkable pamphlet, to which I shall
have occasion to refer more than once hereafter, entitled _Avant-projet
pour la création d'un sol fertile à la surface des Landes de Gascogne_,
Duponchel argues with much force, that the fertilizing properties of
river-slime are generally due much more to its mineral than to its
vegetable constituents.
No. 29 (page 265, _note_). Even the denser silicious stones are
penetrable by fluids and the coloring matter they contain, to such an
extent that agates and other forms of silex may be artificially stained
through their substance. This art was known to and practised by the
ancient lapidaries, and it has been revived in recent times.
No. 30 (page 268). There is good reason for thinking that many of the
earth and rock slides in the Alps occurred at an earlier period than the
origin of the forest vegetation which, in later ages, covered the flanks
of those mountains. See _Bericht über die Untersuchung der
Schweizerischen Hochgebirgswaldungen_. 1862. P. 61.
Where more recent slides have been again clothed with woods, the trees,
shrubs, and smaller plants which spontaneously grow upon them are
usually of different species from those observed upon soil displaced at
remote periods. This difference is so marked that the site of a slide
can often be recognized at a great distance by the general color of the
foliage of its vegetation.
No. 31 (page 286, _note_). It should have been observed that the
venomous principle of poisonous mushrooms is not decomposed and rendered
innocent by the process described in the _note_. It is merely extracted
by the acidulated or saline water employed for soaking the plants, and
care should be taken that this water be thrown away out of the reach of
mischief.
No. 32 (page 293, _note_). Gaudry estimates the ties employed in the
railways of France at thirty millions, to supply which not less than two
millions of large trees have been felled. These ties have been, upon the
average, at least once renewed, and hence we must double the number of
ties and of trees required to furnish them.--_Revue des Deux Mondes_, 15
July, 1863, p. 425.
No. 33 (page 294, _second paragraph of note_). After all, the present
consumption of wood and timber for fuel and other domestic and rural
purposes, in many parts of Europe, seems incredibly small to an
American. In rural Switzerland, the whole supply of firewood,
fuel for small smitheries, dairies, breweries, brick and lime
kilns, distilleries, fences, furniture, tools, and even house
building--exclusive of the small quantity derived from the trimmings
of fruit trees, grape vines and hedges, and from decayed fences and
buildings--does not exceed an average of _two hundred and thirty cubic
feet_, or less than two cords, a year per household. The average
consumption of wood in New England for domestic fuel alone, is from five
to ten times as much as Swiss families require for all the uses above
enumerated. But the existing habitations of Switzerland are sufficient
for a population which increases but slowly, and in the peasants' houses
but a single room is usually heated. See _Bericht über die Untersuchung
der Schweiz. Hochgebirgswaldungen_, pp. 85-89.
No. 34 (page 304). Among more recent manuals may be mentioned: _Les
Études de Maitre Pierre._ Paris, 1864. 12mo; BAZELAIRE, _Traité de
Reboisement_. 2d edition, Paris, 1864; and, in Italian, SIEMONI,
_Manuale teorico-pratico d'arte Forestale_. Firenze, 1864. 8vo. A very
important work has lately been published in France by Viscount de
Courval, which is known to me only by a German translation published at
Berlin, in 1864, under the title, _Das Aufästen der Waldbäume_. The
principal feature of De Courval's very successful system of
sylviculture, is a mode of trimming which compels the tree to develop
the stem by reducing the lateral ramification. Beginning with young
trees, the buds are rubbed off from the stems, and superfluous lateral
shoots are pruned down to the trunk. When large trees are taken in hand,
branches which can be spared, and whose removal is necessary to obtain a
proper length of stem, are very smoothly cut off quite close to the
trunk, and the exposed surface is _immediately_ brushed over with
mineral-coal tar. When thus treated, it is said that the healing of the
wound is perfect, and without any decay of the tree.
No. 35 (page 313). The most gorgeous autumnal coloring I have observed
in the vegetation of Europe, has been in the valleys of the Durance and
its tributaries in Dauphiny. I must admit that neither in variety nor in
purity and brilliancy of tint, does this coloring fall much, if at all,
short of that of the New England woods. But there is this difference: in
Dauphiny, it is only in small shrubs that this rich painting is seen,
while in North America the foliage of large trees is dyed in full
splendor. Hence the American woodland has fewer broken lights and more
of what painters call breadth of coloring. Besides this, the arrangement
of the leafage in large globular or conical masses, affords a wider
scale of light and shade, thus aiding now the gradation, now the
contrast of tints, and gives the American October landscape a softer and
more harmonious tone than marks the humble shrubbery of the forest
hill-sides of Dauphiny.
Thoreau--who was not, like some very celebrated landscape critics of the
present day, an outside spectator of the action and products of natural
forces, but, in the old religious sense, an _observer_ of organic
nature, living, more than almost any other descriptive writer, among and
with her children--has a very eloquent paper on the "Autumnal Tints" of
the New England landscape.--See his _Excursions_, pp. 215 _et seqq._
Few men have personally noticed so many facts in natural history
accessible to unscientific observation as Thoreau, and yet he had never
seen that very common and striking spectacle, the phosphorescence of
decaying wood, until, in the latter years of his life, it caught his
attention in a bivouac in the forests of Maine. He seems to have been
more excited by this phenomenon than by any other described in his
works. It must be a capacious eye that takes in all the visible facts in
the history of the most familiar natural object.--_The Maine Woods_, p.
184.
"The luminous appearance of bodies projected against the sky adjacent to
the rising" or setting sun, so well described in Professor Necker's
Letter to Sir David Brewster, is, as Tyndall observes, "hardly ever seen
by either guides or travellers, though it would seem, _prima facie_,
that it must be of frequent occurrence." See TYNDALL, _Glaciers of the
Alps_. Part I. Second ascent of Mont Blanc.
Judging from my own observation, however, I should much doubt whether
this brilliant phenomenon can be so often seen in perfection as would be
expected; for I have frequently sought it in vain at the foot of the
Alps, under conditions apparently otherwise identical with those where,
in the elevated Alpine valleys, it shows itself in the greatest
splendor.
No. 36 (page 314). European poets, whose knowledge of the date palm is
not founded on personal observation, often describe its trunk as not
only slender, but particularly _straight_. Nothing can be farther from
the truth. When the Orientals compare the form of a beautiful girl to
the stem of the palm, they do not represent it as rigidly straight, but
on the contrary as made up of graceful curves, which seem less like
permanent outlines than like flowing motion. In a palm grove, the
trunks, so far from standing planted upright like the candles of a
chandelier, bend in a vast variety of curves, now leaning towards, now
diverging from, now crossing, each other, and among a hundred you will
hardly see two whose axes are parallel.
No. 37 (page 316, _first note_). Charles Martin ascribes the power of
reproduction by shoots from the stump to the cedar of Mount Atlas, which
appears to be identical with the cedar of Lebanon.--_Revue des Deux
Mondes_, 15 July, 1864, p. 315.
No. 38 (page 332). In an interesting article on recent internal
improvements in England, in the London Quarterly Review for January,
1858, it is related that in a single rock cutting on the Liverpool and
Manchester railway, 480,000 cubic yards of stone were removed; that the
earth excavated and removed in the construction of English railways up
to that date, amounted to a hundred and fifty million cubic yards, and
that at the Round Down Cliff, near Dover, a single blast of nineteen
thousand pounds of powder blew down a thousand million tons of chalk,
and covered fifteen acres of land with the fragments.
No. 39 (page 339). According to Reventlov, whose work is one of the best
sources of information on the subject of diking-in tide-washed flats,
_Salicornia herbacea_ appears as soon as the flat is raised high enough
to be dry for three hours at ordinary ebb tide, or, in other words,
where the ordinary flood covers it to a depth of not more than two feet.
At a flood depth of one foot, the _Salicornia_ dies and is succeeded by
various sand plants. These are followed by _Poa distans_ and _Poa
maritima_ as the ground is raised by further deposits, and these plants
finally by common grasses. The _Salicornia_ is preceded by _confervæ_,
growing in deeper water, which spread over the bottom, and when covered
by a fresh deposit of slime reappear above it, and thus vegetable and
alluvial strata alternate until the flat is raised sufficiently high for
the growth of _Salicornia_.--_Om Marskdannelsen paa Vestkysten af
Hertugdömmet Slesvig_, pp. 7, 8.
No. 40 (page 348, _note_). The drijftil employed for the ring dike of
the Lake of Haarlem, was in part cut in sections fifty feet long by six
or seven wide, and these were navigated like rafts to the spot where
they were sunk to form the dike.--EMILE DE LAVELEYE, _Revue des Deux
Mondes_, 15 Sept., 1863, p. 285.
No. 41 (page 352, _last paragraph_). See on the influence of the
improvements in question on tidal and other marine currents, Staring,
_De Bodem van Nederland_, I. p. 279.
Although the dikes of the Netherlands and the adjacent states have
protected a considerable extent of coast from the encroachments of the
sea, and have won a large tract of cultivable land from the dominion of
the waters, it has been questioned whether a different method of
accomplishing these objects might not have been adopted with advantage.
It has been suggested that a system of inland dikes and canals, upon the
principle of those which, as will be seen in a subsequent part of the
chapter on the waters, have been so successfully employed in the Val di
Chiana and in Egypt, might have elevated the low grounds above the ocean
tides, by spreading over them the sediment brought down by the Rhine,
the Maes, and the Scheld. If this process had been introduced in the
Middle Ages and constantly pursued to our times, the superficial and
coast geography, as well as the hydrography of the countries in
question, would undoubtedly have presented an aspect very different from
their present condition; and by combining the process with a system of
maritime dikes, which would have been necessary, both to resist the
advance of the sea and to retain the slime deposited by river overflows,
it is possible that the territory of those states would have been as
extensive as it now is, and, at the same time, more elevated by several
feet. But it must be borne in mind that we do not know the proportions
in which the marine deposits that form the polders have been derived
from materials brought down by these rivers or from other more remote
sources. Much of the river slime has no doubt been transported by marine
currents quite beyond the reach of returning streams, and it is
uncertain how far this loss has been balanced by earth washed by the sea
from distant shores and let fall on the coasts of the Netherlands and
other neighboring countries.
We know little or nothing of the quantity of solid matter brought down
by the rivers of Western Europe in early ages, but, as the banks of
those rivers are now generally better secured against wash and abrasion
than in former centuries, the sediment transported by them must be less
than at periods nearer the removal of the primitive forests of their
valleys. Klöden states the quantity of sedimentary matter now annually
brought down by the Rhine at Bonn to be sufficient only to cover a
square English mile to the depth of a little more than a
foot.--_Erdkunde_, I. p. 384.
No. 42 (page 358, _first paragraph_). Meteorological observations have
been regularly recorded at Zwanenburg, near the north end of the Lake of
Haarlem, for more than a century, and since 1845 a similar register has
been kept at the Helder, forty or fifty miles farther north. In
comparing these two series of observations, it is found that about the
end of the year 1852, when the drawing off of the waters of the Lake of
Haarlem was completed, and the preceding summer had dried the grounds
laid bare so as greatly to reduce the evaporable surface, a change took
place in the relative temperature of the two stations. Taking the mean
of every successive period of five days from 1845 to 1852, the
temperature at Zwanenburg was thirty-three hundredths of a centigrade
degree _lower_ than at the Helder. Since the end of 1852, the
thermometer at Zwanenburg has stood, from the 11th of April to the 20th
of September inclusive, twenty-two hundredths of a degree _higher_ than
at the Helder, but from the 14th of October to the 17th of March, it has
averaged one-tenth of a degree _lower_ than its mean between the same
dates before 1853.
There is no reasonable doubt that these differences are due to the
draining of the lake. There has been less refrigeration from evaporation
in summer, and the ground has absorbed more solar heat at the same
period, while in the winter it has radiated more warmth then when it was
covered with water. Doubtless the quantity of humidity contained in the
atmosphere has also been affected by the same cause, but observations do
not appear to have been made on that point. See KRECKE, _Het Klimaat van
Nederland_, II. 64.
No. 43 (page 358, _note_). In the course of the present year (1864),
there have been several land slips on the borders of the Lake of Como,
and in one instance the grounds of a villa lying upon the margin of the
water suffered a considerable displacement. If the lake should be
lowered to any considerable extent, in pursuance of the plan mentioned
in the note on page 358, there is ground to fear that the steep shores
of the lake might, at some points, be deprived of a lateral pressure
requisite to their stability, and slide into the water as on the Lake of
Lungern. See p. 356.
No. 44 (page 369, _last paragraph but one of note_). In like manner,
while the box, the cedar, the fir, the oak, the pine, "beams," and
"timber," are very frequently mentioned in the Old Testament, not one of
these words is found in the New, _except_ the case of the "beam in the
eye," in the parable in Matthew and Luke.
No. 45 (page 375, _note_). In all probability, the real change effected
by human art in the superficial geography of Egypt, is the conversion of
pools and marshes into dry land, by a system of transverse dikes, which
compelled the flood water to deposit its sediment on the banks of the
river instead of carrying it to the sea. The _colmate_ of modern Italy
were thus anticipated in ancient Egypt.
No. 46 (page 378). We have seen in _Appendix_, No. 42, _ante_, that the
mean temperature of a station on the borders of the Lake of Haarlem--a
sheet of water formerly covering sixty-two and a half square English
miles--for the period between the 11th of April and the 20th of
September, had been raised not less than a degree of Fahrenheit by the
draining of that lake; or, to state the case more precisely, that the
formation of the lake, which was a consequence of man's improvidence,
had reduced the temperature one degree F. below the natural standard.
The artificially irrigated lands of France, Piedmont, and Lombardy,
taken together, are fifty times as extensive as the Lake of Haarlem, and
they are situated in climates where evaporation is vastly more rapid
than in the Netherlands. They must therefore, no doubt, affect the local
climate to a far greater extent than has been observed in connection
with the draining of the lake in question. I do not know that special
observations have been made with a view to measure the climatic effects
of irrigation, but in the summer I have often found the _morning_
temperature, when the difference would naturally be least perceptible,
on the watered plains of Piedmont, nine miles south of Turin, several
degrees lower than that recorded at an observatory in the city.
No. 47 (page 391, _note_). The Roman aqueduct known as the Pont du Gard,
near Nismes, was built, in all probability, nineteen centuries ago. The
bed of the river Gardon, a rather swift stream, which flows beneath it,
can have suffered but a slight depression since the piers of the
aqueduct were founded.
No. 48 (page 393, _first note_). Duponchel makes the following
remarkable statement: "The river Herault rises in a granitic region, but
soon reaches calcareous formations, which it traverses for more than
sixty kilometres, rolling through deep and precipitous ravines, into
which the torrents are constantly discharging enormous masses of pebbles
belonging to the hardest rocks of the Jurassian period. These debris,
continually renewed, compose, even below the exit of the gorge where the
river enters into a regular channel cut in a tertiary deposit, broad
beaches, prodigious accumulations of rolled pebbles, extending several
kilometres down the stream, but they diminish in size and weight so
rapidly that above the mouth of the river, which is at a distance of
thirty or thirty-five kilometres from the gorge, every trace of
calcareous matter has disappeared from the sands of the bottom, which
are exclusively silicious."--_Avant-projet pour la création d'un sol
fertile_, etc., p. 20.
No. 49 (page 404, _first paragraph of second note_). The length of the
lower course of the Po having been considerably increased by the filling
up of the Adriatic with its deposits, the velocity of the current ought,
_prima facie_, to have been diminished and its bed raised in proportion.
There are grounds for believing that this has happened in the case of
the Nile, and one reason why the same effect has not been more sensibly
perceptible in the Po is, that the confinement of the current by
continuous embankments gives it a high-water velocity sufficient to
sweep out deposits let fall at lower stages and slower movements of the
water. Torrential streams tend first to excavate, then to raise, their
beds. No general law on this point can be stated in relation to the
middle and lower course of rivers. The conditions which determine the
question of the depression or elevation of a river bed are too
multifarious, variable, and complex to be subjected to formulæ, and they
can scarcely even be enumerated. See, however, note on p. 431.
No. 50 (page 406, _first paragraph_). The system proposed in the text is
substantially the Egyptian method, the Nile dikes having been
constructed rather to retain than to exclude the water. The waters of
rivers which flow down planes of gentle inclination, deposit in their
inundations the largest proportion of their sediment as soon as, by
overflowing their banks, they escape from the swift current of the
channel, and consequently the immediate banks of such rivers become
higher than the grounds lying farther from the stream. In the
"intervals," or "bottoms," of the great North American rivers, the
alluvial banks are elevated and dry, the flats more remote from the
river lower and swampy. This is generally observable in Egypt, though
less so than in the valley of the Mississippi, where, below Cape
Girardeau, the alluvial banks constitute natural glacis descending as
you recede from the river, at an average of seven feet in the first
mile.--HUMPHREYS AND ABBOT'S _Report_, pp. 96, 97.
The Egyptian crossdikes, by retaining the water of the inundations,
compel it to let fall its remaining slime, and hence the elevation of
the remoter land goes on at a rate not very much slower than that of the
immediate banks. Probably transverse embankments would produce the same
effect in the Mississippi valley. In the great floods of this river, it
is observed that, at a certain distance from the channel, the bottoms,
though lower than the banks, are flooded to a less depth. See cross
sections in Plate IV. of Humphreys and Abbot's Report. This apparently
anomalous fact is due, I suppose, to the greater swiftness of the
current of the overflowing water in the low grounds, which are often
drained through the channels of rivers whose beds lie at a lower level
than that of the Mississippi, or by the bayous which are so
characteristic a feature of the geography of that valley. A judicious
use of dikes would probably convert the swamps of the lower Mississippi
valley into a region like Egypt.
No. 51 (_second note_). The mean discharge of the Mississippi is 675,000
cubic feet per second, and, accordingly, that river contributes to the
sea about eleven times as much water as the Po, and more than sis and
a half times as much as the Nile. The discharge of the Mississippi
is estimated at one-fourth of the precipitation in its basin,
certainly a very large proportion, when we consider the rapidity of
evaporation in many parts of the basin, and the probable loss by
infiltration.--HUMPHREYS AND ABBOT'S _Report_, p. 93.
No. 52 (page 423, _first paragraph_). Artificially directed currents of
water have been advantageously used in civil engineering for displacing
and transporting large quantities of earth, and there is no doubt that
this agency might be profitably employed to a far greater extent than
has yet been attempted. Some of the hydraulic works in California for
washing down masses of auriferous earth are on a scale stupenduous
enough to produce really important topographical changes.
No. 53 (page 435, _first note_). I have lately been informed by a
resident of the Ionian Islands, who is familiar with this phenomenon,
that the sea flows uninterruptedly into the sub-insular cavities, at all
stages of the tide.
No. 54 (page 438, _note_). It is observed in Cornwall that deep mines
are freer from water in artificially well-drained, than in undrained
agricultural districts.--ESQUIROS, _Revue des Deux Mondes_, Nov. 15,
1863, p. 430.
No. 55 (page 441). See, on the Artesian wells of the Sahara, and
especially on the throwing up of living fish by them, an article
entitled, _Le Sahara_, etc., by Charles Martins, in the _Revue des Deux
Mondes_ for August 1, 1864, pp. 618, 619.
No. 56 (page 444, _first note_). From the article in the _Rev. des Deux
Mondes_, referred to in the preceding note, it appears that the wells
discovered by Ayme were truly artesian. They were bored in rock, and
provided at the outlet with a pear-shaped valve of stone, by which the
orifice could be closed or opened at pleasure.
No. 57 (page 447, _second note_). Hull ingeniously suggests that,
besides other changes, fine sand intermixed with or deposited above a
coarser stratum, as well as the minute particles resulting from the
disintegration of the latter, may be carried by rain in the case of
dunes, or by the ordinary action of sea water in that of subaqueous
sandbanks, down through the interstices in the coarser layer, and thus
the relative position of fine sand and gravel may be more or less
changed.--_Oorsprong der Hollandsche Duinen_, p. 103.
No. 58 (page 479). It appears from Laurent, that marine shells, of
extant species, are found in the sands of the Sahara, far from the sea,
and even at considerable depths below the surface.--_Mémoires sur le
Sahara Oriental_, p. 62.
This observation has been confirmed by late travellers, and is an
important link in the chain of evidence which tends to prove that the
upheaval of the Libyan desert is of comparatively recent date.
No. 59 (p. 480). "At New Quay [in England] the dune sands are converted
to stone by an oxyde of iron held in solution by the water which
pervades them. This stone, which is formed, so to speak, under our eye,
has been found solid enough to be employed for building."--ESQUIROS,
_L'Angleterre et la vie Anglaise_, _Revue des Deux Mondes_, 1 March,
1864, pp. 44, 45.
No. 60 (page 496, _first paragraph_). In Ditmarsh, the breaking of the
surface by the man[oe]uvering of a corps of cavalry let loose a
sand-drift which did serious injury before it was subdued.--KOHL,
_Inseln u. Marschen._ etc., III. p. 282.
Similar cases have occurred in Eastern Massachusetts, from equally
slight causes.--See THOREAU, _A Week on the Concord and Merrimack
Rivers_, pp. 151-208.
No. 61 (page 497, _last note_). A more probable explanation of the fact
stated in the note is suggested by Èlisée Reclus, in an article
entitled, _Le Littoral de la France_, in the _Revue des Deux Mondes_ for
Sept. 1, 1864, pp. 193, 194. This able writer believes such pools to be
the remains of ancient maritime bays, which have been cut off from the
ocean by gradually accumulated sand banks raised by the waves and winds
to the character of dunes.
No. 62 (page 506, _note_). The statement in the note is confirmed by
Olmsted: "There is not a sufficient demand for rosin, except of the
first qualities, to make it worth transporting from the inland
distilleries; it is ordinarily, therefore, conducted off to a little
distance, in a wooden trough, and allowed to flow from it to waste upon
the ground. At the first distillery I visited, which had been in
operation but one year, there lay a congealed pool of rosin, estimated
to contain over three thousand barrels."--_A Journey in the Seaboard
Slave States_, 1863, p. 345.
No. 63 (page 507). In an article on the dunes of Europe, in Vol. 29
(1864) of _Aus der Natur_, p. 590, the dunes are estimated to cover, on
the islands and coasts of Schleswig Holstein, in Northwest Germany,
Denmark, Holland, and France, one hundred and eighty-one German, or
nearly four thousand English square miles; in Scotland, about ten
German, or two hundred and ten English miles; in Ireland, twenty German,
or four hundred and twenty English miles; and in England, one hundred
and twenty German, or more than twenty-five hundred English miles.
No. 64 (page 512, _last paragraph_). For a brilliant account of the
improvement of the Landes, see Edmond About, _Le Progrès_, Chap, VII.
In the memoir referred to in _Appendix_, No. 48, _ante_, Duponchel
proposes the construction of artificial torrents to grind calcareous
rock to slime by rolling and attrition in its bed, and, at the same
time, the washing down of an argillaceous deposit which is to be mixed
with the calcareous slime and distributed over the Landes by
watercourses constructed for the purpose. By this means, he supposes
that a highly fertile soil could be formed on the surface, which would
also be so raised by the process as to admit of freer drainage. That
nothing may be wanting to recommend this project, Duponchel suggests
that, as some of the rivers of Western France are auriferous, it is
probable that gold enough may be collected from the washings to reduce
the cost of the operations materially.
No. 65 (page 528, _first paragraph_). The opening of a channel across
Cape Cod would have, though perhaps to a smaller extent, the same
effects in interchanging the animal life of the southern and northern
shores of the isthmus, as in the case of the Suez canal; for although
the breadth of Cape Cod does not anywhere exceed twenty miles, and is in
some places reduced to one, it appears from the official reports on the
Natural History of Massachusetts, that the population of the opposite
waters differs widely in species.
Not having the original documents at hand, I quote an extract from the
_Report on the Invertebrate Animals of Mass._, given by Thoreau,
_Excursions_, p. 69: "The distribution of the marine shells is well
worthy of notice as a geological fact. Cape Cod, the right arm of the
Commonwealth, reaches out into the ocean some fifty or sixty miles. It
is nowhere many miles wide; but this narrow point of land has hitherto
proved a barrier to the migration of many species of mollusca. Several
genera and numerous species, which are separated by the intervention of
only a few miles of land, are effectually prevented from mingling by the
Cape, and do not pass from one side to the other * * * * Of the one
hundred and ninety-seven marine species, eighty-three do not pass to the
south shore, and fifty are not found on the north shore of the Cape."
Probably the distribution of the species of mollusks is affected by
unknown local conditions, and therefore an open canal across the Cape
might not make every species that inhabits the waters on one side
common to those of the other; but there can be no doubt that there would
be a considerable migration in both directions.
The fact stated in the report may suggest an important caution in
drawing conclusions upon the relative age of formations from the
character of their fossils. Had a geological movement or movements
upheaved to different levels the bottoms of waters thus separated by a
narrow isthmus, and dislocated the connection between those bottoms,
naturalists, in after ages, reasoning from the character of the fossil
faunas, might have assigned them to different, and perhaps very widely
distant, periods.
No. 66 (page 548, _first paragraph_). To the geological effects of the
thickening of the earth's crust in the Bay of Bengal, are to be added
those of thinning it on the highlands where the Ganges rises. The same
action may, as a learned friend suggests to me, even have a cosmical
influence. The great rivers of the earth, taken as a whole, transport
sediment from the polar regions in an equatorial direction, and hence
tend to increase the equatorial diameter, and at the same time, by their
inequality of action, to a continual displacement of the centre of
gravity, of the earth. The motion of the globe and of all bodies
affected by its attraction, is modified by every change of its form, and
in this case we are not authorized to say that such effects are in any
way compensated.
INDEX
Abbeys of St. Germain and St. Denis, revenues of, 6.
Adirondack forest, 235;
lakes of, 357.
Ailanthus glandulosa, 515.
Akaba, gulf of, infiltration of fresh water in, 440.
Albano, lake of, artificial lowering of, 353.
Algeria, deserts of, artesian wells in, 443;
sand dunes of, 463;
consolidated dunes, 480.
Alpaca, South American, 83.
Amazon, Indians of, 11.
Ameland, island of, 499.
America, North, primitive physical condition of, 27, 43;
forests of, 28;
possibility of noting its physical changes, 52;
by scientific observation, 53;
forest trees of, 274;
sand dunes of, 469;
proposed changes in hydrography of, 532.
Animal life, sympathy of ruder races with, 39;
instinct, fallibility of, 40;
hostility of civilized man to inferior forms of, 121.
Animals, wild, action of on vegetation, 78.
Aphis, the European, 104.
Apennines, effects of felling the woods on, 150, 152.
Appian way, the, 542.
Aqueducts, geographical and climatic effects of, 358.
Arabia Petræa, surface drainage of, 440;
sandstone of, 452;
sands and petrified wood of, 455;
wadies of, 538.
Aragua, valley of, Venezuela, 202.
Ararat, Mt., phenomenon of vegetation on, 287.
Ardèche, l', department of, 152;
destruction of forests in, 389.
-- river and basin, floods of, 386;
supply of water to the Rhone, 388, 398;
violence of inundations of, 388;
damage done by, 390;
effect on river beds, 391;
force of its affluents, 392.
Argostoli, Cephalonia, millstreams of, 434.
Armenia, ancient irrigation of, 366.
Arno, the river, deposits of, 414;
upper course of in the Val di Chiana, 417, 420.
Artesian wells, their sources, 441;
usual objects, 442;
occasional effects, 442;
employment in the Algerian desert, 443;
by the French Government, 444;
success and probable results of, 445;
known to the ancients, 443;
depth of, 444.
Arundo arenaria, 501.
Ascension, island of, 205.
Auk, the wingless, extirpation of, 95.
Australia a field of physical observation, 51.
Avalanches, Alpine, various causes of, 266;
by felling trees, 270.
Azoff, sea of, proposed changes, 531.
Babinet, plan for artificial springs, by, 448.
Baikal Lake, the fish of, 117.
Baltic Sea, sand dunes of, 467.
Barcelonette, valley of, former fertility, 243;
present degradation of, 244.
Bavaria, scarcity of fuel in, 299.
Bear, the mythical character of, 40.
Beaver, the, agency in forming bogs, 31;
cause of its increased numbers, 84.
Bee, the honey, products of, 105;
introduction in United States, 106.
Belgium, effect of plantations in, 152;
Campine of, 513.
Ben Gâsi, district of, rock formation in, 537.
Bergamo, change of climate in the valley of, 151.
Bibliographical list of authorities, vii.
Birch tree (black and yellow), produce of, 171.
Birds, number of, in United States, 86;
the turkey, dove, pigeon, 87;
as sowers and consumers of seeds, 87;
as destroyers of insects, 89;
injurious extirpation of, 90;
wanton destruction of, 92;
weakness of, 93;
instinct of migratory, 94;
extinction of species, 95;
commercial value of, 97;
introduction of species, 98.
Bison, the American, 78;
number and migrations of, 81, 83;
domesticated, 135.
Blackbird, the proscription of, 91.
Bogs, formation and nomenclature of, 29-32;
of New England, 29;
repositories of fuel, 30.
Brémontier, system of dune plantations of, 503;
a benefactor to his race, 515.
Breton, Cap, dune vineyards of, 508.
Busbequius' letters, 64.
Camel, the, transfer and migrations of, 83;
injurious to vegetation, 132.
Campine of Belgium, 513.
Canada thistle, the, 68.
Canals, geographic and climatic effects of, 359;
injurious effects of Tuscan, 359;
projected, Suez, 519;
Isthmus of Darien, 522;
to the Dead Sea, 524;
maritime, in Greece, 526;
Saros, 527;
Cape Cod, 528;
the Don and the Volga, 531;
Lake Erie and the Genesee, 532;
Lake Michigan and the Mississippi, 533.
Cape Cod, sand dunes of, 487;
legislative protection of, 502;
vegetation of, 503;
projected canal through, 528.
Cappercailzie, the, extinction of, in Britain, 96.
Carniola, caves of, 434.
Caspian Sea, proposed changes in its basin, 531.
Catania, lava streams of, 544.
Catavothra of Greece, 536.
Cévennes, effects of clearing the, 153.
Champlain, lake, dates of its congelation, 163.
Cherbourg, breakwater of, 46, 332.
Chiana, Val di, description and character of, 417-420;
plans for its restoration, 420;
artificial drainage of, attempted, 421;
successfully executed, 423.
Clergy, mediæval, their character, 282.
Climatic change, discussions of, 9;
how tested, 20;
causes producing, in New England, Africa, Arabia Petræa, 20-22;
man's action on, difficult to ascertain, 51;
deterioration, 71.
Coal mines, combustion of, 546.
Coal, sea, early use of, for fuel, 222;
increased use of, in Paris, 295.
Coast line, change of, from natural causes, 331;
subject to human guidance, 332.
Cochineal insect transferred to Spain, 105.
Cochituate Aqueduct, Boston, 103.
Col Isoard, valley of, devastated, 242.
Commerce, modern, on what dependent, 60.
Como, lake of, proposed lowering of, 358.
Constance, lake of, 534.
Cork-oak tree, yield of, 311.
Corporations, social and political, influence of, 54.
Cosmical influences, 13.
Cotton, early cultivation of, 61;
can be raised by white labor, 381.
Crawley Sparrow Club, 90.
Currents, sea, strength of, 456;
in the Bosphorus, 457.
Cuyahoga river, 208.
Cypress tree, its beauty, 314.
Darien, Isthmus of, proposed canal across, 522;
conjectural effects of, 523.
Dead Sea, projected canals to, 524;
possible results of, 525.
Deer, numbers of, in United States; 82;
tame, injurious to trees, 130.
Denmark, peat mosses of, 22;
dunes of, 497;
extent and movement of, 498;
legislative protection of, 501, 504.
Desert, the, richness of local color, 445;
mirage in, 446.
Des Plaines river, 533.
Despotism a cause of physical decay, 5.
Dikes, recovery of land by, in the Netherlands, 335;
early usage and immense extent of, 336;
encouraged by the Spaniards, 337;
details of their construction and effect on the land
gained, 340-345;
in Egypt, 413.
Dinornis, or moa, recent extirpation of, in New Zealand, 95.
Dodo, the, extirpation of, 95.
Domestic animals, action of, on vegetation, 79;
origin and transfer of, 82;
injurious to the forest growth, 130.
Don river, proposed diversion of, 531.
Draining a geographical element, 360;
superficial, its necessity in forest lands, 363;
effect on temperature, 364;
underground, _ib._;
extensive use of, in England, 362;
affects the atmosphere, 364;
disturbs the equilibrium of river supply, 365;
by boring, 362;
in France, &c., 362;
Paris, 363.
Drance, Switzerland, glacier lake of, 403.
Dry land and water, relative extent of, 178.
Dwight, Dr., Travels in the United States, characterized, 52.
Earth, fertile, below the rock, 537;
transported to cover rocky surfaces, 537.
Earthquakes, effects of, 542;
causes and possible prevention of, 543;
of Lisbon, 544.
Earthworm, utility of, in agriculture, 100;
multiplication of, in New England, 101.
Egypt, catacombs, 70;
papyrus or water lily, 70;
poisonous snakes of, 112;
supposed increase of rain in, 190;
productiveness of, 230;
necessity and extent of irrigation in, 368, 373;
cultivated soil of, 372, 374;
population of, 374;
amount of water used for irrigation, 380;
saline deposits, 382;
artificial river courses of, 402;
cultivated area of, 412;
sands of, 458;
their prevalence and extent, 459;
source of, 461;
action on the Delta and cultivated land, 462;
effect of the diversion of the Nile on, 529;
refuse heaps near Cairo, 541.
Eland, the, preserved in Prussia, 86.
Elm, the Washington, Cambridge, 146.
Elsineur, artificial formation in harbor of, 539.
England, forest economy of, 221;
large extent of ornamental plantations, 222;
Forests of, described by Cæsar, 222;
private enterprise in sylviculture, 292;
sand dunes of, 507.
Enguerrand de Coucy, cruelty of, 281.
Erie Canal, the, influence on the fauna and flora of its region, 116;
lake, depth and level of, 532;
proposed canal from, 532.
Espy's theories of artificial rain, 547.
Etna, volcanic lava and dust, 131.
Euphrates, sand plains in the valley of, 511.
Eye, cultivation of the, 11;
control of the limbs by, 12;
trained by the study of physical geography, 12.
Feudalism, pernicious influence of, 6.
Fir tree, the, its products, 311.
Fire weed, in burnt forests of the United States, 287.
Fish, destruction of, by man, 112, 114, 120, 122;
voracity of, 114;
introduction and breeding of foreign, 116;
naturalization of, 117;
inferiority of the artificially fattened, 121.
Fish, shell, extensive remains of, in United States, 117;
of Indian origin, 128.
Fish ponds of Catholic countries, 426.
Fontainebleau, forest of, 34, 130;
poaching in, 284;
its renovation, 316;
soil of, 513.
Food, ancient arts of preservation of, 18.
Forest, the, influence of, on the humidity of air, 162;
do. of earth, 165;
as organic, 166;
balance of conflicting influences in, 176;
influence on temperature, 178;
on precipitation, 181, 196;
in South America, 184;
the Canary Islands and Asia Minor, 185;
Peru, 188;
Palestine, Southern France, Scotland and Egypt, 189;
influence of, on humidity of soil, 196;
on springs, 197;
in Venezuela, 202;
New Granada, 204;
Switzerland and France, 205, 208;
United States, 207;
in winter, 210;
general consequences of its destruction, 214;
on the earth, springs, rivers, 215;
literature of, in France, 217;
Germany, 218;
Italy, 218;
England, 221;
influence of, on inundations, 223;
in North America, 225;
disputed effects of, in Europe, 228;
principal causes of its destruction, 270;
in British America, 271;
in Europe, 279;
royal forests, 280;
effects of the Revolution on, in France, 284;
utility of, for the preservation of smaller plants, 286, 290;
do. of birds, 291;
economic utility of, and necessity for its restoration, 292;
extent of, in Europe, 296;
proportion in different countries of, 300;
of the United States and Canada, 300;
economy of, 303;
management of, in France, 304;
European forests, all of artificial growth, 305;
artificial and natural, their respective advantages, 307;
American do., their peculiar characteristics, 313;
economic action of cattle on, 325;
duty of preserving, 327;
average revenue from, 327;
regulated by laws in France, 395.
See _Trees_, _Woods_.
Forests of North America, balance of geographical elements in, 27;
agency of quadrupeds and insects in, 32;
injury to, by insects, 33;
meteorological importance of, 139.
Forest laws, mediæval, character of, 217;
do. Jewish, 217;
severity of, in France and England, 280;
under Louis IX., 281;
of America, created by circumstances, 302.
France, forest literature and economy of, 217;
legislation on forests, 233;
-- Southeastern, former physical state of, 237;
altered condition of, 239;
royal forests of, and forest laws, 280;
extent of, in, 296;
ancient lakes of, 357;
inundations of 1856 in, 393;
remedies against inundations in, 395;
sand dunes of Western, 485;
encroachments of the sea on, 494.
French peasantry, described by La Bruyere, 6;
do. Arthur Young, 7;
of Chambord, 283.
Friesland, sand dunes of, 489.
Fucinus Lake (Lago di Celano), drainage of, by the Romans, 354;
moderns, 355.
Game Laws, effect on the numbers of birds in France, 91;
in England and Italy, 92;
severity of, in France, 283;
unable to stop poaching, 284.
Ganges, valley of the, 548.
Gascony, coast sands of, 453;
dunes of, 496;
extent and advance of, 497;
fixing and reclaiming of, 504;
Landes of, 511;
their reclamation, 512.
Geological influences, 13.
Geographers, new school of, 8.
Geographical influence of changes produced by man, 352.
Geography, modern, improved form of, 57.
German Ocean, sands of, 454, 457.
Germany, extent of forests in, 299.
Glacier lakes in Switzerland, 403.
Goat, the Cashmere or Thibet, 83.
Gold fish, the migration from China, 116.
Goldau, Switzerland, destruction of, 268.
Grape disease, its economic effect in France, Italy, Sicily, 72.
Grasshopper, the rapid increase in America, 291.
Gravedigger beetle, the, 107.
Greece,
proposed maritime canals in, through the Corinthian Isthmus, 526;
Mount Athos, 527;
subterranean waters of, 536.
Gulls, sea, habits of, 98.
Gulf stream, the, 523.
Gunpowder chiefly used for industrial purposes, 335.
Haarlem Lake, origin and extent of, 346, 347;
reasons for draining it, 348;
means employed, 349;
successful results, 350.
Hauran, the productions of, its soil, 74.
Heilbronn, springs at, 207.
Herring fishery, produce of, 120.
Hessian fly, introduction of in the United States, 104.
Honey bee, the wild, New England, legal usage, 302.
Humid air, movement of, 183.
Hunter in New England, exploits of, 82.
Ibex, the Alpine, 86.
India, saline efflorescence of its soil, 382;
natural connection of rivers in, 401.
Insects, injurious to vegetable life, 33;
utility of, 99;
agency in the fertilization of orchids, 102;
mass of their exuviæ in South America, 102;
introduction of injurious species, 104, 106;
ravages of, 105;
tenacity of life in, 106;
the carnivorous, useful to man, 107;
destruction of, by fish, 108;
abundance of, in Northern Europe, 108;
destruction of, by birds, 109;
do. quadrupeds, 110;
do. reptiles, 110;
do not multiply in the forest, 291;
confine themselves to dead trees, 322.
Inundations, influence of the forest on, 223;
of the German Ocean, 334;
means for obviating, 384;
of 1856 in France, 393;
remedies against, 395;
legislative regulation of the woodlands in France for
prevention of, 396;
proposed basins of reception, 398;
do. in Peru and Spain, 400;
Rozet's plan for diminishing, 406.
Irrigation, remote date of in ancient nations, 366;
among Mexicans and Peruvians, 366;
its necessity in hot climates, 367;
in Europe, 367;
in Palestine, 368;
in Idumæa, 370;
Egypt, 371, 373;
quantity of water so applied, 376, 377;
extent of lands irrigated, 396;
effects of, 378;
on river supply, 380;
on human health, 381;
saline deposits from, in India and Egypt, 382;
effect of, on vegetable crops, 378;
on the soil, 379;
economic evils of, 379.
Islands, floating, in Holland and South America, 349, 351.
Ijssel river, Holland, 535.
Italy, effects of the denudation of its forests, 220;
political condition adverse to their preservation, 219;
beauty of its winter scenery, 314;
extent of irrigation in, 368;
atmospheric phenomena of Northern, 368.
Jupiter, satellites of, visible to the eye, 12.
Jutland, effects of felling the woods in, 150;
destruction of forests in, 279;
encroachments of the sea on, 491.
Kander river, Switzerland, artificial course of, 403.
Karst, the subterranean waters of, 536.
Kjökkenmöddinger in Denmark, 16;
their extent, 540.
Kohl, J. G., "the Herodotus of modern Europe," 340;
on dune sand, 475.
Labruguière, commune of, 208.
Læstadius, account of the Swedish Laplanders, 96.
Lakes, draining of, by steam hydraulic engines, 346;
natural process of filling up by aquatic vegetation, 349;
lowering of, in ancient and modern times, 353;
in Italy, 354;
in Switzerland, 356;
inconvenient consequences of, 356;
mountain, their disappearance, 357.
Landscape beauty, insensibility of the ancients to, 2;
of the oasis and the desert, 445.
Lava currents, diversion of their course, 544;
from Vesuvius, phenomena of, 545;
heat emitted by, 545.
Life, balance of animal and vegetable, 103.
Liimfjord, the, irruption of the sea into, 491;
aquatic vegetation of, 492;
original state of, 519.
Lion, an inhabitant of Europe, 85.
Lisbon, earthquake of, 544.
Locust, the, does not multiply in woods, 296;
tree and insect, 32.
Lombardy, statistics of irrigation in, 376.
Louis IX., of France, clemency of, 282.
Lower Alps, department of, ravages of torrents in, 246.
Lumber trade of Quebec, 271;
of United States, 1850-'60, 301.
Lungern, lake of, lowering of, 356.
Madagascar, gigantic bird of, 96;
the ai-ai of, 110.
Madder, early cultivation of, in Europe, 20.
Madeira, named from its forests, 129.
Maize, early cultivation of, law of its acclimation, 19;
native country of, 73.
Malta, transported soil of, 538;
salt works at, 540.
Man, reaction of, on nature, 8;
insufficiency of data, 9;
geographical influence of, 13;
physical revolutions wrought by, 14;
unpremeditated results of conscious action, 15;
ancient relics of, in old geological formations, 16;
mechanical effects of, on the earth's surface, 25;
destructiveness of, 35;
in animal life and inorganic nature, 36-39;
character of his action compared with that of brutes, 42;
subversive of the balance of nature, 43;
sometimes exercised for good, 44;
present limits to, 45;
transfer of vegetable life by, 59;
remains of, 76;
contemporary with the mammoth, 77;
agency in the extermination of birds, 96;
do. introduction of species, 98;
increase of insect life, 104;
introduction of new forms of do. by, 105;
destruction of fish by, 112, 120, 122;
extirpation of aquatic animals by, 119;
possible control of minute organisms, 125;
his first physical conquest, 135;
his action on land and the waters, 330;
possible geographical changes by, 517;
incidental effects of his action, 539;
illimitable and ever enduring do., 548.
Maremme of Tuscany, ancient and mediæval state of, 425;
extent of, 427;
inhabitants, 428;
improvement of, 429;
sedimentary deposits of, 425, 430.
Marine isthmuses, cutting of, 517;
its difficulties, 518;
sometimes done by nature, 519.
Marmato in Popayan, 205.
Marshes, climatic effects of draining, 358;
insalubrity of mixture of fresh and salt water in, 417.
Mechanic arts, illustration of their mutual interdependence, 307.
Medanos of the South American desert, 482.
Mediterranean Sea, tides of, 425;
sand dunes of, 467;
poor in organic life, 520.
Mella, the river, Italy, 248.
Meteorology, uncertainty and late rise of, 16, 22;
varying nomenclature of, 23;
precipitation and evaporation, 24.
Michigan, lake, sand dunes of, 467;
originally wooded, 487;
proposed diversion of its waters, 532.
Mining excavations, effects of, 545.
Minute organisms, their offices, 123;
universal diffusion and products of, 124, 127;
possible control of their agency by man, 125;
the coral insect, 125;
the diatomaceæ, 126.
Miramichi, great fire of, 28.
Mistral in France, 153.
Mississippi river, "cut offs" and their effect, 415;
precipitation in the valley of, 436;
projected canal to, 533.
Mountain slides, their cause, 265, 268;
their frequency in the Alps, 267.
Mountainous countries, their liability to physical degradation, 50.
Monte Testaccio, Rome, 541.
Moose deer, the American, rapid multiplication of, 130.
Mushrooms, poisonous, how to render harmless, 286.
Natural forces, accumulation of, 46;
resistance to, 542.
Nature, man's reaction on, 8;
observation of, 10;
stability of, 27, 34;
restoration of disturbed harmonies of, 35;
nothing small in, 548.
Naturalists, enthusiasm of, 99.
Netherlands, ancient inundations of, 334;
recovery of land by diking, 334;
the practice derived from the Romans, 335;
extent of land gained from the sea, 336;
do. lost by incursions of do., 337;
character of lands gained, 338;
natural process of recovery, 339;
grandeur of the dike system of, 340;
method of their construction in, 341;
modes of protection, 343;
various uses of, 343;
effect on the level of the land, 344;
drainage of do., 345;
primitive condition of, 351;
effects on the social, moral, and economic interests of the
people of, 351;
sand dunes of, 486;
encroachments of the sea on, 494;
artificial dunes in, 499;
protection of dunes in, 500;
removal of do., 509.
Nile, the river, valley of, 374;
its ancient state, 375;
inundations of, 385;
water delivery of, 387;
artificial mouths of, 402;
consequences of diking, 410, 413;
richness of its deposits, 411;
extent of do., 412;
mud banks caused by its deposits, 433;
sand dunes at its mouths, 468;
conduits for irrigation, 521;
proposed diversion of, 528;
not impossible, 529;
effects of, 530;
ceramic banks of, 541.
Northmen in New England, 60.
Nubians, Nile boats of the, 17.
Numbers, the frequent error in too definite statements of, 260;
oriental and Italian usage of, 261.
Oak, the English, early uses in the arts, 223;
"openings" of North America, 136.
Ohio, mounds of, 18;
remains of a primitive people in, 135, 138;
apple trees of, 22.
Old World, former populousness of, 4;
physical decay of, 3;
present desolation of, 5;
its causes, 5;
ancient climate of, 19;
physical restoration of, 47.
Olive tree, the wild, 74;
importance of, 312.
Orange tree known to the ancients, 64;
the wild, 74.
Orchids, fertilization of, by insects, 102.
Organic life embraced in modern geography, 57;
its geological agency, 75;
geographical importance of, 7;
bones and relics of, human and animal, 76.
Ostrich, the, diminution of its numbers, 97.
Ottaquechee river, Vermont, transporting power of, 253.
Otter, the American, voracity of, 120.
Oxen, agricultural uses of, in United States, 80.
Oyster, the, transplantation of, 118.
Palestine, ancient terrace culture and irrigation of, 369;
disastrous effects of its neglect, 370.
Palissy, Bernard, character of, 218;
plan for artificial springs, 447.
Paragrandini of Lombardy, 141.
Paramelle, the Abbé, on fountains, 437.
Peat beds, accidental burning of, 546;
-- mosses of Denmark, 32.
Pecora, river of the Maremma, its deposits, 425.
Peru, ancient progress in the arts, 366;
basins of reception in, 400.
Petra, in Idumæa, ancient irrigation at, 370.
Phosphorescence of the sea unknown to the ancients, 114.
Physical decay of the earth's surface, 3;
its causes, 5;
arrest of, in new countries, 48;
forms and formations predisposing to, 49.
Physical geography, study of recommended, 12;
restoration of the earth, 8;
importance and possibility of, 26;
of disturbed harmonies, 35;
of the Old World, 47.
Pine, the American, former ordinary dimensions of, 275;
how affected by the accidents of its growth, 306;
the maritime, on dune sands in France, 506;
the pitch, hardihood of, 273;
umbrella, the, most elegant of trees, 309, 313;
the white, rapidity of its growth, 274.
Pinus cembra of Switzerland, 309.
Pisciculture, its valuable results, 118.
Plants, cultivated, uncertain identity of ancient and modern, 19;
do. of wild and domestic species, 73;
changes of habit by domestication, 19;
geographical influence of, 58;
foreign, grown in United States, 61;
American, grown in Europe, 63;
modes of introduction, 64;
accidental do., 66;
power of accommodation of, 65;
how affected by transfer, 68;
tenacity of life in wild species, 69;
extirpation of, 70;
domestic origin of, 72;
species employed for protection of sand dunes, 500.
Pliny, the elder, theory of springs, 198, 216.
Po, river, ancient state of its basin, 255;
modern changes, 256;
its floods, tributaries, and deposits, 256-261, 405;
embankments of, 385, 404;
sediment of, 410;
age and consequences of its embankments, 411;
mean delivery of, 412;
_salti_ of, 415.
Poland, sand plains of, 514.
Poplar, the Lombardy, 68;
characterized, 313.
Potato, native country of, 73.
Prairies, conjectural origin of, 134.
Provence, physical structure of, 237;
ancient state of, 238;
destructive action of torrents on, 236;
Alps of, 245.
Prussia, sand dunes of, 485;
drifting of, 498;
measures for reclaiming of, 505.
Quadrupeds, number in United States, 79;
extirpation of, 84.
Quebec, high tides of, 271;
lumber trade of, 272.
Railways, scientific uses of, 53.
Rain water, its absorption and infiltration, 438, 439;
economizing its precipitation, 449.
Ravenna, cathedral of, 60;
pine woods of, 150.
Red Sea, richness of, in organic life, 320;
diversion of the Nile to, its effects, 530.
Reindeer, the, 83.
Reservoirs, geographic and climatic effects of, 258.
Reventlov's organization of dune economy in Denmark, 504;
a benefactor to his race, 515.
Rhine, river, proposed diversion of, 533.
Rice, cultivation of, 381.
Rivers, transporting power of, 252;
in Vermont, 253;
their origin, 262;
injury to their banks by lumbermen, 277;
conditions of their rise and fall, 278;
mutual action of rivers and valleys, 408;
effect of obstructions in, 409;
subterranean course of, 409;
confluences of, effect on the current below, 424;
sediment of, its extent, 547.
River beds, natural change of, 401;
artificial do. in Egypt, 402;
Italy and Switzerland, 403.
River deposits, 408;
of the Nile, 410;
the Po, 411;
the Tuscan rivers, 414.
River embankments, 384;
their use, 404;
disadvantages, 405;
transverse do., superiority of, 406;
effects of, 409.
River mouths, obstructions of, 430;
by sand banks, 431;
accelerated by man's influence, 432;
effect of tidal movements, 432.
Robin, the American, voracity of, 88.
Rock generally permeable by water, 265.
Roman empire, natural advantages of its territory, 1;
increased by intelligent labor, 2;
physical decay of, 3;
present desolation, 4;
caused by its despotism and oppression, 5.
Rozet's plan for diminishing inundations, 406.
Rude tribes, continuity of arts among, 17;
commerce of, 18;
relations to organic life, 39;
and to nature, 41.
Russia, diminution of forests in, 298;
effects of, on rivers and lakes, 299;
sand drifts of the steppes of, 514;
attempts to reclaim them, 515.
Sacramento City, California, effect of river dike at, 405.
Sand, its composition and origin, 452;
action of rivers, 453;
ancient deposits of, 454, 456;
amount of, carried to the Mediterranean, 455;
of Egypt, 458, 461;
movement of, by the wind, 459;
drifts of, from the sea, 461;
dangers of accumulation of, 463;
two forms of deposit, 463;
drifting of dune, 495.
Sand banks, aquatic, 468;
movement of, 469;
connect themselves with the coast, 490.
Sand dunes, how formed, 464;
utilization of, 465;
inland, of the South American desert, 482;
their peculiarities, 483;
age, character, and permanence of, 484;
naturally wooded, 486;
not noticed by ancient writers, 487;
management of, 488;
coast, sources of supply, 465;
law of their formation, 466, 471, 483;
of the Mediterranean, 467;
of Lake Michigan, 467;
of the Nile mouths, 468;
of America, 469;
of Western Europe, 470;
literature of, 471;
height of, 472;
humidity of, 473;
of Cape Cod, 487;
character of their sand, 474, 481;
concretion within, 476;
interior structure of, 477;
general form of, 478;
geological importance of, 479;
composition of sandstone, 481;
as barriers against the sea, 489;
in Western Europe, 490;
extent of, 507;
of Gascony, 496;
of Denmark, 497;
of Prussia, 497;
artificial formation of, in Holland, 499;
protection of, 500;
by vegetation, 501;
trees adapted to, 505;
removal of, 509.
Sand-dune vineyard of Cap Breton, 508.
Sand plains, mode of deposit, 464;
constituent parts, 464;
inland, of Europe, 509;
landes of Gascony, 511;
Belgium, 513;
Eastern Europe, 513;
advantages of reclaiming, 515;
private and public enterprise, 516.
Sand springs, 511.
Sandal wood extirpated in Juan Fernandez, 130.
Saros, projected canal of, 527.
Sawmills, action of their machinery more rapid by night, 278.
Schelk, the extirpation of, 85.
Schleswig-Holstein, encroachments of the sea on, 493.
Scientific observation, practical lessons of, 54-56.
Sea, the, exclusion of, by dikes, in Lincolnshire, 333;
encroachments of, 490;
coast, 491;
the Liimfjord, 491;
Schleswig-Holstein, 493;
Holland, 494;
France, 494.
Sea cow, Steller's, extirpation of, 119.
Seal, the, in Lake Champlain, 117;
voracity of, 120.
Seeds, vitality of, as preserved by the forest, 287, 289.
Seine river, ancient level of, 214;
affluents of, 435.
Ship building of the middle ages, Venice and Genoa, 218.
Siberia, ice ravine in, 158.
Sicily, stone weapons found in, 18;
sulphur mines of, 72;
olive oil crop of, 312.
Silkworm, introduction in South America, 105.
Sinai, Mt., rain torrent at, 441;
production of sand in peninsula of, 454;
garden of monastery at, 537.
Snakes, destructive to insects, 110;
tenacity of species, 111;
number of, in Palestine and Egypt, 111.
Snow, action of the woods on, 211;
experiments on, 212.
Soils, amount of thermoscopic action on various, 144;
mechanical effects of shaking in the Netherlands, 344;
effect of frost on, in United States, 344.
Solar heat, economic employment of, 47.
Solitary, the, extirpation of, 95.
Sound, transmission of, in still air, 165.
Springs, artificial, proposed by Palissy, 447;
by Babinet, 448.
Spain, neglect of forest culture in, 279.
Squirrel, the, destructiveness of, in forests, 34;
of Boston, 121.
St. Helena, flora of, 65;
destruction of its forests, 130.
Staffordshire, phenomena of vegetation in, 288.
Starlings, habits of, in Piedmont, 111.
Stork, the, geographical range of, 93;
anecdote of a, 99.
Subterranean waters, their origin, 434;
sources of supply, 435;
reservoirs and currents of, 438;
diffusion of, in the soil, 439;
importance, 440;
of the Karst, 535;
of Greece, 536.
Suez canal, the, danger from sand drifts, 461;
effect on the Mediterranean and Red Sea basins, 520.
Sugar cane, culture of, 62.
Sugar-maple tree, produce of, 169.
Summer dikes of Holland, 342.
Sunflowers, effect of plantations of, 154.
Swallow, the, popular superstitions respecting, 418.
Switzerland, ancient lacustrine habitations of, 16, 70, 83.
Sylt Island, sand dunes of, 474;
encroachments of the sea on, 493.
Sylviculture, best manuals of practice of, 304;
when and how profitable, 305;
its methods, 315;
the _taillis_ treatment, 315;
the _futaie_ do., 317;
beneficial effects of irrigation, 319;
exclusion of animals, 321;
removal of leaves, &c., 322;
topping and trimming, 324.
Taguataga Lake, Chili, 355.
Tea plant, the, cultivated in America, 62.
Temperature, general law of, 52.
Teredo, the general diffusion of, 107.
Termite, or white ant, ravages of, 107.
Teverone, cascade of, Tivoli, 402.
Timber, general superiority of cultivated, 305;
slow decay of, in forest, 322.
Tobacco an American plant, 68;
introduction in Hungary, 67.
Tocat, Asia Minor, oak woods of, 186.
Tomato, the, introduction to New England, 19.
Torricelli, successful plan for draining the Val di Chiana, 421.
Torrents, destructive action of, 231;
means of prevention, 233;
ravages of, in Southeastern France, 237;
Provence, 239;
Upper Alps, 240;
Lower Alps, 246;
action of, in elevating the beds of mainland streams, 249;
in excavating ravines, 250;
transporting power of, 251;
signs of, extinguished, 263;
crushing force of, 392.
Trees, as organisms, specific temperature of, 156;
moisture given out by, 158;
total influence on temperature, 159;
absorption of water by, 166;
flow of sap, 169;
absorption of moisture by foliage of, 172;
exhalation of do., 174;
consequent refrigeration, 175;
amount of ligneous products of, 173;
protection against avalanches afforded by, 269;
power of resisting the action of fire, 273;
American forest trees, 274;
their dimensions, 275;
change in relative proportions of height and diameter, 276;
comparative longevity of, 277;
European and American compared, 308;
species more numerous in America, 309;
Spenser's catalogue of, 308;
interchange of European and American species, 310;
species of Southern Europe and their extent, 312;
natural order of succession in, 323.
See _Forest_, _Woods_.
Trieste, proposed supply of water to, 536.
Trout, the American, 115, 117, 121.
Tuscany, rivers of, their deposits, 414;
physical restoration in, 416;
improvements in Val di Chiana, 417;
do. in the Maremma, 424.
Tyrolese rivers, elevation of their beds, 249.
Ubate, lakes of, New Granada, 204.
Undulation of water, 456.
United States, foreign plants grown in, 61;
weight of annual harvest in, 62;
number of quadrupeds in, 79;
of birds, 86;
effect of felling woods on its climate, 180;
forests of, 300;
instability of life in, 328.
Upper Alps, department of, ravages of torrents in, 240.
Urus, or auerochs, domesticated by man, 83;
extirpation of, 85.
Val de Lys, evidence of glacier action in, 252.
Vegetable life, transfer by man's action, 59.
Velino, cascade of, Tivoli, 402.
Vesuvius, vegetation on, 131;
eruption of February, 1851, 544.
Volcanic action, resistance to, 544;
matter, vegetation in, 131.
Volga river, proposed diversion of, 531.
Walcheren, formation of the island, 340.
Wallenstadt, lake of, 534.
Walnut tree, consumption of, for gun stocks, 296;
oil yielded by, 310.
Ward's cases for plants, 175.
Waste products, utilization of, 37.
Weeds common to Old and New World, 66;
extirpated in China, &c., 71.
Whale, the, food of, 113;
destruction of, 114.
Whale fishery, date of its commencement unknown, 112;
in the middle ages, 112;
American, 113.
Wheat, its asserted origin, 73;
introduction to America, 74.
Wild animals, number of, 84.
Wild organisms, vegetable and animal, tenacity of life in, 69.
Willow, the weeping, introduction in Europe, 64.
Wolf, increase of the, 84;
prevalence in forests of France, 296.
Wolf Spring, Soubey, 206.
Wood, increased demand for, 293;
ship building, railroads, &c., 294;
market price of, 294;
replaced by iron in the arts, 295;
means of increasing its durability, 295;
how affected by rapid growth, 306;
facilities for working, 307.
Woods, habitable earth originally covered by, 128;
conditions of their propagation, 131;
destructive agency of man and domestic animals, 132;
do not furnish food for man, 133;
first removal of, 134;
burning of, 136;
in Sweden and France, 137;
effect on the soil, 138;
destruction of, its effect, 139;
electrical influence of, 140;
chemical influence of, 142;
influence on temperature, 143;
absorbing and emitting surface of, 144;
in summer and winter, 147;
dead products of, 148;
as a shelter, 149;
in France, 149, 151;
New England, 149;
Italy and Jutland, 150;
as a protection against malaria, 154;
tend to mitigate extremes of temperature, 155.
See _Forest_, _Trees_.
Wood mosses and fungi, absorbent of moisture, 168.
Woodpecker, the, destroyer of insects, 109.
Yak, or Tartary ox, the, 83.
Yew tree, geographical range of, 70.
Zeeland, province, formation of, 339.
Zostera marina, 492.
Zuiderzee, proposed drainage of, 534;
means of, and geographical results, 535.
THE END.
* * * * *
FORSYTH'S "CICERO."
A New Life of Cicero.
BY WILLIAM FORSYTH, M. A., Q. C.
With Twenty Illustrations. 2 vols. crown octavo. Printed on tinted and
laid paper. Price, $5.00.
The object of this work is to exhibit Cicero not merely as a Statesman
and an Orator, but as he was at home in the relations of private life,
as a Husband, a Father, a Brother, and a Friend. His letters are full of
interesting details, which enable us to form a vivid idea of how the old
Romans lived 2,000 years ago; and the Biography embraces not only a
History of Events, as momentous as any in the annals of the world, but a
large amount of Anecdote and Gossip, which amused the generation that
witnessed the downfall of the Republic.
The _London Athenæuem_ says: "Mr. Forsyth has rightly aimed to set
before us a portrait of Cicero in the modern style of biography,
carefully gleaning from his extensive correspondence all those little
traits of character and habit which marked his private and domestic
life. These volumes form a very acceptable addition to the classic
library. The style is that of a scholar and a man of taste."
From the _Saturday Review_:--"Mr. Forsyth has discreetly told his story,
evenly and pleasantly supplied it with apt illustrations from modern
law, eloquence, and history, and brought Cicero as near to the present
time as the differences of age and manners warrant. * * * These volumes
we heartily recommend as both a useful and agreeable guide to the
writings and character of one who was next in intellectual and political
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political composition."
"A scholar without pedantry, and a Christian without cant, Mr. Forsyth
seems to have seized with praiseworthy tact the precise attitude which
it behoves a biographer to take when narrating the life, the personal
life, of Cicero. Mr. Forsyth produces what we venture to say will become
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"This book is a valuable contribution to our Standard Literature. It is
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of the veil which has hung over the scenes and actors of times so full
of ferment, and allows us to catch a glimpse of the stage upon which the
great drama was played."--_North American Review._
_Copies sent by mail, post paid, on receipt of price._
LORD DERBY'S "HOMER."
The Iliad of Homer.
RENDERED INTO ENGLISH BLANK VERSE BY EDWARD, EARL OF DERBY.
From the fifth London Edition.
Two volumes, royal octavo, on tinted paper. Price $7.50 per vol.
Extracts from Notices and Reviews from the English Quarterlies, &c.
"The merits of Lord Derby's translation may be summed up in one word:
"it is eminently attractive; it is instinct with life; it may be read
with fervent interest; it is immeasurably nearer than Pope to the text
of the original. * * * We think that Lord Derby's translation will not
only be read, but read over and over again. * * * Lord Derby has given
to England a version far more closely allied to the original, and
superior to any that has yet been attempted in the blank verse of our
language."--_Edinburgh Review, January 1865._
"As often as we return from even the best of them (other translations)
to the translation before us, we find ourselves in a purer atmosphere
of taste. We find more spirit, more tact in avoiding either trivial
or conceited phrases, and altogether a presence of merits, and an
absence of defects which continues, as we read, to lengthen more
and more the distance between Lord Derby and the foremost of his
competitors."--_London Quarterly Review, January, 1865._
"While the versification of Lord Derby is such as Pope himself would
have admired, his Iliad is in all other essentials superior to that of
his great rival. For the rest, if Pope is dethroned what remains? * * *
It is the Iliad we would place in the hands of English readers as the
truest counterpart of the original, the nearest existing approach to a
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"Among those curiosities of literature which are also its treasures,
Lord Derby's translation of Homer must occupy a very conspicuous
place. * * * Lord Derby's work is, on the whole, more remarkable for
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throughout, than for its special bursts of eloquence. It is uniformly
worthy of itself and its author."--_The Reader._
"Whatever may be the ultimate fate of this poem--whether it take
sufficient hold of the public mind to satisfy that demand for a
translation of Homer which we have alluded to, and thus become a
permanent classic of the language, or whether it give place to the still
more perfect production of some yet unknown poet--it must equally be
considered a splendid performance; and for the present we have no
hesitation in saying that it is by far the best representation of
Homer's Iliad in the English language."
AMERICAN NOTICES.
The _Publishers Circular_ says:--At the advanced age of sixty-five, the
Earl of Derby, leader of the Tory party in England, has published a
translation of Homer, in blank verse. Nearly all the London critics
unite in declaring, with _The Times_, "that it is by far the best
representation of Homer's 'Iliad' in the English language." His purpose
was to produce a translation, and not a paraphrase--fairly and honestly
giving the sense of every passage and of every line. Without doubt the
greatest of all living British orators, he has now shown high poetic
power as well as great scholarship.
From the _New York World_:--"The reader of English, who seeks to know
what Homer really was, and in what fashion he thought and felt and
wrote, will owe to Lord Derby his first honest opportunity of doing so.
The Earl's translation is devoid alike of pretension and of prettiness.
It is animated in movement, simple and representative to phraseology,
breezy in atmosphere, if we may so speak, and pervaded by a refinement
of taste which is as far removed from daintiness or effeminacy as can
well be imagined."
_Copies sent by mail, post paid, on receipt of price._
TRANSCRIBER'S NOTES:
1. Passages in italics are surrounded by _underscores_.
2. The original text includes Greek characters. For this text version
these letters have been replaced with transliterations.
3. Certain words use "oe" ligature in the original, indicated by [oe]
and [OE].
4. The letters with macron are represented within square braces with an
equals sign preceding it. For example, letter a with macron is indicated
by [=a].
5. In this text version, some of the references to appendix notes within
footnotes were incorrect which have been corrected. Also, errors found
in page references within Appendix have been corrected.
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