The Project Gutenberg EBook of North America, by Israel C. Russell
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Title: North America
Author: Israel C. Russell
Release Date: May 3, 2011 [EBook #36024]
Language: English
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Appletons' World Series
_THE REGIONS OF THE WORLD_
EDITED BY
H. J. MACKINDER, M.A.
_Reader in Geography in the
University of Oxford_
Each complete in One Volume, Large 8vo.
BRITAIN AND THE BRITISH SEAS
By the EDITOR
WESTERN EUROPE AND THE MEDITERRANEAN
By ELISÉE RECLUS
CENTRAL EUROPE
By JOSEPH PARTSCH, Ph.D.
SCANDINAVIA AND THE ARCTIC REGION
By Sir CLEMENTS R. MARKHAM, K.C.B.,
F.R.S., President Royal Geog. Soc.
THE RUSSIAN EMPIRE
By PRINCE KROPOTKIN
THE NEARER EAST
By D. G. HOGARTH, M.A.
AFRICA
By J. SCOTT KELTIE, LL.D., Sec. R. G. S.
INDIA
By Colonel Sir THOMAS HOLDICH, K.C.I.E.,
C.B., R.E.
THE FARTHER EAST
By ARCHIBALD LITTLE
NORTH AMERICA
By ISRAEL C. RUSSELL, LL.D.
SOUTH AMERICA
By JOHN C. BRANNER, LL.D.
AUSTRALASIA AND ANTARCTICA
By H. O. FORBES, LL.D.
[Illustration: FIG. 1.--North America.
From a photograph of a relief map by Victor and Cosmos Mindeleff. Scales
of original: Horizontal, 120 miles to 1 inch; vertical, 40,000 feet to 1
inch: proportion, 1:16.]
NORTH AMERICA
BY
ISRAEL C. RUSSELL
PROFESSOR OF GEOLOGY IN THE UNIVERSITY OF MICHIGAN
_With Maps and Diagrams_
[Illustration]
NEW YORK D. APPLETON AND COMPANY 1904
COPYRIGHT, 1904
BY D. APPLETON AND COMPANY
PREFACE
The aim of this book is to give a condensed and, I trust, readable
account of the leading facts concerning the North American continent
which, from the point of view of the geographer, seem most interesting
and instructive. The area of the continent is so vast and the diversity
among its various parts so great, however, that the completeness of
treatment which characterizes the preceding volumes in the series to
which it belongs could not be attempted. To obviate in a measure this
confessed shortcoming, there has been appended to each chapter a list of
books which will enable the reader to continue the studies outlined in
it.
A complete review of the geography of a continent should, as it seems to
me, be divided into two parts: first, a discussion of the natural
conditions, or physical geography, and, second, man's dependence on and
use of the natural resources, or economic geography. Each of these two
leading phases of the subject was embraced in the preliminary outline of
the present volume, but owing to a desire to make each chapter as
complete as practicable, and also on account of limitations as to space,
the treatment of the economic phases of geography has been necessarily
brief. But little more can be claimed for the book as finished than that
it is an attempt to describe some of the more prominent and attractive
aspects of the natural conditions pertaining to North America.
While writing this book I have become more and more impressed with the
incompleteness and inadequacy of the printed records relating to the
geography of the continent of which it treats. Extensive tracts,
particularly in the far North, have not been traversed by observant men,
vast areas throughout the continent have not been surveyed and mapped,
and even in the somewhat thickly inhabited portions of the more
enlightened countries there are large districts in reference to the
geography of which there is but little critical information available.
Under these conditions it seemed best to select typical examples of
various geographical features from the better known portions of the
continent to represent the conditions throughout the less thoroughly
explored domain in which they are situated, and at the same time serve
to illustrate the highly creditable advances made by American
geographers in definitely formulating the principles of physiography.
The book may, in a measure, be considered as an attempt to present in
popular form a report of progress concerning the study of the
geographical development of North America at the beginning of the
twentieth century.
I. C. R.
CONTENTS
CHAPTER PAGE
I. THE MARGIN OF THE CONTINENT 1
The continental shelf--The submarine topography of the
Caribbean region--Movements of the ocean
waters--Islands--Topography of the coast--Estuaries and
harbours.
II. THE TOPOGRAPHY OF THE LAND 60
Coastal plains and plateaus--The Atlantic mountains--The
continental basin--The Pacific mountains--The Antillean
mountains.
III. CLIMATE 173
The elements of climate--Climatic provinces--Secondary
disturbances of the atmosphere--Evaporation.
IV. PLANT LIFE 215
The forests--Prairies, treeless plains, and
plateaus--The treeless mountain tops.
V. ANIMAL LIFE 258
General principles of geographical
distribution--Life-regions and life-zones--The
mammals--Some representative mammals--The birds.
VI. GEOLOGY 299
The growth of the continent--The rocks of which the
continent is composed--The concentration of mineral
substances.
VII. THE ABORIGINES 355
The Eskimos--The Indians.
VIII. POLITICAL GEOGRAPHY 408
Classification of boundaries--Political
control--Population in 1900.
INDEX 427
LIST OF ILLUSTRATIONS
COLOURED MAPS
PLATE PAGE
I. Orographical features 25
II. Mean annual rainfall and temperature 173
III. Climate and life provinces 185
IV. Leading geological features 306
V. Pleistocene glacial deposits 315
VI. Linguistic stocks of Indians North of Mexico 370
VII. Distribution of governments 410
VIII. Characteristic vegetation 418
OTHER ILLUSTRATIONS
FIG. PAGE
1. Relief map of North America _Frontispiece_
2. Profile of a continental shelf 2
3. Map of Gulf of Mexico and the Caribbean region,
showing topography of the sea-floor 17
4. Co-tidal lines 29
5. Profile of sea-cliff and cut-and-built terrace 33
6. Map of a portion of the Atlantic coast of the
United States 35
7. Map of Mobile Bay 36
8. Map of Cape Cod 37
9. Map of the coast of Texas 39
10. Map of a portion of the coast of Maine 45
11. Map of the coast of southeastern Alaska 47
12. Map of the delta of the Mississippi 53
13. Map giving the names of the larger physiographic
divisions of North America 61
14. Altitude map of North America 65
15. Map of the Appalachian Mountains 74
16. Section of anticlinal valleys and synclinal
mountains 78
17. Profile showing relation of ancient peneplains
in the Appalachians 81
18. Section through the Black Hills of Dakota 117
19. Sketch of the Grand Cañon of the Colorado River 134
20. Map of the Great Basin 137
21. Map of Crater Lake, Oregon 153
22. Mount Rainier, Washington 154
23. Map of Puget Sound 161
24. Map showing isobars for January and July 175
25. Ice-palace, Montreal 199
26. Map showing tracks of West Indian hurricanes 209
27. Map showing depth of evaporation
in the United States 212
28. Map showing distribution of forests 215
29. Douglas firs, Vancouver 241
30. View in redwood forest of California, from
photograph by U. S. Bureau of Forestry 242
31. Bison at Silver Heights, Winnipeg 275
32. Map showing range of bison 276
33. Maps showing the growth of the North American
continent 303
34. Map showing the distribution of coal-fields 336
35. Ideal section through an oil and gas
pool beneath an anticlinal 339
36. Lodge or tepee of Blackfoot
Indians, Manitoba 387
37. Panorama of Uxmal, Yucatan 390
38. Pointed arches in Central American ruins 393
39. Carved stonework, Uxmal, Yucatan 394
NORTH AMERICA
CHAPTER I
THE MARGIN OF THE CONTINENT--THE
CONTINENTAL SHELF
In beginning the study of the physical geography of North America, one
of the first facts to claim attention is that the true continental
border is in general many miles seaward from the present margin of the
land. The boundary of our field of study is defined with considerable
accuracy by a line drawn on the bottom of the sea adjacent to the
present coast-line of the continent so as to pass through all points
where the soundings show a depth of 100 fathoms of water. This
100-fathom contour in the topography of the sea-floor chances to
coincide in a general way with the outline of the submerged border of
the continent; landward from it the bottom rises with a gentle slope,
while seaward the descent is usually steep down to a depth of 2,000 or
more fathoms.
A gently sloping shelf-like border surrounds the deep central basin of
the Gulf of Mexico (Fig. 3). To the west and north of Yucatan and west
of Florida the shelf is from 140 to 160 miles broad, with a surface
slope towards the centre of the Gulf of less than 6 feet to a mile--a
slope so gentle that were the surface of the shelf exposed to view, no
eye could distinguish it from a perfect plain. The deepest sounding yet
obtained in the central part of the Gulf, approximately midway between
Yucatan and Florida, shows a depth of 2,119 fathoms. The remarkable fact
is that the slope from the 100-fathom line to the bottom of the central
basin of the Gulf is precipitous. In two places on the border of
the Yucatan bank a descent of about 8,500 feet occurs within a
horizontal distance of 15 or 20 miles.
On the east side of the southern extremity of Florida, and again on the
eastern shore of Yucatan, the continental shelf is only about 5 miles
broad; these are the nearest approaches of the present land to the
actual border of the continent to be found on the Atlantic coast. The
explanation of these exceptional conditions is that both Florida and
Yucatan are portions of the continental shelf which have been raised so
as to form low emerged plains.
From Cape Hatteras northward to the extremity of the Newfoundland Banks
the shelf increases gradually in breadth from about 15 miles in the
region of the Carolinas to over 100 miles off the coast of Maine. The
outer border of the shelf is an irregular curving line. Opposite the
coast of Massachusetts and Maine an extension of the Atlantic basin
reaches within 15 or 20 miles of the present margin of the land. The
manner in which the low plain fringing the eastern border of the United
States passes beneath the waters of the Atlantic and becomes a
continental shelf is illustrated by Fig. 2.
[Illustration: FIG. 2.--Ideal profile through a continental shelf.]
Southeast of Newfoundland the continental shelf has an irregular
surface, marked by shoals and depressions, and furnishes the most
valuable fishing-banks in the world. The 100-fathom curve is there over
500 miles from the coast. This is the broadest portion of the
continental shelf now known on the Atlantic border of the continent.
Northward of Newfoundland the Atlantic basin extends far into Davis
Strait and Baffin Bay, and then its border swings outward about
Greenland, but its true margin is there but imperfectly known.
To the north of the arctic coast of North America, as is suggested in
part by the soundings made by Nansen, the submerged margin of the
continent is probably broad and presents a steep escarpment to the
arctic basin, but the outline of the true continent, as in the case of
the present land extension in that direction, is unknown.
Soundings to the north of Cape Lisburne, on the northwest coast of
Alaska, show that the 100-fathom curve is there over 200 miles from
land. The exceptionally shallow sea covering this portion of the shelf
continues westward to the coast of Asia, and southward through Bering
Strait, so as to embrace the eastern portion of Bering Sea. The
continental mass of North America is thus directly connected with the
continental mass of Asia. A rise of the bottom of less than 200 feet in
Bering Strait would bring about a land connection between the Old and
the New World. This, as will appear later, is a most significant fact to
students of geography and geology.
On the Pacific coast of North America the continental shelf is
throughout much narrower than its average breadth on the Atlantic side
of the continent, and is also more deeply submerged on its seaward
border. The broad platform beneath the northern and eastern portions of
Bering Sea--from which rise the low islands, St. Lawrence, St. Matthew,
Nunivak, and the Pribilof group, now separated by water from 25 to 35
fathoms deep--extends to the south of the more easterly of the Aleutian
Islands, and is prolonged eastward along the south border of Alaska,
where the 100-fathom curve is from 10 to 20 miles from the coast-line,
and approaches still nearer the land in the neighbourhood of the islands
of southeastern Alaska and British Columbia. The shelf is narrow but
well defined along the coasts of Washington and Oregon. Adjacent to
California, Mexico, and Central America, its outer margin is barely 10
miles from land. Throughout the entire distance from the Aleutian
Islands to Panama the outer border of the shelf is in general well
defined, and its seaward escarpment descends abruptly to the floor of
the vast Pacific basin, where the sounding-line shows depths of
from 2,000 to 3,000 fathoms.
Could the waters of the sea be removed and North America viewed from a
distance, in the manner we are enabled to examine the surface features
of the moon through a powerful telescope, an observer would behold a
great plateau, having the present well-known triangular shape of the
continent, rising boldly between the Atlantic and the Pacific basins.
The surface of the plateau would be rough, in comparison with the
generally smooth contours of the adjacent troughs, but even the highest
mountains would be less in elevation above its general surface than the
crests of its bordering escarpments above the adjacent depressions. The
mountain-peaks when illuminated by the sun would appear as points of
light with long, tapering morning and evening shadows, and the east and
west plateau-borders would be strongly drawn bands of light or shadow,
according to the time of day, 6,000 or 8,000 miles in length. The
Bermuda, Hawaiian, and other islands now rising above the surface of the
deep sea would stand on its desiccated floor as isolated, gigantic
mountains--"Bermuda mountain" with an elevation of 15,000 feet, and the
Hawaiian group of peaks with a culminating point of light 30,000 feet
above the surrounding plain. The bordering slopes of the "North American
plateau" and its slightly bevelled margin forming the present
continental shelf would be lacking in details, and appear as a vast,
smooth, curving belt of light or shadow, in striking contrast to the
roughened surface now above water.
The North American continent is not exceptional in being partially
submerged at the present time. Similar conditions occur about the
margins of other continents which, as is well known, are fringed with
broad submarine terraces built in part of their own _débris_. In fact,
every large land mass on the earth under existing climatic conditions
and present distribution of life, if it remained moderately stable for a
sufficient length of time, would have a submarine shelf built about its
borders.
_Of what is the Continental Shelf Composed?_--The rocks forming the
present land surface of North America extend seaward from the existing
shores and constitute the basal portions of the continental shelf, thus
suggesting that the submerged platform is due, in part at least, to
shore erosion--the waves having eaten into the land so as to make a
terrace. That this is not the true explanation, however, may be shown in
several ways.
The superficial covering which gives the continental shelf its smooth
contours is composed largely of sediments such as rivers bring from the
land. This material is coarsest and in greatest abundance near shore and
decreases both in the size of the particles composing it and in
abundance towards the seaward borders of the shelf. The wash from the
land is mostly deposited within a few miles of the coast-line and, as
has been shown by dredging, is seldom carried, even under the most
favourable conditions, more than about 100 miles seaward. Supplementing
the fragmental material derived from the land, and increasing in
thickness towards the seaward margin of the continental
shelf--coincident with the increase in depth of the water--is a deposit
of light-coloured calcareous mud or ooze, formed of the hard parts of
animals and plants which live in the waters of the sea. The organisms
which supply this material are in the main microscopic and live
especially in the warmer seas in countless myriads. Their dead shells or
cases fall to the sea-floor in a constant shower, much as the snow falls
from the air, but continuously year after year and century after
century. This descent of the hard parts of organisms, both calcareous
and siliceous, from the waters of the sea has led to the accumulation of
a sheet of slimy sediment over almost the entire sea-bottom. How thick
this layer is we have no means of knowing, but it is probably many
hundreds of feet.
The organic _débris_ falling on the continental shelf descends through
only a few hundred feet of water and is but little affected by its
solvent action. The great number of organisms, such as the Foraminifera
which secrete calcareous tests or "shells" causes the slime on the
continental shelves to be calcareous and in the condition to form
limestone if cemented or subjected to sufficient pressure. In the deep
sea, where the hard parts of dead organisms fall through many thousands
of feet of water, their more soluble portions are removed and the bottom
is covered throughout vast areas with a pinkish clay composed of the
more insoluble residue of the calcareous shells and the cases of
silica-secreting animals and plants.
The continental shelves are, in general, within the influences of ocean
currents, and fine _débris_, as we seem justified in concluding, is
removed from their surfaces, carried beyond their margins, and deposited
on their seaward slopes. The shelves are thus built outward and are
largely constructional topographic forms. Their outer slopes, where best
defined, represent about the "angle of repose" in water of the fine
material of which they are composed. These slopes are in several regions
so precipitous that they probably would not retain their present forms,
but descend in landslides, should the restraining pressure of the
sea-water be removed.
In certain favoured regions, as about the southern extremity of Florida,
over an extensive area in the West Indies, and on both sides of Central
America, the conditions favour the growth of reef-building coral-polyps,
and portions of the continental shelf in that region are covered with an
irregular layer of living coral and dead coral rock. The importance of
this resistant superficial layer on the minor features of the relief of
the submarine banks, etc., needs to be considered in studying the
secondary topographic features of many portions of the floor of shallow
tropical seas.
In addition to the _débris_ from the land and the rain of the hard parts
of organisms from the water covering the continental shelf there is in
northern regions a third but less important source of material furnished
by floating ice. About the northern shores of America sea ice forms in
winter, some of which is frozen fast to boulders and stones in shallow
water, and when this ice-foot, as it is termed, is adjacent to steep
cliffs, rock _débris_ falls upon it. When the ice becomes broken
into cakes in the spring-time or during storms, it floats away, under
the influence of the winds and currents, and as it melts drops its
freight on the floor of the sea. This shore ice seldom travels far, and
is probably not an important factor in the building of continental
shelves. Of greater interest are the bergs derived from glaciers,
especially in Greenland, many of which contain hundreds of thousands and
even millions of cubic feet of ice and travel hundreds of miles before
melting. In some instances these bergs carry with them rock masses, mud,
etc., derived from the land over which their parent glaciers flowed, and
as they melt, distribute this material over the sea-floor. The greater
portion of this ice-carried freight derived from Greenland is dropped on
the continental shelf, and not infrequently reaches the latitude of
Halifax, and even journeys farther south. This berg-carried _débris_ is
mainly deposited on the continental shelf, for the reason that the cold
currents which bring the bergs southward follow the coast in a general
way, and are bordered on their seaward margins by warmer currents
flowing northward. To the north of Nova Scotia the additions of material
to the continental shelf through the agency of bergs is considerable in
the aggregate, and as the process has been in operation for thousands of
years, the banks or shoals in the sea off the Newfoundland coast are due
in part to this cause.
Ice-carried _débris_ forms an important source of material for the
building of the continental shelf from New England northward and
westward about the shores of North America, including Greenland, to
Bering Sea, and to a less extent on the south coast of Alaska, where
many comparatively small bergs are set afloat by glaciers which reach
tide-water. Supplementing the distribution of _débris_ over the
continental shelf by shore ice and bergs, is the similar work carried on
by the ice discharged into the sea by northern rivers, such as the St.
Lawrence, Mackenzie, and the Yukon.
During the glacial epoch great ice-sheets like those now discharging
bergs along the Greenland coast, but vastly larger, entered the
Atlantic all the way from New York to the Arctic Ocean, and along the
Pacific coast from the Aleutian Islands to the State of Washington.
During certain periods of this time of intense glaciation great
additions of ice-borne _débris_ must have been made to the continental
shelf. The banks to the east of Newfoundland and other similar shoals as
far south as Nantucket are probably due in large part to the _débris_
deposited by the glaciers which formerly entered the sea in that region.
It is of interest in this connection to note that the glaciers, even at
the time of their greatest expansion, could not have extended beyond the
seaward margin of the continental shelf, for the reason that on passing
that boundary and entering deep water they must have broken off and
given origin to bergs.
_Submerged River Channels._--One of the most interesting features in
connection with the continental shelf bordering North America is that
its generally plane surface is trenched in several places by cañon-like
depressions similar to the narrow steep-sided valleys which streams
sometimes cut in the surfaces of plateaus. This suggestion that the
surface of the continental shelf is crossed by stream-cut channels is
supported by the fact that several such depressions, leading seaward
from the present mouths of large rivers, have been discovered by the
sounding-line. The best known example occurs off the mouth of the Hudson
and has been traced from New York Bay about 120 miles seaward to the
edge of the continental shelf. It is deepest and best defined on the
outer portion of the submerged plateau, where for a distance of 23
miles, beginning 97 miles from Sandy Hook, it has an average width of 3
miles and a maximum depth of about 2,500 feet below the surface of the
bordering submarine plain, which has 20 fathoms of water over it. This
cañon opens out in the seaward face of the plateau and forms a deep
notch in the generally uniform crest-line of that escarpment. Farther
"up-stream," so to speak, the channel narrows to a mile and a quarter,
with some irregularities in depth, and near Sandy Hook it is not
apparent, owing to the amount of _débris_, largely sand, swept into
it by shore currents. This evidence, strengthened by the fact that the
true rock-cut valley of the Hudson as far as Troy is filled with clay
and sand to a considerable but unknown depth, is abundant proof that the
land was formerly higher than at present by at least 3,000 feet, and
that the now submerged continental shelf off Long Island was then a
plain above water, across which the ancient Hudson was extended. The
river flowed across this plain for a sufficient length of time to
excavate a cañon over 2,500 feet deep and 3 miles wide from crest to
crest of its walls in its seaward portion. This submerged channel has
the characteristics of a young, stream-cut valley and suggests that the
plain across which it flowed to the eastward of Long Island was a
submerged continental shelf previous to being upraised so as to be
trenched by the Hudson.
The evidence as to changes in the elevation of the Atlantic coast
furnished by the submerged valley of the Hudson does not stand alone.
Similar but less well-defined channels have been discovered by soundings
off the mouths of the Delaware and the Susquehanna, while the most
remarkable instance of all is furnished by the submerged valley of the
St. Lawrence, which has been traced through the Gulf of St. Lawrence and
out to the brink of the submerged continental escarpment some 200 miles
eastward of Nova Scotia. The tide now rises and falls in the St.
Lawrence to within a few miles of Montreal; that is, the "Greater St.
Lawrence" has lost about 1,000 miles of its length owing to a downward
movement of the land.
Evidence of the nature just considered is lacking, or, more correctly,
surveys and soundings which would perhaps reveal the presence of
submerged river channels have not been made about the shores of the more
northerly portion of the continent, but instructive results in this
connection are to be expected when that region is thoroughly studied.
On the Pacific coast several transverse channels in the continental
shelf, similar to the submerged valleys of the Hudson, have been
discovered by soundings, some of which are thought to be true
stream-cut valleys; others, however, start from the coast where there
are no rivers entering, and may be due to other and as yet unknown
causes.
An exceptional feature in the geography of the Pacific coast to the
south of the United States-Canadian boundary is furnished by the islands
off the southern portion of California. These islands, of which Santa
Rosa, Santa Cruz, Santa Catalina, and San Clemente are the most
important, rise from water that is 300 or more fathoms deep to a height
of from a few hundred to about 2,000 feet above the present sea-level.
These islands are the summit portions of mountains similar to those
which give a characteristic relief to southern California. One feature
concerning the islands referred to which is of interest in connection
with the study of the continental shelf is the presence on them of
numerous terraces. These occur on a series of level, step-like areas,
which sweep about the slopes of the islands, in a general way parallel
to the present shore-line, and are records of an upward movement of the
land. The highest well-defined terrace on San Clemente occurs at an
elevation of 1,320 feet, but there are less distinct beach-lines up to
1,500 feet above the present sea-level. The evidence of movements of the
land along the Pacific border of the continent might be multiplied, but
enough has been stated to show that the western border of North America,
like its eastern portion, is subject to fluctuation in reference to the
level of the sea. The line which marks the passage of the solid earth
beneath the waters of the sea is ever changing, owing to movements in
the earth's crust. It is ever changing, also, owing to the action of
waves and currents on the ocean's shores and other causes.
_Life on the Continental Shelf._--No attempt need be made here to give
an accurate description of the plants and animals which find a congenial
home on the continental shelf. One needs, however, to have in mind a
general idea of the wonderful abundance and variety of organic forms in
the shallow waters adjacent to the continent to fully appreciate the
changes in the relief of the ocean-floor, in which they play a
leading part, and also the vast economic importance of these marine
harvest-fields and pastures, as they may be termed.
The continental shelf fringing North America reaches from within 500
miles of the equator to probably a less distance of the north pole. Its
length following its broader curves is in the neighbourhood of 25,000
miles, and its average width is not far from 50 miles; its area is
therefore something like 1,000,000 square miles. On account of the vast
extent of this submarine plain and its great range in latitude, the
conditions influencing the lives of the plants and animals inhabiting
its surface or living in the waters covering it vary from place to place
between wide extremes. The waters resting on it have a mean annual
surface temperature of from 70° to 80° F. at the south, and about 32° F.
at the north. In places great rivers and the turbid waters from glaciers
bring in sediments and form muddy deposits; at other localities the
currents, as in the path of the Gulf Stream off the Carolina coast,
sweep the bottom clear of all light _débris_; and again bare rocks of
limited extent are exposed. The depth of the water resting on the shelf
varies through all gradations down to 100 fathoms. At the south the
hours of light and darkness are approximately equal each day, but at the
north there are six months of sunlight and six months of darkness each
year. Still other variations, as of strength of currents, salinity,
etc., exert an influence in this realm and lead to great diversity in
its living organisms. Throughout its entire extent, however, the
continental shelf abounds in both plant and animal life.
The plant life of the sea, as has been shown in recent years by the use
of the dredge and net, is most abundant at the surface and is
practically absent at the bottom where the water is over 100 fathoms
deep. The animals of the sea, like those of the land, are dependent
primarily on plants for their food. By far the most abundant supply of
food plants in the sea is furnished by minute algæ, which float free in
its water. Below a depth of about 100 fathoms algæ are absent because of
lack of light, and all the deep-sea animals are believed to be
carnivorous. For these reasons the comparatively shallow waters
adjacent to the land and mainly covering the continental shelf are the
most favourably circumstanced of any portion of the sea for the support
of a teeming fauna.
On the continental shelf of North America, especially to the south of
Cape Cod on the Atlantic and south of the Aleutian Islands on the
Pacific coast, there is a warm temperature, light penetrates to the
bottom except in the unfavourable and fortunately restricted areas of
muddy water, and motion of the waters produced by currents and the
pulsations of waves is present. These several favourable conditions
permit of an exuberance of life such as is unknown to persons who
confine their attention to the study of land areas.
We may safely say, in the words of Alexander Agassiz, that the abundance
of life in the many favoured localities of the ocean far surpasses that
of the richest terrestrial faunal districts. The most thickly populated
tropical jungle does not compare in wealth of animal or vegetable life
with certain portions of the continental shelf on the western border of
the Gulf Stream. In this connection we may also cite Humboldt, who
before the marvellous revelations in reference to the life of the sea
made by recent dredging expeditions wrote: "Upon surfaces less varied
than we find on continents, the sea contains in its bosom an exuberance
of life of which no other portion of the globe could give us an idea."
The distribution of life in the sea is analogous to the distribution of
life on land, but in a reverse direction with reference to sea-level. A
traveller passing from the tropical plains of eastern Mexico and
ascending Orizaba, for example, crosses successive belts of vegetation,
each with its indigenous animals, but merging one with another so as to
make a gradation in the luxuriance of the flora and the abundance of
animal life from the wonderfully rich plains adjacent to the Gulf coast
to the snow-capped mountain top. In the sea, the tropical plains with
their tangled vegetation and plentiful animal life are represented by
the still more uniform plain forming the submerged continental
shelf with its strange forests of flowerless plants, the seaweeds. These
submarine jungles shelter hosts of animal species, many of which swarm
in countless myriads. This life embraces all grades of invertebrates,
such as the microscopic protozoa, sponges, radiate animals like the
coral-polyps, starfishes, sea-urchins, etc., and crustaceans in vast
variety, and, among vertebrates, includes fishes, reptiles, and mammals.
Even birds might be included in this category, since many of them are
more at home on the sea than on the land.
The struggle for food among this multitude is intense. As with many
animals on the land, adaptive coloration is here a means of escape from
enemies, and many of the animals assume the brilliant hues of the
surrounding vegetation. The water is less transparent than air, and in
the deep sea it is always night. Counteracting to some extent this
diminution or absence of sunlight, many marine animals are luminous and
shine with phosphorescent light of many different tints. This property
is shared also by the animals of the sunny, shallow sea as well as by
those always living in the cold midnight of the great deep and in the
polar oceans.
The luxuriant vegetation, both attached and floating, and varying from
giant kelp, scores of feet in length, to microscopic algæ which an
amoeba might encompass, clothes the surface of the continental shelf
except in unfavourable localities or is carried here and there by the
currents moving over it, but has its lower limit at about the 100-fathom
line. This inferior limit of marine vegetation is probably more
definitely defined than the superior limit of land plants on snow-capped
mountains. All attached seaweeds are confined to the shallow seas, but
floating kelp, like the well-known Gulf weed or sargasso, which collects
in the eddies of the sea currents and forms more or less mythical
floating islands, is widely distributed, as are also many kinds of
minute algæ which thrive in the upper 100 fathoms of the open ocean in
all latitudes. The primary source of food for the hungry millions of
marine animals, excepting the comparatively small quantity brought
by rivers or blown from the land, is supplied by the marine algæ, and
mainly by the minute forms which float in the water.
So much space has just been given to the marvellous luxuriance of life
on the southern portion of the great shelf surrounding North America
that the reader may perhaps think the cold northern oceans are even more
lifeless and desolate than their adjacent shores. This, however, is not
the case.
Northward along the continental shelf, with decrease in the strength of
the sunlight, the plants and animals lose much of the brilliancy which
characterizes many of the denizens of southern waters, and in general
assume more subdued colours in harmony with the prevailing gray of their
surroundings. The great diversity of animal life to be found in shallow
tropical seas decreases as one traces the continental shelf northward,
but even in the Arctic Ocean adjacent to the land invertebrate life
literally swarms, although the number of species, genera, etc., is
comparatively limited. Seaweeds are not absent from the Arctic Ocean,
although its shores, owing to the destructive action of ice, usually
seem exceedingly barren, and the lower or smaller forms of algæ float in
the waters in abundance. Food sufficient for an extensive fauna is thus
supplied, and where food is plentiful animals are present also, no
matter what the mean annual temperature may be.
The life of the Arctic Ocean has been but inadequately studied, but
enough is known concerning it to show that a promising field there
awaits the naturalist. On the continental shelf off Point Barrow, the
most northern portion of the arctic shore of Alaska (latitude 71° 23'),
180 species of marine invertebrates have been collected. Of these, the
molluscs numbered 61 species; the crustaceans, 44 species; the worms, 20
species; and the echinoderms (sea-urchins, starfish, etc.), 17 species.
Nearly all of the Arctic Ocean adjacent to the coast of America is as
yet unexplored, and we have therefore no direct testimony as to its
flora and fauna. We may reasonably assume, however, that the life is
there practically the same as in the waters of similar depth to
the north of Eurasia. Nordenskiöld, in his narrative of the voyage of
the Vega, speaks of decapods, worms, mussels, crustacea, and asteroids
which crawled in myriads over the beds of clay and sand at the bottom of
the Kara Sea. A detailed account is given of one unusually successful
haul of the trawl when it brought up large asteroids, sponges, crinoids,
holothuria, a gigantic spider, masses of worms, crustacea, etc. This was
the most abundant yield of the trawl-net at any one time during the
voyage of the Vega on the north coast of Asia, and that, too, from the
sea off the northern extremity of the continent. The temperature of the
water at the surface was from zero to -1.4° C. (32° to 29.48° F.), and
at the bottom from -1.4° to 1.6° C. (29.48° to 34.88° F.). In this
connection the same distinguished naturalist remarks: "It is singular
that a temperature under the freezing-point of pure water should be
advantageous for the development of an animal life so extremely rich as
that which is found here, and that this animal life should not suffer
any harm from the complete darkness which during the greater portion of
the year prevails at the bottom of the ice-covered sea."
To persons who have never visited the far north the statements that
travellers in those regions give in reference to the abundance of life
in the sea seems scarcely to be credited. The assertion, however, that
comparing equal areas in the most populous tropical sea and in portions
of the Arctic Ocean, the amount of life, or the tons of living animal
matter per square mile in the two regions, would be in favour of the
northern station is probably true. In addition to the direct evidence
indicated above as to the prolific invertebrate life of the cold waters
of the north, we have still more impressive testimony from the vast
numbers of birds and large-sized mammals which subsist on this
abundance, or feed on fishes, which in turn obtain their subsistence
from the invertebrate realm.
Every rocky island and headland at the north is a breeding-place for
sea-birds. They are to be numbered by millions, yet their daily food is
gathered from the surface of the sea. The seals live in large
numbers about all the arctic shore, and the walruses, each individual
weighing about a ton, occur in herds; while whales and narwhals inhabit
the same waters. The presence of such numbers of large mammals is proof
that the life on which they subsist is abundant.
THE SUBMARINE TOPOGRAPHY OF THE CARIBBEAN REGION
The studies which have given to the world so much information concerning
the continental shelf surrounding the main body of North America have
been continued, or, perhaps more properly, were initiated, in the West
Indian waters. For this important work we are indebted mainly to the
United States Coast and Geodetic Survey and the United States Fish
Commission. The work of officers of the United States Navy in charge of
Coast Survey and Fish Commission vessels, in making accurate
measurements of depths, temperatures, strength and direction of
currents, character of bottom, etc., has, in some instances, been
commemorated on maps of the sea-floor by such names as Brownson Deep,
Sigsbee Deep, Bartlett Deep, etc. The routine survey work referred to
has been supplemented and extended by the labours of Louis Agassiz, L.
F. Pourtales, Alexander Agassiz, and others in studying the life in the
sea, the origin and history of the material forming the sea-bottom, and
the nature of the shelves, banks, deeps, etc., which give diversity to
its topography.
The continental shelf bordering Florida on the east is separated from a
similar submarine embankment surrounding the Bahama Islands by a channel
56 miles wide and from 200 to 500 fathoms deep (Fig. 3).
This channel when followed northward becomes shallower and broader, and
opposite the Carolina coast is no longer discernible in the relief of
the broad continental shelf. The Gulf Stream flows northward through
this Florida channel, as it is termed, with a current of from 2 to 6
miles per hour. These conditions are such as to suggest that the channel
referred to has in part been excavated by the Gulf Stream.
[Illustration: FIG. 3.--Gulf of Mexico and the Caribbean region:
topography of sea-floor. The first contour line from the land indicates
a depth of 600 feet--the outer margin of the continental shelf. Contour
interval below the 600-foot curve, 3,000 feet. After R. T. Hill.]
The Great Bahama Bank, from which rise the low coral-built Andros
Islands and a large number of crags and rocks, measures about 360
geographical miles from southeast to northwest, and has a width of
approximately 200 geographical miles. Throughout its entire submerged
portion the water is less than 100, and over much of the area less than
10 fathoms deep. It is invaded and given an irregular shape, however, by
a "tongue of the ocean" which curves in from the northward, in which
soundings of from 700 to 1,000 fathoms have been obtained. To the north
of the Great Bahama Bank, and separated from it by water nearly 2,000
fathoms deep, is the Little Bahama Bank, measuring 50 by 150
geographical miles, from which rises the low islands known as Great
Bahama, Great Abaco, and a multitude of islets and crags, while beneath
the water, as is the case also on the greater submarine plateau to the
south, there are numerous shoals. Southeast from the Great Bahama Bank,
and in a general view to be classed with it, are several other shallow
areas in the sea, of similar character, and with numerous islands and
reefs rising from them. The southeastern terminus of this series of
plateaus, the surfaces of which have been built up practically to the
level of the surface of the sea, is the Navidad Bank, situated about 50
miles to the north of the eastern end of the island of Santo Domingo
(Haiti) and forms the west border of Brownson Deep. The length of the
series of banks to the north of the Greater Antilles is about 800, and
its average width 120 geographical miles.
The unevenness of the surface of the Bahama Banks (and the same is true
also of the southern portion of Florida, the Yucatan peninsula, and of
nearly all of the submarine plateaus or banks in West India waters) is
largely due to the coral reefs and the coral rock formed on them. While
the outer portion of the continental shelf, in most instances, is formed
of soft, unconsolidated calcareous mud or ooze, in the tropical seas,
where the depth, clearness of the water, etc., are favourable,
reef-building coral-polyps become attached and form massive corals. The
growth of these corals is irregular, and the surface of the plateaus
where they are attached becomes roughened. There is a delicate
adjustment between the growth of reef-building corals and strength of
current, freedom of exposure to the waves, etc., and they flourish in
certain localities, as on the windward border of islands, and die at
other localities. The growth of coral "heads" and reefs changes the
direction of currents, and the spaces of soft ooze and dead coral
between the localities most favourable for coral growth are liable to be
scoured out and the bottom lowered. When coral, together with the shells
of molluscs and other organic refuse of the teeming life of tropical
seas, reaches the surface of the water, fragments and even large masses
are broken off by the force of the waves, ground into calcareous sand
owing to the movements produced by the waves and currents, and much of
it heaped on the borders of the reefs so as to raise them above the
fair-weather level of the sea. Much of this material, when it becomes
dry, is moved by the winds and built into dunes, thus still further
increasing the height of the land. Many of the islands in the Bahamas
have thus been formed, but the process has been modified in the greater
part of that region by movements in the earth's crust which have
produced widely extended elevations and depressions. The larger islands
in the Bahama group are coral platforms which have been moderately
elevated, and bear on their surfaces extensive accumulations of
wind-deposited sand. The Yucatan peninsula is also, to a great extent,
an upraised coral platform. The surfaces of such exposed areas of easily
soluble calcareous rocks are roughened still more by the action of rain
and percolating waters, and if subsequently submerged to a moderate
depth would give origin to "banks" with uneven, and possibly
conspicuously roughened surfaces. Different stages in this varied
history are illustrated throughout the West India region.
About the Caribbean coast of Honduras and Nicaragua the continental
shelf is broad and is termed the Mosquito Bank, in reference to its
proximity to the widely known coast of that name. Off the northeast cape
of Honduras this submerged shelf has a breadth of about 125 geographical
miles, and is succeeded to the eastward by the much smaller,
isolated, submarine plateau known as the Rosalind Bank. Even on a small
map, like that forming Fig. 3, it is readily seen that in
general terms there is a series of banks and low islands extending from
the Mosquito Coast to Jamaica, Santo Domingo, Porto Rico, and the
Caribbees. The distance measured along the curved line connecting the
several areas of shallow water is about 1,700 geographical miles. Should
this region be upraised 600 feet, the new lands that would appear would
still, in several instances, be separated by deep water, thus showing
that although in a generalized view it is convenient to consider the
banks and shelves referred to as parts of a single great group, there
are several centres from which they have grown.
A third great group of banks and shoals occurs about the borders of
Cuba, especially along its southern margin. Associated with this
submerged plain of calcareous mud, roughened by countless coral crags,
is a narrow east-and-west ridge in the Caribbean Sea, known in part as
the Misteriosa Bank, which rises precipitously on its southeast border
from a depth of over 3,400 fathoms, and is indicated at the surface by
the Cayman Islands.
The Caribbean and Gulf of Mexico region has great depressions or "deeps"
as well as broad banks or shoals. The submarine topography is, in fact,
on a more Titanic scale than in any other known region. Brownson Deep,
some 50 miles north of Porto Rico, has a depth of 4,561 fathoms (27,366
feet), and the bordering slopes of the depression in certain places, and
for long distances, have an inclination of 35 degrees. Between 15 and 30
miles south of Porto Rico the bottom of the Caribbean Sea is 1,500
fathoms below its surface, and rapidly descends to over 2,400 fathoms.
Bartlett Deep, a long, narrow depression in the sea-floor, intervening
in its eastern portion between Cuba and Jamaica, has a depth of 3,428
fathoms (20,568 feet) measured from the surface of the sea. Sigsbee
Deep, in the central portion of the Gulf of Mexico, is a third basin of
similar nature, remarkable for the great extent of its nearly
level floor, which is from 2,035 to 2,071 fathoms below sea-level. (On
Fig. 3 only the general depths of these great depressions are
indicated.) Coupled with the profound depth of the sea in the West
Indian region are the rugged mountains of the Great Antilles and the
volcanic cones of the Caribbees. Some of the elevations of the land
referred to are, in feet, as follows: Porto Rico, 3,609; Jamaica, 7,360;
Cuba, 8,600; and Santo Domingo, 10,300. The extreme range in the relief
of the surface of the solid earth (lithosphere) between the bottom of
Brownson Deep and the summit of Santo Domingo is 37,666 feet--the
horizontal distance between the two is about 270 geographical miles. No
mountain on the earth has such an elevation above sea-level. The islands
of the West Indies are thus shown to be the summits of stupendous
mountains, the greater portions of which are submerged. The low-lying
islands, and even the banks which can be discovered only with the aid of
the sounding-line, are in reality the tops of wonderfully steep
mountains or plateaus some 20,000 feet in height.
It is a significant fact that the profiles of the partially or wholly
submerged mountains of the West Indies are, as a rule, steeper than the
slopes of the mountains on the land with which they may reasonably be
compared. This is due in part, perhaps, to the greater density of the
medium in which they stand, the sea-water affording a greater degree of
support than the air, but the main reason is that beneath a few hundred
feet of water there is no erosion except the exceedingly slow removal of
matter in solution. Could the waters of the sea be withdrawn so as to
reveal the Caribbean Mountains in all of their stupendous grandeur, the
vast, smooth, sweeping surfaces extending from the horizontal lines
drawn about the higher summits by the waves and by the deposition of
sediment and coral growths, down to their bases would be unmarked by
channels and ridges of the character that give details to the type of
mountains with which we are most familiar.
An instructive generalization concerning the relief of the West India
region, suggested by Alexander Agassiz and sustained by the later
studies of R. T. Hill, is that we there find topographic forms produced
by movements in the earth's crust which have not been modified by
erosion. The great elevations rising from the floors of the "deeps" are
upraised blocks of the earth's crust which have not been beaten by rain,
shattered by frost, or trenched by rills, creeks, or rivers. They
illustrate the character of the rough blocks of rock from which many of
the mountain forms of the land have been sculptured.
This sweeping view, which it seems safe to accept as a generalized
outline of the history of the topography of the region in question,
needs to be qualified, as there are known to have been extensive up and
down movements throughout large areas in that portion of the earth's
surface. The mountains on Jamaica are scored by horizontal lines marking
former sea-levels up to a height of 2,000 feet, and similar and still
higher records are plainly visible on several of the larger West India
islands. This evidence shows that the present land over a wide extent of
the Caribbean region was formerly deeply submerged. More than this, the
rocks forming the higher portions of the Greater Antilles are largely
composed of more or less consolidated ooze, such as is now found on the
sea-floor in deep water. This line of evidence shows that what in late
geological time was the sea-floor has been raised between 20,000 and
30,000 feet. It is thus known that both upward and downward movements of
great vertical and great horizontal extent have occurred in the
Caribbean region. Whatever minor changes the topography of the now
submerged sea-floor may have suffered owing to emergence, the general
relief, as suggested above, seems to have resulted from movements in the
earth's crust, and that these movements, in certain instances at least,
produced faults--that is, breaks or fissures--along which the rocks were
upraised on one side or depressed on the other, so as to form great
cliffs. The precipitous submarine slope forming the northwest border of
Bartlett Deep may reasonably be interpreted as a great fault scarp. A
portion of this escarpment rises above the sea and forms the remarkably
straight and exceedingly rugged south coast of Cuba in the region
of Santiago. In the main the remarkable submarine topography of the West
India region presents us with an example of what would have been the
leading features of several portions of the earth's surface which are
now land, as, for example, the Great Basin region of Utah, Nevada, etc.,
had deformation gone on without erosion.
MOVEMENTS OF THE OCEAN WATERS
To the student of the geography of a continent the climatic and other
influences of the great ocean currents, as well as the more tangible
results produced by the waves which break on the borders of the land,
demand extended and painstaking investigation. The most that we can hope
to do at present in this connection is to state briefly some of the more
important influences that the movements of the ocean waters have on the
climate of North America and on the topography of its shores.
_Currents._--The surface waters of both the north Atlantic and the north
Pacific, as is the case with all broad water bodies, have a drift and in
places flow in well-defined currents, mainly on account of the friction
of the wind on the surface of the sea, aided by variations in the
density of the water due to differences in temperature and salinity. In
each ocean there is a great swirl or eddy, for the reason that the
surface drift and the flow of the deeper currents carry the waters about
in a rudely circular path, parallel in a general way with the boundaries
of the respective basins. The direction of this motion, to one situated
in the central part of either basin, is from left to right, or with the
movements of the hands of a watch. In the southern portion of each basin
there is a westward-flowing equatorial current, which in each instance
is deflected northward on approaching the bordering land, and as it
continues is still more deflected owing to the influence of the earth's
rotation, and acquires a northeast trend; on reaching the eastern side
of the oceanic basins, the currents are again deflected, a portion of
the one in the Atlantic and all of the one in the Pacific being
turned southward so as to complete the circuit.
In the southern portion of the north Atlantic the surface drift is
westward at a rate of four or five miles a day. The waters, forced along
principally by the trade-winds, flow through the numerous passes between
the Lesser Antilles and enter the Caribbean Sea, and from thence are
carried through the Yucatan channel into the Gulf of Mexico. The waters
are piled up, as it were, in that great landlocked basin, at the same
time becoming warmer, and receive additions of fresh water from rain and
inflowing streams. Each of these causes tends to decrease the density of
the water, while evaporation has a counterbalancing influence. The
escape for the waters, both salt and fresh, which enter the Gulf, is by
evaporation and by flowing through the only notch in the rim of the Gulf
basin which is not in the path of the equatorial current, namely, the
strait separating Florida from Cuba and the Bahama Islands. These
outflowing waters form the justly celebrated Gulf Stream.
Between Florida and the shoal waters on the Bahama Banks the Gulf Stream
is about 50 miles wide, approximately 350 fathoms deep, and flows
northward at the rate of from four to five miles an hour. Its
temperature is about 80° F. It is estimated that this great river in the
ocean carries 90,000,000,000 tons of water per hour past a given
cross-section. Its course is northward along the immediate border of the
continental shelf until it arrives opposite the Carolina coast, and
thence northeastward, thus giving it a constantly increasing distance
from the land. To the north of the Bahamas it receives as a tributary
the portion of the equatorial current, perhaps even greater in volume
than the true Gulf Stream, which is deflected northward by the West
India Islands and their associated banks. Continuing its course, it is
deflected still more towards the northeast owing to the influence of the
earth's rotation, at the same time expanding and losing velocity so as
to become a surface drift rather than a well-defined current. Under the
influence of the prevailing westerly winds of the north Atlantic, the
waters delivered by the Gulf Stream pass the vicinity of the
British Islands and in part enter the Greenland Sea.
[Illustration: PLATE I.--Orographical features.]
The transfer of the vast amount of warm water carried by the Gulf Stream
far to the north is counterbalanced in part by a southward-flowing cold
current which emerges from Davis Strait, and being joined by another
cold current from the eastward of Greenland, continues southward under
the name of the Labrador current, past Newfoundland and Nova Scotia to
the Massachusetts coast, and is thought to exert an influence on the
temperature of the sea even as far south as Cape Hatteras. While the
Gulf Stream in the northern portion of its course curves eastward and
departs from the American coast, the southward-flowing Labrador current
is turned westward and follows close along the border of the land, and
mainly over the continental shelf.
The chief effect of the cold current from the north in proximity to the
coast of the continent is to bring to the adjacent land a lower mean
annual temperature and especially colder and more stormy winters than it
would otherwise experience. This tendency is augmented by the icebergs
carried southward with the Labrador current. In a similar way, the
northward-flowing warm current gives Florida and the Carolinas a
subtropical climate, admits of the growth of reef-building corals about
the Bermuda Islands, and carries so much warmth to northwestern Europe
that its climate is milder and more humid than one would expect from its
geographical position.
The currents of the north Pacific are analogous to those of the north
Atlantic, but simpler, as there is nothing similar to the true Gulf
Stream, and as communication with the Arctic Ocean is practically
closed, there is no cold current flowing southward from that ocean; but
the conditions, so far as they influence the climate of North America,
are reversed. A warm current flowing northward off the coast of Japan,
and hence known as the Japan current, crosses the Pacific, and on
approaching the coast of Alaska and British Columbia is deflected
southward. The climate of the northwest coast is thus ameliorated, the
prevailing westerly winds are warm and humid, and the mean annual
precipitation from western Alaska to Oregon is in the neighbourhood of
100 inches. Under the influence of a mild equitable temperature and
abundant moisture, the land bordering the Pacific from southern Alaska
to northern California is clothed with the most magnificent forests that
the continent affords. The marked contrasts in climate, vegetation, and
the conditions that influence civilization between the two sides of the
North American continent, produced by the cold Labrador current on the
east and the warm Japan current on the west, is shown in a marked way by
the sweep of the lines of equal mean annual temperature (isotherms)
represented on the map forming Plate II, and again by the
distribution of forests, as will be described later. It is instructive
to note that the climate of Sitka, in north latitude 57°, is far more
temperate and equable than that of New York city, latitude 40° 45',
although the cool summers on the northwest coast make the mean annual
temperature somewhat lower than on the coast of New York, or even of New
England.
The influence of the opposite conditions in reference to ocean currents
experienced by the eastern and western borders of the continent are even
more marked in the life of the adjacent waters than in the vegetation
and fauna of the land itself. The plant and invertebrate life of the
shoal waters of the Pacific coast, consisting largely of southern
species, is exceedingly rich and varied, even to the inlets of the
Alaska coast, where glaciers come down to the sea; while on the Atlantic
border, northern species occur on the New England coast, and even
farther south. The contrasts in temperature between the waters of the
Atlantic and Pacific which cover the submerged border of the continent
are well shown by the distribution of the cod, the most valuable of all
fishes to man, which, as is well known, belongs to the northern fauna
and ranges from the north Atlantic about the arctic coast of both the
Old and the New Hemispheres, to the north Pacific. On the east coast of
America this circumpolar fish, of which several species are known, is
found occasionally as far south as Cape Hatteras, but the most southern
"bank" on which it is extensively taken is off Cape Cod, in
latitude 42°; on the west coast it travels perhaps as far south as the
mouth of the Columbia, but the most southern locality where it occurs in
commercial quantities is off the Shumagin Islands, in latitude 55°. The
life of the continental shelf, as well as of the adjacent land, thus
bears testimony to the vast importance to North America of the great
ocean currents washing its shores.
_Tides._--The waters of the ocean are subject to wave-like undulations,
caused by the attraction of the moon and sun, termed the tides. Every
day, at the average interval of twelve hours and fifty-one minutes, the
"tide rises," and with equal regularity intermediate between these
periods it "falls." This rise and fall of the waters along the coast,
accompanied frequently by strong currents, are produced directly by the
arrival in the shoal water of a pulsation of the ocean, which becomes a
true onward-moving gravity wave as it nears the land. In the open sea
the amplitude of the tidal undulations is but two or three feet, and
their rate of travel in general 700 to 800 miles per hour. On reaching
shoal water, however, the onward movement is decreased by friction on
the bottom, the waves become higher, and when they meet an
outward-flowing bottom current, their bases are still more retarded and
the slope of their fronts increases until the water falls forward and
breaks into foam. On the Atlantic coast, each tidal wave reaches the
land broadside on, as it were (Fig. 4), and at the outer capes high
water occurs at practically the same time from Florida to New England,
but its farther landward progression is greatly modified by the shape of
the coast and the depth of water in the estuaries and other
indentations. When the wave as it rushes landward enters a broad water
body through a narrow entrance, as the Gulf of Mexico, for example, it
spreads, and as the impulse is transmitted to larger and larger volumes
of water, it decreases in height. (In a critical study the tides
originating in the Gulf itself should be considered.) At Galveston,
Texas, the mean range between high and low tide is less than one foot.
When, however, an estuary with a broad mouth receives a tidal wave from
the ocean, the impulse is more and more concentrated and the wave
rises higher. At the head of the Bay of Fundy the difference between
high and low water is from 50 to 60 feet. For the reason just stated,
the tidal wave is generally higher in the Atlantic coast estuaries than
on the ocean capes, and under favourable conditions may be transmitted
for long distances up the rivers emptying into such estuaries, and may
be felt where the mean elevation of the stream is several feet above the
mean level of the sea on the neighbouring open coast. Tidal waves pass
up the Hudson to Troy, a distance of 150 miles from the Narrows,
where the mean range is 2.3 feet. In St. John River, New Brunswick, the
tidal impulse is felt at Frederickton, 70 miles from the Bay of Fundy,
and at an elevation of 14 feet above its surface. In the St. Lawrence
estuary and river the tidal waves ascend 283 miles to Three Rivers, a
few miles below Montreal, where the mean elevation is about 11 feet and
the mean range of the tide 0.9 foot. In the Columbia the range of the
tide is about 6 inches at a distance of 140 miles from the ocean.
[Illustration: FIG. 4.--Co-tidal lines. A diagrammatic representation of
the advance of tidal waves in the Atlantic and Pacific. Figures refer to
noon and midnight. After R. S. Tarr.]
In the north Pacific (Fig. 4) the tidal waves come from the south and
expand much the same as the corresponding waves do in the north
Atlantic, but instead of striking the coast broadside on, sweep along
the shore from south to north.
There are two localities on the coast of North America, one at the head
of the Bay of Fundy and the other at the head of Cook's Inlet, Alaska,
where the tides present especially interesting features. In each of
these inlets the incoming tidal wave meets an outward-flowing current
which tends to hold it back. The incoming waters are thus piled up until
sufficient head is established to cause them to advance as a
steep-fronted wave termed a _bore_, which curls over and breaks in a
long line of foam as it rushes along. At the head of the Bay of Fundy
the bore travels at the rate of 6 or 7 miles an hour, and has a height
of from 4 to 6 feet. The great disturbance produced by the strong
current and breaking waves causes the mud of the bottom to be disturbed
and the waters to be charged with sediment. Much of this mud is
deposited during the interval of quiet water at high tide, and as the
outflow is not so impetuous as the inflow, broad mud-flats are formed.
At certain localities about the Bay of Fundy artificial dikes have been
made, which admit the mud-charged waters at high tide, and retain them
until much of their freight is deposited. In this manner, large areas of
rich lands have been secured.
The geographical influences of the tides and of the currents produced by
them are of interest in many ways. To navigators they are of special
importance. Even in this age of steam, the arrival and departure
of vessels from harbours is regulated so as to take advantage of the
incoming or outgoing tidal currents. Many harbours can be entered by
deep-draft vessels only at high water, for the reason in general that
sand-bars are frequently formed at the mouths of tidal estuaries. One of
the most marked illustrations of the influence of the rise and fall of
the tide on navigation occurs at St. John, New Brunswick, where the tide
flows in and out of St. John River so as to form a cascade each way,
dependent on the direction of the current. At low water the level of the
river is from 11 to 15 feet above the Bay of Fundy, and at high water
the level of the bay is from 8 to 12 feet above that of the river when
not affected by the tide. There are four periods of from ten to fifteen
minutes each during each twenty-four hours when vessels can pass in and
out of the river's mouth.
In the Arctic Ocean the tides are small. At Point Barrow, the most
northern locality on the coast of Alaska, the difference between high
and low water is but 6 or 7 inches. The tide comes from the southward
and westward, and there is a prevailing current setting to the eastward.
At Herschel Island, near where the east boundary of Alaska reaches the
Arctic Ocean, the mean range of the tide is but 1.8 foot. At Cape
Sheridan, the northeast point of Grinnell Land, north latitude 82° 25',
there is a range of 2.6 feet during two periods each month when the
tides are highest, and but 1.2 foot at the lowest or neap tide periods.
In addition to the weakness of the tides and tidal currents along the
arctic coast, there is an absence or great diminution of the influence
of wave and currents, owing to the prevalence of ice on the sea. Shore
erosion is there at a minimum in spite of the abrasion produced by the
ice-packs when forced landward by the wind.
_Islands._--In the classification of islands used by A. R. Wallace in
his Island Life two primary divisions are recognised, namely,
continental and oceanic islands.
Continental islands are land masses which have been separated from
continents and are rarely far removed from their borders, and,
besides, are composed of rocks similar to those of the neighbouring
mainland and inhabited by terrestrial animals which are related to the
fauna of the larger land area. Ancient and modern continental islands
have also been recognised, their age being indicated by the degree of
similarity between their faunas and the fauna of the continent with
which they were formerly connected. Those of ancient origin are commonly
surrounded by deep water, while those which are more modern usually rise
from continental shelves, the channels intervening between them and the
mainland being less than 100 fathoms deep. Oceanic islands rise from
deep water, are either volcanic or so far as their emerged portions are
concerned composed of coral rock, and are without warm-blooded
terrestrial animals.
About the borders of North America there are islands belonging to each
of these classes. The numerous examples rising from the continental
shelf all about the margin of the land, but in the Atlantic most
numerous from New York northward, and in the Pacific from the Strait of
Fuca northward, are plainly recent continental islands. The larger of
the West Indies and the group of small islands off the California coast
are also continental islands, but show by the character of their faunas
and the depth of the water about them that they have been long separated
from the main mass of the continent. Typical examples of oceanic islands
are furnished by Bermuda, in the Atlantic, and Guadalupe, in the
Pacific. In this same class, but less remote from the mainland, and in
their faunas and floras showing a nearer relationship to South than to
North America, belong the Caribbees.
TOPOGRAPHY OF THE COAST
The generalized coast-line of North America measures about 35,000 miles
in extent, and presents a great variety of scenery. The range in
diversity embraces all classes of coast topography from the low, sandy
mangrove-fringed borders of Florida and the Gulf of Mexico, to the
magnificent sea-cliffs of Labrador and British Columbia and the
marvellous ice-walls of Greenland and Alaska where tide-water glaciers
enter the ocean.
Like nearly all the features of the earth's surface, this narrow
intricate belt where the sea and land meet is constantly undergoing
changes. The principal processes which lead to alterations in the
coast-line may be considered as forming three groups: First, the wearing
away of the land through the action of waves and currents and the
deposition of the _débris_ thus produced so as to make additions to the
borders of the continent; second, the upward and downward movements of
the land; and third, the changes produced by glaciers, ice-flows, and
icebergs.
With these more active agencies by which the coast-line is being
modified may be included chemical solution and deposition, the influence
of plants and animals, the weathering of the margin of the land, etc.;
but a critical review of all these processes is impracticable in the
present treatise.
_Changes in the Coast-Line due to Waves and Currents._--The waves of the
sea beat on the land with never-ceasing activity, but exert the greatest
force during storms. The blow which a great surge strikes when it breaks
at the base of a cliff, amounting in many instances to 3 or more tons to
the square foot, tends to disrupt the rocks both directly by its impact
and by the compression of air and water in their interstices. The
greatest work of the breaking waves is performed, however, with the aid
of the stones which accumulate on the beaches. These are hurled against
the land by the force of the landward-rushing waters and break and
abrade the rocks with which they come in contact. The friction produced
by the impact of waves charged with sand, pebbles, and boulders against
the land leads to its removal along a horizontal belt with a narrow
vertical range. The waves of the sea, in fact, act like a horizontal
saw, the edge of which slowly advances landward. As a result of this
process of under-cutting, highly characteristic and frequently most
picturesque forms are given to rocky coasts. Whenever the sea is
bordered by hard rocks standing well above the surface, but not rising
too precipitously from deep water, we find cliffs facing seaward.
At the base of each of these sea-cliffs there is a shelf or terrace
which records, in part at least, the advance that the sea has made
inland.
A cross profile of a wave-cut seashore (Fig. 5) shows two prominent
features, namely, a sea-cliff with a horizontal base, and a terrace
sloping seaward from the foot of the cliff. Of these, the cliff is by
far the more prominent as it stands up boldly to view, while the terrace
is in large part and perhaps wholly submerged. These two leading
characteristics in the topography of wave-cut shores are shown in the
following diagram:
[Illustration: FIG. 5.--Ideal profile of a sea-cliff and current-built
terrace.]
The water carried landward by each wave as it rushes up the sloping
surface of a terrace again finds its way seaward, either wholly or in
part, as an "undertow." Much of the rock _débris_ ground fine by the
ceaseless beating of the surf is separated from the coarser material,
thus leaving the latter free to be moved by succeeding waves, and is
carried seaward by the bottom current or undertow. During storms
especially there is usually to be seen a belt of discoloured water
seaward from the white breakers which margin the land. The finer
_débris_ carried away from the shore by the undertow is sooner or later
deposited, and much of it is laid down on the terrace bordering the land
and serves to build out its seaward margin. A normal sea-terrace is thus
in part the result of the cutting away of the land, and in part of the
deposition of the material removed. The sea not only cuts away the land,
however, but at many localities makes important additions to it.
Where the water is shallow the larger waves break at a distance perhaps
of several miles from the coast-line, and build up long narrow bars,
usually of sand, which form barriers, more or less parallel with the
shore, and shelter it from further encroachments of the sea. Again, when
the wind from the sea blows obliquely to the coast, currents are
established in the water which sweep along the loose material on the
beach and on the submerged portion of the terrace of which the beach is
a visible part, and cause it to travel in the general direction of the
prevailing on-shore winds. This action also leads to the building of
bars more or less parallel with the coast and at the extremities of
capes, particularly where the shore currents enter deeper water and give
origin to spits of various shapes, which are frequently curved towards
the land and at their extremities become hooks and loops.
There are thus two important processes, one destructive and the other
constructive, by which the sea is continually modifying the border of
the land.
When once the underlying principles on which depend the characteristics
of coastal topography are suggested, any observant person can apply them
for himself and thus be able to read the history as well as admire the
beauties of seacoast scenery. It is not necessary, therefore, to attempt
to present a detailed account of the coasts of North America from a
purely geographical point of view; there are certain results of the
processes just referred to, however, which are of wide-reaching
economic, and especially of commercial interest.
[Illustration: FIG. 6.--A portion of the Atlantic coast of the United
States.]
From Central America northward to Cape Cod the rocks bordering the sea
are soft or easily soluble, and the adjacent land of low relief.
Throughout this section the work of the sea is mostly constructive, and
the margin of the land is sheltered by sand-bars from the attack of
waves and currents. Where the waves of the open ocean do reach the land,
as on the coast of New Jersey, the sea-cliffs are low and the topography
of a mild type. Very generally, as along the coast of Mexico and Texas,
and from Florida to Long Island, there are long narrow bars adjacent to
the shore, with lagoons intervening between them and the mainland.
These features are well illustrated on the accompanying map (Fig. 6) of
a portion of the Atlantic coast where long narrow bars, sometimes
forming skeleton capes, are a characteristic feature. On the middle
Atlantic coast of the United States the prevailing winds blow southward
and there is a general southward flow of the shore currents, which carry
with them the sand on the beaches and bars. An interesting fact in this
connection, pointed out by N. S. Shaler, is that although the sands are
continually being moved they are not worn out. After the sand-grains
have been reduced to a certain size they retain films of water which
separate them one from another, and act as cushions which prevent the
grains from coming in contact, thus greatly retarding further
comminution. But for the protection thus afforded the sand-bars would be
removed and the border of the land exposed to the attack of the waves
and cut away; whereas under existing conditions lagoons are formed,
which in many instances are utilized as harbours or are filled by
wind-blown sand, the sediment brought by streams, plant growths, etc.,
and valuable additions are made to the continent.
[Illustration: FIG. 7.--Mobile Bay.]
The sand-bars just referred to frequently cross the mouths of rivers,
and in such instances a struggle ensues between the currents moving
along the shore and the outflowing river-waters aided by the currents
produced by the tides. This conflict leads to the formation of sand
banks and bars, generally submerged, across the entrances of bays and
inlets and to the building of sand-spits from the seaward capes. A
typical instance is furnished at the entrance of Mobile Bay (Fig. 7),
where a spit from each side has been built by shore currents so as
to greatly contract the tideway between. Similar features are presented
by Sandy Hook and Coney Island, each of which has been built of sand
deposited by shore currents at the seaward entrance of the lower New
York Bay. Another illustration of this same general character is
furnished by the curved extremity of Cape Cod (Fig. 8), which is a
sand-spit of large size with a hooked extremity. Spits of this nature
are common on our coasts, and in many instances themselves form
harbours, as at Coney Island and near the extremity of Cape Cod. Many
other similar examples of the importance of lagoons, sand-bars, spits,
etc., to shipping, which occur, especially along the Atlantic coast of
the United States, may be studied to advantage on the admirable charts
of the United States Coast and Geodetic Survey.
[Illustration: FIG. 8.--Cape Cod, Massachusetts.]
The sand-bars, spits, and other similar structures along the Atlantic
coast are also of strategic importance, for the reason that they afford
advantageous sites for fortifications, as is illustrated by the strong
forts at Sandy Hook which guard the entrance of New York Bay. These
sea-built foundations are also utilized in a large number of localities
for lighthouses. The waterways shut off from the sea by off-shore bars
in some instances permit of the passage of vessels from one harbour to
another. In this connection it is of interest to note that an important
system of canals is under consideration for making a continuous waterway
for deep-draft vessels, some 700 miles long, which will connect the
estuaries and lagoons from New York to the Carolinas.
While the islands of sand referred to present many conditions favourable
to commerce, fisheries, and other industries, their apparent durability
is deceptive, and in some instances faith in their permanence has led to
disastrous results. They owe their existence to the action of waves and
currents, and unless blown sand is heaped upon them are raised but a few
feet above mean sea-level, and are liable to inundation if a high tide
is accompanied by an on-shore gale. A sad illustration of this plain
conclusion is furnished by the disaster that overwhelmed the city of
Galveston on the night of September 8, 1900, during which some 3,000
people perished and $20,000,000 to $30,000,000 worth of property was
destroyed. This great loss was in large part due to the fact that the
city was inundated by the advance over its site of the storm-driven
waters of the Gulf of Mexico. The island on which Galveston stands (Fig.
9) was built by the waters of the Gulf, and during the hurricane
referred to they again claimed their own.
[Illustration: FIG. 9.--Coast of Texas.]
Northward of Cape Cod, the rocks adjacent to the ocean are mostly hard
and resistant, consisting largely of schist, gneiss, granite, trap,
etc., which when undercut by the waves stand as bold cliffs and
headlands. This portion of the continental border abounds in picturesque
scenery and is abundantly supplied with fine harbours and well-sheltered
havens in which boats may take refuge. Typical portions of this
rugged coast are furnished by the magnificent sea-cliffs of Mount Desert
and Grand Manan islands, the bold shores of Newfoundland and Labrador,
and the precipitous border of Greenland. The scenery throughout nearly
all of this vast extent of wave and storm beaten rocks is in striking
contrast to the mild and generally monotonous sand-built shores to the
south of Cape Cod. Between the angular headlands and rugged capes at the
north, with their white girdles of surf, there are frequently curved
beaches and numerous spits and bars of yellow sand which connect the
salients of the shore or extend from them so as to furnish safe
anchorages.
On the arctic coast of North America the action of the waves and
currents on the land is greatly retarded by ice, and the tides are
small, but to what extent these conditions unfavourable to the work of
the sea are counterbalanced by the abrasion performed by ice-floes is
unknown. The northern border of Alaska, as well as the shore of Bering
Sea, is mostly low and the rocks soft, although certain of the sea-capes
are bold and are evidently composed of resistant material.
The Aleutian Islands present a peculiar exception to the general coast
topography of the rest of the continent. Although this region has not
been studied in detail, it seems to furnish an example of a rugged
mountain range that has been partially submerged at a comparatively
recent date. The rocks in many places descend precipitously into deep
water, leaving no room for the formation of beaches, and hence the
waves, to a great extent, are without tools with which to cut away the
land. At the heads of the many bays and inlets, however, one finds
beautiful sand-beaches with gracefully curving lines, in striking
contrast to the dark, rugged cliffs bordering their seaward extensions.
The southern and southeastern borders of Alaska are exceedingly bold,
and present some of the most sublime coast scenery to be found in the
world, but to the geographer the greatest interest of this portion of
the continental border, as is true also of the entire Pacific coast of
North America, centres in its relation to up and down movements of the
land.
_Changes in the Coast-Line due to Oscillation of the Land._--Land areas
are exposed to the erosive action of wind, rain, streams, etc., and are
sculptured by these agencies into valleys, cañons, peaks, ridges, and
other familiar topographic forms. The various processes by which land
areas are modified lead in general to a roughening of the surface. As an
extreme illustration, a high plateau becomes dissected by streams so as
to form an intricate system of rugged mountain ridges and peaks, with
deep, steep-sided valleys between. The degree of this roughening depends
principally on the elevation of the land, together with contrasts in the
resistance of the rocks due mainly to variation in hardness, climatic
conditions, etc., but in general one may say the higher the land
is raised above the sea the more rugged will be its topography as the
process of wearing away progresses. It is to be remembered in this
connection, however, that land areas pass through a somewhat definite
series of changes, from topographic youth to topographic old age, each
stage being accompanied by changes in the relief. It is during
topographic maturity that the greatest roughness of the surface of a
land area is produced.
Land areas are continually wasting away, owing especially to the attacks
of the streams, and the material removed is deposited in the sea. The
_débris_ brought from the continents by streams is laid down in shallow
water--about the shores of North America almost entirely on the surface
of the continental shelf--and in this region of deposition the hollows
are filled and a generally smooth surface given to the sea-floor.
The topography of the land, for the reason stated above, is nearly
everywhere uneven; while the topography of the sea-floor is
characterized by uniformity. We can easily predict, therefore, the
general character of the changes in a coast which would result from
either a subsidence of the land, thus allowing the sea to encroach upon
it, or of an elevation, which would expose a portion of the sea-bottom,
thereby increasing the area of the land. A subsidence of the land
adjacent to the sea permits an extension of the waters landward; the sea
will enter the valleys so as to form estuaries, bays, straits, etc.,
while the high land between the partially water-filled depressions will
rise above the water-level and appear as peninsulas, capes, and islands.
A bold, deeply sculptured coast when depressed will give origin to an
intricate, and what may be termed a ragged shore-line; while a lower
region crossed by large river-valleys would be changed to a system of
broad estuaries.
An upward movement in the earth's crust along the ocean's shore would
expose a portion of the sea-floor and add a strip of generally level
country to the previous land area. The boundary between the old and new
topography in such an instance would be the upraised coast-line with
its sea-cliffs, wave-cut caves, terraces, beaches, and other
characteristic features of coast topography.
There are thus two strongly contrasted types of coast scenery, produced
by oscillations of the earth's crust where ocean and continents meet. In
each class there is a wide range in details, which vary in harmony with
the amount the land rises or falls in reference to sea-level.
When one has these general laws in mind a map of the coast-line of North
America acquires great significance.
From about the latitude of New York southward to Central America many
comparatively small oscillations of the land have occurred in recent
geological time, and what was formerly a portion of the continental
shelf is now exposed and forms a coastal plain. This plain, in general
from 50 to 100 miles broad, slopes gently seaward, and its continuation
under the sea forms the present continental shelf (Fig. 2). Evidently a
slight up or down movement or a gentle tilting of this partially
submerged plain in an east and west direction would cause a marked
advance or recession of the sea. Each time the sea advanced the country
submerged would be smoothed over by the action of the waves and currents
and a sheet of sediment laid down upon it; and each time the sea receded
the emerged land would be trenched by the rivers flowing across it. The
records show that many such changes have occurred.
The Gulf border of Mexico and Texas, composed of soft marine sediments,
forms a gently sloping plain bordered on the west by a roughened upland,
and illustrates the general feature of a recently emerged coastal plain
(Fig. 9). The same is true also of the entire coast from Texas to New
York, but it happens that a recent movement through this region was of
such a nature as to allow the sea to encroach on the land, and the
previously excavated stream valleys are now, in part, occupied by the
sea. This feature is most marked from the Carolinas to New York (Fig.
6), where there are several great estuaries and drowned river-valleys
which extend far into the land. The best examples are Albemarle Sound
and Chesapeake and Delaware Bays. The James River channel is submerged
as far as Richmond, the Potomac to Washington, the Susquehanna to
Harrisburg, the Delaware to Trenton, and the Hudson to Troy. These are
typical illustrations of what geographers term drowned river-valleys.
They are evidence that the land formerly stood higher than now, was
trenched by the rivers that flowed across it, and was then depressed or
tilted so as to allow the sea to encroach upon it. The importance of
these events in the settlement of North America by Europeans and on the
subsequent development of commerce, manufactures, the location of
cities, etc., needs only to be suggested to permit the reader to fill in
the details for himself.
On the Gulf coast and about Florida the later movements of the land have
been less than in the region from Albemarle Sound to New York, and
estuaries are there absent, with the somewhat marked exception of Mobile
Bay. Certain secondary conditions need to be introduced here, but space
will not permit of more than a brief presentation of them. Not only have
the recent movements of the land been less about the shores of the Gulf
of Mexico than in the middle Atlantic region of the United States, but
the rivers at the south are in general smaller and less swift than those
farther north, and hence are less able to excavate broad valleys. The
Southern rivers, such as the Alabama, Mississippi, Rio Grande, etc., are
silt-laden and tend to fill their estuaries, while the weaker streams
are unable to resist the encroachments of sand-bars and spits built by
shore currents, and their mouths have been practically closed. The coast
of Texas gives evidence of slight modern subsidence, but the small
estuaries formed have, for the most part, been separated from the Gulf
by sand-bars.
Northward of the middle Atlantic region the recent oscillations of the
land continued to increase and reached a maximum about the shores of the
Arctic Ocean; on the Pacific coast also there is similar evidence of an
increase in the recent earth movements from the south northward.
In an outline sketch of the present coastal topography of the continent
we can generalize, and say that the whole continent during the late
Tertiary, glacial, and recent times has swayed up and down about a
hinge-line situated in the region of the Gulf of Mexico, and the
movements, although not uniform, have increased in amount from the south
northward. Let us glance at the evidence on which this broad statement,
involving the up and down surging of a vast continent, is based.
The Hudson, as stated above, is a drowned river as far as Troy, a
distance from the present land margin of 160 miles. In the next great
river to the northward, the St. Lawrence, the tide rises and falls
nearly up to Montreal, a distance of about 800 miles from the general
shore-line. Still farther north are Hudson Strait and Hudson Bay, which,
although but imperfectly explored, seem to be an example not only of the
drowning of a river-valley, but of the largest part of a river-basin.
The geography of the arctic archipelago fringing the north shore of the
continent also suggests that a strongly stream-cut plateau has there
been deeply submerged.
In addition to the drowned river-valleys and ragged coasts which record
a subsidence of the land, there are raised terraces and beaches which
begin at the south near New York and increase in elevation above the
present sea-level, when followed northward, all the way to the arctic
region, and have in the far north an altitude of about 1,200 feet. These
old beaches and terraces show that the land was formerly depressed and
has since risen; but, as shown above, has not regained the elevation it
had previous to the glacial epoch.
The marked differences in the geography of the coast from New York
northward to the Arctic Ocean, and from the same locality southward to
Central America, are due primarily to the fact that the oscillations of
the land have been such that at the north the continental shelf is
entirely submerged and the sea has encroached on a rough land; while at
the south the recent oscillations have been less and a broad margin of
the continental shelf is exposed and forms the coastal plain.
At the north, we find innumerable islands, bold, rocky shores with many
capes and headlands, separated by deep inlets, sounds, straits,
bays, etc., or, in brief, a ragged coast such as finds typical
illustration on the shores of Maine (Fig. 10), while at the south (Fig.
6) the shores are low, sandy, remarkably uniform in trend, and without
islands, excepting such as are built by the waves and currents. The West
India Islands will, no doubt, be recalled by the reader, but their
history is again different. Intermediate between the land that has
experienced great oscillation at the north and the region of less
energetic movements at the south is the series of large estuaries
mentioned above, in the narrower portions of the coastal plain.
[Illustration: FIG. 10.--A portion of the coast of Maine.]
The northern and western coasts of Alaska are mostly low, and correspond
in a general way with the coastal plan of the Carolina region. The last
well-marked movement of the land in that region has been in the
direction of an elevation, and we find low shores, with but few
harbours, similar in many ways to the coast of Texas.
It is probably true, as already stated, that the Aleutian Islands,
although in part the result of recent volcanic activity, owe their
peculiar and exceptional characteristics to the partial subsidence of a
deeply sculptured mountain range. On the south coast of Alaska, in the
region of Mount St. Elias and Mount Fairweather, a recent and
extensive elevation has occurred, which, however, did not bring the
bottom of the adjacent portion of the ocean above the sea-level. This
apparent anomaly seems to be due to an uprising of the rocks along the
north side of a break, or belt of branching fractures, which closely
approximates to the coast-line and has determined the position of the
continental border in that region. The facts, so far as known, appear to
show that we have here what geologists term a fault, the north or
landward side of which has been raised at least 5,000 feet in very
modern times, but, so far as we can judge, without disturbing the
seaward border of the break. The coast between Mount Fairweather and
Mount St. Elias is by far the boldest, and from a scenic point of view
the most impressive, portion of the entire shore-line of North America.
The mountains are young and among the highest on the continent. They
rise precipitously from the margin of the sea, and are sheathed in snow
and ice from base to summit throughout the year.
The margin of the continent southward from Mount Fairweather to the
Columbia River, a distance in a straight line of about 1,200 miles,
furnishes some of the best illustrations of the changes in coastal
geography due to subsidence that our continent affords (Fig. 11). This
wonderfully irregular coast is fringed with a belt of mountainous
islands from 50 to 100 or more miles broad. The inlets between the bold
capes and the straits separating the numerous islands are deep. The
rugged, forest-clothed slopes with precipitous, and in many instances
nearly vertical walls, descend into water that is frequently from 50 to
over 200 fathoms deep. In brief, a deeply dissected mountain range more
than 1,000 miles in length has there been depressed at least 2,000 feet
below its former altitude, thus allowing the sea to flood its deep,
picturesque valleys.
Puget Sound, with its numerous and frequently narrow arms (Fig. 23), is
the southward extension of the partially inundated country considered
above. To the west of this magnificent sound rise the Olympic Mountains,
which barely escape being an island at the present stage of the
swaying of the land. On the west, as on the east border of the
continent, there are drowned river-valleys, such as the Stikine, Frazer,
Columbia, and Sacramento. It is not to be understood, however, that the
entire Pacific coast region has been raised or depressed as a unit.
There have been differential movements in some of its parts, but these
are not as yet well known. In southern California, for example, raised
beaches and a narrow coastal plain about Los Angeles give evidence of a
modern rise of the land.
[Illustration: FIG. 11.--Coast of southeastern Alaska.]
In reference to the broad generalization that the continental mass of
North America has undergone up and down movements, greatest at the north
and decreasing southward, as if moving on a hinge-line running east and
west in the region of the Gulf of Mexico, it is of interest to note that
the ragged coasts of Maine, Nova Scotia, Newfoundland and
Labrador, due to the partial submergence of a rugged land, lie in the
same latitudes as the equally ragged coast of Washington, British
Columbia, and Alaska. This is more than a coincidence. The rocks on the
two coasts are similar, being for the most part resistant crystalline
schists, gneisses, granites, etc., and in each instance stood high above
the sea for a long period during which they were deeply trenched by
streams and by great glaciers, and then at about the same time, as
nearly as can be judged, each region was depressed so as to allow the
sea to encroach upon it.
While a deeply sculptured land when partially submerged gives origin to
a ragged coast, a region of similar elevation, but not cut by streams or
other agencies so as to have deep valleys, when subsidence occurs
produces a bold, harbourless shore without islands. The striking
contrast between the deeply indented border of the continent, with its
broad fringe of islands, from Mount Fairweather southward to Mount
Olympus, and the remarkably uniform although bold coast-line from Mount
Olympus southward to Mexico, and indeed nearly to Cape Horn, has much
significance in this connection.
The mountains bordering the Pacific coast of the United States are among
the younger on the continent. These coast ranges, largely on account of
their youth, have not been deeply sculptured, but rise boldly from the
ocean's shore throughout nearly the entire distance from the Strait of
Fuca to the end of the peninsula of Lower California. The mountains of
Central America, although but little known, are of comparatively recent
date, but differ from the coast ranges in being more largely built of
young volcanic rocks. Both the coast ranges and the mountains of Central
America are much less deeply sculptured than the mountains bordering the
Pacific to the north of Puget Sound, and a subsidence along this shore
would produce but moderate changes in the coast-line. In this great
extent of coast, measuring nearly 5,000 miles, there are but few
harbours; in the portion belonging to the United States the generally
bold coast-line is broken but in two places, one where the
Columbia reaches the sea, and the other where the Sacramento finds an
outlet through the portions of its drowned valley known as the Golden
Gate.
The Bay of San Francisco owes its origin to a subsidence of the land
which has admitted the sea into the valley of the Sacramento, but this
valley, which, uniting with the one at the south drained by the San
Joaquin, forms the Great Valley of California, is not due to stream
erosion, as in the case of the drowned valley of the Hudson or of the
St. Lawrence, but to the upraising of the mountains bordering it. During
a former time of greater subsidence than at present the Bay of San
Francisco was larger than now, and has been contracted both by the
deposition of sediment and by a partial re-elevation of the land. The
exceptional character of the Bay of San Francisco and its marked
excellence as a harbour give to the city on its shore promises of
marvellous development.
The Gulf of California is due, in a general view, to what may be
considered as a departure of the Coast mountains away from the general
trend of the continental border. We have but little detailed information
concerning this region, however, and the studies of modern geographers
have likewise been meagre throughout all the coast-line farther south.
The Pacific coast of Mexico is geographically similar to that of
California, but instead of a single great harbour there are four of
moderate size and excellence, the histories of which have not been
studied. Farther south, along the Central American coast, the shores are
bold, but several indentations, due in part at least to volcanic
agencies, furnish shelter for vessels and offer encouragement to
commerce.
The bold and not deeply sculptured mountains along the nearly unbroken
coast from the Strait of Fuca to Panama, rise close to the true border
of the continent. The continental shelf of this portion of the shore of
the Pacific is narrow. An elevation of 100 fathoms would add scarcely
more than 10 miles to the extent of the land. This narrowness of the
continental shelf seems to be due to the recency of the uplifting
of the Coast mountains, and the lack of time for the _débris_ from the
land and the organic refuse of the sea to shoal the water. The Pacific
basin is deep close to the land bordering it, thus restricting the
seaward extension of the continental shelf.
_Changes in the Coast-Line due to Ice._--It is now well known that
glacial ice many hundreds of feet thick formerly covered the northern
half of North America and flowed outward across the present position of
the coast-line throughout all of the northern border of the continent
from Staten Island in the east and Puget Sound in the west, with the
exception of the Arctic and Bering Sea coasts of Alaska.
The effects of this outward-flowing ice on the topography of the
continental border crossed by it were in general in two directions.
Where the land was rough or moderately so previous to the coming of the
ice-sheets the inequalities of surface were increased; but where the
land was smooth or but gently undulating its elevations were planed away
by the glaciers and made still more smooth. The reason for these
differences is that when the land from which the ice flowed was rugged
or had previously been deeply trenched by streams, the valleys gave
direction to the ice currents and the margins of the continental
ice-sheets became divided into separate ice-streams, as is the case in
Greenland at the present day. This localization of the ice currents
served to deepen and broaden the pre-existing valleys, and especially on
the bold coast of Alaska and British Columbia increased in a marked way
the inequalities of the surface and favoured the production of a ragged
coast-line when the ice melted and was replaced in part by the sea.
When, however, the topography of the land was not sufficiently accented
to cause the ice flowing over it to gather into well-defined currents
the general surface was worn down, thus favouring the production of an
even coast-line after the melting of the ice-sheets.
Where the coast-lands were high and rugged, the deepening and broadening
of the valleys led to the origin of deep, narrow, canal-like waterways
termed fiords (_fjords_), when the ice withdrew from the partially
submerged land or when subsequent depression carried the glaciated
troughs below sea-level. On the Atlantic coast from Maine to Labrador,
and thence northward to the Arctic Ocean, there are numerous examples of
fiords, as is also the case on the Pacific coast from Mount St. Elias to
Puget Sound. At the present time the localized ice-streams from the
great central ice-sheet of Greenland are continuing this process of
fiord excavation. The same is true also, but on a much smaller scale, of
the tide-water glaciers of southern Alaska.
The shores of the northern portion of the continent from New England to
the Aleutian Islands are now being modified by the grinding of
ice-floes, which are driven against the land by the wind. This process,
however, although locally important, need claim but little attention in
a general view of the geography of the continent.
_Changes in the Coast-Line due to the Deposits made by Streams._--The
visible loads of silt and sand in suspension carried to the ocean by
streams, as well as the material the streams roll and push along their
bottoms, is delivered to the waters of the ocean and deposited in
various ways. Much of this material, notably the coarser portion, is
dropped near land and the finer portion floated far out from the coast
before settling to the bottom. Two classes of deposits made in this way
may be recognised, namely, those laid down by the streams themselves as
they drop their loads on entering still water, or delta deposits; and
those spread over the sea-floor by waves and currents after receiving
the _débris_ brought from the land. Which of these two modes of
deposition will prevail depends on whether the waters of the ocean at
the localities where the streams deliver their loads are essentially
still or are affected by strong currents. In the former instance all but
the finer of the _débris_ derived from the land is quickly dropped and
deltas are formed; and in the second instance the currents bear the
material away and deposit it either in the shallow water adjacent to the
neighbouring shore, forming shoals, bars, embankments, spits, etc., or
spread it in a sheet over the sea-floor. The most notable changes
in the coast-line resulting from this general process occur where
silt-laden streams enter still water and form deltas.
On the coast of North America many of the streams which enter estuaries
deliver their loads to waters which are agitated, especially by tidal
currents, and ill-defined shoals, sand-banks, etc., are produced. In
three conspicuous instances, however, large rivers are engaged in
building deltas, and thus producing well-marked changes in the
coast-line.
At the north, the Mackenzie enters the nearly tideless Arctic Ocean,
where floating ice almost completely counteracts the tendency of the
wind to produce currents, and a great delta is being extended seaward.
The river divides on its delta into many _distributaries_ and enters the
sea by several mouths. The sea near the mouths of the river is reported
to be shallow, and obstructed by many sand-banks and islands. No survey
of the Mackenzie delta has as yet been made, and but little definite
information concerning it is available.
The Yukon on entering the shallow eastern portion of Bering Sea, where
the influence of the tides is small and floating ice is present
throughout about nine months each year, is also engaged in building a
great delta which projects into the sea and gives the coast-line a bold
outward curve. The Yukon begins to divide into separate channels,
several of which enter the sea as independent distributaries at a
distance of about 150 miles from the outer border of its delta. The
distance between the outer finger-like division of the stream is about
90 miles. The Yukon is a graded stream--i. e., is able to carry material
in suspension, but not to deepen or fill its channel--in the lower
portion of its course, and is making an important addition to the land
owing to the dropping of its burden of silt as soon as the still water
into which it flows is reached. The stream is thus being extended, and
in order to enable it to continue its task of transportation and the
delivery of its load to the sea, the extended portion of its channel is
built up so as to give a slope down which the waters can
flow--that is, the beds of the distributaries are raised, and they also
shift their positions from time to time and make additions to the entire
surface of the delta. This extension of the stream and deposition of
silt by its distributaries have added about 1,000 square miles to the
land. Although the delta of the Yukon presents an admirable example of
the change in a coast-line produced by the sediment dropped by a great
river, the partial surveys of it that have been made are not as yet
available for study.
Fully as characteristic of the modification of coast-lines made by a
stream as any in the world is the well-known example of the delta of the
Mississippi. This classical instance illustrates not only the manner in
which coast-lines are modified, but the behaviour of a large silt-laden
stream which has reduced its valley to a low gradient, and throughout
hundreds of miles of its lower course is spreading out a wide flood
plain. The extension seaward of this flood plain forms the broad delta
at the river's mouth.
[Illustration: FIG. 12.--Delta of the Mississippi. After United States
Coast and Geodetic Survey.]
During high-water stages the Mississippi widely over-spreads its banks
and during such inundations of its valley drops much of the silt it
previously held in suspension. The material deposited is laid down most
abundantly on the immediate border of its low-water channel. Each side
of the channel is thus raised so as to form what is termed a natural
levee. During this process also the bed of the stream is raised by the
deposition of sediment upon it, thus tending to cause the stream to flow
on a raised ridge and producing an unstable condition which from time to
time enables the river to break across its confining levees and divide
into two or more separate channels. In the lower portion of the river
some of the new channels thus formed reach the sea and furnish
independent outlets for its waters. The first of these distributaries
now departs from the main channel at a distance of 200 miles from the
Gulf of Mexico, and farther seaward several other divisions occur (Fig.
12). The area of the delta is about 1,230 square miles. Each
distributary is engaged in building a pair of embankments, or natural
levees (although this process in recent years has been modified by the
construction of artificial embankments for the sake of improving
navigation), and each subdivision of the river is also building a delta.
Each of the finger-like extensions of the delta, shown on the
accompanying map, is due to the prolongation of a pair of embankments
into the Gulf by each distributary and the growth of a secondary delta
at its mouth. The river is thus building a highly compound delta,
composed of the secondary deltas formed at the mouth of each of its
distributaries. A conspicuous modification of the otherwise generally
evenly curved border of the Gulf of Mexico is thus produced, a result
that could only be reached in a water body but little disturbed by wind
or tidal currents.
ESTUARIES AND HARBOURS
The features of a coast of greatest importance to civilization are its
harbours. A coast without harbours is like a Chinese wall, and tends to
isolate a people inclosed by it. An indented coast with numerous havens
for the shelter of vessels fosters the interests of navigation,
including sea fisheries, invites commerce from other lands, and
stimulates its inhabitants to explore and travel. A diversity of
industries is thus favoured and the people adjacent to an indented coast
with good harbours tend to become more progressive and more cosmopolitan
than if intercourse with other communities is confined to overland
routes.
The Atlantic border of North America is abundantly supplied with fine
harbours, which not only favour communication with distant countries,
but are within easy reach of agricultural and forest lands and important
coal and other mineral deposits adjacent to the coast or in the
interior, and are near extensive and valuable fishing grounds. The best
of these harbours are at the mouths of rivers which have been depressed
so as to form estuaries with wide entrances. These sea-gates, however,
are frequently contracted, owing to the presence of sand-bars and spits
deposited by shore currents.
The great St. Lawrence estuary reaches to Montreal, and beyond lie the
Great Lakes, the rich lands of Ontario and New York, and the now
highly productive States of the Middle West. Two geographical features
in this basin detract from the conditions otherwise highly favourable to
commercial development, namely: the rapids in the St. Lawrence between
Montreal and Lake Ontario and the fall in the Niagara, and the winter
climate of Canada, which causes the rivers and estuaries to be ice-bound
for a considerable part of each year. To obviate the first of these
unfavourable conditions far-reaching plans for a deep waterway between
the Great Lakes and the Atlantic are now being matured. The splendid
harbours from Nova Scotia southward are never seriously obstructed by
ice, and south of Virginia ice is practically unknown.
The estuaries at the mouth of the Hudson, Delaware, Susquehanna,
Potomac, James, and the Alabama, together with the distributaries of the
Mississippi (which is not a partially drowned river, but one that is
building up and extending its channel), are the natural outlets of
portions of the continent of great fruitfulness. When other, and
especially climatic, conditions are considered, it will be seen that to
the geographer the Atlantic sea-border from the Gulf of St. Lawrence to
the Gulf of Mexico seems destined to be the next great commercial centre
in the succession from Greece to Britain. An important adjunct to the
present highly favourable geographical conditions pointing to a great
future for civilization on the Atlantic coast is the construction of a
ship-canal across the isthmus uniting North and South America. This step
must soon be taken.
A glance at a map of North America must impress one with the belief that
the Pacific coast with its great extent of harbourless water-front is
far less favourable to the growth or ideas, institutions, and industries
than the deeply indented Atlantic shore-line. From the Isthmus of Panama
to the State of Washington there is, as we have seen, but one harbour of
the first class, the estuary of the Sacramento, and one of the second or
third class, the estuary of the Columbia. From Puget Sound northward
harbours are numberless. There are two important geographical reasons,
however, why the general absence of good harbours to the south of
Puget Sound is not so serious as it perhaps might seem. First, the
mountain ranges run north and south parallel with the coast, and the
natural lines of interior travel lead to the outlets through the Coast
Ranges traversed by the Sacramento and the Columbia. The second and more
general reason is that, owing to the warm currents in the Pacific, the
portion of the west coast most favourable for a high degree of
civilization is situated farther north than the similar belt on the
Atlantic border.
* * * * *
By way of a summary of this chapter, the reader is asked to bear in mind
the fact that the land forming North America, as is the case with all
continents, is not at rest, but is subject to movements which cause
elevations and depressions of various portions of its area with
reference to sea-level. These movements have been in progress since the
birth of the continent, and still continue. An upward movement of the
earth's crust where the land and ocean meet causes a portion of the
sea-floor to emerge and an addition usually of the nature of a coastal
plain to be made to the border of a continent; while a reverse movement
enables the sea to advance on the land and to flood the low-grade
valleys opening to the ocean.
In a generalized view of the recent history of the coast-line of North
America the dominant fact is that to the north of the latitude of the
north shore of the Gulf of Mexico the resultant of the later movements
of the continent is downward; the amount of the depression thus caused
increases in a general way with increase in latitude on both the
Atlantic and Pacific coasts. This downward movement has permitted the
sea to encroach on the land and to flood many pre-existing valleys. On
the Atlantic coast it produced such estuaries as Chesapeake and Delaware
Bays, the tide-water portions of such rivers as the Hudson and the St.
Lawrence, and farther north, where the submergence was greater,
permitted the sea to invade the continental basin and form Hudson Bay.
To this same wide-reaching cause is due also the bold ragged coast-line
of the Atlantic from New England northward. On the Pacific border
the downward movement is recorded by the tide-water portions of the
Sacramento, Columbia, etc., and the deep picturesque fiords of the
Canadian and Alaskan coasts. The most decided influence of these changes
in the geography of the continent's margin on the affairs of men
resulted from the production of numerous fine harbours and the extension
of estuaries far inland, thus favouring commerce and fisheries in a high
degree.
As a result of the oscillations just referred to, the sea has gained
important characteristics as well as the land. The broad submerged shelf
fringing the continent furnishes conditions highly favourable to both
plant and animal life, and affords some of the most valuable
fishing-banks of the world.
The Caribbean region is a marked exception to the broader changes that
have affected the coast-line throughout the central and northern
portions of the continent, and stands by itself as a conspicuous
illustration of more localized earth movements which produced a
remarkable submarine topography.
LITERATURE
In continuation of the studies outlined in this chapter the following
books, most of which contain more special references, will be found of
assistance:
AGASSIZ, A. _Three Cruises of the Blake._ 2 vols. Houghton,
Mifflin & Co., Boston, 1888.
GILBERT, G. K. _The Topographic Features of Lake Shores._ In
United States Geological Survey, Fifth Annual Report, 1883-'84,
pp. 69-123.
GULLIVER, F. P. _Shoreline Topography._ In Proceedings of the
American Academy of Arts and Sciences, vol. xxxiv, 1899, pp.
151-258. Contains a valuable bibliography.
HILL, R. T. _The Geological History of the Isthmus of Panama and
Portions of Costa Rica._ Bulletin of the Museum of Comparative
Zoology at Harvard College, vol. xxviii, 1898, pp. 151-285.
HILL, R. T. _Cuba and Porto Rico with the Other Islands of the
West Indies._ The Century Co., New York, 1899.
SHALER, N. S. _Seacoast Swamps of the Eastern United States._ In
United States Geological Survey, Sixth Annual Report, 1884-'85,
pp. 353-398.
SHALER, N. S. _The Geological History of Harbors._ In United
States Geological Survey, Thirteenth Annual Report, Part II,
1891-'92, pp. 93-209.
SHALER, N. S. _Sea and Land._ Scribner, New York, 1894. _United
States Coast and Geodetic Survey._ Annual Reports, Coast Pilot,
Tide Tables, etc.
CHARTS AND MAPS
To the student of the geography of the coast and submerged border
of North America, the extensive series of charts published by
the _United States Coast and Geodetic Survey_ supply a vast
amount of accurate information. A catalogue of these charts,
with prices, etc., is issued by the Survey. Many of the charts
issued by the _United States Hydrographic Office_, and a large
number of the topographic maps published by the _United States
Geological Survey_, are of value in this same connection. An
account of these charts and maps, with instructions as to
methods of obtaining them, etc., is given in _Government Maps
for Use in Schools_, by Messrs. Davis, King, and Collie,
published by H. Holt & Co., New York, 1894.
CHAPTER II
THE TOPOGRAPHY OF THE LAND
Taking the better known portions of North America as a basis on which to
classify the leading geographical features of the continent, it is
convenient, and in the main sufficiently accurate, to recognise five
primary physiographic provinces. These are, in their general order, from
east to west:
1. Coastal plains and plateaus, of which the country between the
Atlantic Ocean and the Appalachian Mountains furnishes the most typical
examples.
2. A series of mountain ranges embracing all of the more elevated
country on the east side of the continent from Georgia northward to the
arctic archipelago, and in this book termed the _Atlantic Mountains_.
3. The great system of plains and plateaus extending from the Gulf of
Mexico northward to the Arctic Ocean and bordered on the east by the
Atlantic Mountains and on the west by a still greater series of
mountains, which may be designated with sufficient accuracy as the
_Continental Basin_.
4. A group of mountain chains and mountain ranges on the west side of
the continent, including the Rocky Mountains, Sierra Nevada, Cascades,
etc., and sometimes termed the Cordilleras. Under the scheme of
classification here used, this highly complex belt of rugged country
extending from south-central Mexico northward to the Arctic Ocean is
termed the _Pacific Cordillera_, or, in less technical language, the
_Pacific Mountains_.[1]
[1] The propriety of using the names here employed for the larger
physiographic provinces of North America has been discussed by several
writers in the _Bulletin of the Geographical Society of Philadelphia_,
vol. ii, 1899, pp. 55-69.
[Illustration: FIG. 13.--The larger physiographic divisions of North
America.]
Each of the four physiographic provinces briefly described above is in a
conspicuous manner elongated in a north and south direction. The
mountains, valleys, and plateaus, as well as the controlling lines of
structure in the rocks below the surface, throughout the main body of
the continent coincide in direction more or less nearly with the
parallels of longitude. At the south, however, and crossing the trend of
each of the provinces named above, is the:
Fifth, or Caribbean province, which includes the West Indies, the
southern part of Mexico, and all of Central America. In this
province are the _Antillean Mountains_, now mostly submerged, the
principal axes of which trend east and west.
With this brief outline of the larger physical divisions of North
America in mind, let us endeavour to become acquainted with the leading
characteristics of each of the provinces as they exist to-day, and at
the same time learn something of their long and varied histories.
COASTAL PLAINS AND PLATEAUS
_The Coastal Plains._--From New York to Key West and thence about the
borders of the Gulf of Mexico to the neighbourhood of Vera Cruz, the
border of the present land area of the continent is formed by a low
plain, from 30 to 50 miles broad in New Jersey, but increasing in width
southward to Georgia and Florida, where its somewhat indefinite inland
margin is more than 100 miles from the sea, and reaching its greatest
development in the delta of the Mississippi. Extending southward about
the west coast of the Gulf, it forms the low, featureless eastern border
of Texas, about 50 miles broad, and passes into Mexico, but gradually
narrows as the Pacific Mountains approach the coast, and ends in the
vicinity of Vera Cruz.
The Atlantic and Gulf coastal plain everywhere slopes gently seaward,
and on its landward margin has an elevation in general of from 200 to
300 feet. The character of the material of which the coastal plain is
composed, the fossils contained in it, as well as its geographical
features, show that it is a continuation of the continental shelf, and
was formed at a time when the border of the continent was more deeply
submerged than at present. Minor oscillations of the earth's crust have
time and again allowed the sea to extend inland, only to be forced to
recede when the land again rose. Each invasion of the sea left a sheet
of soft sediment over the portion of the land that was submerged. These
oscillations are still in progress, as is indicated by the fact that
along the New Jersey coast a downward movement at the rate of about 2
feet per century is taking place. A similar depression of the land
is also thought to be in progress along the south Atlantic coast and in
the delta of the Mississippi. The Atlantic coastal plain has its most
characteristic development in South Carolina, and is roughly divisible
according to its topography and soil into several belts parallel with
the shore-line. At the same time it is transversely divided into strips
by the several rivers which flow across it and by the many branches of
these rivers originating on the plain itself.
The junction of the portion of the gently sloping border of the
continent now above sea-level, with the submerged portion, is
characterized by the presence of a belt of swamps, in part marine
marshes where the salt water ebbs and flows, and in part fresh-water
morasses in which the drainage is obstructed largely by decaying
vegetation. Inland from the coastal swamps the surface becomes higher,
is for the most part well drained, and when not too sandy furnishes rich
agricultural lands. The Atlantic plain as a whole thus has three
principal divisions: a submerged portion, a marsh portion, and a
subaerial portion. During past ages the position of each of these belts
migrated, owing to movements in the earth's crust, but their succession
in reference to each other has been the same since the Tertiary period.
One of the most typical portions of the fringe of swamps now bordering
the land is situated in eastern Virginia and North Carolina, and is
known as the Dismal Swamp. In the central portion of this marshy region,
embracing some 700 square miles, lies Lake Drummond, an example of a
large number of small fresh-water lakes which are retained by rims
composed of plant growths and decaying vegetable matter. The mound of
vegetable _débris_ in the summit of which Lake Drummond is situated is
from 20 to 30 miles broad and rises some 12 feet above tide-level. The
lake is nearly circular, from 2 to 2½ miles in diameter, and from 6
to 10 feet deep. The water is amber-coloured on account of the vegetable
matter in solution, but is clear and without sediment in suspension, and
is considered as remarkably wholesome. The lake was without definite
outlet previous to the cutting of drainage-canals, and is entirely
encircled by a dense forest, which has encroached on its border in such
a manner as to render its boundaries indefinite. The wall of rank
vegetation surrounding the open waters of the lake marks the beginning
of the encircling swamp. Standing in the lake and supported by their
widely expanded roots are several aged cypress-trees.
Along the coast of the Carolinas and Georgia sand-bars thrown up by the
sea have formed many lagoons (Fig. 6), which are being filled by the
wash of detritus from the land, by sand blown from their confining
ridges, and by vegetation and the hard parts of molluscs, crustaceans,
etc., living in their waters. In part, these areas have been converted
into swamps, and are gradually being transformed into dry land. Farther
southward, about the shores of Florida, and thence along the Gulf
border, the low, indefinite margin of the coastal plain is fringed in
many places by dense thickets of mangrove-trees, which extend their
aerial roots into the salt water, and by retaining sediment and dead
vegetation as well as by furnishing conditions favourable for animal
life, lead to a gradual extension of the land.
The west border of the coastal plain from New York southward to central
Georgia is at the junction of the soft, unconsolidated sands and clays
of the emerged portion of the continental shelf, with hard and usually
crystalline rocks of great geological age forming, an upland known as
the Piedmont plateau, which extends westward to the base of the
Appalachian Mountains. The sharply defined boundary between the plain
and the plateau is termed the _fall line_, for the reason that it is
marked by the lowest falls and rapids in the streams flowing eastward
from the Appalachian Mountains. Throughout the courses of these streams
to the west of the fall line they are shallow and swift and broken by
many picturesque rapids, while to the east of the fall line they broaden
in the soft sediments of the coastal plain, and are deep, placid streams
which widen into estuaries. The influence of the tides is felt in these
drowned rivers to the fall line. The most important fact in this
connection is that the lower courses of the larger rivers, such as
the Delaware, Susquehanna, Potomac, James, etc., are navigable for
ocean-going vessels, while their upper courses to the west of the fall
line are difficult to traverse even in canoes.
[Illustration: FIG. 14.--Relief map of North America. After United
States Geological Survey and Canadian Geological Survey.]
The fall line is thus the head of navigation in a number of rivers, and
for this reason it has determined the sites of several important cities.
Its course is marked by Trenton, Philadelphia, Baltimore, Washington,
Richmond, Weldon, Raleigh, Augusta, and Macon. Farther south, about the
landward margin of the portion of the coastal plain bordering the Gulf
of Mexico, the fall line is less distinct, largely for the reason that
the rocks bordering it on the north and west are less resistant than
those forming the plateau at the east base of the Appalachians.
Exceptions to the fact that the coastal plain is composed mostly of soft
sediments occur in southern Florida and in Yucatan, where coral rock has
been upraised. Southeastward from Yucatan a coastal plain is wanting and
rocky bluffs separated by stream-cut valleys come boldly down to the
surf line. Partially drowned valleys on each side of Central America
bear record of a recent but moderate downward movement of the land.
From New York northward along the border of the continent the coastal
plain is mostly lacking, or if recognisable, is greatly modified by
glacial deposits, and the Piedmont plateau, as it is known farther
south, swings eastward and becomes a coastal plateau with a more or less
roughened surface, which extends northward to Labrador and the Arctic
Ocean.
The geologically recent oscillations of the continent, as stated in the
preceding chapter, have been greatest in high latitudes, where the last
movement, as there are reasons for believing, was upward and is still
continuing. This rise, although it has not fully counteracted the
changes produced by a preceding downward movement, has caused the
shore-line to recede and a great area on the arctic border of the
continent which was previously submerged has thus become exposed. The
coastal plain on the west side of Hudson Bay, as described by T. B.
Tyrrell, is about 50 miles wide in the vicinity of Fort Churchill,
latitude 55°, and broadens rapidly northward of that locality. In
latitude 64° the boundary between these new lands and the older plains
of the interior is about 300 miles from the present shore; thence
northwestward it has not been traced, but may be expected to cross the
Mackenzie some 250 miles from its mouth and pass westward into Alaska.
This arctic coastal plain is known in part as the Barren Grounds, but in
general may be designated as a _tundra_, as over extensive areas it is
similar to the still greater tundras of Siberia. This tundra forms the
extreme northern and northwestern border of the continent in arctic
Canada and northern and northwestern Alaska, and although but
imperfectly explored, has a length of probably 2,000 miles and a width
of from 50 to 60, and in places of over 100 miles. On the west coast of
Hudson Bay the tundra region slopes gradually from 500 to 600 feet above
the sea down to the present coast, and is traversed by sand and gravel
terraces and beaches or ridges which mark the former positions of the
sea margin. The lower ridges referred to are thickly strewn with shells
of molluscs belonging to species still living in the adjacent ocean
waters, thus indicating the recency of the emergence of the land. This
arctic coastal plain has the same general geographical features as the
coast plain on the southern Atlantic and Gulf border of the continent;
but, owing mainly to different climatic conditions, differs from its
southern representative in nearly every detail.
The tundra may be briefly defined as a vast frozen morass. The dense
mat-like vegetation consists principally of mosses and lichens (but not
noticeably of _Sphagnum_ or peat-moss, as is sometimes stated), and
during the short and not infrequently hot summers is beautified by a
multitude of low flowering herbaceous plants. Trees are absent, except
along the inland border, where the tundra merges with the subarctic
forest. To the north, or seaward from the isolated groves of stunted
spruce-trees marking the "continental timber-line," the only
representative of arboreal vegetation is usually the slim osier-like
arctic willow which grows in sheltered localities and attains a height
of 3 to 5 feet. Near the streams there are in some localities broad
areas covered with dark-green meadow-like growths of rushes
(_Equiseta_). The luxuriant flowering plants spring into existence
as if by magic as soon as the winter's snow melts, and under the warmth
and light of the nightless arctic summer grow with wonderful rapidity.
In winter the tundra is snow-covered, but the snow is less deep than in
more humid regions, and the cold is intense. The bog becomes deeply
frozen, and is not completely thawed during the succeeding summer. Even
in midsummer, when the surface is a luxuriant garden of flowers and
fresh gray-green moss, ice exists a foot or two beneath the luxuriant
carpet and extends to a great but unknown depth. Excavations made in
Alaska have shown that the perennial, dirt-stained ice beneath the
tundra is at least 25 feet thick, but this is by no means its maximum
depth. On the shore of Eschscholtz Bay and along the Kowak River
sections of the tundra exposed in cliffs indicate a thickness of 150 to
300 feet of ice, covered by a thin layer of black peaty soil. The
similar region in Siberia, as shown by borings, is known to be
permanently frozen to a depth of 380 feet deep. The subsoil ice is
sheltered by the vegetation and the peaty soil resting on it, from the
heat of the short summers, and the part softened by the summer's sun is
refrozen during the long intensely cold winters. It is probable that
under the present climatic conditions a sheet of perennial ice would be
formed beneath the tundra, but the suggestion that the ice now present
is in part an inheritance from a former period of greater cold is not
without support. The vegetation of the tundra grows each year at the
surface, while the partially decayed material below is frozen and
preserved. This increase in depth of the vegetable matter is much the
same as the growth of peat in temperate latitudes, except that the
partially decayed material is preserved in cold storage. It was in the
tundra of Siberia that the completely preserved bodies of the mammoth
and the woolly rhinoceros have been discovered. Similar finds are to be
looked for in the tundra of North America, where the bones of these
animals have already been found.
On the Pacific border of the continent the shores are mostly bold, and
coastal plains comparable with those on its eastern and northern
margins are absent. In southern California, however, in the vicinity of
Los Angeles, a modern and apparently local elevation of the land has
produced a highly fertile plain, now, owing to the magic touch of
irrigation, beautified by gardens and orchards.
_The Piedmont and Coastal Plateaus._--Adjacent to the western margin of
the Atlantic coastal plain, and extending from Alabama northward to New
England, there is a plateau region about 150 miles broad in its central
part, but narrowing towards its extremities so as to be from 40 to 60
miles broad in Maryland and New Jersey, and of about the same width at
the south, in Georgia. The slope of the plateau surface is seaward from
an elevation of about 1,000 feet along its western margin to 250 or 300
feet at the fall line where it joins the coastal plain.
From its position at the foot of the Appalachian Mountains this
moderately elevated plain is termed the Piedmont plateau. The same
plateau extends northeastward, however, where it is known as the New
England plateau, and is without any definite boundary to separate it
from the similar region in the maritime provinces of Canada. While local
divisions of this great extent of moderately elevated plateau country
are recognised, yet in a general view of the continent it is evident
that the Piedmont plateau, the New England plateau, and the similar
region, mostly of crystalline and igneous rocks, extending from Maine to
Hudson Strait and beyond, in reality forms a single great geographical
unit in which the geological structure and geographical features are
much the same. The general history of this great Atlantic plateau, as it
may, perhaps, be termed, shows that it consists mainly of metamorphic
rocks, such as mica schist, gneiss, slates, etc., together with granite
and other igneous rocks, and, to a minor extent, of sandstones, shales,
and limestones, mostly of Jura-Trias and Carboniferous age. These rocks
were upraised probably in part into lofty mountains, and then worn down
by erosion nearly to sea-level, thus forming what is termed a
_peneplain_, or a plain of subaerial denudation. It is not intended by
this statement to imply that all of the Atlantic plateau was ever
a single great peneplain, but the same general history seems to apply to
the entire region. The upheaval of the plains produced by erosion gave
the streams greater energy, and they have begun the task of again
reducing the land to sea-level, but have not as yet broadened their
valleys so as to greatly modify the general plateau character of the
region they traverse. The softer or more easily soluble rocks have been
eroded away, leaving broad valleys, as in the several instances where
sandstones and shales of what is known as the Newark system (Jura-Trias)
occur in detached areas from South Carolina to Nova Scotia. Then, too,
from northern New Jersey northward to Labrador and beyond, great
glaciers have crossed the plateau or developed upon its broad north
portion and have ground down its surface or left widely extended hills
and ridges of morainal material upon it.
Where the process, just referred to, of planing down a tract of country
nearly to sea-level is incomplete and remnants of former uplands still
remain as isolated hills or groups of hills, such inheritances from the
pre-peneplain stage may still exist when the region is elevated into a
plateau and give diversity to its surface. An example of such a residual
hill is furnished by Mount Monadnock, in southern New Hampshire, and, as
proposed by W. M. Davis, the name of this old landmark is adopted as a
technical term by which to designate all similar remnants of old uplands
left standing on a peneplain. On the Atlantic plateau there are many
_monadnocks_. They range in size from well-characterized hills to
mountain-like forms, and may be isolated or occur in groups. When a
monadnock stands alone its history may be easily read, but groups of
such eminences, especially when of large size, become ranges of hills or
even mountains, and may preserve so much of their former characteristics
that they outrank the adjacent peneplain and become the dominant
geographic feature of the region to which they give diversity. Such a
passage from monadnocks to mountains seems to be furnished by the
numerous isolated hills on the Atlantic plateau and the mountains of New
England and of eastern Canada.
The most characteristic portions of what has just been termed
provisionally the Atlantic plateau are the Piedmont plateau, which
skirts the east base of the Appalachian Mountains from New York to
central Alabama and the Labrador plateau. The eastern border of the
Piedmont plateau is determined by the fall line described above, where
the hard crystalline rocks of the Piedmont region meet the softer rocks
of the Atlantic coastal plain. The rivers flowing eastward from the
Appalachian, such as the Delaware, Susquehanna, Potomac, and the James,
cross the Piedmont plateau in well-defined but narrow channels, usually
from 100 to 200 feet deep, leaving the interstream spaces with generally
level surfaces, although etched as it were by the lateral tributaries of
the master streams. These rivers are shallow and rapid in their courses
across the plateau, or in somewhat technical geographical language are
not as yet graded, but on crossing the fall line become sluggish
tide-water streams which widen into estuaries, as already described.
Owing to the warm humid climate of this region, the rocks in the
interstream spaces are usually deeply decayed and furnish clay soils
which have characteristic red and yellow colours. Much of the cotton and
tobacco of the South Atlantic States is grown on these residual soils
which were left as the more soluble portions of the rocks were removed
in solution.
Labrador, although in great part unexplored, is known to present the
characteristic features of an irregular plateau, with a general
elevation of 1,500 to 2,000 feet above the sea. The surface is
undulating and has hills and hollows, the latter frequently holding
lakes and swamps, but the inequalities seldom exceed 500 feet in
vertical range. Although the western boundary of the Labrador plateau is
indefinite, its area may be taken at about 500,000 square miles. In its
western part, and apparently rising from the plateau as a group of
residual hills left by erosion, are the so-called Laurentian or
Laurentide Mountains. The eastern border of the plateau forms the bold
and excessively rugged Atlantic coast-line of Labrador, characterized by
steep cliff with a fringe of small rocky islands. The adjacent sea
is deep and the continental shelf narrow. On the south the plateau is
bordered by a series of terraces which lead down to the St. Lawrence
River and on the west it merges indefinitely with the plains of the
continental basin.
The rocks of Labrador are largely metamorphic, but include ancient
igneous intrusions, and are hard and resistant. The present surface is
the result of deep erosion which has removed a great but unknown
thickness of material and left exposed what was once the deeply buried
basal portion of a mountainous region. This is a part of the oldest
known land of the continent, and, so far as can be learned, has never
been covered by the sea since a very ancient geological period. In
addition to the long eras of erosion, during which the _débris_ removed
was deposited in part farther south, and contributed to the formation of
the stratified rocks of the Appalachian region and interior continental
basin, there was a comparatively recent extension of great glaciers over
the plateau which removed the previously disintegrated and decayed rocks
and left the present bare, rounded, and generally subdued hills with
intervening basins. The soils are thin, for the reason that under the
present climatic conditions rock decay is retarded, and are confined
principally to the depression where peaty material has accumulated.
Owing to the lack of soil on the uplands, the excess of water in the
hollows, and to the severity of the climate, the forest is not
continuous, the trees are small, and the vegetation generally of a
subarctic character. This vast region is without agricultural
possibilities, and thus far has been of value to man almost solely on
account of its fur-bearing animals and the fisheries of its coast.
The northern border of the Atlantic plateau cannot at present be
accurately defined. Seemingly it should include the Arctic archipelago,
which provisionally may be considered as a deeply dissected plateau
region, at present less elevated than formerly, thus allowing the sea to
enter the valleys and to transform old uplands into islands. The bold
and highly instructive explorations conducted in recent years by
Robert Bell, for the Canadian Geological Survey, have shown that in the
region adjacent to Hudson Strait the plateau features characteristic of
the greater part of the Labrador peninsula are absent and mountains
occur which rank as the highest on the eastern border of the continent.
On the Pacific coast plateaus corresponding closely with those adjacent
to or bordering the Atlantic are wanting. What geographers recognise as
deeply dissected plateaus, so extremely rough that they pass for
mountain ranges, do occur on the western border of the continent,
however, and will be described later.
THE ATLANTIC MOUNTAINS
This title will no doubt appear novel to many persons, and is, perhaps,
open to adverse criticism, but it serves to unite in one group all of
the mountains in the eastern half of North America. A cordillera, as
usually defined, consists of two or more mountain chains associated
geographically, but not necessarily of the same age. On the Atlantic
border of the continent we have an example of such a family of
mountains. The Atlantic mountains, although comprising ranges, systems,
etc., of widely different ages, are all geologically old, and have
resulted from upheavals along two generally parallel and slightly
overlapping northeast and southwest belts adjacent to the Atlantic
Ocean. The growth of this group of mountains is believed to have been
from the north southward, and several periods of upheaval have been
recognised.
The two main divisions or chains referred to are separated by the valley
of the St. Lawrence. The mountains at the north are known as the
Laurentides or Laurentian Highlands, and those at the south comprise the
mountains of New Brunswick and Maine, the White Mountains of New
Hampshire, the Green Mountains of Vermont, the Adirondack Mountains of
northeastern New York, and the Appalachians. The most convenient method
of reviewing the characteristics and histories of these several uplifts
is to begin with the Appalachians, which are at the same time the
most important and best known, and consider them in their order from
south to north.
[Illustration: FIG. 15.--Appalachian Mountains.]
_The Appalachian Mountains._--This beautiful and frequently exceedingly
picturesque series of long, narrow ridges separated one from another by
trough-like valleys, constitutes a mountain system some 900 miles long
and 50 to 130 or more miles wide (Fig. 15). The truly mountainous
portion in its widest part, in western North Carolina and eastern
Tennessee, is about 70 miles across, but a portion of the adjacent
plateau on the west partakes of the same structural features and is a
part of the Appalachian uplift. The system is considered as extending
from the Hudson southward to central Alabama and central Georgia. At the
north its terminus is indefinite, as it merges with the highlands to the
east of the Hudson and with the Berkshire Hills of Massachusetts, which
in turn are not strictly separable from the Green Mountains of Vermont.
At the south, the system ends somewhat abruptly where the crystalline
rocks comprising its southern terminus pass beneath the soft sediments
of the coastal plain. The eastern border of the system is well defined
by its junction with the Piedmont plateau, but on the west it merges
through a series of lessening folds with the plateaus and plains of the
eastern border of the interior continental basin. The Alleghany plateau,
which skirts the western border of what is usually recognised as the
Appalachian Mountains, but which is really its moderately disturbed
border, extends from the Hudson to Alabama, and in its various portions
is known by distinct names. Its northern extension overlooking the
Hudson forms the Catskill Mountains; farther south it becomes locally
the Alleghany plateau, and still farther south the Cumberland plateau.
Separating the bold eastern escarpment of this series of plateaus from
the generally higher mountains to the eastward lies the great
Appalachian Valley, which under various names extends from the Hudson to
central Alabama. This important and highly fruitful valley is underlaid
to a great extent by thick bedded limestones and soft shales, and owes
its existence to erosion and largely to the removal of limestone
in solution.
The Appalachians are nowhere lofty, and only approach the
characteristics of great mountains in their southern portion. The
culminating summit is Mount Mitchell, in western North Carolina, which
has an elevation of 6,711 feet. Roan Mountain, 27 miles to the northward
of Mount Mitchell, rises 6,287 feet above the sea. In the neighbouring
Unaka and Great Smoky Mountains, to the southwest and west of Mount
Mitchell, there are many boldly rounded domes ranging in height from
5,000 to over 6,000 feet Northward of the highly picturesque southern
Appalachians, the system decreases in height and is really a deeply
dissected plateau, as will be shown later, in which the long,
even-crested ridges have a general elevation of 4,000 feet in Virginia
and about 2,000 feet in Pennsylvania and New Jersey. At its northern
extension in New York it decreases still more in height, and is
surpassed in elevation by the plateau on the west, there represented by
the Catskill Mountains, the highest portion of which is 3,660 feet above
the sea.
The characteristic structural feature of the Appalachians is the
presence of a great series of up and down folds, or anticlinals and
synclinals as geologists term them, which run in a nearly parallel
northeast and southwest direction, but in Pennsylvania especially
exhibit many broad curves in their general course. These folds are
similar to the waves that may be produced in a heavy rug or carpet by
pressing against one of its margins. The rocks have been thrown into a
series of great wrinkles which are not continuous throughout the length
of the system, but as one dies out another takes its place. The folds
overlap at the ends or are arranged _en échelon_. The longer axes of the
folds are seldom horizontal, but have usually a gentle pitch; for this
reason one end of a fold frequently passes beneath the surface, while
the other end is exposed to erosion. Another characteristic is that the
anticlinals, as a rule, are steep on their western margins, and slope
more gently on their eastern flanks, or are unsymmetrical. The
overturning of the folds where most pronounced has led to the
breaking of the rocks on the west side of an upward wrinkle where the
descending limb of an anticlinal is sharply bent in order to pass into
the ascending limb of the adjacent synclinal. These breaks or faults in
certain instances form thrust planes along which one portion of a series
of beds has been carried westward, sometimes for several miles, over
another portion of the same series. This highly characteristic system of
unsymmetrical folds, passing at times, and especially in Tennessee and
Alabama, into great thrust planes, is accounted for on the general
theory that there has been lateral pressure or a tangential thrust,
which has forced the strata into a series of elongated arches, in much
the same manner as in the case of a rug, as above suggested, one margin
of which has been forced by lateral pressure towards its central part.
The rocks composing the greater portion of the Appalachians are
stratified marine sediment such as sandstone, shale, limestone, etc.,
which were laid down one on another until a great depth was attained,
corresponding, as we may fancy, to a pile of rugs, the original
thickness in Pennsylvania being about 40,000 feet. Lateral pressure
resulting, as it is believed, from the cooling and consequent
contraction of the earth's highly heated interior, and the movement of
the cool and rigid crust in order to keep in contact with the shrinking
mass beneath, has led to the folding and occasional breaking of the
rocks, which at the same time were elevated above the sea. A crushing
together or folding of the rocks similar to that which has taken place
along the central part of the Atlantic border of North America, as is
well known, has occurred also in many other regions, and the
Appalachians may be taken as the type of a class of mountains, sometimes
termed corrugated mountains, which includes the Alps and Pyrenees, the
Coast Range of California, etc. For convenience we may speak of such
mountains as being of the Appalachian type.
Had the folding in the Appalachian region gone on without erosion, the
surface would to-day be a series of great, elongated arches or
upward folds, rising in many instances 5,000 or more feet above the
intervening valleys, and where breaks or faults occur their upraised
borders would stand as mighty cliffs, in some localities a mile or more
high. The central part of the region with this strange topography had
there been no erosion would, perhaps, be fully as prominent as the
Himalayan Mountains are at present. No sooner, however, were the
Appalachian Mountains upraised above the sea than the destructive
agencies of the atmosphere began their attacks upon them. The rocks were
shattered by changes of temperature, and at times at least crumbled by
the freezing of absorbed water and also underwent chemical changes which
softened and disintegrated them. The rains beat upon them, and streams
flowing to the sea cut channels and carried away the material forming
the land. These processes of disintegration and erosion have been in
progress since islands and continents first appeared on the earth, and
every mountain range now giving diversity to the surface of the land
represents the net result of elevation over denudation. The Appalachians
are not an exception, but a typical illustration of this general law.
The great folds of which they are composed have been truncated by
erosion and the surfaces thus produced, etched, as it were, by the
action of the air, rain, and by streams, so as to leave the edges of the
more resistant layers in relief.
One conspicuous result in this general process of erosion is due to the
fact that the folded strata consist in many instances of alternating
hard, or insoluble and soft, or readily soluble layers. Where resistant
layers underlaid by soft, or readily soluble strata formed the summits
of arches they have in many instances been broken in the process of
folding or cut through by streams flowing down their flanks and the weak
beds beneath exposed. After this stage was reached the erosion of the
upward folds went on more rapidly than the removal of rock from the
compressed downward folds, so that what is structurally a ridge became a
valley: while the bordering troughs or synclinals floored with hard
layers were left in relief as ridges or table-lands. The anticlinal
ridges have thus been transformed into topographic valleys and the
original synclinal troughs left in relief as plateaus and ridges.
[Illustration: FIG. 16.--Section of anticlinal valleys and synclinal
mountains.]
This reversion of what would have been ridges and troughs had there been
no erosion, is illustrated by the following cross-section through
Lookout Mountain in Alabama, which is an example of what is known as a
synclinal mountain. Many such synclinal mountains or plateaus, separated
by narrower anticlinal valleys, occur throughout the Appalachians.
The characteristics in the present topography of the Appalachians just
considered are but a minor portion of the great changes that have
resulted from erosion. The history of the system has not been the same
in this connection throughout, but retains evidences of successive
upward movements with long periods of erosion intervening which have
produced certain striking differences in its northern and southern
portions. These differences are so well marked that it is convenient to
divide the system into two portions, termed the northern Appalachians
and southern Appalachians. The most conspicuous difference between the
two is shown by the direction of flow of the larger rivers. At the
north, the principal rivers--the Delaware, Susquehanna, Potomac, and
James--rise well to the west of the mountains and flow southeast athwart
the numerous folds, and after crossing the Piedmont plateau and coastal
plain discharge into the Atlantic. At the south, however, the rivers,
particularly New River and the Tennessee, rise on the eastern border of
the Appalachians and flow westward, cutting through the Alleghany
plateau, and are tributary to the Mississippi and the Gulf of Mexico.
The somewhat arbitrary dividing line between these two provinces
follows the divide to the north of New River, or in a general way, as
has been stated by C. W. Hayes, is marked by a line drawn from the most
easterly point of Kentucky southeastward to Cape Fear, on the Atlantic
coast.
The fact that several large rivers rising to the northwest of the
northern Appalachians flow directly across or through the numerous
ridges composing the system in deep, narrow valleys, and the similar
behaviour of the streams rising on the eastern border of the southern
Appalachians, but flowing westward, are among the most interesting
features of the entire region. Why is it that the mountains have not
formed a divide or water-parting so as to force all of the streams
having their sources on its west side to take what would seem the easier
course, and to flow to the Gulf of Mexico, and cause the waters falling
on its eastern slopes to flow to the Atlantic? The answer to this
apparently puzzling question has been furnished by Davis, Willis, Hayes,
Campbell, and others, who have shown that the mountains were not raised
all at once, but experienced upward movements at widely separated
intervals, with intervening periods of rest during which the elevations
previously produced were more or less completely planed away by erosion.
During one of these intervals the north Appalachians more especially
were worn down to approximately sea-level and a gently sloping plain
produced across which the larger rivers flowed to the Atlantic. This
peneplain was later upraised into a plateau and its downward inclination
towards the east increased. The streams were thus given greater energy
and began again to deepen their channels. They held their right of way
acquired on the featureless erosion plain and cut deep trenches through
the edges of the hard layers which crossed their courses. At the same
time lateral branches were developed which followed the outcrops of the
less resistant beds and eroded them away so as to leave the hard beds in
bold relief. As the edges of the more resistant beds became more and
more prominent the eastward-flowing streams cut deeper and deeper into
them. The even summits of the ridges, one of the most striking
features in the beautiful scenery of the Appalachians, still mark the
position of the elevated erosion plain.
In the southern Appalachian the old erosion plain formed nearly at
sea-level was tilted gently westward, and the streams flowing over its
surface given initial courses in that direction, which were maintained
as they deepened their channels, and on account of increased energy
originating from the upraising of the region drained by them, developed
lateral branches, as is the case of the more northern streams just
referred to, and the process of carving away the land to sea-level was
again renewed.
Portions of the original upland or mountain mass left unconsumed during
the long period of planation, which reduced most of the region nearly to
sea-level, still remain in eastern Tennessee, western North Carolina,
and northern Georgia, and form the highest and most picturesque portion
of the Appalachians.
After the upraised peneplain from which the long, even-crested ridges of
the Appalachians were produced by the excavation of the bordering
valleys had been deeply dissected and the valleys broadened, another
upward movement took place and the streams again deepened their valleys.
This is the stage in which we now find the mountains. The crests of the
ridges, characteristically displayed in eastern Pennsylvania, are
portions of the first peneplain of which a definite record is preserved,
while the broad valleys with sharply cut channels in their bottoms
represent the much less complete second stage of planation.
The two ancient peneplains referred to above, the histories of which are
recorded in the topography, have received definite names in order that
they may be readily designated. The older and higher one is termed the
Schooley peneplain[2] on account of the preservation of a typical
portion at Schooley Mountain in New Jersey, while the lower one,
represented by the broad valley through which flows the Shenandoah
River, Virginia, is known as the Shenandoah peneplain. A generalized
profile in a northwest and southeast direction through a portion of the
Appalachians is shown in the following diagram, which will serve to make
more definite the description just given. The highest summits in the
diagram represent portions of the Schooley peneplain; if the depressions
could be refilled the surface of the great plateau formed by the
elevation of this plain would be restored. The bottoms of the broad
depressions represent the Shenandoah peneplain, which is sharply
trenched by the modern river channels.
[2] Also known as the "Kittatinny peneplain," but the name used above
has priority.
[Illustration: FIG. 17.--Generalized east-and-west profile showing
relation of peneplains.]
The Appalachians thus furnish not only a typical example of a mountain
system produced by the folding and upheaval of the rocks of the earth's
crust, accompanied in many localities by breaks or faults and
overthrusts, but also preserve the records of two well-characterized
peneplains. The long and varied history of the range has been in part
interpreted by geologists from the character of the rocks, the fossils
they contain, and the structure that has been impressed upon them; but
some of the most instructive chapters are recorded in the topography,
and their study has led to a highly creditable advance in methods of
geographical research.
The Appalachian Mountains when first seen by Europeans were clothed
throughout with a varied and beautiful forest consisting largely of
hardwood trees. Nowhere do they invade the region of perpetual snow, and
glaciers are absent. These statements are true also for all of the
mountains on the eastern side of the continent to the south of Hudson
Strait.
The Appalachians abound in beautiful scenery, but, except about a few of
the very highest domes and ridges, have little of the stern
ruggedness which is typical of truly great mountains. Their countless
valleys are now mostly cleared of their primitive forests and under
cultivation. To a large extent also even the steep hillsides are tilled.
The larger trees which formerly grew on the mountains have nearly all
been felled, and where the land is not suitable for cultivation their
place is taken by a dense second growth. Under the mild, humid climate
that prevails, more especially from the vicinity of the Susquehanna
River southward, the rocks are deeply disintegrated and decayed, and
even steep mountainsides are mantled with soil and rock _débris_. It is
the excess of disintegration and decay over erosion which gives to the
mountains their usually flowing outlines and pleasingly picturesque
rather than rugged scenery. The valleys still retain much of the
material washed from the uplands, and are deeply floored with rich soil.
The characteristic colours of this decayed rock-waste are many shades of
red and yellow, which harmonize in a most artistic manner with the
prevailing green of the plant-covered uplands and abandoned fields.
These red and yellow soils, particularly about the bases of the higher
summits of the southern Appalachians, afford abundant crops of cotton,
corn (maize), and tobacco.
_The Mountains of New England, New York, New Brunswick, etc._--The
picturesque Berkshire Hills, in the western portion of Massachusetts,
have rounded and flowing outlines and a generally subdued relief. The
more prominent of these greatly eroded remnants of what was once a
mountain range rise but 2,000 to 3,500 feet above the sea. No
satisfactory boundary between these hills of gneiss, schist, and allied
metamorphic rocks, and the others of the same general character in the
neighbouring portions of New York and New Jersey, has been determined.
So far as the relief is concerned, and so far also as the complex
geological history has been deciphered, there seems no good reason for
separating the Berkshire Hills from the Appalachian Mountains. It is
convenient, however, to consider the Appalachians as terminating at the
Hudson. The Berkshire Hills when traced northward merge with a
region of similar topography which unites them with the Green Mountains
of Vermont, the highest summit of which, Mount Mansfield, attains an
elevation of 4,364 feet above the sea. To the east of the Green
Mountains are situated the still higher and more rugged White Mountains
of New Hampshire, which culminate in Mount Washington. This widely known
and greatly admired peak has an elevation of 6,293 feet, and, next to
Mount Mitchell in the southern Appalachians, is the highest mountain on
the eastern side of the continent to the south of the newly discovered
group of peaks near Hudson Strait. Associated with Mount Washington are
at least 15 peaks, each of which is over 5,000 feet high, and a still
larger number of lesser summits which exceed 4,000 feet in elevation
above the sea. The remarkable natural beauties of the Green and White
Mountains, the ease with which they can be reached by means of
railroads, and the numerous summer hotels, and hospitable farmhouses
interspersed among them, make this, the most mountainous portion of New
England, a favourite region for summer rest and recreation. The Green
and White Mountains are nearly parallel north and south ranges, from 30
to 60 miles apart, and separated by a tract of lower but hilly country
with a generally southern slope, where many streams unite to form the
southward-flowing Connecticut River.
The Adirondack Mountains, in northeastern New York, are situated some 25
miles to the west of the Green Mountains, and separated from them by
another tract of hilly country similar to the one dividing the mountains
of Vermont from those of New Hampshire. In this space lies the irregular
sheet of water over 100 miles long known as Lake Champlain. This
beautiful lake discharges northward through Richelieu River to the St.
Lawrence. In the same tract of hills, but to the southward of Lake
Champlain and tributary to it, lies the smaller but still more charming
Lake George.
The Adirondacks are rudely circular in ground plan, and measure from 60
to 70 miles from east to west, and about 100 miles from north to south.
The entire area, known to the early settlers of New York State as
the North Woods, is rugged and most pleasingly diversified. Its leading
charms are the large number of dark, densely forested summits, the many
beautiful lakes and clear, sparkling streams. The highest of the
numerous steep-sided peaks is Mount Marcy, 5,344 feet, and second in
rank is the equally beautiful eminence known as Whiteface, which rises
4,872 feet above the sea and about 3,000 feet above the adjacent
valleys. Over 20 neighbouring forest-covered summits have elevations in
excess of 4,000 feet.
The rugged region in northeastern New York and the adjacent portion of
New England is in general without well-marked boundaries. On the north
it extends into Canada, and is margined by the great valley through
which flows the St. Lawrence. In the province of Ottawa, to the south of
the St. Lawrence, there is a group of bold hills similar in many ways to
the Green Mountains, known as the Notre Dame Mountains, which decreases
in height when traced northward and merge with a roughened plateau which
extends far to the northeast and embraces the Gaspé Peninsula and the
table-land and hills of New Brunswick. Much of the country adjacent to
the St. Lawrence on the south is rolling and hilly and contains large
tracts of rich agricultural land which is highly favourable for dairying
and sheep-raising. Mount Sutton, the highest elevation in the Notre Dame
Mountains, is 4,000 feet high, and several other forest-covered
mountain-like hills range in elevation from 1,000 to 3,000 feet. In the
irregular valleys of this region there are a large number of lakes,
situated in general from 700 to 1,000 feet above the sea. The Gaspé
Peninsula to the north of New Brunswick, bordered on the north by the
valley of the St. Lawrence, and on the east by the Gulf of St. Lawrence,
has a rough relief and dense forests and is still a wilderness. The
general elevation of the uplands in this little known region is about
1,500 feet. The surface is in reality a broad plateau in which numerous
valleys have been excavated and from which rises a range of hills termed
the Shikshock Mountains, some 65 miles long and 4 or 5 miles wide,
with peaks ranging from 3,000 to 4,000 feet in height.
Much of Maine and New Brunswick is similar to the region just referred
to, and, in a generalized geographical view, may be considered as a part
of the great coastal plateau of the northeastern portion of the
continent, roughened by erosion so as to appear to one travelling
through its valleys as an endless succession of rugged hills. The
highest of the numerous prominences in Maine is Mount Katahdin, 5,200
feet, and in New Brunswick the culminating summit is Bald Mountain,
2,470 feet.
The rugged region embracing the Adirondacks, together with the more
elevated portions of New England and of the adjacent provinces of
Canada, has many geographical features that are similar to those of the
southern Appalachians, but at the same time this, the central portion,
differs in a marked way from the southern extension of the Atlantic
mountains. The higher mountains in each of these picturesque regions are
at least in a general way to be considered as the unconsumed remnants of
ancient uplands, the greater part of which have been eroded away. The
most marked contrast in the scenery of these two regions of similar
elevation is due to the presence of a great number of lakes at the
north, many of them of large size, and the total absence of such
beautifying elements in the landscapes at the south. The streams at the
north are frequently impetuous and broken by many cataracts and rapids,
thus furnishing abundant water-power; while at the south the streams
flow through more evenly graded channels and are without cascades except
near their sources in the mountains. These contrasts are such as are to
be found the world over between regions of young and old topography. The
differences in the degree of development reached by the streams of the
New England region as contrasted with those of the southern
Appalachians, finds an explanation in the fact that New England, Canada,
etc., was formerly covered with glacial ice, and on the retreat of the
glaciers the surface of the land was left with an essentially new
relief, while the southern Appalachians were well to the south of
the great ice invasion, and the streams of that region have reached a
mature development, except near the sources of their head-water
branches, which, like the topmost twigs of a tree, are always young.
The central, like the southern portion of the Atlantic mountains, is
forest-clothed. All but a few of the highest summits in the Adirondack
and White Mountains are concealed beneath a dense and varied growth of
trees and shrubs. The summits, which are nearly bare of vegetation, like
the upper 800 or 1,000 feet of Mount Washington, owe this condition to
lack of soil rather than to elevation. Nowhere in the Atlantic mountains
to the south of the but little known peaks near Hudson Strait, is the
elevation sufficient to reach above what would be the timber-line under
favourable soil conditions. The trees of the White and neighbouring
mountains are principally various species of conifers, such as the pine,
spruce, hemlock, larch, etc., which grow thickly on all but the most
precipitous slopes. Before man disfigured the beauties of the land the
lower hills, the river-valleys, and the borders of the numerous lakes
and tarns were clothed with a more varied flora than the uplands. In
these valley forests the dark foliage of evergreens is in summer mingled
with the lighter green of maples, beeches, birches, oaks, locusts, and
other broad-leaf trees. The forests are thus highly diversified and
partake of the characteristics of both the northern and southern floras.
It is in these northern woods that the glorious autumnal colouring for
which North America is justly famous is to be seen in its greatest
splendour. October is here truly the golden month of the year. At that
season the bold hills, with their sombre robes of coniferous trees, rise
like dark rugged islands above an undulating sea from which the most
gorgeous sunset colours seem to be reflected. The brilliant colouring of
the ripe foliage beautifies the land as with a cloth of gold. It is at
this season also, during the tranquil days of what is known as Indian
Summer, that a purple haze is thrown like a veil over the harlequin
landscape, as if to subdue its glories and bring them within the range
of man's appreciation.
Only a few of the higher summits in the New England region approach the
scenic conditions usually associated with truly lofty mountains. In
fact, the general lack of rugged escarpments as well as of great
elevation leads the geographer to rank even the highest of these rounded
summits as hills of large size rather than attempt to burden them with
the dignity that the term mountain carries with it. They are beautiful
hills, separated one from another by lovely valleys, which draw the
beholder to them and fill his memory with tender longings and vague
dreamy fancies such as the sterner grandeurs of great mountains fail to
awaken.
_The Laurentian Highlands._--A vast area in the eastern portion of
Canada, to the north of the valley of the St. Lawrence, including
Labrador, is underlaid by very ancient crystalline rocks of the same
general character as those forming the Adirondacks. This same geological
system, the Archean, has a wide development in the continental basin to
the north of Lake Superior and about Hudson Bay. To the north of Quebec,
in the region drained by the Saguenay and Ottawa Rivers, the land has a
general elevation of 1,500 to 1,600 feet, and is known as the Laurentian
Highlands, although sometimes dignified by the name Laurentian
Mountains, or, more briefly, as the Laurentides. In reality, this broad,
indefinitely defined region from a geographical point of view is a
roughened plateau and not a mountain range or group of ranges. When the
structure and metamorphosed condition of the rocks are considered,
however, it is found that they have the characteristics pertaining to
the central and more deeply seated portions of true mountains. The rocks
are mainly crystalline schist, gneiss, granite, etc., together with
igneous intrusions, all of which have been intensely folded, crumpled,
and broken. The general interpretation of the existing conditions is
that deep erosion has occurred and, in fact, a mountain range or a
mountain chain worn down to a generally plane surface. The thickness of
the rocks thus removed, or the depth of erosion, is unknown, and owing
mainly to the complexity of the geological structure of the terranes
remaining, will perhaps never be ascertained, but can be safely
estimated as not only hundreds, but several thousands of feet. Erosion
has laid bare portions of the earth's crust which were once deeply
buried, and reveals the character of the "basement complex," as it has
been termed, which forms the foundation of the continent. Owing to the
great age of the rocks and the depth to which they were once depressed
in the earth's crust, they have experienced great changes. They are not
only intensely folded and crushed, but in large part have been caused to
flow under great pressure, and have thus acquired a schistose structure.
Fissures have been filled with molten rock injected from below so as to
form dikes, and possibly still greater or regional intrusions have
occurred. Over large areas the amount of once molten and intruded rock
exceeds the surface exposure of what are usually, but with some
hesitation, classed as metamorphosed sediments.
Long exposure to the air in a region of mild relief is usually
accompanied by the formation of a deep soil. The soil over the
Laurentian Highlands, however, is generally thin, and large areas of
bare rock are exposed. The explanation of this apparent anomaly is that
glaciers during a geologically recent period were formed on this region
and flowed away from it, carrying most of the previously formed rock
_débris_ with them. The time since the melting of the glaciers has been
too short for a new soil to form, except in the valleys and depressions
among the bare glaciated hills, which hold a peaty accumulation
resulting from the partial decay of vegetation. The scarcity of soil is
also due in part to the climatic conditions now prevailing, which are
unfavourable to rapid rock decay.
To the north of the Laurentian Highlands and in the vicinity of Hudson
Strait, the land becomes higher, and as recently reported by Robert
Bell, of the Canadian Geological Survey, forms true mountains with
elevations in the neighbourhood of 8,000 feet. What revelations are to
come from the inhospitable and in large part ice-covered lands still
farther north can only be told as exploration and surveys are extended
in that direction.
This brief review of some of the leading characteristics of the
mountains and hills adjacent to the Atlantic coast will, I think, serve
to show that they bear a family relationship; like the members of a
family, they are of various ages, although all of them are past their
prime, and may with propriety be termed the _Atlantic Cordillera_.
THE CONTINENTAL BASIN
An inspection of the map forming Fig. 14, on which the larger
geographical features of North America are indicated, will assist the
reader in appreciating the general relations and extent of the plains
and plateaus which collectively form the Continental basin.
This medial region of the continent is bordered on the east for some
2,000 miles by the Atlantic mountains, and on the west throughout its
entire extent by the Pacific mountains. It is open to the sea at both
the north and the south, and extends in one continuous series of plains
and plateaus from the Gulf of Mexico to the Arctic Ocean. The southern
portion of this interior basin or trough has already been briefly
described in discussing the characteristics of the Gulf plains. The
northern portion has also been considered in describing the tundra
region adjacent to the Arctic Ocean.
The leading geographical features of the North American continental
basin are its generally low elevation, the mildness of its topographic
details, and, with two exceptions, the absence within its borders of
elevations having a mountainous structure. In general the rocks beneath
the surface are horizontally stratified marine sediments. The stream-cut
valleys are shallow and usually broad, except in the bordering plateaus
and foot-hills on the east and west sides, where the streams frequently
flow several hundred feet below the surface of the broad, flat-topped
interstream spaces. The drainage of the continental basin serves as a
convenient basis for subdividing it into three separate portions. These
are the Gulf slope, which discharges its surplus waters into the Gulf of
Mexico and is drained principally by the Mississippi; the St.
Lawrence slope, occupied in part by the Great Lakes and drained by the
St. Lawrence River; and the arctic slope, down which the Mackenzie,
Nelson, and other rivers flow to the Arctic Ocean or to Hudson Bay. At
no place are the Pacific mountains broken by cross-drainage, so as to
allow the continental basin to send a tribute to the Pacific Ocean.
The vast extent of the Continental basin, embracing, as it does, some
three-fourths of the entire area of North America, makes it necessary,
even in a general review of the large geographical features of the
continent, to recognise smaller subdivisions than the three great
drainage slopes referred to above. For this purpose we select the more
or less well-defined plains and plateaus into which the region is
naturally subdivided. The portion of the Continental basin embraced
within the boundaries of the United States has been shown by J. W.
Powell to consist of the following physiographic regions, namely, the
Gulf plains; the Prairie plains; the Lake plains, including the region
draining to the Great Lakes; and the Great plateaus or Great plains, as
they are more generally termed, adjacent to the eastern border of the
Pacific mountains. Several of these divisions need to be extended and
still others recognised in order to include the entire region under
review. The portion of the Continental basin to the north of the United
States-Canadian boundary has been only partially explored, and the
subdivisions of it suggested below are to be considered as provisional.
The Lake plains include in Canada the country to the north of the Great
Lakes, which drains to them, but excepting the flat lands bordering
Lakes Erie and Ontario and once covered by their waters, the region
referred to is rather a roughened plateau than a plain. From a
geological point of view the hilly country composed of crystalline rocks
to the north of Lakes Superior and Huron and included within their
hydrographic basins partakes more of the character of the Laurentian
Highlands than it does of the features of the portion of the Lake plains
situated in the United States.
The Prairie plains also extend far to the north of the international
boundary, and on their northern border merge with the forest-covered
plains in central Manitoba and the northern portion of Saskatchewan,
which are drained by northward-flowing rivers. These plains in the far
north differ from the Prairie plains in the fact that they are forested
and acquire greater diversity from the presence of innumerable lakes,
several of which are of large size. For convenience we may designate
this vast and but little known northern region as the Subarctic Forest
plains. Still farther north, where the forest dies away, lie the Barren
Grounds, which merge on their northern border with the frozen morasses
or tundra of the arctic coastal plain.
To acquire just conceptions of the topographic and other characteristics
of the several regions of mild relief which make up the Continental
basin is a difficult task, as each one is of great extent and possesses
many peculiarities of its own, and besides, in two separate regions,
each embracing many hundreds of square miles, movements in the earth's
crust have occurred of such a nature as to elevate the rocks and give
them the general structure commonly found in mountain ranges. Reference
is here made to the Ozark uplift in the southwestern portion of the
Prairie plains and the Black Hills of Dakota which rise from the Great
plateaus.
_The Ozark Uplift._--There is an area embracing about 75,000 square
miles in southern Missouri, northern Arkansas, and the eastern border of
the Indian Territory, in which the rocks have been upraised above the
surrounding Gulf and Prairie plains. The uplift, if we imagine it
uneroded, would have the general form of an inverted canoe; that is, it
would form an elongated ridge, broad and dome-like in the central
portion and dying away on all sides into the great surrounding region of
undisturbed and essentially horizontal rocks. The major axis of the
uplift, although exhibiting a double curvature, has a general northeast
and southwest trend. It is about 500 miles long, and in the widest part
is approximately 200 miles broad. What the height of the dome
would be had the rocks composing it not yielded to the destructive
influences of the air or been removed by streams cannot be readily
estimated, since the movements of the earth's crust which upraised it
occurred at several widely separated intervals with intervening periods
of decay and erosion, and downward movements have also been experienced
which submerged the region and permitted the deposit of sheets of
sediment over it. If the results of the upbuilding agencies had not in a
large measure been counteracted in these several ways, the dome to-day
would have a height of several thousand feet. In the present condition
the deeply eroded dome presents the net result of elevation over
subsidence and erosion. The dome-like form is lost, and in its place is
a complex series of ridges and valleys. The higher summits now
remaining, situated principally in the Iron Mountain district in
northeastern Missouri, rise from 1,400 to 1,800 feet above the
neighbouring plains, and from 1,800 to 2,100 feet above the sea.
The greater intensity with which the rocks in the southwestern portion
of the Ozark uplift have been folded than in the more northern portion
and the varying degrees to which the beds have yielded to denudation
have resulted in giving to its various parts different types of
topography. This diversity has led to the recognition of several
distinct divisions, such as the Shawnee Hills, at the extreme
northeastern end of the uplift, where the rocks have been folded and the
ridges cut across by the Mississippi; the St. François Mountains, in
southeastern Missouri, composed of a large number of isolated hills and
rising from 500 to 800 feet above the adjacent valleys; the Ozark
plateau, in southwestern Missouri and northwestern Arkansas, the central
part of which has a general elevation of 1,500 feet above the sea, and
to one travelling over it seems a boundless and featureless plain
underlaid by apparently horizontal but in reality gently westward
dipping sheets of stratified rocks; the Boston Mountains, in central and
western Arkansas, consisting of rugged irregular ridges and truncated
summits with a general crest-line elevation of 1,000 feet above
the sea; and the Ouachita (pronounced _Wichitaw_) Mountains, formed of
numerous rudely parallel upward folds of hard rock, which rise from 500
to 1,000 feet above the adjacent valleys and form a belt of unusually
picturesque, forest-crowned hills, extending from Little Rock, Arkansas,
westward into Indian Territory.
The study of the island-like Ozark region in the broad, ocean-like
expanse of the prairies is far from being complete. Although
topographically distinct and appearing as one of the minor units in the
geology of the continent, geologists are inclined to the view that the
Ozark uplift as above described should be considered as consisting of
two independent but contiguous areas of upheaval, namely, the Ozark
Hills, situated mainly in Missouri, and the Ouachita Hills, lying mainly
in Arkansas and the Indian Territory. This Ozark-Ouachita region--by
whatever name finally designated--is one with a long and varied, nay,
even a poetic history. In writing of the Archean rocks of the Iron
Mountain region, Missouri, Arthur Winslow states that they "are truly
ancient elevations, older than any others in the State, older than the
mountains of Arkansas, older than the Appalachians, older than the Rocky
Mountains; if venerable be an attribute of great age, they certainly
merit that appellation. For not only are all other rocks of Missouri
youthful as compared with these, but there is a genetic relationship,
and the former are in a sense descendants of the latter. For when the
limestones and other sedimentary rocks were yet unformed these
crystalline rocks must have existed as parts of a continental mass, and
from the degradation of this continent resulted the materials of the
later formed sedimentary rocks. The present granite and porphyry hills
are but protruding parts of the remnant of this ancient continent which
stood as islands above the ocean waters while the beds of limestone and
sandstone were being formed about them, which rose with these beds when
they were lifted from the waters, which now, rugged and weather-beaten,
yet tempered by age and varied experience, rear themselves above the
surrounding younger rocks and bid fair still to live when the
latter have yielded to the forces of degradation."
Besides its pleasing scenery, varied and abundant mineral resources, and
health-giving springs, this oasis of hills amid the unvaried monotony of
the grass-covered plains in the southern portion of the continental
basin derives an additional attraction from its forest growths in which
southern pines are mingled with oaks, hickories, walnuts, and other
broad-leaved trees. The soil is generally productive, and great fields
of corn and cotton may be seen side by side.
_The Gulf Plains._--The Gulf plains include the western portion of
Florida, and extend westward and southward about the borders of the Gulf
of Mexico in a continuous belt from 50 to 60 to perhaps 100 miles wide,
to where the Pacific mountains approach the coast in east-central
Mexico. This low, gently seaward-sloping region, underlaid by soft
horizontal strata, possesses a generally rich soil well adapted for the
cultivation of cotton, corn, sugar-cane, and rice. In the low, hot
country of eastern Mexico nearly all tropical fruits can be successfully
raised. The most characteristic as well as the broadest portion of this
productive belt is in the States of Mississippi and Louisiana, and
extends northward with a gradually decreasing width to the mouth of the
Ohio. This is the lower Mississippi basin, which owes its existence
mainly to the deposits of silt laid down by the river after which it is
named. Much of the land is really the delta of the "Father of Waters,"
over which that river spreads out in vast inundations each year.
The Gulf plains skirt the southern end of the Appalachian Mountains, and
to the west of the Mississippi are bordered in part by the Ozark uplift.
There are certain reasons for believing that these two regions of
elevation, characterized by a similar geological structure, are portions
of a single greatly disturbed belt, but are now separated by a broad
area which has been depressed and deeply covered with comparatively
recent sediments. But that this general view of the origin of the larger
features in the relief of the Gulf States can be accepted with
entire confidence is questionable. True it is, however, that the delta
region of the Mississippi has undergone many up and down movements, and
that several successive sheets of sediment have been laid down upon it,
but that the folds and crumplings characteristic of the southern
Appalachians and of the Ozark uplift extend across the intervening space
beneath the covering of horizontal rocks has not been demonstrated.
The Gulf plains throughout are less than 500 feet above the sea, and
much of the Gulf margin and the similar tract which extends northward to
the mouth of the Ohio has an elevation of less than 100 feet. The fringe
of lowland bordering the Gulf and extending up the course of the
Mississippi is generally swampy and contains numerous small water bodies
which owe their existence to the cutting off of the beds of the river so
as to form what are termed ox-bow lakes.
Previous to the settlement of the Gulf plains by Europeans and the
clearing of much of the land for plantations it was clothed with such a
dense growth of trees and vines as to be almost impenetrable. The
southern pine there reaches its greatest perfection and is the basis of
a great lumber industry, and oaks of several species, the wide-spreading
white-trunked sycamore, the still more stately tulip-tree with its
cup-like blossoms of yellow, the fragrant magnolia, the seemingly always
aged cypress, the gum-tree, and many other species of arboreal
vegetation also find most congenial conditions for their growth. The
dwarf palmetto, which forms such a characteristic growth in Florida,
extends northward in the Mississippi basin to the southern border of the
Ozark uplift. Much of the luxuriant moss and lichen draped forest of the
Gulf plains with all its primitive network of shrubs and vines still
remains.
_The Prairie Plains._--A prairie in the current use of the term is a
generally level region, either a plain or a plateau, without forests but
clothed with a carpet of luxuriant grasses and flowering annuals. A
rolling prairie is an undulating or hilly, grass-covered region. The
Great plains of the west-central portion of the Continental basin
meet these requirements, and are typical prairies. On their eastern and
northern border the Prairie plains merge with the adjacent forested
plains, and on the west from Mexico northward to the subarctic forest
pass by still less tangible gradations into the more elevated and drier
Great plateaus or high plains, where bunch-grass, with bare intervals
between the scattered tufts, takes the place of the continuous sod of
the true prairies. The reasons for the change from forest to prairie and
beyond to the land of the bunch-grass as one travels from east to west
across the interior basin, lie in differences in the humidity of the
climate.
The Prairie plains have their beginning at the south in Mexico a short
distance from the Rio Grande, and are prolonged northward through
central Texas, meeting to the north of Red River the forest-covered
Ouachita Hills. But to the west of the Ozark uplift the Prairie plains
extend northward in a belt about 100 miles wide which expands in Kansas,
northern Missouri, eastern Nebraska, Iowa, Illinois, and western Ohio to
fully 800 miles. In this highly fertile region, now the most productive
agricultural area of comparable size in North America, if not in the
world, one may travel in a straight line for nearly 1,000 miles through
a land without high hills but pleasingly diversified by undulations of
the generally level surface and by winding stream-formed valleys
bordered by swelling bluffs, without losing sight of towns, villages, or
comfortable farmhouses. In spring this entire region is bright green
with pastures and sprouting grain-fields, and in autumn yellow with the
harvest. Miles on miles of rustling corn-fields form the most
characteristic feature of the summer landscapes.
The Prairie plains contract to the north of Illinois and Iowa to a width
of about 200 miles, being encroached upon by the forests of the Great
Lakes region, but are prolonged northward through Minnesota and the
Dakotas far into Canada. The length of these natural meadows from south
to north is nearly 2,000 miles; their entire area is not far from
500,000 square miles. On the north they merge with the vast region
of similar relief which is darkened by the pines and spruces of the
subarctic forest.
The northern portion of the original prairie region has been given a new
and in some respects a more pleasing aspect by the sowing of millions of
acres with wheat. This is the most favourable large area for wheat
culture in North America, and one of the three great wheat-growing
regions in the world. The most productive portion of these northern
wheat-lands lies in the valley of the Red River of the North, situated
in part in Minnesota and the eastern portion of the Dakotas, but
including also the plains of Manitoba. Could we view the broad extent of
the Prairie plains as do the birds in their southward migrations, we
would see them golden with the sheen of ripening wheat at the north,
green and russet in the central portion with corn, and white with cotton
to the south. Everywhere from south to north and east to west the vast
expanse is dotted with the curling wreaths arising from household fires,
and at hundreds of localities blotted by the smoke of towns, factories,
smelting-works, and coal-mines.
Throughout the entire extent of the Prairie plains the underlying rocks
are essentially horizontal, and consist largely of limestone. An ancient
sea-bottom has been broadly upraised with but slight disturbances of the
strata to a general elevation of about 800 feet in Minnesota and the
Dakotas. From this low continental divide the land slopes gently both to
the north and south. The local variations of surface are due mainly to
the unequal weathering of the rocks and the excavation of stream-formed
valleys. To the north of the mouth of the Ohio, however, the prairie, in
common with the adjacent regions, was formerly occupied by glacial ice,
which on melting left widely spread deposits of clay, stones, gravel,
etc., which gave the region a new surface, and in certain instances
turned the streams from their former courses. Much of the rolling
prairie inherits its billowy surface from the glaciers. In the midst of
the young topography of glacial and more recent date there is an area of
about 10,000 square miles in southwestern Wisconsin and adjacent
portions of Minnesota and Iowa which is surrounded by the deposits of
the ancient ice-sheets (glacial drifts), but not covered by them. This
driftless area, as it is termed, has an old topography in striking
contrast to the relief of the region about it, in which broad
river-valleys bordered by the pinnacled and castellated rocks exposed in
the bordering slopes of the adjacent uplands are among the most
conspicuous features.
The soil of this driftless region is a ferruginous clay, resulting from
the prolonged weathering of the rocks, principally limestone, on which
it rests, while the surfaces formerly covered by glacial ice are mantled
with soil of a mixed character containing many fragments and large
boulders of compact rock. In the prairies to the south of the glacial
boundary the soils are mainly of a sedentary origin, and have resulted
from the disintegration and decay of the rocks on which they rest, but
usually rendered black by the humus resulting from the partial decay of
numberless generating grasses and other lowly plants. This black soil is
wonderfully productive and furnishes the basis of the greater part of
the wealth and industries of the region it covers. The minor exceptions
to the general fertility occur where the rocks immediately underlying
the surface, as in the zinc and lead region of southwestern Missouri,
are highly charged with flint-like material, which remains when the
limestone once containing it is dissolved and carried away. The
horizontal sheets of rock beneath the broad central portion of the
Prairie plains belong to the Carboniferous system and contain highly
valuable seams of bituminous coal. The area of these coal-producing
lands is estimated at 125,000 square miles. In this same region also
there are extensive tracts in which natural gas and petroleum are
obtained in remarkable abundance. In southern Wisconsin and the adjacent
portions of Illinois valuable deposits of lead occur under conditions
similar to those associated with the lead and zinc mines about the
northern border of the Ozark uplift.
Owing to the demand for transportation facilities and the mild
relief of the land, the entire extent of the Prairie plains is covered
with a double-lined network of steel. The ganglia in this pulsating
nerve system of intercommunication are Chicago (here included, as it
belongs to the prairie as well as to the Great Lakes region), St. Louis,
Kansas City, Omaha, Minneapolis, St. Paul, etc., cities with from
100,000 to over 1,500,000 inhabitants, and hundreds of lesser centres of
trade, manufacture, and education.
_The Lake Plains._--The region draining to the Great Lakes--or the
Laurentian lakes, as they may, perhaps, be more properly designated,
since they form the source of the river of that name--presents many
striking contrasts to the more monotonous treeless prairies skirting it
on the south and west.
The name "Lake plains," suggested by J. W. Powell for the portion of the
region here referred to within the borders of the United States, when
extended to the entire area draining to the Laurentian lakes, is in part
a misnomer, since much of its surface is rough and irregular. In a
certain sense, however, the term _plain_ is applicable, since it
includes a plain of water over 95,000 square miles in area. The combined
areas of the lakes are greater than that of the region draining to them.
The land bordering the Laurentian lakes is underlaid to a large extent
by horizontal or but slightly disturbed sedimentary rocks, but includes
on the north a portion of the contorted, crystalline terranes already
referred to as forming the Laurentian Highlands, and in general is
characterized by the mildness of its relief. The elevations of the
surfaces of the several Laurentian lakes above the sea are, in feet, as
follows: Superior, 602; Michigan and Huron, 582; Erie, 373; and Ontario,
247. The land forming the margins of these water bodies rises in general
less than 300 feet above their surfaces. In portions of northern
Michigan and in the region of crystalline rocks to the north of Lakes
Superior and Huron, however, the relief is more pronounced and there are
many bold rounded hills with basins between them.
The principal part of the nearly plane land surface about the Laurentian
lakes is in immediate proximity to their borders, and records the
former extent of their waters. These plains, composed of clay deposited
from the lakes when more widely expanded than at present, form a fringe
from 5 to 50 or more miles broad all about the present lake margins.
Across this gently sloping surface the streams from the uplands,
increasing in length as the lakes were lowered, have excavated narrow,
steep-sided channels. These modern plains furnish typical illustrations
of young topography.
In its primitive condition nearly the entire Laurentian lakes region was
densely covered with trees. Previous to the destruction which followed
the advance of the lumbermen its northern portion contained some of the
finest and most valuable white-pine forests on the continent. To the
south of the Laurentian Lakes, and in a general way adjacent to the
Prairie plains, there were park-like areas in the forest, known as
oak-openings, where picturesque bur-oak grew in open groves amid
luxuriant natural meadows. These sunlit gardens, yellow and purple with
golden-rods and asters in autumn, owed their existence to soil
conditions determined long previously by the streams issuing from the
margin of the retreating ice-sheet, which formed level areas of sand and
gravel. The loose open texture of these deposits renders them less
retentive of moisture than the neighbouring morainal hills, and during
the long hot summers all but the most deeply rooted of the trees that
spring up upon them perished.
The soil throughout the Great Lake region is nearly all of glacial
origin and presents many local variations, dependent principally on the
fact that the streams flowing from the ice assorted the _débris_
delivered to them. The surface material, technically speaking, is of
both glacial and fluvio-glacial origin. The former consists principally
of stony clay or _till_, and the latter of gravel. About the immediate
border of the existing lakes lacustral clays form the surface. The
leading characteristics of the glacial and fluvio-glacial soils are
their varied composition and endurance under cultivation. The glaciers
that ploughed the land preparatory to the present harvest gathered
together a great variety of rock _débris_, much of it broken and
unweathered and not leached of its more soluble constituents.
The most typical portion of the Lake plains, including the southern part
of the province of Ontario and the southern shores of the Laurentian
lakes from Minnesota to New York, is highly favourable for agricultural
pursuits, and produces in abundance a great variety of crops as well as
richly flavoured fruits, luscious berries, and healthful vegetables. The
beneficial influence of the neighbouring water bodies on the climate,
tempering the heat of the summers and moderating the severity of the
winters, is shown especially in the distribution of the fruit belts of
Michigan, Ohio, and New York, which are in regions where the prevailing
winds blowing over them come from the lakes.
_The Subarctic Forest Plains._--The Prairie plains merge at the north
with a great tract of forest-covered lowlands, which extend from the
Laurentian hills on the east to near the base of the Rocky Mountains on
the west. The change as one travels northward from the grassy prairies
to the country of equally mild relief, but clothed with trees adapted to
a rigorous climate, is gradual. Along the irregular and in part
indefinite junction of these two vast plains, the alignment of the
forest is broken in many places, and its margin fringed by a picket-line
of groves and of isolated trees, which has advanced southward and
invaded the grass-lands. Between these outposts the prairie with its
wealth of summer bloom reaches well into the realm of perennial shadow.
The southward extensions of the forest are mainly in the valleys and
adjacent to the streams, while the drier steppes between are open
grass-lands. No conspicuous change in the topography of the land or of
the rocks or the soil coincides with the change from grass to forest.
The differences in vegetation must therefore be sought in climatic
conditions, and mainly in the influence of atmospheric changes on the
water contained in the soil.
Throughout practically the whole of the region occupied by the subarctic
forest, between Hudson Bay and the foot-hills of the Rocky Mountains,
the land is low and the valleys monotonous. Many lakes are
present, several of them of large size, and the rivers are remarkable
for their lengths, low gradients, and large volumes.
The subdued topography of the region here considered, and the presence
of vast numbers of lakes and swamps, is due in general to the influence
of the ice-sheets which formerly covered it. In a minor way the presence
of the innumerable small lakes and swamps is owing to the obstructions
formed by growing vegetation, the damming of streams by driftwood, the
work of beavers, and possibly the influence of subsoil ice.
To the north of the Subarctic Forest plain, as already described, occur
the desolate tracts known in Canada as the Barren Grounds, which form a
part or merge into the tundras bordering the Arctic Ocean.
_The Great Plateaus._--The boundary between the prairie plains of the
central portion of the interior Continental basin and the Great plateaus
(Great plains) bordering them on the west is usually indefinite. The
prairies pass into the more elevated and drier plateaus by insensible
gradations. The plateaus rise gradually from east to west, and along
their western margin, adjacent to the east base of the Pacific
mountains, attain a general elevation of from 5,000 to 6,000 feet. Over
vast areas these monotonous plateaus, with their even sky-lines, are
higher above the sea than the crests of the Appalachians, and along
their western margin in many localities even surpass in elevation the
most prominent peaks in the eastern portion of the United States.
Accompanying this increase in elevation from east to west there is a
decrease in precipitation, and in consequence a marked change in the
vegetation. The plateaus, like the prairies, are treeless in their most
characteristic portions, but the larger rivers winding across them are
margined in many instances by giant cottonwoods.
The mental picture that a traveller over the broad plateaus retains in
after-years is of a vast treeless level tract of country, boundless as
the ocean, which is bright green and decked with lowly flowers in the
early spring, but becomes yellowish brown as the heat and dryness
of summer increase and the grasses lose their freshness. Various
portions of the plateaus, however, have their own individuality and
present characteristics which make them conspicuously different from
other portions of the same great series of steppes. At the south, in the
region of the Rio Grande and of the Pecos and Canadian Rivers, the
plateau is dissected by stream-cut valleys 1,000 feet or more deep, and
from one to two score miles across, which divide it into a number of
individual table-lands. The plateau margins for many miles on each side
of the larger river-valleys have been carved by a complex system of
secondary and usually ephemeral streams into a great variety of rock
forms with deep trenches between. These conspicuously sculptured areas
constitute what are commonly termed Bad Lands. In certain regions also
the surfaces of the plateaus, more especially in Nebraska and South
Dakota, are broadly undulating or reveal a seemingly endless succession
of ridges and hills separated by shallow depressions, due to the
presence of large tracts of drifting sand. In spite of these several
variations, however, the leading characteristics of by far the larger
portion of the plateau country are the generally level grass-covered
surfaces extending away in all directions far beyond the reach of
vision. On the rolling prairie one can frequently see the undulating
surface about him for a distance of 15 or 20 miles, but the curvature of
the earth usually draws still narrower limits to the region within the
view of the plainsman. In riding over the plains the scene changes but
little from day to day and from week to week. Monotony is the one word
that best describes the lives of those whose lot is cast on these broad
featureless surfaces. In journeying westward across the plateau over any
one of the transcontinental railways a moment of excitement occurs when
the even line of the western horizon is broken by the summit of a
cloud-like mountain-peak. "Land ho!" is no more thrilling to voyagers on
the ocean than the shouts which first made known the presence of a
mountain-peak to the bands of immigrants who slowly voyaged across this
sea of grass with their picturesque "prairie schooners" previous
to the building of the railroads which now bind together the East and
the West.
The Great plateaus begin indefinitely to the south of the Rio Grande,
broaden in the United States to a general width of about 400 miles, and
extend far northward into Canada. Their northern limit has not as yet
been determined, but is to be looked for near the head waters of the
Mackenzie. The length of the plateau country is in the neighbourhood of
2,000 or 2,500 miles, and its average width about 300 miles. An estimate
of the area with a generally plane surface and an elevation of from
1,000 to 6,000 feet above the sea places it at about 700,000 square
miles.
The eastern portion of the Great plateaus includes western Texas,
Oklahoma, the central and western portions of Kansas and Nebraska, the
western half of South Dakota, western North Dakota, western Assiniboia,
and thence extend northward so as to include portions of Saskatchewan,
Alberta, and Athabasca. On the west the plateau region includes the
eastern portions of New Mexico and Colorado, extends far into Wyoming,
and embraces central and eastern Montana, and thence reaches northward
to Mackenzie.
This region of essentially level plateaus, extending as it does from the
hot lands of eastern Mexico nearly to the arctic circle, presents great
diversity of climate and also well-marked variations in the secondary
features of its relief. Of necessity it needs to be subdivided for more
detailed study. The rivers flowing eastward from the Rocky Mountains
have excavated valleys in the plateau region, and may be used as a basis
for its subdivision. This has been done by J. W. Powell for the portion
within the borders of the United States, and the terms Pecos plateau,
Arkansas plateau, Platte plateau, and Missouri plateau have been
proposed; this category may be extended especially to the northward, so
as to include the less well-known Saskatchewan, Athabasca, Peace, and
Laird plateaus. Each of these divisions is in reality a group of
plateaus, for the reason that the broad areas between the
eastward-flowing rivers are trenched by lateral stream channels
tributary to the main waterways, and thus subdivided into smaller units.
This subdivision of the plateau region by stream channels leaving
flat-topped areas between them makes one instructive geographical
process prominent--that is, the great table-land has been dissected. The
depths of the channels cut across it depend mainly on the elevation of
the land and the distance the streams have to travel to reach the sea;
but modifying conditions are furnished by the degree of resistance the
rocks offer to erosion, the amount of precipitation, etc. If the
elevation is great, the stream can cut deeply, and leave bold secondary
plateaus between them; if the distance to the sea is short, other
conditions being the same, the streams can cut more deeply than when
their courses are long; if the rocks are resistant, they are left in
bold escarpment bordering the valleys and the margins of the secondary
plateaus are well defined, but if they are soft and crumble easily,
their _débris_ is washed and blown into the rivers, and a general
lowering of the surface without the formation of deep trenches is the
result. These and still other conditions have influenced the manner in
which the Great plateaus have been dissected, and are of necessity to be
considered in a critical discussion of the history of the land as
recorded in its relief.
The main reason for the dissection of the region under consideration is
to be found in the fact that it is bordered on the west by high
mountains where precipitation is abundant, and the streams, supplied
largely by the melting of the snow in summer, flow across a
comparatively rainless country. The stream channels in general have been
deepened at a more rapid rate than the areas between them have been
lowered by erosion. Valleys running east and west have thus been
excavated, leaving the intervening spaces as uplands, which, however, in
certain instances have been minutely dissected by the streams
originating on them and supplied by local winter precipitation. Added to
these general conditions are differences in rock texture, which have led
to great variations in the details due to erosions, particularly on the
valley borders.
One other condition which has modified the history of the plateau
region throughout, but most decidedly at the north, is the climatic
change which culminated in the Glacial epoch. During the time referred
to the northern portion of the Great plateaus situated in Canada and the
adjacent part of the United States was invaded by glacial ice which
spread an irregular sheet of detritus over the country it occupied.
Decided changes occurred also in the central and southern portion owing
to increased precipitation, the flooding of the rivers leading from the
melting ice-front, and to movements in the earth's crust of as yet
undetermined extent and amplitude. It is apparent to the geographer that
much of the history of the climatic changes of glacial and post-glacial
times is recorded in the relief of the interior Continental basin to the
south of the limit reached by the ice and in the terraces and alluvial
deposits of the valleys, but as yet for the most part this interesting
story remains unread.
The most deeply dissected portion of the Great plateaus occurs in
western Texas, eastern New Mexico, and Oklahoma. In that region the
rivers having their sources in the Rocky Mountains and flowing to the
Gulf of Mexico have excavated deep and wide valleys, leaving broad
intervening areas in bold relief.
The Pecos River drains a large part of the mountainous region in eastern
New Mexico, and flows through a valley of its own making, which is some
30 or more miles broad and its bottom about 1,200 feet below the general
surface of the plateau lying to the eastward. The Canadian River has
excavated a similar valley, which is some 40 miles broad throughout much
of its course, and is bordered by bold rocky escarpments from 1,000 to
1,200 feet high, in which the edges of the horizontal strata underlying
the adjacent plateaus are exposed. This region of large and strongly
defined topographic features illustrates in a remarkable manner the
nature of the work performed by streams which rise amid high mountains
and flow across a dry plateau standing well above sea-level.
_El Llano Estacado._--A typical portion of the great plateau region left
by deep dissection is furnished by the table-land named by early
Mexican explorers "El Llano Estacado," or the Staked Plains, in
reference to the fact that owing to the monotony of the surface and the
scarcity of water the routes of travel were at first marked by stakes.
This region, celebrated in the traditions of the Southwest frontier, is
described by Captain Marcy, who crossed its eastern portion in 1849, as
being "much elevated above the surrounding country, very smooth and
level, and spreading out in every direction as far as the eye can
penetrate, without a tree, shrub, or any other herbage to intercept the
vision. The traveller in passing over it sees nothing but one dreary and
monotonous plain of barren solitude. It is an ocean of desert prairie,
where the voice of man is seldom heard, and where no living being
permanently resides. The almost total absence of water causes all
animals to shun it; even the Indians do not venture to cross it, except
at two or three points, where they find a few small pools of water." As
will be shown below, the barrenness and desolation of this arid tract is
not so great as it seemed to those who first invaded its primeval
solitude.
El Llano Estacado, or the _Llano_, as it is frequently termed, is about
500 miles across from north to south, and 280 miles wide from east to
west. It is bordered on nearly all portions of its periphery by
descending escarpments which lead down to the adjacent valleys. Its
surface, although appearing horizontal, in reality slopes eastward at
the rate of about 20 feet per mile, and on its highest, northwest
border, has an elevation of 5,500 feet above the sea. This great
table-land has a smooth floor, and, as reported by recent explorers, is
clothed with an abundance of bunch-grass, which formerly furnished
sustenance to herds of antelope and deer. It was in this general region
also that some of the immense herds of buffalo which once inhabited the
broad plateaus found a winter range.
The Llano, together with its southward extension, having the same
characteristics and known as the Edwards plateau, is bordered on the
west by the deep and broad valley of the southward-flowing Pecos River,
and on the north by the equally deep and broad valley carved in the
plateau country by the eastward-flowing Canadian River. The
eastward slope of the surfaces of the two plateaus is continued
throughout the region bordering them on the east all the way to the
shore of the Gulf of Mexico. The streams originating on the eastern
border of the eastward sloping plateaus and flowing to the Gulf of
Mexico, represented at the present time by the Colorado (of Texas), the
Brazos, Trinity, and Red Rivers, extended their trunks by head-water
corrasion and developed numerous branches so long as the rainfall was
sufficient to maintain a surface drainage. But as the streams were
lengthened they cut farther and farther westward and into a region that
became drier and drier, until finally they reached a land in which all
of the scanty rain that fell was absorbed by the thirsty soil. The
drainage from this higher and drier region is subterranean, and reaches
the head waters of the streams to the eastward to a considerable extent
as springs. The streams which lowered the country to the eastward of the
Llano developed many branches, some of which were extended westward into
the drier plateau country in such a manner as to give the eastern margin
of the remaining upland a scalloped and irregular border.
In travelling westward up the courses of the rivers of eastern Texas,
one passes from a low region of old topography to one where the head
branches of the streams flow in cañons, and the relief has the
ruggedness of youth; on gaining the western border of the belt of
country having surface streams one ascends to the smooth surface of the
high plateau, which is young as regards stream development, although in
years older than the country with a deeply eroded surface to the
eastward. The Llano and Edwards plateau present us with examples of
perpetuated topographic youthfulness.
The Llano, although dreaded by early explorers and shunned so far as
possible even by experienced plainsmen, on account of a lack of water,
has in recent years become more favourably known. It is crossed at
present by two railroads. Water has been found beneath the surface in
numerous localities, and the desert-like region now bids fair to
become a favourable cattle-raising country. It is not to be expected,
however, that all the glowing predictions which have been published
concerning this and neighbouring table-lands will be more than partially
fulfilled through the use of the subsurface waters.
_The Arkansas Plateau._--To the north of the Canadian River the region
termed above the Great plateaus is less deeply dissected than in the
portion of which the Llano is typical, and the streams from the
mountains flow through shallow valleys with less rugged and less
picturesque borders than those of the deep wide valleys of western Texas
and eastern New Mexico. The broad plateau surfaces adjacent to the
valleys of the Arkansas and Platte Rivers probably come nearer to the
popular idea of the essential characteristics of the "Great plains" than
any other of the larger divisions of the region under review. The most
conspicuous geographic features of the Arkansas plateau have been
described by W. D. Johnson as consisting of an assemblage of low and
broad table-lands separated by shallow erosion valleys. The plateaus are
immense unsculptured remnants in light relief of an older and originally
perfect plain. The few long and feeble streams, wide apart and flowing
eastward from the distant mountains in parallel courses and without
tributaries, have blocked out by dissection the larger features of the
broad landscape which in future ages will be slowly etched into a
multitude of details. The scenery of these featureless plains is
ordinarily depressing when once the novelty of being adrift on a sea of
grass has passed away. There is nothing that can be termed scenery
except that which once a year for a brief period the sky affords when
clouds of extraordinary grandeur darken the air. Throughout nearly the
entire annual course there is no material for landscape effect except
the straight line of the horizon with a featureless breadth of sun-faded
brown below it and above a merely broader space of faded blue. There is
nowhere a curved line, and though as a scientific fact there is vast
expanse of flat plain, there is little to suggest it when the sky is
empty of clouds. In June the clouds come with a gradual maturing at some
point along the even sky-line, and increase rapidly until the
heavens are filled with magnificent vapour banks; but the display is
simply spectacular, and passes away in a few hours as quickly as it
came, with only local showers to refresh the land.
The one industry that can thrive on the Arkansas plateau, which was
formerly at certain seasons blackened by herds of bison, is
stock-raising. Wells from which water is pumped by windmills furnish
sufficient water for herds of cattle and horses, but not for irrigation.
_Bad Lands._--In the northern portion of the Great plateaus within the
United States the surface rocks over great areas are soft or but
irregularly hardened sediments of ancient lakes and streams and have
been sculptured by rain, wind, and ephemeral rills into a most
marvellous array of monumental and castellated forms. Localities where
this minute dissection of the soft horizontal strata is especially well
marked over hundreds of square miles occur in South Dakota and Montana,
and especially on the borders of the valleys carved by the Loup Fork,
Niobrara, White, Yellowstone, and Missouri Rivers. In this region the
rainfall is light, the mean annual precipitation being in the
neighbourhood of 15 inches, and occurs mostly during the winter months.
In the summer season the lands far out on the plateaus are dry and hot,
and all but the larger streams disappear. The rocks, consisting mostly
of unconsolidated clays and soft sandstones, with occasional hard layers
and irregular concretions, have been cut into innumerable channels,
leaving steep-sided remnants of the former plain between. The maze of
trench-like valleys, the similarity of the sculptured land-forms one to
another, and the absence of water, make these desert regions excessively
difficult to traverse. The Canadian-French who explored the
north-central portion of the Great plateaus in early days of American
settlement termed these tracts of country, so difficult to cross,
_Mauvaises Terres_, a name now seldom used, but replaced by the English
name Bad Lands. Although _bad_ to the hunter and the plainsman, these
desert regions are of fascinating interest to men of scientific
training. The intense heat, the choking alkaline dust, the absence of
water, and the danger of being lost and of perishing of thirst in
these wild silent regions, have not checked the ardour of explorers. Not
only do the Bad Lands present a most attractive field to the student of
erosion and of the origin of earth forms, but their deathlike solitudes
have been made to yield the most wonderful procession of strange extinct
animals yet unearthed by geologists. They are vast cemeteries in which
are interred the skeletons of many genera and hundreds of species of
animals which lived in the ancient lakes or wandered through the almost
tropical forest that in distant ages clothed the adjacent country. The
great lesson to be learned by the geographer in these uninviting regions
as they seem to most people relates to the way in which the rocks have
been eroded. The prevailing softness of the beds with occasional hard
layers, the scarcity of vegetation, the occasional heavy rains, and the
considerable height of the country above the master streams combine to
favour rapid and deep sculpturing. The precipitous slopes of the small
mesas and castle-like rock forms destitute of all vegetation excepting
succulent cacti and scattered clumps of bunch-grass, reveal a multitude
of sunken lines and raised edges, produced by the ephemeral streams, and
a less complex series of horizontal ledges due to the prominent edges of
hard layers. The steep slopes are worn into alcoves and irregular
recesses by the transient rills, and smoothed or etched by the
wind-driven sands. The result is an assemblage of architectural forms
such as only the most fantastic dream pictures or the strange tricks of
the mirage on northern ice-fields can simulate. Nor are the wonderfully
intricate topographical forms the sole attraction. The rocks are
variously coloured, and present endless combinations of yellow, red,
green, purple, etc., in many tints and shades, rendered seemingly
brilliant by contrast with the gray of shales and the blackness of
occasional coal-seams. Owing to the burning of coal-beds, the rocks are
sometimes altered over broad areas and given unusually striking colours,
among which various shades of red predominate. Standing on some
commanding crag in the Bad Lands in the early morning or when the purple
shadows of evening fill the gorges and ravines, the most unimaginative
traveller sees in the silence about him the ruins of a vast city, with
cathedrals, temples, and palaces of varied colours and weird designs
such as no mortal hand ever fashioned. It is at such times that the
picturesque and gorgeous, although desolate, landscape kindles the fancy
and suggests day dreams which distract one's attention from the more
prosaic study of these earth ruins.
The best developed portions of the strange region here referred to occur
on the borders of the uplands overlooking the larger valleys, excavated
by the rivers flowing eastward from the mountains, and are simply larger
examples of erosion, such as may be seen in many bluffs and valley-sides
in nearly every country, but rendered conspicuous by their size, extent,
endless variety, and unusual colours.
_Sand-Hills._--The sands winnowed by the winds from the bare plains and
steep bluffs are in certain places on the Great plateaus gathered into
dunes which cover great areas with a succession of low dome-shaped
hills. On the borders of the Niobrara River there is a detached area of
about 20,000 square miles, which has been covered in this manner with
loose sands. This region, as described by F. V. Hayden, presents a
succession of round-topped hills, some of them scooped out by the
swirling winds so as to resemble volcanic craters. These sand-hills were
formerly a favourite resort of the bison, which fed upon the scanty but
very nutritious grasses in the little valleys and intervals among the
mounds and ridges. There is, for the most part, an abundant supply of
water in the lakelets scattered through the region, and fed by the
seepage from the porous sands, which drink in all the water that falls
upon them and allow it to percolate slowly into the adjacent
depressions. Some of the lakelets and ponds are highly alkaline, while
others are fresh; the former can be easily distinguished from the latter
by the absence of vegetation about their borders. The hills, although
seemingly utterly desolate, on a nearer view sometimes reveal
considerable vegetation, including yuccas or "Spanish needles," which
shelter the sands from the winds.
Many other regions on the western border of the Great plateaus, in the
valleys of the Rocky Mountains and on the desert plains of Utah, Nevada,
and California, are buried beneath drifting sands, which have the
characteristic features of a dune-covered seacoast. The sources of the
sands in these interior plains are usually to be found in the
disintegration of the rocks under the action of the dry air with its
many and sudden changes of temperature, but occasionally they come from
desiccated lake beds not yet clothed with vegetation.
_Central Portion of the Great Plateaus._--The State of Nebraska, about
400 miles in length from east to west, and extending across the Great
plateaus to within some 60 miles of the mountains bordering them on the
west, furnishes a typical example of the west-central portion of the
interior Continental basin. As described by Hayden, this State may be
divided into two portions, one agricultural and the other pastoral. The
eastern part, included in the Prairie plains, contains some of the most
beautiful, gently rolling, and fertile agricultural lands in America.
But the western part is a treeless, almost waterless plain; yet thick,
low, sweet, nutritious grasses cover the entire surface, and render it
well adapted for the raising of large numbers of horses, cattle, and
sheep. Over western Nebraska not more than 15 or 20 inches of moisture
fall annually; the snows of winter are very light and soon pass away,
the winds rapidly gathering them into the valleys and gorges, leaving
vast areas entirely bare. The grasses, instead of decaying, as in all
temperate countries with a humid climate, slowly wither, retaining all
their nutritious qualities, and thus continue until April or May, when
the fresh shoots spring up, so that all kinds of stock thrive throughout
the winter on the open plains without artificial shelter. In this
account, however, the author cited fails to note that the winters are
frequently marked by exceedingly severe storms termed blizzards, during
which gales blow while the temperature is far below freezing, and that
at such times cattle have been known to perish by thousands.
In late summer and autumn the streams in this portion of the plateau
region for the most part become dry, although water may usually be
discovered at long intervals in pools in their beds. In ascending the
valleys the water appears and disappears as if by magic. Here one finds
a swift-running stream several yards broad, and then for a considerable
distance nothing is to be seen but a dry and dusty creek bed, resembling
a sunken roadway. Even the broad Platte has so far forgotten itself for
several seasons as to cease to be a running stream. It is not uncommon
for a river originating in the mountains on the west to be considerably
larger towards its source than near its mouth. Many of the important
streams that flow from the Black Hills towards the Missouri are lost on
their way through the plains. The Yellowstone and the Missouri, the two
most important rivers crossing the Great plateaus in the northern
portion of the United States, retain their existence throughout the
year, although becoming greatly shrunken in autumn, and send eastward a
never-ceasing tribute to the Mississippi.
_Northern Extension of the Great Plateaus._--The Great plateaus cross
the United States-Canadian boundary and extend northwestward through the
western portion of Assiniboia and Saskatchewan, and embrace nearly the
whole of Alberta and western Athabasca. At the international boundary
the plateau region is about 470 miles broad, and extends from longitude
103° 30' westward to the foot-hills of the Rocky Mountains, and in this
region embraces what is frequently termed the third prairie steppe,
known in part as the Missouri Coteau. The east border of this high
plateau throughout much of its extent is well marked by an escarpment
which descends some 300 or 400 feet to the second prairie steppe, which
together with the first or most easterly of the series, embracing the
Red River Valley, is usually considered as belonging to the Prairie
plains. The third steppe in the series, or the one extending from the
Red River to the Rocky Mountains, has an elevation along its eastern
border of about 2,000 feet, rises gradually to the westward, and attains
a general elevation of over 4,000 feet on its western border. All of the
region of the Great plateaus north of the international boundary,
with the exception of about 20,000 square miles tributary to the
Missouri, is drained by rivers flowing eastward to Hudson Bay or
northward to the Arctic Ocean. It is thus a portion of the northern or
arctic slope of the Continental basin. The eastern border of the plateau
country trends northwestward, and finally reaches the Rocky Mountains in
the vicinity of the head waters of the Mackenzie, but as this region is
but imperfectly explored, our knowledge of the boundaries of the natural
division of the continent we have been endeavouring to trace there
becomes indefinite. The Great plateaus in Canada merge into the Prairie
plains bordering them on the east, and in large part the position of the
dividing line between the two is arbitrary.
The portion of the Great plateaus in Canada, like the similar region to
the south, is covered with bunch-grass, which dries as it stands and
forms highly nutritious self-cured hay. Formerly this region was the
winter feeding-ground for vast herds of bison. The winters, although
cold, are not characterized by a heavy snowfall, and even in midwinter
the warm dry _chinook_ winds, as they are termed, similar to the _foehn_
winds of Switzerland, frequently cause the snow to disappear and leave
the brown plateau surfaces free for grazing. Now that the bison has
disappeared, this immense region is favourable in many ways for
stock-raising, but, unlike the lower prairies to the east with their
rich black soil and long hot summers, is not suitable for agriculture.
The main difficulties in the way of successful farming lie in the
dryness of the summers, and the scarcity of water available for
irrigation. The rivers flow in valleys several hundred feet below the
general plateau surfaces, and hence cannot be made available for
irrigating the uplands without too great an expense. In the bottoms of
the valleys, however, adjacent to the stream, limited areas are now
under cultivation, and it is to be expected that the wheat-fields of the
prairie region will be gradually extended into the valley to the
westward, and perhaps even to the eastern margin of the plateaus. A
greater extension of the wheat-belt to the north and west than is now
thought practicable has been predicted, but what the ultimate
limit will be cannot be told.
_The Black Hills of Dakota._--As stated in the brief account already
given of the Prairie plains, their monotony of surface and of geological
structure is broken by a single area of disturbance termed the Ozark
uplift. Similarly, the vast generally level expanse of the Great
plateaus is broken by a single rudely circular region of elevation, the
Black Hills of Dakota, which has been sculptured by atmospheric agencies
and given a diversified topography, in striking contrast with the even
monotony of the country surrounding it.
This protuberance on the surface of the Great plateaus is situated in
the southwest portion of South Dakota, and embraces also a part of
Wyoming, and about 140 miles east of the nearest range--the Big Horn
Mountains--of the Rocky Mountain chain. It rises from the surrounding
plateau to a height on an average of about 2,000 to 2,500 feet; the
highest summit, Harney Peak, is 3,000 feet above the plain, and 7,216
feet above the sea. The uplift is elliptical in ground plan, with a
northwest and southeast axis measuring about 120 miles, and a transverse
diameter of 40 to 50 miles. Its area is in the neighbourhood of 6,000
square miles.
While the generally level plateau surface about the Black Hills is
treeless, except for the scattered groves of wide-spreading cottonwoods
along the immediate banks of the larger streams, the central and higher
portions of the elevation itself is clothed with an open but abundant
forest, consisting principally of pines. The evergreen forests give to
the hills a nearly black colour when seen from a distance, and have
gained for them the name they bear.
The rocks which have been forced upward so as to form the Black Hills
dome were previously like those in the surrounding plain, quite
horizontal, and had a vertical thickness of at least 5,000 feet. The
uplift, if uneroded, would rise from the surrounding plain as a
flat-topped dome about 6,600 feet high, as is suggested by the highest
dotted line in the following diagram. In reality such a dome never
existed, for the reason that its growth was slow, and perhaps is
not completed even at the present day, and as soon as the rocks began to
rise, the rain, wind, streams, etc., commenced their task of
destruction. The higher the rocks were elevated the more powerfully
those agencies acted. The top of the dome was soon broken and its
internal structure revealed.
[Illustration: FIG. 18.--Ideal east-and-west section through the Black
Hills. The vertical scale is about six times the horizontal. The dotted
lines indicate the portion of the uplift removed by erosion. After Henry
Newton.
1. Archean slates and schists.
2. Granite.
3. Potsdam, sandstone, resting unconformably on 1 and 2.
4. Carboniferous, mostly limestone.
5. Red Beds (Trias), sandstone with included limestone.
6. Jura, shales.
7. Cretaceous, shales.
8. White River Tertiary, shales, resting unconformably on 7.]
By reference to the accompanying generalized section through the Black
Hills, which as the uplift is rudely circular would be essentially the
same if taken in any direction through the elevated region, it will be
seen that there is a central core of slate, schists, and granite which
has been forced upward so as to stand in its present eroded condition;
it rises well above the surface of the adjacent plateau. About this
central core the upturned edges of the sedimentary rocks form concentric
zones, the oldest in the series being next the schists, and the youngest
10 to 40 or 50 miles distant. It is the presence in the central part of
the hills of an area of resistant crystalline rocks which have weathered
into rugged forms, and the series of encircling and concentric belts of
rock of varying degrees of hardness and solubility, that has given to
the uplift its present peculiar relief and its generally beautiful
scenery. The edges of the harder belts form bold hills and ridges, while
the softer belts have been eroded into valleys. This series of
sharp-crested ridges and intervening valleys forms concentric circles
completely surrounding the central group of rugged mountains. The
largest and most interesting of the ring-like valleys is underlaid by
red sandstone, and is remarkable for its flaming colour as well as for
its exceptional form. In this Red Valley one may ride entirely around
the rugged central mass of the hills, on a generally level surface,
which is inclosed on its outer border by a precipitous wall of yellowish
sandstone and shale 300 or 400 feet high. The distance about this
"race-course," as it is sometimes termed, is about 200 miles. This
series of concentric ridges and intervening valleys, surrounding a high
and rugged region of more resistant rock, furnish an admirable
illustration of the influence of rock texture, hardness, etc., on
topography.
Another instructive geographical lesson afforded by the Black Hills is
the manner in which the portion of the dome rising above the level of
the rivers which flow across the surrounding plain has been dissected by
stream erosion. The streams originating in the central portion of the
uplift flowed outward in all directions, and have cut deep narrow gorges
through the ridges of hard rock in the base of the truncated dome. Some
20 streams originating in the central portion of the uplift cross Red
Valley and escape through notches in its outer wall, about 16 of which
are well-defined gateways leading to the encircling plateau. This is one
of the most beautiful and most instructive examples of _consequent_
drainage--that is, of streams whose direction has been determined by the
inclination of the surface over which they flow--thus far discovered.
Still another feature of much geographical interest is furnished by the
rivers on the adjacent plain, two of which, branches of the Cheyenne
River, cross the north and south extensions, respectively, of the Black
Hills dome. These streams flow directly across the arched strata, in
cañons of their own making, and, as explained by G. K. Gilbert, are
illustrations of _superimposed_ drainage--that is, the portions of the
dome crossed by the branches of the Cheyenne after the rocks were
upheaved were covered by soft horizontal lake beds, over which the water
flowed as consequent streams. The rivers deepened their channels and
cut through the soft cover of horizontal rock and into the arched
beds beneath. The course of the streams initiated on the covering of
soft beds were maintained, as the flowing water charged with sand cut
downward into the harder, upturned beds beneath, and now, the covering
of soft beds having been eroded away, the rivers flow directly across
(or through) the flanks of the great arch, but are not deflected by it.
In the neighbourhood of the Black Hills, and especially about their
northern and northwestern border, there are secondary hills formed by
the upward protrusion of molten rocks into the generally horizontally
stratified rocks underlying the plateau. These intrusions did not reach
the surface in such a way as to form volcanoes, but were forced upward,
raising domes above them, in which the structure is similar to that in
the great Black Hills dome. These secondary domes have been eaten away
by erosive agencies in varying degrees. In some of them, as the Little
Sundance Hill, near the town of Sundance, Wyoming, the dome of
stratified rock is unbroken, and no igneous rock is to be seen; other
neighbouring domes in which the plutonic magmas rose higher have been
eroded so as to expose the summit portion of the inner core; and in one
instance, known as Mato Tepee, the uncovering of the plug of plutonic
rock which caused the uplift is so complete that it now forms a
prominent fluted column over 600 feet high above its immediate base.
_Volcanic Mountains and Table-Lands._--In the south-central portion of
the Great plateaus in southwestern Colorado and eastern New Mexico,
there are several typical cinder cones with lava-flows associated with
them, which impart novel topographic forms to the general monotony of
the broad plateau surfaces. The highest of the extinct volcanoes in this
region is Mount Capulin, situated in northeastern New Mexico, about 200
miles east of the Rocky Mountains, which rises 2,750 feet above the
surrounding plain, and has an elevation of about 9,000 feet above the
sea. At the summit of this conical mass there is a well-defined crater a
mile in diameter. In the same region there are several other
similar volcanic cones, from which lava streams have descended. As has
been pointed out by R. T. Hill, these are the most easterly volcanoes of
recent geological age in North America. They were formed after the
Tertiary rocks of the Llano were laid down.
The Raton Mesa, situated between Mount Capulin and the front range of
the Rockies, is capped by a lava flow of more ancient date than the
volcanoes just referred to, which has protected the softer rocks beneath
from erosion, and now stands as a prominent table-land with precipitous
borders.
THE PACIFIC MOUNTAINS
To the west of the Continental basin is a vast cordillera composed of
numerous mountain chains which extends from south-central Mexico
northward to the Arctic Ocean, and in its broadest part is about 1,000
miles wide. As already explained, we speak of this region in its
entirety as the Pacific cordillera, or less technically as the Pacific
mountains. It is a highly complex group of mountain chains, each of
which contains two or more distinct mountain systems; each system,
again, is usually composed of many ranges, and each range is frequently
made up of a multitude of ridges, peaks, buttes, mesas, etc.; there are
also many plateaus more or less completely dissected by erosion, and
broad valleys, as well as numerous cañons, gulches, ravines, arroyas,
and other secondary topographic forms. This vast cordillera not only
contains mountains produced by the folding of the rocks of the earth's
crust, in a general way similar to the Appalachians in structure, but
also upturned blocks many miles in extent, bounded by breaks or faults,
and volcanic mountains, vast lava-flows, and elevations due to the
injection of molten rock into the earth's crusts so as to elevate domes.
In fact, scarcely any topographic form and no important geological
structure that is known is lacking in this great family of mountains
which dominates the western portion of the continent.
The Pacific mountains begin abruptly at the south, along a generally
east and west line passing some 75 miles south of the City of
Mexico, where the precipitous border of the table-land of central Mexico
overlooks a lower region to the south which is diversified by many
volcanic mountains. But little accurate information is available
concerning the geology and geography of Mexico, but in general, as is
well known, there are three main mountain belts which traverse that
republic. One of these mountain belts is adjacent to the Gulf of Mexico,
and another is situated near the Pacific coast of the main portion of
the republic, while the third forms the rugged and irregular axis of the
peninsula of Lower California. Between the leading mountain belts of the
mainland there are numerous short ranges and many nearly level-floored
valleys. The general level of this inland region is in the neighbourhood
of 6,000 feet, while the more prominent peaks and crests attain
elevations of from 10,000 to 12,000 feet. The general trend of the main
mountain belts, and of the numerous subordinate ranges, is about
northwest and southeast. For this reason, and also because the valleys
have become deeply filled with _débris_ from the mountains, travelling
in directions leading north and south is facilitated by the topography,
while in passing from one coast of the republic to the other the rugged
bordering mountain belts have to be crossed and detours made in order to
pass around the central mountain ranges.
The more elevated portion of central and northern Mexico, together with
the peninsula of Lower California, has an arid climate, to which many of
the conspicuous features in the geography of the land are due. The
precipitation over large areas is insufficient to maintain permanent
streams, the vegetation is nearly all of a desert-like character, and
several basins exist which do not drain to the sea. In the interior
basins there are saline and alkaline lakes, and numerous dry lake beds
or _playas_, which are whitened by saline efflorescences. The rocks
exposed in the mountains are largely of sedimentary origin, but a
characteristic feature is the geology, especially to the west, in the
presence of extensive volcanic areas and lofty mountains of igneous
rocks.
The Pacific cordillera begins in southern Mexico with a width of some
300 miles and broadens when traced northward. At the boundary between
Mexico and the United States it has a width of fully 700 miles, but
reaches its greatest breadth in the latitude of San Francisco and
Denver, where it is about 1,000 miles across. In its better known, but
as yet incompletely studied portion embraced within the boundaries of
the United States there are several important subdivisions, such as the
Rocky Mountain belt on the east; a less lofty, but yet rugged central
region, termed the Great Basin, characterized by having a dry climate
and by the fact that the streams do not reach the ocean; and a western
mountain chain which includes the Sierra Nevada and Cascade Ranges. To
the west of the mountains just named lies the great valley of
California, and similar regions in Oregon and Washington occupied in
part by Puget Sound. To the west, again, are the several ranges
bordering the Pacific coast from Lower California to Vancouver Island,
and termed in a general way the coast mountains. Each of the great
divisions of the Pacific mountain region has its indefinitely known
southern terminus in Mexico, and extends northward to beyond the
Canadian boundary. As this central portion of the most westerly of the
larger geographical divisions of the continent is well developed in the
United States, and has there been more carefully explored than
elsewhere, a review of its leading features will serve to give as good
an idea of the entire Pacific mountain region as is now practicable.
_The Rocky Mountains._--The limitations to the north and south of the
region to which this name is more or less specifically applied are not
well defined. Perhaps the most accurate statement at present permissible
is that the Rocky Mountains begin at the south, in northern Mexico, and
extend northward across the United States and Canada to near the shore
of the Arctic Ocean. On the east it is sharply defined by its junction
with the Great plateaus. Its western border, although less definite than
the eastern, is easily traced, at least across the greater portion of
the United States, by the marked contrast it presents to the
geographical conditions characteristic of the Great Basin region,
but owing to the many difficulties met with in attempting to adjust and
make use of the current nomenclature in classifying geographical regions
more or less artificial boundaries have to be accepted. The Great Basin
is so designated because it is a region of interior drainage--that is,
it does not send any tribute to the sea. Its boundaries are therefore
the crest-lines of the surrounding divides or water-partings. The Rocky
Mountains, on the other hand, are defined as an elevated region, the
boundaries of which are determined by relief and not by drainage. The
basis of classification in these two instances is not the same, and one
province overlaps the other. The streams flowing westward from the Rocky
Mountains into the Great Basin--such, for example, as Bear, Provo, and
Sevier Rivers in Utah--have their sources well within the Rocky Mountain
province as defined by uplift, but yet lie wholly within the Great Basin
province as defined by drainage. In spite of this inconsistency,
geographers recognise as the western border of the Rocky Mountains the
irregular and in part indefinite line where the elevated region breaks
down and meets the broad level-floored valleys characteristic of the
Great Basin. This line, or more properly belt of country, although
indefinite at the south, may for convenience be taken as beginning at
the head of the Gulf of California, and extending up the Colorado River
for about 300 miles, to where that river makes an abrupt bend, turning
southward after a westerly course through the Grand Cañon. From the
locality indicated, the boundary passes through central Utah, and is
sharply defined for most of the way by the bold western escarpment of
the Wasatch Range. In the neighbourhood of Great Salt Lake the border of
the mountain belt trends more and more to the northwest, crosses Idaho
diagonally, and in northern Washington merges with or closely approaches
the Cascade Mountains. In this northern region the border of the Rocky
Mountains is again indefinite, and until the geological structure of
western Canada is more thoroughly studied can only be located
provisionally.
The unsatisfactory condition of the nomenclature at present applied to
the larger topographic features of North America is illustrated by the
fact that to the north of the United States-Canadian boundary the term
_Rocky Mountains_ is much more restricted than is the custom in the
United States. In Canada this name is applied to the most easterly of
the ranges or chains of the Pacific cordillera. This difference in the
significance of the name referred to on the opposite sides of the
international boundary is unfortunate, but is due in large part to our
ignorance of the geography and geology not only immediately along the
boundary line, but generally throughout the rugged region of the
northwest portion of the continent.
One of the most important geographic features in the central part of the
United States is the presence in Wyoming of a broad, generally flat,
region known as the Laramie plateau (plains) and its extension westward
across nearly the entire width of the Rocky Mountains. The general
elevation of these "plains" is about 7,000 feet, or approximately 1,000
feet greater than that of the western border of the Great plateaus. The
Laramie plateau and country to the west having a similar topography,
furnished a convenient pass for the Union Pacific, the oldest of the
transcontinental railroads, and divides the Rocky Mountain belt into two
portions, which may be termed in a general way the northern and southern
Rocky Mountains respectively.
To the north of the Union Pacific Railroad there are several important
mountain groups, termed collectively the Stony Mountains by Lewis and
Clark in the report of their bold explorations across the continent in
1804, but not generally used since that time. This name has recently
been revived by J. W. Powell as a convenient term by which to designate
this large division of the Rocky Mountain belt, but unfortunately is not
recognised and has no significance to the north of the international
boundary. What the natural limitations of the Stony Mountains may be in
Canada remains to be determined.
The Stony Mountain system includes the Big Horn Mountains in
north-central Wyoming, the sharp and lofty Teton Range to the
south of the Yellowstone National Park, and several other rugged uplifts
of great extent in Montana and Idaho, and should the name be extended to
the north of the international boundary until a natural limit is
reached, it will include the Rocky Mountains of Canadian geographers
(the most eastern of the great uplifts constituting the Rocky Mountain
belt), together with the several ranges of the Gold Mountains. These
several mountain ranges and groups of ranges appear to have diverse
geological structure, but their histories are by no means thoroughly
understood. Some of them, as stated by Powell, are carved out of broad
folds, and involve both originally deeply seated igneous and metamorphic
rocks and upturned and folded sedimentary beds; while others are due to
movements along lines of fracture and in part of overthrust.
The Stony Mountains form a portion of the continental divide which parts
the waters flowing to the Pacific from those that find their way to the
Atlantic. The thousands of streams tributary to the Missouri head
against the equally numerous fountains supplying the westward-flowing
Columbia. The broad valleys between the several ranges have a general
elevation of between 7,000 and 8,000 feet, and the bold, massive
mountains rise from 10,000 to over 13,000 feet above the sea. Owing to
the considerable elevation even of the valleys, and the northern
position of the region here considered, as well as its distance from the
equalizing influence of the sea, the extremes of climate are strongly
marked. The summer season is comparatively short, and in the valleys the
heat is intense (ranging from 90° to 112° F.) and the rainfall small or
none at all, while the winter season is cold (temperatures of from -15°
to -30° F. being frequent) and accompanied by an abundant snowfall,
especially on the mountains. Agriculture, although carried on in the
valleys, is of comparatively small importance, and is usually dependent
on irrigation. The mountains are snow-covered through much of the year,
and small glaciers occur about the lofty summits of the Teton Range and
on the mountains near the international boundary and in Canada. The
valleys are generally destitute of trees except along the
streams, where white-trunked cottonwoods spread their green leaves in
summer and become a tracery of golden yellow in the autumn, marking the
courses of the life-giving waters. The lower mountain slopes are covered
with dark forests of pine, spruce, and juniper, which increase in
density and extent as one follows the ranges northward until the
influence of the high northern latitude is felt, and in northern Canada
the zone of the subarctic forest is reached.
In the central part of the Stony Mountains is situated the justly famed
Yellowstone National Park, which is truly remarkable for its fine
scenery, its deeply carved and gorgeously colored cañons, and most of
all for its numerous hot springs and spouting geysers. This is the only
geyser region on the continent, and the most extensive of the three now
existing in the world.
The finest scenery of the northern division of the Rocky Mountain belt
lies to the north of the international boundary, and within recent years
has been rendered accessible by the building of the Canadian Pacific
Railroad. It is in this region that the mountains are highest, most
rugged, and clothed most completely with the dark, sombre, evergreen
northern forests. Here, too, high up among the bare serrate mountain
tops, and mostly above the timber-line, are found the largest of the
glaciers in the Rocky Mountain belt. This wonderful region of rugged
mountains, deep and formerly glacier-filled valleys, impetuous rivers,
and dense forests has only recently become known to the world at large.
Vast areas, no doubt as attractive as those about Banff, Lake Louise,
Glacier House, etc., already famous, remain to be discovered and
described.
In the fastnesses of these wild northern Rockies moose, elk, deer, bear,
mountain-sheep, and mountain-goat still abound. The buffalo (bison) is
protected in the Yellowstone National Park, and will probably be
preserved from extinction. A small herd also survives in Canada. The
streams, except those flowing from glaciers, are bright, clear, and
swift, and are well stocked with fish. The trout, represented by several
species, there finds the cool retreats so essential to its life. To the
sportsman and skilled angler the northern Rockies are a paradise.
Among the lofty mountains and in the larger valleys there are many
lakes, more especially in northern Idaho and Montana and in Canada. Many
of these, and particularly those near the heads of the valleys and about
the more lofty peaks, are true rock-basin lakes, worn out by the
grinding of sand-charged glacial ice when the glaciers were far more
extensive than now. The large lakes situated in the trunk portions of
the broad-bottomed valleys are in many instances retained by dams of
glacially deposited detritus and record the changes in the aspect of the
land inherited from the Glacial epoch. These numerous lakes present a
vast variety of scenery, and in many instances reflect from their placid
mirror-like surfaces as beautiful and inspiring pictures of rugged
grandeur as can be found in the world. The natural beauties of the
classical lakes of Switzerland and Italy are rivalled by many of the
charming water bodies of the northern Rockies, which but few men
appreciative of the beauties of nature have ever seen.
To the south of the Laramie plateau the mountains of the Rocky Mountain
system are more irregular and more lofty than those to the north of that
break. The many rugged ranges in southern Wyoming, Colorado, and
northern New Mexico form a great group, to which the name Park Mountains
has been applied by J. W. Powell. The several ranges composing this
group have a general north and south trend, to which, however, an
exception is furnished by the Uintah Mountains in southwestern Wyoming
and eastern Utah, which consists of a deeply dissected east and west
fold or broadly uplifted plateau. Intervening between several of the
adjacent ranges there are wide, nearly flat-bottomed valleys, which owe
their leading characteristics to the deep filling of depressions by
_débris_ carried from the bordering mountains by the wind and streams.
These broad valleys surrounded by rugged peaks are known as parks, and
the numerous ranges among which they are situated are hence designated
the Park Mountains. The term by which the valleys are known is in some
respects misleading, as the word _park_ usually carries the idea of a
diversified and in part forested region, with mild, picturesque
scenery. Perhaps a city park or the beautiful rural estates of England
are most usually brought to mind when the term referred to is mentioned.
But in the great mountains of the central portion of the continent one's
idea must expand to keep in harmony with his surroundings. The natural
parks of that region are broad, generally treeless, valleys with winding
streams, the uplands are grass-covered and rolling, and in distant views
the courses of the streams are marked by narrow belts of verdure. The
picture is framed by a succession of mountain domes and embattled
cliffs. Over all arches the dark blue, cloudless sky of a nearly
rainless region. In the clear air distances are deceptive, and what
appear to be miles to the novice must be extended to leagues in order to
acquire adequate conceptions of the magnitude of the scene.
The most famous of the great tracts of generally level land surrounded
by the high ranges of the Park Mountains is San Luis Park, situated in
southeastern Colorado and extending southward into New Mexico, which has
a length from north to south of about 130 miles, and is from 20 to
nearly 40 miles wide. Its general elevation is between 7,000 and 8,000
feet. This great valley, level-floored with soft deposits swept in from
the bordering highlands, and almost completely surrounded by rugged
mountains, although more desolate than the majority of the numerous
similar valleys in the same region, is typical of its class. The Rio
Grande winds through its entire length and many streams rising in the
bordering mountains flow to the valley during the winter season, but in
summer, owing to the high temperature, active evaporation, and small
rainfall, only a few of the larger of these mountain-born torrents reach
the main, southward-flowing river. In the southern portions of the
valley large areas are covered with drifting sand, which is fashioned by
the winds into ever-changing dunes of a creamy whiteness. Some of the
streams from the mountains expand on the plain and form the San Luis
lakes, from which the water escapes by evaporation, thus causing them to
become alkaline. The land bordering the lakes is whitened as with
snow by saline incrustations. On the lower portion of the rim of this
mountain-inclosed basin there are scattered groves of pines and
junipers, and at higher elevations the mountains are dark with forests.
The more lofty peaks, however, rise far above the upper limit of the
forests and are rugged and magnificent even under the glare of a
cloudless sky.
To the east of the San Luis Park, and rising about 7,000 feet over it,
and over 14,000 feet above the sea, stands Sierra Blanca, one of the
finest of the many majestic mountains of Colorado. In summer immense
cloud banks frequently gather about this cold, isolated peak, and local
storms, accompanied by fierce lightning and echoing thunder, beat upon
its shrouded sides. These tempests raging on the mountain top, while the
adjacent valleys are flooded with sunlight, recall the scriptural
accounts of the storms of Mount Sinai. In fact, the southwestern portion
of the United States and the adjacent region in Mexico, so far as
scenery and climatic peculiarities are concerned, have much in common
with Palestine.
The other great parks in Colorado, which have suggested a name for the
group of mountains in the midst of which they are sheltered, are less
arid and less desert-like than the one just described; but like it,
derive their magnificence and fascination from their vast extent, the
sublimity of the bordering mountains, and the wonderful transparency of
the air above them, rather than from the topography of their nearly
level floors or the vegetation that strives ineffectually to clothe
their nakedness.
The individual summits as well as the separate ranges composing the Park
Mountains are remarkable for their massiveness and the great height of
their bare rounded summits rather than for picturesque details. Several
of the peaks are among the highest in the United States. One conspicuous
feature is the considerable elevation of the valleys, usually over 7,000
feet, and the large number of lofty summits. Of the peaks that have been
measured, over 30 exceed 14,000 feet in height. The portion of the Park
Mountains above an elevation of 10,000 feet, as is indicated on
the map reproduced on page 65, is far greater in area than
any other region of similar altitude on the continent.
In the Park Mountains, and generally throughout the southern Rockies,
even to central Mexico, the forms that meet the eye are the remnants of
vast upheaved folds and domes of the earth's crust sculptured and
degraded by erosion. The nearly horizontal rocks of the Great plateaus
on meeting the eastern border of the mountains are bent abruptly upward,
and in many places stand on edge or have been overturned so as to dip
westward. This abrupt upward bending and the presence of remnants of the
same beds on the summits of some of the higher mountains shows that the
strata have not been simply folded into anticlinals and synclinals, but
that there has been a thickening and upswelling of the rocks beneath.
In the northern Rockies, except in western Idaho and adjacent portions
of Washington and Oregon, evidences of recent volcanic activity are
rare, although igneous rocks cover great areas, and in the Yellowstone
Park numerous geysers and hot springs bear evidence to the presence of
abnormal heat in the earth's crust. In the southern Rockies, however,
volcanic mountains which still preserve their forms are numerous in
certain regions, and in Mexico there are mighty volcanic piles and many
lesser elevations built up by extrusion of molten material, some of
which are still active. Examples are furnished of volcanic mountains
ranging from perfect cones with curved slopes typical of the forms
produced by the piling up of various sized fragments about the vents
from which they were extruded, to irregular serrate peaks which reveal
the anatomy of the dissected volcanic masses, and even the dikes which
remain after the surface elevation of a volcano has been removed. The
most modern volcanoes in this great group of mountains are situated in
central Mexico, but others nearly as perfect in form occur in New Mexico
and Arizona, and in the plateaus to the east of the Park Mountains. The
Spanish peaks in southeastern Colorado are instructive illustrations of
the topographic forms produced when a volcanic mountain has been deeply
dissected.
In the formation of volcanic mountains there is an extrusion of molten
and fragmentary material accompanied by an escape of great volumes of
steam at the surface. Closely related to this phase of vulcanism is the
injection of molten material into the earth's crust from below, so as to
force its way between stratified beds and produce intruded sheets. In
this latter process the sheets of injected material may be thin in
comparison to their lateral extent or thick lens-shaped masses. In the
production of either of these forms of intrusion the cover above the
injected material is lifted and a change is made in the topography of
the surface. The intrusions, which are thick in comparison to their
lateral extent, are known as _laccoliths_. At times intrusions of this
nature are of such thickness that they produce true mountain forms. If
unmodified, these elevations would be domes, but when their surfaces are
broken by erosion and their dissection and removal progresses they
frequently assume rugged, serrate forms.
The type of laccolithic mountains made known some years since by the
studies of G. K. Gilbert is furnished by the Henry Mountains, in
southern Utah. More recently it has been found that this interesting
phase of mountain building is illustrated by many other examples in the
Rocky Mountain region and elsewhere.
The rocks exposed at the surface in the southern Rockies, as in the
northern division of that great chain, embrace almost every variety
which enters into the composition of the earth's crust. The central
cores of many of the now deeply eroded ranges consist of granite and
other similar rocks, and are surrounded by sedimentary beds which range
in age from the oldest stratified rocks now known to the youngest.
Igneous rocks in great variety and in all forms incident to an extruded
or volcanic and intruded or plutonic origin are present. The many
disturbances that have occurred have led to the formation of mineral
veins and the impregnation of rock masses with ores of various
kinds--such as gold, silver, lead, copper, etc.--which have been mined
with great success at many localities.
_The High Plateaus._--To the west and south of the Park Mountains, and
situated in the western portions of Colorado and New Mexico, eastern and
southern Utah, and northern Arizona, there is an extensive region having
a general surface level of 6,000 to 7,000 feet above the sea, known as
the High plateaus. This region has suffered great erosion and is deeply
trenched by stream-carved cañons. Although not mountainous in the
ordinary acceptance of the term, its surface is rugged and difficult to
traverse, particularly on account of the deep cañons that intersect it
in every direction.
The High plateaus are a part of the Rocky Mountain region and bear a
somewhat similar relation to the Park Mountains that the Alleghany
plateau does to the Appalachian Mountains. Streams flowing westward from
the Park Mountains and from the southwestern portion of the Stony
Mountains unite to form the Colorado River--the one great drainage
channel of the region. The importance of this remarkable river in the
history of the land has led to the adoption of the name Colorado plateau
by Powell and others for the region under consideration. As with so many
of the grander geographical units of the continent, the precise limits
of the one here considered are difficult to define; but in spite of this
uncertainty as to meets and bounds, the now classical writings of
Newberry, Powell, and Dutton especially have shown that a strange and
wonderful land exists in the southwest part of the United States, which
is of unusual interest to geologists and geographers.
The High plateaus are underlaid by nearly horizontal rocks. The larger
elements in the structure are great blocks of the earth's crust
measuring some 60 to 100 miles on their various borders, which are
bounded by breaks (faults), or by what are termed monoclinal folds or a
change from one plateau to another by a single bend in the strata. The
rocks in each of the separate plateaus are usually gently tilted. Their
eroded edges stand as lines of massive, gorgeously coloured, and
frequently fantastically sculptured cliffs. These cliffs, when seen from
below, appear as rugged mountain ranges, but to an observer standing on
their deeply sculptured crests are easily recognised as the
upturned edges of large gently tilted blocks of the earth's crust.
The basement rocks beneath the High plateaus are very ancient granites,
schists, etc., which formed a land surface and were greatly eroded
before the first of the superimposed stratified beds were deposited upon
them. The first of the sheets of sediment laid down by the primeval
ocean belong to the oldest rocks containing records of life that have as
yet been recognised--the Algonkian (pre-Cambrian) terranes of modern
geology. Above these come other deposits of sandstone, shales,
limestone, etc., representing a wide range of geological history, and
including as the upper member of the series the sediments of large
Tertiary lakes. This vast succession of stratified rocks, some 13,000
feet in thickness, has been upraised in a broad way, without the
crumpling and folding, but broken, as stated above, into great blocks
which are now variously inclined, but still preserve a plateau-like
character.
Besides the movements in the earth's crust which raised the plateaus and
caused fractures and simple or monoclinal folds in the rocks of which
they are composed, there occurred volcanic eruptions which produced
numerous cinder cones, extensive lava-flows, and widely spread sheets of
comminuted material known as lapilli, dust, and so-called ashes.
Although the history recorded in the rocks forming the High plateaus is
one of fascinating geological interest, the easier and more obvious
lesson that the region has to offer, more especially to the geographer,
has been engraved and etched on its surface by streams and wind-blown
sand.
On the High plateaus the rainfall is comparatively small, and the
streams originating there mostly ephemeral. But on the mountains to the
east and north the precipitation is more abundant and rivers are formed
which flow across the plateau region. The Green and Grand Rivers, fed by
many tributaries, unite to form the Colorado, which flows southwestward
for some 700 miles and discharges its muddy waters into the Gulf of
Lower California. This great river year by year and century after
century has deepened its channel through the plateau region where the
rainfall is small, more rapidly than the general surface has been
lowered by erosion. The main conditions are a broad area of nearly
horizontal rocks, raised high above the sea or above the base level of
erosion, and an arid climate; crossing this region is the ever-flowing
river, which, acting like an endless saw, cuts deeper and deeper into
the blocks of the earth's crust which have been raised athwart its
course. Resulting from these conditions is a mighty trench or cañon,
which is by far the most magnificent of its kind in North America, if
not in the world. Not only has the main river sunken its channel into
the earth to a depth of more than a mile throughout a large portion of
its course, but each tributary stream has been engaged for a long period
of time in a similar task. Although most of the streams originating on
the surface of the plateaus are ephemeral, they work rapidly when the
occasional heavy rains flood their channels. This deepening of the
stream channels, while their borders and the intervening portions of the
plateau surface suffered but comparatively slight erosion, has produced
a wonderful system of deep steep-sided trenches in the borders of which
the edges of the dissected rocks are exposed in nearly vertical
precipices.
[Illustration: FIG. 19.--Grand Cañon of the Colorado River. After W. H.
Holmes.]
Aside from the lessons of interest to the geologist and geographer so
plainly engraved on the surfaces of the plateaus crossed by the
Colorado, the region has a wonderful fascination for the purely æsthetic
feelings more or less latent in every human breast. To one traversing
the open pine forests, in places clothing the plateaus and inclosing
many grassy glades and flower-decked parks, in which timid deer may
frequently be seen feeding in the early morning, and emerging on the
brink of the Grand Cañon, the scene that meets the eye is marvellous
beyond all description. C. E. Dutton, to whom we owe some of the most
graphic and inspiring descriptions of natural scenery ever written,
states that those who have long and carefully studied the Grand Cañon of
the Colorado do not hesitate for a moment in pronouncing it the most
sublime of all earthly spectacles. "If its sublimity," writes
Dutton, "consisted only in its dimensions, it could be sufficiently set
forth in a single sentence. It is more than 200 miles long, from 5 to 12
miles wide, and from 5,000 to 6,000 feet deep. But it is not magnitude
alone that gives this marvellous cañon its prominence; it is the
gorgeous and varied colouring of its mighty walls, the endless details
in the sculpturing of its battlements and towers, the ever-changing
atmospheric effects of its profound depths, and the wonderful stimulus
to the imagination with which it feeds the mind. Standing on the brink
of the Grand Cañon, the prosaic search for causes and effects for a time
at least must be laid aside, and give place to the emotions."
Wonderfully grand as are the scenes beheld in traversing this region of
high plateaus, with its magnificent cliffs and profound cañons, one is
constantly reminded that it is an arid land. The higher portions of the
plateau, it is true, are in places forested, but over vast areas the
rocks are bare. Water is everywhere scarce except in the bottom of the
larger excavations. Thirsty, and perhaps perishing, the traveller,
Tantalus like, looks down on the shining silvery threads of water in the
cañons, hundreds and even thousands of feet below, but separated from
them by impassable barriers. To the south the plateaus descend to the
desolate valleys of southern Arizona, where strange gigantic
cactus-plants and scattered clumps of thorny shrubs alone break the
dreary monotony of the hot gravelly deserts. Agriculture is there
impossible without irrigation, but where the life-giving waters can be
utilized, as in the Gila Valley, marvellous productiveness follows.
THE GREAT BASIN
To the west of the Rocky Mountain belt in the United States there exists
a region embracing about 210,000 square miles, which sends no stream to
the ocean. This vast and in large part desert tract is known as the
Great Basin. The climate is characterized by its aridity. The annual
precipitation is small and evaporation active. All the water reaching
the land is returned to the air by evaporation, either directly or from
the streams and lakes. Many of the lakes do not overflow and are more or
less alkaline and saline, while some of them, as Great Salt Lake, Utah,
and Mono and Owens Lakes, California, are dense with mineral matter in
solution.
[Illustration: FIG. 20.--The Great Basin.]
The Great Basin is not a single level-floored depression, as one might
infer from its name, but is traversed by rugged mountain ranges, which
divide it into a large number of minor valleys. Some of these secondary
basins have lakes and streams which escape from them into lower
depressions, but in many instances under present climatic conditions
they have no surface water, all the moisture that reaches them being
absorbed by the thirsty soil or evaporated without forming lakes. The
Great Basin proper, as it may be termed, embraces nearly the whole of
Utah and Nevada, together with small portions of the southern parts of
Idaho and Oregon and a large area in southeastern California. While the
drainage conditions limit the application of the name to this group of
associated basins which send no tribute to the sea, the climatic and to
a less extent the topographic and geological conditions that
characterize it have much wider, although indefinite boundaries. This
wider region which resembles the Great Basin proper, extends from
British Columbia southward to beyond the city of Mexico, and includes
the eastern half of Washington and Oregon, a large part of Idaho, and
much of Arizona, New Mexico, and western Texas. In this outer region
both to the north and south of the Great Basin proper there are
drainless valleys, as those of central Mexico, in which the conditions
characteristic of the desert valleys of Utah and Nevada are repeated.
The greater region of arid valleys and desolate mountains surrounding
the Great Basin proper is crossed at the north by the Columbia and in
the central part by the Colorado. Each of these large rivers has its
source in the Rocky Mountains and flows to the Pacific.
The most obvious features of the Great Basin and of the northward and
southward extensions of the belt of country having much in common
with it, depend on climatic conditions. The rainfall is small throughout
the entire belt from the Canadian boundary to south-central Mexico. The
average mean annual precipitation, judging from such observations as are
available, is probably less than 15 inches, but this broad statement
does not truly represent the diverse conditions. The rainfall is
confined almost entirely to the winter season, and frequently comes in
short heavy downpours. During the summer season, the valleys especially,
become so parched that only such plants can grow as are adapted to
long-continued droughts. The topography is rough and diversified by many
mountain ranges, and the precipitation is more abundant on the uplands
than in the valleys. Over large areas in Nevada and southeastern
California the mean annual rainfall is less than 5 inches. The author,
while carrying on geological work in this region, was informed by some
of the older settlers that at times for fully eighteen consecutive
months no rain whatever fell in certain of the valleys. From the
accounts of travellers in central Mexico, it seems as if some of the
interior basins in that region must be fully as arid as those just
referred to.
One conspicuous result of the lack of moisture is the absence of
forests. Except on the mountains mainly at the north the Great Basin and
its extensions, as defined above, is nearly destitute of trees. The
valleys are in many instances thickly covered with desert shrubs,
notably the sage-brush, but the floors of the driest basins are in many
instances almost absolutely without vegetation, and are frequently white
with saline incrustations.
Many of the depressions in the Great Basin, as well as some of the
outlying valleys referred to, have rivers and lakes which exhibit
certain interesting features that are unfamiliar to people dwelling in
humid lands. The streams are fed in part by the small precipitation on
the desert valleys, and by springs, frequently of heated water, but
mainly by the rain and melting snow on the mountains. Many rills and
rivulets are born on the valley sides of a single storm, but are
absorbed by the thirsty soil or evaporated during the succeeding hours
of sunshine. Other streams have a greater lease of life and flow
down to valleys and basins, suffering evaporation and absorption as they
progress, which cause them to diminish in volume, and finally to vanish.
The stronger streams, such as Sevier and Bear Rivers in Utah, the
Humboldt River in Nevada, and the Truckee River in California, maintain
their existence throughout the year, and expand into lakes in which the
inflow is balanced by evaporation.
The lakes of the Great Basin present even greater diversity than the
streams. Some of those situated principally in the mountains are of
pure, limpid, wholesome water, supplied by cool, sweet brooks and rills
or by the melting of the winter's snows, and overflow throughout the
year. These lakes, usually of small size, are similar in all respects to
the ordinary lakes of humid lands. In eastern Utah, adjacent to the west
base of the Wasatch Mountains, the Provo River and other streams supply
Utah Lake, the outlet of which, the Jordan River, empties into Great
Salt Lake. Utah Lake is well within the Great Basin, and situated at a
low elevation for the region, namely, 4,500 feet, or about 280 feet (in
1873) above the level of lake of brine into which it discharges. This is
the largest of the fresh lakes in the valleys of the Great Basin, and
owes its existence to the fact that a depression there occurs which is
filled to overflowing by the streams from the mountains. Bear Lake, in
northeastern Utah, is another exceptional example of a fresh lake of
considerable size at a comparatively low altitude, in the same region.
On the western rim of the Great Basin, at an elevation of 6,247 feet,
and surrounded by the forested peaks of the Sierra Nevada, lies Lake
Tahoe, "the gem of the Sierra," a water body of remarkable purity, which
discharges through Truckee River into Pyramid and Winnemucca Lakes.
These lower lakes, situated in desert valleys at an elevation of 3,780
feet above the sea, are without outlets and alkaline and bitter. The
most characteristic lakes of the Great Basin, however, are those that do
not overflow, and on account of concentration by evaporation are more or
less highly charged with mineral matter in solution. These saline and
alkaline lakes may be divided into two classes, in reference to
their duration, but the line of separation is indefinite. Certain of
them have maintained their existence for many years, and probably have
not been evaporated to dryness for several centuries, and may be classed
as perennial lakes; others are evaporated to dryness each year, or
during certain exceptionally dry and hot seasons, and may be termed
ephemeral lakes. In many instances the beds of the ephemeral lakes are
normally in a state of desiccation, and appear as broad, level, mud
plains, usually with a white fringe of saline matter. Frequently these
mud plains, or _playas_, as they are termed, are transformed into
shallow lakes during a single storm, but the waters are absorbed by the
clays beneath or evaporated within a few days or perhaps a few hours
after the rain ceases. The largest and most characteristic of the
perennial saline water bodies is Great Salt Lake, the counterpart in
many ways of the Dead Sea. The streams discharging into this salt sea
have the usual purity of river-waters, and carry but a small fraction of
one per cent of saline matter in solution. The lake is supplied also in
part, but to an unimportant extent, by springs, the most of which are of
essentially fresh water. The source of the salts which make the waters
of the lake a brine is evidently, therefore, the small percentage of
mineral material brought in by the tributary streams. After reaching the
lake these fresh waters, in the ordinary meaning of the term, are
concentrated by evaporation. This is the explanation of the leading
facts in the chemistry of all of the saline and alkaline lakes of the
Great Basin region, such as Pyramid, Winnemucca, and Walker Lakes in
Nevada, Mono and Owens Lakes in California, and the saline lakes of
Mexico.
The volume of a lake without an outlet, or an "inclosed lake," is
determined mainly by the ratio of the inflow (including the rain falling
directly on its surface and the tribute from springs) and evaporation.
Its volume, and consequently its area, fluctuates from season to season,
and frequently varies also during periods embracing several years. With
variations in volume there are fluctuations in the percentage of saline
matter in solution, even if precipitation of one or more of the
contained salts does not take place during the periods of more than
usual concentration. In most instances inclosed lakes are concentrated
by evaporation in summer seasons, and perhaps become nearly saturated
solutions, but are diluted during the rainy winter seasons. Fluctuations
in volume, area, depth, salinity, etc., are thus characteristic of
inclosed water bodies. They are sensitive to climatic changes which
ordinary weather records fail to detect, and are modified in a
conspicuous manner when the country about them becomes inhabited and
irrigation is practised.
Some of the lakes of the Great Basin are dense brines from which various
substances are being precipitated. The economic importance of these
natural reservoirs of brine and of various soda salts is great, and will
become more and more important as transportation facilities increase.
Great Salt Lake, it has been estimated, contains 400,000,000 tons of
common salt and 30,000,000 tons of sodium sulphate in solution. During
the past ten years about 40,000 tons of common salt have been harvested
from it annually. Mono Lake contains some 245,000,000 tons of saline
matter in solution, of which about 92,000,000 tons are sodium carbonate
and bicarbonate. Owens Lake is similar to Mono Lake in composition, and
is now the basis of a large soda industry.
A marked difference between a region which drains to the ocean and one
where the streams enter inclosed basins where their waters are
evaporated is that in the former the waste from the land carried by the
streams as an invisible load in solution or as a visible load consisting
mainly of silt and sand in suspension is contributed to the ocean and
widely distributed before being deposited--much of the material in
solution, in fact, may be said to be a permanent contribution to the
salinity of sea-water; but in most instances where streams enter
inclosed basins all of the material contributed both in solution and
suspension is sooner or later precipitated. The area within an inclosed
basin, on which the inflowing streams lay down their loads, is as a rule
less extensive than the area that is being denuded to supply the
material. The receiving basins are thus filled in or _aggraded_, and
there is a concentration both of the mechanical wash from the land and
of the substances taken in solution by the waters of streams and
springs. A marked result of this process of concentration, particularly
of the fine waste of the uplands and mountains, is seen in the
approximately level floors of inclosed valleys. Throughout the Great
Basin the valleys have been filled to a depth in many instances of
hundreds of feet. Some of the lower mountain ranges in Utah have been so
nearly buried beneath these valley deposits that only their summits,
termed _lost mountains_, appear above the even surface of the desert
plains. This _débris_, deeply filling the valleys referred to, is
usually a fine yellowish dust-like material, similar in many ways, and
probably in mode of origin, to the _loess_ of China in which geologists
have taken much interest. With the concentration and deposition of the
fine mechanical wash of the uplands there has also been a concentration
of the more soluble saline constituents of rocks, which causes the soils
of arid regions to differ in an important way from those of humid lands.
The leached and characteristically red-tinted soils of warm humid
countries, consisting of the oxidized residue of deeply weathered rocks,
are absent from arid regions; in their place we find minutely
disintegrated, usually light-coloured, and not chemically impoverished
soils. In warm humid regions chemical decay of the rocks is the
conspicuous feature; in equally warm arid lands mechanical
disintegration is carried to an extreme, without the removal of the more
soluble constituents. In fact, concentration of saline matter, notably
common salt, sodium sulphate, gypsum, etc., is one of the functions, so
to speak, of arid climates, when the requisite evaporation basins are
present. Among the important industries of the Great Basin region is the
gathering and purifying of the various salts contained in the existing
water bodies and in the basins of desiccated lakes.
In addition to the characteristics of the region referred to above,
which are mainly the result of climatic conditions, the Great Basin has
certain geological features, in the main, so far as North America
is concerned, peculiar to itself. The leading structural features of the
rocks, so far as they find expression in the surface relief, is the
presence of a large number of extensive faults trending in general about
northeast and southwest. These faults are breaks or cracks along which
the rocks have been moved up and down. One side of a fault sometimes
stands higher than the opposite side, and forms a narrow and frequently
high and rugged mountain range. The number of these faults within the
Great Basin is as yet unknown, but they certainly number many hundreds.
In a cross profile of the region between the Wasatch Mountains on the
east and the Sierra Nevada on the west the number of mountain ridges due
to faulting is at least a score. The precipitous western border of the
Wasatch Mountains is itself a great fault scarp, as is also the eastern
border of the Sierra Nevada. The faults that determine the steeper sides
of these mountain ranges are not to be considered as single clean-cut
gashes, but as irregular and intersecting fractures traversing a narrow
belt of country. The faults referred to divide rocks of all ages, and
are evidently due to the most recent disturbances that have affected the
region. It is not probable that the break in any given instance was
formed all at once. Such vast convulsions would be out of harmony with
the rules of nature. But rather many small movements and adjustments of
pressure have occurred along the same belt of fracture. This conclusion
is sustained by the fact that many of the faults have experienced
movements in very recent times. In places fault scarps a score or more
feet in height cross the alluvial cones at the mouths of the small
high-grade valleys in the mountains. These scarps in loose
unconsolidated gravel and similar material, even under an arid climate,
could not be expected to preserve their freshness for many years. At
times the breaks cross the courses of streams and cascades, and rapids
are formed by the waters flowing down escarpments thus produced in loose
material. One characteristic fault scarp in Inyo Valley, California, is
known to have been formed during an earthquake that shook that portion
of the country in 1872. The many small earthquakes that have been
felt in the Great Basin region are believed to have been caused by
slight movements along the breaks that traverse the region. This and
other evidence indicates that the faults to which so much of the
characteristic scenery of the Great Basin is due have grown by repeated
minor displacements, and that such movements are a common cause of
earthquakes.
The most conspicuous topographic features of the better known portion of
the Great Basin are long, narrow, and frequently sharp-crested ridges,
with a gentle slope on one side and a steep escarpment on the other. The
steeper side in a large number of instances is known to be the upraised
side of a fault. Each of these basin ranges, as they are termed, may be
considered as the upturned edge of a block of the earth's crust, in
general from 60 to 100 or more miles long, and 10 to perhaps 20 miles
wide. The crest-lines of the tilted blocks are frequently serrate, on
account of differences in the hardness and texture of the rocks and the
effects of weathering. There is frequently, however, an older structure
revealed in them, showing that the region was folded and otherwise
disturbed previous to the later movements which produced the leading
features in the present topography. It is probable that this older
structure in some instances has had an important bearing on the forms of
some of the ranges, but our knowledge in this direction is too limited
to warrant presentation in a popular treatise.
Many of the basin ranges are imposing on account of their height and
ruggedness, when seen from the adjacent, deeply filled valleys, although
scarcely more than half of their actual elevation above the sea is
revealed from such points of view. Exceptions to this general statement
occur, however, in southeastern California, where, in Death Valley, the
land is 480 feet below sea-level. This is the only region in North
America which, like the basin of the Dead Sea, is below the level of the
ocean's surface. On the border of Death Valley the mountain ranges rise
from 6,000 to 10,000 feet, and the highest summit, known as Telescope
Peak, is reported to have an elevation of nearly 11,000 feet
above the sea. In the central and northern portions of the Great Basin
the valley floors have a general elevation of from 5,000 to 6,000 feet.
The mountains rise from these valleys to a height of from a few hundred
to 4,000 or 5,000 feet. Among the highest, if not actually the
culminating peaks well within the Great Basin are White Mountain, on the
California-Nevada boundary, about 30 miles southeast of Mono Lake, which
has a summit elevation of 13,000 feet, and Jeff Davis Peak, in eastern
Nevada, which rises 13,100 feet above the sea and 8,000 feet above the
adjacent valleys.
The numerous sharp-crested ranges of the region under review are
frequently remarkable for the richness of the colours of the naked
rocks. The mountain slopes and towering angular summits when outlined
against the morning or evening sky are frequently as brilliantly dyed as
are the New England hills when clothed in the harlequin foliage of
autumn. Before sunrise and after sunset each serrate crest-line is the
sharply cut border of a silhouette of the deepest and richest purple.
The diversity of scenery in the Great Basin is increased by mountains of
volcanic origin, including several modern craters, some of which hold
lakes, and by lava-flows of recent date, and by great alluvial fans or
detritus cones which stream out into the valleys from the mouths of
gorges in the bordering mountains.
The Great Basin proper, with its rugged topography and arid climate, is
not an agricultural region. Small portions of it, however, when water
can be had for irrigation, have been transformed into fruitful farms and
gardens which yield bountiful returns. But even a century hence, when
all has been accomplished in the way of reclaiming the arid valleys that
can be done by utilizing the available water for irrigation, only a
small per cent of the whole will be under cultivation.
SIERRA NEVADA AND CASCADE MOUNTAINS
To the west of the Great Basin, and extending from southern California
northward to beyond the United States-Canadian boundary, there is a
lofty and extremely rugged belt of mountains consisting of two
ranges--the Sierra Nevada at the south and the Cascade Mountains at the
north. Topographically, these two ranges form a single elevated belt of
country, but custom, and as is now generally understood the geological
structure and history, draws a dividing line between them in northern
California. The Sierra Nevada-Cascade range extends far into Canada, and
is there known as the Coast Range. No adjustment of the nomenclature in
use on the two sides of the international boundary has been made, and in
order to conform with current usage, it is necessary to consider
separately the two portions of the range on opposite sides of the
forty-ninth parallel.
The Sierra Nevada has its southern terminus at Tejon Pass, in southern
California, and extending from there northward to Lassen Peak, in the
northern part of the same State. With the exception of a small area to
the east and north of Lake Tahoe, the entire range is included within
the boundaries of California. This is geographically one of the best
defined of the larger mountain ranges in the United States. Its eastern
border especially is easy to trace, as for the most part it is
determined by a great escarpment, corresponding to the fault scarp which
borders one side of so many of the basin ranges. The Sierra Nevada, in
fact, may be considered as one of the basin ranges of great size and
forming the western wall of the region of interior drainage lying to the
eastward. This abrupt eastward-facing mountain slope is in reality a
great fault scarp, formed mainly by the upheaval of the west side of an
intersecting system of fractures. It is not known, however, how much of
the escarpment is due to the upheaval of the west side of the belt of
fracture, or how much to the sinking of the eastern side. There have no
doubt been many up and down movements along this belt, of which
the present mountain wall is the algebraic sum. The escarpment rises in
general from 5,000 to 6,000 feet above the desert valleys to the
eastward, and reaches a maximum of about 14,000 feet in the vicinity of
Death Valley. It is exceedingly precipitous and rises to an irregular
serrate crest-line, from which the general slope westward to the Great
Valley of California is gentle.
The best idea of the generalized topographic form as well as of the
origin of the Sierra Nevada, which the reader may be asked to hold in
mind, is that the range consists of a block of the earth's crust about
500 miles long and from 70 to 100 miles broad, which has been upraised
along its eastern edge so as to give its surface a westward inclination.
From this vast monolith the profound cañons and multitude of sharp
tapering spires which give to the range its magnificent scenery have
been sculptured. Like most generalized pictures of great geographical
features, however, this outline of the form and structure of the great
mountain range of California has to be modified when studied in detail.
From extensive and most painstaking studies by H. W. Turner, of the
United States Geological Survey, the conclusion is reached that "the
Sierra Nevada may be described as a monogenetic range, composed of
highly compressed schists and slates with large areas of associated
igneous rocks, chiefly granite and diabase, upon which lie uncomfortably
a series of later Cretaceous and Tertiary sediments and volcanic rocks."
Could the profound valleys carved in the long western slope of the
Sierra Nevada be filled so as to restore the conditions as they existed
when the mountain block was first upraised and tilted, we would have an
inclined plane in which the edges of previously folded rocks would be
exposed. In other words, the western slope is a tilted peneplain,
bearing on its surface remnants of older uplands. High up on the range
there are detached areas of well-worn gravel, which were deposited when
the slopes were less inclined than at present, and before the existing
peaks and cañons came into existence. Certain of the valleys carved
during a portion of the earlier stage of erosion were subsequently
filled by lava-floods, which buried gold-bearing gravel beneath thick
layers of basaltic rock. Erosion has since cut away the softer beds
bordering these ancient lava-sheets, and left them in bold relief as
table mountains, underneath which miners have excavated tunnels in order
to reach the stream-deposited gravels of the ancient cañons. In these
instances valleys have been changed to uplands, owing to the resistance
to erosion afforded by the volcanic rocks discharged into them.
The long gentle slope on the west side of the Sierra Nevada has been
dissected by westward-flowing rivers, which have sunk their channels
2,000 or 3,000 feet or more into the rocks. Other streams having much
shorter courses flow down the steep eastern slope of the range and have
also excavated cañons. These two systems of drainage, one leading
westward to the Great Valley of California and the other eastward to the
valleys of the Great Basin, extended their head branches until they came
into rivalry with each other, and cut deep notches in the crest of the
range. During a late stage in its history the higher portions of the
mountains were covered with a great field of perennial snow, from which
glaciers flowed both eastward and westward. These ice-streams, by
deepening and broadening the previously water-cut channels, still
further increased the diversity of the topography and impressed upon it
characteristics such as only glaciers can produce.
The highest and most typical part of the Sierra Nevada is in its
south-central portion, and is known as the High Sierra. This region,
although at present not accurately defined, is well worthy of
recognition. Throughout its entire extent, from the neighbourhood of
Lake Tahoe on the north to Tehichipe Pass at the south, a distance of
about 240 miles, it is diversified by rugged serrate peaks and narrow
stream-cut valleys of great depth. Many of the mountains attain
elevations of from 12,000 to over 13,500 feet. The highest summit is
Mount Whitney, in the southern part of the range and near its eastern
border, which rises 14,522 feet above the sea and has the added
distinction of being the highest mountain in the United States,
exclusive of Alaska. It is a notable fact that this great mountain-peak
should be situated only about 100 miles from Death Valley, the lowest
depression on the continent.
Another of the remarkable features of the Sierra Nevada is the great
depth and the wonderfully precipitous walls of some of the valleys
carved by the westward-flowing rivers. The most famous of these is the
sublime Yosemite Valley, now world-renowned. This cleft as it appears in
solid light-coloured granite, over a mile deep, is believed by Turner,
the last of several geologists to discuss its origin, to be due to
stream erosion. The fact seems well established, however, that glacial
ice has assisted in the great task. The Yosemite is not such an unique
feature as was at one time supposed, but is approached if not equalled
in depth and magnificence by Hetch Hetchy Valley, through which flows
the Tuolumne River, and is duplicated, in part at least, by other
similar stream-cut gulfs.
Among the chief elements in the glorious scenery of the Sierra Nevada is
the multitude of lakes left as a rich inheritance by the departed
glaciers. These occur not only high up amid the bare peaks where their
basins were excavated by the flowing ice, but also in the lower valleys
where the ancient ice-streams built morainal dams.
The High Sierra was swept nearly clean of soil and _débris_ by the
ancient glaciers, and the hard rocks thus exposed were rounded and
burnished by the ice that flowed over them. But little disintegration or
decay of the rocks has taken place since an amelioration of climate
changed the drainage from a solid to a liquid form. On account mainly of
the general absence of soil the forests are less dense than might be
expected from the height of the regions where they occur and its general
climatic conditions. The more lofty peaks reach far above the forests
and are riven and shattered by frost. The crests and cliffs at somewhat
lower altitudes are also bare, but in the cañons and on the meadow-like
valley bottoms smoothed by the glaciers, open park-like groves of pine
and spruce grow in picturesque disorder. On the ledges of the great
precipices, and on many of the secondary summits, gardens of
alpine flowers blossom in late summer, and at times impart a rich warm
glow to the heights that support them. The views of nature, unmarred by
the hand of man, which reward the persistent mountaineer in this silent
wonderland of the upper world, are not only grand beyond all
description, but beautified by a delicacy of decoration where
snow-fields and alpine gardens meet, that is undreamed of by the
dwellers in the denser air of the plains and seaside. Lovers of nature
who are unable to climb the towering summits of the High Sierra and see
for themselves the marvellous beauty there so lavishly displayed can at
least find a glowing pen picture of it in John Muir's fascinating book
The Mountains of California. On the lower western slope of the Sierra
Nevada the forests become continuous and luxuriant, the trees are of
large size, and the lovely flowers carpeting the valleys and hillsides
take on a more familiar appearance than the gorgeous blossoms of the
alpine meadows. It is in this region that the gigantic _Sequoia_ still
lingers as a remnant of a nearly extinct flora.
Statements of heights and depths, of geological structures, and of
topographic forms are perhaps necessary to enable one to form a mental
picture of a snow-crowned mountain range which will bear some faint
resemblance to the mighty original; but when one threads his way through
the resinous forests on the lower slopes of the Sierra Nevada, ascends
some one of the profound water-cut rifts in its side, scales the steep
cliffs, traverses the crystal surfaces of the small glaciers, and
finally stands on a spire-like summit covered only by the dark blue of
the dome above, all thoughts of the arches and walls that support the
mighty cathedral are lost in wrapt wonder and admiration of the
magnificent scene about him. It is this intense feeling for the sublime
and beautiful in nature that the student of geography should strive to
cultivate, as well as to acquire skill in reading the prosaic history
written everywhere on the mountains. This important lesson can seldom be
studied to greater advantage than amid the silent awe-inspiring peaks of
California.
The Cascade Mountains, as previously stated, are a direct continuation,
so far as the relief is concerned, of the Sierra Nevada. The geological
structure of the region in northern California, where the two ranges
approach each other, has been studied by J. S. Diller, of the United
States Geological Survey, who concludes that they present characteristic
differences. In the Cascade Mountains in northern California, Oregon,
and southern Washington the rocks exposed at the surface are mainly, if
not entirely, of volcanic origin, and were poured out in a molten
condition as lava-flows, or as fragmental ejections from volcanoes, and
in part rose through fissures and formed what are termed fissure
eruptions. The rocks thus extruded are mainly composed of dark, heavy
basic material, such as basalt and andesite. These outpourings of molten
rocks were on a grand scale, and a large number of volcanic mountains
were formed which still remain as the dominant peaks of the rugged and
densely forested Cascade Range. Although the evidence now available
seems to show that there is a striking difference between the Sierra
Nevada and the Cascade Mountains, another significant change occurs when
one follows the Cascade Mountains into northern Washington. Where the
Northern Pacific Railroad crosses the range the volcanic rocks are
succeeded northward by granites, schists, serpentine, etc., and
Cretaceous and Tertiary sedimentary beds of much the same character as
those in the Sierra Nevada.
The study of the Sierra Nevada-Cascade region has not progressed far
enough to warrant a decision, but the fact referred to above strongly
suggests that the two ranges, as we now term them, are essentially a
single uplift, a large portion of which, extending from Lassen Peak, in
California, northward across Oregon and into Washington as far as the
Northern Pacific Railroad, is buried beneath a great blanket, so to
speak, of lava-flows. The tract of elevated and rugged country in
northern Washington embraced in the Cascade Mountains, as has been
observed by the writer, passes into Canada without a marked change in
either its geology or geography, and there is no occasion for a
change of name when the international boundary is crossed.
The Cascade Mountains in Oregon and southern Washington, where the
surface rocks are mainly and perhaps wholly of volcanic origin, are
rugged for two principal reasons: First, volcanic energy has built up
great individual peaks; and second, erosion has carved deep valleys and
numerous ravines and gorges. The volcanoes are now extinct, or have long
been dormant, and their cold summits are in several instances crowned
with perennial snow and small glaciers. The forms given to the more
prominent elevations by the eruptions which built them have to a great
extent been defaced by erosion. As they stand to-day they furnish an
instructive series of more or less deeply dissected volcanic mountains.
[Illustration: FIG. 21.--Crater Lake in the summit of Mount Mazama,
Oregon.]
Not only has erosion changed the characteristic slopes of the peaks
built of lava-flows and ejected fragments, but in at least one
remarkable instance the volcanic energy itself greatly altered the
structure it had previously raised. Mount Mazama, situated in southern
Oregon in the summit region of the Cascades, is a truncated volcanic
cone in the top of which there is an immense depression now partially
filled by the waters of Crater Lake (Fig. 21). The main features in the
history of this unique mountain with a lake in its summit, as
interpreted by Messrs. Dutton and Diller, of the United States
Geographical Survey, are as follows: It once stood as a conical peak,
similar to several other mountains of volcanic origin in the same
region, some 15,000 feet in height; it was then an active volcano with a
summit crater filled with lava, but subsequently, for a time at least,
became dormant and was occupied by glacial ice. At a later period an
escape for the lava was furnished by a fissure or other opening which
admitted of a surface discharge at a more or less distant locality, in a
manner similar to the escape of the molten rocks from the great
volcanoes of the Hawaiian Islands within historic times. This drawing
off of the lava from the crater removed the support afforded its walls
from within, and the summit portion of the mountain, embracing about
three-fourths of its height above the adjacent valleys, fell in
and was engulfed. The mountain was thus truncated, and presents the
general appearance of similar cones the upper portions of which are
known to have been blown away by explosions. But in the case of Mount
Mazama, the hypothesis of truncation by explosion seems to be disproved
by the absence of the fragments of the portion removed on the slopes
remaining or on the surrounding region. After the falling in of the
summit of the mountain comparatively mild volcanic explosions followed
which built a cone within the great pit or _caldera_ in the summit of
the truncated mountain, but without filling it. The space left vacant is
now occupied by water, and thus transformed into a lake. The cone built
after the catastrophe referred to now forms Wizard Island, near the
southwest border of Crater Lake.
Some idea of the magnitude of the changes wrought in Mount Mazama by the
events recorded in its geology and topography may be obtained from the
following facts: Crater Lake has a surface elevation of 6,239 feet above
the sea, and is nearly 2,000 feet deep in its deepest part; the
precipices surrounding it are from 520 to 1,987 feet high. The whole
depth of the depression is therefore 4,000 feet. This _caldera_, as such
basins of volcanic origin are termed, is nearly circular, with an east
and west diameter measuring 6 miles, and a north and south diameter of 5
miles. The volume of the pit is nearly 12 cubic miles.
Not only is Mount Mazama with its wonderful lake one of the most unique
natural features of North America, but it has its full share of the
artistic details of lake and mountain scenery which appeal so forcibly
to the finer instincts within us. The outer slopes of the mountain are
clothed with the all-embracing coniferous forests which cover the
Cascades as with a mantle throughout their entire extent, while the
precipitous inner slopes are for the most part bare precipices of
angular and extremely rugged rock. The lake itself is of the most
marvellous blue, in which the encircling cliffs, the crater-island, and
the sky above are reflected.
[Illustration: FIG. 22.--Mount Rainier, Washington.]
Other peaks along the crest-line of the Cascades to be numbered by the
score, although with less romantic histories than Mount Mazama,
have instructive answers to give when properly questioned. Among the
remarkably picturesque summits rising above the dark coniferous forests
of western Oregon are the following, with their respective heights above
the sea expressed in feet: Mount Pitt, 9,760; Mount Mazama, 8,228; Mount
Union, 7,881; Mount Scott, 7,123; Three Sisters, Mount Jefferson,
10,200; and Mount Hood, 11,225. Of these peaks, the best known, on
account of its proximity to the city of Portland, and at the same time
one of the most picturesque and beautiful, is Mount Hood, situated about
25 miles south of the Columbia River. The concave slopes so
characteristic of volcanic cones are no longer conspicuous on the sides
of this once symmetrical mountain, and only remnants of its crater
remain. The part it played as a safety-valve for the pent-up energy
beneath was long since finished, although heated vapours still escape
from an opening near the summit. Similar manifestations of heat have
also been observed about several other ancient craters in the Cascades,
but these occurrences are not considered as indicating that actual
connections still exist with reservoirs or bodies of molten rocks below
the surface: they are evidently due to the residual heat of the once
molten rock in the conduits of the now extinct or dormant volcanoes.
The lava-flows and volcanic mountains typically displayed in the
Cascades throughout the breadth of Oregon continue northward and form at
least the surface portion of the same range in Washington as far as the
Northern Pacific Railroad, or about 100 miles north of the Columbia. The
more important volcanic mountains in western Washington are, in their
order from south to north; as follows, the height of each being given in
feet: Mount Adams, 9,570; Mount St. Helens, 9,750; Mount Rainier,
14,525; Glacier Peak, 10,436; and Mount Baker, 10,877. Only two of these
ancient volcanoes, namely, Mount Adams and Glacier Peak, are situated on
the crest-line of the Cascade Mountains; the others are to the westward
and more or less completely detached from the main range.
The Cascade Mountains are in general parallel with the shore of the
Pacific, and rise as a prominent barrier athwart the path of the
prevailing westerly winds. Precipitation on their seaward slopes is
copious, but their landward sides overlooking the arid plains of central
Washington are far less humid. The westward, or rainy slope, is clothed
with a magnificent forest of giant trees, while the eastward, or sunny
side, is largely without forests, but abounds in natural meadows and
pastures. Large portions of the mountains are still almost entirely
unknown, and retain their primitive wildness, except that forest fires,
particularly near the international boundary, have in places made
desolate the once beautiful valleys and precipitous slopes. Elk, deer,
bear, the mountain-goat, and mountain-sheep still roam the forests. The
large streams abound in salmon, and each cool, clear brook and rushing
creek is a favourite haunt of the trout. No more delightful
camping-ground for lovers of nature and searchers for recreation can be
found than the grassy, park-like valleys on the sunny side of these
magnificent mountains.
Many of the details in the scenery of the Cascades are due to the work
of ancient glaciers. Numerous lakes, held in rock-basins in the higher
portions of the mountains, and many still larger sheets of water
retained by morainal dams in the lower valleys, give a superlative charm
to many a wild and rugged landscape. The largest and most interesting
lake in the entire Cascade region is Lake Chelan, situated in a deep
valley on the eastern side of the mountains in north-central Washington.
This beautiful sheet of water, a mile or two wide, extending like a
placid river for some 70 miles into the mountains, resembles in many of
its features the far-famed lakes of northern Italy. The mountains
inclosing this hidden gem of the Cascades rise abruptly from the water's
edge to great heights, and with one exception are unbroken by deep
side-valleys. For fully 50 miles the blue plain of water is overshadowed
on each side by crags and precipices from 5,000 to 6,000 or more feet in
height. The lower slopes are dark with forests of pine and fir, and the
bare serrate spires above are white with snow long after the
spring flowers have faded in the lower vales. The water of the lake is
clear and sparkling, and has the deep-blue colour of the open ocean. The
sounding-line has shown a depth of 1,400 feet, and the bottom is about
300 feet below sea-level. This wonderful lake, clasped in the embrace of
the eastward extended arms of the Cascades, is but 2 or 3 miles from the
Columbia River, into which it discharges its surplus waters through
Chelan River, and may be easily reached from Wenachee, on the Great
Northern Railroad, by steamers on the Columbia. Although at present
scarcely known to the world of tourists, Lake Chelan is destined to take
as an important place in the lives of those who seek rest and recreation
as does Lake George in northern New York at the present day.
Before attempting to trace the Pacific mountains northward through
Canada and Alaska, let us glance at the leading geographical features to
the west of the Sierra Nevada-Cascade uplift.
THE GREAT VALLEY OF CALIFORNIA AND THE PUGET SOUND BASIN
To the west of the Sierra Nevada-Cascade Mountains, and bordered on the
west by another and very nearly parallel series of elevations, known in
a general way as the Coast Mountains, there is a succession of long,
relatively narrow basins, situated end to end, and constituting what may
be termed a valley-chain. This series of basins extends from southern
California northward far into Canada, and includes, in their order from
south to north, the great Valley of California, the Willamette and
Cowlitz Valleys in Oregon and Washington, and the Puget Sound basin,
together with its great but indefinitely defined northward extension.
The Great Valley of California has a length of about 500 miles and an
average width of approximately 40 miles, and is greater in area than
either Belgium, Denmark, or Switzerland. It is divided in reference to
drainage into two portions, the San Joaquin Valley at the south and the
Sacramento Valley at the north, named respectively after the
rivers that drain them. These two streams unite and discharge into San
Francisco Bay, the outlet of which is through the Golden Gate to the
Pacific. This central basin of California has a generally flat bottom
composed of a great depth of unconsolidated gravel, sand, and clay,
which are believed to owe their deposition mainly to the streams flowing
from the bordering mountains, although in part they may have been
deposited when the land was more depressed than now and the basin was a
great sound, connected with the ocean by a single narrow opening. The
rock-waste swept into the valley served not only to add to the
accumulations forming its floor, but to give the bottom some
irregularities. A portion of its southern end, shut off by alluvial
deposits brought down from the Sierra Nevada, is occupied by the shallow
alkaline waters of Tulare Lake. When the great valley was first visited
by white men it was without trees, except along the immediate borders of
some of the streams, and for the most part was a luxuriant meadow of
wild grasses and flowers. On the uplands oak-trees grew in scattered
park-like groves with gorgeously flower-decked hills and vales between.
This favoured land, clothed in its natural beauties, came as near being
an Eden as perhaps any portion of the continent. The changes that have
followed the settlement and cultivation of this great mountain-inclosed
basin are simply marvellous. Cities and villages have been built,
orchards and vineyards planted which yield most bountiful harvests, and
the once grass-covered plains are now seemingly boundless wheat-fields.
The unkept natural garden of half a century ago has become a granary not
only for the people of America, but for those of Asia as well.
To the north of the Klamath Mountains, which shut in the central Valley
of California at the north, lies the beautiful Willamette Valley, about
150 miles long, drained by the northward-flowing river of the same name,
which joins the Columbia where the thriving city of Portland now stands.
The depression between the mountains of which the Valley of the
Willamette forms a part, extends north of the Columbia, and is there
drained by the southward-flowing Cowlitz River. The relation of
these two valleys is much the same, although on a smaller scale, as that
existing between the San Joaquin and Sacramento Valleys, except that the
Columbia, after passing through the Cascade Mountains, receives the
Willamette and Cowlitz rivers as tributaries, one from each side of its
course. This Willamette-Cowlitz depression is surrounded by densely
forested hills and the snow-capped summits of ancient volcanoes. The
soil was originally highly fertile, and although now somewhat
impoverished, still furnishes a substantial basis for agriculture, and
renders the region one of the most productive as well as most beautiful
in the United States.
To the geographer the Willamette-Cowlitz Valley seems scarcely distinct
from the great depression farther north in the same valley-chain, which
now holds the waters of Puget Sound, except that there is a low
water-parting between. This divide, as previously suggested, is thought
to be due largely to stream and glacial deposits, which have been laid
down in the previously nearly level-floored intermontane trough.
The Puget Sound basin has a length from south to north of about 150
miles, and extends from the Olympic Mountains on the west to the Cascade
Mountains on the east, a distance of some 60 miles. The sound terminates
at the north at the Strait of Fuca (at Port Townsend, in Fig. 23), but
the depression in which it lies continues northward, with similar
geographical and geological characteristics. In a general way the same
depression may be said to extend northward to southeastern Alaska, but
is there deeply water-filled, and its western border is discontinuous
and broken into many islands.
There are several features in the Puget Sound basin which especially
impress the traveller: Next to the magnificence of the lofty volcanic
cones that stand like Titan watch-towers along the western slope of the
Cascades and the dense forest of gigantic firs and cedars, the most
conspicuous feature of the region is the extreme irregularity of the
sound itself. Even such general maps of Puget Sound as are
usually available indicate that it is exceptional and different from all
other water bodies on the continent, not including the extension of the
same series of basins northward. Not only is Puget Sound extremely
irregular, and inconsistent with any theory that would ascribe its
origin to the subsistence and drowning of stream-eroded valleys, but its
waters are deep and the channels narrow. The uplands between the
waterways are low plateaus composed of clay, gravel, and glacial
moraines. The explanation of these unique conditions is that glacial ice
formerly occupied the basin and deposited moraines and gravel-plains and
clay-plains about its margins; when the branching and irregular sheet of
stagnant ice melted its place was taken by the waters of the sea. This
simplified outline of the later history of Puget Sound has many
modifications, the most important being that there were at least two
periods of ice occupation, with an intervening stage of mild climate
between, during which the previously formed glacial deposits were forest
covered and thick beds of peat formed.
[Illustration: FIG. 23.--Puget Sound.]
The ice which occupied Puget Sound was the extreme southern portion of a
great but irregular Piedmont glacier which fringed the rough and ragged
coast of the continent all the way to southern Alaska. A remnant of this
former ice body still exists near Mount St. Elias, and constitutes the
very instructive Malaspina glacier.
THE MOUNTAINS BORDERING THE PACIFIC
In a preceding chapter the rugged topography of the western margin of
the continent has been briefly described, and a general explanation
given of the contrasts which it presents to the coastal plains and
plateaus on the Atlantic border.
The long, narrow peninsula known as Lower California, as yet unstudied
in the light of modern geography, is known to be mountainous throughout.
Although nearly surrounded by the waters of the ocean, the climate of
the peninsula is hot and arid and its surface desert-like. The Gulf of
California, which separates such a large portion of the Pacific border
of Mexico from the main body of the republic, has the characteristics of
a drowned intermontane or orogenic valley. But whether the great
depression was ever dry land or not is unknown. The waters of the gulf
are shallow, however, and a moderate upward movement of the earth's
crust in that region would transform it into a great valley similar in
its general features to the central basin of the State of California.
What are frequently designated collectively as the Coast Mountains begin
at the south and adjacent to the shore of the Pacific, in the vicinity
of Santa Barbara, Cal., and extend northward along the immediate
seaboard far into British Columbia. A continuation or branch of this
series of elevations follows the south coast of Alaska, and is prolonged
so as to form the Aleutian Islands. The length of the mountain system or
succession of ranges referred to is between 3,500 and 4,000 miles. The
detailed study of this long, narrow, and in many parts excessively
rugged region is as yet in its infancy, and only a brief account of its
salient features can be attempted at present.
In southern California the structure of the mountains and the deep
stream-deposited gravel, etc., in the intervening valleys, as well as
the aridity of the climate and character of the vegetation, correspond
closely with the similar conditions in the Great Basin. In fact, the
Great Basin region, as the term has been used on a previous page, there
meets the Pacific, and the islands rising from the adjacent
portion of the ocean seem to be the summits of mountains of the Basin
Range type. Owing to the dryness of the climate in southern California
and adjacent portions of Mexico, the deeply alluvial-filled valleys are
treeless, and agriculture is only possible with the aid of irrigation.
Where water can be had, however, there are wonderfully productive
orchards, vineyards, and gardens, in which the fruits and flowers of
both the temperate and torrid zones flourish side by side with
marvellous luxuriance. The palm there casts its shadow on fragrant
bowers of the most superb roses. The grass-clothed mountain slopes are
either bare of trees or but scantily forested, while the upland valleys
produce a dense jungle of native trees and shrubs.
To the north of the irregular and diversified portion of southern
California, where the Great Basin region extends southwestward to the
Pacific, rises the southern Coast Range of California. The indefinite
beginning of this range is in the neighbourhood of Point Conception, to
the north of Santa Barbara, and its northern terminus is at the Golden
Gate. The same belt of mountains extends northward, however, and forms
the northern Coast Range, which extends to the Klamath Mountains in
northern California. The coast ranges of California as a whole are about
500 miles long and from 30 to 40 miles broad, and comprise several
seemingly distinct uplifts, some of which have culminating peaks from
4,000 to about 7,000 feet high. In general this elevated region is
conspicuously sculptured, and in part at least has the characteristics
of an eroded plateau. The suggestion has been offered that the northern
portion of the Coast Range is a dissected peneplain.
The Coast Ranges, although generally bare of trees to the south of the
Golden Gate, become more and more densely forested when followed
northward. It is in this northern division that the great forests of
redwood occur, now so largely used for lumber. Reference is here made
not to the "big trees," which grow in certain restricted areas on the
west slope of the Sierra Nevada, but to the far more extensive forests
of a related species.
Considering mountain forms simply, it is difficult if not impossible to
determine where the Coast Mountains of California terminate at the
north, but, as has been shown especially by J. S. Diller, there are
reasons based on geological structure for separating them from the
irregular group of ranges and peaks in northern California and southern
Oregon recently named the Klamath Mountains. The coast system is
continued north of the Klamath Mountains by the Coast Mountains of
Oregon, which extend to the Columbia River, and consist of irregular
ridges or series of ridges, with bold lateral spurs, especially on the
ocean side. It varies conspicuously in height from place to place, yet
nowhere attains a great altitude. The elevations of the bolder summits,
although not accurately measured, seldom exceed 3,000 feet.
The Coast Mountains of Oregon are considered as terminating at the
northern boundary of the State, there defined by the Columbia River, but
no reason is apparent, however, for not including in the same group the
elevated land lying in southwestern Washington and adjacent to the
Pacific coast. Between the Columbia and Chehalis River in Washington
there is a rugged region which attains an elevation of over 4,000 feet,
and is separated from the Olympic Mountains to the northward by Chehalis
Valley. Although the geology of this group of ridges and peaks is
entirely unknown, its position and general appearance, when seen from a
distance, suggest that it might properly be considered as a direct
extension of the Coast Mountains of Oregon.
Following the general belt of the Coast Ranges still farther northward,
we come to the splendid group of forest-clothed mountains, with usually
snow-covered summits, situated to the west of Puget Sound, and known as
the Olympic Mountains. This magnificent range is in full view from
Victoria, Seattle, and Tacoma, and would be far-famed for its grandeur
were it not for its near rival, the still more lofty Cascade Range.
There are several fine, sharp peaks in the Olympics that have never been
scaled, the highest of which, Mount Olympus, rises 8,150 feet
above the sea. Owing to the excessive humidity and other favourable
climatic conditions, these mountains are clothed with magnificent
forests up to an elevation of about 7,000 feet. On account of the
ruggedness of the country, the extreme density of the tangled
undergrowth, and the obstructions formed by the fallen moss- and
lichen-covered trees, this region is extremely difficult to traverse,
and to-day is the least known of the continental portion of the United
States. On the north the excessively rugged Olympic peninsula is
bordered by a deep, broad fiord known as the Strait of Fuca. To the
north of this formerly ice-filled channel lies Vancouver Island, the
central and northern portion of which is mountainous. The highest summit
on the island rises about 7,500 feet above the sea, and a considerable
area in its central part has an elevation of over 2,000 feet.
The Olympics, together with the mountains of Vancouver and Queen
Charlotte Islands, and the northern extension of the same belt, embraced
in part within the mainland of British Columbia and southeastern Alaska,
have been termed the "Vancouver Mountains" by Canadian geographers. The
northern boundary of this mountain system, justly named in honour of the
celebrated English explorer who mapped large portions of the northwest
coast about a century since, remains indefinite, and cannot be
determined until geologists have made more thorough explorations of the
land it occupies. The leading geographical features of this region, as
remarked in a preceding chapter, are due to the deep dissection, by
streams and glaciers, of an elevated table-land. When the ice-streams
melted, the sea was permitted to enter the valleys, so as to form
numerous deep, narrow, steep-walled fiords (Fig. 11). The coast is, in
fact, the most ragged of any portion of the border of the continent. All
but the higher summits are clothed with a dense mantle of vegetation,
the upper limit of which decreases in elevation when followed northward,
from about 7,000 feet in the Olympics to approximately 2,500 feet in
southern Alaska. Perennial snow exists in the higher valleys and
amphitheatres of the Olympics, but the presence of true glaciers
in that group of peaks has not been demonstrated. When followed
northward the snow-line becomes lower and lower, and well-defined alpine
glaciers are known to exist in many of the valleys, more especially on
the mainland of British Columbia and southeastern Alaska. There streams
of ice descend lower and lower with increase in latitude, and to the
north of Stickeen River, in a number of instances, enter the fiords
which connect with the ocean and become tide-water glaciers.
To the west of Lynn Canal, and extending to beyond Copper River, is the
most rugged portion of North America, and contains also some of the
highest mountain-peaks on the continent thus far measured.
The region of high mountains in Alaska and the adjacent portion of
Canada begins on the east in the group of magnificent peaks which
cluster about Mount Fairweather as a centre and extend westward, with a
breadth of some 80 miles, to beyond Mount St. Elias. Farther westward,
beyond Copper River, other great mountains are known to exist. One of
these, Mount McKinley, has an elevation of 20,400 feet, and so far as
now known is the highest peak in North America.
The highest summit to the east of Copper River is Mount Logan, 19,500
feet. This superb ice-sheathed peak is situated in Canada about 40 miles
from the coast and 12 miles east of the one hundred and forty-first
meridian. Second in rank is Mount St. Elias, 18,070 feet, situated close
to the one hundred and forty-first meridian, and within the territory
belonging to the United States. These two summits are the highest in a
land of lofty snow-covered mountains, and for this reason have claimed a
large share of attention. There are many neighbouring peaks, however,
that are wonderfully magnificent, but only a few of them have been
measured and many of them are still unnamed. Only one of the high
mountains of Alaska, namely, Mount St. Elias, has been climbed. This
splendid feat of mountaineering was accomplished by Prince Luigi, of
Savoy, in 1899.
In southern Alaska the snow-line is only about 2,500 feet above
tide, and a large number of magnificent glaciers descend to sea-level,
and many of them actually enter the ocean. All of the valleys and basins
among the higher summits are occupied by snow-fields and glaciers. The
general covering of ice and snow as well as the ruggedness of the land
makes this the most difficult of all the mountainous portions of North
America to traverse.
In the St. Elias region the mountains have been produced by upheaval,
and are not volcanic in their origin. The frequently repeated statement
that Mount St. Elias is a volcano is incorrect. Although igneous rocks
occur near its summit, they are of the nature of dikes or intrusions,
probably of ancient date, and not lava-flows. The principal volcanic
mountains of Alaska are farther west in the region of the Alaskan
peninsula and the Aleutian Islands. This western extension of the
continent is excessively rugged, but the mountains rise directly from
the ocean and in part form a chain of precipitous islands with irregular
topographic forms.
There are mountain ranges also in the central and northern portions of
Alaska and the adjacent part of Canada, but this region awaits
exploration, and but little accurate information concerning its
topography is on record.
_The Mountains of Western Canada._--Reference has already been made to
the differences in the nomenclature applied to the portions of the
Pacific mountains on opposite sides of the United States-Canadian
boundary, and at present this lack of harmony cannot be adjusted. As is
well known, the great Pacific cordillera crosses the boundary nearly at
right angles, and there is no abrupt change in the topography of the
land. From the western border of the Great plateaus to the Pacific,
between the forty-fifth and fifty-sixth parallels, as stated by the
Geological Survey of Canada, the cordillera has an average breadth of
about 400 miles, and is composed of four great mountain chains, named in
their order from east to west, the Rocky, Gold, Coast, and Vancouver
Mountains. These four great chains are nearly parallel and have
irregular northwest and southeast trends.
The Canadian Rockies rise abruptly from Great plateaus in which the
rocks are nearly horizontal, and have a complex structure, due to the
folding and other disturbances that have affected the strata. Deep
dissection by stream erosion has occurred, as is the case generally
throughout the Pacific cordillera, and the peaks and ridges remaining
are remarkable for their grandeur. Although less elevated than the
higher portions of the same great belt in the United States, many of the
summits are from 8,000 to 10,000, and, as reported, in a few instances
reach 13,000 feet in height, while the passes range is elevated from
about 4,000 to 7,000 feet. The western border of the Rocky Mountain
range is well defined for a distance of some 700 miles to the northward
of the international boundary by a remarkably straight, wide valley,
which is occupied by the head waters of several large rivers, namely,
the Kootenay, Columbia, Fraser, Parsnip, and Findley. To the west of the
great valley just referred to rises the Gold system, composed
principally of the Selkirk, Purcell, Columbia, and Caribou Ranges. It is
in this rugged region that some of the most remarkable of the splendid
scenery of western Canada occurs.
To the west of the Gold system is a broad region of valleys and lesser
mountains, known as the interior plateau of British Columbia, which is a
northward extension of the Great Basin region of the United States. The
breadth of this belt of comparatively low country is about 100 miles.
Like the similar region in Washington and Oregon, it is without forests,
but favourable as a grazing country. In part it is occupied by extensive
lava-flows, similar to the Columbia River lava of the northwestern part
of the United States.
The Coast Mountains of Canada, although stated by geologists to be
distinct from the Cascade Mountains, are in part at least, as determined
by the present writer, a direct northward extension of that range. The
average elevation of the higher peaks in the Canadian Coast Range, as it
is termed, is between 6,000 and 7,000 feet, while the culminating points
reach an elevation of about 9,000 feet. How far northward the
nomenclature applied to the Pacific mountains in southwestern Canada
will be found applicable can not be stated, as the region to the north
of the fifty-sixth parallel is almost wholly unknown.
THE ANTILLEAN MOUNTAINS
As has been clearly pointed out by R. T. Hill, the Pacific cordillera
ends at the south in south-central Mexico, while the Andean cordillera
at its northern end terminates in the rugged mountains of Venezuela to
the south of the Caribbean Sea. These two great cordilleras do not
overlap, but there is a difference of about 10 degrees of latitude
between them, and if extended they would pass each other at a distance
of nearly 1,000 miles. In the space thus indicated, measuring some
600,000 square miles, is included the southern portion of Mexico,
Central America, and the West Indies. The rocks in these countries
present a great series of folds which trend in an easterly and westerly
direction, and thus present a conspicuous exception to the major
structural features of both North and South America. To this newly
recognised division of the larger geological and geographical
characteristics of the New World the name _Antillean mountains_ has been
given.
The folds or corrugations in the rocks of the Central American and
Caribbean region extend in an east and west direction along the seaward
margin of Venezuela and Colombia from the Orinoco westward to the
Isthmus of Panama, and thence continue westward through Costa Rica, the
eastern portions of Nicaragua, Guatemala, and Honduras, and reach
southern Oaxaca in Mexico. The same system of plications is revealed
also on the larger West India islands. The rocks of this great region
include granite and allied metamorphosed terranes, old lavas, and
sedimentary beds.
One of the most conspicuous features of this region with a structure and
relief commonly found in mountains is that to a great extent it is
depressed beneath the sea, and only the higher summits are in view. Some
of the larger inequalities of the rock surface have been
discovered by means of the sounding-line. By referring to Fig. 3, it
will be seen that two submarine ridges extend in an east and west
direction beneath the Caribbean Sea, from the West Indies to the Central
American coast, and are separated by Bartlett Deep. These ridges
correspond in trend with the longer axes of the folds in the Antillean
mountains, and suggest a common origin for the leading geographical
features of the land and of the still more remarkable topography of the
sea-floor.
In addition to mountains produced by corrugation and upheaval, there are
also in the middle American region numerous volcanic mountains. Of these
there are two well-defined belts, each trending in general north and
south, or directly across the longer axes of the folds of the Antillean
mountains. One of these belts of volcanic cones and craters is situated
on the Pacific coast of Central America and Mexico, and includes some 25
active volcanoes, and the other is defined by the numerous volcanic
islands of the Lesser Antilles. The association of these belts of
fracture through which molten rock has been extruded and where
earthquakes are of common occurrence, with the junction of the east and
west belt of plication to which the Antillean mountains are due, with
the north and south belts of mountains forming the Pacific and Andean
cordilleras, is significant in connection with the study of the origin
of the larger features of the relief of the solid earth.
* * * * *
Varied as is the relief of North America when studied in detail, an
outline sketch of its major features may be readily retained in mind. On
the east side of the main continental area are the Atlantic mountains,
extending from near the Gulf coast northward to beyond Hudson Strait; in
the central part is the broad continental basin, a vast region of low
relief reaching from the Gulf of Mexico to the Arctic Ocean; west of the
continental basin are the Pacific mountains, the greatest of all the
elevations on the continent, which begin abruptly in south-central
Mexico and extend northward, expanding to a width of about 1,000
miles in the United States and reach the Arctic Ocean and Bering Sea.
The movements in the earth's crust, which blocked out these major
physiographic features, were produced by forces acting in east and west
directions, and gave origin to folds and faults with their longer axes
trending north and south. To the south of the main body of the
continent, in middle America, are situated the Antillean mountains, also
a cordillera comparable with the Atlantic and Pacific cordilleras, in
which the longer axes of the folds and faults trend east and west, and
are due to forces acting in north and south directions. The Antillean
mountains in a general way connect or intervene between the Pacific and
the Andean cordilleras. Where the Antillean mountains cross the axes of
the Pacific and Andean cordilleras are situated the volcanoes of
southern Mexico and Central America, and those of the Lesser Antilles.
Geographers will recognise that this outline is drawn boldly, but
although it will no doubt have to be modified as detailed studies
progress, it should serve to emphasize the leading geographic divisions
of the North American continent when viewed as a whole.
LITERATURE
The following list of publications relating to the physiography of North
America is here presented largely because the books mentioned contain
bibliographies or references which indicate sources of more special
information:
_American Geographical Society, Bulletin._ Published annually.
_Canadian Geological Survey_, Ottawa, Canada. Index to reports
from 1863 to 1884, published in 1900.
DARTON, N. H. _Catalogue and Index of Contributions to North
American Geology, 1732 to 1891._ United States Geological
Survey, Bulletin No. 127, Washington, 1896.
DAVIS, W. M. _Physical Geography._ Ginn & Co., Boston, 1898.
Contains a valuable bibliography.
DRYER, C. R. _Lessons in Physical Geography._ American Book
Company, New York, 1901. Contains a valuable bibliography.
_Geological Society of America, Bulletin._ Published annually
since 1890 at Rochester, N. Y. Index to vols. i-x, published in
1900.
_International Geography._ Edited by H. R. Mill. D. Appleton and
Company, New York, 1900. Contains several chapters on North
America by various authors.
_Journal of Geology._ Edited by T. C. Chamberlin and published at
the University of Chicago, Chicago, Ill.
MERRILL, G. P. _Rocks, Rock-Weathering, and Soils._ The Macmillan
Company, New York, 1897.
_National Geographic Magazine._ Washington, D. C.
_National Geographic Monographs._ American Book Company, New York,
1895. One volume published.
POWELL, J. W. _Exploration of the Colorado River of the West._
Published by the Smithsonian Institution, Washington, 1875.
POWELL, J. W. _Cañons of the Colorado._ Flood & Vincent,
Meadeville, Pa., 1895.
RUSSELL, I. C. _Lakes of North America_, Ginn & Co., Boston, 1895;
_Glaciers of North America_, Ginn & Co., Boston, 1897;
_Volcanoes of North America_, The Macmillan Company, New York,
1897; _Rivers of North America_, Putnam's Sons, New York, 1898;
_The Names of the Larger Geographical Features of North
America_, in _Bulletin of the Geographical Society of
Philadelphia_, vol. ii, 1899, pp. 55-68.
SHALER, N. S. _Nature and Man in America._ Scribner's Sons, New
York, 1891.
_Stanford's Compendium of Geography and Travel._ North America:
Canada and Newfoundland, by S. E. Dawson; United States, by H.
Gannett; Central America and West Indies, by A. H. Keane.
Published by Edward Stanford, London.
TARR, R. S. _Elementary Physical Geography._ Macmillan & Co.,
1895.
_United States Geological Survey._ Bibliography and Index,
contained in Bulletins No. 100, 127, 177, 188, and 189, issued
by the Survey. The reader is referred especially to the
_Geological Atlas_ and the _Topographic Atlas_, published by the
Survey.
WARMAN, P. C. _Bibliography and Index to the Publications of the
United States Geological Survey._ United States Geological
Survey, Bulletin No. 100, Washington, 1893. (Relates to
publications of the United States Geological Survey issued
previous to 1892; continued in Bulletin No. 177 by the same
author.)
WARMAN, P. C. _Catalogue and Index of the Publications of the
United States Geological Survey, 1880 to 1901._ United States
Geological Survey, Bulletin No. 177, Washington, 1901.
WEEKS, F. B. _Bibliography of North American Geology,
Paleontology, Petrology, and Mineralogy for the Years 1892-1900,
inclusive._ United States Geological Survey, Bulletins No. 188
and 189, Washington, 1902.
WHITNEY, J. D. _The United States._ 2 vols. Little, Brown & Co.,
Boston, 1889 and 1894.
CHAPTER III
CLIMATE
_The Elements of Climate_
North America, embracing as it does essentially a quadrant of the
earth's surface, presents a variety of climatic conditions ranging from
those characteristic of the equatorial belt to those normal to polar
regions, as well as every gradation due to variations in elevation from
sea-level and even below that horizon in Death Valley, California, to
the summits of high plateaus and lofty mountains.
[Illustration: PLATE II.--Mean Annual Rainfall & Temperature.]
The principal elements of the weather which go to make up the conditions
of the atmosphere embraced in the broader term _climate_ are
temperature, precipitation, and the winds. On the accompanying map,
Plate II, the mean annual temperature of the continent is represented by
_isotherms_, or lines drawn through localities having the same average
temperature for the year. On the same map is also shown in blue the
average depth of precipitation, including both rains and melted snow. On
Fig. 24 lines are drawn through points having the same average
barometrical pressure (_isobars_) for the months of January and July,
together with arrows indicating the general direction of the surface
winds during each of these months, which may be considered as
representative of the summer and winter seasons. The data shown on these
maps have been compiled mainly from the reports of the weather bureaus
of Canada, the United States, and Mexico, and indicate, at least in a
general way, a summary of what is known concerning the main
meteorological elements which determine the climatic conditions in North
America. An examination of these maps will suggest certain general
conclusions in reference to the leading characteristics of the climate
in various portions of the continent and the changes they undergo
from season to season.
[Illustration: FIG. 24.--Average barometric pressure and direction of
wind for January and July.]
_Distribution of Heat and Light._--The distribution over the earth's
surface of the heat and light received from the sun is not only of
fundamental importance as respects climate, but furnishes a part of the
essential conditions on which depend the presence and distribution of
living organisms. The heat and light, or more accurately, the radiant
energy of the sun, the full significance of which is probably not
thoroughly understood, we term, for convenience, _insolation_. The
intensity and seasonal distribution of insolation are prime factors on
which many important results hinge.
Owing to the inclination of the axis about which the earth rotates (23°
27') to the plane in which the earth travels about the sun, or the plane
of the ecliptic, the northern end of the axis is turned towards the sun
in summer and away from it in winter--that is, the axis of rotation of
the earth at all times is parallel to the same imaginary straight line.
As a result, the sun appears to migrate northward in the heavens during
the spring-time of each year, being vertical over the equator on March
21st, and to an observer in north latitude 23° 27' rises higher and
higher each moon, until on June 21st it is vertically overhead; and then
returns southward. The latitude in which the sun is in the zenith at the
time of its greatest northward migration determines the position of an
imaginary line on the earth's surface, named the Tropic of Cancer. This
line, as shown on the accompanying maps, crosses the Bahama Islands,
passes about 40 miles to the northward of Havana, divides Mexico into
two approximately equal parts, and cuts the peninsula of Lower
California near its southern end. The portion of the continent to the
south of the Tropic of Cancer lies within the torrid zone.
When the sun is vertical over the equator, as it is about March 21st and
September 23d each year, its rays, not allowing for refraction, are
tangent to the earth's surface at the poles, and the hours of light and
darkness are equal the world over. During the winter season the sun
appears to migrate southward of the equator until December 21st,
when it is vertical at noon at all points situated in south latitude 23°
27', which is termed the Tropic of Capricorn. Its rays are then tangent
to the earth's surface in the northern hemisphere in latitude 66° 33',
which defines the position of the arctic circle. This imaginary line on
the earth's surface, as is indicated on the accompanying maps, crosses
Canada to the north of Hudson Bay, and passes through Alaska near where
the Porcupine River joins the Yukon. To the north of the arctic circle
lies the frigid zone. Between the torrid and frigid zones is situated
the temperate zone, within which is included about seven-eighths of
North America, exclusive of Greenland. The relation of the continent to
the three great zones of climate into which the northern hemisphere is
divided is thus most fortunate so far as man's activities are concerned.
The climatic zones just referred to, while based on precise astronomical
data and representing important facts, are not separated one from
another by tangible lines, and might easily pass undiscovered by one who
studied only the surface characteristics of the earth. Each summer a
wave of heat and light sweeps northward over the continent and reaches
beyond the pole; and each winter a counteracting wave of cold and
darkness moves southward, the influence of which is marked even well
within the torrid zone. A comparison of the isothermal lines drawn on
the map forming Plate II with the parallels of latitude
shows at a glance that there is only a general relationship between the
two. In order to understand this discrepancy between what might be
expected from astronomical considerations in reference to the
distribution of solar energy and the actual conditions as learned by
observation, it is necessary to take a more critical view of the manner
in which insolation is received by the continent, and also to consider
secondary conditions which exert far-reaching influences on its
distribution.
The amount of heat, or to avoid objections, the distribution of
insolation over North America, depends on three primary conditions:
First, the angle at which the sun's rays strike the earth, the range
being from zero to 90°; second, the length of time a particular
locality is exposed to sunlight; and third, variations in the distance
of the earth from the sun. Each of these conditions varies from day to
day for every locality throughout the continent. The sun is highest in
the heavens in the torrid zone, being twice vertically overhead each
year at every locality, and the hours of light and darkness each day are
approximately equal throughout the year. North of the torrid zone,
however, the rays of the sun become more and more oblique to the earth's
surface, and hence insolation becomes weaker and weaker for a given
period of sunshine as one travels from south to north. But the hours of
sunlight each day undergo marked variations, lengthening from December
21st to June 21st, and shortening as the sun makes its southward
migration. At the north pole, as all know, there are six months of light
and six months of darkness each year. The amount of insolation reaching
the northern portion of the continent each day increases with the
lengthening of the hours of light, and during midsummer is greater for a
given area in a single day (twenty-four hours) than the amount received
by a similar area in the torrid zone. The almost magical springing into
life and bloom of the vegetation over the northern portion of the
continent with the lengthening of the hours of sunshine each summer is
thus explained. In the portion of the continent within the temperate
zone, more especially within the continental basin, the large number of
hours of sunshine during a summer's day is frequently accompanied by a
temperature as great as is usually experienced in the torrid zone. It is
the high summer temperature of this region, together with the lengthened
duration of sunshine in the growing season, that makes the Mississippi
basin and the adjacent region on the east and north so favourable for
agriculture when the requisite amount of moisture is present.
The distribution of heat over the earth's surface depends not only on
the direct influence of insolation, but on its transfer from one
locality to another through the agency of the winds and ocean currents.
The movements of the waters of the ocean, it will be remembered, are
largely under the control of the winds, so that the essential
factor in the transfer of heat from place to place is atmospheric
circulation. The primary causes of movements in the air, as is a matter
of current knowledge, are the differences that arise in temperature at
various localities. In regions where the air becomes more highly heated
than over adjacent areas it expands, and in consequence becomes lighter,
volume for volume, than the air over neighbouring areas, and is forced
upward and overflows aloft. The overflow or dispersion of the warmer and
lighter air above gives origin to a reduction in barometric pressure,
the column of mercury in a barometer being counterbalanced by the
pressure of the air above it. Briefly stated, the air near the earth's
surface flows towards regions of low, and away from regions of high
barometric pressure, and winds are established. The directions taken by
the winds are influenced or controlled in various ways.
_The Planetary Winds._--The great movements in the atmosphere originate
from differences in temperature between the warm equatorial and cold
polar regions. This alone would cause the cold air from either pole to
flow towards the equator as surface winds, and the warm air in the
equatorial belt to ascend and overflow aloft towards either pole. The
earth's rotation, however, influences the direction of these winds and
causes them to be deflected from the lines of longitude which they would
otherwise follow. In the northern hemisphere the air-currents are
deflected to the right and in the southern hemisphere to the left of
their initial directions. The best known examples of these planetary
winds, as they are termed, are the trade-winds, which blow from the
northeast in the northern and from the southeast in the southern
hemisphere. Between these two belts of converging winds lies the
equatorial belt of calm, some 300 miles wide, which also encircles the
earth and is termed the doldrums.
In the quadrant of the earth's surface occupied by North America the
climatic conditions are controlled in a large measure by the planetary
winds. In the equatorial belt of calms the barometric pressure is lower
than on either side, the temperature is uniformly high, the air
is heavily charged with moisture, and torrential rains are frequent. In
the belt of the northeast trades the weight of the air for a given area
is greater than in the doldrums, the wind blows with remarkable
uniformity both of direction and force, the sky is normally clear, and
rain infrequent except when the warm moist air is forced upward either
by local storms or on coming in contact with high land. The trade-winds
blow across the West Indies, Mexico, and much of Central America. To the
north of the trade-wind belt is a belt of prevailingly high barometrical
pressure, light variable winds, narrower and less well defined than the
doldrums, which encircles the earth in the region of the Tropic of
Cancer. This belt of calms, although familiar to sailors, to whom it is
known as the "horse latitudes," is ill-defined on the land, where its
presence is masked by changes due to local conditions. To the north of
the tropical calm belt the prevailing surface winds are from the
westward, and owe their direction to the constant flow of the upper
air-currents in their poleward journey, under the influence of the
earth's rotation. This great belt of winds from the westward crosses the
portion of North America including the United States and southern
Canada, but it is subject to many disturbances. The northern portion of
the continent extends into the little known polar region of prevailingly
low barometrical pressure, where midsummer and midwinter calms normally
prevail.
The great world-encircling currents of the atmosphere, namely, the
trade-winds, blowing towards the southwest or west across the Caribbean
and Mexican region, and the prevailing westerlies, or winds blowing in
an easterly direction, over the broad temperate portion of North
America, exert the main control on the climate of the continent.
_The Seasons._--Of primary importance to the inhabitants of North
America is the fact that the climatic belts determined by the
inclination of the earth's axis to the plane of the ecliptic are subject
to annual migration towards the north and south. In the torrid zone the
equatorial belt of calms, with its humid and oppressively hot
atmosphere, prevailing cloudiness, and heavy rains, and the belt
of the northeast trades, with its prevailingly clear skies and
refreshing breezes, do not occupy the same positions throughout the
year, but migrate with the sun. The migration of these two strongly
contrasted climatic belts brings to the otherwise remarkably uniform
conditions of the atmosphere over the West Indies, Central America, and
Mexico, two, in general well-defined, periods each year, namely, a wet
and a dry season, the former occurring in the summer and the latter in
the winter. It is to be borne in mind that between the tropics there
are, with certain local exceptions, but two seasons each year, the
leading contrasts of which are determined by differences in rainfall.
To the north of the Tropic of Cancer the seasonal changes are more
varied than in the torrid zone, and contrasts in temperature become the
most marked climatic feature; while precipitation, although in general
somewhat evenly distributed throughout the year, is more abundant in
winter than in summer. On account, however, of the greater diversity in
the climatic changes experienced each year within the temperate zone,
four seasons are recognised, the most distinctive features of which
depend on changes in both temperature and humidity.
In the northern portion of the temperate zone, and extending over the
arctic zone, the seasons are again reduced to two, summer and winter,
the contrasted conditions pertaining mainly to temperature and light.
A marked variation, which has an important bearing not only on climate,
but on the distribution of life encountered in passing from equatorial
to polar regions, is found in the distribution of light. Between the
tropics the number of hours of light and darkness each day is
approximately equal; in the temperate zone there is considerable
diversity from season to season, which increases with increase in
latitude; and uniformity, of a different character than at the far
south, again becomes prominent in the frigid zone, where the number of
hours of light each day is greatly prolonged during the summer and
correspondingly decreased during the winter. The extreme contrast
occurs in the neighbourhood of the pole, where during the summer season
the sun is continuously above, and in winter continuously below the
horizon, or in familiar language, there is a six-months day (light) and
a six-months night (darkness).
In going from the equatorial to north polar regions there is a general
decrease in mean annual temperature, and in general a decrease also in
precipitation, but great variations in these gradual changes, with
increase in latitude, occur which are both continental and local in
character. In winter the interior portions of the continent, and
especially the plateaus and mountains, are colder than the lands in
corresponding latitudes near the oceans; while in summer the reverse is
true, the margin of the continent being cooler than the broad interior.
In this general view of the climatic zones and the normal changes they
undergo we may note that the torrid zone is characterized by its
simplicity and monotony of climatic conditions, although disturbed at
times, especially in the West Indies, by occasional great cyclonic
storms, termed hurricanes, which occur, however, at quite definite
seasons. The temperate belt is equally well marked by its complex and
frequently changing atmospheric conditions, the winds being subject to
numerous and great variations, and storms of diverse character being
frequent. The frigid zone, again, is without conspicuous variations
except during the change from its monotonous summer to its still more
uniform winter weather, and the reverse change six months later. The
disturbances in the balance of atmospheric conditions at the far north,
or the storms, are of a much less varied character than in the fickle
temperate zone--thunder-storms and tornadoes, for example, being
unknown.
It is the summer migration of a heated belt from the south northward
across the temperate zone, and the equally conspicuous winter advances
of cold from the north southward across the same broad region, which
gives to the United States and the southern portion of Canada a
conspicuously changeable climate. The temperate zone, so far at
least as North America is concerned, deserves its name only when the
mean of the yearly changes in temperature is considered, as much of it
is hotter in summer than equal areas between the tropics, and in winter
over all of its northern half the cold is, at times, nearly or quite as
intense as during the same season in the far north. As a whole, the
portion of the continent embraced in the temperate zone is characterized
by its pronounced seasonal changes, including wide extremes of heat and
cold over large areas, and by its frequently sudden and strongly marked
weather changes during short periods of time. It is a highly suggestive
fact that of all the great climatic zones the one having the most
changeable climate, the greatest extremes of heat and cold, and the most
frequent storms should be the one in which man has reached the highest
development both of body and mind. Evidently it is the _struggle_ for
existence, when not too severe, which insures advancement. The part of
North America most densely inhabited by descendants of Europeans, and
the portion of the continent where intellectual development has made the
greatest advance, is the east-central portion, where not only the
variation of climate from season to season, but the weather changes from
week to week and day to day are the most conspicuous.
_Secondary Conditions influencing Climate._--While the primary
conditions controlling the climate of North America in common with all
other portions of the earth's surface depend on the relation of the
earth to the sun, there are many secondary conditions to be considered.
First in importance among these, so far as the broader features of the
climate of the continent are concerned, is the unequal heating of land
and water areas. During summer, more especially in the temperate zone,
the land becomes more highly heated than the adjacent oceans, and an
inflow of the cooler and moister air from the sea over the land occurs.
In winter the land cools more quickly and to a greater degree than the
adjacent waters, and the tendency of the heavier air over the land is to
flow outward as surface winds. Continental winds are thus generated,
similar in their origin to the familiar land and sea breezes of the
ocean shore in summer, but on a large scale, which have an
important bearing on the seasonal changes. The influence of the
continental winds is sufficiently well marked to give North America two
general classes of climate. One pertains to inland regions, is
characterized by great contrasts in temperature and humidity between
summer and winter, and is termed continental. The other pertains to the
border of the land where, on account of the equalizing influence of
large water borders, the contrast between the climate of summer and
winter is less pronounced, and has received the general title of oceanic
climate. The climate of the Dakotas, for example, is of the continental
type, while that of New Jersey is of the oceanic type.
The unequal heating and cooling of adjacent portions of land areas also
produces important atmospheric movements, as, for instance, when broad,
treeless plains become more highly heated in summer than adjacent
forested areas; or on account of rapid radiation become excessively cold
in winter and lower the temperature of the air above them. In the first
instance an inflow of cooler and heavier air from adjacent regions would
be established; and in the second example the chilled air would tend to
flow outward, thus, in each instance, establishing winds which usually
acquire a more or less well-pronounced circular motion. The Prairie
plains and the Great plateaus to the east of the Rocky Mountains become
highly heated in summer, and together with several other similar regions
in North America, meet the first of the conditions just considered;
while the higher portions of the Great plateau, especially at the north,
and the still more elevated mountains of Montana, Colorado, etc., become
excessively cold in winter and illustrate the other extreme.
Mountains serve to deflect the winds blowing against them either to one
side or upward, the former frequently producing important changes in
direction of the surface air-currents, and the latter, by causing the
air to rise, permits of its expansion and consequent cooling, thus
favouring precipitation. For this and other reasons precipitation
increases with elevation, at least until an altitude of many
thousands of feet is reached, and the mountains are cooler and more
humid than the adjacent valleys. The air-currents on passing over a
mountain range and descending are warmed by compression, and having lost
a part and in many observed instances a large percentage of the moisture
they previously contained, become warm, drying winds. The chinook winds,
as they are termed in America, are marked examples of the influence
exerted by mountains on climatic conditions.
What are termed above the secondary conditions, tending to modify
climate, produce such great changes in the distribution of rainfall,
temperature, etc., and in the influence of the planetary winds, that the
subdivision of the northern hemisphere into torrid, temperate, and
frigid zones, while based on astronomical data, does not serve to
represent actual conditions, except in a general way, in reference even
to the single element of temperature expressed in these names. A
comparison of the isotherms and of the distribution of precipitation as
indicated on the preceding maps, with the parallels of latitude, shows
at once that these two most important elements of climate are
conspicuously independent of distance from the equator. A logical basis
for subdividing the continent into _climatic provinces_ must therefore
be sought in other directions.
CLIMATIC PROVINCES
In order to obtain a comprehensive idea of the climate of a continent,
it is obviously desirable to subdivide it into areas having more or less
similar and distinct atmospheric conditions. The leading difficulty in
making such subdivisions is the well-known fact that the climate of any
region which may be chosen passes by insensible gradations into that of
adjacent regions, and any boundaries that may be drawn are to a
considerable extent artificial and arbitrary. While the true basis on
which to establish climatic areas or provinces is the resultant of all
the weather elements which go to make up the atmospheric conditions
recognised under the broader term climate, so many factors have to be
considered that it is extremely difficult to arrive at a general
acceptable conclusion. The principal elements of the weather to be
considered are, approximately, in the order of their importance,
beginning with the one which exerts almost universal control--temperature,
precipitation, the winds, absolute and relative humidity of the air, and
evaporation.
[Illustration: PLATE III.--Climate & Life Provinces.]
In North America there are voluminous records in reference to each of
these elements of the weather, embracing considerable lengths of time,
and relating mainly to the United States and southeastern Canada, but
not sufficient to enable one to subdivide the entire continent into
climatic provinces. The lack of weather records embracing the entire
continent may be supplied in part by what may be termed the natural
records of atmospheric conditions as expressed by the flora and fauna,
as well as by soil conditions and topography. In recognition of this
principle, the climatic provinces of North America here adopted have
been made to conform to its life-zones.
The major climatic divisions of North America here provisionally adopted
are, in their general order from south to north, the _Tropical_, _Lower
Austral_, _Upper Austral_, _Transition_, _Boreal_, and _Arctic_ (Plate
III). These several divisions are termed climatic provinces, and are
assumed to coincide with those of the life-regions as mapped by C. Hart
Merriam. The basis for classification is mainly temperature. In the
main, the northern boundaries of the provinces and their higher limits
in mountainous regions are determined by the temperature of the season
of growth and reproduction among plants and animals; while their
southern boundaries or lower limits on the mountains are determined by
the temperature of a brief period during the hottest portion of the
year. A more definite account of the reasons for choosing these
limitations will be given later in discussing life areas. While the
principal basis for establishing climatic provinces is temperature, many
other conditions are also recognised, chief among which is
precipitation. Several of the climatic provinces have two divisions,
namely, a _humid_ and an _arid_, the dividing line being
approximately the one hundredth meridian. These are well defined and
important in the tropical, austral, and transitional, but less definite
and less well known in the boreal and arctic provinces. The regions
embraced in the several climatic provinces named above, as well as their
humid and arid divisions, so far as now understood, are shown on the
accompanying map.
_The Tropical Province_ (Plate III).--This is the most southern of the
climatic provinces which it is convenient to recognise in North America,
and includes the West Indies, Central America, and southern Mexico,
together with a narrow strip on each coast of northern Mexico and the
extreme southern ends of the peninsulas of Florida and of Lower
California. While the land areas in this widely extended province
present conspicuous differences, their climate in general is
characterized by a high mean annual temperature with but moderate
seasonal or daily variations, and by the occurrence in general of a wet
and a dry season each year. The prevailing winds are the northeast
trades. While the average yearly temperature is high, being in general
about 80° F., the heat in summer is less intense than in many portions
of the austral provinces. In winter the temperature does not fall
sufficiently to produce frost, except on the higher mountains, which, in
fact, belong to one or more of the other provinces named above. On
ascending the mountains a rapid change to cooler and even to frigid
zones is experienced. Snow occurs on the higher portions of the
mountains of Central America and Mexico, and in a few instances, as on
the great volcanic cones in sight from the City of Mexico, is perennial.
On the mountains just referred to all of the several climatic provinces
are represented by well-characterized zones, arranged one above another,
and presenting in epitome the general changes one would experience in
travelling from the Gulf of Mexico to the Arctic Ocean.
In marked contrast to the prevailing uniformity of temperature at
corresponding elevations throughout the tropical provinces is the
inequality in rainfall in reference to both seasonal periods and
differences in geographical position. Of the annual changes, the
most pronounced and characteristic is the alternation of wet and dry
periods. During the summer season, or in general from May to October,
the air is usually clouded for at least a portion of each day, and heavy
downpours of rain occur. Throughout the remainder of the year the clear
skies and refreshing breezes, such as on the ocean are normally
characteristic of the trade-wind belt, prevail. The remarkable
regularity with which these changes occur each year suggests at once
that they are due to the migrations northward and southward with the sun
of the great climatic belts encircling the equatorial region of the
earth. In summer the equatorial belt of calms and heavy rainfall not
only migrates northward and occupies a portion of Central America,
bringing to Costa Rica and Nicaragua cloudy skies and abundant
precipitation, but seems to be carried bodily still farther northward,
so that the influence of the southeast trades of the southern hemisphere
makes itself felt, and four somewhat well-marked annual changes occur,
namely, two wet and two dry seasons. What is known of the climate of
this extreme southern portion of the province under review indicates
that the seasonal changes, especially on the Caribbean slope, are less
well marked than in its central portion, and rain is frequently copious
in nearly every month of the year. In the region just mentioned the mean
annual precipitation, as at Greytown, for example, at the eastern
extremity of the proposed Nicaragua Canal, is about 250 inches, and in
exceptionally wet years reaches nearly or quite 300 inches. This is, so
far as known, the heaviest annual precipitation in any portion of North
America.
In the West Indies the rainy season begins, in general, in May and lasts
until October. On the lowlands of eastern and south-central Mexico the
wet season commences in June, and the rains increase until the end of
July and end in November. This region lies to the north of the northern
limit reached by the equatorial belt of calm, but the rains in the
summer season are due to the same general influence, namely, the
lowering of temperature in the northward-moving upper air-currents, and
their effect on the trade-winds. In Cuba and along the northern
coast of the Gulf of Mexico when the trade-wind belt migrates southward
in winter the influences of the southward-moving storm from the
Mississippi Valley and Atlantic States produces what are termed
_northers_, which bring a chill and at times frost, more especially in
Florida and on the higher portions of Cuba.
While the wide-reaching seasonal changes within the tropical province
depend on the migrations of the planetary winds northward and southward
with the sun, and are due primarily to astronomical conditions, there
are equally well-marked variations in rainfall dependent on or regulated
by geographical conditions. These are of two principal classes: First,
elevation of the land; and second, the relation of broad land areas to
the direction of the prevailing winds, each of which is abundantly
illustrated in the tropical province.
The mountainous islands in the West Indies receive a heavy rainfall,
especially on their windward or easterly slopes, while the low islands,
and less markedly the southwestern border of the higher islands, are
much less humid. The eastern side of Porto Rico, for example, has an
abundant rainfall, and was originally clothed with a luxuriant native
flora, including large forest-trees, while the lowlands on its southern
and southwestern border are subject to drought, and irrigation is
desirable to insure the growth of crops. Again, while the mountainous
islands of the Lesser Antilles, with their luxuriantly forested slopes,
present ideal pictures of tropical loveliness, low-lying Sombrero,
Barbuda, St. Martin, and other similar islands are so arid that guano
has accumulated on them to such an extent as to be of commercial
importance. The reason for these striking contrasts within narrow
geographical limits is readily seen in the influence of the highlands on
the trade-winds. These air-currents blowing from the Atlantic are warm
and contain a high percentage of moisture. As they advance, however,
they invade regions that are progressively warmer and warmer, and the
capacity of the air for moisture is correspondingly increased. For this
reason the trade-winds in crossing low land become drying winds.
When the warm humid air-currents are forced upward, however, they are
cooled in part by contact with the land, but to a greater extent on
account of expansion due to decreased pressure; the dew-point is thus
lowered, and when saturation is reached precipitation follows. This
explanation applies also to the low peninsula of Yucatan, which is
within the trade-wind belt, and is exceptional among the lands of
Central America, on account of its dearth of forests, but in this
instance, and also in reference to the similar barren condition of the
Bahama Islands, in addition to the lowness of the land, the influence of
the underlying porous, limestone rocks on the vegetable growths should
be considered. In the instances just mentioned the rain that falls is
quickly absorbed by the cavernous rocks, and surface streams are rare.
In Central America the influence of mountains on the climate is much the
same as in the West India islands; in fact, the narrow rugged belt of
land connecting the two Americas may, from our present point of view, be
considered as a great island situated mainly within the trade-wind belt,
and similar to Jamaica, for example, in its influences on the winds
blowing across it. The eastern slopes of the Central American mountains,
together with the adjacent lowlands, with the exception, principally, of
Yucatan, are well watered and clothed with dense vegetation, while on
the western slopes, and especially over the narrow fringe of lowland
adjacent to the Pacific, the rainfall is less than on the Caribbean
coast, and the forests are open with many grass-covered areas which are
favourable for agriculture. In the mountainous portions of the West
Indies and of Central America, on account of the more healthy conditions
on the leeward or drier sides, as compared with the windward or humid
slopes of the mountains, the towns and the principal portion of the
white inhabitants are located on their western borders. Owing to the
great humidity and the long-continued high temperature during the hotter
portion of the year throughout the tropical province, much of the
lowland to the eastward of the high mountains is swampy and unhealthy.
This low region in Mexico and Central America is known as the
_tierra caliente_, or hot country; on the mountains and plateaus, or in
general where the elevation is between 5,000 and 7,000 feet, is the
cooler and remarkably salubrious _tierra templada_; and at still higher
elevations occur the _tierra frie_. Owing to the decrease in temperature
with elevation, and the fact that the moist warm air is forced to rise,
and in consequence expands on passing over the highland, the rainfall
probably increases with elevation through the three zones just referred
to.
While the tropical province is characterized by the uniformity with
which its atmospheric changes occur, it is nevertheless in part subject
to occasional and exceedingly violent cyclonic storms termed hurricanes,
which begin in the torrid zone, travel northward (Fig. 26, page 210),
and make their influence felt in more than one of the climatic provinces
into which North America is here divided. Thunder-storms, frequently of
great violence, also occur, especially in the Central American region in
summer, when the doldrums migrate northward.
The trade-wind belt broadens in crossing the southern portion of the
North American continent, and on the west coast and during its greatest
northward migration reaches to southern California. As we have seen, the
lowlands not adjacent to mountains in the Caribbean region receive
little or no rain from the trade-winds, for the reason that the
prevailing air-currents are moving from cooler to warmer regions, and
therefore have their capacity for moisture increased as they advance
more rapidly than their thirst can be satiated. The trade-winds are thus
normally drying winds. The same principle holds true for continents as
well as islands. The trade-winds on reaching the eastern border of the
Mexican plateau are forced upward and part with much of their moisture
in the form of rain and snow, and on descending to the lower lands
bordering the Pacific are desiccating winds. The conditions are thus
much the same as on the lowlands situated to the leeward of the
mountains of the West Indies. The narrow fringe of low-lying country on
the west border of the main body of Mexico, together with the
peninsula of Lower California and a portion of the southern extremity of
California, are arid, although in immediate proximity to the ocean. The
leading characteristics of the climate of this, the arid portion of the
tropical province, are its small rainfall, clear atmosphere, high mean
annual temperature, moderate seasonal changes, and active evaporation.
The most typical portion of the arid region bordering the Pacific from
California southward lies in northwestern Mexico, where the mean annual
precipitation on the western slope of the central table-land is from 15
to 20 inches, but gradually diminishes as one descends to the lower
lands to the westward to 10 inches, and even to 5 inches or less. A
great portion of the lowlands is practically a desert, although, as is
common on the desert-like tracts of this continent, it is sparingly
covered with detached clumps of cacti, yuccas, and other similar plants
which live with the minimum of water.
The hot, arid lands of the southwest just referred to are similar in
position, in reference to the relation of land areas to the trade-wind
belts, as other trade-wind deserts, as they are termed, such as the
Sahara, which occur on the leeward side of continents where they are
crossed by these drying winds.
_The Lower Austral Province_ (Plate III).--This province embraces the
Atlantic and Gulf coasts of the United States from Connecticut
southward, with the exception of the tropical portion of southern
Florida; the Mississippi basin south of the mouth of the Ohio; and
includes also many of the valleys amid the Pacific mountains from the
northern boundary of California to central Mexico. The larger
geographical conditions on which the boundaries of the province depend
are the warm currents in the Atlantic, which ameliorate the temperature
of the adjacent land as well as supply it with abundant moisture; the
low elevation of the central continental basin, which permits of great
extension northward of the climatic conditions originating about the
Gulf of Mexico; and the mountainous character of the western portion of
the province, where the valleys have a markedly different
temperature and rainfall from the highlands.
The most southern portions of the lower austral province within the
border of the United States has a semitropical climate and is
characterized by its high mean annual temperature, abundant rainfall,
and uniformity of weather conditions throughout the year. The summers
are hot, but tempered by winds from the Gulf of Mexico and the Atlantic,
and the winters, although normally mild and without snow, are varied at
intervals by periods of cold which bring occasional frosts. This
semitropical division of the lower austral province embraces a narrow
strip of coast-land extending from South Carolina to southeastern Texas,
with the exception of the extreme southern end of Florida, and forms a
transition between the hotter and more humid tropical province to the
southward and the cooler and less humid region to the northward.
As the saying is, a tree is judged by its fruit; in a similar way we may
judge of the climate of a region by its products. The Gulf strip of the
lower austral province is the home of a number of plants and animals not
found farther north, as, for example, the cabbage palmetto and Cuban
pine, and several species of birds and small mammals. Among the
agricultural products of this narrow coastal belt which are suggestive
of its climate are rice, sugar-cane, and sea-island cotton; of fruits it
produces, especially in Florida, oranges, mandarins, lemons, limes,
shaddocks, and pineapples.
The humid portion of the lower austral province extends northward from
the Gulf strip, and presents a transition in climatic conditions between
the semitropical Gulf coast and the more markedly temperate climate of
the upper austral. This eastern division of the lower austral,
characterized by its mild winters, general absence of snow, long hot
summers with abundant rain, extends from eastern Virginia southward
about the southern end of the Appalachian Mountains, and in the
Mississippi Valley broadens so as to reach the mouth of the Ohio River.
Its western limit is in central Texas, where the mean annual rainfall
decreases to less than 20 inches, and forests give place to
treeless, grass-covered plains and plateaus.
Through this eastern portion of the lower austral the mean annual
precipitation is in general between 50 and 60 inches, and is so
distributed throughout the year that each month receives approximately
an equal share. In general, however, the rainfall is greater in winter
than in summer. The mean annual temperature of the humid portion of the
lower austral is from 60° to 68° F., the mean winter temperature 40° to
52°, and the mean summer temperature from 75° to 80° F. From these
records it may be inferred that the conditions are favourable for the
growth of trees. In its natural condition this entire region was clothed
with a varied and beautiful forest, consisting largely of broad-leaved
trees, but is also the home of the southern pine and the cypress. The
characteristic crops are cotton and corn (maize).
The western or arid portion of the lower austral province embraces
western Texas, a large area in northeastern Mexico, and circling about
the southern extremity of the Pacific mountains in central Mexico,
extends northward adjacent to the tropical border of the Pacific and the
Gulf of Lower California, into Arizona and southern California. A
detached area of this same province occupies the great Valley of
California.
The leading feature in the climate of the extensive and irregular region
just outlined is its aridity. The rainfall is too small to insure forest
growths; the land is treeless, except along the streams, and irrigation
is necessary for successful agriculture. With a sufficient amount of
water for irrigation, a great variety of fruits, etc., may be raised,
including many products usually considered as indicating tropical
conditions, such as mangoes, dates, figs, citrus fruits, olives,
pineapples, etc. Not only are the agricultural products numerous and
varied, but the yield per acre under the most favourable conditions is
far in excess of the best results reached in most regions where rain is
relied on to furnish the requisite moisture. Under the prevailingly
cloudless skies of the hot arid lands of the southwestern portion
of the continent insolation is intense and the growth of vegetation
phenomenal when the necessary amount of water is supplied. The land in
its present condition presents great contrasts, ranging from desolate,
sun-burned tracts which are almost absolute deserts, to the vivid green
of irrigated fields and the deep shade of heavily fruit-laden orchards.
_The Upper Austral Province_ (Plate III).--The portion of North
America embraced in this climatic province lies principally in the
central part of the United States, but includes also a narrow strip in
southern Ontario, adjacent to the north shore of Lake Erie, and a large
irregular area in the central plateau of Mexico. A marked feature of its
geography is its extreme irregularity in the portion occupied by the
Pacific mountains in the United States and Mexico. The reasons for this
lie mainly in the influence of the relief of the land on climate, the
direction of the prevailing winds, and varying distances from the ocean.
It is a familiar fact that boreal and even arctic climatic conditions
are met with on high mountains. The attention that is given to changes
in climate with increase in altitude is no doubt largely due to the fact
that the mountains present conditions which are exceptional and more or
less novel as seen from our accustomed point of view. A person living in
an elevated region, on descending into a deep valley, would be impressed
with the reverse order in which the climatic zones occur. In making such
a descent he would pass in succession from a boreal or perhaps arctic
climate, through a transitional or cold temperate, to the warm temperate
or upper austral province, and might even reach the semitropical
division of the lower austral. In the Pacific mountains within the
border of the United States the valleys are sufficiently deep to have
the climatic conditions here ascribed to the upper austral, and in the
southwestern portion of the United States descents may be made--as in
the Great Valley of California and in the arid basins of southern
Nevada, Arizona, etc.--sufficiently great to reach the lower austral.
The valleys amid the Pacific mountains, which fall in the upper austral
province, are in general low at the north in reference to
sea-level, and become higher and higher at the south. For example, the
upper austral region in central Washington is but 400 or 500 feet above
the sea, while in Mexico it lies in general at an altitude of between
4,000 and 6,000 feet.
The upper austral province may be termed warm temperate, with a marked
contrast between the heat of summer and the cold of winter. The summers
are long, with an average temperature of 70° or 75°, while the winters
are variable, with frequent cold periods when ice forms and snow-storms
are not rare. The snow seldom remains on the ground for more than a few
days at a time, however, except in the northeast, where the warm
temperate climatic conditions of the province under review merge with
those of the colder region to the northward embraced in the transition
province.
The upper, like the lower austral, presents two well-marked divisions in
reference to humidity--an eastern or humid and a western or semihumid
portion; the dividing line is in the neighbourhood of the one hundredth
meridian. In the eastern division the mean annual precipitation in the
Piedmont region to the east of the Appalachians and on the coastal plain
adjacent to the Atlantic in Maryland and New Jersey is from 40 to 80
inches, but decreases westward, and on the border of the Great plateaus
in Kansas and Nebraska is about 20 inches. In the western division the
annual precipitation is less than 20 inches, and agriculture without
irrigation is uncertain and usually impossible. To the east of the one
hundredth meridian the rain is somewhat evenly distributed throughout
the year, although an increasing dryness of the summer is easily
detected as one travels from east to west, but in the various upper
austral valleys of the Pacific mountain region the precipitation is
mostly during the winter, and the summers are practically rainless. The
marked difference in precipitation between the humid and semihumid
division of the upper austral province is recorded on the surface of the
land by the vegetation. In the eastern division the entire region, with
the exception of the prairies in the central part of the Mississippi
basin, was originally clothed with a varied and beautiful forest,
consisting mainly of broad-leaved trees, such as the hickory, maple,
oak, etc., while the semihumid western division is treeless, except in
immediate proximity to streams.
In the southern portion of the humid division of the upper austral
province cotton is one of the staple products, but the northern limit of
the region in which it can be successfully cultivated is soon reached as
one travels northward. Tobacco is grown extensively in the southeastern
and eastern portions of the province. The principal crop of the great
central area in the Mississippi Valley is corn (maize). Successful wheat
culture begins in the northern portion of the province, but the
conditions favouring its cultivation increase to the northward and it
becomes the characteristic and most valuable crop of the transition
province.
In the western or semihumid division of the upper austral the variety of
agricultural products that can be successfully cultivated with the aid
of irrigation is greater than in its eastern portion, where irrigation
is not generally practised. The northern limit at which tobacco, fruits,
the vine, etc., may be advantageously cultivated in the west is greater
than in the east. For example, in the east the northern limit at which
tobacco is raised on a commercial scale is in Connecticut, while in the
west it reaches a large size and excellent quality in central
Washington. Various fruits, such as the peach, pear, plum, grape, etc.,
have their northern limit of successful cultivation in the east in
western New York, southern Ontario, and southern Michigan, a region
favourably influenced in this connection by the proximity of the Great
Lakes; in the west these same fruits reach a high degree of perfection,
and are produced in great abundance, with the aid of irrigation, in
north-central Washington, fully 5 degrees of latitude farther northward.
On the whole, the upper austral province may be said to have a warm
temperate climate, in which the summer season is longer and more
pronounced in its characteristics than the winter season. It
presents sufficient seasonal variations, however, to favour in a high
degree both the physical and intellectual development of man.
_The Transition Province_ (Plate III).--This, the transition region
between the austral and boreal provinces, includes the cool temperate
portions of North America. Like the austral provinces, its outlines are
irregular, and in places it occupies detached or island-like areas, on
account of the influence of mountains on climatic conditions. Its
largest continuous area is situated along the northern border of the
United States, but includes the southern portions of Assiniboia,
Ontario, and Quebec, and extends from the Atlantic to the Pacific Ocean.
From this main belt there is a marked extension southward along the
Appalachian Mountains, which carries a cool temperate climate into
northern Georgia, and another and much greater southward extension along
the Pacific mountains, which reaches central Mexico. In the northern
portion of the United States and adjacent parts of Canada, the region
under consideration has, in general, an elevation of 1,000 feet or even
less above the sea, but it rises when followed southward along the
mountains, and in the southwestern portion of the United States and on
the table-land of central Mexico attains an elevation of some 8,000 or
9,000 feet. On the higher portions of the mountains of Central America
and the West Indies the climatic conditions are similar to those of the
regions farther north here included in the transition climatic province,
but these isolated areas are not sufficiently well known to be indicated
on the accompanying map.
The mean annual temperature of the transition province is lower than
that of the upper austral, and, although a precise average is not at
present attainable, may be taken at about 45° F. The winters are long
and cold, especially in the northern part of the United States and
adjacent portions of Canada, the mean temperature being approximately
20° or 25°, but sudden and great variations are not uncommon. At times,
and frequently for continuous periods of several days, the temperature
falls to 20° or more below zero of the Fahrenheit scale, then again
rises above freezing, and the frozen soil thaws and possibly
becomes entirely freed from ice.
In common with the austral provinces, the one under consideration is
divided into two portions, an eastern and a western, in reference to
precipitation, the dividing line being a little to the eastward of the
one hundredth meridian. While the western portion of the province is
characterized by its small rainfall, precipitation is greater, mainly on
account of greater elevation, than in the adjacent portions of the
austral provinces, and in Oregon and Washington there is a markedly
humid area.
Snow falls throughout the entire transition province, at least during
exceptional winters, and in general during every winter. There is great
variation in the depth of the snow from winter to winter, and also with
geographical position. It is greatest in the northeast--that is, from
the Atlantic coast westward to Wisconsin and Minnesota--and least on the
Pacific coast and the southern portion of the Pacific mountains. Over
the northeastern portion of the province the snow frequently whitens the
ground for weeks, and even for two or three months continuously. A deep
accumulation which remains for a long time unmelted is welcome, as it
protects the roots of plants from sudden changes of temperature and
prevents alternate freezing and thawing of their sap, which is injurious
to their tissues in numerous instances. Great variation in the amount of
snow that falls annually in a given locality is of common occurrence. A
large proportion of the yearly accumulation frequently occurs during one
or two great storms. For example, in January and February, 1898, there
were two severe storms, accompanied by an unusual depth of snow, the
first being most pronounced over New England, and the second in the
region of the Great Lakes. Other storms increased the amount of snow so
that at the beginning of March the average depth in Maine was 40 to 70
inches, in New Hampshire and Vermont 10 to 40 inches, and in
Massachusetts 10 to 20 inches, while in Michigan and Wisconsin the
general depth on level ground was 1 to 2 feet, with many drifts 10 to 15
feet deep.
[Illustration: FIG. 25.--Ice-palace erected in Montreal, Canada, during
the winter of 1889.]
The winter in the northeastern portion of the transition province may be
said to be the most characteristic feature of the climate, as it is the
one that is most pronounced and exceptional, when a comparison is made
with other thickly peopled portions of the continent. The period of cold
and snow each year is long, extending in general from November to March,
and the coming of the flowers and birds in spring is frequently much
delayed. The long cold winters have a decided influence on plant and
animal life, and in a marked way modify the lives of men. In the
northeastern portion of the United States and adjacent provinces of
Canada various forms of sleighs are extensively used during the winters,
and skating on the frozen lakes and streams and excursions on snow-shoes
over the fields and through the forests are a popular and healthful
exercise, while coasting and tobogganing--or to explain these terms to
people living in regions where snow does not fall, the sliding down
steep snow- or ice-covered slopes on sleds or flat-bottomed
toboggans--are highly enjoyable sports indulged in by children and grown
people alike. In certain cities, notably Montreal and Quebec, what are
termed ice-palaces (Fig. 25) are built of blocks of ice and are utilized
for winter carnivals.
The summers throughout the transition province are hot, with little rain
in the western portion, but refreshing showers and occasional
destructive storms in the humid eastern portion. Owing to the latitude
of the main transcontinental belt of the province, the number of hours
of sunlight each day in summer is increased beyond what it is in the
main portions of the austral provinces, thus favouring the growth of
vegetation. There is also a lengthening of the morning and evening
duration of twilight, and magnificent sunrises and sunsets are frequent.
The mean summer temperature is in the neighbourhood of 70° F., but hot
spells, lasting for days, and even weeks, are of common occurrence.
During these trying and frequently unhealthy intervals the temperature
in the shade reaches or even exceeds 100° F., and sunstrokes or
prostrations by reason of the heat, particularly in the cities, are
numerous. The four seasons of the year are better marked and have
more pronounced characteristics in this division of the continent than
in any other, and it is the region of greatest seasonal climatic changes
as well as of marked weekly and even daily variations in weather
conditions. The most delightful months to most people are May, when the
returning migratory birds are nesting, the trees unfolding their many
tinted leaves, and the air laden with the perfume of multitudes of
blossoms, and October, when the rich colours of ripened leaves give to
the forests a marvellous variety and brilliancy of colour and the
tranquil, hazy atmosphere is undisturbed by storms for days and even
weeks together. This annual period of tranquil weather, extending
frequently far into November, is known as Indian summer.
In the northern portion of the transition province the broad-leaved,
deciduous trees of the central and eastern portions of the United States
reach their northern limit, and become mingled with a southward
extension of the conifers which form the major portion of the forest of
Canada. A similar but less marked change occurs among the Pacific
mountains, where the scattered growths of oaks, piñon pines, sycamores,
etc., of the lower mountain slopes and stream sides mingle with the
spruces and yellow and white pines of the more elevated region, where
the climate is similar to that of central Canada. As remarked by
Merriam, the province as a whole is characterized by comparatively few
distinctive animals or plants, but rather by the occurrence together of
southern species which there find their northern limit and northern
species which there reach their southern limit. It embraces the northern
portion of the truly agricultural lands of the continent. The plants of
economic importance which there reach their highest stage of perfection
are wheat, oats, and other cereals, the sugar-beet, numerous vegetables,
the white potato, apples in great variety and abundance, cherries,
plums, grapes, etc. It is the northern limit of corn, and includes
nearly the entire area in which maple-sugar is produced. In the eastern
portion of the province several varieties of native nuts, such as the
beechnut, butternut, chestnut, hazelnut, hickory-nut, walnut,
etc., grow wild and in great abundance; but nut-bearing hardwood trees
are also a characteristic feature of the forests of the humid portion of
the austral provinces.
In the western division of the province a humid area--embracing western
Washington and Oregon, part of northern California, including the Coast
Range of the same States--presents a marked contrast to the more widely
extended and excessively irregular arid portion which surrounds the
higher mountains and is for the most part remote from the ocean. Both
the humid and arid divisions of the western part of the province are
alike favourable for agriculture, as is shown by the vast and highly
productive wheat-fields of the semihumid eastern portion of the States
just named and the productive hop lands, orchards, and vineyards of
their humid western portions.
The climate of a great land area not only finds expression in its fauna
and flora, but in the industries and the intellectual development of its
people. While it is difficult to translate man's physical and
intellectual development into terms of climate, it is evident that the
transition province favours both bodily and mental activity more than
any of the other climatic provinces into which North America is here
divided. Although the boundary between the upper austral and the
transition provinces is indefinite, it is easily to be seen, from the
geographical distribution of cities, agricultural population,
manufactories, colleges, and other institutions of learning, etc., that
the climate of the province under review is on the whole the one in
which the greatest intellectual advance has been made and the one which
holds out the greatest promise for the future.
_The Boreal Province_ (Plate III).--This climatic division of North
America extends in a broad belt diagonally across the continent from the
eastern portion of Labrador nearly to the shore of Bering Sea, and is
represented by detached areas in both the Atlantic and Pacific mountains
far beyond its general southern limit. Its northern border, in the
Continental basin, is marked by the cessation of forests, and on the
mountains to the southward its upper limit coincides with the
timber-line. Its leading climatic features are its low mean
annual temperature--in general from 32° to 40° F.--its long, cold
winters, and short, hot summers. The differences in mean annual
precipitation in various parts of the province are less marked than in
the several provinces previously noticed, but in the far north a cold
arid division should be recognised. Although but few direct measures of
precipitation are available for comparison, our general knowledge of the
great boreal province and the character of its vegetation indicate that
there is a decrease in precipitation from both the eastern and western
borders of the continent towards the interior, and also from its central
portion both northward and southward. The heaviest precipitation is on
the Pacific coast, from California northward to southern Alaska, and the
lightest precipitation is probably in the central Continental basin,
near the northern limit of the province. Precipitation on the Pacific
coast at low elevations is almost entirely in the form of rain, but on
the mountains there is in winter deep snow which remains for a number of
months unmelted. Throughout the portion of the province included in
Canada and Alaska the snowfall is abundant, but heaviest towards the
Atlantic coast. Along the northern margin of the province, as indicated
by observations at a small number of stations, not only is the mean
annual precipitation light, probably under 20 inches, but the winter
snow is not deep, although it remains on the ground continuously for
five or six months. In the main or northern portion of the boreal
province, owing to the comparatively high latitude, the variation in the
number of hours of light and darkness each day during a year becomes
conspicuous. In summer the sun is above the horizon from eighteen to
twenty-four hours each day, and in winter the hours of darkness are
correspondingly increased. The year is divided into but two seasons,
summer and winter, the distinctive features of spring and fall, so well
marked in the upper austral and transition provinces, disappearing. On
account of the low mean annual temperature, and especially because of
the shortness of the growing season, agriculture is of small importance.
Along its southern border, more especially in southeastern Canada and
Newfoundland, such small fruits as currants, huckleberries,
raspberries, blackberries, cranberries, etc., grow wild and yield
abundant returns when cultivated. In favoured localities white potatoes,
turnips, beets, and certain varieties of the apple, as well as the more
hardy cereals, are cultivated with moderate success.
_The Arctic Province_ (Plate III) comprises the cold, treeless plains
sloping to the Arctic Ocean and the summits of the higher mountains at
the south which rise above the transition province. The one controlling
climatic feature is the low temperature, the mean for each year being
32° F. or lower. The winters are longer and more severe than in the
boreal province, and the summers short and hot. Insolation, on account
of the length of the days in summer of the main area of the province and
the free exposure on the mountain summits to the southward, is intense,
but its beneficial effect on vegetation is largely counterbalanced by
the influence of the lingering snow and ice. In the mountainous regions
of North America the arctic province is the birthplace of numerous
glaciers. Although destitute of trees, the arctic, or arctic-alpine
province, as it may be termed, is rendered glorious in numberless
localities by the profusion and brilliancy of its flowering annuals.
SECONDARY DISTURBANCES OF THE ATMOSPHERE
In the broad, general movements of the atmosphere over North America
embraced in what are termed the planetary and continental winds there
are many disturbances due to more or less local changes in conditions,
the most conspicuous of which are whirlwinds, chinook winds,
thunder-storms, tornadoes, cyclones, and hurricanes. While some of these
disturbances are local, as the whirlwind and tornadoes, and may not
extend beyond the boundaries of the particular climatic provinces where
they originate, others, as the cyclones and hurricanes, may affect the
climate of several provinces.
_Whirlwind._--A conspicuous, although minor feature in the atmospheric
phenomena of the hot, dry plains and valleys, especially of the
Mexican plateau and the Great Basin, and less markedly of the Great
plateau to the east of the Rocky Mountains, is the occurrence of small
whirlwinds which carry dust and light objects into the air in spiral
columns that are not infrequently 2,000 or 3,000 feet high, and have a
diameter of perhaps 50 to 100 feet. These small whirls of the air, in
which some of the characteristic features of the intensely active
tornadoes and widely destructive tropical hurricanes can be studied on a
small scale, occur most commonly during hot summer afternoons, when from
a commanding station half a dozen or more swaying columns may be seen
moving in various directions over the parched valleys and sun-scorched
plains. These columns not only move in various directions, showing that
they are not due to the same immediate cause, but have different
internal motions, some whirling from right to left, and others in the
opposite direction.
The generally accepted explanation of these small whirlwinds is that the
air over the surface of the deserts, which are frequently almost bare of
vegetation and perhaps white with saline incrustations, becomes locally
highly heated, especially when there is little or no wind, and is forced
upward by the inflow of the surrounding cooler and heavier air. The
inflowing currents have different velocities, and on meeting the
strongest one gives a rotary or spiral motion to the ascending column,
which acts like a chimney in allowing the escape upward of the hot air
from below. A central vertical line frequently seen in the dust columns
shows that a core of comparatively still air is present, about which the
dust-charged air rises in a spiral course. If the conditions just
outlined should be greatly increased in magnitude some of the leading
features of tornadoes and even of hurricanes would be produced. In
short, all of the winds cited above, except the chinook, are concentric,
swirling movements in ascending air, due primarily to a local increase
in temperature at the lower portion of the atmosphere.
_Chinook Winds._--On the Great plateaus adjacent to the Rocky Mountains,
and in similar situations to the eastward of the Sierra Nevada
and Cascade Mountains, warm, drying winds frequently occur, especially
in winter, when they bring a balminess as of spring. The remarkable
feature of these interesting winds is that they come from the snow-clad
mountains, but are warm and dry in contrast with the preceding condition
of the air on the plains. The capacity of the air brought by these winds
for moisture is so great that evaporation is active, and the snow in the
valleys and over the broad plains disappears without visible melting.
The change in the previously winter aspect of a region within the
influence of these _chinook_ winds, as they are termed, is truly
surprising, and to their influence is due to a marked extent the value
of the Great plateaus as stock-ranges, for the reason that the snow is
removed from them so as to allow cattle to feed on the naturally dried
grasses.
The chinook winds are the counterpart of the _foehn_ winds of
Switzerland, and are explained on the principle that descending air is
made more dense by the increased pressure to which it is subjected, and
its temperature correspondingly raised, its capacity for moisture being
at the same time increased on account of its rise in temperature. The
apparent anomaly of a warm, dry wind blowing from a snow-clad mountain
range is no longer a mystery, if we consider that the air is drawn over
the mountains towards a centre of low barometrical pressure owing to the
wide-reaching influence of a cyclonic storm or other large atmospheric
movement. The air as it rises in order to cross a mountain is cooled,
largely on account of relief of pressure, and parts with a portion,
possibly a large portion, of its moisture, which condenses on the
mountain commonly as snow; on passing the mountain the air descends and
is warmed by compression, and having less moisture than before, becomes
a drying wind, which produces the sudden and surprising changes on the
plains and valleys to the leeward.
The chinook winds of the western portion of Canada and the United States
occur principally to the eastward of high mountains, for the reason that
the prevailing air-currents of that region are from the west.
_Thunder-Storms._--In the eastern portion of the United States and
adjacent parts of Canada during the summer season the heating of the
lower portion of the atmosphere, especially on still, sultry afternoons,
causes ascending currents of warm, moist air, which become cooled as
they rise, and give origin to vast masses of cumulus clouds. These
magnificent "thunder-heads," as they are sometimes termed, illuminated
by the full sunlight are most magnificent, and usually herald the coming
of heavy showers, accompanied by frequently destructive lightning and
heavy thunder. The bases of the clouds when seen from a distance are
usually horizontal and may have curtain-like festoons beneath, due to
falling rain; while aloft the white vapour boils upward in fleece-like
masses, revealing a strong convectional ascent of moist air. The
immediate cause of a thunder-storm is the rapid ascent of a column of
warm moist air, which becomes cooled as it rises and the moisture
contained in it condensed. The cause of the ascent of the air column, at
least over plains and plateaus, is the heating of the air in contact
with the earth. A layer of warm, and consequently light, air beneath a
layer of cooler and heavier air furnishes unstable conditions which
favour an overturning and an escape upward of the lighter air, which is
forced to ascend much as the hot air in a chimney is made to flow upward
by the pressure of cooler and heavier air around. The conditions
preceding a thunder-storm are a stagnant atmosphere over a broad region
where the lower layer of hot air is also charged with moisture. These
conditions are frequently fulfilled on the plains of the Atlantic slope
and southeastern portion of the continental basin in summer when warm
moist air is drawn in from the Gulf region towards the centre of an area
of low atmospheric pressure, and thunder-storms are there a
characteristic feature. The storms usually advance northeastward, the
direction being determined by the flow of upper air-currents, and move
over the country with a breadth of from 10 to perhaps 100 miles, and
send down copious supplies of refreshing rain.
Over the Great plateaus the air near the earth's surface is
highly heated during the summer season, but it is deficient in moisture,
and thunder-storms are rare, except for a brief period in late summer or
fall when the normal conditions are disturbed.
Thunder-storms are almost unknown in the great Canadian-Alaska province
and along the cool and humid northwest coast. They are also of rare
occurrence in the hot and dry atmosphere of the Great Basin and Mexican
plateau, but when they do come are of marked intensity, and pass under
the name of "cloudbursts." At the far south, in the region brought under
the influence of the equatorial belt of calm, thunder-storms are
frequent and of great intensity.
An upward ascent of warm moist air, in much the same manner as described
above, occurs about isolated mountains, particularly in the southern
portion of the Rocky Mountain chain, and summer thunder-storms are there
of frequent occurrence, especially in the afternoon, about the higher
mountain-peaks, while the adjacent valleys are flooded with sunlight.
Reference to this most striking phenomenon has already been made in
describing the Park Mountain.
_Tornadoes._--The fierce circular whirls in the air producing pendent,
spirally twisting clouds, which when they touch the earth are of such
intensity as to sweep away houses, trees, and nearly everything in their
paths, are known to meteorologists as tornadoes, although popularly, but
erroneously, termed cyclones. Storms of this character are of frequent
occurrence in the United States to the east of the Great plateau, and
are most numerous in the Mississippi Valley. Their path of destruction
is seldom over half a mile wide, and as a rule they progress towards the
northeast, in obedience to the movement of the upper air-currents, at a
rate of from 20 to 40 miles an hour, and may cut a swath from a few
miles to 20 or more miles long through forests, farms, villages, and
towns. They occur usually in the afternoon, and sometimes in the earlier
hours of the night, of warm, sultry days, especially in spring and early
summer, but are not strictly confined to that portion of the
year. The conditions which precede the coming of a tornado are, in
general, the same as those in advance of a thunder-storm--that is, an
indraft of hot, moist air beneath a cooler layer, thus establishing
unstable conditions. An upward draft is started, the intensity of which
becomes so great that the inflowing winds are given a rapid spiral
motion about a calm centre. The tornado may be considered as a fully
developed or exceptionally energetic thunder-storm, in which a spiral
movement is established as in desert whirlwinds. The conditions for the
origin of this class of dreaded and locally most destructive storms are
best fulfilled in the central portion of the Mississippi basin, where
they are somewhat frequent. They occur less commonly over the country to
the eastward, and are unknown in the more northern and western climatic
provinces, and, so far as the writer is aware, they have not been
reported from the region to the north of the United States.
_Cyclones._--This name is applied to the great atmospheric disturbances
marked by an inflowing of air towards a centre of low barometric
pressure from adjacent regions, commonly several hundred miles across,
and an escape and overflow aloft. As in whirlwinds and tornadoes, there
is a spiral movement established in the inflowing currents, but owing to
the large size of the area of low pressure, this seldom reaches
destructive violence. Cyclonic storms are of common occurrence,
especially in the temperate zone, and bring to that region its
characteristic diversity of weather. Most of the rain and snow-storms of
the continent are due to the vast swirls of the atmosphere about areas
of low atmospheric pressure, which cause air-currents from different
directions and with different components of heat and moisture to move
over the land.
The cyclonic storm of the Mississippi Valley, the Atlantic coast States,
and southeastern Canada frequently originate in the Great plateau
province, and are carried towards the Atlantic owing to the influence of
the eastward-blowing winds of the upper atmosphere. At times these
storms are of such magnitude and intensity that they cross the Atlantic
and are observed in England and Scandinavia. The courses they
follow may be traced from day to day on the weather-maps issued by the
United States Weather Bureau, and from the directions they are likely to
follow and the atmospheric conditions pertaining to their various parts
predictions of surprising accuracy as to the changes which the weather
in a given locality will experience can be made one or two days before
the changes occur.
_Hurricanes._--Cyclonic storms of the general nature of the tornadoes,
but of vastly greater extent and intensity, originate occasionally
during the latter portion of the summer season over the tropical portion
of the north Atlantic, move slowly westward to the vicinity of the
Lesser Antilles, where normally their courses bend northward, and then
skirt the Atlantic coast of the United States and drift eastward under
the influence of the eastward-flowing upper air-currents, and not
infrequently make their influence felt in the western portion of Europe.
Occasionally, on account of the presence of an area of high barometric
pressure to the north of Cuba, the course of one of these tropical
hurricanes, as they are termed, is rendered irregular, and it passes
over the Atlantic States or is deflected still more and crosses the Gulf
of Mexico before reaching the border of the continent, as was the case
in September, 1900, when a large part of Galveston was destroyed. The
normal paths of the tropical hurricanes as they approach the coast of
the United States and the exceptional course of the one which passed
over Galveston, are indicated on the map forming Fig. 26.
[Illustration: FIG. 26.--Tracks of West Indian hurricanes. The circles
on the tracks indicate the position of the storm centres at Greenwich
mean noon on successive days. The date of the several storms is as
follows:
1. Aug. 27-Sept. 1, 1890.
2. Aug. 19-Aug. 25, 1890.
3. Aug. 19-Aug. 31, 1891.
4. Sept. 4-Sept. 9, 1891.
5. Sept. 16-Sept. 25, 1891.
6. Sept. 28-Oct. 7, 1891.
7. Aug. 17-Aug. 22, 1892.
8. Aug. 15-Aug. 22, 1893.
9. Aug. 23-Aug. 28, 1893.
10. Sept. 6-Sept. 9, 1894.
11. Sept. 20-Oct. 4, 1894.
12. Oct. 5-Oct. 10, 1894.
13. Oct. 12-Oct. 18, 1894.
14. Oct. 24-Oct. 27, 1894.
15. Oct. 18-Oct. 25, 1895.
16. Sept. 5-Sept. 10, 1896.
17. Sept. 9-Sept. 25, 1896.
18. Sept. 26-Sept. 29, 1896.
19. Oct. 9-Oct. 14, 1896.
20. Oct. 23-Oct. 26, 1897.
21. Oct. 20-Oct. 23, 1897.
22. Sept. 11-Sept. 20, 1898.
23. Aug. 3-Aug. 25, 1899.
24. Aug. 30-Sept. 7, 1899.
25. Sept. 8-Sept. 14, 1899.
26. Sept. 1-Sept. 11, 1900.]
The analogy of a tropical hurricane to a tornado has already been
referred to, but while a tornado may lay waste a tract of country
perhaps half a mile wide, and in exceptional cases 20 to 30 miles in
length, a hurricane is from 200 to 300 miles in diameter, and may
continue to be destructive, on account of the rapid inflow of air from
the periphery towards the centre, for 2,000 or 3,000 miles. The velocity
of the spirally blowing winds which are the characteristic feature of
these great storms is frequently 100 miles or more per hour. In spite of
their magnitude, however, the conditions leading to their origin and
growth are essentially the same as in the case of tornadoes, and
even of the much smaller whirlwinds. They have their birth where the
moist, still air above the ocean in the region of the doldrums at the
season when the equatorial belt of calms is farthest north, becomes
highly heated and rises on account of the pressing in of cooler and
heavier air from adjacent regions. The ascending column is at first
carried slowly westward, in obedience to the general flow of the
atmosphere in the intertropical belt, and at the same time the currents
coming in from opposite directions give the ascending air a rotary
motion. As the currents from the northeast are stronger than those from
other directions, this whirling motion is from right to left, or
opposite to the movement of the hands of a watch. The whirling air
column extends into the upper atmosphere, and as it moves along past the
West Indies becomes influenced by the prevalent flow of the upper
air-currents, and is carried northwestward, and later eastward in a path
which approximates to a parabolic curve. The inward-rushing spiral winds
leave a calm centre, the "eye of the storm," which corresponds to the
hollow core of a whirlwind and the calm centre sometimes noted in
tornadoes. The upward ascent of warm, humid air is accompanied by a
decrease of pressure and consequent expansion and cooling which leads to
rapid condensation and a heavy downpour of rain; the change of the
moisture from a vaporous to a liquid form liberates heat, which serves
to perpetuate the upward flow of air, and thus prolongs the life of the
storm. During the passage of the central area of low barometric pressure
over a given locality the clouds frequently part and portions of the
clear sky may be seen. Accompanying the rain are frequent lightning
flashes, as during ordinary thunder-storms.
The tropical hurricanes are the most violent and most dreaded of all the
storms that sweep over any portion of our continent, but fortunately for
dwellers on the land, are confined for the most part to the sea, since
the atmospheric conditions over the land lead to their loss of energy,
although in rare instances they may be re-enforced by uniting with a
cyclonic storm, as happened in the case of the Galveston hurricane, and
thus continued after reaching the land. The destructiveness of the
hurricanes at sea has been greatly lessened in recent years, not only on
account of the general use of steam as a motive power for vessels
instead of the wind, but because meteorologists can designate the time
when they are likely to occur and the best method of sailing away
from them if encountered. Since the establishment of the United States
stations for observing and reporting the atmospheric conditions on the
West India islands, the approach of a hurricane can be foretold and
warning given to navigators and others of the coming danger.
EVAPORATION
An important element in climate is the amount of moisture the air
contains. The absolute amount of water vapour in a given volume of air
is of interest in this connection, but what is of still greater
importance is the ratio of the amount of water vapour present to that
which the air might contain, or what is termed the _relative humidity_.
The relative humidity, providing the actual amount of vapour present
remains unchanged, depends upon the temperature of the atmosphere. For
this reason, the warming of an air-current, as the trade-winds, for
example, in which the water vapour present may, previous to the warming,
have approached saturation, causes it to have a still greater capacity,
and hence decreases the relative humidity.
The winds in passing over the land may be either cooled or warmed, and
hence their influence on evaporation is continually changing; but the
mean rate of evaporation from an open water body can be determined for a
definite time, say a year, for various localities, and thus afford a
means of comparison between one region and another. Observation of the
mean annual evaporation for various stations, mostly within the United
States, have been made, and the result shown by lines drawn through
places where the rate is the same. A map showing this data, on which the
figures indicate the depth of evaporation in inches, is here presented.
The systematic study of evaporation, and especially the part played in
it by plants, has scarcely more than been begun on this continent, and
important results concerning its influence on atmospheric conditions are
to be expected. The subject is also of great importance in reference to
agriculture, the prevention of frost, etc.
[Illustration: FIG. 27.--Depth of evaporation. After T. Russell.]
LITERATURE
The great storehouse of information pertaining to the weather and
climate of the United States is the numerous publications of the United
States Weather Bureau, Washington, D. C. Similar bureaus exist at the
capitals of Canada and Mexico, which have issued valuable reports.
Of the many elementary and popular books on meteorology, the following
will be found helpful in continuing the study of the subjects outlined
in this chapter:
DAVIS, W. M. _Whirlwinds, Cyclones, and Tornadoes_, Lee & Shepard,
Boston, 1884; _Elementary Meteorology_, Ginn & Co., Boston,
1894.
FERRIL, W. _A Popular Treatise on the Winds._ Wiley & Sons, New
York, 1889.
GREELY, A. W. _American Weather._ Dodd, Mead & Co., New York,
1888.
_Maryland Weather Service_, vol. i, Baltimore, 1899. Contains a
valuable bibliography.
RUSSELL, T. _Meteorology._ Macmillan & Co., New York, 1895.
SHALER, N. S. _Aspects of the Earth._ Scribner's Sons, New York,
1889.
WALDO, F. _Modern Meteorology_, Scribner's Sons, New York, 1893;
_Elementary Meteorology_, American Book Company, New York, 1896.
CHAPTER IV
PLANT LIFE
If we take the trees as representatives of the flora of North America,
and this seems to be the only practicable method in a general treatise,
we find them growing most densely and presenting at the same time the
greatest variety where the temperature is uniformly high throughout the
year and the rainfall heavy and long-continued. From the torrid lowlands
the forests in general decrease in the variety and number of trees on a
given area, both towards the north, where temperature becomes the
controlling factor, and towards regions of small rainfall, where the
leading adverse condition is deficiency of moisture. In the most highly
favoured localities the struggle for existence between species and
species and individual with individual is intense, exposure to the
life-giving sunlight being the dominant aim of every one of the
contending hosts. As drier or colder regions are approached, but few
species can survive and the forests are characterized by their monotony.
Where the conditions of heat and moisture are such that the existence of
a species is precarious, the balance of power, so to speak, passes to
the secondary conditions; and the texture and composition of the soil,
slight differences in the relief of the land, and consequently in
drainage or in the degree of exposure to light, prevalence of fires,
etc., make themselves prominent and limit distribution.
[Illustration: FIG. 28.--Map showing the distribution of forests in
North America.]
From a geographical point of view, the broadest features in the flora of
North America are the forested and unforested areas. The distribution of
the forests, prairies, and treeless plains as they existed previous to
the coming of Europeans is shown on the accompanying map. For the
portion of the continent to the northward of Mexico the data on
which this map is based are much more abundant than for the southern
portion.
THE FORESTS
As is indicated on the map just referred to, the forests of North
America in a general way form a broad belt, for the most part within the
influence of winds from the ocean, which surrounds a large area of
treeless plains and plateaus in the west-central portion of the interior
continental basin, but is broken and rendered irregular in its
southwestern part of the treeless valley of the Great Basin region. The
irregular circular belt of tree-covered land is closed at the south by
the forest on the lowlands of Mexico and Central America. This vast
forest belt, extending from the Atlantic to the Pacific, and from Panama
to northern Canada, presents great variations even in its larger
features, and, for convenience, and also with the aim of expressing in a
rough way natural relationships, needs to be subdivided for purpose of
study. The basis for such a subdivision has already been suggested, as
the forests, like all other divisions of the life of the continent, are
an expression of climatic conditions--that is, the boundaries of the
botanical and zoological provinces should agree with those of the
climatic provinces.
On this basis we have the tropical forest, which covers the more humid
portions of the east and west margins as well as all of the southern
portion of Mexico, together with nearly all of Central America and the
West Indies, and includes the southern extremity of Florida. Within the
tropical forest, however, there are high mountains on which trees with
the general characteristic of those more northern floras find a
congenial habitat. The two austral and the transition provinces are to a
great extent clothed with diversified forests, which are naturally
divided into two portions: an eastern division, embracing the Atlantic
and Gulf border of the United States, together with the eastern part of
the Mississippi Valley and the Great Lakes region; and a western
division, in which is included the lands bordering the Pacific
from near Mount St. Elias southward to the vicinity of San Francisco,
and also several irregular branches or detached island-like areas on the
Pacific mountains, in the United States and Mexico. The former of these
divisions may, in a general way, be termed the Atlantic, and the latter
the Pacific forest. Separating them is the treeless west-central portion
of the Continental basin. Both the Atlantic and Pacific forests merge at
the north with the boreal forest, which extends diagonally across the
continent from Newfoundland to Alaska. Peninsula-like and island-like
areas occupied by the boreal forest occur in the sea-like expanse of the
transition and austral provinces, on both the Atlantic and Pacific
mountains.
The tropical and boreal forests have their greatest extension from east
to west or with the parallels of latitude, and are remarkable for their
uniformity in general characteristics, the reason being that climatic
conditions, and especially the temperature in summer, change less
rapidly along east and west than along north and south lines. The
Atlantic and Pacific forests, on the other hand, have their greatest
extension across the parallels of latitude, and hence experience marked
changes from locality to locality in both temperature and precipitation,
and are characterized by conspicuous changes from one locality to
another in the genera and species of trees of which they are composed.
In each of the areas occupied by the major divisions of the encircling
continental forest belt there are marked variations in elevation, which
are accompanied by corresponding climatic changes, and hence by
modifications in the forest growths. Of all portions of the continental
forest belt, variation in elevation is least marked in the forests of
Canada, and for this reason, in part, we there find the most uniform and
most monotonous of all the forests of the continent. The influence of
elevation, however, on climate and on both plant and animal life is
greater for a given measure, as for 1,000 feet, in the torrid than in
the cool or cold zone, for the reason that the possible range in
climatic conditions is much greater at the south than at the north.
_The Tropical Forest._--There are great areas in southern Mexico which
are clothed with a typical tropical forest; while other similar forests
cover nearly all of the lower portions of Central America, the larger or
more rugged West India islands, and the southern extremity of Florida.
Throughout this vast region, within the influence of the trade-winds and
of the equatorial rains, the forests are luxuriant and beautiful, except
on lowlands not adjacent to the windward side of mountains. The
characteristic trees of the hot, humid lowlands extend up the mountain
to an elevation of some 4,000 or 5,000 feet, where a change to the
aspects familiar in the lowlands of the temperate zone begins, and palms
give place to oaks and pines.
Of the many features of the tropical forests which impress a traveller
from colder regions, none excite greater wonder than the large number of
vegetable species growing in close proximity. It has been said, and
apparently the statement cannot be successfully challenged, that a
greater variety of plants may be collected on 100 square yards of
surface in the humid, tropical lowlands than can be found on 100 square
miles in the forest of central Canada. It is probably safe to extend
this striking contrast by saying that of the trees on a typical area in
the tropical forest of the size mentioned, there are in many localities
more species than in the whole of the subarctic forest.
Among the characteristics of tropical forests is the presence of many
kinds of plants on a limited area, hundreds of species struggling upward
to the light where there seems room but for one; the variety of mosses
and lichens; the profusion of flowering parasites; the luxuriance of the
vines, many of which are armed with spines; and the abundance of the
remarkable aerial roots termed _lianas_. Of the last there is a great
variety, some of them of large size and surprising length; they
frequently descend from plants entwined among the topmost branches of
great trees, looking not unlike the cordage of a forest of masts in some
crowded port, and on reaching the ground send out rootlets in the humid
soil.
In the depths of a tropical forest it is always twilight. Even at
noontide no shafts of yellow sunlight reach the ground to glorify mossy
banks and flower-gemmed dells, as in the open woods of temperate climes,
but a diffused greenish light, producing weird effects, alone penetrates
the dense leafy canopy far overhead. The roots of even the larger trees
in these hot, humid forests do not have to descend deeply in order to
find the necessary moisture or to receive protection from frost and
sudden changes of temperature, but are usually widely expanded and
thickly interwoven over the surface. The earth from which the dense
vegetation derives nourishment is surprisingly deficient in vegetable
mould, which is a characteristic feature in the moist forests of
temperate and even subarctic regions, where the complete decay of dead
vegetation is long delayed. In the tropical forests the annual supply of
dead vegetable matter suitable to be transformed into humus is far
greater than on a corresponding area in the woods of more northern
regions, but decay is so rapid, owing to the uniformly high temperature
and the conditions favouring the multiplication of bacteria, that even
great trees on falling quickly disappear; in many instances, the forms
of prostrate tree trunks are preserved and overgrown with luxuriant
mosses or gorgeously festooned with ferns and orchids, but soon become
fragile shells from which nearly all the woody tissues have been removed
by decay or by swarming colonies of insects. Where life is so exuberant
and the wants of growing plants so great it seems as if the food supply
was insufficient, and that none could be spared to accumulate on the
ground and form a soil.
The two most characteristic and distinctive classes of plants in the
tropical forests are the palms and the ferns, each of which is
represented by many genera, a large number of species, and multitudes of
individuals, and in each class there is a gradation in size from low
herbaceous growths to arboreal forms.
In every way worthy of first mention among the plants of the Caribbean
forests are the palms. A characteristic portion of the forest referred
to occurs in Cuba, where, as is stated by R. T. Hill in his recently
published and attractive book descriptive of the West Indies,
there are some 26 species of palms, which give variety and beauty to the
scenery of the "Pearl of the Antilles," as well as shade and food to its
inhabitants. At the head of these for height and grace of form stands
the royal palm, which might well be chosen for the emblem of the fair
island it adorns. The wide-spreading crown of glossy pinnate leaves of
this species is borne on a spindle-shaped stem of tough fibrous wood--so
strong and pliant that it defies even the hurricane--in many instances
150 feet above the ground. The tree is a marvel of beauty and
elasticity, and, fortunately for Cuba, is one of the most abundant of
the larger trees on the island. It is met with almost everywhere; in the
centre of broad pasture-lands it often stands alone, tall and straight,
while bordering the cultivated fields of the rich planter it forms a
shady avenue to his dwelling. This well-named _royal palm_ has also been
called the _blessed tree_, for every part of it has its usefulness to
mankind. Certain medicinal qualities are claimed for its roots; the
outer portion of its trunk is easily split into boards for use in making
houses and furniture for the poorer people; in the centre of the cluster
of young leaves at the summit is a tender substance which is eaten raw,
or cooked as a vegetable, or preserved with sugar as a table delicacy.
The broadened leaf-stalks where they leave the main stem form a
sheath-like expansion resembling a thin board, often four to six feet
long, which is made to serve a variety of purposes, such as plates, and
when soaked in water becomes pliable and may be fashioned into baskets
and dishes for cooking, and at the same time furnishes salt for the
seasoning of the boiling vegetables or meat.
The world-encircling cocoanut-palm is found about the shore of tropical
North America, and there, as elsewhere, serves a great variety of uses,
being a greater blessing, especially to the natives and the poorer
descendants of European and African immigrants, than even the royal
palm. The economic importance of its wood-fibres, leaves, and fruit are
too well known to require re-enumeration.
While the wealth of palms is confined to the hot, moist regions
of Mexico, Central America, and the West Indies, several members of the
same great family are found in the United States. The royal palm is
native to southern Florida, while the low fan-palms cover much of the
northern portion of the same State, and occur even about the Ozark Hills
in Arkansas, and the palmetto, growing to be a stately tree, is found
near the coast in the Carolinas and is the emblem of South Carolina, the
"Palmetto State."
The ferns, although abundant, especially in moist woods from Alaska
southward, throughout the continent, reach their greatest variety and
richest luxuriance in the West Indies and Central America, where the
graceful and most artistically beautiful tree-ferns add an indescribable
charm to the always varied foliage. The tree-ferns grow farther up the
mountains of the torrid zone than do the larger palms (in the same
manner that the smaller ferns extend much farther north than the most
hardy palmettoes), and form a conspicuous feature in the foreground of
nearly every wide-reaching prospect in the more elevated portions of the
West Indies, Central America, and south-central Mexico.
In addition to the palms and ferns, the tropical forests of North
America contain a large number of trees of great economic importance.
Chief among these are the mahogany, which is native to the lands
bordering the Caribbean Sea and Gulf of Mexico, and reaches the largest
size and produces the most beautiful and most highly prized wood on
Cuba, Haiti, the Bahamas, and Jamaica. As is well known, this hard,
dark, heavy, fine-grained, and exceedingly durable wood has been used
for the best grades of cabinet-work for about two centuries, and is
still unsurpassed for the beauty of its grain, susceptibility of a high
polish, and the several ways in which it is adapted for the carver's
tool. On account of the great and long-continued demand for its wood it
has become scarce in all but the most inaccessible localities. When
allowed to reach full maturity it is a large, wide-spreading tree with
numerous branches, looking not unlike a giant oak, but has pinnate
leaves and small, although somewhat conspicuous, white flowers.
Another gift of the tropical forest is the lignum-vitæ, which furnishes
the exceedingly tough, hard, resinous wood preferred above all others
for the making of pulleys, mallets, etc. Many other highly prized woods,
not known, however, by familiar names, are also found in the varied
forests of tropical America, as well as numerous vegetable dyes, such as
logwood, brazil-wood, indigo, etc.
The lands of the Caribbean-Gulf region are credited with having
introduced to civilized man the potato, Indian corn (maize), and
tobacco, although the home of the former is probably in the Andean
portion of South America. Indian corn grows luxuriantly not only in the
hot lowlands of Mexico, but on the border of the central table-land of
that republic, where it is supposed to be indigenous, and has now become
one of the leading crops of temperate North America, and is cultivated
in many other portions of the world. Tobacco was found under cultivation
in Mexico at the time of the first coming of Europeans, and retains for
its familiar name the appellation of the district where it was first
seen. From Mexico also come the dahlia and the giant sunflower, as well
as the various species of aloes and cacti now so common in gardens and
conservatories the world over.
Of all the plants, excepting Indian corn and the potato, which are
native to the region under review, none has proved such an unalloyed
blessing to civilized man as the cacao-tree. As this tree is unfamiliar
to most residents of temperate lands, it may not be unprofitable to
transcribe in part a description of it from Rhind's Vegetable Kingdom.
The tree is very handsome, from 12 to 16 feet high, with an upright
trunk some 5 feet high; the leaves are lanceolate, with entire margins,
and of a bright-green colour; the flowers are inconspicuous, reddish,
with yellowish sepals; the fruit, attached by short stems to both trunk
and branches, has a yellowish and reddish colour, oblong, about 3 inches
in length, and consists of a fleshy rind, half an inch thick, containing
a white pulp in which are imbedded about 25 seeds. The seeds, when
roasted, freed from their husks, and ground, furnish the chocolate so
extensively used, especially in France and Spain and in the
former Spanish colonies, and is increasing in favour among
English-speaking people.
Vanilla, which is used in flavouring chocolate as well as many other
dishes, was also found in use among the Aztecs at the time of the
Spanish conquest. The vanilla-plant is a climbing vine, with lanceolate
leaves 18 inches or more in length, and produces a pod containing
bean-like seeds. The pods and seeds when properly dried furnish the
flavouring extract of commerce.
Although the trees which yield rubber in America, as well as the
cinchona, from the bark of which quinine is obtained, are justly to be
accredited to South America, yet certain varieties of these useful
plants occur in Central America and are under cultivation as far
northward as central Mexico.
A more detailed account of the plants of great utility in one direction
or another native to the tropical forests, should include plantains,
bananas, and yams, the wide distribution of which, largely by human
agency, throughout the torrid zone is well known. The delicious
pineapple is native to the Caribbean region, and was found in the
markets of the Aztecs by the early Spanish invaders, although perhaps
indigenous to other lands as well. In Mexico especially, but on the
borders of the tropical forest and in the drier interior, grows the
agave, from which the national beverage, _pulque_, is obtained, and
another species of the same peculiarly American family of plants
supplies great quantities of the tough fibre known as sisal or henequen
hemp, particularly on the stony, arid portions of the peninsula of
Yucatan. Of interest to children especially is the fact that Mexico
exports some 3,000,000 pounds of chewing-gum each year, which is
obtained from a plant there growing wild. To this list of indigenous
products may be added ginger, arrowroot, etc., as well as many fruits
scarcely known outside the tropics, such as the mango, alligator-pear,
breadfruit, and numerous others. This hasty enumeration might be greatly
extended or presented in more detail, but probably enough has been said
to indicate the great and probably as yet but partially
determined economic importance of the vegetable products of the torrid
portion of North America.
Associated with the tropical forest, but thriving best in an advanced
skirmish-line about its drier inland borders, is a group of plants
indigenous to the two Americas--the strangely shaped and spinous cacti.
One of these, the prickly-pear, as it is termed on account of its
pear-like edible fruit, is the emblem of Mexico. A fit legend to place
about this unique heraldic design would be the motto inscribed on the
rattlesnake flag of colonial days in America, "Don't tread on me," as
every one will appreciate who has travelled in the southwestern portion
of the United States or in the upland regions of Mexico.
The cacti extend from South America northward through the lands
bordering the Caribbean Sea and Gulf of Mexico, and east of the
Mississippi are represented by a single genus, _Opuntia_--the
prickly-pear, or Indian fig, as it is often termed--which grows in dry
situations as far north as Massachusetts and Michigan. In the Great
Basin several genera of cacti are plentiful, especially on dry, stony
uplands, and two species reach as far northward as the Canadian
boundary. Although the cacti tribe is widely distributed, the region
where it presents the greatest variety and the largest individuals is in
the dry, semi-desert portions of Arizona and the table-lands of central
Mexico. It is most at home on sterile, rocky ridges and amid bare cliffs
where there appears to be but little soil, but the strong roots strike
deep into the earth in search of moisture. The cacti present great
diversity of form and an indefinite differentiation of stem and leaf. In
fact, there are no easily recognised leaves in the ordinary sense of the
term, but the fluted and jointed stems perform the function of foliage.
The plants are economical of moisture, and not only present a minimum of
surface for evaporation or transpiration, but their epidermal tissues
are for the most part without pores, thus retarding the escape of the
moisture drawn from the seemingly dry soil.
In size and shape the cacti present great variety, ranging
through all gradations from the thick, strongly jointed, pad-like
expansions of the prickly-pear, a few inches high, growing in widely
extended clusters and massive globular forms, looking not unlike spiny
melons, 2 or 3 feet or more in diameter, to jointed and fluted columns,
bristling with sharp spines, the largest of which, known as the
candelabrum cactus, attains a height of from 40 to 60 feet. In this the
largest of all the cacti, which is not uncommon in Arizona and adjacent
portions of Mexico, the central upright stem, frequently 20 inches or
more in diameter, sends out from 1 to perhaps 7 or 8 club-shaped
branches, which leave the parent stem nearly at right angles, but soon
bend upward and become parallel with the central stalk, which they
frequently surpass in height, their form thus suggesting a branching
candlestick or candelabrum.
In spite of the bizarre and frequently repellent appearance of the cacti
as seen under cultivation, in their barren homes they are in harmony
with their surroundings, and add a characteristic, and even beautiful
element to the scenery of the parched and generally desolate valleys and
rocky slopes where they thrive best. Their blossoms are large, usually
either white or brilliantly coloured, and expand in the hot, dry air,
fully exposed to the intense sunlight, and present a freshness and
vigour which tell of the abundant store of moisture within the thick
rind inclosing their stems. The showy flowers are borne close to the
body of the plant or at the ends or edges of the inflated pad-like
leaves, and are scentless, except in the case of a few night-blooming
species, and attract insects from afar by reason of the conspicuousness
of their widely expanded corollas. The fruits also are usually
conspicuous, and present many rich tints of red and yellow, which at a
little distance give them the appearance of flowers. The fruit of
several species are edible, and even delicious, especially when gathered
fresh from the thorny stems and eaten on the desert, perhaps many miles
from the nearest spring or stream. One species of cactus growing
abundantly in Mexico and known as the cochineal-fig, is inhabited by the
cochineal-insect, from which the highly prized dye of that name is
obtained.
A companion of the cacti in the arid region where they flourish best is
the yucca, or Spanish bayonet, which sometimes attains the size of small
trees and throws out several branches. Its leaves are stiff,
thick-stemmed, and each one terminated by a sharp spine, as is well
known from the many examples to be seen under cultivation in Europe and
America. The flowers are white and borne in luxuriant showy spikes a
foot or two in length, and sometimes give to dry, rocky slopes the
appearance of a luxuriant garden.
The cacti, yuccas, and associated plants of the most arid portions of
the continent stand far apart, without mutual support or shelter, and
find protection in their spines, thick rinds, and frequently acrid
juices. Their colours are usually neutral, grayish green, rendered still
more inconspicuous by the dust that settles on them, but their flowers
are as a rule conspicuous, thus serving to attract pollen-bearing
insects, and their fruits are in many instances brightly coloured, and
furnish food for birds and other animals, which assist in the
distribution of their seeds.
_The Atlantic Forest._--The originally forest-covered eastern portion of
North America, referred to under the term Atlantic forest, embraces the
region from the eastern coast of the continent inland across the
Appalachian Mountains and interior Continental basin to the eastern
border of the prairies or plains; its southern limit, in a general way,
is the coast-line of the Gulf of Mexico, but the arbitrary boundary,
dividing it from the tropical forest, crosses the southern portion of
Florida, and at the extreme southwest is drawn at the Rio Grande. The
northern boundary of the Atlantic forest is also an arbitrary line, and
follows the fiftieth parallel of latitude from the mouth of the St.
Lawrence westward to the region about the Lake of the Woods; along this
boundary the varied Atlantic forest merges with the monotonous and
mostly coniferous subarctic forest. The region thus roughly outlined
comprises over 2,000,000 square miles, and was at the time of the first
coming of white men to America almost completely forest-covered, but the
natural conditions are now profoundly modified, and to a great extent
the trees have been cut or burned, and the land they shaded
converted into cultivated fields.
The Atlantic forest as a whole has two leading characteristics, the
first being the great variety and frequently large size of the deciduous
trees--that is, of broad-leaved trees, such as the oak, hickory, elm,
maple, chestnut, etc., which drop their ripe leaves each fall and renew
them the following spring--and the second, the intermingling of the
trees of the class just mentioned with the coniferous trees, such as the
pine, spruce, tamarack, etc., which have narrow, needle-shaped leaves
and are usually designated as evergreens. While these general statements
are sufficiently accurate for our present purpose, it is to be
remembered that some of the broad-leaved trees (_Angiosperms_) are
evergreen, especially in the southern portion of the Atlantic forest,
as, for example, some of the oaks, the magnolias, the holly, etc.; while
at the north, certain of the conifers (_Gymnosperms_) shed their leaves
each fall, as is conspicuously illustrated by the yellow of the tamarack
or larch forests of the northeastern portion of the United States and
eastern Canada, in November, and the bright green of the same trees in
May of each year. It is in the intermediate temperate region, between
the mostly evergreen coniferous subarctic forests and the mostly
evergreen broad-leaved trees of the Caribbean forest, that the wonderful
transformation in the colours of the mountains and plains each autumn
becomes the most conspicuous feature in the annual round of seasonal
changes as expressed by the vegetation.
Of the two classes of forest-trees, represented by the oak and the pine,
which are intermingled and struggle with each other for supremacy in the
Atlantic forest, it is difficult to say which is the more beautiful or
which is of the greater service to man. The broad-leaved trees give us
our hardwoods, used extensively for furniture, the interior finish of
buildings, and for the manufacture of tools, farming implements, wagons,
carriages, sleighs, etc. To a great extent it was the availability of
these strong, tough, hard, and durable woods which has made American
tools and implements of such a high grade of excellence that they
are in demand in every civilized country. For example, the American
ax-helve, made of hickory, is almost a work of art, as well as of
utility, and it is prized above all others by foresters the world over.
The same tree has aided no less efficiently in the popularity and
excellence of American carriages and sleighs, the equal of which for
lightness, strength, and durability has not been reached in other
countries. The pines and their near relatives furnish what unfortunately
has been considered an unlimited supply of easily workable lumber,
suitable for building houses, vessels, bridges, and many other purposes.
Of the pine lumber supplied by the Atlantic forest, there are two
principal varieties, the far-famed white pine, furnished by New England,
the Great Lake region, and southeastern Canada, and the yellow pine,
which comes from the South Atlantic and Gulf States.
Of the Angiosperms which reach the dignity of trees, the Atlantic forest
possesses a variety and abundance not exceeded elsewhere in the world.
The most characteristic examples are the maples, elms, oaks, hickories,
walnuts, chestnuts, ashes, basswoods, birches, tulip-trees, magnolias,
liquidambar, tupelos, sycamores, etc., nearly all of which are
represented by a number of species or varieties and vast numbers of
individuals. While this diversity is found throughout the forests of the
east-central part of the continent, certain regions are characterized by
the abundance and large size of the trees belonging to one or to a few
genera, so that a striking change is met with as one travels in any
direction. The maples and elms reach their greatest size and abundance
at the north, especially in New England, and thence westward to the
Mississippi Valley, where they are the favourite shade-trees of villages
and farms. In regions where the forests have been removed choice
specimens of these trees have frequently been saved or subsequently
planted, and standing alone, without competition and fully exposed to
the light, reach great perfection of form and a high degree of beauty.
The oaks are represented by a large number of species and varieties
throughout the entire Atlantic forest, but reach their largest size and
greatest abundance, both of species and individuals, in central
and southern portions of the eastern United States. The same may be said
also of the hickories, except that the maximum in reference to size,
number of species, and abundance is attained in the region of the Ozark
Hills. The tulip-tree, so named from the profusion of showy yellow
blossoms it bears, is large and wide-spreading, with broad, dark-green
leaves, and has the centre of its habitat in Kentucky, where many
magnificent examples occur along the fences separating the broad meadows
and rich pastures of the region of the blue grass, but thrives also from
the Atlantic coast westward to beyond the Mississippi, and from Ontario
on the north nearly to the Gulf of Mexico on the south. Not only is the
tulip-tree an ornament and a blessing on account of its flower-laden
branches and dense shade, but its white, even-grained wood is of great
value.
To give even a list of the deciduous trees which flourish and reach a
high degree of perfection in the Atlantic forest would require far more
space than is at present available. There is one other genus, however,
which cannot be passed by even by a casual observer, and that is the
magnolia, one species of which, the _grandiflora_, is the most
magnificent of all the splendid broad-leaved trees of America. This, the
largest and finest of the several species of its genus found in the
eastern portion of the United States, attains a great size in the
southern Appalachian region, but is best developed in the lower portion
of the Mississippi Valley. It is frequently from 50 to 80 feet or more
in height, wide-spreading, and in many instances upward of 3 feet in
diameter, with dark-green leaves which do not fall in the autumn. In
spring the dark foliage is beautified by cup-shaped blossoms of creamy
whiteness and remarkable fragrance, which measure 3 or 4 inches in
diameter. When the magnolia is in blossom it becomes a centre of
delicious perfume and a colony of insect life. Its wood, although creamy
white and excellent for cabinet-work and interior finish of houses, has
not as yet found favour for these or other purposes.
With the exception of a few species of broad-leaved forest-trees
found in greatest perfection in the northern portion of the Atlantic
forest, they reach their greatest development in size, number of
species, and density of growth in the southern portion of the broad
Mississippi basin, where, in addition to magnolias, the tulip-tree,
etc., chestnuts, hickories, oaks, and many other genera grow side by
side and attain great height and dignity. This is also the centre of
dispersion of the American hawthorns, which reach a size and beauty
unrivalled elsewhere. The Osage orange is peculiar to this region, and
the red cedar (juniper), the most widely distributed of all the American
conifers, and also the yellow or southern pine are there at their best.
Much of this region still retains its primitive wildness.
The great extent of the Atlantic forest in latitude, the topographic
diversity of the region it occupies, and its exposure on the east to
maritime and on the west to continental climatic conditions, have led to
great variations within itself. From the coast of New England westward
and including the entire drainage basin of the St. Lawrence, together
with an extension southward along the Appalachians, the forests are
composed largely and over extensive areas almost wholly of coniferous
trees. This region of northern evergreens contains in its southern
portion sturdy growths of broad-leaved deciduous trees. The spruces, the
most characteristic of the trees of the subarctic region, are present
in abundance on the mountains of New England, and still form a dark
mantle over the Adirondack hills; but on the less elevated lands
adjacent the white pine dominated and outnumbered all its rivals in the
primeval forest.
The white or Weymouth pine, which up to the present time has proved to
be of greater commercial value than any other tree on the continent,
extends westward from southern Newfoundland and the coasts of the
maritime provinces of Canada to Minnesota, and occupies nearly the
entire drainage area of the St. Lawrence, together with an extension
southward along the Appalachians nearly to their southern limit.
The white pine is a large tree for the region in which it grows. Its
height is from 70 to 150 feet, with a diameter at the base of from 3 to
9 feet. It thrives best on sandy soil and hills of glacial drift, and
endures a severe winter climate, as well as the frequently
long-continued droughts of the hot summers. Its wood is soft, compact,
with an even, straight grain, and is not conspicuously resinous. The
sap-wood is nearly white and the heart of a light brown, slightly tinged
with red; it is easily worked and susceptible of a good polish; it is
more extensively used for boards, shingles, etc., than any other wood in
the eastern portion of the continent, and is in demand also for
cabinet-work, the interior finish of buildings, ship-building, and many
other purposes.
The southern pine--known also as the "long-leaved pine"; "Georgia pine,"
for the reason that the lumber derived from it was first extensively
shipped from that State; "yellow pine," in reference to the golden
colour of its wood; and "hard pine," in distinction from the softer
white pine--is another valuable species. The tree with these several
synonyms, of which the term _southern pine_ will here be used, forms
open forests with but scanty undergrowth, over a region extending from
near the Atlantic coast in the Carolinas and Florida, westward to the
delta region of the Mississippi, and reappears again to the southward of
the Ozark Hills. Although not so large, and to many admirers of
beautiful trees not so picturesque or pleasing as its relative in the
more rigorous climate of the St. Lawrence basin, the southern pine,
growing within the reach of the moist, warm winds from the Atlantic and
Gulf of Mexico, is still an attractive tree, especially when young and
when freedom is afforded to expand its boughs. It is seldom over 100
feet high, and as cut for lumber has on an average a diameter of about 2
feet at the base, although individuals measuring 3 or 4 feet in diameter
are not rare in certain favoured areas. It grows best on dry, sandy
soil, outside the flood-plains of streams, where it forms monotonous
forests, with but few intergrowths of other trees. The wood is heavy,
hard, strong, durable, coarse-grained, very resinous, and of many
shades of brown and yellow. When sawed into lumber, it serves a wide
range of uses, more especially for the frames of buildings and ships,
and for the floors and interior finish of houses.
Next to the southern pine, the most characteristic tree of the Atlantic
coastal plain southward from Virginia and westward through the Gulf
States, is the cypress, also a conifer, but, like the tamarack, sheds
its leaves in the autumn. The cypress grows especially in swampy
localities, and has a widely expanded base, suitable for support on
marshy soil, and reaches a large girth, although seldom over 75 feet
high. Aged and most picturesque examples are growing in isolated
positions in Lake Drummond, the central water body of the Dismal Swamp,
and in many other similar situations in the belt of low country fringing
the borders of the Atlantic and Gulf of Mexico. Its wood is used for
most of the purposes for which the southern pine is employed, and now
that the white pine is approaching extinction, is to a considerable
extent supplying the demand for cabinet-wood.
In glancing at the larger and most numerous trees of the Atlantic
forest, and those of greatest utility, we should not neglect the humbler
plants, usually of little, if any, purely commercial value, but
priceless on account of their beauty and the fragrance of their flowers,
which grow beneath the shade of their larger and more stately associates
or are content to possess the local areas, perhaps high on the
mountains, where the conditions of climate or soil are unfavourable for
the growth of large trees. Throughout the eastern portion of the United
States, but more especially on the slopes and summit portions of the
Appalachians, there are many species of azalea, laurel, rhododendron,
etc., which grow luxuriantly and in spring and early summer furnish a
wealth of bloom that is scarcely rivalled elsewhere on the continent. In
this same region also, but extending westward to Michigan and Minnesota,
and even to eastern Nebraska, grows the redbud or Judas-tree, which each
May becomes as thickly set throughout all its branches with small
crimson blossoms as are the tree-like coral in tropical seas with
expanded polyps. This beautiful tree of low growth many times gives to
the mountains of Virginia, when seen from a distance, a delicate blush
like that which the osiers earlier in the spring impart to the marshy
vales and river-banks. A companion of the redbud, but far more widely
distributed, is the dogwood or cornel, of several species, the most
conspicuous of which, and in the Appalachian region the most common, is
the flowering dogwood. In May and June this species puts out a profusion
of clusters of small greenish flowers, each of which is surrounded by a
broadly expanded and very showy corolla-like involucre, composed of four
white or pinkish inversely heart-shaped leaves. When the cornel is at
the height of its spring-time glory it stands forth amid the tender
greens, russets, and pinks of the unfolding leaves of the various trees
and shrubs among which it grows as if the orchards and forests had been
commingled by some fairy gardener. In autumn the cornel again becomes
conspicuous in the woodlands by reason of its clusters of coral-red
fruit.
In the splendid Atlantic forests, with their marvellous intermingling of
shining pine-needles, broad, swaying leaves, and many-coloured trunks,
there are also vines and creepers sometimes forming impenetrable
tangles, as where the broad leaves of the wild grape grow in pendent
sheets of green from supporting trees, or the jessamine fills the air
with fragrance. Of the many vines which entwine the trunks of trees,
mantle the rocks, and quickly claim abandoned fields, especially in
Virginia and neighbouring States to the southward, none is more
beautiful or more highly prized for the charm it adds alike to fields,
fences, and forests than the familiar Virginia creeper. The glory of
this widely distributed vine comes in the autumn when its leaves change
from green to the most brilliant scarlet. During the season of harvest
also, when the trees are arrayed in their greatest splendour, the ground
is yellow with golden-rods or purple with asters. This annual carnival
of colour embraces the entire Atlantic forest, but is most
resplendent in the region of the Hudson and St. Lawrence. A charming
little denizen of the Atlantic forest is the lowly and humble arbutus,
or Mayflower, which springs up through the dead leaves carpeting the
ground in early spring, and fills the air with its delicious perfume.
The Mayflower is a trailing plant, but a few inches high, with rounded
or oval leaves, which remain green all winter and furnish a pleasing
setting for the small pink or rose-coloured blossoms, which appear in
early spring even before the snow has melted. It reaches great
perfection beneath the pines of New England and about the Laurentian
lakes, but extends far southward along the Appalachians, where elevation
gives conditions similar to those of the lower region at the north.
The Atlantic forest reaches its western limit in the Mississippi basin
(Fig. 28), and is succeeded westward by treeless prairies, which merge
along their western margins with the drier and less completely
grass-covered high plains adjacent to the east base of the Rocky
Mountains. The forest does not terminate abruptly, as on the border of a
cleared field, but by gradual transitions. As its western limit is
approached, a change in the species is noted, trees which thrive on
uplands and can sustain long-continued summer drought replacing the
species best adapted for more humid conditions. The forest is most
extended, however, along the streams where white-trunked cottonwoods,
frequently of great size, with widely spreading branches, extend even
into the region of the great plateaus. Much of the prairie region in
Illinois, Iowa, etc., was originally nearly surrounded by forest
growths. The natural condition of the prairies and higher plains
adjacent to them on the west and the reason for the limits set to the
western extension of the Atlantic forest will be considered later under
the heading _Prairies and Plateaus_.
_The Boreal Forest._--From Nova Scotia, Newfoundland, and Labrador a
forest composed mainly of a few species of coniferous trees extends
westward, and after passing the southern extremity of Hudson Bay, is
prolonged northwestward across the continent and in the region of
the mouth of the Mackenzie nearly to the shore of the Arctic Ocean. It
extends also through central Alaska to within about 100 miles of the
border of Bering Sea. This vast transverse forest belt which unites the
northern extremity of the Atlantic forest with the northern portion of
the Pacific forest is over 3,000 miles long from southeast to northwest,
and on an average fully 600 miles wide. On the north, more especially in
arctic Canada and as it approaches the shore of Bering Sea, it thins
out, owing to the severity of the winter climate, the trees become
dwarfed and stunted in much the same way as the trees adjacent to the
timber-line on high mountains, and is succeeded by the broad treeless
plains of the Barren Grounds and tundra. Along its south-central border
its extension is again limited by climatic conditions, principally the
dryness of the hot summers. The trees are there scattered or form
isolated groves to the south of the general forest boundary, and are
finally succeeded by the treeless prairies and interior plains and
plateaus. On the east the great northern forest merges with the pine of
the northern portion of the Atlantic forest, and in a similar way at the
northwest passes by insensible gradations into the north extension of
the coniferous forest growing on the Pacific mountains. In each of the
instances there is no well-defined boundary between the east and west
belt of northern forests and the north and south forest belts adjacent
to the Atlantic and Pacific.
The boreal forest presents a striking contrast to the forests of the
torrid zone and to the greater portion of the forests of temperate
regions in the fact that it is composed of but a few species of trees.
Monotony which becomes oppressive to one who lingers long in its sombre
shade is its most conspicuous characteristic. In the main it is composed
of but eight species of trees, namely, white and black spruce, larch or
tamarack, canoe-birch, balsam-poplar, aspen, balsam-fir, and the gray
pine. Of these the spruces are the most abundant and most characteristic
as well as the most northern trees of the continent. They
frequently reach sufficient size to make them available for building log
houses and for lumber.
Four of the species mentioned above, namely, the white spruce,
canoe-birch, balsam-poplar, and aspen, cross the entire breadth of the
continent from Labrador to Alaska, but the pines and firs in the east
and the west are of different species. The larch or tamarack, which
forms such an important feature of the forest in eastern Canada and
about the Laurentian lakes, extends westward to beyond Hudson Bay, but
is represented by other species in the Mackenzie and Yukon basins, and
in the northern portion of the Pacific mountains. The region occupied by
the great northern forest is interspersed with lakes, some of them of
large size, and by innumerable swamps. The spruces and the gray pine
grow on the uplands between the lakes and swamps, while the cold, wet
bottom-lands are occupied by poplars, dwarf birches, willows, and
alders. In the north, near where the forest breaks into outstanding
groves and finally gives place to grassy hills, as along the Porcupine
River in Alaska, the foliage in the lowlands becomes golden in autumn
and forms irregular, far-reaching avenues of brilliant colour separating
the hills, which are black with spruce-trees or shimmer with the soft
gray tints of ripened grasses. There is much that is beautiful and even
lovely along the poleward border of the great forest, but within its
deeper recesses the ground is covered with mosses and lichens, and the
stiff, sombre trees have a monotonous similarity and unbending rigidity.
In spite of the great area covered by the boreal forest, it being one of
the greatest, if not the most widely extended continuous growth of
arboreal vegetation in the world, it is of comparatively small economic
importance. Even if the trees were within the reach of a market, their
wood is of inferior quality and not generally suitable for lumber. A
modern industry has been developed, however, which may bring it into
demand, namely, the manufacture of wood-pulp, so largely employed in the
making of paper and for other purposes.
_The Pacific Forest._--In the northern portion of the Rocky Mountain
region in Canada and Alaska the boreal forest, as already stated, merges
by insensible gradations with the forests occupying the Pacific
mountains from Alaska southward to Mexico. The junction line between the
two is irregular, and what are essentially outliers of the more northern
forest occupy the higher portions of the mountains in the western
portion of the United States.
The Pacific forest begins at the north near Mount St. Elias, and at
first occurs on isolated areas separated by ice-fields and inland
reaches of the ocean, but in southeastern Alaska and on the numerous
islands adjacent becomes more continuous and extends eastward far into
British Columbia. As the timber-line in that region has an elevation of
but 2,500 feet at the extreme western extension of the forest, although
gradually rising southward, large portions of the mountains are treeless
and barren. In the United States, on account of increasing dryness of
the valleys from north to south, the forest becomes broken into many
detached portions, which occupy the mountains and higher plateaus and in
general are restricted to higher and higher locations with decrease in
latitude. This distribution illustrates in a striking manner the
dependence of trees on humidity. The forest is densest and the trees in
general of greatest size and occur at the lowest elevations on the
northwest portion of the Pacific coastal region, where the rainfall is
excessive and distributed practically throughout the entire year. The
Coast Ranges from Alaska southward to central California, as well as the
Cascade Mountains and Sierra Nevada, are tree-clothed. In the interior,
and especially in the central and southern portion of the Pacific
cordillera, where the valleys are hot and dry in summer, trees are
absent, and even the borders of the rivers in many instances without
shade. In Canada the trees frequently extend across the lowlands, but in
Montana and Idaho the valleys resemble the treeless plains to the east
of the Rocky Mountains, while the uplands and the lower mountain slopes
are dark with firs and pines. Above the forest rise the barren and
frequently perpetually snow-covered summit-peaks and ridges. In
the Great Basin region, and from there southward, many of the mountains
are practically destitute of trees from base to summit.
So vast is the region occupied by the Pacific forest and so varied the
conditions dependent upon climate, soil, and elevation which influence
its growth, that great variations in the genera and species of trees
composing it are to be expected. This prediction is soon verified when
one travels through the forest. The extremes may be indicated briefly by
referring to the fact that at the north the trees are mainly spruces,
firs, and cedars, and at the south include the giant cactus, arboreal
yucca, and the fan-leafed palm. In its medial division are the great
forests of western Washington and Oregon, composed mainly of firs and
cedars, and the no less magnificent forests of redwood-trees on the
Coast Ranges of northern California and the west slope of the Sierra
Nevada. Like the boreal forest, the one under consideration is largely
composed of coniferous trees, although in the valley, and especially
along the borders of streams in southern Canada, Washington, etc., a few
species of broad-leaved trees, such as the maple, cottonwood, ash, and
alder, thrive in close association with dark conifers; while in similar
situations farther south oaks growing in scattered groves give a
park-like character to the land, as in the southern portion of
California.
In contrast with the Atlantic region, the western portion of the
continental forest belt is singularly lacking in broad-leaved trees, and
such as are found are usually of small size and but little economic
importance. This lack, however, is perhaps more than counterbalanced by
the number both of individuals and of species and the great size and
magnificence of the conifers.
One of the densest and in many ways most thoroughly representative
portions of the Pacific forest where it occupies an excessively humid
region occurs on the west side of the Cascade Mountains in Washington,
inclusive of the Puget Sound basin and the region to the westward from
which rise the Olympic Mountains.
In western Washington the forest is composed mainly, and, in
fact, over large areas, almost entirely of two species of trees, namely,
the red fir and the red cedar, each of which attains gigantic
dimensions. Of these two species, the first is the more common, the
larger, and by far the more important from a commercial point of view.
It frequently, and, in fact, commonly, attains a height of from 200 to
300 feet, with a diameter at the base of from 8 to 10 or more feet. Not
only do these magnificent trees reach such great dimensions, but they
are thickly set over hundreds of square miles of territory. In thousands
of instances the great trunks sheathed in rough thick bark rise straight
and massive, with but a slight decrease in diameter, to a height of
upward of 80 feet before the first branch is given off. The cedars, the
intimate companions of the great firs, are of equally gigantic girth at
the base, but taper rapidly to spire-like summits, usually from 100 to
150 feet above the ground, and are thickly set with small branches
throughout. They flourish best in excessively moist situations and reach
far up the mountains, particularly along the numerous watercourses;
while the firs, although perhaps most at home on the less thoroughly
water-soaked uplands, thrive on the banks of streams, the sides and
summits of hills, and on steep mountainsides alike.
Mere enumeration of the number and size of the trees, however, fails to
give an adequate impression of the astonishing magnificence of the
wonderful forest of the Puget Sound region. Its grandeur is beyond
description, and can only be fully appreciated by one who abides for
weeks or months in its perpetual twilight. The great trees, shaggy with
mosses and lichens of innumerable tints of brown, green, and yellow, do
not form detached groves, as is so frequently the case in less humid
lands, but are thickly set for mile after mile and league after league,
as one threads his difficult way beneath them. So vast is the forest
that a person travelling through it soon becomes impressed with the idea
that it is interminable. Beneath the deep shade of the lofty boughs
there is a rank undergrowth of young firs, cedars, and hemlocks, while
in the valleys especially, and on the frequently inundated
flood-plains of the streams, there is usually a tangled growth of
vine-like maples, alders, elders, yews, etc. In this lower forest the
most conspicuous and frequently too abundant plant is the broad-leaved
and excessively spiny devil's-club, the foliage of which changes to
brilliant yellow in the early autumn, and forms a most artistic setting
for the spikes of crimson fruit borne at the extremities of the
upward-bending ends of the usually prostrate stems.
[Illustration: FIG. 29.--Douglas Firs, Vancouver, B. C.]
Of still more lowly habits are the ferns, mosses, and lichens which form
a thick, luxuriant, and ever-varied carpet over the black humus soil
beneath. The ground throughout the forest is encumbered with fallen
trunks, sometimes piled one on another to the depth of 20 or 30 feet,
which, owing to the continuous moisture, remain undecayed for centuries.
Not infrequently a massive cedar or fir, in size and shape not unlike a
prostrate column of some great temple, supports three or more trees,
each large enough to be cut for lumber, whose gnarled and twisted roots
clasp the sides of their host and descend to the earth beneath. The
beauty of these fallen giants when overgrown with thick layers of
variegated moss and exquisitely decorated with hundreds of small
hemlocks and a multitude of gracefully bending fern-fronds, always fresh
in colour and usually beaded with moisture, is beyond the power of the
most skilful artist to adequately portray. The fascination of the
great forest is such that the explorer, although perhaps weary with
forcing a passage through the dense undergrowths and climbing over
prostrate trunks, is lured by its charms into more and more inaccessible
retreats probably never before invaded by man, but at last finding that
the wonderland has no attainable limits, is content to rest on some
inviting couch of golden-tinted lichens and study the varied charms and
endless details of the dream-like picture surrounding him.
From a commercial point of view the forest of the Puget Sound region is
of immense importance. Lumber industries have been established there,
with the most improved appliances for cutting trees, transporting the
logs to mills, and sawing them into lumber, much of which is loaded on
ships and widely distributed. So vast is the forest, however, that as
yet the natural conditions are but slightly changed, except in the
immediate vicinity of tide-water, but the destruction from axe and fire
has only been begun; the waste that, no doubt, is to continue is most
disheartening.
Another centre in the vast and locally differentiated Pacific forest, as
typical in its way as are the dense growths of fir and cedar just
referred to, occurs on the Coast Range of north California, where the
redwood (_Sequoia sempervirens_) is the all-important and characteristic
tree. This redwood forest begins at the south in the vicinity of San
Francisco, and extends northward, mainly on the moist seaward slopes of
the Coast Ranges, to southwestern Oregon, but seldom reaches more than
30 miles inland.
[Illustration: FIG. 30.--Redwood Forest, California.]
The redwood resembles the cedar in habit, general appearance, character
of its wood, and colour of bark and leaves. It flourishes best in moist
localities, and attains a great size, surpassing in height and diameter
of stem even the giant firs of Washington, and is only exceeded on this
continent by its cousin, the great sequoia (_Sequoia gigantea_) of the
western slope of the Sierra Nevada, in south-central California. It
frequently attains a height of 300 or more feet, with a diameter at the
base of 15 or 16, and in certain exceptional instances of over 20 feet.
It rarely branches low, but almost invariably has a straight,
fluted stem, perfectly symmetrical, rising with a slight taper for about
200 feet to the first limb. The foliage is dull green in colour, fine,
and drooping. It is a most beautiful tree both in form and colour, and
is markedly gregarious in habit. As stated by Henry Gannett, it forms
the densest forest known if the comparison is made on the basis of the
amount of merchantable lumber growing on a given unit of area. For
example, the yellow-pine forests of the Southern Atlantic and Gulf
States contain on an average about 5,000 feet, board measure (square
feet of boards an inch thick), of timber per acre, and in the moderately
dense portion of the white-pine forests of the Great Lakes region the
average is about the same. In each of these regions, famed for their
lumber, a tract containing 10,000 feet of lumber per acre would be
considered as heavily forested. In the redwood forests of California,
however, 50,000 feet of lumber per acre is not rare over extensive
areas, while for special tracts containing many square miles this
estimate may safely be doubled. Upon 96,443 acres in Humboldt County,
California, the average amount of lumber contained in the trees still
standing is 84,000 feet per acre. The returns of lumber companies during
a continuous period of ten years from tracts which have been cleared
show a return of 75,000 to 100,000 feet per acre, but even this is not
the maximum. A certain tract of several square miles actually yielded
150,000 feet per acre; and there is on record a yield of 1,431,530 feet
from a single acre. One tree is said to have furnished 66,500 feet of
lumber, and another, 15 feet in diameter at the base, contained
100,000 feet. Another tree, still standing, measures 22 feet in
diameter, and it is estimated will yield 200,000 square feet of boards
an inch thick.
The wood of the redwood-tree is of a clear red colour with the exception
of a thin layer just under the bark, which is almost pure white, and is
light, soft, coarse-grained, and susceptible of a high polish. It is the
most common and most valuable of all the forest products of the Pacific
coast of North America, and is serviceable for a great variety of
purposes.
The celebrated "big trees" of California are not to be confounded with
the redwood described above, but belong to a different species of the
same genus. The big trees are worthy of their name, as they are by far
the largest in North America. When full-grown they average about 275
feet in height, with a diameter near the ground of about 20 feet. One of
the tallest as yet measured has a height of 325 feet, and the largest a
diameter of 35 feet 8 inches inside the bark and 4 feet above the
ground. The age of one of these giants, as shown by the number of rings
of growth in its trunk, is about thirteen hundred years; another, 24
feet in diameter, is twenty-two hundred years old; and a third showed
over four thousand rings of growth, and must have been in its prime at
the time of the birth of Christ. The trees occur in detached groves on
the western slope of the Sierra Nevada in south-central California, but
become more common southward, where they form a genuine forest belt.
Their range from north to south is about 260 miles, and their elevation
above the sea from 6,000 to 8,000 feet.
"So exquisitely harmonious," says John Muir, in his charming book The
Mountains of California, "and finely balanced are even the very
mightiest of these monarchs of the woods in all their proportions and
circumstances, that there is never anything overgrown or monstrous about
them. On coming in sight of them for the first time, you are likely to
say, 'Oh, see what beautiful, noble-looking trees are towering there
among the firs and pines!' their grandeur being in the meantime in great
part invisible, but to the living eye it will be manifest sooner
or later, stealing slowly on the senses like the grandeur of Niagara or
the lofty Yosemite domes. Their great size is hidden from the
inexperienced observer as long as they are seen at a distance in one
harmonious view. When, however, you approach them and walk around them,
you begin to wonder at their colossal size and seek a measuring-rod.
These giants bulge considerably at the base, but not more than is
required for beauty and safety; and the only reason that this bulging
seems in some cases excessive is that only a comparatively small section
of the shaft is seen at once in near views. One that I measured in the
King's River forest was 25 feet in diameter at the ground and 10 feet in
diameter 200 feet above the ground, showing that the taper of the trunk
as a whole is charmingly fine. And when you stand back far enough to see
the massive columns from the swelling instep to the lofty summit
dissolving in a dome of verdure, you rejoice in the unrivalled display
of combined grandeur and beauty. About 100 feet or more of the trunk is
usually branchless, but its massive simplicity is relieved by the bark
furrows, which, instead of making an irregular network, run evenly
parallel, like the fluting of an architectural column, and to some
extent by tufts of slender sprays that wave lightly in the winds and
cast flecks of shade, seeming to have been pinned on here and there for
the sake of beauty only. The young trees have slender simple branches
down to the ground, put on with strict regularity, sharply aspiring at
the top, horizontal about half-way down, and drooping in handsome curves
at the base. By the time the sapling is five or six hundred years old
this spiry, feathery, juvenile habit merges into a firm, rounded dome
form of middle age, which in turn takes on the eccentric picturesqueness
of old age. No other tree in the Sierra forest has foliage so densely
massed or presents outlines so firmly drawn and so steadily subordinate
to a special type.... The foliage of the saplings is dark bluish green
in colour, while the older trees ripen to a warm brownish-yellow tint,
like _Libocedrus_. The bark is rich crimson brown, purplish in
young trees and in shady portions of the old, while the ground is
covered with brown leaves and burrs forming colour masses of
extraordinary richness, not to mention the flowers and underbrush that
rejoice about them in their season. Walk in the sequoia woods at any
time of year, and you will say they are the most beautiful and majestic
on earth. Beautiful and impressive contrasts meet you everywhere; the
colours of tree and flowers, rock and sky, light and shade, strength and
frailty, endurance and evanescence, tangles of supple hazel-bushes, tree
pillars about as rigid as granite domes, roses and violets the smallest
of their kind, blooming around the feet of the giants. Then in winter
the trees themselves break forth in bloom, myriads of small four-sided
staminate cones crowd the ends of the slender sprays, colouring the
whole tree, and when ripe dusting the air and ground with golden
pollen."
Owing to the remoteness of the big trees from commercial centres, they
have escaped to a great extent the destruction which everywhere attends
the advent of the white man, and some of the finest groves are now under
state protection.
The sequoias are not only of interest on account of their great size and
grandeur, but from the fact that they are the lingering survivors of an
ancient and once widely distributed genus. During the Cretaceous and
Tertiary divisions of geological history the genus numbered at least 50
species, as has been shown by leaf impressions, fossil wood, and cones
buried in the rocks of New Zealand and Chile on the south, Spitzbergen
and Greenland on the north. Over North America they extend from the
Atlantic to the Pacific. At present the only two species known, both of
which, as already stated, are confined to the Pacific coast, and with
the exception of a slight extension of the less gigantic of the two into
southwestern Oregon, are found only in California.
While the firs, cedars, and redwoods form the major portion of the
forests in the more humid regions on the western side of the continent,
there are two species of pines growing in drier situations which in a
general view are even more characteristic of the Pacific forest
than are the sequoias. These two pines, well worthy to stand side by
side with the giant firs and still more gigantic redwoods, are known as
the sugar-pine and the yellow pine.
The sugar-pine grows amid the mountains from southwestern British
Columbia, southward through western Washington, Oregon, and on the
Sierra Nevada and Coast Ranges of California, at elevations ranging from
4,000 to 8,000 feet. It frequently clothes steep declivities or bids
defiance to the storms on the crests of sharp ridges. In size it is
scarcely exceeded by any of its companions excepting the firs and
sequoias. It frequently attains a height of from 200 to 275 feet, with a
diameter at the base of from 8 to 14, and in some instances of over 20
feet. Individual trees are known which have a height of 245 feet and are
18 feet in diameter. The branches are usually high above the ground and
widely spreading. In the case of well-grown individuals they leave the
main trunk with a sweeping, downward curve, which midway out changes to
an upward curve, and at the extreme distal end droops once more. At the
extremity of many of the far-reaching boughs there are suspended one or
two cones, each 12 or 14 inches long and sometimes over 8 inches in
diameter. The peculiar and frequently remarkably regular curvature of
the great branches, giving them the form of half a Cupid's bow, imparts
to these mighty pines a grace and symmetry possessed by few other trees.
The familiar name of this great pine refers to the fact that from wounds
or incisions in its trunk there exudes a sweet sap which is considered
by many persons to exceed even the sap of the maple in agreeableness of
flavour.
Lovers of beautiful trees will agree in considering the sugar-pine as
the noblest of its family growing in the woods of America, if not the
most majestic of its kindred in the world. Its only rival, but of a
different type of beauty, is the Norfolk Island pine, of the south sea
islands.
Of the many pleasant memories of camp life in the forests of America
which are a source of delight to the writer none are recalled with
greater pleasure than those associated with the sugar-pine of the
Sierra Nevada, where the ground is carpeted with the long brown needles
that fall in showers at certain seasons from the boughs far overhead.
With the faded leaves are strewed also the great cones which always
excite wonder and admiration. In the clear air and brilliant sunlight of
the Californian mountains the luxuriant plume-like leaves far aloft
appear to be formed of burnished silver or have the yellow of gold,
according as the light strikes them, and at night the lofty boughs
swayed by the winds make music such as no other forest can produce.
Nothing in the vegetable world, not even the great sequoias, convey such
an abiding impression of strength and majesty as these pines which have
withstood the storms of centuries without losing their vigour or their
symmetry and beauty of form. Unfortunately as it would seem, however,
these magnificent trees are useful, as the term is commonly employed,
and are fast falling a prey to lumbermen, who measure their value in
dollars.
The yellow pine of the Pacific mountains, not to be confounded, however,
with the yellow pine of the southern Appalachian region, fortunately has
another common name, the _silver pine_, which is more appropriate and
distinctive. This is the most widely spread, perhaps, of all the pines
of North America, and is familiar to every one who has travelled through
the Pacific mountains from British Columbia to Mexico, and from the
Black Hills of Dakota or the mountains of Colorado and New Mexico
westward to within hearing of the surf of the Pacific Ocean. It ranks
second in size to the sugar-pine, but is a near rival in strength and
nobleness of form. As might be inferred from its wide distribution, the
silver pine had adapted itself to a great range of conditions, not only
of climate, but of soil and height above the sea. It is found from an
elevation of about 2,000 feet above the sea up the mountainsides nearly
to timber-line, and flourishes alike in the hot, arid valleys and in
regions bordering on perpetual snow and ice. One beautiful feature of
the silver-pine forests is their open, park-like character. The trees
stand far apart, and thus have room to reach not only a great size,
but a remarkable degree of perfection of form. Between the
islands of shade on the sunlit ground there is usually but little
undergrowth, and the far-extending natural pastures permit one to ride
in any direction without inconvenience.
One other pine of the widely extended Pacific forest demands attention
even from the passing traveller, not on account of its size, for it is a
dwarf in a land of giants, but for its wide distribution and the food
its large, oily seeds furnish for birds, squirrels, and even for man. I
refer to the piñon pine, of which there are several species. They are
seldom over 35 or 40 feet high, and are not remarkable for beauty,
although they furnish an agreeable feature in the sparsely
forest-clothed and semiarid region where they thrive best, but they bear
a profusion of small cones, each of which contains perhaps a dozen
edible and nutritious seeds. These seeds were formerly used by the
Indians for food on an extensive scale, and are still gathered in large
quantities, and may be found in the markets of our cities. The Indian
encampments in the piñon forests in the fall of the year are among the
most picturesque features of these degenerate days of the aborigines.
In the southwest portions of the United States the forests are confined
to the mountains and the higher table-lands, the hot, arid valleys being
without trees other than the larger growths of cacti and yucca. Similar
conditions are present in northern Mexico, but on the western side of
that republic and throughout practically the whole of the peninsula of
Lower California the mountains and valleys alike are treeless and
desolate.
As stated by C. S. Sargent, the forests of North America, exclusive of
Mexico, Central America, and the West Indies, contain arboreal
representatives of 158 genera of plants, of which 94 genera occur in the
Atlantic and 59 in the Pacific side of the continent, and 48 genera in
the tropical portion of southern Florida. Of the number of genera of
trees in the Caribbean forest we have no reliable census.
PRAIRIES, TREELESS PLAINS, AND PLATEAUS
To the west of the Atlantic forest lie the broad natural meadows termed
prairies, and still farther west the yet more extensive pasture-lands of
the great plateaus which reach the eastern base of the Rocky Mountains
(Fig. 28). The transition from the luxuriant and varied forest on the
east to the treeless, thinly grass-covered plateaus on the west side of
the interior Continental basin is gradual. The change occurs in the
prairie region, where a struggle has been in progress for thousands of
years between the conditions favouring and those adverse to tree growth.
The balance of power, so to speak, is the amount of rain or of
soil-stored moisture during the summer season. The gradual decrease in
the mean annual precipitation from east to west on the inland border of
the Atlantic forest continues westward, and on the plateaus adjacent to
the Rocky Mountains the aridity is such that no trees can grow except
along the immediate border of the stream, unless artificially irrigated.
The explanation of the absence of trees in the central and western
portions of the interior Continental basin is found in the mean annual
rainfall and the manner in which it is distributed throughout the year,
together with variations in the texture and composition of the soil, and
the disturbances in the natural conditions brought about by fires. The
question, "Why are the prairies treeless?" has been variously answered
by different observers. The outcome of a long discussion in this
connection seems to be that the main cause of the absence of trees lies
in the climatic conditions and principally in the lack of sufficient
rain during the long, hot summers. Arid regions the world over are
without forests, but the Prairie plains cannot be said to be arid; in
fact, the mean annual rainfall over the greater portion of this region
is equal to or exceeds that of many well-forested countries, averaging
as it does in general about 30 inches. But the prairies lie between the
more humid forest-covered regions on the east and the less humid or
subarid plateaus on the west, and during the summer season
droughts and hot, scorching winds are of common occurrence. It is the
long dry summer that establishes the critical conditions, particularly
about the eastern and northern borders of the prairies. Of secondary
importance is the character of the soil. An exceedingly fine soil, like
that of the prairies, as has been pointed out by J. D. Whitney, by
excluding the air from the roots of trees is detrimental to their
growth. Where the dryness of the summers make the lives of trees
precarious the nature of the soil, whether coarse or fine, becomes the
controlling factor. In the prairie region where the soil is more open
and porous than usual, although other conditions remain the same, as in
the Cross Timbers of Texas, trees flourish; while intervening areas
where the soil is fine are typical prairies. Again, where the climatic
conditions become critical, as during long, dry summers, the grass and
other vegetation burns readily, fire spreads rapidly and widely, and
young trees are destroyed. In the prairie region, as pointed out by J.
W. Powell, the Indians were formerly in the habit of burning the grass
each summer in order to insure more favorable pasturage for game during
the succeeding spring. This annual burning kept back the forest and led
to the eastward extension of the prairie.
During the past decade many groves have been planted on the prairies,
and have flourished, especially when the adjacent fields are cultivated
so as to allow the earth to store a larger share of the winter rain; the
success of this tree planting, it has been claimed, is evidence that the
nature of the soil is not a determining factor in the problem, because
trees will grow if protected from fire. The success of arboriculture on
the formerly treeless plains and plateaus, however, decreases as one
travels westward. On the western border of the prairies and on the great
plateaus, remote from streams, trees can be made to grow only by the aid
of irrigation. If this region had never been swept by fire it is safe to
say it would still be treeless. Each of the explanations referred to
above to account for the treeless condition of the prairies--one
referring it to soil conditions, and the other to the former prevalence
of fires--certainly has much in its favour, and for certain localities
seems satisfactory, but each point of view should include a broader
range and recognise the fact that the requisite critical conditions have
been furnished by wide-reaching climatic causes. The Prairie plains
furnish but one phase of the gradual change that occurs in the natural
mantle of vegetation when traced from the dense, well-watered forests of
the Appalachians and the Alleghany plateau westward to the semiarid and
truly arid lands of the great plateaus and Rocky Mountain region, where
only such plants as are able to withstand long-continued drought can
grow. This same broad conclusion is sustained also at the north, where
the prairie dovetails, as it were, with the subarctic forest.
The general or underlying reason for the treeless condition of the vast
central portion of the continent is doubtless a lack of sufficient rain.
The precipitation that does occur comes mainly during the winter season,
when the land is colder than the ocean; in summer the land becomes
highly heated and imparts its temperature to the air, which thus has its
capacity for moisture increased, and prolonged droughts occur. At the
south, in Mexico and the adjacent portion of the United States, the
trade-winds blow over a region which is more highly heated than the
ocean from which they come, and are hence drying winds. To the west of
the Great plateaus rise the Rocky Mountains, where climatic conditions
are different on account of elevation, and, as we have seen, forests
occur at considerable elevations, but not in the broader valleys. The
conditions unfavourable for tree growth are continued and even
intensified in the valleys of the central portion of the Pacific
mountain region, and culminate in the deserts of the Great Basin and
western Mexico. Throughout all of this vast treeless region the
controlling condition is deficiency of moisture, particularly during the
summer or growing season.
The nearest approach to desert conditions to be found in North America
occur in the valley of Utah and Nevada and the southern portion
of the Great Basin region in Arizona and Mexico. The bottoms of these
valleys are, in some instances, occupied by shallow lakes in winter,
when scanty rains occur, but during the long, hot summers they become
completely desiccated, and are then broad expanses of hard mud, cracked
by drying so as to resemble a tessellated pavement of cream-coloured
marble. These mud-flats or _playas_ are frequently absolutely without
plant life. Excepting the playas, however, and, in numerous instances, a
narrow belt of ground encircling them, which is white with efflorescent
salts, the valleys of even the most arid portion of the Great Basin
region are generally plant-covered. The most common and most widely
spread of the shrubs on these shadeless plains is the sage-brush. So
characteristic is this plant of countless valleys from Canada to Mexico
within the general region of the Pacific mountains that to one familiar
with the country the term "sage-brush land" brings to mind the leading
features of the region designated. The sage-brush lands are far from
being desert areas, however, for in early spring a profusion of low,
sweet-scented flowers bloom beneath the gray-green _Artemisia_, and
sufficient bunch-grass to sustain considerable herds may be expected in
the same localities.
The vast, irregular belt of forest encircling the central treeless
portion of the continent also dies out on its northern border, where the
subarctic forest is succeeded northward by the Barren Grounds and tundra
plains. Clearly the explanation of the absence of trees in the prairie
region and the adjacent plateaus cannot be applied to scarcely less
extensive treeless plains at the far north, where rain falls in summer
and the soil is always abundantly charged with moisture. It needs no
argument to show that the control among the conditions governing tree
growth at the north passes to the temperate element of climate, and that
the timber-line is there determined, as it is on high mountains, by the
severity of the winters' storms and frosts and the shortness of the
summers.
THE TREELESS MOUNTAIN TOPS
On the higher mountains of North America above the upper limit at which
trees are able to grow there are picturesque regions carpeted and
garlanded in late spring and summer with lovely flowers, the
indescribable charms of which are only known to those who rejoice in
climbing rugged peaks and in following the trails of the mountain-goat
along sharp-crested ridges. The gorgeous blossoms of these roof-gardens
of the world are much the same on all high mountains in temperate
latitudes, but from having become first widely known to civilized man on
the mountains of Switzerland, are generally termed alpine flowers. The
most attractive features of an alpine flora, which springs into bloom as
soon as the snow melts and forms a rapidly widening belt of colour as
the margins of the snow-fields recede higher and higher, is the great
profusion of brilliantly coloured blossoms. No sooner does the snow of
winter melt than the moist ground becomes enamelled in brilliant colours
on account of the springing up and quick blossoming of millions of hardy
plants. The growing season on mountain heights is short, but the sun's
energy is there more intense and the hours of light each day longer than
in the valleys below, and the plants adapted to such conditions pass
through their annual circle of changes from sprouting seed to mature
fruit with remarkable rapidity. In many instances the mountain-climber
finds beautiful lilies unfolding their sun-dyed blossoms at the bottom
of well-like depressions in lingering snow-banks. The gleaming
mountain-peaks when seen from afar are said to be crowned with snow, but
the mountaineer rejoices in the knowledge that their cold diadems are
wreathed and festooned about their lower margins with lovely blossoms.
Many mountains less ambitious than their neighbours have the garlands
without the crown. An alpine flora is present on the Pacific mountains
from Mexico northward to Alaska. Like the "timber-line" and the
"snow-line," the intermediate belt of profusely flowering herbaceous
plants descends lower and lower with decrease in latitude; on the great
volcanic cones of Mexico it has an elevation of over 15,000 feet;
on the Sierra Nevada the greatest wealth of flowers occurs at about
12,000 feet; on Mount Rainier widely extended gardens resplendent with
rainbow tints occur at 7,000 to 8,000 feet; and about the foot-hills
near Mount St. Elias, at an elevation of 2,500 feet or less above the
sea, every knoll and island-like area in the vast ice-fields is so
densely overgrown with brilliantly flowered plants that one has to part
the rank growths with his hands and press them aside with his alpenstick
in order to force a way through the fields of bloom. Admirers of
nature's loveliness who have not climbed to aspiring heights will find a
new and beautiful world in the public alpine garden on the summit and
about the snow-fields of the higher portions of the Pacific mountains,
where no sign-boards forbid entry and no fences obstruct the way. In
these regions nearest the sun and stars there are few, if any, plants of
utility to man, but marvellous beauty and lavish profusion fill the
foreground in every view. These glorious mountain heights have their
use, however, although as yet known to but few; rest and recreation amid
scenes at the same time novel and most inspiring may there be found by
the toilers in our crowded cities.
Among the Atlantic mountains only a few summits attain a sufficient
elevation to claim a wreath of alpine flowers. Something of the nature
of the gorgeous fields of bloom about the great peaks of the Pacific
mountains is suggested on the treeless summits of the White Mountains,
but although classed by botanists among alpine floras, the plants
growing there fail to give a true idea of the display characteristic of
the mountains which make a nearer approach to the lower limit of
perennial snow. In the southern Appalachians the absence of a luxuriant
alpine flora is perhaps more than counterbalanced by the profusion of
rhododendrons, azaleas, and laurels.
* * * * *
One instructive lesson suggested by this hasty glance at the plant life
of North America is furnished by the quick response that vegetation
gives to conditions of environment. Throughout the greater
divisions of the forest, prairies, grass-covered plains and valleys, and
flower-decked mountain heights there are constant variations from
locality to locality in the plant life to meet seemingly obscure or but
slight changes in the conditions of temperature, humidity, exposure to
sunlight, soil composition, soil texture, etc.; and besides there is a
never-ceasing struggle for existence among the plants themselves which
leads to important modifications of a flora. These changes occur from
locality to locality, frequently within a short radius, but more than
this, the resultant of the various modifying conditions on which plant
life depends are not constant even for a given locality. The study of
extinct floras has shown that during the preceding ages in the earth's
history marvellous changes in the plants of many regions, and, in fact,
of the entire earth's surface, have taken place. The distinct
impressions of palm-leaves, for example, are commonly found in the rocks
of the Cascade Mountains, where spruces, firs, and cedars now dominate
the landscape. Still more striking is the fact that even treeless
Greenland and the largely ice-covered islands of the arctic archipelago
were formerly clothed with forests as luxuriant and varied as those now
growing in the southern Appalachian region. Although the migrations of
existing forests during the few centuries of which we have historic
records have been too slow to be appreciated by man, yet it is safe to
conclude that changes similar to, and in fact a continuation of, those
known by geologists to have taken place in the distribution of the
vegetation of the continent since the Tertiary period are still in
progress. With far-reaching and exceedingly slow changes in climatic
conditions and in elevation above the sea due to upheaval and
denudation, the plants of our forests, prairies, and mountainsides, are
being moved here and there, in ever-changing combinations. Nature thus
secures a rotation in the vegetation of a region, as the careful
husbandman varies his crops from year to year. The suggestion in this
connection furnished by geologists is that we are living in a
spring-time following the great winter, known as the Glacial epoch, and
that the tropical, temperate, and subarctic forests are migrating
northward in an orderly march, and each in turn ascending higher and
higher on the more lofty mountains.
LITERATURE
MUIR, JOHN. _The Mountains of California._ T. Fisher Unwin,
London, 1894.
PINCHOT, GIFFORD. _A Primer of Forestry._ United States Department
of Agriculture, Bulletin No. 24, Washington, D. C., 1899.
SARGENT, C. S. _Report on the Forests of North America._ Tenth
Census of the United States, vol. ix, Washington, D. C., 1884.
United States Geological Survey. Reports on Forestry.
CHAPTER V
ANIMAL LIFE
A common ground to zoologists and geographers in the exploration of
which they derive mutual pleasure from assisting each other, is the
geographical distribution of animals. In this connection the fauna of
North America presents perhaps even more interesting problems than does
its flora.
GENERAL PRINCIPLES OF GEOGRAPHICAL DISTRIBUTION
In the study of the distribution of animals over a continent, the
discovery of the laws determining the intangible boundaries which the
members of a species may not pass is even more difficult than the
similar task in the case of plants. Plant species for the most part
advance and retreat slowly as conditions change, and, with minor
exceptions, there is no freedom of movement for the individual; but
animals, and especially the higher forms, are sensitive to even slight
changes in their environment, and there is more or less individual
freedom to travel over the land, to fly through the air, or to swim
through the water. Why the members of a given species which have
apparently unlimited power to travel should be confined to a certain and
frequently a narrowly circumscribed area has excited the curiosity of
man for many centuries.
A point is gained in reference to the distribution of animal species
when it is remembered that animals are either directly or indirectly
dependent on plants for food, and it follows that if plants, as we have
seen, are so largely controlled in their distribution by climate, the
secret of the distribution of animals is to be sought in the same
direction. When a thoroughly satisfactory classification of
climatic provinces is arrived at, it will no doubt be found to agree
with the larger features of plant distribution, and should coincide,
although perhaps less definitely, with the major divisions into which
the zoologist partitions the earth's surface. This principle has been
recognised by C. Hart Merriam in subdividing the United States into
"life-zones and crop-zones," and in the following pages his view will be
discernible, although losing much of their clearness by reflection.
_The Place of North America in the Life Realms of the Earth._--The
geological distribution of animals has been critically studied by P. L.
Sclater, A. R. Wallace, T. H. Huxley, and others, and the entire land
area of the earth subdivided into realms, regions, etc., in such a
manner as to indicate the present grouping of animals. One of the latest
of these broad views of the life of the earth is presented by Richard
Lydekker, who, from the evidence furnished by both living and extinct
mammals, has divided the world into three great "realms," two of which
are again subdivided into "regions," as follows:
{ 1. Australian region.
Notogæic realm { 2. Polynesian region.
{ 3. Hawaiian region.
{ 4. Austro-Malayan region.
Neogæic realm Neotropical region.
{ 1. Malagasy region.
{ 2. Ethiopian region.
Arctogæic realm { 3. Oriental region.
{ 4. Holarctic region.
{ 5. Sonoran region.
In this classification, North America falls in part in two realms, the
_Arctogæic_ and _Neogæic_, the former embracing the table-land of
north-central Mexico and all of that portion of the continent lying to
the northward, while the lowland of Mexico, together with Central
America and the West Indies, falls in the latter realm. The Arctogæic
includes also nearly the whole of the eastern hemisphere. The
relationship expressed in this classification of both the living and
extinct mammalia of North America to that of Eurasia, is supposed to be
due to a former land connection between the Old and the New World
at Bering Strait, and is most clearly marked by northern species, the
intercontinental bridge being too far north to be available for southern
forms. The mammals and many of the other animals of the low, hot borders
of Mexico and of Central America are a northward extension of the fauna
of South America--that continent constituting nearly the entire Neogæic
realm. The mammals of the West Indies are few in species, and have their
nearest relationship with the fauna of the continent to the southward.
LIFE-REGIONS AND LIFE-ZONES
The detailed study of the zoology of North America is far from complete,
but the voluminous results reached have led to several attempts at broad
generalization in reference to geographical distribution. Important and
highly instructive memoirs have been presented in this connection by J.
A. Allen, Angelo Heilprin, E. D. Cope, and others, who have in the main
attempted to correlate the distribution of animal species, but
principally the mammals, with variations in mean annual temperature.
Among the latest of these contributions, and marking the advance made at
the close of the nineteenth century, is the classification proposed by
C. Hart Merriam, already referred to in the sketches that have been
given of the climate and of the flora of the continent. The basis for
this classification is the seemingly well-determined law that the
northward distribution of terrestrial animals and plants is controlled
by the sum of the positive temperatures for the entire season of growth
and reproduction, and that the southward distribution is governed by the
mean temperature of a brief period during the hotter portion of the
year. By "positive temperatures" is meant the sum of the mean daily
temperature above that which determines the period of physiological
activity in plants and of reproductive activity in animals, assumed to
be 6° C. or 43° F. The exact length of the period to be taken as the
hottest portion of the year has not been definitely determined, but
must be short enough to fall within the hottest part of the
summer in high northern latitudes, and probably increases in length from
north to south; the time assumed is the six hottest consecutive weeks of
the year.
On the basis just stated, Merriam has divided North America into the
following life-regions and life-zones:
+--------+---------+---------------+---------------------------------+
| | | | Governing Temperatures |
| | | +-----------------+---------------+
| | | | NORTHERN LIMIT |SOUTHERN LIMIT |
| | | +-----------------+---------------+
| Realms | Regions | Zones | Sum of normal |Normal mean |
| of | | | mean daily |temperature of |
| Ly- | | | temperatures |the six hottest|
| dekker | | | above 6° C. |consecutive |
| | | | or 43° F. | weeks |
+--------+---------+---------------+--------+--------+-------+-------+
| | | | Deg. C.| Deg. F.|Deg. C.|Deg F. |
| | |{Arctic | | | 10[3] | 50[3] |
| |{Boreal |{Hudsonian | | | 14[3] |57.2[3]|
|Arcto- |{ |{Canadian | | | 18 | 64.4 |
| gæic |{ |{Transition | 5,500 | 10,000 | 22 | 71.6 |
| |{Austral |{Upper austral | 6,400 | 11,500 | 26 | 78.8 |
| | |{Lower austral | 10,000 | 18,000 | | |
|Neogæic |Tropical |(At present | | | | |
| | | unclassified) | 14,500 | 26,000 | | |
+--------+---------+---------------+--------+--------+-------+-------+
[3] Estimated from insufficient data.
The boundaries of the regions and zones given in the above table are
shown on the map facing page 173, but for detailed information
concerning the basis of the classification the reader is referred to the
monographs by Merriam mentioned at the end of this chapter. In the
publications referred to lists are presented of the resident mammals and
birds characteristic of each region and of its subdivisions to the north
of Mexico. While the boundaries shown on the accompanying map can be
recognised in nature by the naturalist and serve a useful purpose, to
the unskilled observer each region would appear to blend with its
neighbours by intangible gradations. In fact, in this, as in the case of
so many other similar instances in nature, there is an absence of
definite, or what may be termed hard and fast lines. The significance of
the boundaries referred to, to the unskilled observer, is still more
obscure by the fact that the migratory birds, and to some extent the
mammals, annually pass from one zone to another, and besides,
several conspicuous mammals and birds are permanent residents in more
than one zone.
THE MAMMALS
The relation of the mammals of North America to the similar animals now
inhabiting other portions of the earth may be briefly shown by
indicating the distribution of the orders into which the mammalia are
divided. It will be remembered that in general each order is subdivided
into families, these again into genera, the genera into species, and a
species may contain several varieties. The classification here adopted
is the one used by Lydekker in his Manual of Palæontology. An order when
represented in the fauna of a continent is indicated in the following
table by a plus, and when absent by a minus sign.
CLASS--MAMMALIA
+-------+-------------+--------------------+--------------------------+
| | | | DISTRIBUTION |
| Sub- | | +---+---+----+------+------+
|Classes| Orders | Examples | N.| S.|Eur-| |Aus- |
| | | |Am.|Am.|asia|Africa|tralia|
+-------+-------------+--------------------+---+---+----+------+------+
| {|1. Primates |Man, lemurs, | + | + | + | + |(Man) |
| {| |apes, monkeys. | | | | | |
| {|2. Chiroptera|Bats. | + | + | + | + | + |
| {|3. Insecti- |Moles, shrews, | + | + | + | + | - |
| {| vora |hedgehogs. | | | | | |
| {|4. Carnivora |Lions, tigers, cats,| + | + | + | + | - |
| {| |dogs, seals, etc. | | | | | |
| {|5. Rodentia |Beavers, rats, | + | + | + | + | + |
| {| |mice, squirrels, | | | | | |
| {| |rabbits. | | | | | |
|Eu- {|6. Ungulata |Ox, horse, elephant,| + | + | + | + | - |
|theria{| |tapir, etc. | | | | | |
| {|7. Sirenia |Dugong and | + | + | + | + | + |
| {| |manatee. | | | | | |
| {|8. Cetacea |Whales, dolphins, | + | + | + | + | + |
| {| |narwhals. | | | | | |
| {|9. Edentata |Sloths, armadillos, | + | + | + | + | - |
| | |ant-eaters. | | | | | |
+-------+-------------+--------------------+---+---+----+------+------+
|Meta- |10. Marsu- |Kangaroos, opossums,| + | + | - | - | + |
|theria | pialia |etc. | | | | | |
+-------+-------------+--------------------+---+---+----+------+------+
|Proto- |11. Monotre- |Ornithorhynchus, | - | - | - | - | + |
|theria | mata |echidna | | | | | |
+-------+-------------+--------------------+---+---+----+------+------+
1. Of the _primates_, exclusive of man, the monkeys are the only
representatives in North America. Several species are common in Central
America, but they are absent from the West Indies, and do not occur
north of the _terra caliente_ of Mexico.
2. The bats are world-wide in their distribution, and several genera and
species occur on this continent, their northern limit being in central
Canada; during the winter in the United States and Canada they hibernate
largely in caverns. One family of the _Chiroptera_, the leaf-nosed bats
(_Phyllostomatidæ_), are strictly American, having their principal
habitat in the southern continent, but ranging as far north as the West
Indies, Mexico, and southern California. These are the vampires of which
many harrowing tales are told. The Central American species are small,
not larger than an English sparrow, but do not hesitate to attack
cattle, and even men.
3. The insect-eating mammals are represented by a large number of genera
and species, of moles and shrews, but hedgehogs are absent.
4. The flesh-eating animals are well represented by the cats (jaguars,
panthers, and lynxes), wolves, bears, racoons, martens, etc. Many
species of the seal family occur about the entire coast-line from Panama
to the Arctic Ocean. The lion, tiger, leopard, hyena, are absent.
5. The rodents are present in great numbers not only of individuals, but
of species and genera; as rats, mice, jumping-mice, squirrels,
porcupines, beavers, rabbits, etc.
6. The hoofed animals, _ungulates_, are represented by the bison,
musk-ox, several deer, antelope, mountain-sheep and mountain-goat,
tapir, and swine (peccary). Abundant remains of extinct species of the
horse family have been found, ranging far back in geological time, but
native horses are not known to have existed since the coming of
Europeans. The most notable vacancies in this order in the living fauna
are the rhinoceros, hippopotamus, camel, giraffe, and elephant, although
these are abundantly represented by fossil forms.
7. The _Sirenia_, which includes certain large herbivorous marine
mammals of wide distribution, are represented on the borders of the Gulf
of Mexico and the Caribbean Sea by the manatee.
8. The _Cetacea_ are present in the marine waters adjacent to the coast,
more especially in the north, where whales of several species, dolphins,
the narwhal, etc., are found.
9. Of the _Edentata_, which are so characteristic of the fauna of South
America, and with one exception (the scaly ant-eater, not found in
America) do not occur in the Old World, only the armadillo can be
credited to North America; of this, two species occur from Texas
southward.
10. The marsupials, found nowhere else in the world to-day except in
Australia and America, are represented by the opossum, of which two
species are common in the United States.
11. The lowest known order of the mammalia, the _Monotremata_,
represented in Australia by the duck-billed platypus (Ornithorhynchus)
and the _Echidna_, is unknown in America.
Considered in reference to their abundance, large size of individuals,
and number of species, in comparison with the other orders present,
North America may be said to be the home of _herbivores_. The only
continent in rivalry with it in this respect is Africa. More abundant in
individuals and species than the herbivorous mammals, however, but
smaller in size and frequently diminutive, are the rodents. The
carnivores are fortunately limited in number of species, although the
individuals of certain species are at times numerous, but not in general
dangerous to man.
SOME REPRESENTATIVE MAMMALS
To the general reader the animals of greatest interest are no doubt the
mammals, and particularly those which attract the sportsman, are of
value for food, or furnish fur and skins for clothing. Of such animals
the northern portion of North America and the mountains extending
southward into the austral region furnish a large number.
_The Musk-Ox._--In the far north, mostly beyond the arctic circle, lives
the musk-ox, the hardiest of herbivores, in which, as expressed in its
generic name, _Ovibos_, there is a curious mingling of the
characteristics of the sheep and the ox. The teeth are similar to those
of the sheep, the female has but two mammæ, and beneath the long
yellowish-brown hair of the outer coat there is a thick wool-like
growth. Its gentle, inoffensive nature is also similar to that of the
sheep. The large feet and the horns, however, are like those of the ox
tribe. The horns resemble those of the Cape buffalo, being broad at the
base and covering nearly the entire forehead. They slope downward at the
sides, and then curve forward and outward, at the same time tapering to
a sharp point, which renders them efficient weapons. These
characteristics, although intermediate between those of the sheep and
the ox, are more strongly inclined to the former. In reality, however,
the musk-ox is more goat-like than sheep-like, as is indicated by its
covering of hair, its short sturdy legs, the cannon-bone being
remarkably short, and its ability as a climber.
A full-grown musk-ox measures about 8 feet in length, inclusive of the
short tail, and is 3 feet, 8 or 9 inches in height at the shoulders. The
thick-set, shaggy body is supported on short stout legs, and the feet
are broad, to serve both as scrapers in clearing away the snow from the
moss and herbage on which it lives and in climbing ice-covered slopes.
Its range is over the Barren Grounds of Canada, the islands of the
arctic archipelago, and the border of Greenland. Peary found it grazing
in herds in the far north of Greenland beyond the inland ice, and was
saved from starvation by the food it furnished. Although hardy and well
adapted by nature to withstand the most severe cold, it moves southward
over the Barren Grounds in winter and to some extent at least seeks
shelter in the subarctic forest, but apparently does not pass to the
southward of latitude 59°. Like certain other animals of the northern
portion of the continent, its habitat is to the northeastward and it is
unknown in Alaska.
Bones of the musk-ox found in the frozen soil of Siberia indicate that
it formerly had a circumpolar distribution. A skull obtained near Salt
Lake City, Utah, in 1871, and the presence of its bones in the
superficial deposit of Europe as far south as the Pyrenees, show that it
formerly lived far to the southward of its present southern limit. This
was during the Pleistocene division of geological history, when glacial
ice covered all of Canada and the arctic animals were crowded southward.
As the ice melted and its southern margin receded, the musk-ox moved
northward. The absence of this species in northern Europe and Asia,
where the climatic conditions, nature of the vegetation, etc., are
similar to those of its present home, is perhaps due to the influence of
man. The successful introduction of the domesticated reindeer into
Alaska suggests that beneficial results would follow the transplanting
of the musk-ox to northern Siberia.
_The Polar Bear._--About all of the northern coast-line of America,
including the shore of Bering Sea and Baffin Bay, lives the well-known
polar bear, which is circumpolar in its distribution. The wide range of
this the most northern of the bear tribe is due not only to its strength
and ability to make long journeys over rough ice-floes and the wide
distribution of the animals it feeds upon, principally the hair-seal,
but is aided by the fact that it takes to the water readily and is a
good swimmer. It has also been known to make long journeys on floating
ice.
_The Eskimo Dog._--Another animal of circumpolar distribution, the
original home of which is unknown, is the Eskimo dog, the range of which
has no doubt been extended while the distribution of many other animals
has been curtailed, owing to human influences.
_The Caribou._--The neighbour of the musk-ox in the desolate solitudes
of the far north, and in part ranging over the same ground, is the
caribou, the American representative of the reindeer. Indeed the caribou
and the reindeer have been considered as belonging to the same species
by some naturalists, but recently the American division of the genus has
been shown to consist of at least five species, each of which
differs from the one found in Europe and Asia. Among hunters and
sportsmen, two divisions have long been known, namely, the woodland
caribou and the Barren Ground caribou. The former includes the larger
species, or the caribou proper, as it may be termed, and the recently
described species from Newfoundland and Alaska; while the latter is
represented by a single species, the _Rangifer articus_.
The woodland caribou is in general about twice the size of the species
inhabiting the Barren Grounds, has a height of 4½ feet at the
shoulder, and weighs some 250 pounds, although the males sometimes reach
a weight of 400 pounds. Its range is from Nova Scotia and Newfoundland
northwestward through the subarctic forest to British Columbia and
northeastern Alaska. As its popular name signifies, its home is in the
forest, and although meeting the smaller form during the latter's
southward migrations, it does not extend its range to the Barren
Grounds. On the south, it was formerly found in northern Michigan and in
southern New York, and thence eastward through Vermont, New Hampshire,
and Maine. Owing to the activity with which it has been hunted, it has
for the most part been crowded to the north of the St. Lawrence, and is
reported to be greatly diminished in numbers even in the wilds of
Labrador. It still wanders into the woods of New Hampshire and Maine,
and occurs somewhat abundantly in Nova Scotia and Newfoundland. It is
the caribou of Newfoundland, etc., which comes nearest the reindeer in
size and in the shape of its magnificent antlers, but none of the
American species has been domesticated.
The Barren-Ground caribou still occurs in large herds in northern
Labrador, on the treeless region to the west of Hudson Bay, and in
winter migrates southward into the shelter of the subarctic forest. In
its northern range it reaches the shore of the Arctic Ocean and the
islands adjacent, and on the west follows the tundra to the Bering Sea
coast. In Alaska it formerly occurred in immense herds, especially in
winter, when it made long inland journeys through the forest and across
the frozen rivers, but the invasion of the region by miners and
the supplying of the natives with firearms has led to a great reduction
in its numbers. In the barren and but seldom traversed region to the
west and north of Hudson Bay the caribou is still in its primitive
condition and moves in bands numbering several thousand. In this
connection an extract from the journal of J. B. Tyrrell, of the Canadian
Geological Survey, is of interest: "All day [July 30, 1893] the caribou
have been around us in vast numbers, many thousands being assembled in a
single herd. One herd collected on the hill behind our camp, and another
remained for hours in the wet bog on the point in front of us. The
little fawns were running about everywhere, often coming up to within a
yard or two of us, uttering their sharp grunts as they stood and looked
at us or as they turned and ran back to the does. About noon a large
herd had collected on the sides and summit of the hill behind us. Taking
a small hand-camera with which we were supplied, we walked quietly among
them. As we approached to within a few yards of the dense herd, it
opened to let us in and then formed a circle around us, so that we were
able to stand for a couple of hours and watch the deer as they stood in
the light breeze or rubbed slowly past each other to keep off the black
flies. The bucks, with their beautiful branching antlers, kept well to
the background. Later in the afternoon a herd of bucks trotted up to us
and stood at about 40 yards distant. This was a most beautiful sight,
for their horns were fully grown, though still soft at the tips, but
unfortunately we had no camera with us. We did no shooting to-day." The
herd of caribou just described was estimated to contain between 100,000
and 200,000 animals.
The destruction of the woodland caribou in the eastern portion of Canada
has been so great that it is in danger of being exterminated, and great
suffering, and even starvation has overtaken the Indians of that region
in consequence. Similar, but even more alarming results have followed
the thoughtless slaughter of the Barren-Ground caribou in Alaska, and to
prevent the suffering and even threatened extermination of the
natives, reindeer from Siberia and northern Europe have been introduced
by the United States Government[4] and are thriving under the care of
herders from Lapland. The moss on which the reindeer feed is abundant in
Alaska, and there seems no good reason why they should not become as
numerous and useful in their new home as they were in the boreal portion
of the Old World. The first reindeer were introduced in Alaska in 1881,
and the several herds, collectively, now number 3,323.
[4] The introduction of domesticated reindeer into North America is a
very important matter, and one which if properly conducted will add
vastly to the food supply and resources for clothing for both native and
white people. The civilization of the natives in the northern portion of
the continent and the securing for them of a source of subsistence which
will depend on their own care and industry hinges on the success of this
undertaking. Much information in this connection may be found in the
reports of Sheldon Jackson, published by the Bureau of Education at
Washington between 1893 and 1900.
_The Moose._--This, the largest living representative of the deer tribe,
and with the exception of the bison the largest existing land mammal of
North America, formerly inhabited the continent throughout its entire
breadth from the forty-third to the seventieth degree of latitude, or
from the mouth of the Ohio to the mouth of the Mackenzie. Although
crowded northward and now found only sparingly in the United States, as,
for example, in the extensive forests of Maine and in the still larger
forests clothing the mountains of Montana and Idaho, it has held its own
in the wildest and most remote portions of the Pacific mountains in
Canada and Alaska, where its numbers are perhaps nearly as great as they
were a century ago. Its preservation is due not only to its shyness,
remarkably quick hearing, and keen sense of smell, but to its solitary
habits and the fact that it does not gather in herds during the
breeding season, like most other deer.
A full-grown male moose is from 7 to 8 feet high at the shoulder, and
from 10 to 12 feet high at the tip of the magnificent antlers when
standing erect, and is from 800 to 1,200 pounds in weight. The
broad palmate antlers with numerous sharp points sometimes measure 8½
feet or more from tip to tip. The does are without antlers, and are
still more ungainly than the long-legged and apparently awkward males.
Stringent laws are now enforced for the protection of the moose in all
of the inhabited portions of its range, and it is likely to survive and
to continue to tempt the sportsman to traverse the wild regions it
inhabits for several generations to come.
_The Wapiti._--Next in size to the moose, and in many ways the grandest
of the deer tribe not only of America, but of the world, is the wapiti
or American elk. In language not pedantic, W. A. Perry speaks as follows
of this noble animal: "Monarch of the wilderness, lord of the mountain,
king of the plain, what hunter who has sought thee in thy pine-embowered
home whose heart-beat does not quicken and whose eye does not brighten
at the mention of thy name! For with it comes the recollection of
boundless prairies, grass-robed and flower-decked; of pine-clad,
snow-capped mountains; of sweet breezes, gentle melodies, and grand
trophies. I once heard an Indian speak his last words, and they were
these: 'To-morrow, in the Spirit Land, again shall I chase the wapiti.'"
Although the wapiti is one of the typical animals of the boreal region,
in its primitive freedom it overstepped the boundaries of the life-zones
which science seeks to define, and marched southward far into the
austral region. It was found at the coming of the white man in nearly
all parts of what is now the United States, and extended from the
table-land of north-central Mexico northward to the fifty-sixth or
fifty-seventh degree of latitude, or about the position of Lake
Athabasca. Its northern range thus overlapped the region inhabited by
the moose and caribou, while at the south it was exposed to the attacks
of the jaguar. As civilization advanced across the continent, the wapiti
slowly retreated, and in diminished numbers it now lives in the wildest
portion of the Pacific mountains to the north of Snake River and the
Columbia. It is still abundant in the Olympic Mountains of Washington,
the Bitter Root Mountains of Idaho, and in Montana. A large herd
finds protection in the Yellowstone National Park, but in winter, when
migrating southward, is exposed to most destructive attacks from both
white and Indian hunters. Among the mountains of the mainland in British
Columbia and the central and more rugged portion of Vancouver Island it
is still the "king of the wilderness."
The male wapiti at maturity is some 7 or 8 feet high at the shoulders,
and lifts its wide-spreading antlers fully 11 feet from the ground. Its
weight is from 800 to possibly 1,100 pounds. The colour is, in general,
dark brown, with lighter shades on the thighs, and changing to black
beneath the body; there are stripes of light brown on either side of the
tail which join an area of similar colour beneath the hind legs; the
colour varies, however, at different seasons and in different
individuals. The head is small, well formed, and beautiful. The carriage
of the animal and its bold, undaunted mien, when roaming its native
mountains and glens, is all and more than poets ascribe to the stag of
the Old World.
Stringent laws are now on the statute-books for the protection of the
wapiti, both in the United States and Canada, but the difficulties in
the way of enforcing them in regions remote from civilization are great.
The wapiti does not extend into the most forbidding wilds of the far
north, where its safety as a species, as in the case of the moose, would
be insured, and besides, congregates in bands, which facilitates its
slaughter. Its range has been steadily decreasing since the coming of
the white man, and particularly since the introduction of firearms among
the Indians, and its extinction, outside of reservations and parks, is
to be expected in the near future.
_The Smaller Deer._--Besides the caribou, moose, and wapiti, there are
half a dozen or more members of the deer family (_Cervidæ_) represented
in the fauna of North America. Of these the Virginia deer is best known,
as its range embraces the most thickly settled portion of the continent
between Maine and the Gulf States, and from the Atlantic coast to the
Rocky Mountains. In spite of indiscriminate slaughter and poorly
enforced game laws, this species has not only held its own, but in
recent years has greatly increased in number in certain localities. To
the west of the range of the Virginia deer and merging with it in part,
in the Pacific mountain region occur the white-tailed, black-tailed
mule, and sonora deer, and perhaps other species. The combined ranges of
these several species embrace the larger part of the continent and
extend from eastern Canada to the Pacific coast, and from southern
Alaska to Panama.
Next to the deer comes the antelope, formerly so common on the Great
plateaus. This, the pronghorn antelope, as it is usually termed, is
about the size of the domestic sheep, but with long slim legs, and is a
most active and exceedingly graceful animal. Its true home is on the
treeless plateaus east of the Rocky Mountains, but its range extends
from Saskatchewan to northern Mexico, and from the Prairie plains to the
Cascade Mountains in Oregon. It has steadily decreased in number,
especially during the last quarter of a century, and is now no longer
seen in the large bands that were formerly an attractive feature of the
sea-like plains over which it travels seemingly with the freedom of a
bird.
The animals thus far referred to have their range determined mainly by
the broader features of climate, but not in a conspicuous way by the
relief of surface. They inhabit mountains, plateaus, and plains alike,
as is shown most conspicuously in the case of the wapiti, which formerly
grazed in large herds on the prairies of the Mississippi Valley, and has
been killed at an elevation of over 10,000 feet in the Pacific
mountains. Not so, however, with the mountain-climbers whose names
follow, which have their chosen "station" on the mountains at
timber-line and ascend as far above that horizon as vegetation grows.
_The Bighorn or Mountain-Sheep._--The bighorn, of which three species
are now recognised, has its home in the Pacific mountains from northern
Mexico to central and northern Alaska. Its vertical range is also great,
as it has been seen on the precipitous walls of the Grand Cañon of
the Colorado, but a few hundred feet above sea-level, and about
the summits of the peaks of Colorado and in the Sierra Nevada and
Cascade Mountains at elevations of from 10,000 to 13,000 feet. An
exception to the fact that the bighorn is usually found on rugged
mountains and is most at home on seemingly inaccessible cliffs is
furnished by bands which live and appear to thrive amid the Bad Lands
along the Missouri River, some 400 miles to the eastward of the Stony
Mountains.
The bighorn resembles the wapiti in colour, although it is of a lighter
brown, especially in winter. It is clothed with wool beneath the stiff
outer coat of hair, and is a true sheep, but larger than any
domesticated variety of _Ovis_. The rams attain a height of at least 3
feet 6 inches at the shoulder, and weigh some 300 or 400 pounds. Both
sexes are provided with horns, but those of the male are much the
larger, and in the finest examples attain a length of 30 inches,
measured along the outer curve, and a circumference at the base of 15 or
16 inches. The most magnificent head ever obtained, so far as the writer
has been able to learn, is that of a ram shot in the Selkirk Mountains,
the horns of which are 52½ inches in length, measured along the outer
curve, and 18½ inches in circumference at the base. These immense
horns are used, as in the case of the domestic ram, in fighting, but the
widely current statement in reference to the animals alighting on them
when jumping from precipices is entirely mythical. The bighorn is a
fearless and skilful mountaineer, and will climb or descend precipices
by bounding from ledge to ledge where the most reckless hunter dares not
follow. Its ability to find a sure footing on even smoothly glaciated
rocks is due to the peculiar structure of the feet, which have a
rubber-like pad beneath the sharp-pointed and sharp-edged hoofs.
_The Mazama or Mountain-Goat._--The companion of the bighorn on the
lofty mountains, but even more thoroughly a mountaineer, is the
so-called mountain-goat, _Aplocerus montanus_, which, in spite of its
long hair, short curved horns, sturdy legs, bearded chin, and general
goat-like appearance, and more than the goat's ability to climb,
is in reality more nearly related to the antelope than it is to the
sheep. This alpine antelope, unlike its cousin of the plains, is only at
home on dizzy heights, and summer and winter alike lives at timber-line
on the mountains or in the alpine gardens adjacent to perpetual snow.
One of the earliest generic names under which it is assumed this alpine
antelope was included, namely, _Mazama_, although rejected by
naturalists, has recently been revived and adopted by an enthusiastic
mountaineering club in Portland, Oregon, as their name, and is likely to
become widely known. Among the hunters and the inhabitants generally of
the region where the animal under consideration lives it is termed the
mountain-goat, and no protest from naturalists, however well founded, is
likely to bring about a change in this connection.
The mazama is entirely white, excepting its hoofs, horns, and narrow
lines about the eyes and nostrils, which are black. In general, it is
smaller than the bighorn, but bucks have been reported to attain a
length of nearly 6 feet and a weight of some 300 or 400 pounds. Its
habitat is not only higher on the mountains but more restricted in
geographical extent than that of the bighorn. It is said to live about
Mount Whitney, the highest summit in the Sierra Nevada, but is unknown
farther south; in Colorado it is reported to have been seen on a few of
the higher peaks, but its main range begins well to the north of these
outlying localities, in the mountains of Montana and Idaho and in the
Cascades. To the north of the United States it occurs throughout the
higher ranges of British Columbia and in the mountains of southern
Alaska as far west at least as Cook Inlet. It is plentiful and as yet
undisturbed by hunters on the foot-hills about Mount St. Elias, where
the alpine conditions congenial to it occur at an elevation of from
2,000 to 3,000 feet above the sea. Like all of the larger animals, and
especially the herbivores, the bighorn and the mazama are sought by
sportsmen, but on account of the ruggedness of the regions they inhabit
and their wariness they are likely to survive when most other examples
of "big game" shall have been exterminated. Both the bighorn and
the mazama are sought by Indians for food and for their pelts, and their
horns are frequently used, especially in Alaska, in the manufacture of
spoons. They are practically of no economic importance to white men,
although their flesh when young is excellent food, and their fleeces
would be of value to the weaver if they could be obtained in sufficient
quantity. They serve, however, to entice the sportsman, who is usually
an ardent lover of nature, into some of the wildest and grandest regions
the continent affords. Their value in this connection is not to be
measured in dollars, and strenuous efforts should be made to insure
their continuance.
[Illustration: FIG. 31.--Bison at Silver Heights, Winnipeg. (Photograph
by William Notman & Son.)]
_The Bison._--Of all the larger mammals of North America, none was more
numerous at the time Europeans advanced over the continent than the
bison or "buffalo" (_Bos americanus_), and none more important alike to
the Indian and the white man. The part played by this relative of the
domestic ox in the history of the country is not only instructive, but
one of the best illustrations that can be furnished of the practical
extermination of a species through the greed and lack of forethought of
so-called civilized man.
The bison is a shaggy, brown animal, about the size of the well-known
Durham breed of cattle, but with a larger head and a prominent hump on
the shoulders (Fig. 31). The hind quarters are small in comparison with
the massive head and shoulders, and appear weak. The head, neck,
shoulders, and fore legs are covered with thick matted hair, at times 16
inches long and of a dark-brown colour merging into black. The straight
black hair beneath the chin of the bull is usually some 10 inches in
length, and as the animal carries its head low, frequently sweeps the
ground. Back of the medial portion of the body the hair is short and of
a yellowish-brown colour, or "between dark umber and a living-liver
brown," as Audubon says. There is much variation in colour, however, and
distinct varieties have been stated to exist. The horns, hoofs,
and a bare space about the nostrils and mouth are black.
The weight of a fully grown bull is about 2,000 pounds, and of a cow
1,200 pounds.
[Illustration: FIG. 32.--Range of the Bison.]
The boundaries of the region in which the bison has been seen by white
men, together with the dates of its extermination in various sections of
the country, etc., are shown in Fig. 32. In about 1870 the vast herd
which ranged over the treeless plateaus and Prairie plains between the
Rio Grande and Great Slave Lake was divided, owing to the great
slaughter that occurred in the vicinity of the Central Pacific Railroad,
into two herds, one of which had its summer range in Montana and
neighbouring territory, but moved northward in summer into
Canada, while the other fed on the plains of the west Texas region in
winter and moved northward in summer as far as southern Nebraska. In
each case a southward movement was begun as winter approached, but these
seasonal changes scarcely warrant the name of migrations.
The number of these large animals living between the Mississippi and
Rocky Mountains previous to 1872, even after being hunted for centuries
by the Indians and killed in constantly increasing numbers each year by
white men for half a century, can only be reckoned in millions. Many
trustworthy observations are on record, however, from which the vastness
of the herds can be approximately judged. For example, R. I. Dodge thus
refers to a herd which he passed through in the Arkansas Valley in May,
1871, when it was moving northward: "The great herd could not have
averaged, _at rest_, over 15 or 20 individuals to the acre, but was not
less than 25 miles wide, and from reports of hunters and others it was
about five days in passing a given point, or not less than 50 miles
deep. From the top of Pawnee Rock I could see from 6 to 10 miles in
almost every direction. This whole vast space was covered with buffalo,
looking at a distance like one compact mass, the visual angle not
permitting the ground to be seen." From this and other observations, W.
T. Hornaday has estimated that the herd referred to numbered not less
than 4,000,000 individuals. From the records kept by railroad companies
of the number of skins shipped over their lines and other evidences, it
has been computed that of the southern herd mentioned above over
3,500,000 individuals were killed during the years 1872, 1873, and 1874.
The northern herd seems to have been at least as large as the southern
one, so that the entire number on the Great plateaus in any one year for
the decade preceding 1870 was not less than 8,000,000, and even this
vast number seems to be an underestimate.
The great slaughter of the southern herd occurred from 1872 to 1874, and
of the northern herd ten years later. In 1889, as stated by Hornaday,
the bisons running at large in North America numbered but 635. In
1902 the number of bison in the United States was reported to be 800,
the increase being due to protection extended to the herds, and perhaps
also to a more accurate count.
_Fur-Bearing Animals._--Of the animals of North America which are taken
for their fur, the seal and sea-otter have already been referred to in
connection with the brief review presented of the life of the
continental shelf. As is well known, the colder regions of the earth are
the ones which yield the most valuable furs, and in the fur trade of the
world this continent, on account of its wide expansion at the north, has
taken the leading place as a producer. In fact, the fur trade is a
prominent feature in the history of America, and one whose followers
experienced great vicissitudes and countless adventures.
The animals that tempted the tireless and fearless sons particularly of
France, England, Scotland, and Russia to build their fortified
trading-posts throughout the subarctic forest from the St. Lawrence to
the Mackenzie and Yukon, were principally the beaver, sable, ermine,
fox, mink, wolverene, bear, otter, wolf, lynx, musk-rat, skunk, marmot,
etc. Nearly all of these animals are forest dwellers, and several of
them, as the beaver, otter, mink, and musk-rat, haunt the shores of
streams and lakes. Of the sable, there are two species, known as the
marten and the fisher. The bears are represented by at least four
species. The foxes number at least a dozen species, of which four are
especially prized for the beauty of their fur, namely, the arctic, red,
cross, and silver.
While the fur-bearing animals named above are characteristic of the life
of the boreal region of North America, a number of the species, and, in
fact, nearly all of them, range southward into the austral region,
especially in the more humid and generally forest-covered portions of
both the Pacific and Atlantic mountains, while one of the most important
as regards the beauty of its fur--the otter (_Lutra canadensis_),
frequently termed the land-otter, in order not to confound it with its
larger and far more valuable cousin, the sea-otter (_Enhydra
marina_)--reaches the torrid region and is still living in
Florida, and has been reported as occurring in Central America.
Of all the fur-bearing animals referred to above, the most valuable when
the total number of skins that have been taken is considered, and in
many ways the most interesting, is the beaver, of which but one living
species (_Castor canadensis_), closely allied to the beaver of northern
Europe, is known in America. Fully grown individuals are about 3 feet in
length, one-third of which is to be credited to the broad, flat,
scale-covered tail, and weighs some 50 or 60 pounds. The outer coat of
its pelage consists of rather coarse brown hair, beneath which there is
a fine, soft, dark fur, which makes its skin of commercial value. In
dressing the skins the hair is plucked, the fine fur beneath being
clipped to a uniform length and usually dyed. The formerly well-known
beaver hat was made from this fur, but in recent years silk has taken
its place. The importance of the American beaver is illustrated by the
fact that some 7,000,000 skins have been sold in London by the Hudson's
Bay Company since the year 1752. Not only is the fur of the beaver in
demand, but its flesh, and especially the muscles of the tail, are
prized for food by hunters and others who live the free, open-air life
of the frontier, although it is seldom exposed for sale in the markets
of cities.
The beaver is of interest to the geographer not only on account of its
wide distribution, which embraced the entire continent wherever the
willow, birch, alder, etc., on which it subsisted, could grow, from
northern Mexico to the Arctic Ocean, but for the reason that it made
more conspicuous and lasting changes in the minor features of the
surface of the land than any other mammal. One of its peculiar habits is
that it gnaws down trees frequently 6 or 8 inches in diameter, and after
cutting them into sticks a few feet in length, uses them in making dams
across small streams. These dams were built in thousands and tens of
thousands all through the forested regions, and being plastered with
mud, and still further enlarged and strengthened by the accumulation of
driftwood and leaves, held the waters of the streams in check and
caused them to expand so as to form small lakes, ponds, and swamps.
These beaver-dam lakes are common even at the present day, and many of
them which have been filled with sediment or drained furnish rich lands,
now utilized for gardens and cultivated fields. In Michigan these
beaver-dam lakes furnish the rich black soil so favourable for the
raising of celery and other vegetables. The beaver has disappeared from
all but the wilder and more inaccessible portions of the continent, but
the influence of the changes it made in the drainage of the land will
endure for many generations to come.
Of the fur-bearing animals mentioned above, none are more definitely
American than the skunks, or, to use a more felicitous name, _Mephitis_,
which ranges from central Canada to central Mexico, and is represented
by four or five species. As stated by Elliott Coues in his instructive
monograph on the North America _Mustelidæ_, the skunks are closely
related to the badgers, being heavy-bodied, short-legged, stout in
build, with hairy tails and generally loose pelage. They neither climb
trees nor swim in water; their gait is slow, and they do not allow
themselves to be hurried, even in the face of danger; their retreats are
burrows in the ground or dens in rocks and hollow logs, and sometimes in
the nooks and corners of dwellings and outhouses. Their most common
representative, _Mephitis mephitica_, is a beautiful animal some 15 or
20 inches in length, exclusive of its bushy tail, which is usually 12 to
15 inches long. The head is small, the ears low and short, and the hair
of a glossy black, relieved by conspicuous white markings which are not
only irregular in shape, but vary with individuals. The most marked
characteristic of the skunks is their ability to emit at will a fluid
which has the most disagreeable and sickening odour known. This fluid is
secreted in two glands, each about one inch in diameter, situated at the
base of the tail and opening into the rectum, but has no connection with
the secretions of the kidneys, and is probably seldom discharged except
when the animal is annoyed. It is a unique and most efficient
means of defence. In this connection it is to be remembered, however,
that the skunks belong to the family _Mustelidæ_, which is characterized
in part by the odoriferous secretions present in its various species,
but, above all others, the odours emitted by the genera under
consideration are the most dreadful. The stench produced by these
animals when startled or enraged is not only horrible beyond
description, but endures for months and even a year or more. The yellow
liquid which is ejected is squirted in a fine spray for a distance of
some 6 or 8 feet, but its odour may sometimes be perceived, even when
the wind is still, for a distance of a quarter of a mile.
The skunk having this one unconquerable means of defence from all its
enemies except man, exhibits evidence of degeneration in other respects.
When discharging its odoriferous fluid it faces its enemy, who is held
at bay or retreats, and hence, not being compelled to run, has acquired
a slow, wavering gait and deliberate movements; having no occasion to
ascend trees for safety, it has lost or failed to develop the ability to
climb; and its lack of other powers which are highly developed in its
near of kin may be used in illustration in a similar way. It is
practically removed from the attacks of enemies excepting dogs and other
canines and some birds of prey, but has to adapt itself to conditions of
climate and food supply. In winter in the northern portion of its
habitat it becomes more or less torpid, and during the coldest weather
usually hibernates, thus lessening the exertion required to procure
sustenance. When the temperature is not excessively low it seeks its
food, which consists of insects, birds' eggs, small reptiles, mice,
etc., and in settled regions visits the poultry-yards, and thus
increases the enmity extended to it by all mankind, who have ever been
disgusted by its odours. Another objectionable fact in reference to this
despised yet, we may perhaps say, respectfully treated animal, is that
its bite sometimes produces hydrophobia.
The skunks are not only widely distributed in North America, occupying
perhaps a larger area in the austral than they do in the boreal region,
but are influenced to a less extent by climatic and topographic
conditions than probably any other genera among our mammals. It lives
among mountains and on plateaus and plains, and in forests as well as on
the open prairies, and extends from humid regions like eastern Canada
and New England to the dry, semi-desert valley of New Mexico, and from
the cold shores of the Great Lakes and central Canada to the warm Gulf
States. Although offensive, and everywhere declared a nuisance, and
persecuted as such, as well as trapped and hunted for its pelt, its
range has been decreased but little since the settlement of the country
by Europeans, although its numbers are greatly reduced. Its beautiful
fur when deodorized and dyed of a uniform black is sold under the name
"Alaskan sable," "black marten," "American sable," etc., and is
extensively worn even by the most fashionably attired dames of every
land.
_The Bears._--Of the bears native to North America, as was stated by S.
F. Baird in 1857, the number of species is somewhat indefinite, but four
are commonly recognised and mention is sometimes made of two others.
This uncertainty as to the number of species of the genus _Ursus_, I
believe, still exists, and in itself is significant. If the bears have
not been satisfactorily classified, as is apparently the case, it
suggests that they exhibit great variations and that the drawing of hard
and fast specific boundaries among them is difficult, and perhaps
impossible.
The species which are usually recognised are the polar bear, the
grizzly, the cinnamon, and the black. Of the black and brown or cinnamon
bears there seems to be several varieties, some of which are perhaps
worthy of being considered species. On the other hand, it must be
remembered that Baird and others makes the cinnamon a variety of the
black bear. Again the grizzly and cinnamon intergrade in such a manner
that an experienced naturalist has considered them to be but extremes of
a single species.
The polar bear is distinguished from its kindred, at least in a general
way, by its large size and white or yellowish-white colour. These and
other differences from its relatives have led naturalists to place it in
a distinct genus, of which it is the only species. It is
circumpolar in its distribution, and in America occurs along the coast,
seldom travelling inland except during the breeding season, when it is
sometimes met with 25 miles from the ocean. Its southern range on the
Atlantic coast is in northern Labrador, but it is occasionally carried
on floating ice as far south as Newfoundland. It inhabits the shores of
Hudson Bay and the Arctic Ocean. On the west coast it reaches Bering
Strait, and is carried on floating ice to the islands in the northern
part of Bering Sea, and at rare intervals reaches the Pribilof Islands.
It is probably strictly carnivorous, and lives principally on the seal.
It is supposed to be the largest of the bear tribe, but is certainly
approached if not rivalled in size by the brown bear of southern Alaska.
As many arctic explorers testify, it is dangerous to man and will lead
in an attack.
The famous grizzly or "silver tip" inhabits the Pacific mountains, but
is best known in the Rocky Mountains and Sierra Nevada. Although like
all kindred species presenting conspicuous individual variations, it is
usually dark in colour, with white tips to some of the hairs. The pelage
is long, almost shaggy, and gives the animal even a more formidable
appearance than its great size and strength justifies. It is not only
one of the largest of the American bears, ranking in this respect with
the polar bear and the largest of the huge brown bears, but is also
probably the fiercest, and not infrequently has been known to attack
man, although it will usually retreat from the presence of human beings
if an opportunity is available. Full-grown individuals are about 8 feet
in length and weigh in the neighbourhood of 1,000 to 1,200 pounds.
The brown bear, of which there are perhaps three species, including the
Barren-Ground bear of the north-central part of Canada, are, as their
name signifies, of a brown or cinnamon colour, but present great
variation in this respect. Some are of a decided yellow, while others
become dark and are scarcely distinguishable from the true grizzly. They
reach a great size, particularly in southern Alaska, and possibly in
certain instances even exceed the polar bear in dimensions and
weight. The tracks of one which I measured near Mount St. Elias were 16
inches long by 8 inches wide, and the stride was 64 inches. The range of
the brown bear is confined principally to the Pacific mountains, but is
of greater extent than that of the true grizzlies and includes central
Canada.
The black bears are of almost continental distribution and occurred in
all or nearly all wooded districts before the balance of natural
conditions was disturbed by the coming of the white man. They are the
smallest of the bear tribe on this continent and are usually harmless,
but at times when attacked or approached suddenly, especially if
accompanied by their young, become formidable enemies. Their colour is
usually a glossy black, but much variation occurs, especially about the
head, and this and other differences are thought by some to indicate
specific distinctions. A seemingly well-marked variety occurring in
southern Alaska, which has a thick bluish-black under-fur, has recently
been described as a distinct species.
Near relatives of the bear are the racoons, of which several species are
present, one being abundant in the eastern portion of the United States
and the other in the Pacific mountains.
_The Cats._--The _Felidæ_ are represented by two genera, _Felis_ and
_Lynx_, each of which contains several species.
Of the true cats, the largest is the beautiful jaguar, or American
tiger, _Felis onza_, which is nearly as large, and by some said to be
equal in size to its Asiatic relative. It more nearly approaches the
leopard, however, in the character of its spots as well as in its
arboreal habit, but exceeds it in size. The jaguar is some 4 feet or
more in length to the base of the tail, and the tail is about 3 feet
long. Its general colour is a soft-yellowish passing into dark brown and
black, with large rosette- or somewhat lozenge-shaped spots, which take
the form of indefinite rings of dark fur with lighter centres, within
which there are one or two dark dots or eyes. The skins are fully as
beautiful as those of the tiger or leopard, and are highly prized for
rugs, and in some cases have been used for clothing. A dark,
nearly black variety (or perhaps more properly, examples of melanism)
has been described as a distinct species, and is sometimes spoken of as
the black tiger.
The centre of distribution of the jaguar is probably in the great
Amazonian forest, but it ranges over nearly all of South America,
throughout Central America, and extends northward to Texas and perhaps
Louisiana.
Next to the jaguar in importance is the widely known panther. Unlike
most of its relatives, this species has an essentially uniform colour.
The fur on the back, head, and tail is of a tawny brownish-yellow, but
varies somewhat with changes in seasons. The under parts are of a dirty
white. The animal when full-grown is of a formidable size, the larger
examples being nearly 5 feet long from the tip of the nose to the base
of the tail. The stout cylindrical tail is from 20 to over 30 inches
long. In spite of its size and great strength the panther is not to be
feared so long as room for its escape is open, as it is a great coward.
One of the most interesting facts concerning this species is its
unusually great range. Before being disturbed by white men it inhabited
practically the entire width of both North and South America, from
Hudson Bay to Patagonia, an extreme range of some 110 degrees of
latitude. It is most at home in the mountains and is seldom seen on open
plains. It is still common in the Pacific mountains of the United States
and Canada.
Of the smaller cats, several of which are beautifully marked, mention
may be made of the ocelot of the Texas region and the lynx or American
wildcat. The latter, of which there are at least three varieties, is yet
common, and maintains approximately its original range, which embraces
the entire width of the continent from the subarctic forest at least as
far south as northern Mexico.
_The Wolves._--In the history of the establishment of English colonies
in this country, and throughout the spread of civilization across the
continent, many accounts are given of encounters with wolves. These
stories as they have been handed down have probably in many instances
been magnified, but there is no doubt but that the larger wolves,
such as the gray timber-wolf, once common in the northern portion of the
United States, when assembled in packs and pressed by hunger, were
formidable antagonists.
Of the wolves, four species are usually recognised, but their great
variation, in each instance, has led to the description of numerous
varieties, some of which have by certain writers been given the dignity
of distinct species. The largest is the gray wolf, which is white or
grizzly gray in colour, and frequently 5 feet or more in length and
weighs 50 to 60 pounds. Individuals have been killed, however, which
exceed these measures. The range of this species, or group of species as
the case may be, was originally continental, but more particularly in
the forested regions. Its hair, which is frequently 4 inches or more in
length, and the fine thick under-fur make the skins valuable for robes,
but they are seldom used for clothing, except by the Indians and
Eskimos. The hood of the outer garment worn by Eskimos, termed a parkie,
is frequently fringed about the face-opening with the long warm hair of
the wolf.
A smaller species, the coyote, is still common on the western plains,
and is termed the prairie-wolf. It is a comparatively small animal,
although frequently 3 feet in length of body with a bushy tail
two-thirds as long, and is of a skulking, cowardly nature. Its colour is
usually a yellowish gray, and its skin, although used for robes, is much
inferior to that of the gray wolf. Its range is from northern Mexico
northward throughout the great plateaus, and in the valleys of the
Pacific mountains into Canada. It is usually the first of the larger
mammals the traveller in that region learns the existence of, even at
the present day. Several individuals frequently gather together just
after sunset and make their presence known by barking and howling in
concert. These serenades last but a short time, however, and are likely
to be repeated in the morning just before sunrise. During the night the
animals composing these bands seem to scatter and hunt for food
singly, but reunite in the early morning, after which they again
separate and seek secluded individual retreats.
_Brief Mention of Other Mammals._--In order to convey an adequate idea
of the large variety and richness of the North American mammalian fauna
far more space would be required than is at present available. Indeed,
of the smaller mammals much more research is evidently needed before
even the number of genera and species can be enumerated, much less their
life histories and economic importance made known, as is indicated by
the fact that a large number of species previously recognised has been
described during the past two or three years.
Of the abundant smaller mammals, none are more attractive or beautiful
than the arboreal squirrels, of which several species are widely known.
One of these, the common red squirrel, is remarkable for its wide range
and adaptability to a great variety of conditions. It is abundant in the
valley of the Yukon and even north of the arctic circle, throughout the
forest-covered portions of Canada, and as far south as the South
Atlantic States. Of less extensive range is the gray squirrel and the
black squirrel, common in New England, and the somewhat larger and yet
more beautiful fox squirrel of the central part of the continental
basin. There are also a large number of species of ground squirrels, and
several species of flying-squirrels. The rodents are also represented by
the marmots, certain species of which are exceedingly numerous near
timber-line in many of the ranges of the Pacific mountains as far north
at least as Mount St. Elias, and by gophers, chipmunks, lemmings, the
musk-rat, porcupines, rabbits, hares, rats, mice, etc. The list might
also be extended by enumerating the bats, shrews, and moles, but we are
compelled to cut short this most interesting portion of our review.
_Mammalian Families Peculiar to America._--While there are many genera
and species of mammals found only on this continent, the number of
families that are peculiar to it is small. Among the characteristic
families, most of which, however, extend into South America, none are of
greater interest in the study of geographical distribution than
the opossums, of which there are 3 genera and some 22 species, all of
them confined to the New World. Of these, two species are common in
North America: one, the Virginia opossum, abundant throughout the
eastern portion of the United States to the south of New York, and the
other and smaller species, which inhabits Mexico and extends northward
into southern California and Texas. Many representatives of this same
family occur in Central and South America, some of which are notable on
account of their diminutive size. The opossums are of peculiar interest
owing to the fact that they are the only representatives of the
marsupials now living outside of Australia. Fossil species occur,
however, in the Tertiary rock of Europe, so that the American forms
cannot be considered as indicating a recent land connection between this
continent and Australia.
The porcupines are also representative of the New World fauna, although
not strictly confined to it, and belong mostly in the northern
continent. The Canadian porcupine is found throughout nearly the entire
forested portion of the boreal region and extends as far south as the
Middle Atlantic States, and an allied species, but of larger size,
inhabits a portion of the same region and extends to the Pacific
mountains and occurs in Alaska.
The racoons are strictly American and inhabit both continents. They are
common in the forests of Central America and Mexico, and extend as far
north as central Canada.
Of the several families of smaller and less well-known mammals peculiar
to this continent, mention may be made of the pouched rats of
California.
All of the animals to which attention has thus far been directed are now
living; should one attempt to describe the great number of fossil forms
whose bones have been discovered in the rocks, the menagerie would be
vastly enlarged, and many exceedingly strange species, genera, families,
and even larger divisions of the animal kingdom, added to the extended
procession.
THE BIRDS
When one attempts to write an account of the birds of North America, the
heavens seem darkened with such a multitude of varied and beautiful
forms and the air filled with such a discordant clamour mingled with the
sweetest of music that failure to convey an adequate idea of the
countless numbers and diversity of the feathered throng within the
compass of a few pages must be recognised from the start.
The important place held by the birds of North America in the avifauna
of the world, may perhaps be best indicated by noting first of all what
orders and families are without representatives among them.
The orders under which the birds of the world are arranged in the scheme
of classification adopted by Wallace in his great work on the
geographical distribution of animals are as follows:
CLASS--AVES
ORDERS. EXAMPLES.
1. Passeres Includes the greater number of the smaller birds, such
as kingbirds, flycatchers, larks, jays, crows,
blackbirds, finches, sparrows, warblers, chickadees,
swallows, thrushes, etc., numbering in North America
some 328 species and many subspecies.
2. Picariæ Woodpeckers, cuckoos, toucans, kingfishers, swifts,
goat-suckers, humming-birds, etc.
3. Psittaci Parrots only.
4. Columbæ Pigeons and the dodo.
5. Gallinæ Grouse, pheasants, quail, jungle-fowl, turkeys,
guinea-fowl, etc.
6. Opisthocomi The hoazin of Guiana and Brazil only.
7. Accipitres Eagles, owls, vultures, hawks, buzzards, falcons, etc.
8. Grallæ Rails, snipes, plovers, cranes, herons, storks,
flamingoes, etc.
9. Anseres Ducks, geese, gulls, petrels, pelicans, penguins,
loons, auks, etc.
10. Struthiones Ostrich, rhea, cassowaries, emeus, apteryx.
Of these ten orders, all but two are abundantly represented in North
America. The missing orders include the ostrich-like birds, of which the
only species in the New World is the rhea, of the southern portion of
South America, and the peculiar hoazin, represented by a single
species found in Guiana and Brazil.
The eight orders under which the birds of North America have been
arranged (other classifications, however, have been adopted by various
naturalists) have again been subdivided into families, genera, species,
etc. According to Wallace's summary, the 8 orders referred to contain
124 families, of which 75 are not represented in North America to the
north of the lowlands of Mexico, while 47 families are present. Of these
47 families, 25 are essentially of world-wide distribution, and only 1,
containing a single species, a small wren-like bird of the genus
_Chamæa_, found in California, is peculiar to the fauna of the
continent.
As the North American continent under the arrangement adopted for the
series of books of which the one in hand forms a part, is considered as
including the West Indies, Mexico, and Central America, the above
summary does not represent its entire bird fauna, but presents, perhaps,
the best general idea of it that is at present attainable. To include
the birds of the tropical portion of the continent would add greatly to
the number of species, but I believe not materially to the number of
families and orders, as given above.
In reviewing the distribution of the land birds of North America to the
north of Mexico, but including lower California, J. A. Allen places the
total number of genera, as given in the check-list of the American
Ornithologists' Union, at 181. Of these, 55, or 30 per cent, are
circumpolar or otherwise wide-ranging Old World forms; 126 genera, or 70
per cent, are American, of which 35, or 28 per cent, are essentially
tropical, leaving 91 genera, or about 50 per cent, as distinctly North
American.
The number of species in the avifauna of the continent, according to the
latest check-list published by the American Ornithologists' Union
(1895), is 768, together with a large number of subspecies. If the
tropical portion of the continent were included, this number would be
greatly increased and possibly doubled.
A further generalization has been advanced by Allen, who states that in
the arctic portion of the continent the number of genera of birds
present during the breeding season is 65, of which only 5 are
exclusively American. In the cold temperate belt 120 genera are
represented, of which 98 are circumpolar and 22 American. In the warm
temperate belt 95 genera occur which do not range into the cold
temperate belt, and of these only 12 are Old World forms, while 83 are
exclusively American, and in addition 60 genera are common to both the
cold and the warm temperate zone, of which 46 are represented in the
fauna of the Old World, while 14 are American. This gives 155 genera for
the warm temperate zone, of which 58 are Old World and 97 exclusively
American. There are besides 50 essentially tropical genera which extend
into the warm temperate zone, of which 43 are American and 7
tropicopolitan. The avifauna of the warm temperate zone thus contains a
total of 205 genera.
The above enumeration indicates the rapid increase in the variety of
bird life met with as one travels from the arctic to the Gulf coast of
the continent, and in this connection it is to be remembered that the
land contracts in breadth towards the south. In number of individuals,
however, it is doubtful if there are less per square mile at the north
than at the south during the breeding season.
There is a decrease in the number of Old World forms inhabiting North
America from north to south. A similar decrease in mammalian species
common to America and Eurasia has previously been referred to, and the
same explanation applies in each case, namely, the near approach of the
land areas of the Old and the New World at the north, and the actual
union of the two continents in late geological time.
As has been shown by Allen, the species of birds of the temperate and
boreal zones of North America were derived in part from the Old World,
in part from types almost universally distributed throughout the warmer
latitudes, and in part from tropical America, but to a marked extent the
species present developed where they are now found. This
generalization is in harmony with the geographical relations of the
continent to other land areas, and with the fundamental principles of
evolution.
_Migrations._--Among the many facts of interest to the geographer in
connection with the bird life, none present a more fascinating field for
study than the annual migrations in which a very large number of the
species participate.
As one travels northward from Mexico or the Gulf States, the number of
species of birds which remain in essentially the same area throughout
the year, or the _residents_ as they are termed, becomes less and less.
In New England and about the southern shores of the Great Lakes there
are about 30 species which remain all winter and may justly claim to be
citizens. Besides these, there are several visitors that come from the
north and belong to the vast army of migrants, but which are contented
with a comparatively small change of position during the periods of
greatest cold or heaviest snow. In the far north the number of residents
is still more restricted. On the tundras fringing the arctic coast even
the snow-owls, snow-buntings, and the ptarmigans, the hardiest of birds,
move southward during the winter to the shelter of the subarctic forest,
and bird life on the vast frozen morasses is practically, if not
absolutely, wanting.
The millions of birds that journey southward each fall begin their
return migrations at the first promise of spring. Even during unusually
mild spells of weather in winter, temporary northward movements occur.
The migratory birds are actuated by such a strong desire to regain their
nesting places and summer homes that they embrace every opportunity to
journey towards them, and not infrequently suffer severely for the risks
they take. In some instances species which have begun their northward
flight too soon are killed by thousands owing to a return of severely
cold weather or die for lack of food.
The first definite northward migration in the southern portion of the
Mississippi Valley begins during exceptionally favourable years as early
as the end of January, but the great movement of the feathered
hosts is not usually at its height before the middle of March or the
first of April. In New England the current of migration begins between
the middle of February and the first of March, and increases in strength
until the middle of May, when it is at its height, and then rapidly
declines and is practically over by the beginning of June. In the far
north, the first arrival from the southward, and that a species which
does not make a long annual journey, usually appears early in April. At
Point Barrow, the most northern portion of Alaska, as was observed by
John Murdock in 1882 and 1883, the first harbinger of spring was a
snow-bunting, which arrived the first year on April 9th. The
northward-flowing tide of bird life ends early in July in the region of
the Yukon, and by the middle of that month the vast flocks have been
separated and the many mates have found their nesting places. The time
taken for the general movement is thus in the neighbourhood of four
months.
The northward flight of the birds is seldom, if ever, one continuous
journey, but like many other movements in nature, progresses by
pulsations. Well-defined "bird-waves" have been recognised especially in
the Mississippi Valley. The direct or immediate cause of the starting of
these waves of life is the coming of a wave of heat. Secondary or
modifying conditions are furnished by strength and direction of the
wind, cloudiness, rain, etc. As the weather in spring-time is fickle,
and its variations not the same for any two consecutive years, so the
gathering of the birds into flocks and their northward flights vary,
although for a term of years the arrival of a given species at a
particular station does not depart far from a mean date. With the
northward sweep of the waves of bird life over the temperate and boreal
portions of the continent comes the awakening of plant life, but the
birds, to a marked extent, precede the unfolding of the flowers. This
marvellous renewal of the life of the land after the long cold winter
makes the budding and nesting spring-time the most joyous portion of the
year, and one which exerts a marked effect on human thought and
activities. The spring-time awakening in all nature is like a
resurrection, and has apparently exerted an influence on the religions
of the world.
The bird-waves referred to above are characterized at the start by the
presence of great numbers of a single species, but as they progress,
scattering occurs, and at the time of the greatest movements in the
northern portion of the United States a large number of species
frequently arrive at a given locality in a single night. At sunset the
groves may be nearly tenantless and silent, while at sunrise they are
alive with the flitting of wings of many colours, and the air pulsates
with many different songs.
Judging from extended observations on migrations made in the Mississippi
Valley, the definite waves of bird life which sweep northward with the
spring-tide of temperature are in some instances 100 or 200 miles long
and have a breadth of perhaps a score of miles. The distance between the
waves varies with variations in the weather and perhaps other causes,
and as they progress they apparently become less definite and at the
north have yet to be recognised.
The migrations of the birds are performed principally at night. In the
northern part of the United States during the hours of darkness in early
spring, even when cloudiness prevails or the land is veiled in mist, the
voices of geese may frequently be heard overhead, proving that unseen
flocks are then winging their way northward. About the lighthouses along
the coast and on the shores of the Great Lakes, when migration is in
progress, dead birds are frequently found in considerable numbers and of
various species. In these cases the birds are evidently attracted by the
lights and killed on striking the windows that protect them. This occurs
particularly on stormy or cloudy nights, when the birds fly low. Several
of the larger species of birds, as the geese, ducks, cranes, etc., which
are strong of wing, make long flights without resting. In many instances
a single stage in a journey may include 500 or 600 miles. Most of the
smaller birds, however, fly comparatively short distances between the
pauses made for rest and food.
A species on reaching the northern portion of the route over which it
usually migrates scatters, and the individuals mate, nests are built,
and young reared. At the approach of cold weather reassemblage occurs,
frequently great flocks being formed, and the southern movement begins.
The southward migration is less conspicuous in most instances than the
movement _en masse_ of the birds in the spring, and so far as now seems
to be recognised is not divided into definite waves.
While the winter habitat of most birds in the temperate and boreal
portions of the continent is to the south of their summer homes, the
annual migration is not in all cases great in amount. Some species move
only a few hundred, or possibly a few score, miles. Even the winter
residents make short migrations, dependent on weather conditions. The
greater part of the migratory birds, however, pass the winter in the
Gulf States, Mexico, the West Indies, and Central and South America. In
some cases they go well to the south of the equator. The annual flight
going and coming measured in a straight line, between the nesting place
and the winter home, cannot be less in many instances than from 8,000 to
10,000 or 12,000 miles. An interesting fact in this connection is that
certain species follow definite routes. The region moved over annually,
if marked on a map, would resemble two open or partially opened fans,
with their handles pointing towards each other and connected by a narrow
band.
The causes of the annual migrations of birds have received much study
and been the subject of much speculation. The general consensus of
opinion in this connection seems to be that the birds are controlled
largely by what we in our ignorance term instinct. The true beginning of
the migration seems to be in the fall, when the birds are driven from
their homes by cold or, perhaps more accurately in most cases, by
scarcity of food. This, however, is not the whole story, since many
species start southward before cold weather approaches and while food is
yet abundant. Then, too, crippled individuals have been known to survive
the winter in regions from which their summer companions have
departed. Instinct, therefore, plays a part in even the fall migration,
where at first glance sufficient physical reasons may seemingly be
claimed for it. During the spring migration the birds are moved by a
strong impulse to regain their breeding-grounds. Each species seems to
have adapted itself to certain conditions of temperature, food, etc.,
through long ages of development, and acquired a subtle faculty of
regaining the environment to which it is best adapted, as soon as the
adverse conditions that caused it to leave its home are ameliorated. How
a particular bird is enabled to return to the nest it built the year
previous is not known. The study of the homing instinct of pigeons
assists in this direction, however, and suggests that birds are endowed
with something answering to a sixth sense--that is, a sense of direction
or of orientation.
_Spring-time Music._--The northward-flowing tide of life each spring
brings to the temperate zone of North America a marvellous change not
only in colour and movements, but in sound. This is the season of bird
courtship and more than usual happiness among the feathered millions.
From shore to shore of the continent a chorus more seductive than
sirens' songs pulsates on the breezes.
The winter is characteristically a season of silence. The sounds heard
at a distance from human habitations are mainly those produced by
inanimate nature. The wind causes varied discords amid the bare branches
of the deciduous trees or sings weird melodies in the pines. Strange
muffled roars come from the frozen lakes, as the ice contracts and
breaks during periods of excessive cold. The frost in tree trunks causes
sharp explosions. The ice-covered streams are still except where
cataracts interrupt their even flow. In the profound silence of a calm
winter night the distant dismal howl of a wolf, the cry of an owl, or
the bark of a fox alone reminds one that life still continues, but these
animate sounds are far more frequently absent than present. With the
coming of the spring there is a marvellous awakening and unfolding. The
brooks, swollen to overflowing by the melting of the snow, make
music as they run. The northward flight of the birds brings to every
grove a chorus of song. A host of batrachians and reptiles bestir
themselves after a long winter sleep and vociferously proclaim their
presence. The insect world, with its unnumbered legions, takes wing. The
air vibrates with millions of voices. The trees put forth their leaves,
each a harp-string which responds to the touch of the fingers of the
wind. The organ-notes of the thunder again startle the hibernating
echoes. As the winter is the silent season, so the spring is the time of
music.
One of the most charming of the many phases of nature's concert season
is the matin songs of the birds. Ere the eastern sky along the New
England coast becomes roseate with the first blush of morn, the twitter
of birds may be heard amid the shadowy branches of the trees. Soon a
thrush or a warbler awakens in full song, and is followed by a host of
other voices, until the air pulsates with music. As the sun rises and
his first level rays reveal the varied tints of the tree tops, the
many-voiced chorus passes the height of its ecstasy and the music
gradually subsides. But the glad tidings of the coming of the day are
passed westward from grove to grove and from meadow to meadow, and a
wave of song sweeps on ahead of the wave of light, induced by its
coming. The song-wave spreads to the north and south and flows steadily
westward over the forest-covered mountains, across the great central
basin of the continent, breaking on the treeless plateaus into many
streams which follow the grove-fringed rivers, passes through the
depressions in the Rocky Mountains, and although weakened in the arid
valleys beyond, is not checked. The larks there listen for its coming
and pass the joyful message westward. The timid dwellers in the great
forests of Oregon awaken at the magic sound and the lofty tree tops are
made to thrill with the voices of unseen choirs while it is yet night in
the silent aisles below. The onward rush of sound is not reflected or
turned back by the lofty Cascades, but flows through their passes and
only ceases when the sea-birds of the Pacific renew a note that
was dropped on the distant Atlantic coast.
One of the most fascinating incidents in the life of the explorer in his
lonely camps in the great forests or amid the solemn mountains is the
coming of the wave of song in the spring and early summer-time which
precedes and accompanies the rising of the sun.
* * * * *
The fascination of the field of study touched upon in this chapter
invites an attempt to present an account of some of the more
characteristic birds of North America, and to endeavour to convey to the
reader some idea of the varied reptilian, fish, and invertebrate life of
the continent, but the limitations of space prohibit such a review. Even
the great problems dealing with the intimate relation that exists
between geographical conditions and the distribution of animals cannot
be given more attention than the suggestions already offered.
LITERATURE
ALLEN, J. A. _The Geographical Distribution of Animals_, in
Bulletin of the United States Geological and Geographical Survey
of the Territories, vol. iv, Washington, 1878, pp. 313-377; _The
Geographical Distribution of North American Mammals_, in
Bulletin of the American Museum of Natural History, vol. iv, New
York, 1892, pp. 199-243.
HEILPRIN, ANGELO. _The Geographical and Geological Distribution of
Animals_. International Scientific Series, London and New York,
1897.
OSBORN, H. F. _The Rise of the Mammalia in North America._ New
York, 1893.
COPE, E. D. _Geographical Distribution._ In the Annual Report of
the Smithsonian Institution for the year ending June 30, 1898,
Washington, 1900, pp. 1199-1234.
MERRIAM, C. HART. _Life-Zones and Crop-Zones of the United
States_, United States Department of Agriculture, Division of
Biological Survey, Bulletin No. 10, Washington, 1898; _Results
of a Biological Survey of the San Francisco Mountain Region and
Desert of the Little Colorado, Arizona_, United States
Department of Agriculture, Division of Ornithology and Mammalogy
[Bulletin] No. 3, Washington, 1890; _The Geographical
Distribution of Life in North America_, in Proceedings of the
Biological Society of Washington, vol. vii, 1892, pp. 1-64.
CHAPTER VI
GEOLOGY
_Introduction_
In the preceding chapters an attempt has been made to present outline
sketches of the geography, fauna, and flora of North America as they
exist now. Yesterday, we may say for the sake of emphasis, there were
differences from what exists to-day in each of these great groups of
facts. That is, changes are everywhere in progress. With the recognition
of this idea comes logically the conclusion that similar changes must
have taken place in the past, and that the geography of the earth's
surface, and its flora and fauna, at no very distant time must have been
markedly different from what they are to-day. To test this hypothesis
the geologist studies the records preserved in the rocks in much the
same manner that the historian searches the papyri or the monuments of
Egypt to discover what changes in the affairs of men have occurred since
the days of the Pharaohs. The changes referred to are not essentially
different from those now in progress, but in reality the two are parts
of a single series. For a very long time there have been continents and
oceans, lakes and rivers, and the land has been diversified by mountains
and hills, plains and valleys, in the same general way as at the present
time. When once the idea is grasped that we are living in a geological
age, and that there is no break between the present and the past, it is
evident that the history of the past can be interpreted by means of the
results produced by known causes. Familiar formulas which express this
idea are: "The present is the key to the past"; "Geography is the
geology of to-day," etc. The forces or agencies which are now modifying
the earth's surface, such as the rending of rocks by changes of
temperature and the action of frost, erosion and deposition by streams,
the dash of ocean waves against the land, volcanic eruption, the
chemical action of organic acids, movements producing upheaval and
subsidence, etc., have been in action for geological eras, but their
intensity has varied from time to time and from place to place.
THE GROWTH OF THE CONTINENT
The geological history of North America is, in general, the same as that
of other continents, but claims attention in certain particulars,
largely for the reason that with the exception of Europe it has been
studied more thoroughly than any other comparable land area. In Europe,
throughout much of geological time, there have been numerous islands,
and as a large portion of the records of past changes which have been
presented were formed in the ocean, the results are complex. But in
North America there has been a comparatively steady growth from one main
continental centre or nucleus, and the records of the principal changes
that have occurred are, to a greater degree, simple. Not only in the
major features of the relief of the continent, as already described, but
in its growth and geological history, it is, so far as can be judged
from the present state of our knowledge of the various land areas, the
most typical of all the continents.
Changes in the outlines and area of a continent are brought about
principally by movements of elevation or depression in the earth's
crust. Of less importance is the erosion of the margin of the land by
waves and currents and the deposition of material brought from the land
by streams, together with the spits, bars, and embankments made by waves
and currents. By these and other and less conspicuous processes the
shape of North America has undergone numerous changes in outline and is
still being modified.
General maps have been prepared by J. D. Dana and others, showing the
outlines of North America at various stages in the course of its
development, and from a series of such maps recently compiled by D. C.
Schaffner those here reproduced (Fig. 33) have been selected to
illustrate the growth of the continent. As has been shown by various
geologists, the outlines of the present continents and ocean-basins had
their major features determined at a very early stage in the history of
the earth, and at a time preceding the existence of the oldest known
sedimentary rocks. At the close of the Archean, the earliest geological
era now recognised, and, so far as has been determined, before life
existed on the earth, the principal nucleus of North America was a land
mass some 2,000,000 square miles in area, situated mainly in what is now
the eastern half of Canada, from which there was a southward
prolongation represented by the Adirondack hills of New York (Fig. 33,
A).
The rocks forming this earliest known land in the Western Hemisphere
consist of crystalline schists, gneisses, and granite, which are
considered by some geologists at least as having resulted from the
metamorphism of sedimentary beds. Penetrating and intimately
intermingled with these greatly altered rocks, some of them perhaps
metamorphosed lavas and allied terranes, are many rocks that were forced
upward from deep in the earth into fissures in a molten condition and
have since cooled and crystallized. More than one epoch of metamorphism
has perhaps occurred, and the entire record now accessible is
exceedingly complicated.
The physical conditions at the earth's surface at the close of the
Archean period, as may reasonably be inferred, were not essentially
different from what they are now. The land areas were eroded by streams,
and the _débris_ carried to the sea and deposited, the coarser near
shore and the finer farther seaward. Upward movements in the earth's
crust in various places subsequently laid bare a portion of the
sea-floor adjacent to the former land, and the continent was enlarged.
The outline of the land as it existed previous to the upheaval which
exposed this portion of the ocean's bottom would be defined by the
landward margin of the material deposited. The exposed sediments
would be coarsest near the former coast-line and become finer and finer
seaward from it, and the fossils contained in the consolidated sands and
clays would also supply evidence bearing on the origin of the rocks. It
is by such interpretation of the ancient records in the light of what is
now taking place that the geologist is enabled to map approximately the
outline of North America at several stages in its growth in the manner
shown on the series of maps here presented. Information in this
connection, however, concerning both the northern and southern portions
of the continent is too meagre at present to be largely utilized in
these outline sketches.[5]
[5] The relations of the eras referred to on these maps and the
positions they occupy on the geological time-scale are shown a few pages
later on a chart of the geological history of North America.
The next system thus far recognised, following the Archean, is the
Algonkian, at the close of whose deposition some additions had been made
to the Archean or pre-Algonkian land. Succeeding the Algonkian system
come, in succession, the Cambrian, Ordovician, and Silurian systems. At
the close of the Silurian there was a decided increase in the size of
the main nucleus of the continent. Owing principally to an excess of
elevation over subsidence in the portion of the earth's crust beneath
the northeastern part of the region now occupied by the United States,
portions of the sediments deposited previous to the close of the
Silurian were upraised and important additions made to the extent of the
land southward from the Archean area of Canada. This "Appalachian
peninsula" would be conspicuous in a map representing the outline of the
continent at the close of the Silurian. The eastern margin of the
growing continent was then well to the eastward of its present position,
but how far beyond the present coast we have no means of determining.
Although at the close of the Silurian the continent had greatly
increased in area over that of the nucleus at the close of the Archean,
it bore but little resemblance to its present form. It is worthy
of note, however, that with the exception of the eastward extension of
the land at the time referred to, the growth had been within the present
continental outline.
A later stage in the growth of the continent is shown in Fig. 33, B,
when its eastern margin had much of its present general outline and the
Appalachian Mountains were in their prime. The time indicated is at the
close of the Paleozoic era, and after the great coal-fields extending
from Pennsylvania southward to Alabama and westward to beyond the
Mississippi were formed. The eastern half of the continent was
approximately completed at the time just referred to, and is older than
the western half.
During the Cretaceous period great changes took place in the geography
of the still growing continent, as may be seen by the map illustrating
that period. The conspicuous features in the geography are the submerged
Atlantic and Gulf borders, and the presence of a broad belt of ocean
water in the continental basin which reached from the then much expanded
Gulf of Mexico to the Arctic Ocean, and divided the land into an eastern
and a western continental island.
Following the Cretaceous period came the Tertiary period, during which
the continent assumed very nearly its present outline. During this
period, however, as is indicated in Fig. 33, D, the Atlantic border of
the United States from New England southward and a wide area about the
Gulf of Mexico, were submerged and had deep layers of sediment deposited
on them. During the Tertiary, bodies of fresh water became for the first
time a conspicuous feature on the land, and large lakes and broad
silt-depositing rivers existed particularly in the Pacific mountain
region of the United States, and at its close the continent was
practically completed as we now know it, but several important
oscillations, particularly at the north, have since occurred.
[Illustration: FIG. 33.--Maps showing the growth of the North American
continent.]
With the growth of the continent, briefly outlined above, came greater
and greater diversity in its relief, due principally to the
upraising of various mountains in a somewhat orderly succession from
east to west.
The oldest mountains on the continent are the Laurentian Highlands of
eastern Canada. Although the region referred to--the one mentioned above
as being composed of Archean crystalline rocks--is not now of sufficient
elevation or ruggedness to be termed mountainous, it shows in the nature
and structure of its rocks that deep erosion has taken place. The
inference is that truly great mountains have been removed, but the
evidence may also sustain the interpretation that slow upheaval has been
accompanied by erosion, and that at no time was the land conspicuously
elevated.
Next in age after the Laurentian Highlands come the mountains of New
England and the maritime province of Canada, which were upraised at the
close of the Silurian period. The next great step was the crumpling into
folds and upheaval of the rocks in the Appalachian region at the close
of the Paleozoic era. The Park and Stony Mountains were upraised at the
close of the Mesozoic era, and later came the Sierra Nevada and
Cascades, followed by the Coast Ranges. Youngest of all, and in part for
that reason the boldest and most lofty, are the magnificent mountains of
southern Alaska, with a host of sublime peaks, like Mounts Fairweather,
Logan, St. Elias, and perhaps McKinley. The last-named and highest peak
of all, however, may be of volcanic origin.
In the above list showing the progressive westward movement of the birth
of mountain systems, account is taken only of the elevations produced by
upheaval. The mountains due to volcanic eruptions, which are still
conspicuous, are all young, in comparison with the mountains situated to
the eastward of the Sierra Nevada. The majestic cones of the
northwestern portion of the United States, of which Mounts Shasta, Hood,
Adams, Rainier, Baker, etc., are the most glorious, are of Tertiary or
later age. The same is true, so far as known, of the still more lofty
volcanoes in Mexico. The "pine-tree" forms of steam rising from the
volcanoes of the Caribbees, Central America, southern Mexico, and
southwestern Alaska, proclaim the recency of the birth of the frequently
magnificent craters built of rocks that were once molten, from which
they emerge.
THE ROCKS OF WHICH THE CONTINENT IS COMPOSED
The rocks of which North America is built belong to three classes, which
are world-wide in their distribution. These are: First, rocks produced
by the cooling and crystallizing of formerly molten magmas; second,
those deposited by water; and third, those which previously belonged to
either of the two classes just referred to, but have been recrystallized
and so greatly changed that their preceding condition is no longer
clearly recognisable.
These three classes or subkingdoms, as perhaps they might be termed from
analogy with systems of biological classifications, are in technical
language:
1. _Igneous rocks_, such as the lava of Vesuvius.
2. _Sedimentary rocks_, such as sandstone, shale, limestone,
coal, etc.
3. _Metamorphic rocks_, such as gneiss, schist, some granites,
etc.
These major divisions are based principally on mode of origin, but do
not indicate relative age. While theoretically at least, and in a
general way, the rocks of these three great classes came into existence
on the earth in the order named, it is convenient to consider first
those of sedimentary origin.
[Illustration: PLATE IV.--Leading geological features.]
_The Sedimentary Rocks_ (Plate IV).--Whenever land exists or the waves
and currents of the ocean come in contact with the rocks denudation
occurs. That is, the rocks are broken through the action of mechanical
or chemical agencies, such as the friction of the gravel and sand swept
along by streams, the solvent power of water, etc., and the fragments
thus produced are removed principally through the action of flowing
water and deposited. Resulting from this general process of rock decay
and disintegration, combined with transportation and deposition,
there result mechanically formed sedimentary beds, such as shale,
sandstone, conglomerate, etc.; chemically formed sedimentary beds, such
as the deposits of springs, the saline precipitates from inclosed lakes,
etc.; and organically formed sedimentary beds, as, for example, peat,
coal, and limestone.
Since the first appearance of land in the region now occupied by North
America, sedimentary rocks have been in process of formation, and in
this way the growth of the continent, with the aid of movements in the
earth's crust, has been produced.
The superficial extent of the sedimentary beds in North America is very
great, as is indicated on the map referred to above. By far the larger
portion of the surface of the continent is underlain by them. Their
thickness varies from place to place, but probably reaches a maximum in
the Appalachian region, where a depth of some 40,000 feet has been
measured. Throughout the continental basin their depth is in general
from 3,000 to 4,000 feet. In the Pacific mountains their thickness
embraces tens of thousands of feet, and the same is true in Mexico,
Cuba, and Jamaica. These sedimentary rocks contain fossils which, with
comparatively few exceptions, show that they were deposited in the
ocean; thus sustaining in an important manner the conclusion already
presented in reference to the growth of the continent.
Great as is the area of the sedimentary beds at the present time, it
does not show the entire extent to which what is now land has at some
time been submerged beneath the sea. In certain broad regions,
sedimentary beds which formerly existed have been removed by erosion; in
other extensive areas they are covered by volcanic rocks, and in still
other portions of the continent, embracing thousands of square miles,
they have been metamorphosed and their original characteristics
obliterated.
The system of classification of the sedimentary beds that has been
adopted, as is well known, is based on the relative age of the
formations, determined primarily by the occurrence of one formation
above another, in regions where but moderate disturbances in
position have occurred. Many of the stratified rocks contain
fossils--that is, records of the life of the time they were deposited,
and after the order of succession of a large number of formations has
been ascertained, the life records they contain may be used as a means
of determining the age of a newly discovered terrane.
By grouping the information obtained from the study of the vertical
sequence of the formations in many regions, and also the records of life
contained in them, a composite geological column has been constructed
which shows the relative age of all known formations. The larger
divisions of such a scheme of classification are world-wide in their
application, but the smaller divisions are usually of restricted
geographical extent.
The scheme of classification of general application in North America is
shown in the chart on page 308. The arrangement is in order of age, the
oldest formation being at the bottom. There is some lack of uniformity
among American geologists as to certain of the terms used, more
especially in the lower portion of the column, and in part the scheme is
provisional, but in general it may be taken as expressing the progress
made in the study of the geology of North America up to the present
time.
The names of the larger divisions in this scheme of classification, or
those designating the groups and systems and the eras and periods, have
for the most part been adopted from European geologists. Two important
ones, however--namely, Archean and Algonkian--are of American birth.
While this scheme of classification is based on the succession of
sedimentary beds, igneous and metamorphic rocks have a place in it,
providing their age can be determined.
The Archean period includes the time previous to the deposition of the
oldest known sedimentary beds, and its lower limit is as yet undefined.
The Archean system, or the rocks formed during the Archean period, are
without known fossils, and consist largely of gneisses and foliated
schists, which are metamorphosed sedimentary or igneous terranes,
together with various eruptives. The typical area where these rocks are
exposed at the surface is in the Laurentian Highlands of eastern Canada,
the main Archean nucleus of the continent, but rocks of the same age and
same general character occur in several of the mountain systems of both
the Atlantic and Pacific cordilleras, and underlie the sedimentary beds
throughout a large part of the Continental basin. The Archean system was
named by J. D. Dana, and divided into two portions, namely, the
Laurentian below and the Huronian above. More recent studies, especially
by C. R. Van Hise, have shown the necessity of removing from the system
many of the terranes formerly referred to it, and of placing them in the
Algonkian. The Archean as it remains after this adjustment is termed by
Van Hise the _Basement Complex_. This term, although thus far not
generally adopted, has much to commend it, since the terranes designated
by it are highly complex, and may perhaps be ultimately subdivided into
two or more systems, and besides occupy a basal position lower than any
known sedimentary formation that has escaped metamorphism.
_Outline Chart of the Geological History of North America_
+----------------------------------------+-----------+-----------------+
| Rock-Scale. -->| Group. | System. |
| Time-Scale. -->| Era. | Period. |
+------------+------------+--------------+-----------+-----------------+
|Zoic time: | Time of | Time of |Psychozoic.|Human. |
|embracing | Mammals. | Palms and +-----------+-----------------+
|the history +------------+ Angiosperms. | |Pleistocene. |
|of the | +--------------+Cenozoic. +-----------------+
|earth since | | | |Tertiary. |
|the | Time of | +-----------+-----------------+
|appearance | Reptiles. | Time of | |Cretaceous. |
|of life. | | Cycads. |Mesozoic. +-----------------+
| +------------+--------------+ |Jura-Trias. |
| | Time of | +-----------+-----------------+
| |Amphibians. | Time of | |Carboniferous. |
| | | Acrogens | +-----------------+
| +------------+(Ferns, club- | |Devonian. |
| | Time of |mosses, etc.).| +-----------------+
| | Fishes. | |Paleozoic. |Silurian. |
| +------------+ | +-----------------+
| | +--------------+ |Ordovician. |
| | Time of | | +-----------------+
| |Molluscs and| | |Cambrian. |
| |Crustaceans.| +-----------+-----------------+
| | | Time of | |Algonkian. |
| +------------+ Algæ. | +-----------------+
| | | |Eozoic. |(As yet unknown |
| | Time of | | |pre-Algonkian |
| | Protozoa? | | |sediments.) |
+------------+------------+--------------+-----------+-----------------+
|Azoic time: preceding the dawn of life. |Azoic. |Archean or |
| | |Basement Complex.|
+----------------------------------------+-----------+-----------------+
| Solid Earth. |
| Prehistoric Molten Earth. |
| Gaseous Earth. |
+----------------------------------------------------------------------+
The Algonkian series embraces a great thickness of sedimentary beds, in
part metamorphosed, which in certain localities rest unconformably on
the eroded surface of the Basement Complex and in places are overlain
unconformably by Cambrian rocks. Both the upper and lower contacts,
however, in certain localities, have been rendered obscure by
metamorphism. The system derives its name from a tribe of Indians that
inhabited the region about the shores of Lake Superior, where it is well
developed. The Algonkian terranes are exposed in the Grand Cañon of the
Colorado, in the Wasatch and Uintah Mountains, the Black Hills of
Dakota, about the southern shore of Lake Superior, and in many parts of
eastern Canada, as well as in several other localities. The oldest known
fossils occur in these rocks, and consist of a small number of
brachiopods, molluscs, crustaceans, etc. These scanty records are
suggestive, and at least stimulate the hope that an extensive
pre-Cambrian fauna will ultimately be discovered. The few forms found
seem to be not far different from the similar life records of the
Cambrian.
The Cambrian system, although first studied in Europe, has an important
development in North America, and occurs at the surface at a large
number of localities ranging from Newfoundland to California. The known
distribution of the system and the nature of the rocks composing it
indicate that it occurs widely in the Continental basin beneath
subsequent deposits. The most interesting results derived from the study
of the Cambrian, carried on especially by C. D. Walcott, pertain to its
life records. With the exception of a few obscure algæ, all the fossils
thus far discovered are marine invertebrates. As regards rank in the
zoological scale, certain molluscan remains are the highest, but
outclassing them in size, abundance, and degree of specialization are
the _trilobites_, the nearest living representatives of which are
certain crustaceans. Of the trilobites about 100 species have been
discovered in the Cambrian rocks of North America, the largest
individual being about 20 inches in length.
The picture of the continent which the facts just referred to enables
one to sketch in fancy includes land areas destitute of animal life, and
probably without vegetation, except perhaps the lichens, the lowest of
the cryptogams. The sea, especially in its shallower portions near land
and over its surface, contains algæ, mostly, we presume, of small size,
in fact microscopic, and soft tissued. The animal life subsisting
primarily on the algæ are all invertebrates, and nearly all of them,
excepting the crustaceans, simple in organization. None of the animals
the remains of which have thus far been discovered had strong shells or
other well-developed protective or supporting tissues, thus indicating
that they were not subject to the attacks of formidable enemies.
As compared with later faunas, the animals of the Cambrian were
primitive, but their diversity--every subkingdom of invertebrates being
represented--is positive evidence that they were not the first
inhabitants of the waters. Considered from the point of view of
development, this fauna stands at least half-way, and some students of
the ancient history of the earth place it as far as nine-tenths of the
way, up the life column--that is, the time from the first appearance of
life on the earth to the beginning of the Cambrian was at least as long
and possibly nine times as long as the time that has since elapsed. This
is a sufficient promise that many records of life, and it seems safe to
predict as varied an assemblage of organisms as the at present
known Cambrian fauna, will ultimately be discovered in the Algonkian or
lower rocks.
The Paleozoic era witnessed the first appearance of vertebrate life. The
earliest known forms were fish-like in character and were succeeded in
sequence by batrachians and reptiles. In this connection the most
important contribution to the world's knowledge, from the study of the
American records, include the discovery of a large number of fishes, or
fish-like forms, some of them of gigantic size, in the Devonian and
Carboniferous rocks of the Ohio region, by J. S. Newberry; numerous
batrachians in the Coal Measures of Ohio, by E. D. Cope; of batrachians
and probably reptiles in rocks of similar age in Nova Scotia, by J. W.
Dawson and O. C. Marsh.
During the Paleozoic era land plants appeared, and before its close the
continent was densely clothed with forests consisting of flowerless
plants such as ferns and club-mosses, together with a less abundance of
trees related to the existing conifers.
Great additions to the world's knowledge of the varied and beautiful
floras of the swamps in which the coal-beds of Pennsylvania, Ohio, Nova
Scotia, etc., were accumulated have been made by H. D. Rogers, J. S.
Newberry, Leo Lesquereux, J. W. Dawson, I. C. White, David White, and
others.
The Mesozoic era is characterized among other events by the first
appearance and rapid development of flowering plants, the cycads being
especially numerous, and of our ordinary broad-leaved trees, such as the
oak, willow, sassafras, etc., and by the coming in of palms; and in the
animal kingdom by the culmination of reptilian life and the advent of
birds and mammals.
The American Mesozoic rocks have yielded a rich store of fossil plants,
as is well known from the painstaking studies of J. S. Newberry, Leo
Lesquereux, W. M. Fontaine, L. F. Ward, F. H. Knowlton, and others.
These same students of the progress of plant life on the continent have
also made extensive and critical studies of the Cenozoic floras.
The relics of reptilian life brought to light from the Mesozoic rocks of
New Jersey, Kansas, Wyoming, etc., by Joseph Leidy, O. C. Marsh, E. D.
Cope, and others, have astonished the world, even though marvellous
results in a similar direction had previously been made known in Europe.
The reptilian age was marked in America by the presence of such huge
reptiles, and by the strange development and adaptations in various
directions that they surpass the wildest dreams of fable. Lizard-like
reptiles walked the earth that were 40 to 60 feet in length and stood 10
to 14 feet high where the massive hind limbs joined the body. Their
thigh-bones in certain instances measured over 6 feet in length. Some of
these monsters, it is estimated, weighed at least 10 tons. These, the
hugest of all land animals, were vegetable feeders. Others, of less
size, although still gigantic and more active, were carnivorous. Some of
the old lizard-like forms which left their footprints in great abundance
in the sands now hardened into sandstone in the Connecticut Valley and
New Jersey walked on their hind feet, after the manner of birds, and
left three-toed footmarks, some of them 20 inches in length, which are
strikingly bird-like in appearance. Other great reptiles, whale-like in
appearance, inhabited the ocean. Yet more marvellous forms were provided
with wings, resembling those of bats, and in the case of the great
_Pteranodons_ found in the rocks of Kansas had a "stretch of wing" of
fully 20 feet. But the strange menagerie that has been resurrected
contains such a marvellous array of grotesque shapes that not even a
catalogue of the genera can be presented here.
While the Mesozoic era was emphatically the age of reptiles, the coming
of a more highly developed fauna was foreshadowed. Bird life was
represented, and the skeletons of reptilian birds, or birds with teeth
like those of reptiles, have been discovered in the Mesozoic rocks of
Kansas. Important additions to our knowledge of these strange creatures,
which furnish much instructive data in reference to the development of
the higher from the lower forms of life, have been made by O. C. Marsh.
The humble beginning of mammalian life is shown by insectivorous
marsupials, the jaws of which were discovered in the Newark system
(Lower Mesozoic) of North Carolina.
The Cenozoic era is the age of mammals, so called because during that
time brute mammals succeeded reptiles as the rulers of the earth. From
the rocks deposited in North America during this era, principally the
sediments of fresh-water lakes and the gravel-beds laid down by streams
in the Pacific mountain region, a great number of skeletons of truly
remarkable mammals, differing widely from anything now living, have been
discovered by Joseph Leidy, O. C. Marsh, E. D. Cope, H. F. Osborn, and
others. The profound interest attached to this fauna, and the bearings
it has on the study of the geographical distribution of animals,
climatic changes, etc., is indicated by the fact that it includes forms
related to the rhinoceros, elephant, camel, etc., which are not
represented among the animals now living on the continent, although
having relatives in other and principally tropical countries.
During the Psychozoic era mind gained ascendency over brute force, and
man became the leader. The mammals continued to dominate the earth
throughout the Pleistocene period and were then probably more numerous
and of even larger size than during the preceding Tertiary period.
During the Pleistocene great climatic changes occurred, and large
glaciers existed in several regions which now enjoy a temperate climate
and are densely populated.
The presence of man in North America during the Pleistocene has not been
proved, but important contributions to knowledge concerning the brute
mammals, and in reference also to the climatic and physiographic
changes, have been made.
In stream-deposited gravels, caverns, peat swamps, etc., over the
surface of practically the entire continent, the bones of many species
of large mammals have been obtained. These include the mastodon and
elephant, megatherium, megalonyx, mylodon, a large horse, a great bison,
an elk much exceeding the living species in size, a giant beaver,
and many others remarkable for their large dimensions as compared with
their living representatives. Several of these large animals survived
the vicissitudes of climate characteristic of the Glacial epoch, but
have since become extinct.
The chief contributions to Pleistocene history, however, made by
American geologists, are in connection with the records of climatic
changes. During the earlier portion of the period, and beginning perhaps
in late Tertiary time, the continent in large part at least was more
elevated than now and the energetic streams of the mountainous portions
eroded deep cañons. To this Sierran epoch, as it is termed, is referred
the excavation of the larger valleys of the Sierra Nevada, the
world-renowned cañons of the Colorado and Snake Rivers, and probably the
deep Valley of the St. Lawrence and the Hudson.
A climatic change perhaps initiated by the greater elevation of the
land, but not as yet wholly explained, caused glaciers to form about the
higher portions of a number of the ranges in the Pacific mountains, and
continental glaciers of the type of the ice-sheet now covering Greenland
to expand from at least three centres, termed the Labradorean, Keewatin,
and Cordilleran, in what is now Canada. During this time of great ice
accumulation and of glacial advance and retreat, or the Glacial epoch,
as it is termed, fully one-half of North America was buried beneath
ice-sheets of the continental type. A composite map showing the portions
of the continent which were covered with ice at one time or another
during the Glacial epoch is reproduced in Plate V.
[Illustration: PLATE V.--Pleistocene glacial deposits.
NOTE: This map presents what may be termed a composite picture
of the extent of glacial ice during Pleistocene and Recent
time; Greenland, much of the Arctic archipelago, and many areas
in the Pacific mountains are still occupied by ice. The broken
blue lines on the Atlantic and Pacific coasts show
approximately the seaward extension of the Pleistocene
ice-sheets. The detached areas of glaciation in the western
portion of the United States are here assigned to the Wisconsin
stage, but in the Rocky Mountains and Sierra Nevada there are
records of two ice advances. The drift in western Canada here
colored as Wisconsin is perhaps in part of later date.]
During the maximum advance of the ice from the Labradorean centre into
the Continental basin it nearly reached the mouth of the Ohio River
(near Cincinnati). An earlier advance from the Keewatin centre extended
to the Missouri River in Missouri. There is evidence of a succession of
advances and retreats of the ice forming a very complex history. With
its final retreat the Great Lakes came into existence and the continent
reached the stage in its development when man became prominent.
The study of glacial geology in North America was initiated, or at least
given a fresh start and in the proper direction, by Louis Agassiz, and
within recent years energetically carried forward by a large number of
earnest workers. The stage of advance reached in this branch of geology
which serves so admirably to link the present with the past is well
presented in the numerous publications of T. C. Chamberlin and his
associates.
The instructive history of the growth of North America and the
successive appearance of higher and higher forms of life, the records of
which have been discovered in the sedimentary rocks, has been made known
by the combined studies of a large number of investigators, but the
great task has been carried on mainly under the auspices of various
national and State surveys. Chief among these is the present United
States Geological Survey, which has published what may be justly termed
a library of valuable literature and of topographic and geologic maps.
_The Igneous Rocks_ (Plate IV).--Under the at present popular
explanation of the origin of the earth, namely, the nebular hypothesis,
and also the modification of it termed the meteoric hypothesis, the
planet itself is considered to have been at one time in a molten
condition. The starting-point of the study of the rocks composing the
earth should be, therefore, the primitive crust cooled from fusion. In
addition to this there have been throughout history geologic migrations
of molten matter from deep within the earth towards the surface, and a
part of the material thus forced outward, principally through fissures,
has cooled in the rocks it penetrated, forming intrusions of various
kinds, and a part has reached the surface and been extruded, as during
volcanic eruptions.
Probably every known phase of vulcanism is illustrated by the igneous
rocks of North America, and in certain branches of the subject, as the
nature of intrusions and the changes which occur in the cooling of
igneous magmas, marked advances in the world's knowledge have been made
by American geologists.
Examples of volcanic phenomena on a grand scale are furnished by the
still active volcanoes of the Caribbees, Central America, Mexico, and
Alaska. Between southern Alaska and south-central Mexico there are no
active craters, but a large number of volcanic mountains in various
stages of erosion which form an instructive series illustrating the
internal structure of the mode of accumulation of ejected fragment
material and of lava-flows. In this series of mountains built by igneous
agencies belongs the great volcanic piles of the Cascade region, of
which Mounts Baker, Rainier, Adams, Hood, Jefferson, Mazama, Shasta,
etc., are among the leading examples. Many other illustrations in the
same connection, some of them in an advanced stage of erosion and now
revealing only the dikes and necks of resistant rock that cooled and
hardened well below the surface, occur widely throughout the southwest
portion of the United States. The still recognisable volcanic mountains
of the continent, with the exception of those of the Caribbees, are
confined to its western half, and with the exception of certain almost
perfect craters in eastern New Mexico are all within the Pacific
mountains. A great belt of volcanoes, including a large number of both
active and extinct examples, extends from Panama to the Aleutian
Islands, a distance of some 7,000 miles, and is a part of the so-called
"circle of fire" surrounding the Pacific Ocean. This belt is about 1,000
miles broad in its central part, where only extinct volcanoes exist, and
narrows towards both its northern and southern extremities, which are
defined by still steaming craters. The narrow northern portion,
inclusive of the active volcanoes of the Alaskan Peninsula and the
Aleutian Islands, is prolonged westward, and forms a curve concave to
the southward, while the equally narrow southern portion marked by the
energetic craters of Central America forms a curve concave to the
northward. The entire belt has something the shape of a sigmoid curve,
with a wide central portion.
In the preceding sketch of the growth of the continent it was shown that
the Pacific mountain region is younger than the Atlantic mountain
region. In this same connection certain interesting general conclusions
have been reached in reference to igneous activity. In each of the great
cordilleras referred to there have been extensive breaks in the earth's
crust through which molten rocks have been forced upward. Volcanoes and
various intrusions have been formed in each region, but in the eastern
half of the continent the time since the last eruptions has been so
great that all evidence in the relief of the land of the former presence
of volcanic mountains has been obliterated. Erosion has cut deeply into
the rocks on which the ancient volcanoes stood, and revealed in some
instances the dikes occupying the fissures which supplied them. A large
number of dikes of igneous rock occur in the Atlantic coast region from
Prince Edward Island southward to Alabama and Georgia, and vast
lava-flows of ancient date are still preserved about the south shore of
Lake Superior. Volcanic eruptions in the older half of the continent
have long since ceased and the breaks which gave them existence have
been healed. The later movements in the western half of the continent
have caused fresh fractures to form, through which molten matter has
been forced to the surface. Many facts have been observed in each region
which show an intimate connection between movements in the earth's crust
which have produced fractures and the distribution of volcanoes.
The lavas poured out by the more recent volcanoes of North America are
mainly dark basic rocks, among which basalt predominates. An exception
occurs in the case of the Mono craters near Mono Lake, California, which
in recent time extruded a thick, viscous, highly siliceous, rhyolitic
lava, much of which cooled quickly and formed volcanic glass or
obsidian.
In addition to streams and sheets of lava, many volcanoes, and
especially those in a state of explosive eruption, blew into the air
quantities of fragmental material, such as scoria, bombs, volcanic
gravel (lapilli), dust, etc., which was scattered far and wide over the
land. More or less extensive sheets of this material, in many instances
interstratified with sedimentary beds, and especially with the
strata laid down in Tertiary lakes, or separating lava-flows, occur
widely throughout the Pacific mountains. Dust showers of the nature just
referred to have occurred at a recent date, and the fine white material
that fell is now found at the surface in a large number of localities,
ranging from Central America to the Yukon Valley and from Kansas and
Nebraska to Oregon and Washington.
The most remarkable instance of the addition of volcanic rocks to the
surface of North America is in the case of the Columbia River lava,
which covers some 200,000 or more square miles of country in Washington,
Oregon, and neighbouring States. In that region outwellings of highly
liquid rock came from fissures and spread widely over the surface as
veritable inundations, which on cooling became black, basaltic rock, but
without forming mountains or craters. Where the Snake River has
excavated its magnificent cañon in these still horizontal layers of
basalt, a thickness of 4,000 feet is revealed, although the stream has
not as yet cut through the formation, and in Stein Mountain, Oregon, a
similar series of lava-sheets over 5,000 feet thick has been measured.
The Columbia River lava was spread over the surface of a deeply eroded
land in a series of vast overflows of molten material. The liquid rock
covered the broad plains and extended into the valleys in the adjacent
mountains, giving them level floors of basalt. Mountain spurs became
capes and headlands and outstanding buttes were transformed into islands
in the molten sea. The lava since cooled and crystallized has in places
been folded and tilted; streams like the Columbia, Snake, Spokane
Rivers, etc., have carved great cañons in it, and the surface,
especially where it is still nearly horizontal, has decayed and yielded
a wonderfully rich soil. It is the fine, rich residual material of these
lava plains, redistributed in part by the wind, which furnishes the
basis for the immense wheat industry of the northwestern portion of the
United States.
The extrusion of molten rock from deep within the earth so as to form
volcanoes or fissure eruptions at the surface is only a part of a widely
extended and highly varied process. As geologists have discovered,
particularly in deeply eroded regions, by no means all of the fissures
which permit of the forcing upward of molten material in them reach the
surface. Many of them died out before coming to the light and favoured
the production of various forms of intrusion.
A fissure originating deep in the earth's crust and extending upward,
perhaps with many branches and irregularities, if injected with molten
rock from below gives origin to dikes. That is, a dike is a more or less
vertical sheet of igneous rock which has cooled and crystallized in a
fissure. Such sheets of intruded material cutting across the bedding of
stratified rocks, or traversing older igneous or metamorphic terranes,
are of common occurrence and are frequently abundant in deeply eroded
regions. They occur particularly in mountains of upheaval, thus
demonstrating the fact that to a large extent the fissure which became
injected with molten magmas and perhaps gave origin to volcanoes, are
due to movements in the rocks composing the earth's crust. The force
which causes molten rock to rise in such fissures also tends to prolong
and enlarge them. The heat of an intruded magma affects the rocks it
traverses and produces what is termed contact metamorphism. Examples of
dikes in the Newark system have already been referred to, and others are
common throughout the Pacific mountains. Where the Columbia River lava
in central Washington has been removed by erosion, hundreds, and in fact
thousands, of dikes are exposed in the terranes on which it formerly
rested.
When a dike ends above in horizontally bedded rocks it sometimes happens
that the injected magma, especially if highly fluid, is forced in
between the strata and spreads widely between the layers, forming an
intruded sheet, which lifts a broad cover to a height equal to its own
thickness. An example of an intrusion of this nature is furnished by the
palisade trap-sheet in New Jersey and New York, which has a maximum
thickness of about 1,000 feet, and is fully 100 miles in length from
north to south. The portion which remains is but a remnant and is
seldom over 2 or 3 miles wide. This sheet in common with its associated
sandstones and shales has been tilted so as to dip westward at an angle
of about 15 degrees, and its eastern border eroded so as to form the
picturesque Palisades on the west bank of the Hudson opposite New York
city. Many other similar intruded sheets are known in Nova Scotia, the
Connecticut Valley, among the Pacific mountains, etc.
A marked variation in the process just outlined occurs when, as the
controlling condition, the intruded magma is highly viscous instead of
highly fluid, and the friction of contact and of flow is greatly
increased. Under such circumstances the intruded magma expands less
widely than is the case when an intruded sheet is formed, and a thick
intrusion results, which lifts a small cover perhaps to a great height.
Intrusions of this nature are sometimes expanded in their upper portions
into a more or less mushroom shape, and from their fancied resemblance
to cisterns of once molten rock within older terranes have been termed
_laccoliths_. The typical examples are furnished by the Henry Mountains
in southern Utah, described by G. K. Gilbert. Other similar intrusions
in Colorado have been studied by Whitman Cross, and yet other examples
have been discovered in various parts of the Pacific mountains. In the
case of certain of the laccoliths in the Henry Mountains, now laid bare
by erosion, the cistern-like mass of intruded material is 12,000 feet or
more in diameter, some 5,000 feet thick in the central part, and lifted
a cover of stratified rocks fully 7,000 feet thick.
Where a dike ends above in older rocks, and particularly in horizontally
stratified sedimentary beds, in a pipe-like form, similar to the conduit
of a volcano, but without reaching the surface, the unexpanded or but
slightly enlarged summit portion lifts a comparatively small cover into
a dome, and what has been termed a plutonic plug results.
All the various phases of intrusions thus far referred to, it will be
readily seen, are variations of one process. The wide range in
the results produced are dependent on local conditions, either in
respect to terranes invaded, as, for example, whether or not they are
undisturbed sedimentary beds, and on the physical condition of the
intruded material, in reference especially to its degree of viscosity.
There is an intimate and even a genetic connection between intrusions on
the one hand and volcanic and fissure eruptions on the other. If
fissures lead from portions of the earth's crust sufficiently deep to
permit the rocks to become plastic or fused on account of the relief of
pressure due to the opening of the fissure, the magma may be forced to
the surface, becoming more and more plastic or more perfectly fluid as
the weight upon it decreased, and volcanic phenomena result; or if the
fissure fails to reach the surface intrusions of various forms may be
produced. The simplest form of intrusion, the dike, results under
whatever condition the summit portion of the magma comes to rest. A
magma forced upward in fissures in the earth's crust may meet moist
rocks or even reservoirs of water, and in such instances steam or gases
are produced and a new force is added, which may produce explosions.
In addition to the intrusions of the various classes just referred to
there are others on a far larger scale, examples of which occur in North
America, but as yet their mode of origin has been but little studied. I
refer to vast upwellings of molten or plastic material beneath the more
rigid portions of the earth's crust, which elevate domes, perhaps 200 or
300 miles or more in their various horizontal diameters. The great areas
occupied by intrusive granite, as the one from which the Bitter Root
Mountains in Idaho have been sculptured, are of this nature. These
"regional intrusions," as they may be termed, elevate mountains in the
same general manner as in the case of laccoliths, but of far greater
size. To the elevations produced in this manner I have ventured to apply
the name _subtuberant mountains_, in expression of the idea that they
have resulted from vertical uplifts, due to the upswelling of molten
material beneath.
_The Metamorphic Rocks_ (Plate IV).--At the contact of either
sedimentary or igneous rocks with intrusive rocks of whatever form, such
as dikes, sheets, laccoliths, etc., there has been in many well-known
instances an alteration of the terranes penetrated or uplifted which is
most intense along the contact and diminishes at a distance. This change
or metamorphism, as it is termed, consists of an alteration in the
colour, texture, hardness, mineral and chemical composition, etc., of
the rocks affected, and may be manifest throughout a thickness of but a
few feet, or perhaps only a few inches, but near large intrusions is apt
to be traceable for scores or hundreds of feet. In the case of intense
contact metamorphism, the altered rock assumes a new form, and may
exhibit a crystalline and foliated or schistose structure. The changes
referred to are most marked when water is present, and are thought to be
due largely to the influence of heated water percolating through the
rocks and producing changes by solution and deposition. The principal
agencies which take part in contact metamorphism are heat, heated
waters, pressure, and perhaps movements within the rocks.
There are extensive regions throughout which the rocks have been changed
in a manner similar to the alterations commonly found adjacent to
igneous intrusions which, in general, have been brought about in some
other way. This regional metamorphism, as it is termed, has affected the
rocks in certain instances throughout districts measuring many hundreds
of square miles in surface extent, and with a vertical range of many
thousands of feet. The rocks referred to have been changed without
fusion from a previous condition, during which they were either
sedimentary beds or cooled and crystallized igneous magma. This
conclusion has been verified in numerous instances by tracing the
thoroughly altered rocks to regions where the change has been less
intense and finally to where they pass by insensible gradations into
easily recognisable sedimentary or igneous terranes. Common examples of
metamorphic rocks are mica, schist, gneiss, statuary marble,
certain granites, etc. These rocks frequently have a foliated or fissile
structure, such as it is presumed would result from a flowing movement
within the mass while under great pressure. Characteristically also the
rocks are composed of interlocking crystals or portions of crystals,
which are not contained in a glassy base, as is the case with most rocks
that have crystallized from fusion. That is, the metamorphic rocks are
characteristically _holocrystalline_, while igneous rocks are
_porphyritic_, or _cryptocrystalline_.
The analogy between rocks altered by contact metamorphism and those
affected by regional metamorphism had led to the conclusion that the
latter, like the former, have been changed by heat and the passage
through them of heated water bearing mineral matter, and especially
silica, in solution. More than this, the foliation frequently so
characteristic of metamorphic rocks is considered as evidence of a
flowing movement or shearing of the material while under pressure. In
short, rocks are altered by heat, especially if water is present in
them, by motion, and by chemical changes produced by percolating waters,
and perhaps in still other ways. The degree of heat required is not
definitely known, and probably varies according to the nature of the
rocks, the presence or absence of water, etc., but is certainly less
than that necessary to produce fusion, and is thought, in general, to be
in the neighbourhood of 750° F. While heat alone is considered as
sufficient to produce metamorphism, it is probable that in most
instances two or more of the agencies just referred to have been in
operation at the same time. In the case of the foliated rocks motion
within the mass seems to have been the predominating factor, and
dynamical metamorphism is considered as important as heat metamorphism.
In North America, as is indicated roughly on the map forming Plate IV,
metamorphic rocks occur at the surface over a great region in eastern
and northeastern Canada, in Labrador and Newfoundland, in the New
England States, and thence southward along the eastern side of the
Appalachians. Other extensive regions occupied by similar rocks
occur in many of the ranges of the Pacific mountains, from Alaska to
Panama, and are known in the West Indies.
Not only do the metamorphosed rocks outcrop at the surface over large
areas, but, as may be inferred from such outcrops, as well as from the
records of numerous borings, underlies nearly the entire extent of the
sedimentary formations. The basal portion of the continent, with the
exception of certain areas where igneous rocks occur, is formed of
metamorphosed terranes. So generally is this true, that it is safe to
say that if a boring is begun at any locality on the continent where
sedimentary beds occur, and is continued downward until the sedimentary
rocks are passed through, metamorphic terranes will be found beneath.
The same is true also where the surface is composed of lava-sheets. The
exceptions, where metamorphosed rocks do not occur beneath sedimentary
or volcanic beds, are when igneous intrusions or ancient lava-flows are
present at a depth.
In the brief description given of the Archean system on a preceding
page, it was stated that the rocks composing it are largely metamorphic.
But rocks of practically any age may be altered in the several ways
mentioned above, and the resulting gneisses, schists, etc., be
indistinguishable from those of the Archean. In fact, some of the
metamorphosed rocks of North America, as certain gneisses, schists,
etc., of the Sierra Nevada and Cascade Mountains, are known to be of
Mesozoic and even Cenozoic age.
In speaking of the growth of North America, and again in connection with
the distribution of volcanic mountains, it was shown that there has been
a progressive migration of the field of action of the forces which
upheave the rocks so as to form land areas, and also of the movements in
the rocks which produce fractures and lead to the origin of volcanoes.
In a similar way the sphere of influence of metamorphism as indicated by
the age of the transformed rocks in various regions has in a general way
migrated from east to west across the continent.
In the Laurentian Highlands the metamorphosed rocks are of pre-Cambrian
age; in New England and the Appalachian region they are, in part at
least, of Paleozoic age; and in the Sierra Nevada and Cascade Mountains
metamorphosed Mesozoic and Cenozoic rocks occur. As movements in the
outer portion of the earth's crust may produce fractures in any class of
rocks, and as such fractures favour the intrusion of igneous material,
the metamorphic rocks may contain igneous intrusions similar to those
noted above in connection with sedimentary rocks. As the stratification
so marked in sedimentary beds is lacking in metamorphosed rocks, it is
not to be expected that intrusions will take the form of sheets,
laccoliths, etc., but rather appear as dikes with perhaps irregular
branches. As the same region may experience two or more periods of
metamorphism, it is evident that great complexities may arise, as, for
example, when a metamorphosed terrane is penetrated by dikes and
irregular intrusions and again subjected to metamorphosing conditions.
These considerations lead to the suggestion that rocks metamorphosed in
pre-Cambrian time, for example, would be apt to be more complex than
those of Mesozoic date. In general, this has been found to be true, as
is suggested by the fact that to the pre-Cambrian metamorphosed
terranes, as previously stated, the name Basement Complex has been
applied.
_Summary._--The relation of the three great divisions into which the
rocks composing North America, in common with all other portions of the
known lithosphere, are divided, may perhaps be better understood when it
is remembered that the igneous rocks came _from below_ in a molten
condition; that the sedimentary rocks have been formed _at the surface_
from the _débris_ of either igneous, metamorphic, or previously formed
sedimentary beds; and that metamorphic rocks have been produced _within_
the earth's outer crust by the alteration of either igneous or
sedimentary rocks. When the heat which produced certain phases of
metamorphism is sufficiently increased, greater freedom of molecular and
chemical changes occur and the material acted on passes to the
condition of an igneous magma. The three great classes of rocks
considered above are thus seen to be but stages in a cycle which the
material of the lithosphere passes through.
The conditions which bring about these changes are still in action and
are intimately associated with movements in the rocks of the earth's
crust. When elevation raises a portion of the earth's crust above
sea-level, erosion and redeposition ensue and sedimentary rocks are
formed; the greater the elevation the more energetically the forces act
which bring about denudation, transportation, and sedimentation. When
depression occurs of sufficient amount to carry rocks previously at or
near the surface into the zone of metamorphism, alterations follow, and
in general the deeper the depression the greater the changes until
metamorphism culminates in fusion, providing pressure does not
counteract the influence of heat. Dynamical and chemical metamorphism
may occur at less depth than purely heat metamorphism, and it may be
presumed takes place in the axes of mountain ranges, even above
sea-level. Such a broad view of the relations and genesis of the three
great lithologic divisions of the material forming the earth's outer
crust is necessary to the understanding of the conditions observed in
the basal portion of the geological column, as it is termed, in which
the age and order of succession of the sedimentary rocks is indicated.
In certain localities, for example, the Cambrian rocks rest
unconformably on a surface of metamorphic and igneous rocks--that is,
the Basement Complex was raised above sea-level, eroded and subsequently
depressed before the Cambrian sediments were laid upon it. In other
localities the Cambrian rocks pass indefinitely into metamorphosed
terranes beneath, which means that metamorphism invaded the series after
the deposition of the Cambrian, and the characteristics of its junction
with older rocks was obliterated. Similar relations may evidently be
discovered at any horizon in the geological column. Obviously the
chances of a system of stratified rocks becoming metamorphosed or of
being removed by erosion, are greater the nearer their position
to the base of the sedimentary series; in a similar way the chances of a
sedimentary terrane becoming invaded by igneous intrusions is greater
the greater its age; again, the older a sedimentary terrane the greater
the chances of its becoming buried by subsequent deposition and the less
the likelihood of its being exposed for study. The only position in
which a sedimentary formation can maintain its integrity and be safe
from destruction by erosion or transformation by metamorphism is below
sea-level and above the zone of heat metamorphism; but even in this
position it may have its distinctive features, including its fossils,
obliterated by dynamical and chemical alterations. These suggestions are
offered for the sake of indicating, as stated on a previous page, that
the Cambrian and Algonkian rocks should not be considered as the first
formed sediments, and that there is hope of the discovery of a rich
fauna of older date than any at present known. In the search for the
earliest evidence of animal life on the earth, North America holds out
favourable conditions.
THE CONCENTRATION OF MINERAL SUBSTANCES
The most important branch of geology treats of the substances in the
earth's crust that are of direct service to man, as, for example,
building stones, coal, iron, petroleum, gold, etc. Only a glance can
here be given at the conditions which have led to the origin of the
materials of commercial value and to their geographical distribution.
From the mode of origin of the principal classes of rocks it may be
reasonably inferred that certain minerals and ores will be developed or
concentrated in one class of rocks and not in the others. To a great
extent the facts observed during the development of mines, etc., sustain
this prediction.
In the cooling and crystallizing of igneous rocks from a state of fusion
many minerals are formed, the most common being silicates of the
alkaline earths, which are usually inclosed in a glassy or
cryptocrystalline base. The igneous rocks have characteristically
a highly complex chemical composition, and although frequently
containing the metallic element, etc., which are of economic importance,
these are widely disseminated, and in nearly all cases in chemical
combinations, as the minor ingredients of siliceous minerals. Although
the igneous rocks sometimes contain valuable ores, they are in many, if
not all instances, due to secondary enrichment and are not a result of
primary crystallization from fusion. As all the material of the earth's
crust was at one stage in the series of changes it has experienced
consolidated from fusion, it follows that the ores and minerals now of
economic value did not then exist, or were widely diffused and have
since been formed or concentrated.
The processes of concentration referred to are carried on in various
ways through the agency of mechanical, chemical, vital, molecular, and
electrical forces, acting singly or in association. For example,
concentration through the action of mechanical agencies is illustrated
by the manner in which rocks are reduced to fragments in the every-day
process of denudation and the resulting _débris_ removed by streams and
redeposited. In this process an assorting in reference to size, specific
gravity, etc., takes place, and certain substances, as sand, for
instance, is accumulated in one locality, and certain other substances,
as clay, deposited in another locality. During this process gold,
platinum, etc., owing to their high specific gravity, may be
concentrated in stream channels. The accumulation of mineral matter
through the action mainly of chemical agencies, occurs when the waters
percolating through rocks dissolves certain substances, as calcium
carbonate, for instance, and on coming to the surface as springs, or
dripping from the roofs of caverns, deposit calcareous tufa,
stalactites, etc. Silica, iron, manganese, and other substances are
frequently concentrated in a similar manner.
Concentration of previously widely disseminated substances principally
through the agency of vital forces, is illustrated by the manner in
which molluscs and polyps obtain calcium carbonate from water and
deposit it in their shells or skeletons. The part played by plants in
this same connection is shown by the way in which they eliminate carbon
dioxide from the air or from water, and concentrate the carbon in their
tissues. From the carbon accumulated in this manner, under certain
conditions, deposits of peat, lignite, coal, graphite, etc., have
resulted.
What may provisionally at least be termed molecular concentration occurs
when similar molecules are brought together largely by water and
crystallized to form mineral species. In order to simplify this brief
discussion as much as practicable, this phase of concentration will be
included under the chemical processes referred to above.
The three principal methods by which mineral substances are
concentrated, namely, the mechanical, chemical, and vital, have in the
main different fields of action. The mechanical and vital agencies
operate at the surface of the lithosphere, although organic products,
principally certain acids, descend into the earth in solution in water
and play an important part in deep-seated chemical changes, as in the
formation of mineral veins. The chemical agencies bring about the
concentration of mineral substances both at or near the surface and at a
depth.
The intensity with which the several agencies just referred to operate
varies according to conditions. The mechanical agencies, for example,
acting mainly through the aid of flowing water, are in general most
potent in humid regions and where the land is high above sea-level.
Vital agencies depend largely on climate and are most active in warm
humid regions. The chemical agencies are influenced largely by heat, the
presence of water, and by pressure.
It is interesting to note that a high degree of heat leads to the
dissipation and wide distribution of substances previously concentrated;
fusion, for example, permitting of the intimate mingling or
recombination of substances, previously segregated, although during the
dying stages of volcanic activity minerals like sulphur, cinnabar, etc.,
may be directly condensed and thus concentrated from a vaporous
condition.
During the formation of the three main classes of rocks composing the
earth's crust, the agencies leading to the concentration of various
substances now of economic importance have to a great extent been
different, and hence in a marked way the stones, ores, fuels, gems,
etc., to be expected in each of the three classes of rocks,
respectively, are distinct. Certain exceptions to this broad conclusion,
however, arise from the fact that rocks belonging to each of the classes
referred to may have been brought within the influence of the same or
similar concentrating agencies and like results produced in each class.
_Economic Importance of the Igneous Terranes._--The igneous rocks, as
previously noted, are such as have cooled from fusion. On the cooling of
magmas various minerals are formed, most commonly silicates, and except
in a minor way in connection with the weaker stages of volcanic activity
and the slow cooling of the rocks, there does not seem to be any marked
tendency towards the concentration or segregation of metallic minerals
or ores. Although igneous rocks do contain gold, silver, copper, etc.,
and a large variety of the rarer metals, they are widely disseminated.
As is well known, however, igneous rocks are in some instances of value
for the metallic mineral, gems, and ores associated with them, but in
the great majority of instances at least, and as a rule, these minerals
and ores are the result of subsequent changes and owe their origin
mainly to deposition from heated, percolating water. Rich ore bodies
frequently occur on the borders of igneous dikes, and in fissures and
cavities in igneous rocks, but the process by which they have been
formed is similar to that leading to the concentration of mineral matter
in metamorphic rocks, and will be referred to later.
The igneous rocks themselves furnish desirable building stones, such as
granite, diorite, porphyry, diabase, etc. With the exception of granite
and the nearly related diorite, these have not as yet been extensively
utilized in North America. Certain of the igneous rocks have been
altered to serpentine, which on account of its pleasing green colour and
the ease with which it can be cut and polished furnishes a stone
valuable for interior uses. It is also employed, usually with a rough
surface, in the construction of exterior walls of dwellings, gateways,
etc. Large bodies of serpentine occur at a number of localities in the
Atlantic mountains from Pennsylvania and Maryland northward, including
eastern Canada, and also over extensive areas in the Pacific mountains,
particularly in California, Washington, and Alaska.
The principal ores and minerals of commercial importance in the igneous
rocks are native copper, as in northern Michigan; copper pyrites, as at
Butte, Montana; gold, at many localities, including the Treadwell mine,
Alaska; opal, which is mined on a small scale in Idaho and Washington.
In practically all these instances, and numerous others that might be
enumerated, the substances referred to have been deposited from solution
in cavities in the rocks or have replaced other substances, and are due
to what is termed above chemical concentration.
_Economic Importance of the Sedimentary Terranes._--The sedimentary
rocks are composed principally of fragmental material derived from the
disintegration of older rocks transported and deposited mechanically,
and resulting in the formation of sandstone, shale, etc., and of
organically concentrated material, such as shells and corals, which form
limestones. The deposits originating in these ways furnish excellent
building stones, the principal classes being sandstones and limestones.
These occur widely throughout North America, and in formations of all
ages subsequent to the Archean. The sandstones were deposited near the
shores of the seas, or in lakes, and the limestones principally in
moderately deep oceans.
Sandstones occur largely in the Cambrian formation on the south shore of
Lake Superior and about the borders of the Adirondack hills of New York.
They are usually red or reddish-brown rocks, and their pleasing colours,
durability, even grain, and the readiness with which they may be broken
in any direction make them desirable building stones.
The Newark system, extending in detached areas from Nova Scotia
to South Carolina, contains immense quantities of brown and gray
sandstone, which have been extensively quarried, particularly in the
Connecticut Valley, New Jersey, Pennsylvania, and Maryland, and largely
used in Atlantic coast cities. The Carboniferous and Devonian
sandstones, usually of a gray colour, of Pennsylvania, Ohio, and
neighbouring States, are largely used in the cities of the interior
portions of the United States. Extensive deposits of Mesozoic and
Cenozoic sandstones occur throughout the Pacific mountains, and afford a
practically unlimited supply of good building material, which as yet has
been but little utilized. The colours of sandstones vary from bright red
through brown-yellow to gray, and in some cases are nearly white,
depending largely on the condition of the iron present. The red rocks
are dyed with ferric oxide; the brownstones contain iron, frequently in
the cementing material that unites the grains, in various stages of
oxidation and hydration; the gray stones may also contain iron, but if
present it is in union with organic matter, as the ferric carbonate, for
example. The Cambrian and Newark sandstones are prevailingly of some
shade of red, for the reason that not enough organic matter is present
to change the iron to a carbonate.
The sandstones when of an even fine grain and not too hard, are suitable
for sharpening tools, and large quantities of grindstones, whetstones,
etc., are made from them, as on the Lake Huron shore of Michigan, in
Ohio, etc. Other sandstones, practically free from iron, are used in the
manufacture of glass. The best example of "glass sand" is the Sylvania
sandstone of southeastern Michigan. Unconsolidated sand is largely used
in mixing mortars and cements, for smoothing stones used for
architectural and monumental purposes, as foundry sand in making moulds
for casting, and many other ways. Seaward from where sand is being
deposited we find in the present oceans that as a rule fine bluish or
greenish mud occurs, and still farther seaward, except where
coral-polyps thrive, usually at a distance of 100 miles or more from
land, the bottom is composed of calcareous mud or ooze. The sand
and mud are derived from the land, and if consolidated form sandstone
and shale. The calcareous ooze is derived from the life of the sea,
largely minute lime-secreting foraminifera, together with shells of
molluscs, and in the vicinity of coral islands or reefs the hard parts
of coral growth are added. That is, the calcareous oozes are formed by
the concentration of calcium carbonate through the vital action of
animals and to a less extent of plants. Such material, if consolidated,
would form ordinary limestone.
In North America there are terranes scores of hundreds of miles across
in various directions and hundreds and even thousands of feet thick that
have been formed in the manner just indicated. From this mode of origin
it may be truthfully inferred that limestone may have been formed during
any age since organisms having the power of secreting calcium carbonate
existed on the earth. The limestones of North America range in age from
the Algonkian period to the present time, and are still being formed in
the ocean and in a minor way in lakes.
Impure limestones, frequently coloured or clouded with red, due to
ferric oxide, are quarried on an extensive scale in eastern Tennessee,
and are used for decorative purposes. The Tennessee limestones referred
to are of Paleozoic age; in Florida porous rocks, known as coquina,
composed of imperfectly consolidated shells of living species of
molluscs, are used in the construction of buildings. Gray limestones
susceptible of a good polish occur in Ohio and neighbouring States and
are utilized to some extent for columns and interior finish of
buildings, but in the main the stones of this nature when employed for
architectural purposes are rough-faced. Vast amounts of limestone
suitable for masonry occur widely throughout the Mississippi Valley in
many of the ranges of the Pacific mountains, especially in the United
States and Mexico, and are also of immense thickness in the West Indies.
In many instances limestone has been metamorphosed, as will be described
below, and converted into crystalline marble. Commercially, however, all
limestone, whether crystalline or not, which is susceptible of a
polish, is termed marble.
Under certain conditions calcium carbonate is concentrated at or near
the earth's surface by chemical agencies, as about springs where
calcareous tufa, travertine, etc., are precipitated, and in caverns
where stalactites and stalagmites are formed. Stalagmite sheets are
sometimes composed of variegated, laminated layers, and when polished
produce a beautiful decorative stone which passes under the name of onyx
marble. Deposits of this character of commercial importance occur in
Arizona and Mexico.
Calcium carbonate concentrated in lakes through the combined action of
chemical and vital agencies produces the so-called marl, now extensively
utilized in the manufacture of Portland cement. In this mode of
accumulation the calcium carbonate is dissolved by percolating waters
from the rocks and soils and carried to lakes in solution; it is there
precipitated largely through the vital action of certain algæ and
deposited as a fine white ooze. Thousands of deposits of this nature,
varying in extent up to several hundred acres, and having a depth of
from a few feet to 40 and even 60 or more feet, occur in the portion of
the continent covered with glacial drift, and especially in the States
from New England to Minnesota. The reasons for the greater abundance of
marl in this region than elsewhere are that the glacial drift is there
highly calcareous, numerous lakes are present, and the climatic
conditions are such as to favour the growth of certain aquatic plants,
and especially the _Characeæ_ or stoneworts, which have the property of
eliminating calcium carbonate from ordinary lake waters.
The importance of the vital agencies in concentrating substances of
economic value is illustrated by the manner in which coal, petroleum,
and natural or rock-gas, etc., have been formed.
Land plants have the power, under the influence of light, of decomposing
the carbon dioxide (carbonic-acid gas) of the air and fixing the carbon
in their tissues, the oxygen being liberated and rendered
available for animal respiration. Carbon is thus concentrated, and when
plant remains accumulate and are preserved beneath water in swamps, a
slow change takes place and peat is formed. The essential conditions for
the accumulation of vegetable matter have been present on the earth ever
since a land flora existed, and coal-beds occur at many different
horizons. The earliest date at which land plants seem to have been
sufficiently abundant to furnish material for coal-beds was the
Carboniferous period. Although a similar flora existed during the
preceding period, the Devonian, no coal-beds of workable thickness are
known in the rocks of that age. Since the Carboniferous period coal has
been found at many horizons in the sedimentary rocks, and peat is being
accumulated at the present day.
[Illustration: FIG. 34.--Map showing the distribution of coal in North
America.]
The coal-fields of North America are more extensive than those of any
other continent, excepting, perhaps, the at present but little known
coal-bearing formations of Asia, and are distributed in temperate
latitudes, from tide-water on the Atlantic to tide-water on the Pacific
coasts, where the greatest commercial and intellectual development has
been reached.
Coal of Carboniferous age occurs in large and valuable deposits in Nova
Scotia and New Brunswick; there is a small area of graphitic anthracite,
not now utilized, in Rhode Island; but the great fields are in
Pennsylvania and the States southward to central Alabama, and westward
to beyond the Mississippi. A detached coal-basin containing some 6,700
square miles, but a small part of which is productive, however, occurs
in the central part of southern Michigan. Small coal-fields in Virginia
and North Carolina, the first to be worked in America, are of Jura-Trias
age and form part of the Newark system. Extensive fields of valuable
coal of Mesozoic age, principally in the Laramie system, occur in New
Mexico, Colorado, Wyoming, Montana, and still farther north along the
same great belt in Canada.
Another highly valuable field of Mesozoic coal is now being extensively
worked on Vancouver Island. The coals of the west side of the
Pacific mountains, largely lignites, but in many instances of high grade
and serviceable for steam coal, are mostly of Cenozoic age (Tertiary)
and occur in California, Oregon, Washington, and Alaska. The
distribution of the various coal-fields is indicated on the above map,
and space will not be taken in describing their geographical relations.
Peat is present in innumerable swamps throughout the humid, temperate
portion of the continent, especially from Louisiana and Florida
northward, to the region about the Great Lakes and widely throughout
Canada, but is at present of small commercial importance, although steps
are being taken for its extensive utilization.
The most valuable of the coal deposits are of Carboniferous age, and lie
to the east of the Rocky Mountains. The most of the coal is bituminous,
or soft coal, used principally in generating steam and for manufacturing
gas and coke. The exceptions occur in eastern Pennsylvania and in Rhode
Island. These are considered as metamorphosed coals, although in the
Pennsylvania region there is no evidence of the action of a high degree
of heat. In the Rhode Island field the rocks associated with the coal
are plainly metamorphic in character, and the coal has, in large part,
been changed to graphitic anthracite.
That anthracite may be of any age, however, is indicated by the local
changes that have occurred in Mesozoic and Cenozoic coals, where they
have been penetrated by dikes and other varieties of intrusions, or have
been altered by surface lava-flows. In such situations the coal has lost
nearly all its volatile matter, and in composition and in certain
instances, as in western Colorado, in physical character as well, is
essentially an anthracite.
In addition to the various coal deposits referred to above there is a
second series of organic compounds found stored in sedimentary rocks
which consists of hydrocarbon. This series of substances includes
natural or rock-gas, petroleum, maltha or semifluid hydrocarbon, and
solid hydrocarbons, such as asphaltum, albertite, grahamite,
ozokerite, etc. These substances are usually considered as being of
organic origin and to have resulted from changes which take place in
vegetable and animal tissues when buried and in most cases subjected to
heavy pressure. A large part of the hydrocarbons referred to is thought
to have been derived from animal organisms, an opinion which is
sustained in an important manner by the fact that large stores of both
petroleum and rock-gas have been discovered in rocks which were laid
down before land vegetation is known to have existed. Marine algæ were
present, however, so that it cannot be affirmed that the hydrocarbon of
the earlier Paleozoic rocks came entirely from animal organisms. It is
highly probable, however, that a large portion of the hydrocarbons
stored in Paleozoic and later strata was derived from the animals whose
hard parts occur so abundantly as fossils in the same or adjacent beds.
[Illustration: FIG. 35.--Ideal section showing favourable conditions for
the storage of petroleum and gas.]
Besides the concentration of carbon in plant and animal tissues and its
change to hydrocarbons, there is a still further concentration necessary
in order that stores of petroleum, gas, etc., shall be accumulated so as
to be of economic value. This accumulation is dependent largely on
physical conditions. The production of hydrocarbons from organic matter
contained in sedimentary rocks, and particularly in shale, is going on
in many regions, and probably nearly everywhere, especially when the
soft parts of animals are buried in the rocks, but the petroleum, gas,
etc., generated escape at the surface and pass into the air and are
again widely disseminated, unless conditions are present which lead to
their accumulation. The conditions favouring the natural storage of the
substances referred to are cavities, or more usually porous beds, such
as sandstone, beneath impervious beds, such as clay or shale. The
conditions are still more favourable when lateral as well as vertical
escape is cut off, as, for example, when arches or domes occur. The most
favourable conditions result when a bed of shale or other rock, as _a_,
Fig. 35, from which hydrocarbons are being evolved occur beneath a sheet
of porous sandstone or fissured rock of any kind, _b_, above which there
is a close-textured, unfractured stratum, such as shale, _c_, and the
series is bent along certain axes into upward folds or anticlinals.
Under these conditions, as extended experience has shown, a well drilled
at _d_ should yield in succession gas, petroleum, and water.
The conditions for the production of petroleum, gas, etc., have been
present on the earth since the first appearance of life, and reservoirs
may have originated at any subsequent time. The oldest known reservoirs
still charged with these substances that have been discovered occur in
the earlier Paleozoic rocks, just above the formations containing the
oldest known fauna. Important petroleum and gas fields in rocks of the
Trenton period occur in New York, Ontario, Ohio, and Indiana. The
Devonian rocks of Pennsylvania, New York, Ontario, etc., also yield
large supplies of both oil and gas. Mesozoic rocks of Colorado, Wyoming,
etc., are also rich in the concentrated hydrocarbon referred to, and on
the Pacific coast, particularly in California, rocks of Cenozoic age are
highly productive. Petroleum and gas may occur also in rocks more recent
than the Cenozoic, but owing to the absence of reservoirs, and possibly
the lack of sufficient time, no important accumulations are known in
beds more recent than the Tertiary, unless they come from a deeper
source in older rocks. The vast quantity of petroleum stored in the
rocks of various ages in North America is indicated by the fact that in
1900 the yield from the wells of the United States was 63,362,704
barrels, and from Canadian wells about 280,000 barrels, making a total
of nearly 64,000,000 barrels.
The stores of rock-gas are also enormous, as is indicated by the fact
that a single well at Bairdstown, Ohio, yielded over 17,000,000
cubic feet per day. In 1890 the average daily flow of the Indiana
gas-wells was 779,525,000 cubic feet. The value of the natural gas
consumed in the United States in 1900 was $23,606,463.
In the sedimentary rocks of North America there occur also extensive and
valuable deposits of semifluid and solid hydrocarbons, such as maltha,
asphaltum, albertite, grahamite, uintahite, etc., which have arisen,
under the most plausible explanation thus far offered, from the
concentration by evaporation of fluid hydrocarbons such as petroleum.
The evaporation, particularly of heavy petroleum, leads to the formation
of a solid residue, similar to asphaltum. In fact, there is no definite
boundary between the lightest naphtha and the most coal-like asphaltum.
They form a connected hydrocarbon series, analogous to the coal series.
Albertite, a bright, coal-like substance, exceedingly rich in volatile
hydrocarbon, occupies fissures in Carboniferous rocks in Nova Scotia,
and a similar but less lustrous mineral, termed grahamite, occurs in
fissures in rock of the same age, near a rich oil-pool in West Virginia.
Other similar deposits, but usually wax-like and dull, are found in Utah
and neighbouring States. Asphaltum occurs in vast quantities in southern
California, and also in Cuba; these deposits resemble the celebrated
asphaltum of Trinidad and give promise of being fully as extensive and
valuable.
In brief, gaseous, fluid, semifluid, and solid hydrocarbons in great
variety are widely distributed throughout the portions of North America
where the surface is composed of sedimentary beds, and in a few
instances occur in cavities in igneous rocks as well.
The influence of life in leading to the concentration of substances of
commercial value is still further illustrated by the beds of
diatomaceous earth which are found in various portions of North America
and elsewhere, particularly in Cenozoic and more recent terranes. Beds
of diatomaceous earth reported to be 40 feet thick and of wide extent
have been found near Richmond, Virginia, and similar deposits occur at
several localities in Oregon, California, etc. The uses of this fine,
white, flour-like powder, each minute grain of which is a
beautiful siliceous organism, are for polishing powder, as an ingredient
in friction soap, as an absorbent for nitroglycerine in the manufacture
of high explosives, etc.
A class of substances of economic importance which owe their
accumulation to chemical agencies acting at the surface of the earth is
well illustrated by deposits of rock salt and gypsum.
In the Silurian system in New York, Ontario, Michigan, etc., several
beds of rock salt and gypsum occur, indicating that there were formerly
a number of separate evaporating basins in that region. The beds of salt
vary in thickness from a few inches to over 300 feet, as at Tulley, New
York. At Goodrich, Ontario, 6 beds of salt from 6 to 35 feet thick have
been penetrated in a single well. With the salt in this the Salina
formation there are many beds of gypsum. In rocks of Carboniferous age
in Michigan, other extensive beds of salt and gypsum have been
discovered. In Louisiana, Texas, Utah, and other States, salt and gypsum
occur in Mesozoic and Cenozoic rocks. One of the most remarkable of
these deposits is beneath small islands in the Gulf of Mexico off the
Louisiana coast. On Jefferson Island, for example, rock salt was reached
recently at a depth of 260 feet beneath Cenozoic rock, and was
penetrated for over 1,800 feet without reaching the base of the deposit.
The supply of salt stored in the rocks, and the natural brines of the
arid region, such as the waters of Great Salt Lake, afford an
inexhaustible supply upon which comparatively small demands have thus
far been made.
In addition to salt and gypsum there are other substances that have been
accumulated in a similar manner, such, for example, as sodium sulphate,
of which large beds occur in the desiccated lake basins of the arid
region, sodium bromide, which is obtained from some of the ancient
brines pumped from deep wells in Michigan.
Next to the fossil fuels, the most important products of the rocks in
North America are the iron ores. Although certain igneous rocks are rich
in iron, and in some instances contain it even in a pure or
metallic state, none of the rocks that have cooled from fusion carry
iron in any form in sufficient quantities to be of commercial
importance. Most of the iron in igneous rocks is contained in mineral,
usually silicates, and would be difficult to separate. When exposed to
the air and to percolating water, the iron-bearing minerals of the
igneous or other rocks decay and the iron enters into various new
combinations. When organic acids are present, and especially carbon
dioxide, ferrous carbonate is formed, which is quite soluble, and is
taken into solution by percolating water, some of which emerges as
springs, and joins the surface run-off, which may also take up ferrous
carbonate in solution. One of the most common methods by which iron ore
is accumulated is when water carrying ferrous carbonate in solution
forms swamps and lakes, and in many instances as the water is exposed to
the air and aided by evaporation it parts with a portion of its carbon
dioxide, and the hydrated sesquioxide of iron or limonite results. When,
under similar conditions, an excess of organic matter is present, beds
of ferrous carbonate are formed. In other instances iron oxide is
precipitated in swamps and lakes through the action of low forms of
plant life. The ores of iron concentrated in these ways are in many
instances in well-defined layers, or lenticular bodies, which are
thickest in the central portion and thin out in all directions. Their
forms are determined mainly by the shapes of the depressions they
occupy. Both ferrous carbonate and limonite, however, occur in irregular
surface deposits.
In North America, bog-iron ores occur at the surface in many regions, in
existing swamps and about springs, but are seldom of economic
importance, owing in part to the great abundance of better ores.
Limonite occurs at the surface also, having been deposited in cavities
and as a cement for loose fragments, particularly on the weathered
outcrops of formations rich in iron. When rocks contain but a fraction
of 1 per cent of iron, the soil on their weathered outcrops, owing to
the removal of the more soluble ingredients and the leaving of the less
soluble oxidized iron, have a yellow, brown, or red colour, and
in some instances this process of concentration has produced workable
iron ore. Limonite and earthy hematites occur widely throughout the
Appalachian region, in central New York, and westward to the Mississippi
Valley. One of the most productive formations is the Clinton, a division
of the Silurian, the outcrop of which extends in a nearly continuous
band from Alabama, where at Birmingham, etc., it is extensively worked,
northward along the west side of the Appalachians to central New York,
and thence westward to Ohio, and appears again in Wisconsin. At many
localities throughout this belt, some 1,300 miles in length, iron
furnaces have been built, although now mostly abandoned, the ore supply
being the weathered outcrop of the Clinton limestone.
In the Carboniferous rocks of Pennsylvania and neighbouring States to
the south and west, layers of ferrous carbonate, formed when there was
an excess of organic matter present, termed black-band ore and kidney
ore, occur. The former is present as regular strata and the latter in
oval concretionary masses. These ores, although not as rich in iron and
less pure than certain other and more abundant and more accessible
deposits, have been extensively utilized, largely for the reason that
they occur in the same formation which furnishes coal available for
their reduction.
Deposits of iron ore accumulated in the several ways referred to above
may be metamorphosed and changed to hematite and magnetite. The richest
iron ores of North America are of this nature, and will be referred to
below in connection with other substances of economic importance
contained in the metamorphic rocks.
There are various other substances in the stratified rocks of North
America of economic importance which owe their value to some process of
concentration. Certain rocks, as the so-called greensands or marls of
eastern New Jersey, contain from 3 to 10 per cent of potash, which makes
them valuable fertilizers. In this instance the concentration took place
on the floor of the sea, through the action of decomposing
organic matter, and the potash-bearing mineral of the greensand, namely,
glauconite, was deposited in the interiors of the minute tests of
foraminifera. The importance of this material is indicated by the fact
that the greensands of New Jersey have been actively worked for more
than half a century, the annual products during many years being upward
of 100,000 tons.
Extensive areas in the Carolinas, Florida, etc., underlaid by rocks of
Cenozoic age, are rich in phosphatic nodules, which have been derived
from organic matter. The guano deposits of the low arid islands in the
West Indies illustrate another mode of accumulation of organic material
useful as a fertilizer.
The assorting of surface _débris_ by streams and currents has led to the
formation of extensive deposits of clay which occur widely throughout
the portions of North America where the surface is composed of
stratified rock, which is extensively used in the manufacture of
earthenware, bricks, tiles, terra-cotta, Portland cement, etc.
When rocks containing gold in nuggets, grains, scales, etc., are
disintegrated, and the resulting _débris_ removed by streams, mechanical
separation of the heavier from the lighter material takes place and all
but the very finest of the gold is concentrated on the stream beds. In
this manner the rich placers of the Pacific mountain region from
California to Alaska have originated.
The general nature of the ore bodies formed through the action of
chemical agencies in sedimentary rocks, by solution and redeposition, is
illustrated by the lead and zinc ores of Wisconsin, Missouri, the
silver-bearing lodes of the Pacific mountains, etc. In the case of the
lead and zinc deposits the ores occupy the interspaces between broken
sedimentary beds or line caverns. Under the best explanation of the
origin of these deposits that has been offered, although certain
modifications of the general hypothesis have been suggested which it is
not necessary to consider at length at this time, the lead and zinc are
considered to have been at one time widely distributed in the adjacent
sedimentary rocks, mainly limestone, and to have been taken in
solution by percolating waters and carried to cavities where they were
precipitated, together with various other mineral substances, such as
calcium carbonate or calcite, barium sulphate or barite, carbonate of
calcium and magnesium or dolomite, etc. The minerals containing lead are
principally galenite or lead sulphate, cerussite or lead carbonate;
while the zinc is contained in the minerals, sphalerite or zinc
sulphide, calamine or zinc silicate, smithsonite or zinc carbonate, etc.
These minerals, including both those containing lead and zinc, and those
intimately associated with them which are at present of no commercial
value, are such as are known to crystallize from solution without the
aid of high temperatures. In the Missouri lead and zinc districts the
ore deposits occur near the surface, the depth of the present working
seldom exceeding 150 or 200 feet, and, as nearly as can be judged, have
been formed by the downward transfer of mineral matter through the
process of solution and recrystallization, as the surface of the land
has been lowered by chemical and mechanical denudation.
Many of the rich silver-mines of the Pacific mountains occur in fissures
and cavities in sedimentary rocks, mainly limestone. Instances of this
nature are furnished by certain mines in northeastern Mexico, where the
ore is found in cavities in Cretaceous limestone; at Leadville and
Aspen, Colorado; Big and Little Cottonwood cañons, and the Horn
silver-mine, Utah, where the principal country rock is Carboniferous
limestone; the Eureka district, Nevada, where the ore occurs in cavities
in Cambrian limestone. In the case of several of these mines, igneous
rock is near at hand, and the ores are believed to owe their
concentration largely to the action of heated waters.
In other regions deep fissures, occupied in part by dikes of igneous
rock, have permitted of the ascent of water charged with mineral matter
from far below the surface; such waters are heated, in part by the
general heat of the earth's interior, or, if in association with dikes,
by the heat of the once molten intruded rock. The ascending hot water is
an active solvent, and as it rises becomes cooled, and for this
and other reasons precipitates many mineral substances. Veins are thus
formed, which are many times banded--that is, result from the filling of
fissures by the successive deposition of minerals of various kinds on
their walls, each different layer of minerals indicating a change in
conditions. Fissures filled in this manner from below, as denudation
progresses, become exposed at the surface and reconcentration through
the influence of disintegration and decay, and of solution and
redeposition by descending water takes place. Ore bodies of this
character carrying gold, silver, mercury, etc., are of wide occurrence,
especially in the Pacific mountains, but the process of concentration is
independent of the nature of the country rock. Segregated and fissure
veins occur in either igneous, sedimentary, or metamorphic terranes, but
are more commonly of economic importance in the metamorphic rocks than
elsewhere, and will be referred to again in that connection.
_Economic Importance of the Metamorphic Terranes._--The great laboratory
in which rocks undergo important changes in their physical condition and
in mineralogical and chemical composition, is what has been termed on a
previous page the zone of metamorphism. The depth of the upper limit of
this zone is variable, dependent in part on the nature of the rocks and
on movements within them, as is the case of mountain building. In fact,
there is probably no well-defined limit to the zone either above or
below, as in the former direction metamorphism merges by gradations into
alteration produced by the descent of surface water, and in the latter
direction as heat increases passes again, as we imagine, by insensible
and irregular gradations into a region where the rocks are so highly
heated that diffusion rather than concentration results. Whether the
rocks below the zone of metamorphism are fused or not depends on
pressure. They are probably solid, but in a potentially plastic
condition, and become fused and may be forced upward through fissures in
the condition of igneous magmas when pressure is relieved. The zone of
metamorphism lies between a superior zone where alteration by
descending water is dominant, and a lower region where alteration due
mainly to heat is in control. In the zone of metamorphism the influence
of heated percolating waters, combined with movements in the rocks, are
the principal factors which lead to the concentration of mineral
substances.
Under the influence of percolating, heated waters, new minerals are
formed in sedimentary or igneous rocks, and rocks once metamorphosed may
undergo additional changes. Mineral matter previously widely
disseminated through rocks is, under the action of percolating, heated
water, brought together and the regeneration and crystallization of a
large variety of ores and minerals result. The birthplace of a large
variety of ores and minerals is in the zone of metamorphism. It is in
metamorphic rocks that the geologist looks for gems, the precious
metals, crystalline marble, magnetic iron, etc.
For the most part, however, the native metals and ores of the precious
and many of the common metals are too widely disseminated in the
metamorphic rocks to be of commercial importance, and a still further
concentration, principally in fissures and other cavities, is necessary
before they can be of value to man. This secondary concentration is much
the same as in the case of the deposition of lead and zinc ores in
cavities in sedimentary rocks, and results largely from the solution and
redeposition, sometimes by replacement, of mineral matter by heated
waters.
Certain ores and rocks contained in metamorphic terranes owe their
concentration to previously acting processes of concentration, but have
undergone chemical changes in place. Illustrations of this class of
ores, etc., are furnished by the magnetite and hematite contained in the
metamorphic rocks on the eastern border of the Appalachians, in New
England, eastern Canada, and the Lake Superior region. These ore bodies,
frequently of great size, in some instances furnish evidence of having
been originally lenticular masses of bog-iron ore, or ferric carbonate,
associated with sedimentary beds, and originally concentrated, as
already mentioned, at the surface through the action of water charged
with carbon dioxide, but principally on account of the influence of heat
have been changed to a higher degree of oxidation and now appear as
hematite, as, for example, in the iron districts of the northern
portions of Michigan, Minnesota, Wisconsin, and the Ozark Hills, or
still further altered as in the richest of all iron ores, magnetite, so
abundant in the metamorphic rocks of the Appalachian region, about the
Adirondack hills, widely and in extensive bodies in eastern Canada,
about the south shore of Lake Superior, in Texas, etc.
In certain instances, as has been shown by C. R. Van Hise and others,
hematite ore, like that of the Lake Superior region, has resulted from
the alteration of ferrous carbonate which had replaced limestone by a
chemical process of solution and double decomposition.
As bodies of iron ore in the form of the carbonate, or limonite, may
occur in rocks of any age, and as rocks of any age may be metamorphosed,
it follows that hematite and magnetite may be present in any formation
which has been subjected to metamorphosing conditions.
Limestone when metamorphosed is changed to a crystalline marble,
frequently white in colour owing to the dissipation of its previously
contained organic matter. The white marbles so extensively utilized in
Georgia, Vermont, etc., are of this nature. Other similar metamorphosed
layers occur in several of the ranges of the Pacific mountains from
Mexico to Alaska.
The influence of metamorphism on deposits of coal when the heat has been
of moderate intensity serves to drive off a large part of the volatile
matter present and converts the coal into a substance resembling coke,
as has happened adjacent to dikes or intruded sheets of igneous rock in
the Richmond coal-field, Virginia, in New Mexico, Washington, etc. When
the heat is somewhat more intense, the coal is changed to what is termed
graphitic anthracite, as in the Rhode Island coal-fields, and when still
greater or long-continued, results in the production of graphite,
as in the Algonkian rocks about the Adirondack hills and over a wide
region in eastern Canada.
An important result of metamorphism is the production of new minerals in
the rocks acted on. Many of the metamorphic terranes consist essentially
of quartz, feldspar, and mica, which have been formed by the
rearrangement of the mineral matter contained in the rocks during their
previous state. Besides these constituent minerals there are frequently
others present, such as the garnets, tourmaline, emerald, sapphire,
corundum, etc., which are of economic importance. In a large number of
instances the minerals of metamorphic rocks are contained in veins of
one class or another, in part resulting from segregation in the rocks
themselves while yet in a heated condition, and in part deposited in
fissures or other openings as a result of secondary concentration
through the action of heated waters. The principal difference between
the minerals concentrated in the metamorphic rocks and those deposited
in cavities in unaltered sedimentary beds seems to be that in the former
instance the percolating water which carried the material in solution
had a higher temperature than in the latter case.
Among the numerous mineral substances of value in the arts, occurring in
the metamorphic terranes of North America, other than building stones
and the previously concentrated deposits, such as iron ore, graphite,
etc., mention can only be made at present of the following:
Mica, which is used in thin sheets for the windows of stoves and
furnaces, and when ground and mingled with other substances furnishes a
good insulating material for electric wires, fireproofing, and also used
as a lubricant, etc., occurs in large quantities in the metamorphic
rocks of New Hampshire and Ottawa, and less abundantly in North
Carolina, South Dakota, Wyoming, Idaho, etc. It is widely distributed,
but to find transparent colourless sheets of large size is difficult.
Talc and soapstone, consisting of the hydrated silicate of magnesia, and
useful for hearths, mantels, fire-brick, linings for stoves, laundry-,
bath-, and acid-tubs, etc., and when ground, employed as an
adulterant of soap, paper, rubber, and as a lubricant, etc., occurs
widely in the metamorphic terranes on the eastern side of the
Appalachians, in Canada, and at numerous localities in the Pacific
mountains. The chief centres of production at present are in
Pennsylvania, New Jersey, New Hampshire, and Vermont.
Asbestos, valuable on account of its fibrous structure and
non-conductivity of heat, which make it an excellent insulator, and
largely used in the manufacture of fireproof paper, cloth, etc., occurs
in connection with serpentine, in metamorphic terranes, and is
extensively mined in the Thetford district, Quebec.
Corundum, consisting of aluminum oxide, and having essentially the same
composition as the sapphire and ruby, and a less pure variety of similar
composition termed emery, is largely used as an abrasive in polishing
metal, sharpening tools, etc., and also as "sand-paper" in working wood,
occurs in commercial quantities, largely in crystalline limestone, at
Chester, Mass., in Georgia, North Carolina, and several other
localities. Although corundum is next to the diamond in hardness, and
therefore highly favourable, when reduced to a powder, for polishing
various substances, the demand for it has in recent years been
diminished owing to the manufacture of an equally if not superior
material termed commercially _carborundum_.
Among the crystals used as gems, which occur in the metamorphic rocks of
North America but thus far in minor quantities, and as a rule of
inferior quality, may be enumerated sapphires, rubies, tourmalines,
garnets, quartz, etc.
Apatite, a mineral rich in phosphoric acid, and largely used in the
manufacture of fertilizers, occurs associated with limestone in the
metamorphic rocks of Quebec and Ontario in the form of veins, beds, and
irregular pockets, and a few years since was extensively mined, but now,
owing to foreign competition, is held in reserve.
By far the most valuable of the minerals and native metals that occur in
the metamorphosed terranes is gold. Although this metal has been found
in paying quantities in association with nearly every kind of
country rocks and in terranes of all ages, the place of its original
concentration from a previously widely disseminated condition is to a
great extent in the zone of metamorphism. It occurs principally as
native gold, although usually alloyed with silver, but is frequently
contained in iron pyrites. In the crystalline rocks, such as gneiss,
schist, slates, granite, etc., it occurs in flakes and grains, but so
far as its occurrence in commercial quantities is concerned its
deposition has for the most part been secondary, and the metal, usually
in association with quartz, is found in veins, lodes, contact deposits,
etc., and owes its concentration to chemical agencies not well
understood, acting in connection with percolating water. That this
general statement is correct is clearly shown by the fact that gold
occurs in crystals, flakes, grains, etc., most frequently in quartz and
iron pyrites, which, as can be shown in a number of ways, have
crystallized from solution. The gold and its commonly associated mineral
in countless instances occupy fissures and must have been carried to
such localities after the surrounding rock had been fractured. So
intimate is the association of gold with metamorphic rocks that this is
one of the main guides in searching for it, although, as already stated,
it is frequently present in other rocks as well. With the disintegration
of the metamorphic terranes the gold is set free, and may be still
further concentrated by streams so as to form the well-known placers.
A very large proportion of both the quartz and placer mining of North
America is in regions occupied by metamorphic rock. This is true of all
gold-mines, previously quite largely exploited, of the Atlantic mountain
region from Georgia to eastern Canada. The mines of California are also
largely in schistose rocks, as are also those to the northward,
throughout the Pacific mountains, to British Columbia and Alaska,
including the recently established mining district at Cape Nome.
With placer gold, and probably derived largely, if not entirely, from
metamorphic rocks, there are frequently found grains of platinum. The
annual production of this metal in the United States and Canada
has a value of about $5,000.
The study of the distribution of native metals and ores in the
metamorphic rocks of North America indicates that in general the older
rocks, as the Archean, for example, are less rich than the younger
terranes, such as the schist, etc., of the Sierra Nevada and Cascade
Mountains. This seems to indicate that the older rocks were once deeply
buried and their more soluble substances removed by ascending waters,
and in part redeposited in higher terranes. Erosion has since carried
off the rocks which were mineral-charged and laid bare the depleted
terranes beneath. This hypothetical explanation of the general poverty
of the Archean rocks is coupled with another consideration, namely, that
the younger metamorphic terranes, where they have been elevated, as in
the Pacific mountains, are more broken than the Archean rocks, and
afford more cavities in which minerals may be deposited. Whether this is
a complete explanation or not remains to be demonstrated, but
observation shows that the Archean terranes--all of which as yet
discovered are composed of either metamorphosed or igneous rocks--are,
in comparison with younger metamorphosed rocks, relatively poor in
minerals and ores of commercial importance.
Among the economic products of the rocks are included mineral waters.
The direct commercial value of such waters, not including their use for
baths, etc., in the United States, is about $7,000,000 annually. The
demand for these waters depends largely on the mineral substances they
hold in solution, and which in many instances is in process of
transference from one locality to another. Much might be written in this
connection in illustration of the fact that the processes by which
minerals, ores, etc., have been concentrated are still in progress.
LITERATURE
An extensive literature is available concerning the geology, minerals,
ores, etc., of North America, but only a few of the more important
publications can here be referred to. The numerous publications
of the United States Geological Survey, the Geological Survey of Canada,
and the Geological Survey of Mexico contain vast amounts of valuable
information. Several of the States of the United States have independent
surveys and have published numerous reports. Of journals containing
articles of American geology, the more important are: _The Journal of
Geology_, published at the University of Chicago; _The American
Geologist_, published at Minneapolis, Minn.; _The American Journal of
Science_, published at New Haven, Conn. The publications of a large
number of learned societies in Canada and the United States should also
be consulted.
The most useful bibliographies of North American geology are:
DARTON, N. H. _Catalogue and Index of Contributions to North
American Geology, 1732-1891._ Published as Bulletin No. 127 of
the United States Geological Survey, Washington, D. C., 1896.
DOWLING, D. B. _General Index to the Reports of Progress_ [of the
Geological Survey of Canada], _1863-1884_. Published by the
Canadian Geological Survey, Ottawa, Canada, 1900.
WARMAN, P. C. _Catalogue and Index of the Publications of the
United States Geological Survey, 1880 to 1901._ Published as
Bulletin No. 177 of the United States Geological Survey,
Washington, D. C., 1901.
WEEKS, F. B. _Bibliography of North American Geology,
Paleontology, Petrology, and Mineralogy for the Years 1892-1900,
Inclusive._ United States Geological Survey, Bulletins No. 188
and 189, Washington, D. C., 1902.
Of the numerous general treatises on the geology, the following will be
found especially helpful to the student:
DANA, J. D. _Manual of Geology._ Fourth edition. American Book
Company, New York, 1895.
KEMP, J. F. _The Ore Deposits of the United States and Canada._
Scientific Publishing Company, New York, 1900.
LE CONTE, J. _Elements of Geology._ Fifth edition, revised and
partly rewritten by Prof. H. L. Fairchild. D. Appleton and
Company, New York, 1903.
MERRILL, G. P. _A Treatise on Rocks, Rock-Weathering, and Soils._
The Macmillan Company, New York, 1897.
SHALER, N. S. _Outlines of the Earth's History._ D. Appleton and
Company, New York, 1898.
CHAPTER VII
THE ABORIGINES
At the time the Western Hemisphere became known to Europeans, as has
been shown by subsequent explorations, it was inhabited by native tribes
from the Atlantic to the Pacific and from the extreme north to
Patagonia. The aborigines were distributed principally along the coast,
about the borders of lakes, and on the margins of streams, but much of
the interior was also inhabited or roamed over by hunting and war
parties, or crossed by various tribes during their migrations. Large
areas, it is true, more especially among the rugged mountains, in the
great subarctic forest, and on the trackless tundras, had no permanent
residents, but in general terms the entire land was inhabited.
In spite of the reports as to the density of the aboriginal population
made by several early explorers, who for the most part followed the
waterways, visited the most thickly inhabited regions, and saw the
natives when brought together by motives of curiosity or defence, it is
now known that North America, considering its vast extent, was but
sparsely peopled. As to the number of the inhabitants, there is no even
approximately accurate knowledge. The greatest density of population, so
far as can be judged, was in the tropical region, and decreased
northward in a general way in conformity with change in latitude, but
varied also in a conspicuous manner in accord with local climatic and
topographic influences.
In the same manner as the exploration of the New World led to the
discovery of many species, genera, etc., of plants and animals, it also
added two types of man to those previously known to Europeans. The
propriety of separating the American aborigines into two groups of
tribes is based on the contrasts the members of these divisions
present not only in colour and other physiological characteristics, but
on well-marked differences in language, customs, arts, etc. On this
basis two varieties of the human species have been recognised, namely,
the Eskimo and the Indian.
The term Eskimo, formerly spelled Esquimau, is of obscure origin, but is
thought to have been adopted by Europeans from the Indians of Labrador,
who thus designated a northern people living on the coast, and is said
to mean "raw-flesh eaters." The word in use among the Eskimos to
designate themselves is _Innuit_, meaning people, or the people, in the
sense that in their own estimation they are of more importance than all
other peoples.
The term Indian, as is well known, arose from an error of the early
Spanish voyagers, who, on arriving in America, believed they had reached
India, and hence termed the natives of the new land Indians. This
mistake has led to many attempts to substitute some other word by which
to designate the people referred to, but thus far none of the terms
proposed has been generally accepted. In the present book the word
Indian is used to designate the aborigines of the New World, exclusive
of the Eskimos.
The geographical distribution of the Eskimos and Indians is sharply
defined even at the present day, and is indicated on the map forming
Plate VI.
_Origin of the Aborigines._--The generally accepted conclusion in
reference to the origin of the American aborigines seems to be that man
reached this continent while the peoples of the Old World were yet in a
primitive condition, and at a time when the highest stage of culture was
expressed by the knife and spear-point of chipped stone, and developed
independently in accord with the natural conditions with which he was
surrounded. More than this, once planted, the original stock received
but slight if any accessions by subsequent immigration. This last
statement is not in strict accord with the conclusions reached by
certain ethnologists, who claim that the use of masks, the art of
carving on wood, stone, ivory, etc., the practise of tattooing, the
preservation of human heads, and other customs practised by the Indians
of the Pacific coast of the two Americas--and in North America,
extending eastward along lines of easiest communication--suggest an
influence coming from Polynesia at a time when the peoples dwelling on
the west borders of the Pacific had made a well-marked advance in
culture. Some influences on the aborigines of America coming both from
Polynesia and eastern Asia must seemingly be admitted, the importations
having been by means of storm- and current-swept boats and junks, but
the evidence does not point to trade relations. The most that can be
claimed seems to be slight modifications of the arts and customs of the
American aborigines, but not enough to make what may be termed an
indelible impression upon them.
The low state of culture of the original stock from which the American
aborigines were derived, implied in their distinct subsequent
development in language, arts, etc., indicates that man appeared in
America previous to the invention of boats capable of crossing broad
oceans. The necessary inference from this--if the hypothesis of one
place of origin for the human race is accepted--is that migration to
America was by land, or at most across narrow straits. The geography of
the continents must have been markedly different from what it is at
present to admit of this, providing the proof that access was not gained
where Asia and America make a near approach to each other at Bering
Strait is conclusive, and at present that evidence seems unquestionable.
The present state of opinion in reference to the origin of the American
aborigines is thus expressed by one well qualified to speak with
authority. At the close of a review of several lines of evidence J. W.
Powell says:
"Thus we are forced to conclude that the occupancy of America by mankind
was anterior to the development of arts, industries, institutions,
languages, and opinions; that the primordial occupancy of the continent
antedates present geographical conditions, and points to a remote time
which can be discovered only on geological and biological
investigation."
_Antiquity of the Aborigines._--The conclusions to be drawn from the
studies of ethnologists in reference to the length of time man
has made his home in America are qualitative, not quantitative. The time
is certainly long, probably embracing tens of centuries; but how long no
one can state in years. This claim for a great although indefinite
antiquity is based on several lines of evidence, some few of which the
reader may find it profitable to briefly consider.
A comparison of physiological characteristics shows that the American
aborigines have well-marked differences from all other varieties of the
human race. This conclusion is not based on any one special feature,
although colour and character of the hair are the most conspicuous, but
on the resultant, so to speak, of many attributes. It is, in a measure,
a comparison of ideal type-examples of each variety. While each
characteristic that may be chosen has individual and tribal variations,
and but few of them are perhaps conspicuously different from those
pertaining to the peoples of the Old World, yet taken together they
clearly differentiate the American aborigines from all other varieties
of the human species.
Applying the same principles to man that are used in the study of the
geographical distribution of the lower animals, the only legitimate
conclusion the naturalist can deduce from the evidence just referred to
is that the branch of the human family indigenous to North America has
been isolated for a sufficient length of time to develop into a new
variety. The American aborigines are different from all other varieties
of the human species because each more or less isolated community or
group of communities the world over has varied in its own way in accord
with climatic and other conditions, and the connecting links have been
lost. The differences that have arisen in this manner are so great that
the nature of the parent stock is no longer determinable from its living
representatives. This process of development among the lower animals is
understood to involve a great length of time; and the inference is that
man's development is no exception to the rule.
The evidence favouring a great antiquity for the American aborigines is
strengthened by the fact that when first known to Europeans both North
and South America were inhabited by tribes having more or less
well-defined territorial limits. If this population spread from one or
even from several centres it is evident that a great length of time
would be required for it to reach all parts of the New World and to
become adjusted to a wide range in climatic and other conditions, as is
known to be the case.
Students of languages have shown that the most enduring characteristics
of man are to be found in his speech. The fundamental principles of a
language outlive not only political and social changes, but even
physiological distinctions, and are inherited from a primitive stock by
all its branches. We might reasonably expect, therefore, that a study of
the languages spoken in America in pre-Columbian days would be a sure
index as to the primitive stock from which the various tribes came, and
show to which of the many other branches of the linguistic tree they are
most closely related. Turning with this question to those who have made
a critical study of the languages of the American aborigines, and no one
is better qualified to bear testimony in this connection than J. W.
Powell, the honoured director of the American Bureau of Ethnology, we
find a definite answer. He says:
"The North American Indian tribes, instead of speaking related dialects,
originating in a single parent language, in reality speak many
languages, belonging to distinct families, which have no apparent unity
of origin."
To the north of Mexico (Plate VI) the aborigines are divided into 58
linguistic families. In a large portion of these languages there are
tribal dialects not understood by members of other tribes of the same
family. Thus the Algonquin linguistic family contains some 30 or 40
distinct languages. In the Athapascan the diversity is nearly as great.
The smaller families present similar conditions in proportionate degree,
although there are stocks which speak but one language. Four of the
linguistic families referred to extend into Mexico, but to the south of
the territory occupied by them other languages and dialects are spoken.
Ethnologists who have studied the tribes of Mexico report 19 linguistic
stocks, containing 108 distinct languages, among which there are upward
of 60 dialects. In Central America a similar diversity in the
native tongues exists. Reclus, in his great work The Earth and its
Inhabitants, states that in the New World 450 native languages are
spoken--a number greater than that of all the languages in use in the
rest of the earth. Not only are the American linguistic stocks different
from each other, and fail to furnish evidence of having been derived
from a single parent tongue, but, as philologists assure us, no one of
them is analogous to any language spoken in other lands.
As is well known, a language is not created _de novo_, but by a slow
process of development. Since the first acquirement of articulate speech
by man a succession of languages has appeared owing to the growth,
differentiation, etc., of pre-existing forms of speech. It is a
warrantable inference, therefore, that the marvellous diversity in
speech present in America could only have arisen by a process of
evolution involving a very long period of time.
As the American languages have no affinity with the Teutonic or Semitic
stocks, it is evident that the source or sources from which they came
far antedate the birth of the oldest people of which history takes
cognizance. Man must therefore have set foot on American soil before the
sprouting of the linguistic twig which, after millenniums, produced the
cuneiform inscriptions of ancient Persia and Assyria.
The diversity of arts, customs, myths, religions, etc., among the
American aborigines, and their difference in nearly all instances from
the analogous attributes of the peoples of other lands, also point to a
long period of isolated development in much the same manner as has been
referred to in the case of a comparative study of their languages. The
skin boats used by the Eskimos are widely different from the birch-bark
canoes of the Algonquins, and these again differ conspicuously from the
dug-out canoes of southeastern Alaska and British Columbia; still other
varieties of boats are peculiar to the more southern Indian tribes, and
all alike differ from the boats used in other lands. Like individuality
pertains also to the houses of the American aborigines, their clothing,
arms, utensils, basket-work, picture-writings, etc. One is forced to
recognise in each of these arts or industries not only development in
many diverging lines among the various tribes, but the birth of ideas
analogous to those which arose in other lands, and their independent
growth under special conditions. All of this, and much more in the same
general direction that might be discussed did space permit, points to a
great antiquity for the indigenous American peoples.
Among the nations of the Old World certain plants have been under
domestication for so long a time, and have varied so greatly, that the
wild species from which they came are no longer known. This is true of
nearly all our common fruits and vegetables and many of our flowers that
were derived from the Old World. At the time of the Spanish conquest the
aborigines of America were cultivating tobacco, potatoes, beans,
tomatoes, squashes, maize, cotton, etc., and in the case of most of
these plants the wild species from which they were derived has not been
ascertained. The argument that points to a great antiquity in the case
of wheat and the peach applies equally well to tobacco and maize, and
indicates that horticulture began in America in remote antiquity. At the
time of Columbus, the ox, sheep, goat, pigeons, fowls, cat, etc., long
domesticated in the Old, were absent in the New World, and the llama,
turkey, etc., indigenous in America, were unknown in Europe. These
striking differences, among which there is not even a single exception,
amount to positive evidence that contact between the peoples of the Old
and the New World did not occur after the inhabitants of the former
emerged from savagery, or, what is the same thing, never existed in the
sense that trade relations were entered into. This same line of argument
seemingly casts grave doubts on the deductions already referred to
concerning the importation into America from Polynesia of the practise
of tattooing, the wearing of masks, the use of labrets, etc.; and
indicates also that but slight changes were produced in the American
aborigines owing to the wrecking of Asiatic junks on the northwest
coast.
Another factor bearing on the antiquity of the indigenous Americans is
the stage of development reached in spite of their long and nearly
complete isolation. Stimuli from without, and particularly
contact with more advanced peoples, having been lacking or of small
importance, incentive to bodily and mental activity arose mainly from
the desire for food, clothing, and shelter, and from intertribal
rivalry, jealousy, and war. This process of indigenous development was
certainly slow. With man, as with the lower animals, the rate of advance
and of specialization increases as higher and higher grades of
development are reached. For the American aborigines to have attained
the higher stages of barbarism at the time of the arrival of civilized
Europeans, solely by self-growth and self-education, is perhaps even a
stronger argument for their antiquity than their differentiation in
culture, languages, etc.
These several lines of evidence point to the coming of man to America as
an event of the far distant past--a time so remote, in fact, that it
pertains to geology rather than to ethnology.
Turning to the geological records, we find no authentic and
well-attested evidence of the presence of man in America either previous
or during the Glacial period. From time to time so-called "finds" of
stone implements in gravel and other deposits more or less definitely
determined to be of Glacial age have been made, but in all of these
instances convincing proof as to the age of the deposits, or of the
relation of the implements in question, to them, has not been presented.
Certain discoveries of the bones of men and of articles of human
manufacture found in California have been claimed to be of Tertiary
age--that is, much older than the Glacial epoch--but more critical
studies, especially by W. H. Holmes, have shown that they are decidedly
modern and pertain to the Indians still living in the region where they
were found. In brief, all the geological evidence thus far gathered
bearing on the antiquity of man in America points to the conclusion that
he came after the Glacial epoch. Judgment in this respect, however,
should be held in abeyance, as the search for evidence is as yet
incomplete.
As the problem now stands, the origin of the American aborigines is not
only unknown, but no generally accepted or fairly promising
hypothesis as to the land from which they came, the route followed, or
the date of their arrival is to be found among the large number
suggested. A continuation of the critical, ethnological, and geological
studies now in progress, it is hoped, will do much to clear away this
mystery, but at present only small progress can be truthfully reported.
_Culture of the Aborigines._--In the classification of peoples in terms
of culture three main divisions are commonly recognised, namely,
_savagery_, _barbarism_, and _civilization_; but the boundaries between
these divisions are not sharply defined and a wide range of intermediate
gradations is easily discernible.
By savagery is understood the lowest grade of culture and of ethics, in
which social customs are lax or wanting and tribal organization not
attempted. In the condition of savagery people are without permanent
homes, do not attempt agriculture or even horticulture, have no
domesticated animals except perhaps the dog, and subsist on fish and
game, including molluscs, small mammals, and reptiles, and such seeds,
fruits, nuts, etc., as wild plants supply. The art of kindling fire is
probably known to all existing savages, but much of their food is eaten
uncooked.
In the state of barbarism tribal organization may exist; some form of
religion is usually recognised; definite marriage relations are entered
into, although polygamy is commonly practised; permanent houses, perhaps
for winter use only, are built; clothes are made from woven cloth as
well as from skins; the plaiting of baskets and the art of making coarse
pottery, frequently highly decorated, are understood; essentially all
utensils, arms, etc., are of stone, wood, bone, or ivory, the metals
other than those occurring in a native state being unknown; and writing
is unknown, although pictographs may be employed.
Civilization implies a well-marked development in ethics, laws, social
organization, institutions, arts, writing, etc.
Under this scheme of classification various divisions of the aborigines
of North America at the time of the coming of Columbus occupied each of
the planes of development designated; but those frequently classed as
civilized had not arrived at an advanced stage of culture, and
can perhaps with greater propriety be designated as semicivilized, or,
better still, be referred to the highest stage of barbarism.
Some of the native tribes, as those of southern California and certain
of the peoples of Mexico and Central America, were in a state of
savagery, and, in fact, have not advanced beyond that state at the
present day. A large majority of the aborigines, as, for example, the
Algonquins, Shoshoneans, etc., or, in general, all of the Indians to the
northward of Arizona and New Mexico, together with certain of the tribes
to the south of that boundary, had definite tribal organization,
permanent homes at least for winter use, in part practised horticulture,
and for these and other reasons are to be classed as in the barbarous
stage of development. The Aztecs, Mayas, etc., of Mexico and Central
America had well-established governments, built permanent and frequently
large and elaborately decorated houses, some of which were of hewn
stone, practised horticulture with the aid of irrigation, had developed
a system of picture-writing, and were skilled in working native metals.
These and other advances towards civilization were great and promising,
but the use of iron was unknown, and their practice of human sacrifice
and the absence of phonetic writing denies them a place among truly
civilized peoples.
Another scheme for the classification of peoples in terms of the highest
grade of implements used by them is current under which they are placed
in certain ages on the assumption that man in all regions has passed
through an orderly sequence in his development, and that the successive
changes are expressed by the nature of the material used in the
manufacture of implements. Under this plan of classification we have an
age of stone, an age of bronze, and an age of iron. The stone age is
commonly divided into two parts: an earlier or _paleolithic_, during
which the highest type of implement used is fashioned of stone by
chipping; and a later, or _neolithic_, when implements of stone are
shaped by grinding and polishing. Following the stone age came one of
bronze, when a mixture of copper and tin was used for implements; and
later the age of iron, beginning when the art of reducing metals
from their ores was discovered. In this scheme a copper age is sometimes
included, with doubtful propriety, however, if, as in America, the metal
referred to is obtained in its native condition.
Under the somewhat indefinite scheme of classification just referred to
the North American aborigines, inclusive of the Aztecs, etc., previous
to the coming of European civilization were in the stone age of
development, although bronze was in use among the Incas of Peru, and to
some extent had found its way northward as far as Mexico. Certain of the
tribes still used implements of chipped stone, but in the great majority
of instances implements of polished stone were the highest type known.
Native copper was widely used for axes, knives, ornaments, etc., but
iron, except such as occurs in meteors, was unknown.
The difficulty met with in selecting any one article or any one material
used by primitive peoples as a basis for their classification is
illustrated by the facts just cited, as it places the lowest savage of
America in the same group as the Aztec and the Maya. Obviously, in the
classification of peoples as with the lower animals all characteristics
should be included.
THE ESKIMOS
The extreme northern part of North America is included in the
circumpolar lands described in another volume of the series of which the
present book forms a part, and the Eskimos as a people will therefore
receive but passing attention at this time.
One of the most interesting facts to the geographer concerning the
Eskimos is their peculiar distribution. From choice or necessity they
make their homes on the bleak, inhospitable northern border of the
continent, and do not extend inland except where the coast is indented
or large rivers enter the sea. In all localities their dwellings are
near the water. They are the most northern people on the earth, and
their still greater northward extension is checked only by the absence
of land on which to build their winter homes. Their present inland limit
on the continent is no doubt determined in part by long-established
custom and by the distribution of the animals on which they have become
dependent for food, clothing, fuel, etc., but the chief control
formerly, no doubt, more potent than at present, is to be sought in the
aggressiveness of the Indians. In Greenland, the arctic archipelago, and
throughout the immense extent of coast-lands from Labrador to Alaska
they have been isolated and withdrawn from contact with other peoples
for a long period of time, and their slow development unmodified by
extraneous influences. In Newfoundland and Alaska, however, they have
been in contact with the Indians, trade relations established, and to a
limited extent an interchange of ideas as well as some intermarriage has
taken place.
Throughout the vast extent of arctic coast between Newfoundland and
Alaska, as well as in Greenland and on the islands of the arctic
archipelago, the Eskimo was the sole inhabitant before the coming of
Europeans, and one language current from the Atlantic to the Pacific. No
other primitive people has such an extent in longitude. The reason for
this peculiarity is that between the sea margin, where the Eskimo makes
his home, and the southern border of the subarctic forest and adjacent
prairies, where the Indians have their hunting-grounds, there intervenes
the tundra--a neutral ground attractive neither to the Eskimo nor the
Indian.
The one thing which more than all else has enabled the Eskimo to
maintain an existence and to thrive in the frozen north is his discovery
of a means of obtaining heat and light where wood is scarce--that is,
the invention of the lamp. This invention, as has been shown by Walter
Hugh and others, was favoured by the occurrence in the far north of
animals like the seal and walrus, which yield oil with a high
heat-giving property.
In Alaska the Eskimo stock is broken into several tribes speaking
diverse dialects. Of these, two main subgroups are distinguished,
namely, Innuits and Aleuts or Aleutians. The former includes several
tribes living on the margin of the mainland, from near Mount St. Elias
northward to the Arctic Ocean, and the latter consists of but two
tribes, now intermingled, which at the time of the discovery of
the Alaskan region by the Russians inhabited the western portion of the
Alaskan peninsula and the Aleutian Islands. A detailed account of these
peoples should have united with it a study of the so-called Tuski of
northeastern Siberia, who are of the same stock, and, as seems probable,
are the descendants of Eskimos who migrated from America to Asia.
_The Innuits._--This name, as is stated by W. H. Dall, is applied to
themselves by all the tribes of the Eskimo stock, except the Aleuts and
the eastern Siberian natives. It is in use at the present time from
Greenland to Bering Strait, and thence southward to the vicinity of
Mount St. Elias.
In Alaska the Innuits are divided into at least fourteen tribes,
speaking as many different dialects, and distinguished by such names as
Ugalakmuts, Kaniagmuts, etc. The termination _mut_, in a substantive
sense, means a village at the place or on the river to the name of which
it is added (Dall). In common with all other Eskimo tribes the Innuits
are a sturdy, well-built people, having lighter-coloured skins than the
Indians, and more nearly approaching the yellow of the Asiatics, but
distinct from it, and in many instances having a decided reddish tinge
to the cheeks. The prevalent idea that the Eskimo is of decidedly short
stature is not borne out by the various tribes in Alaska, who are not
much, if any, below the average height of Europeans. Their rotund bodies
and full, round faces, in which the organ answering to a nose is
depressed until between the eyes it is scarcely distinguishable, suggest
that the severity of the climate has led to a development of fat for
protection against cold in the same manner as among the seals and
walruses. Such a generalization is perhaps misleading, as great
individual variations occur as among all peoples, but the typical Innuit
whose figure remains in one's memory when the bony hags, the cadaverous
individuals, and the aged are forgotten or but dimly recalled, favours
the conventional pictures of Santa Claus, with a face resembling the
full moon, small black eyes with a suggestion of obliquity in their
alignment, and nearly complete absence of a beard on the ruddy cheeks.
The food of the Eskimos of Alaska, as is the case with all other
divisions of that people, is derived mainly from the sea. Their diet is
almost exclusively fish, the blubber and flesh of the seal, walrus, and
whales, especially the white whale or beluga, which ascends the larger
streams. To these sources of supply are added the arctic hare, caribou
(reindeer), and in fact any flesh that can be obtained. Vegetable diet
is almost unknown, except so far as it is supplied by the berries that
grow in profusion on the tundras. The necessity for salt, so marked in
the case of most peoples, is absent in the far north.
The coast of Alaska, where dwells the Innuit, is treeless. Inland from
the margin of the sea extends the permanently frozen tundra. Wood for
fires, sleds, frames for skin boats, spears, bows, arrows, etc., and in
prehistoric time for producing fire by friction, is derived entirely
from driftwood cast on the beach by the waves. This wood, consisting in
many instances of great tree trunks from which planks two or more feet
wide can be hewn, is brought to the sea by rivers heading far inland,
as, for example, the Yukon and the Kuskokwim, and distributed by the
wind and currents all about the coast and islands of Bering Sea.
Driftwood is also carried to the Arctic Ocean by the Mackenzie, but in
general is not plentiful on the borders of the ice-bound northern ocean.
The houses of the Alaskan Innuit previous to the coming of the Russians,
and still to a great extent, consist of a single room, usually measuring
about 10 by 14 feet, situated in part below the surface of the ground
and entered by means of a tunnel-like passageway. They are made of
driftwood, and floored, lined, and roofed with planks hewn from the same
material. On a roof of poles sods and earth are placed and rendered
compact by stamping, thus forming a cover which serves to exclude water
produced by the melting of the naturally added layer of snow. When
spring-time approaches these partially subterranean winter dwellings are
liable to be inundated, and are abandoned and tents used during summer
seasons. Formerly these tents were made of skins of caribou or seal, but
in these degenerate days cotton drilling bought of white traders
has been substituted. During winter journeys temporary snow huts are
built, of the oval, bake-oven shape, well known to most Europeans from
the many pictures that have been published of similar structures made by
the more northern Eskimos. On the coast of Alaska, however, when
driftwood is available, the roofs of the snow houses are frequently made
of poles on which snow is piled.
In addition to the ordinary winter dwellings, which are usually occupied
by two or more families, each village is commonly supplied with an
assembly house or _casine_ (a word of Russian origin), which serves also
as a bath-house, and in them winter dances, the chief amusement of the
people, are held. The casine, built by the united efforts of the various
members of a community, consist of a single room, in part underground
and entered by a tunnel, which frequently measures some 25 by 30 feet on
the sides, and is approximately 15 feet high. They are substantially
made of logs or of thick planks hewn with much labour from stranded tree
trunks. The roof is of logs covered with moss and earth, and has an
opening in the centre for the escape of smoke from the fire kindled on a
hearth in the centre of the floor. When the fire is not burning, the
opening in the roof is closed with a membrane obtained from the
intestines of the seal. About the sides of the room there is a raised
platform for spectators during dances and for the use of bathers when
the customary steam-baths are indulged in. An interesting fact in
connection with both the ordinary winter homes and the casines, which
indicates their American origin, is that they are communal. A tenement
used by several families in common is characteristic of the American
aborigines from the arctic to Panama.
The architecture of the Innuits has been modified but little during
recent years, except that in localities most visited by white men and
where trading stations have been established, as at St. Michael,
log-houses built after the manner of those used by the Russian residents
have to a considerable extent replaced the native huts, with favourable
results so far as sanitary conditions are concerned. The Russian
log-house is not unlike the many similar structures still to be
seen in portions of Canada and the United States, except that the upper
side of each log is hewn so as to have a sharp edge, which fits into a
deep groove, cut in the log which rests on it. Moss is placed between
the logs, and is also used to fill all holes and crevices. Air is
usually admitted through a pipe situated beneath the floor and opening
in front of the stove, if one is used, and a small pipe for ventilation
passes out through the roof. In the Russian houses the stove is usually
a huge affair, made of large flat stones, which retain heat for a long
time.
[Illustration: PLATE VI.--Linguistic stocks of indians north of Mexico.]
The dress of the Innuits in former days, in common with all the Eskimo
tribes, consisted of skins, and in special cases of the intestines of
seals. The characteristic garment is the parkie or overshirt, not open
in front, however, provided with a hood and made of caribou skin tanned
with the hair on. Those worn by men have a different cut than those
intended for women. In recent years, and perhaps before the coming of
white men, the skins for the manufacture of parkies were derived largely
by trade from the people owning domesticated reindeer in Asia. The
margin of the hood is commonly made of wolf skins, the long hair of
which, blowing across the face, affords much protection. Trousers and
boots made of the skin of the hair-seal or moccasins shaped from the
skin of the leg of a caribou completed the dress. Mats of grass are worn
in the boots or moccasins during cold weather. At the present time the
summer clothing of the natives throughout Alaska is generally of cloth
obtained from white traders, but nothing brought from more civilized
countries can replace the parkies, fur trousers, skin boots, and
waterproof shirts or _kamlaykas_. These articles, except the last
mentioned, are largely used by white men, especially if making winter
journeys.
The boats in use among the Innuits are still the _kayak_ and the
_oomiak_, for which civilized man can offer no adequate substitute. The
well-known kayak, made of a light framework of wood, tied with thongs,
over which is tightly stretched a dressed sealskin covering, leaving
only one or two circular openings for the occupant, is in use from
Greenland all about the arctic coast of America to Asia. Different
shapes pertain to different tribes. In recent years, as a result
of outside influence, openings for three occupants are sometimes made,
the size of the boat also being increased. To one familiar with boat and
canoe travel these light skin craft, with their water-tight decks, seem
the perfection of boat construction. The occupant lashes the skirt of
his kamlayka about the raised rim of the opening in which he sits and
the boat is thus rendered impervious to water from whatever direction.
The greatest danger is that the parchment-like covering may be ruptured,
as by the cutting edge of thin ice. To ordinary storms, however, they
are more safe than even the deservedly celebrated "whale-boat" of the
white man. The oomiak, or woman's boat, also made of dressed skin
stretched over a frame, is much larger than the kayak, has a flat
bottom, is without deck covering, and designed for the use of many
occupants. As is well known, boats of each of these types are propelled
by means of paddles. Both the kayak and oomiak are still in every-day
use, and it is to be hoped the boats of the white man will never wholly
replace them.
The changes in house-building and dress referred to, which have come
from contact with white men, are outward signs of a great modification
in the lives of the Innuits, which began in the early days of Russian
occupation and has continued with increasing importance to the present
time. The natives are quick to imitate the customs of the strangers who
have visited them, and but for the restraint that the climatic
conditions have put upon them and the high price in furs demanded by
traders for imported goods the changes thus produced would be far more
marked than is now the case. To some extent the food of the natives has
been modified, flour being in demand, but, with minor exceptions, the
principal articles consumed are still such as are obtained by hunting
and fishing.
The greatest change that has taken place in the condition of the Alaskan
Innuits, and one which, perhaps, culminated at the time of the recent
"gold excitement" on the Yukon and at Cape Nome, is in relation to the
introduction of intoxicating liquors and of certain contagious diseases.
These scourges, coming from the south, have been almost as great
a blight among the native peoples as would be the sweeping southward of
a wave of arctic temperature to the vegetation of tropical lands. The
_curse of contact_, resulting when a civilized race invades a land
inhabited by childlike aborigines, as has been seen in many parts of the
world, has overtaken the Innuits in common with nearly all other tribes
in Alaska, and decadence and the prolongation of a miserable existence,
unless cut short by extermination through starvation, is all that
seemingly can be hoped for.
The fur-bearing animals of Alaska have been greatly reduced in numbers
during the last twenty-five years: the caribou and the moose have, to a
marked degree, been killed or driven to remote regions; the larger
whales, on account of overcapture by American whalers, have become
scarce; the sea-lion and the walrus are nearly extinct; the fur-seal, of
more importance to the Aleutians than the Innuits, is rapidly
approaching extinction. Thus in many ways the food supply is greatly
decreased. Recourse to agriculture is impossible. The one redeeming
feature of the white man's aggression is the introduction of the
domesticated reindeer from Asia and Lapland. With reindeer, the salmon,
not as yet depleted in the streams emptying into Bering Sea, the white
whale, the hair-seal, not as yet of commercial value, the countless
birds of summer, the berries of the tundra, etc., the Innuits can
survive, maintain their manhood, and become useful to civilization in
certain ways if the curse of drink and the spread of imported diseases
could be stopped. Such a change, however, for various reasons, is not to
be hoped for. It may perhaps be said that the influence of missionaries,
and, what is vastly more important, the work of the school-teacher, has
opened to these children of the cold northern land a way to
civilization, but the results up to the present time are not reassuring.
The census of 1890 showed that the Innuits of Alaska numbered 13,045. In
the census of 1900 a separate enumeration of Eskimos and Indians was not
made.
The dismal picture I have been compelled to sketch of the present
condition and future prospects of the Innuits of Alaska, in order
to indicate their status at the opening of the twentieth century,
applies also with variations in detail and some hopeful signs to a large
majority of the other aboriginal tribes of North America.
_The Aleutians._--The aboriginal inhabitants of the Aleutian Islands are
termed Aleuts or Aleutians, a word of obscure and perhaps foreign
derivation. As stated above, they belong to the Eskimo family, but are
more widely separated from the parent stock than any other of its
constituent tribes. Evidence advanced by W. H. Dall tends to show that
they are of American continental origin. At the time of the first coming
of the Russians, about 1750, they were at war with the Kaniagmuts, who
inhabited the greater part of the Alaskan peninsula and were the nearest
tribe of the Innuits.
When discovered by the Russians the Aleuts were an active, sprightly
people, fond of the dance and of festivities. They are of lighter
colour, but not perhaps in general more nearly white than the
full-blooded Innuits. At present it is difficult to find even a single
representative of unmixed descent, Russian occupation having stamped out
or greatly modified nearly every native characteristic both of body and
mind. They were originally a robust people, of about the average height
found in civilized countries, with coarse black hair and scanty beards.
Their island life, where no large game invited inland journeys, made
them emphatically "canoe people." The habit of sitting in their kayaks
and using the muscles of the upper portion of the body in paddling,
throwing the spear, etc., while the lower portion of the body received
but little exercise, led to a fine chest development and to undersized
and comparatively weak legs. The women, to whom the use of the kayak was
not intrusted, were better proportioned than the men, and many of them
are pleasing in appearance. As stated by Dall, they were less determined
than their neighbours on the mainland, the Kaniagmuts, but were by no
means devoid of courage. Their mode of worship partook more of the
character of a religion than that of any other of the Eskimo tribes in
their native condition.
From what can be learned of the Aleuts in their uncontaminated native
state, they seem to have been the most intelligent of all the Eskimo
tribes and the one which gave the greatest promise, if treated humanely,
of advancement when civilization was introduced. Less than a century of
contact with Russian invaders, however, led to a depth of degradation
that is only paralleled and possibly not exceeded by the shameful
results of the Spanish invasion among the aborigines of the West Indies.
One of the darkest chapters in American history, fortunately for the
credit of Europeans now largely lost, is that containing an account of
the brutal treatment the Aleuts received at the hands of the Russians.
The childlike natives became worse than slaves. The debauchery of their
oppressors was shameful. As stated by Dall, "the Aleuts were subjected
to the most horrible outrages. The names of Glottoff and Solóvioff (two
Russian explorers, 1764-'65) make them shudder to this day. Thousands
perished under sword and fire. Long after those enormities were checked
the Russians considered the Aleuts as beasts rather than men," etc.
Their numbers, estimated at 10,000 in 1799, were, according to a Russian
census, reduced to 5,238 in 1808, and, as stated by Dall, numbered not
more than 1,500 in 1870. The census of 1890 gives it as 967.
The incentive to Russian oppression was the greed for furs and the lust
of rude men at a distance from all centres of control. The Aleutian
Islands and neighbouring waters is the home of the sea-otter, which is
clothed with the most beautiful of all furs. Near at hand are the
Pribilof Islands, to which the fur-seal formerly resorted each summer in
countless numbers, and during its migrations traversed the passes
separating the islands of the Aleutian chain, where they were easily
taken; the commercial value of their skins previous to about 1867,
however, was small. In addition, the land-otter and several species of
foxes also inhabited the same region. These allurements tempted the
Russians, and besides the Aleutian Islands, with their sheltered
harbours, furnished favourable stations from which to extend the fur
trade into the still greater region to the eastward, and at an
early date in the foreign occupation of Alaska became a basis for
supplies.
The entire fur trade in Russian America was placed by charter in the
hands of the Russian-American Fur Company in 1799, which, like the
Hudson's Bay Company, had territorial jurisdiction as well as trade
monopoly. This powerful company maintained its existence under various
renewals of its charter until the purchase of Alaska by the United
States in 1867. The authority conferred on the Russian company gave it
exclusive right to purchase furs from the natives, and thus to dictate
prices. This system was fraught with evil to the natives, and their
extinction would no doubt have resulted had it not been for the
influence of missionaries of the Russian-Greek Church, among whom the
name of Veniaminoff will ever be held in blessed memory. In a measure
the gross oppression of the Russians brought its own punishment to the
offenders. The decrease in the number of the Aleutians meant a decline
in the number of pelts secured. To insure the gathering of the highly
prized furs the native hunters must be maintained. The later days of
Russian occupation were characterized by more humane treatment of the
natives, schools were established among them, liquors withheld, and
their rapid decline checked. When Alaska was purchased by the United
States the Russian-American Fur Company was supplanted by the Alaskan
Commercial Company, to whom a lease of the Pribilof Islands was granted.
In this lease provision was made for the support and education of the
Aleutians on the Pribilof Islands. As the chief and almost the sole
employment open to the Aleutians during the past thirty years has been
the taking of sealskins on these islands, this wise provision had a
beneficent influence on the entire tribe. How faithfully the Alaskan
Commercial Company carried out its contract has been seriously
questioned, but it is, nevertheless, a fact that the Aleutians have
fared better under American than under Russian rule. A gradual adverse
change in their condition has come about, however, owing to the decrease
and threatened extinction of the sea-otter, and the great decline in the
number of the fur-seals owing to the attacks made on them during
their annual migrations, which amounts to commercial extinction. The
lucrative industries of the natives have thus practically disappeared,
and there is nothing to take their place. The surviving members are
objects of charity, but as yet the United States Government has made no
adequate provision for their support. One method of ameliorating the
existing adverse conditions that is practicable is the introduction of
domesticated reindeer; another, not so easy to accomplish, is the
suppression of the liquor traffic.
THE INDIANS
The aborigines of the New World to the southward of the narrow strip of
arctic coast-land inhabited by the Eskimo are designated by the term
Indian, as already explained. There is no sharp line of demarcation
between the Indians of North and South America, one shading into the
other, but only those of the northern continent are here considered.
In many scientific treatises, as well as in books of travel and general
literature, the Indians are frequently referred to as "red men," and the
term "copper coloured" commonly applied to them. To the writer each of
these expressions seems infelicitous. It is true that throughout America
the Indians have a reddish undertone in their colour, but in numerous
tribes it is not pronounced. As to copper colour, the meaning of the
term is vague. What is copper colour? Presumably the colour of the pure
metal when unoxidized. No such colour is more than suggested even by the
aborigines having the lightest skins in the members of the many tribes
that have come under the writer's notice. A more correct term--but this
is a matter of opinion, in which differences are permissible--would be
brown, of which many shades occur, ranging from light cinnamon colour to
dark chocolate, and even nearly black. There is no recognisable
connection between variations in colour and climatic conditions. The
faces, hands, and other freely exposed portions of their bodies are
darker than the parts usually covered with clothing, and frequently
suggest the appearance of bronze statutes not fully darkened by
exposure to the weather. In colour they more nearly approach that of the
Polynesians than any other peoples, but in general are of a darker hue.
The members of the various Indian tribes, although presenting a wide
range of differences, have many physiological and mental resemblances,
which, like their languages, serve to set them apart from all other
peoples. A composite picture of their persons would show a man sinewy
rather than heavy in build, but there are many exceptions; of average
stature, 5 feet 8 or 10 inches, but there are tribes whose average is
more, and others in which it is less; dark brown, with a reddish
undertone, in colour; deep-set, black, and in general small eyes, their
alignment straight; the nose prominent and frequently well shaped; mouth
large, with strong, frequently perfect teeth; lower jaw massive; and
face beardless or nearly so, and the hair of the scalp long, coarse, and
black. In order to make such a sketch realistic, the bronze-like
athletic figure must be clothed in a blanket worn with the grace of a
Roman toga or wrapped in a robe of bison-skin; the feet encased in
moccasins of tanned deerskin, and usually decorated with beads or
variously coloured porcupine-quills; the face striped, dotted, or
blotched with various colours; the coarse hair falling like a thatch to
the shoulder, or braided, and in certain tribes shaved or plucked,
except only the traditional scalp-lock, and decorated with feathers,
most frequently of the eagle; necklaces, rings in the ears, amulets,
etc., made of the claws of the bear, shells, beads, quills, etc.,
bespeak various tribes; the primitive weapons were the hatchet-like
tomahawk, the bow and arrow, and the spear. The Indian has been
idealized in the writings of poets and novelists, but occasionally, even
at the present day, one meets with an approach to the ideal. Judged by
the standards of civilization, as he is seen to-day on numerous
reservations and about the streets of towns, he is a lazy, dirty
vagabond. A far more favourable and agreeable picture is presented,
especially in the eastern portion of Canada and adjacent States to the
south and in the Indian Territory, where the blessings of civilization
have been accepted and the once roaming savage has become a tiller of
the soil, an owner of cattle and sheep, and lives in a comfortable
house supplied with furniture such as white men use.
While a racial likeness impossible to conceal unites all of the various
tribes, no single picture or generalized description, however carefully
prepared, can convey to one unfamiliar with the Indian an accurate idea
of his personal appearance. A typical example from one tribe when
critically studied is found to differ widely from an equally
representative example of another tribe, not only in speech, dress,
methods of wearing the hair, ornaments, etc., but also in physique and
in mental traits.
In temperament the Indian is usually described as being moody, reserved,
wary, grave, and his face expressionless, the current of his thoughts
being unrevealed in his proud, indifferent bearing. In his own mind he
seems to consider himself superior to all other beings, and to regard
them with contemptuous indifference. All this is true enough as seen by
a stranger, but in his home life, and not infrequently when in the
presence of trusted white men, the mask of indifference is laid aside
and the laugh and jest indulged in. The extreme of assumed indifference
is exhibited, as has been well attested by many witnesses, when death by
torture is inflicted on a captive, as, for example, burning alive, when
no outward sign is permitted to reveal his intense suffering.
The Indian is a hunter and fisherman both from inheritance and
necessity. From his mode of life his sense of sight and of hearing have
become wonderfully acute. His skill in following a trail is proverbial.
When living near the sea or by the side of streams and lakes he is as
much at home in a canoe as his relative of the plains in post-Columbian
days when seated on his hardy pony. In current literature, however, all
of these traits, as in the case of the personality of the Indian, have
been fused into one ideal. It is true that the Indian hunter is more
skilled in following a trail, in interpreting the signs and sounds in
the forest, in shooting the foaming rapids in his frail canoe, etc.,
than the average white man to whom such pursuits are incidental or newly
acquired; but many white men, and particularly those who have in a
measure degenerated and assumed the Indian mode of life, are his
equal, if not his superior, in all that pertains to woodcraft.
In mental qualities the Indian is the inferior of the Caucasian and the
Asiatic, but is the superior of the negro. The ability to advance is not
absent, and capacity to reach a certain grade in civilization is
general, but beyond the acquirement of indifferent skill in the arts,
literature, etc., but few have passed. The mental quality of
perseverance under adverse conditions and of continuous application has
not been granted him.
These children of the forests and plains, easily pleased and as easily
angered; kind to their children and friends, but cruelly revengeful when
enraged; treasuring a kindness, but never forgetting an injury; without
rigid self-control, as is sadly illustrated by their inordinate passion
for liquor when once a taste for it is acquired, are plastic organisms,
which reflect the conditions under which they have developed. These
untutored barbarians, descendants from ancestors who brought little with
them save the stone axe and the stone spear, but of necessity originated
all their arts and institutions without contact with other peoples, and
were exposed to a wide range of climatic and other physical conditions
for many centuries, present a most instructive subject for the study of
the geographer and others who are interested in the relation of man to
his environment.
_Resources._--To the Indian in pre-Columbian days no ships from overseas
brought supplies, and as the various tribes were frequently at war with
their neighbours, trade relations were greatly restricted. Intertribal
barter was carried on, however, and the capture of supplies and utensils
of various sorts by one tribe from another favoured their dispersion.
Although such articles as the native copper of the Lake Superior region,
the red pipe-stone (catlinite) of Minnesota, and obsidian from various
places found its way to remote localities, each tribe had essentially to
supply its wants from the natural resources of its own domain. The range
in raw materials, to borrow a modern commercial term, that the Indian's
intellectual development permitted him to utilize is indicated in the
following table:
{ Animal: Mammals, birds, reptiles, fishes,
{ crustaceans, insects, and at times human flesh.
{
{ { Wild--roots, bulbs, seeds, fruits, nuts,
{ { bark, berries, sap.
Used for food. { Vegetable { Cultivated--maize, cacao, melons,
{ { squashes, tomatoes, sweet potatoes,
{ { potatoes, pineapple, (tobacco).
{
{ Mineral: Salt, (earth in certain instances).
{ Animal: Skins, sinews, tendons, hair, wool,
{ feathers, and cochineal for dyes.
{
Used for clothing. { Vegetable { Wild--bark, fibres, roots, dyes, gums.
{ { Cultivated--cotton, aloe (?)
{
{ Mineral: Dyes, such as ochres and cinnabar,
{ charcoal.
{ Animal: Skins, sinew, etc.
Used in the {
construction of { Vegetable: Logs, bark, seeds; grass, roots, etc.,
houses. { for mats.
{
{ Mineral: Stone, adobe, sods, earth, selenite
{ (caves).
{ Animal: Skins, sinew; oil in paint; quills, shells,
{ etc., for decoration.
Used in making {
boats. { Vegetable: Tree trunks, bark, seeds, pitch.
{
{ Mineral: Asphaltum; metallic oxides, etc., for
{ paint.
{ Animal: Bones, horns, skins, scales, teeth, shells.
{
{ Vegetable: Wood, bark, nuts, leaves, fibre, dyes,
{ pitch.
Used in making {
utensils and { Mineral: Soapstone for pots, pipes, etc.; obsidian,
weapons. { flint, etc., for spear and arrow points, knives,
{ scrapers, etc.; various hard stones and pebbles
{ for axes, mortars, pestles, etc.; copper for axes,
{ knives, etc.; mineral dyes; gold and silver.
{ Animal: Skins, hair, fur, bones, hoofs, claws,
{ teeth, ivory, oil in paints; shells, coral,
{ pearls, feathers, quills, scales, etc.
Used as personal {
ornaments and in { Vegetable: Seeds; fibres for mats, basket-work, etc.
the decoration {
of houses, { Mineral: Stone (turquoise, emerald, jasper, mica,
boats, etc. { catlinite, etc.), clay, gold, silver, meteoric
{ iron; and various metallic oxides, cinnabar, etc.,
{ for paints.
In these several ways, and yet others, as in their games, medical
practice, elaborate religious ceremonials, mortuary customs, modes of
travel, etc., the aborigines utilized a wide range of materials supplied
by nature, and supplemented them by horticulture, and to an exceedingly
limited extent by domesticating animals. The degree to which they
utilized the natural supplies was much less in certain directions than
became possible to civilized people, but several sources of raw
materials prized by them have not been called upon by white men, and are
now in greater or less measure abandoned by the natives
themselves. The vast mineral wealth of the continent was almost entirely
unavailing to the aborigines, except so far as native metals were
discovered; while several articles, such as the camass, the seeds of
grasses, insects, etc., for food and material, used for implements, as
obsidian for arrow points, spears, and knives, catlinite and other
stones for pipes, porcupine-quills for decoration, etc., are of small
value to Europeans. While civilized man has become more and more
independent of climatic and other natural conditions, largely through
the aid of commerce, the aborigines were much less resistant and were
forced to adjust themselves to their environment, and like other plastic
organisms, were modified by it.
_The Natural Food Supply._--The food of the Indians was mainly the flesh
of mammals, birds, and fishes. The smaller deer of various species
inhabited the entire continent from the subarctic forest to Panama. The
range of the bears was equally extensive, but in certain instances, on
account of superstitious fear, were not customarily used for food. The
almost universal source of food supply furnished by the smaller deer was
supplemented at the far north by the Barren Ground caribou, succeeded
southward by the woodland caribou; overlapping the range of the latter
and extending farther south was the moose; this, in turn, was
supplemented and exceeded in southern range by the Wapiti (elk); more
restricted was the range of the mountain-sheep and mountain-goat, each
inhabiting the Pacific mountains; on the Great plains roamed the bison
and the antelope, the former extending from the central Atlantic
seaboard to the Snake River plains, and the latter from the subarctic
forest to Mexico. The mammalian food supply was most abundant in the
temperate belt, and while decreasing northward, declined more rapidly
towards the south. The food supply furnished by fishes was plentiful
wherever water was present, and in superabundance in tidal rivers and
estuaries both on the Atlantic and Pacific coasts; but these resources
fluctuated in a conspicuous way with seasonal changes, owing especially
to the annual migrations of the shad and salmon. Supplementing the
highly desirable fish-food on the ocean shores were the molluscs,
and especially the oyster and the clam. The rivers, particularly of the
Mississippi Basin, supplied fresh-water "clams" (_Unios_), and the
saline and alkaline lakes of the arid region, inclusive of Mexico,
teemed with the larvæ of insects, which were utilized for food. In the
Atlantic and Mississippi region, south of the Great Lakes and extending
to Central America, lived the wild turkey; the forests of the Atlantic
and Pacific coasts, the vast prairies, and the no less extensive
sage-brush plains to the westward were inhabited by various species of
grouse; the land east of the Pacific mountains, from the Gulf of Mexico
far northward, was darkened by immense flights of pigeons; the water
from the far south to the far north, throughout the breadth of the
continent, were visited by large numbers of swans, geese, ducks, and
other water birds. In a conspicuous way the feathered hosts, valuable
for food, were migratory, thus again introducing a variable quantity
into the lives of the aborigines.
The vegetable food of the Indian tribes that did not practise
horticulture varied from locality to locality, and in the temperate and
more northern regions fluctuated through a wide range with seasonal
changes. Berries were abundant in certain regions and at certain
seasons. The raspberry, blackberry, huckleberry, strawberry, etc., of
many varieties, grew wild in the eastern Mississippi and Atlantic coast
regions. The huckleberry extended from the northern Atlantic coast
regions westward across the continent on the southern border of the
subarctic forest, and reached central Alaska. On the coast of British
Columbia and Alaska to Mount St. Elias, salmon-berries, wild currants,
huckleberries, and strawberries flourished with marvellous luxuriance
and of large size. Wild cherries were abundant on the Atlantic coast and
extended to the Pacific mountains. Certain small plums of value for food
occurred widely in what is now the United States. The papaw and
persimmon thrived in the southern portion of the Atlantic coast region.
The fruits of the cacti yielded refreshment in the southwestern States
and in Mexico. Throughout all the hardwood forests of the Mississippi
Valley and the region south of the St. Lawrence a large variety
of nut-bearing trees, such as the walnut, hickory, chestnut, beechnut,
oak, etc., were in great abundance and furnished a large annual food
supply. In the northern portion of this region grew the maple, the
saccharine sap of which was utilized by the Indians for making sugar. In
the Pacific mountains south of Canada grew the piñon, perhaps of all the
trees of the continent the species that yielded the greatest food supply
to the Indians. In this same region, particularly to the northward, grew
the small lily-like plant having a blue flower, known as the camass, the
bulbs of which are highly nutritious. Both the piñon and the camass are
largely utilized even at the present day for food by the Indians. In
Mexico, Central America, and the West Indies a large number of tropical
fruits, bulbs, nuts, etc., abound, which are suitable for food, and, as
we have more or less direct evidence, were utilized by the Indians of
that region in prehistoric times. The period of harvest at the south is
less sharply defined than in temperate latitudes and the natural food
supply subject to less seasonal fluctuations.
The Indians so long as they did not engage in agriculture--there being
an absence of anything that could be termed commerce, and even the
transfer of food and other supplies by barter being restricted--were
obliged to move from place to place, in order to avail themselves of the
abundance furnished in certain localities and at certain seasons. This
is well illustrated at the present day. With the coming of the salmon in
the rivers of the northwest Pacific coast region the Indian feasts by
the river-side; when the berries ripen in the valleys of the Cascade
Mountains he is there, together with the bears, to profit by the
bounties of nature; in Nevada he still makes journeys to the piñon
groves in October; and in the subarctic forest he accompanies the
migration of the caribou. In former days he followed the movements of
the herds of bison on the Great plateaus. In these and many other ways
the food supply of the Indian tended to establish nomadic customs, and
as each source of fuel and other supplies demanded different methods of
capturing animals or different utensils for gathering seeds,
etc., variations in culture development was a necessary result. The duty
of replenishing the general stores was shared by all, but there was no
definite organization for this purpose, and certainly nothing worth the
name of business management. As the adage is, "What is every one's
business is no one's business," and for this reason the Indian, as a
rule, failed to lay aside a sufficient supply of food for winter use,
and in consequence frequently went hungry and not infrequently died of
starvation.
The scarcity of the spontaneous food supply at certain seasons or during
exceptional years, and the recurrence of cold or rainy seasons,
necessitating shelter, would naturally lead the Indian to develop in two
important directions, namely, agriculture and architecture. As is well
known, promising advances had been made in each of these arts, when
indigenous development was checked and to a great extent killed by the
appearance on the scene and subsequent encroachments of peoples from
over the sea.
_Horticulture._--Concerning the art of cultivating plants for food,
clothing, utensils, etc., practised by the Indians before the coming of
Europeans, it is difficult to obtain accurate information. The writings
of Spanish and other explorers who first visited various tribes have
been diligently searched in this connection by students of American
history, and although much that is instructive has been discovered, many
questions remain unanswered.
The principal regions where cultivation of the soil was practised in
pre-Columbian times are situated in the United States south of the St.
Lawrence and east of the Mississippi Valley, and inclusive of the lands
bordering the Great Lakes on the south; also much of New Mexico,
Arizona, Mexico, Central America, and the West Indies. In the eastern
portion of what is now the United States localities naturally devoid of
trees were cultivated by the Indians, and partial clearings were made in
the vast forest by deadening the trees, probably by girdling or cutting
the bark entirely around their trunks with stone axes, and leaving them
standing. A similar process was employed by white settlers in later
years, and is practised even at the present day. In these partial
clearings, from which the underbrush was no doubt burned, gardens of
maize, melons, pumpkins, beans, gourds, sunflowers, potatoes, tobacco,
and perhaps other plants were grown without irrigation. Garden-beds, as
they are termed, are still to be seen in the forests of Michigan, which,
as indicated by the trees growing on them, are older than the time white
men began the cultivation of the soil of that region. In the arid
southwestern portion of the continent and in Central America gardens
were cultivated with the aid of irrigation, and what has been described
as a high degree of skill in horticulture attained. The chief products
of these gardens were maize, cotton, tobacco, beans, melons, cacao,
bananas, and the red pepper. Possibly vanilla, tomatoes, and pumpkins
were also grown. The aloe was extensively utilized in the south, but
whether definitely cultivated or not seems uncertain.
The cultivation of fruit-trees other than the cacao, which furnishes the
seeds from which chocolate is made, does not seem to have been carried
on, although certain writers imply that native trees were tended and
given greater facility for growth by removing adjacent plants. It is
stated by some authors that in the region to the eastward of the
Mississippi the Chickasaw plum is now found growing in clearings that
were abandoned by the Indians and not elsewhere, and the inference is
that it was formerly cultivated. Asa Gray mentions, however, that this
species is probably not indigenous.
Of domesticated mammals none are known to have been possessed by the
Indians except the dog, which it is presumed was derived from one or
more species of the native wolf, and was used to carry or draw burdens,
served also for food, and furnished skins for clothing and hair for
weaving cloth. The turkey was domesticated by the Aztecs and the village
Indians of the New Mexico region; among the latter, even at the present
day, eagles are confined in cages and plucked for feathers. There is
seemingly no doubt but that in pre-Columbian, as in recent years, the
young of wild animals were captured by the Indians and reared as pets,
which in times of necessity probably served for food; but there are no
records of definite attempts to domesticate the bison, mountain-sheep,
mountain-goat, or the peccary of the Gulf coast and Central America. In
the attractive accounts that have appeared in recent years concerning
the grandeur of the Aztecs mention is made of extensive menageries, but
even the most poetic of historians has not assigned to the tribes of
that confederation flocks and herds. The llama and the paco or alpaca,
although reared extensively by the Incas of Peru, are not certainly
known to have been introduced into North America.
To the eastward of the Mississippi, where numerous earthworks bear
testimony of an early settlement by aborigines, heavy forests, the
severity of the winter climate, and wide variations in summer rains
combined to make the natural conditions to a marked degree adverse to
aboriginal development. In Central America, and the West Indies
generally, the exuberance of vegetable growth is such as almost to defy
the clearing of land by people provided only with stone or copper
utensils. Between these two regions, in the southwestern portion of the
continent, are the arid lands, where, when once the idea of irrigation
was embraced, the conditions favouring a sedentary life, with
agriculture as a basis, are far more auspicious than elsewhere. The land
is there treeless, the indigenous plants are easily killed by fire and
by irrigation, the soil is rich, intense sunshine favours plant growth,
and the gathering of harvests is not delayed or the efforts of industry
rendered abortive by rain. Of all portions of the continent, this is the
one where resistance to human development is least, providing man's
ideas are sufficiently advanced to permit him to grasp and put in
practise the art of irrigation. It is reasonable to suppose that the
Indian there first began to build permanent homes and to cultivate the
soil. This hypothesis is sustained in part by historical evidence, and
in part by the ruins of ancient villages or communal houses, irrigation,
ditches, etc. From this centre it may be presumed, in the absence of
definite proof, that the art of horticulture spread to Central America
and the Mississippi Valley.
In spite of the glowing accounts given by certain historians concerning
the high degree of skill in agriculture attained by the
aborigines of Mexico and Central America, and the extent of their
plantations, a conservative balancing of the evidence indicates that
they never advanced beyond the stage of gardening, and that field
agriculture, the cultivation of orchards, and the domestication of
mammals was practically unknown to them.
[Illustration: FIG. 36.--Lodge or Tepee, Blackfoot Indians, Manitoba.
Photograph by William Notman & Son.]
_Houses._--The houses of the primitive Indians, owing to the various
stages in culture attained by different tribes and differences in
climatic conditions, showed a wide range in material used and in the
results obtained. The shelters of the wandering tribes and of the
village Indians during their journeys were usually some form of tent,
either composed wholly of boughs or of a framework of sticks over which
skins were spread and secured by thongs. The typical _wigwam_ consisted
of a number of poles from 15 to 18 feet long, lashed together at the top
and arranged in a circle some 10 feet in diameter at the base, on which
a covering of skins, bark, or mats was spread, leaving an opening at the
top for the escape of smoke from a small fire placed on the ground
within. At the top a wing-like extension of the covering was frequently
provided which could be adjusted to the direction of the wind. An
opening on one side, protected by a curtain of skin, or closed by
drawing the covering together, served as a door. A modification of this
genuine Indian lodge, or _tepee_, in which cotton cloth is substituted
for the primitive covering, may be seen over a wide extent of the
country to the west of the Mississippi at the present day (Fig. 36).
A step higher than the usually circular lodge of boughs, etc., in use
principally among the Indians to the west of the Mississippi, was
furnished by the bark houses of the northeastern tribes, as those of New
York, in which a rectangular frame of poles with an arched or triangular
roof was covered with bark, usually of the elm, tied to the inner frame
and held also by an external frame of poles, the two frames being lashed
firmly together. This, the celebrated "long house" of the Iroquois, like
most Indian houses, was designed to accommodate a number of families,
and may be said to have consisted of several houses placed end to end
with a common passageway running through them. Fires were lighted
in this passageway, one for each family, and the smoke allowed to escape
through openings in the roof. One of these bark houses is described by
an early traveller as being 80 feet long, 17 feet wide, and with a
common passageway 6 feet wide running through its length, on each side
of which were apartments 5 feet square. Smaller houses, usually for the
use of a few families, were also built. The larger ones, as was common
in many Indian villages, were occupied both as dwellings and for general
assemblies. These houses were grouped in villages, about which
palisades, consisting of poles planted in the ground, were frequently
built, and in at least one instance a ditch filled with water was used
on the outside of the palisade to increase their security against
attack.
The feature of special interest concerning the houses of the American
aborigines, inclusive of the Eskimos, is that they were usually occupied
by a number of families. This communal idea runs through all the
indigenous American architecture. As remarked by Lewis H. Morgan, one of
the most judicious students of American ethnology, "the house for a
single family was exceptional throughout aboriginal America, while the
house large enough to accommodate several families was the rule.
Moreover, they were occupied as joint tenement-houses. There was also a
tendency to form these households on the principle of gentile kin, the
mothers with their children being of the same gens or clan."
The idea of the joint tenement-house, as has been clearly shown by
Morgan, illustrated by the bark cabins of the Iroquois, finds its most
striking expression in the communal houses, or _pueblos_, of the village
Indians of New Mexico and Arizona, and in the abandoned stone houses of
Central America. In the arid southwestern portion of the continent
certain tribes, termed the Pueblo Indians, are still living in the
villages they occupied when first visited by Spanish explorers (1640).
On account of their exclusiveness and the isolation of their villages in
an immense desert region they have been but slightly modified, so far as
their home life is concerned, even at the present day, by contact
with white men. The hot desert has shielded these people in much the
same manner that the frozen tundra has served to preserve the purity of
the Eskimo.
The homes of Pueblo Indians, as described by Morgan, are immense
tenement-houses, built of stone and adobe, frequently occupying several
acres of ground, and from 1 to 6 or 7 stories high. The number of
inhabitants at Zuñi, one of the most typical of these pueblo towns, is
stated to have been 1,500 in 1851, but to have previously included some
5,000 souls. The adobe, of which the houses are largely constructed, is
the soil of the region, which when mixed with water and allowed to dry
becomes sufficiently hard to retain indefinitely in an arid climate the
form given to it. The soil is formed into bricks, and also used as a
mortar to unite rough stones. Although much stone was used in the
construction of the pueblos, it was roughly dressed by hammering, or not
changed at all from its natural condition, and regularly cut and carved
stones do not occur in the buildings. The pueblos were built in
successive terraces, usually either in a semicircle or on three sides of
a rectangle, the open side being protected by a wall. Irregular forms
are also known, the general plan being adapted to the natural condition
of the site chosen. In certain instances the structures were placed on
elevations where a high degree of safety was insured, but others are on
the open plain and even at the base of a commanding eminence, and near
enough to be reached by arrows shot from a bow. Protection against
enemies was increased by an absence of openings in the exterior walls,
except at a considerable height above the ground; ingress and
communication from terrace to terrace being by means of ladders, which
were drawn up or their steps removed in times of danger. The roofs of
the pueblos, as may be seen at Zuñi at the present day, are flat and
consist of poles covered with adobe.
The controlling ideas in the construction of the pueblos seems to have
been communal residence and defence. The houses are at the same time
tenements and fortresses. A characteristic feature of these, as of
practically all Indian villages, is the presence of one or more
assembly rooms, and of open courts or plazas, where the people gathered
for council, worship, amusement, etc.
When white men first visited the Pueblo Indians they cultivated gardens
with the aid of irrigation in which maize, mostly of a blue colour, was
the principal crop, and had domesticated the turkey; earthen vessels of
large size, frequently elaborately and pleasingly decorated, were
manufactured; cotton fabrics were woven of spun threads, and the men
were armed with bows and arrows and shields; clothing was made of
dressed deerskins, buffalo-robes, and cotton cloth usually dyed dark
blue. The descriptions of the Pueblo Indians given by the first visitors
from civilized peoples would, to a great extent, apply to them at the
present day, although in reality their lives have been profoundly
modified and their indigenous development checked.
Throughout a wide extent of the arid southwest the ruins of ancient
pueblos, irrigation canals, remnants of pottery, the latter frequently
marking village sites on isolated eminences, bear witness of a formerly
widely spread people. This evidence shows also that the ancestors of the
present tribes have inhabited the same territory for a great length of
time. In this same general region are found the houses of the
cliff-dwellers, who excavated rooms in the faces of precipices,
frequently high above their bases and only accessible by means of holes,
serving as steps, cut in the rock, or with the aid of ladders. In many
instances these ancient cliff-dwellers, of which no certain descendants
remain, took advantage of natural caverns, or of overhanging ledges,
which were closed by means of walls of rough stone and adobe.
[Illustration: FIG. 37.--Panorama of Uxmal, Yucatan.
In the foreground at the left is the Pyramid-temple of the
Magician, _A_, with its small court at the right-hand base.
Connecting immediately with this is the Nunnery quadrangle,
_B_, occupying the greater part of the foreground. Behind the
latter, on the ground level, are two massive ruined walls
usually referred to as the Gymnasium, _C_, and rising behind
this is a great triple terrace, on the second level of which,
at the right, is the House of the Turtles, _D_, and crowning
the summit is the Governor's Palace, _E_. To the right and
beyond is the serrated crest of the House of the Pigeons, _F_,
overshadowed on the left by the massive pyramid, _G_, and
backed up by a temple-crowned pyramidal pile of inferior
dimensions, _H_. To the left of the House of the Governor and
beyond is a group consisting of two pyramids, _I_, and on the
right of the Nunnery quadrangle, and some distance farther
away, are other ruined masses, one only coming fully within the
limits of the picture.--_W. H. Holmes._]
The pueblo dwellings, built largely of adobe, are stated by ethnologists
to have extended southward into Mexico, and illustrate the nature of the
houses in which the Aztecs lived, but the highest type of aboriginal
architecture in America is furnished by the dwellings and so-called
temples, palaces, etc., still standing in Yucatan and other portions of
Central America. In these ruins we have abundant example of buildings
made of cut stone, laid in regular and even courses, united with
mortar composed of burned lime and sand, and elaborately sculptured in
bas-relief and in the round, or covered with designs moulded in stucco.
In size and proportions these unique structures are impressive. The
so-called Governor's Palace at Uxmal, Yucatan, is 320 feet long, 40 feet
wide, and 25 to 26 feet high, and surmounts an artificially constructed
platform of earth 35 feet high and approximately 550 feet square.
This platform is terraced and provided with broad flights of stone steps
(Fig. 37). These dimensions will serve to render more instructive the
accompanying sketch of the principal ruins at Uxmal by W. H. Holmes.
[Illustration: FIG. 38.--Examples of Maya Arches. After W. H. Holmes.
_a._ Section of cuneiform arch with acute apex, Chichen-Itza.
_b._ Section of ordinary arch with flat capstone.
_c._ Section of ordinary arch with dressed surfaces.
_d._ Section of ordinary arch with dressed surfaces and curved
soffit slopes.
_e._ Portal arch with long slopes, showing masonry of exterior
facing.
_f._ Section of trefoil, portal arch of Palenque.]
Mere size and their great number are not the significant features of
these ruins. They are well built, of cut stone, and most elaborately
decorated, as may be seen by the accompanying reproduction of a
photograph of a typical example. In reference to the skill displayed by
the unknown architects and builders, Holmes, one of the most recent as
well as the most critical of Central American travellers, remarks as
follows:
"The stone used is the pale-yellowish and reddish-gray, obscurely
marbled limestone of the locality.... The facings and ornaments are all
cut and sculptured with a masterly handling not surpassed where chisels,
picks, and hammers of iron and steel are used, and the faces and contact
margins are hewn with perfect precision. Though the finish of the
surfaces was often secured by means of abrasion or grinding, picking or
pecking were the main agents employed, and the indents of the tools are
often apparent and wonderfully fresh-looking. The stones were set in
mortar, although in many cases the joints are so perfect that the mortar
does not appear on the surface."
The extensive ruins of Uxmal, although only a part of the treasures
concealed in the forests of Central America, express with an eloquence
not as yet fully appreciated the advanced stage of culture and
refinement attained in America from the growth of indigenous ideas. Some
of the special features illustrated by them from which the degree of
mental development of their builders can be judged is the presence of
the wedge-shaped but not of the true arch. The character of the simplest
and perhaps the first style of arch constructed by the awakening peoples
in many lands are shown in the accompanying sketches, borrowed from
Holmes's most instructive report. Columns, both square and round, were
used, and statues both in bas-relief and in the round are common. The
designs, whether of animals, grotesque monsters, feathers, or
plants, are in strong relief, either cut in stone or moulded in stucco.
These designs are not confined to single stones, but embrace several
blocks, and together with the diaper fretwork extend the entire length
of even the larger structures. Accompanying the well-wrought figures of
men, and at times forming separate inscriptions, are many hieroglyphics,
the meanings of which are still unknown. All or nearly all of the
structures stand on artificial platforms, which are terraced. A terraced
pyramid, with a broad flight of steps on one or more sides, surmounted
by a well-proportioned rectangular building, faced with cut stone,
highly decorated, and with a flat roof, are the larger features of the
Maya ruins.
[Illustration: FIG. 39.--Sculptured Façade of Governor's Palace, Uxmal,
Yucatan.
This very handsome and elaborate piece of work is a section of
the embellished entablature zone of the palace. The height from
the lower or medial moulding below to the coping course above
is about 10 feet. The entire length, covering the four walls of
the building, is some 725 feet. If we allow that the stones
employed average 6 by 12 inches in surface dimensions, this
deeply coffered and relieved mosaic would comprise upward of
20,000 pieces, all specially cut and a large percentage
elaborately sculptured. Two plain coping courses are seen at
the top, followed by a twined fillet moulding, while under this
is a line of very ornate snouted masks. The broad space below
is filled with bold fretwork, set on a lattice ground and
interrupted by the wonderful overdoor trophy, the central
feature of which is a human figure, fully life size, sculptured
in the round and seated in a niche with festooned base. The
head [now displaced] was surrounded by an elaborate and
colossal head-dress, most of which remains. The horizontal bars
terminating in serpent heads at both ends are separated by
lines of hieroglyphs.--_W. H. Holmes._]
All of this and more, as can be read in the elaborately illustrated
books of Stephens, Holmes, and others, shows that the Maya people, at
the time they were crushed by the more than cruel Spanish invasion, had
reached a stage in their development but little short of true
civilization.
_Ethnological Studies._--The native dress of the Indians, their boats,
ornaments, and still more their customs, systems of government,
religions, myths, traditions, etc., offer attractive subjects for study,
which are being earnestly pursued by many students at the present time.
The closing decade of the nineteenth century witnessed a true awakening
of the white people of America to an interest in the many relics
of ancient earthworks, buildings, utensils, etc., found throughout the
continent, and a healthy growth of an earnest desire to record all that
can be learned concerning the representatives still remaining of the
vanished peoples to whom they pertain.
In the van of this important work is the Bureau of Ethnology of the
Smithsonian Institution. Important work has also been carried on by the
Peabody Museum of Archæology, situated at Cambridge, and more recently
has been taken up in an energetic manner by the American Museum in New
York and the Field Columbian Museum at Chicago. The National Museum of
Mexico has assembled rich stores of archæological and ethnological
material pertaining to the native races of Mexico, and the Mexican
Government is doing much to preserve the priceless prehistoric monuments
of the republic from vandalism. There are also many private antiquarian
collections and many individual students who are doing good work along
their chosen historic, linguistic, and other branches of research. One
phase of this work, particularly in reference to ancient earthworks,
buildings, and also the observations of early travellers, missionaries,
explorers, etc., is the removal of the incrustation of romance, and in
part of fable, that has been formed about them. As shown by W. H.
Holmes, in reference to many reputed finds of the relics of men in
various glacial and other deposits; by W. H. Henshaw, in respect to
certain animal carvings; by Cyrus Thomas, in the case of the earthwork
of the eastern part of the United States; by L. H. Morgan, in connection
with the history of the Mexican and Central American aborigines and
other similar examples, imagination has only too frequently taken the
place of critical study and hasty generalizations have been given
publicity. It is perhaps not too strong a statement to say that the
fascinating histories pertaining to Mexico and Central America, written
by Irving, Prescott, and Bancroft, need to be thoroughly revised and
rewritten from the standpoint of the scientific ethnologist. This
clearing of the field of an underbrush of fancy is as necessary as the
work of the axe or _machete_ in removing the vegetable growths
that conceal many of the records of America's history.
_The Contact of the Aborigines with Foreign Peoples._--The chief
interest of the ethnologist concerning the American aborigines relates
to their condition before the introduction of European ideas and
customs. This external influence has been far-reaching and cumulative in
its effects, and to-day there is not a tribe in North America that
stands where it would have stood but for its coming. Among some of the
Eskimo tribes, and in the case also of certain Indian communities in
central Alaska and northern Canada, there have been but slight
modifications even in dress, utensils, etc., by reason of contact with
the white man. The Pueblo Indians have been resistant to change, but
although still grinding their blue corn in primitive stone hand-mills,
and dressed nearly as the first Spanish visitors found their ancestors
in the same villages, there has been a slowly progressing revolution in
the undercurrent of their thought, ideas, religion, customs, etc.
Whether this change is for the better or the worse depends on the point
of view. In attempting to judge of it from the Indian's side, the only
possible conclusion seems to be that the coming of the white man has
been a curse.
The reception of Europeans by the Indian, although in many instances
kindly, has, in the main, been but an outward show of friendship,
concealing suspicion, fear, and jealousy. That this distrust was well
founded is abundantly proved by history. Since the slaughter and
enslavement of the aborigines of the West Indies and of the southern
portion of the continent by Spaniards, through all the bloody conflicts
of the English and French with the Indians of the Atlantic and
Mississippi regions, to near the close of the nineteenth century, almost
constant war, marauding, murder, rapine, and jealousy have accompanied
the contact of the aborigines and the whites. Although the Indians
succeeded in retarding the spread of civilization, they were not strong
enough to permanently check it. In the United States and Canada they
have been, to a great extent, dispossessed of their hunting-grounds by
so-called treaties, or by formal purchase, and placed on
reservations. In Mexico the struggle is still in active progress, but
there and in Central America and the West Indies the contact of the two
races has in part assumed a different phase, and one less visibly
detrimental to the Indian. In the countries now held by people of
Spanish descent, and in fact throughout Latin America, as it is termed,
amalgamation has, to a great extent, caused the disappearance of the
Indian race in its purity. North of the indefinite boundary where the
Spanish language is largely spoken much less admixture of the two races
has occurred than farther south, and the half-breed is classed as an
Indian. While to the north of Mexico it is possible to trace the
post-Columbian histories of the Indian tribes with an approach to
completeness and to state their present census, and note the results of
the attempts that have been made to civilize them, to the south of the
Mexican boundary such a task is seemingly hopeless.
In Alaska the Indians still roam at large with no other restraint than
that arising from the adjustment reached through intertribal relations,
with slight modifications due to the widely scattered settlements of
white men. No attempt has been made by the United States Government to
place them on reservations, and this will probably not occur, as the
white man does not wish their lands for agricultural purposes.
Displacement by contact seems to express the change now in progress.
In Canada the present condition of the Indians varies with locality. In
the southeastern part, including the maritime provinces, they have been
greatly changed from their native condition, and to a large extent
gathered on reservations or have settled on land of their own and become
self-sustaining. In the Labrador region and throughout the Rocky
Mountains they still roam at will, and depend mainly on hunting and
fishing for a livelihood. On the Pacific coast, the Haidas, etc., of
British Columbia--and the same is true of their neighbours, the Tlingits
of southeastern Alaska--have become interested as labourers in the
commercial fisheries, principally the salmon industry.
The Canadian Government has purchased extensive tracts of land
from the Indians, and the purchase money, together with the returns from
the sale of relinquished lands, etc., amounting in 1900 to $3,893,623,
is held in trust for their benefit. The interest on this sum, together
with appropriations made by the Government for the support, education,
etc., of the Indians, amounted during the year 1900 to $1,309,127. The
total--in part estimated--Indian population of Canada is about 99,000,
and those classed as resident Indians number 77,450. The last-named
during the year 1900 cultivated 108,850 acres of land; owned 83,019 head
of cattle, horses, sheep, etc.; cut 68,395 tons of hay; gathered 471,596
bushels of potatoes and other root crops, besides an output of
$1,639,398 worth of fish, furs, etc. During the same year 9,634 Indian
children attended industrial schools. This is certainly a creditable
report and one encouraging to the hope that all the Indians in Canada
will in the course of a few generations become civilized, in spite of
the fact that the Indians outside of the reservations and beyond the
limits of the treaty lands still roam at large and to a great extent are
in a deplorable condition.
In the treatment of the aborigines within her borders Canada has to a
marked degree been both humane and just. Her policy in this connection
is largely an inheritance from that of the Hudson's Bay Company, whose
success in trade depended on maintaining friendly relations with the
native peoples. The work of the factors of "the Great Company" scattered
throughout Canada and carried on continuously for more than two
centuries did much to prepare the aborigines for civil government. Owing
largely, also, to the efficiency of the mounted police of Canada much
less trouble has been experienced in the management of the Indians of
that country than has been the case in the adjacent portion of the
United States. In any comparison, however, of the relation of the
Canadian and United States governments to the aborigines within their
respective borders account needs to be taken of the widely different
conditions on the opposite sides of the boundary line between them. Not
only are the Indians of Canada about one-third as numerous as in the
United States, while the area of each country is about the same,
but owing to a less dense white population to the north of the
international boundary, far less demand has there arisen for their lands
for agricultural, mining, and other purposes than in the United States.
The Indian problem within the United States has been a most serious one,
and is still a severe tax on the nation. The union of the colonies and
the final separation from the mother country left the United States with
an immense western frontier, extending in an irregular way from north to
south through the trackless forests of the Mississippi Valley. As the
nation grew in strength this frontier was pressed farther and farther
westward, while settlements established on the Pacific coast presented a
frontier to the eastward. These two inundations of civilization, crude,
but virile and aggressive, approached each other and entered the passes
in the mountains separating them. Between the two were the
hunting-grounds of the Indians, but the advance of the whites was
irregular and the outposts of civilization were in the Indian country.
In 1867 the buildings of the first of the transcontinental railroads
divided the region roamed over by savage tribes. Railroads continued to
be built, and presently there was no frontier. In a later stage in this
process of subduing a continent it became imperative that the more
hostile and treacherous Indian tribes should be either exterminated or
segregated and confined to definite regions, where they could be under
military surveillance. Many treaties were made between the United States
and the Indians, and by this means and by force the original occupants
of the land were placed on reservations. The aim of the Government, it
must be conceded, has during the past fifty years or more been humane,
but in many instances treaties have been unfulfilled, and individuals in
authority have proved incompetent, unfaithful, and dishonest. In judging
of the dealings of the white man with the Indian, it must be remembered
that the problem was highly complex and in certain ways of such a nature
that no result just to each party was practicable. On one hand, the
rights of the Indian to the land they inherited from their ancestors was
to be recognised, but a larger interest, the march of civilization, had
also to be encouraged. The good of humanity demanded that the barbarian,
roaming over broad lands of which he made no use except for hunting,
should give place to more enlightened people, who wished to cultivate
the soil and make it support thousands of individuals, where before only
a few hundred could find sustenance. The history pertaining to so many
countries, where civilized peoples have displaced races in the lower
stages of culture, was here repeated. The main issue was the same, only
the details differ. In the struggle between the white and the red man it
became evident that the latter must yield, assume habits of industry,
and earn his bread by the sweat of his brow or be exterminated. It may
be said that neither of these seemingly inevitable results has occurred;
the Indian has not been exterminated, and possibly not seriously reduced
in numbers, and to a great extent is not self-supporting. It is
believed, however, that this is but a transient stage, resulting from
the reservation system. In a large number of instances the lands
formerly occupied by the Indians have been purchased from them by the
Government and thrown open to settlement by white people. The money due
for these purchases has in several instances been paid to the Indians,
either as tribes or individually, while in other cases it is still held
in trust by the Government, and the interest on it used for the benefit
of the original occupants of the land.
The United States Government by treaty with certain of the tribes, as
the Sioux, for example, has agreed to pay definite annuities and issue
to each individual a certain amount of clothing and food each year.
Other tribes placed on reservations were also granted clothing and food
sufficient to keep them from want, although no agreement to that effect
was entered into, the theory of the Government being that the Indians
deprived of their hunting-grounds should receive aid until they could
adopt the ways of civilized men sufficiently to be self-supporting. The
number of Indians assisted in this way each year during the past decade
has been about 85,000. The food issued, usually twice a month, consists
of meat, either beef or its equivalent in bacon, flour, coffee,
and sugar. The ration supplied each individual is sufficient to maintain
a person, or at least keep him from starving, but is not intended to
meet all his wants. The desire on the part of the Government that want
should compel the Indian to work, has been still further pressed by a
gradual decrease in the ration issued in certain instances where
definite agreement has not been made and where a tendency to
self-support is manifest. In general, however, this assistance, instead
of stimulating industry, and, as would seem natural, gradually leading
the recipient to desire and obtain more and more of the comforts and
luxuries that may be had as a reward of exertion, served but to enhance
his inherited aversion to all forms of labour. The issuing of rations
even to the extent of insuring the Indian against starvation has to a
great extent removed the incentive to industry, and the Indian, being an
Indian, has remained thriftless and indifferent. The reservation system,
so far as attaining the main aim in view, namely, the civilizing of the
Indian and encouraging him to work, has, to a great extent, been a
failure.
In addition to the issuing of food and clothing, the Government, with
the view of extending still further encouragement, has in a large number
of instances provided the Indians with tools, horses, agricultural
implements, etc., and aided in irrigation and other schemes tending to
the improvement of the lands comprised in reservations.
Besides the direct material aid just referred to, schools have been
established, and an earnest and widely extended effort made to educate
the Indians and make them worthy of citizenship. The result of this
effort, while highly encouraging in many individual instances, has on
the whole fallen far short of what was expected in view of the large
expenditures incurred. The sum thus employed during the past
thirty-three years is about $240,000,000. The total appropriation made
by the Government for the care and education of the Indians, inclusive
of the aborigines of Alaska, for the fiscal year ending June 30, 1901,
was over $9,000,000. Of this sum, over one-third was expended in the
maintenance of schools. In addition to this provision there are a number
of mission and other schools, supported mainly by religious or
benevolent organizations, and certain public schools not receiving aid
from the General Government which were wholly or in part for the benefit
of Indian pupils.
In the case of the larger of the Government Indian schools the Indian
children are removed from their homes and placed in institutions where
they live for a period of four years under military discipline. In these
schools literary is subordinate to industrial training. The majority of
the schools are equipped with shops for shoe- and harness-making,
carpentry, blacksmithing, wagon-making, etc., and in several instances
the girls are taught cooking and house-work. The largest of these
schools is situated at Carlisle, Pennsylvania, at which the average
attendance during the year 1900 was 961. The extent to which education
is spreading through the Indian tribes and its rate of increase are
indicated by the fact that the attendance on the Government schools has
increased from 3,598 in 1877 to 21,566 in 1900.
While the benefits received by the Indians through the issuing of
clothing, rations, and by education has been great and the seed for
future progress sown broadcast, the results, so far as lifting the
recipients into an atmosphere of refinement and civilization and making
them self-supporting are concerned, are far from encouraging. The
Indians in general are still wards of the Government and not worthy of
citizenship.
The aim of the Government is not only to educate the Indians, but to
induce them to adopt the ways of industrious and progressive white men,
build homes on land ceded to them and which they may hold as
individuals, thus breaking up their long-established practise of
communal or tribe ownership, and finally become citizens of the
republic. To this end land has been divided among the heads of families
of several tribes and titles in severalty granted, with restrictions in
most, if not all instances, in reference to the sale of the land within
a certain period. In many instances this plan has been productive of
good results, and the Indians have become industrious and to a large
extent citizens. The numerous successes that have followed the
allotment of land in severalty, accompanied as it is with
responsibilities and the necessity of self-support, is encouraging and
leads to the hope that in the course of a few generations all the
Indians will have passed from the condition of barbarism to one of
civilization.
In Mexico since 1824 the Indians have been on the same political basis
as the whites, although to a great extent they have failed to profit by
their advantages, and so far as legal restrictions are concerned are
eligible to any office of the republic. The brightest example of the
wisdom of this policy is furnished by the fact that in at least one
instance a man of pure Aztec blood has occupied the highest office in
the gift of the people. In general, and in fact almost universally, the
position of the Indian in Mexico is that of a farm labourer, but
although nominally free, owing to a prevalent system of debt, he is
really held in vassalage by the owners of the large plantations or
_haciendas_. In many ways his condition is but little better than that
of a slave. Unlike the roaming tribes of the more northern portion of
the continent, where the food supply fluctuates greatly with the
seasons, the natives of Mexico early became sedentary, and, owing no
doubt in part to the density of the population, became horticulturists,
and have continued to cultivate the soil to the present day. They are
now essentially agriculturists, wedded to their place of birth, and not
only do not desire change, but repel by passive resistance the invasion
of civilization and the use of new and improved tools and machinery.
They are non-progressive, and on account of their great numbers,
constituting about 38 per cent of the entire population, serve to retard
advancement in a manner that is highly detrimental to the enlightened
and progressive members of the ruling class. Education in nearly all
parts of the republic is compulsory and the schools free. With both
political and educational advantages, however, but indifferent progress
towards civilization has been made.
The present condition of the Indians throughout Central America is
similar to that of the descendants of the Aztecs and other tribes in
Mexico both politically and socially. They are a disheartened
race, living in a region where exuberant nature supplies their small
wants with but little exertion on their part, and incentives to activity
either of body or mind are, to a great extent, lacking.
In the West Indies the native Caribs were nearly exterminated by the
Spaniards early in their occupation of the islands, their places as
labourers being supplied by the importation of negro slaves, and at the
present time but few, if any, Indians of pure blood are to be found.
Throughout Mexico, Central America, and the West Indies amalgamation of
the Indian with both Europeans and negroes has taken place, and a mixed
race, consisting of a large percentage of the total population, has
resulted. In Mexico these _mestizos_, as they are termed, number about
5,000,000, or about two-fifths of the entire population. In the Central
American republics the supplanting of the aboriginal race by the same
process is thought to have progressed at about the same rate as in
Mexico.
To the student of geography a comparison of the state of the aborigines
of North America before peoples from other lands came among them, with
reference to the influence of environment, is full of significance. The
highest degree of culture and the greatest advance towards refinement
was in Mexico and Central America, where a uniform climate prevails and
bodily wants are few and easily supplied. It was there that skill in
architecture reached its highest development, and what is worthy the
name of art, and we may almost say letters, but in truth
picture-writing, reached a high degree of advancement.
This marked progress in a tropical country beyond what was attained by
the Indian tribes in the temperate and cold portions of the continent
seems to be an exception to the general rule that intellectual progress
is stimulated by changeable climatic conditions, and reaches the highest
development in cold, temperate climates. Apparently the degree of
stimulation needed for the Caucasian and the Indian differs, and the
latter thrives best where the obstacles to be overcome are least. This
is in harmony with the oft-repeated statement that the Indian is but a
child. The struggle which would discourage the boy is but zest to
the man. Among the Indians themselves, however, we find an exception to
the rule suggested in the fact that the Iroquois or the Six Nations of
New York, in their tribal organization and alliances of offence and
defence probably surpassed even the Aztecs and Mayas. In physical
strength and endurance, and in mental powers, so far as government and
oratory are concerned, the Iroquois probably surpassed all other
Indians; but in architecture, art, picture-writing, etc., they were far
the inferiors of the Mexican and Central American Indians. Thus,
intellectual strength and vigour seem to have been most markedly a
product of the colder and more changeable climate, while the highest
attainment in architecture, etc., was reached at the south.
It is in the temperate region also that the best results have been
reached in attempting to civilize the Indians. This, however, cannot be
claimed as a result of climate simply, since the aid that has been
extended to them in Canada and the United States is far different from
the influence exerted on their relatives at the south by men of Spanish
blood. The results of the efforts of Canada and the United States to
civilize the Indian and make him worthy of citizenship, although costly
and slow in reaching the desired end, are full of promise. By the
methods referred to in the last few pages a strong effort is being made
to counteract the harsh treatment the Indians received during the
earlier years of French and English aggression, and to give them a fair
chance to advance. One important result of the present firm control is
the total cessation of intertribal warfare. Seemingly the aborigines
throughout North America, with the exception--and it is hoped this is
but temporary--of the Alaskan Eskimos and the still uncared-for Indian
tribes of Alaska and Canada, should increase in numbers as well as in
enlightenment. In reference to numbers, the enumerations that have been
made in recent years, although not exact, seem to indicate a diminution
in the rate of decrease, if not a positive advance. In the case of most
of the Indian tribes north of Mexico the change from a free life, passed
to a large extent in tents or temporary homes, to an inactive,
sedentary existence, mostly on reservations, and the influences of
house-life without a knowledge of sanitary conditions was a most severe
one. The adverse results of this change, it is probable, are not yet
past, but the rate of decrease in numbers resulting from it appears to
be diminishing. Aside from the comparative suddenness with which the
Indian has been forced to change his ways of thinking and living, it
must be confessed that there is something inherent in his mental
qualities that makes him unduly resistant to progress. As a race it is
not to be hoped that he can ever be placed on really equal terms with
the white man.
The total aboriginal population of North America in 1900, as nearly as
it is now practicable to ascertain, is shown in the following table:
{ Canada, Arctic coast 1,000
Eskimos. { Newfoundland (Labrador coast) 800
{ United States, Alaska (1890) 14,000
----------
Total Eskimo population, about 15,800
{ Canada 99,010
{ United States, exclusive of Alaska 270,544
Indians. { " " Alaska 15,500
{ Mexico (1895) 5,000,000
{ Central America (largely estimated) 1,600,000
---------
Total Indian population, about 6,985,054
---------
Total aboriginal population, about 7,000,800
In this enumeration no account is taken of the Indians of the West
Indies, for the reason, so far as can be learned, that there are few, if
any, of pure blood remaining.
LITERATURE
Vast stores of information concerning the aborigines of America
have been published by the Bureau of American Ethnology,
Smithsonian Institution, Washington, D. C.; the Peabody Museum
of Archæology, Cambridge, Mass.; the American Museum of Natural
History, New York, N. Y.; the Field Columbian Museum, Chicago,
Ill.; and in the _American Archæologist_, a monthly magazine now
printed by Putnam's Sons, New York.
Readily accessible books relating to the Eskimos of Alaska are:
DALL, W. H. _Alaska and its Resources._ Lee & Shepard, Boston,
1870.
PETROFF, IVAN. _Reports on the Population, Resources, etc., of
Alaska._ In the reports of the tenth and eleventh censuses of
the United States.
The condition of the Indians in the United States during the
past half century is recorded in the annual reports on Indian
affairs published by the Department of the Interior,
Washington, D. C. Similar information concerning the natives of
Canada may be found in the reports on Indian affairs issued by
the Canadian Government at Ottawa.
Of the numerous books on ethnology in which the relation of the
aborigines of America to other peoples is discussed, perhaps
the most useful to the general reader is A. H. Keane's _Man
Past and Present_, printed at the University Press, Cambridge,
England.
Of the many attractive books of travel in which the Indians of
Mexico and Central America and the ruins, etc., of the same
region are described, the most readily accessible are: John L.
Stephens's _Incidents of Travel in Yucatan_, 2 vols., and his
_Incidents of Travel in Central America, Chiapas, and Yucatan_,
2 vols., published by Harper & Brothers, New York, 1867-'68;
and W. H. Holmes's _Archæological Studies among the Ancient
Cities of Mexico_, published by the Field Columbian Museum,
Chicago, 1897.
CHAPTER VIII
POLITICAL GEOGRAPHY[6]
[6] As stated in the preface, several chapters have been omitted from
this book on account of limitations of space. The portions of the
original manuscript referred to relate to the geography of fisheries,
forestry, mining, commerce, agriculture, etc. In discussing each of
these themes, the control exerted by natural conditions or environment
on human affairs made itself prominent because of the immediate
influence of corrective failures when nature's laws are disregarded. A
less attractive phase of the study of the relation of man to nature is
furnished by political geography, in which the influence of something
opposed to environment becomes prominent, and as history shows has in
the main exerted a major control over the geography of nations. That
something, as is well known, is the greed of peoples. Space is here
claimed for a part of my original manuscript for the reason that it
presents a view of political adjustments not usually taken and in a way
perhaps pessimistical, which may awaken opposition, and also because it
contains a summary of the results of a long series of struggles among
various nations for the possession of the North American continent. Of
greater moment than the rivalries of nations for territory, as is also
outlined, is the conflict between two radically different principles of
government--the monarchical and the republican--in which this continent
has furnished the chief battle-grounds. Did space permit, the influence
of geographical conditions on the growth and development of the
fundamental ideas of government could be illustrated by American
history, and the probability that environment will in the end gain
ascendency over local self-interests in the establishing of national
boundaries made prominent.
Among the prominent facts dealt with in the study of political geography
and of history are the territorial limits of nations. For this reason
the characteristics of boundaries are of fundamental importance, and a
classification of them is convenient, if not essential.
CLASSIFICATION OF BOUNDARIES
The boundaries between nations, states, provinces, etc., established in
various ways, may be classified, at least provisionally, in six
groups. We may term these groups _coast boundaries_, _astronomical
boundaries_, _water boundaries_, _mountain boundaries_, _divide
boundaries_, and _arbitrary boundaries_.
_Coast Boundaries._--The junction of the sea and land on the borders of
continents and islands furnishes natural and sharply defined lines,
which are clearly the most desirable of any of the various classes of
boundaries for defining political limits. By international consent the
jurisdiction of a country bordering on the "high seas" is a line one
marine league seaward from the margin of the land, and following its
meanders. As an international dividing line the one-league limit seldom,
if ever, becomes important, since the nice adjustment of the width of an
arm of the sea necessary for such a purpose rarely occurs. When an
extension of the ocean's waters intervening between two nations is less
than two marine leagues wide the boundary between them commonly follows
its medial line, and has all the essential features of a water boundary,
described below.
_Astronomical Boundaries._--The shape of the earth and its motions in
reference to the sun are such that certain imaginary lines on its
surface may be located with precision by astronomers, and if the
monuments or other marks employed to show the positions of such lines
are removed they can be accurately relocated. The lines referred to are
principally parallels of latitude and meridians of longitude, and
boundaries, so far as they coincide with these lines, may for
convenience be classed as astronomical boundaries.
Examples of the class of boundaries here indicated are furnished by the
one defining the east border of the main body of Alaska, which, as
defined in a treaty made in 1825 between Great Britain and Russia, is
the one hundred and forty-first meridian west of Greenwich; and by the
boundary between Canada and the continental portion of the United States
from near the Lake of the Woods westward to the coast of the continent,
which, as finally decided in a treaty between Great Britain and the
United States in 1846, is the forty-ninth parallel of north latitude.
The boundaries of a number of the States of the United States and of
several of the provinces of Canada are either wholly or in part
parallels of latitude or meridians of longitude, and furnish good
examples of what are here termed astronomical boundaries.
The most conspicuous advantages of astronomical boundaries are that they
may be accurately described without a knowledge of the country through
which they pass. They can be located with precision and their courses
accurately marked by monuments. For these reasons astronomical
boundaries, when clearly defined in treaties between nations or in laws
concerning the territorial limits of states or provinces, leave no room
for contention as to their positions.
The leading objections to the use of astronomical boundaries,
particularly as international dividing lines, are: The temptation they
offer to diplomats and others, who may be interested in the speedy
conclusion of a treaty, to make hasty divisions of territory without
knowing its resources or commercial and other possibilities. Then, too,
such boundaries cross the land without reference to its topography, and
have no essential relations to the courses of streams or the directions
of coast-lines, etc. They may divide a fruitful valley in a most
arbitrary and inconvenient manner between two nations with widely
different laws and customs, or cross a navigable river at several
localities, and intersect a coast or lake shore so as to initiate
complex conditions in respect to harbours, navigation, customs duties,
etc. In these and still other ways boundaries coinciding with lines of
latitude and longitude are apt to bring about detrimental commercial and
other relations between adjacent nations, states, and provinces. A
region which is an industrial unit--as the gold fields of the Klondike
district, the iron-bearing tracts to the west of Lake Superior, the
wheat-lands of the Red River Valley, the forested lands of the northwest
coast, etc.--when divided between two or more countries with different
laws is deprived of the advantages that should follow from the natural
course of industrial development, and one part or the other suffers in
consequence.
[Illustration: PLATE VII.--Distribution of governments in North
America.]
Again, until an astronomical boundary is surveyed and marked on
the ground by skilled geodesists, it cannot be located even
approximately by miners, trappers, foresters, and others, and many
difficulties are apt to arise in this connection.
Although an astronomical boundary once decided on and formally recorded
in a treaty leaves no excuse for national quarrels as to its position,
it is evident that its far-reaching and perhaps highly complex
influences on the development of neighbouring peoples are likely to be
such that the natural resources, conditions affecting transportation,
etc., of the region through which it passes should be thoroughly
understood before a final decision is reached.
_Water Boundaries._--In numerous instances the medial line or one shore
of a stream, lake, estuary, strait, or other water body not recognised
as a part of the "high seas" has been selected to serve as a fence
between nations and states; collectively, such boundaries, typically
represented by a river without islands, flowing between well-defined and
permanent banks, may conveniently be termed water boundaries. In
general, when a stream, lake, etc., is a national or state boundary, its
medial line, or the centre of the deepest channel when there is more
than one, is defined as the precise line of demarcation.
The leading features of water boundaries are illustrated by a portion of
the line separating the United States from Canada, which traverses the
middle of the St. Lawrence River, and divides medially several of the
Great Lakes and their connecting streams. The south boundary of the
United States is also in part a water boundary, and is defined by treaty
as "the middle line of the Rio Grande, or its deepest channel where
there is more than one."
In certain instances, when a river, lake, bay, etc., separates two
political organizations, one shore or the other may be defined by treaty
or by law as the actual line of separation, and even complex relations
may exist, in reference to jurisdiction over the dividing waters. The
water boundary between New York and New Jersey, for example, is, in
part, the middle line of the Hudson and of New York Bay, etc., with
several qualifications, including exclusive jurisdiction by New
York over all the waters of the Hudson to the west of Manhattan Island
to the low-water line on the New Jersey shore, subject, however, to
certain rights of property and of jurisdiction of the State of New
Jersey, etc. The waters of Delaware River are, by agreement between New
Jersey and Pennsylvania, a common highway, over which each State "shall
enjoy and exercise a concurrent jurisdiction within and upon the water,
and not upon the dry land between the shores of said river"; the islands
in the river being specifically assigned to the one or the other State.
The advantages of a water boundary are suggested by the fact that in
most instances they may be easily located, even by persons inexperienced
in the method of surveying. Coinciding, as they generally do, with
definite geographical divisions, they do not lead in a conspicuous
manner to complications in the industrial development of the countries
or States separated by them.
The difficulties to which water boundaries may give rise are indicated
by the fact that streams, more particularly than the other water bodies
in question, frequently divide so as to inclose islands, and in certain
instances on nearing the sea send off, perhaps, several distributaries,
which discharge through independent mouths. When a stream divides so as
to inclose an island, even if the main or the deepest channel is
specified by treaty or by law as the one chosen as a boundary, the
question as to which of two channels is really the larger or the deeper
may not permit of definite answer. Streams are subject to many changes,
and what is the main channel one year may become of secondary rank the
next year, or a river, as not infrequently happens, may shift its course
bodily, and thus furnish grounds for contention as to the ownership of
the territory transferred from one of its banks to the other. The
distributaries of streams, or the separate channels into which they
divide on deltas, etc., are also subject to conspicuous and sometimes
sudden changes. Who could decide, for instance, which is the main
channel of such rivers as the Mississippi, the Nile, or the Ganges, in
the delta portions of their courses; or if a choice seemed practicable,
is there any assurance that the distributary largest to-day will
maintain its supremacy for a decade to come, or even be in existence a
century hence?
The controversies that may arise in reference to which of two channels
in a designated water body is the main one, are illustrated by the
well-known "San Juan episode," which came near bringing on hostilities
between Great Britain and the United States in reference to the
ownership of certain islands in the Strait of Georgia; the immediate
subject of contention being whether "the channel which separates the
continent from Vancouvers Island," as the statement reads in the
Webster-Ashburton treaty, 1846, passes to the east or to the west of the
San Juan Islands. The Emperor of Germany, as is well known, acting as
arbitrator, decided that the islands belong to the United States. Thus,
in 1872, a series of disputes as to the Canadian-United-States boundary,
which had been carried on for ninety years, was closed.
While water boundaries, and especially rivers, in certain instances,
have furnished almost ideal dividing lines between nations, in other
instances they have proved to be objectionable. The difference lies in
the nature of the streams themselves, and illustrates the fact that,
with water boundaries as with other classes of dividing lines between
nations, a critical knowledge of the geography of the region through
which they pass is a prerequisite of treaty making, if subsequent
boundary disputes are to be avoided.
_Mountain Boundaries._--The crests of mountain ranges, or mountain
chains, are sometimes specified in treaties as defining territorial
limits. The ideal mountain range is one having a generally straight
alignment and a continuous and sharply defined crest, but in nature this
ideal is seldom attained. Modern geographical studies have shown that
many so-called mountains, which from a distance appear to be
well-defined uplifts with sharp crest-lines, are in reality broad
plateaus or great domes, deeply dissected by stream erosion. In such
instances it is frequently difficult to decide where the crest of the
range is located. Indeed, as is not infrequently the case, there is no
definite and tangible crest-line. Although it is sometimes assumed that
the crest-line coincides with the water-parting, or the divide, between
the head branches of streams flowing in opposite directions from
a mountain-like uplift, it is well known that a mountain range, even
when bold and sharply defined, may not be a divide for the principal
streams of the region where it is situated. An illustration in point is
furnished by the Appalachian Mountains, through which the Susquehanna,
Delaware, and other important rivers rising in the plateau to the west
flow transversely in deep valleys and empty into the Atlantic.
The recent controversy between Argentina and Chile was due to an
assumption in a treaty between them that the crest-line of the southern
Andes coincides with the water-parting between the streams flowing to
the Atlantic and those discharging into the Pacific. Post-treaty
surveys, as they may suggestively be termed, have shown that in the
portion of the Andes in question streams rising well to the east of the
mountains flow westward through them in deep transverse cañons, and that
there is a wide discrepancy between the continental water-parting and
the topographic crest-line of the continent.
A mountain boundary, if defined as the line along which the upward
slopes on the opposite sides of a prominent uplift meet in its summit
portion, would in most instances be irregular and perhaps conspicuously
intricate, for the reason that mountain crests are modified and shaped
by erosion and migrate in one direction or another according to the
strength and other qualifying conditions of the opposite-flowing
streams. Then, too, an uplift which seems to a casual observer to be a
single mountain range, may in reality be highly complex, and no
continuous crest-line be discoverable. In short, the sweeping statements
sometimes embodied in treaties, to the effect that the line of
demarcation between contiguous countries shall be the crest-line of a
certain indicated mountain range are fraught with uncertainties and
difficulties, which are likely to prove a source of discontent and
costly arbitration, or even lead to war.
_Divide Boundaries._--A boundary which is defined as following a
specified water-parting or divide, from which streams flow in opposite
directions, would in most instances be easily traceable on the ground
even by persons unskilled in the art of surveying, and for this
and other reasons has much to commend it; yet, without an accurate
knowledge, and most of all an accurate topographic map of the region
through which such a boundary is to pass, its selection on general
principles, however nicely worded, is open to dangers of the same nature
as those pertaining to a similar choice of a mountain boundary.
In arid regions broad plateaus may form divides, and even an approximate
location of the line of water-parting, if one exists, be a matter of
difficulty and uncertainty. Then, too, the process of head-water
corrasion pertaining to essentially all streams, and of stream capture,
or the acquiring by one stream, through the process of stream
development, of the territory formerly drained by its neighbour, leads
to a migration and sometimes a sudden and perhaps extensive shifting of
a water-parting.
Examples of divide boundaries are furnished by the one separating Idaho
and Montana, which in part coincides with the continental divide, and
serves its purpose well; but the satisfaction it has given is to be
qualified by the fact that, for the most part, it is situated in a
rugged region, where there is but slight probability of the property
interests of the communities parted by it coming into direct contact.
Boundaries which are made to coincide with the courses of rivers, with
the crest-lines of mountains, or with water-partings, have certain
commendable features in common; they are easily located, readily defined
by natural features of the earth's surface, and in general do not
require to be accurately surveyed and marked by monuments before they
serve their purpose as international or interstate fences.
_Arbitrary Boundaries._--A class of boundaries not otherwise readily
definable may be conveniently designated as arbitrary boundaries, since,
as a rule, they are not described in terms such as pertain to
astronomical boundaries, and bear no necessary relation to topographic
or other features of the regions they traverse. Like astronomical
boundaries, the ones here considered are imaginary lines, and, in part,
might with propriety be included in that class, since they are capable
of being located by astronomical methods; but they serve our
purpose better if considered in a group by themselves. The class of
boundaries here referred to includes straight lines connecting two
points; lines defined as running in a given direction (azimuth) and for
certain distances; arcs of circles; tangents to circles, etc. In brief,
arbitrary boundaries may be defined as straight or curved lines or
combinations of such lines, and are similar to the lines employed by
surveyors in marking the boundaries of a farm, locating a railroad, etc.
An example of what is meant by an arbitrary boundary is furnished by the
line separating Delaware from Pennsylvania, which is an arc of a circle
12 miles in radius, with the steeple of the old court-house in
Newcastle, Delaware, as a centre. Again, in the establishment of the
District of Columbia, a rectangle 10 miles square was chosen and marked
on the ground by means of monuments as the site of the capital of the
United States. Another illustration is furnished by the eastern boundary
of California, as defined in its constitution. This boundary runs from
the intersection of 120 degrees of west longitude with the thirty-ninth
degree of north latitude in a straight line in a southeasterly direction
to the River Colorado, at a point where it intersects the thirty-fifth
degree of north latitude.
Boundaries of the nature just cited can only be recognised when actually
marked on the ground, and except in the case of straight lines, not of
great length, or small geometrical figures, are difficult of precise
location, even by skilled surveyors. Should the monuments used to define
their positions be destroyed, their replacement is an arduous task.
An interesting example of a change from an astronomical to an arbitrary
boundary is furnished by the line of demarcation between Texas and New
Mexico, which in part, as originally defined by law, was the one hundred
and third meridian of west longitude, but owing to errors in the first
survey was wrongly marked on the ground by monuments. The monuments,
however, having been accepted as indicating the position of the true
line of division, became points in an arbitrary boundary. Other similar
examples of the acceptance of an arbitrary in place of an
astronomical boundary are not uncommon.
_Impracticable Boundaries._--There are certain dividing lines which are
defined in treaties, decrees, etc., as running parallel to some natural
feature, as a coast or a river, and at a given distance from it, that
might with propriety be classed as arbitrary boundaries, since no effort
is made to adjust them to the natural conditions of the immediate
territory they traverse; but, for the purpose of expressing a still
greater weakness inherent in them, they are here specially designated as
_impracticable boundaries_. This, as is to be hoped, temporary class of
boundaries includes the proposed lines of demarcation sometimes inserted
in treaties, etc., which it is impossible, or at least impracticable,
without great and for the most part useless expense of time and money,
to mark on the ground, and thus seek to make serviceable.
In this connection reference may be made to the boundary between
southeastern Alaska and Canada, which, as stated in the treaty between
Great Britain and Russia previously referred to, in the absence of a
mountain range parallel with the coast and not over 10 marine leagues
inland--and as subsequent explorations and surveys have shown such is
the case--"shall be formed by a line parallel to the windings of the
coast, and which shall never exceed the distance of 10 marine leagues
therefrom." The region through which the line described would pass, if
surveyed, was almost entirely unknown at the time the treaty referred to
was made, but, as has since been discovered, it is exceedingly rugged,
and contains many mountains ranging from 10,000 to 18,000 feet high,
besides a multitude of glaciers and many extensive fields of perpetual
snow. To survey and mark on the ground the boundary indicated in the
treaty would be what may be justly termed an impossible task; and,
besides, if the line as defined by treaty should be established, it
would be intricate, and much less serviceable as a national fence than
any one of several possible boundaries that could have been chosen, with
essentially the same end in view, at the time the original treaty was
entered into, had a geographer been employed to make even a hasty
reconnaissance of the region in question.
[Illustration: PLATE VIII.--Characteristic vegetation.]
Another example of a boundary being defined as running parallel to and
at a specified distance from an irregular geographical feature is
furnished by a part of the boundary between Massachusetts and New
Hampshire, which is a line parallel to the Merrimac River, and distant
from it 3 miles on the north. In this case, although the distance of the
line designated from the one to which it is to be drawn parallel is but
3 miles, and the country between only mildly undulating or hilly, the
boundary as now marked on the ground and accepted as an interstate
boundary is but a rude approximation to the one originally defined.
These examples, and others that might with propriety be classified as
impracticable boundaries, illustrate again the desirability of accurate
geographical knowledge, and still more of an adequate appreciation of
the difficulties and limitations met with by the surveyor, on the part
of those who attend to the real-estate business of nations.
* * * * *
The line of separation between Canada and the United States, as defined
by the Treaty of Ghent, 1814, and after several subsequent adjustments,
was determined as indicated roughly on the accompanying map. Throughout
the greater part of its eastern half it is a river boundary, and in its
western half an astronomical boundary.
In 1876 the English Government granted Newfoundland jurisdiction over
Labrador, and in letters patent defined that dependency as "all the
coast of Labrador, from the entrance of Hudson Straits to a line to be
drawn due north and south from Ause Sableu on the said coast to the
fifty-second degree of north latitude, and all the islands adjacent to
that part of the said coast of Labrador." This line is still unsurveyed.
From the fifty-second parallel to the Strait of Belle Isle, a distance
of about 40 miles, the boundary is a north-and-south line situated about
7 miles west of the fifty-seventh meridian, as is indicated on the best
maps available.
The southern boundary of the United States, as finally determined in
1853 by treaty with Mexico, is, beginning at the east, a river
boundary for some 900 miles, namely, the middle of the Rio Grande, or
its deepest channel, when there is more than one, to where the river
crosses the parallel of latitude 31° 47'; continuing westward, the line
is in part an astronomical and in part an arbitrary boundary to the
Pacific.
The nature of the boundaries separating the several provinces of Canada,
the various States of the United States and of Mexico, the republics of
Central America, etc., are indicated approximately on the accompanying
map. These lines when studied on larger-scale maps on which the drainage
and relief are also shown reveal many features of interest.
POLITICAL CONTROL
The political subdivisions of North America in 1900 are too well known
to require specific description at this time. The long-continued
struggles and rivalries that have led to the present subdivision of
territory pertain to history, and although full of interest from the
point of view of the geographer, cannot be discussed in the present
treatise. Among the conspicuous events that might be shown by a series
of political maps is the contraction and final disappearance of Spanish
and French dominion from the continental mainland. The broad, indefinite
territory once belonging to Spain, which in the sixteenth century seemed
destined to expand still more and possibly embrace the whole of the two
Americas, has been diminished from time to time, until as a result of
the recent Spanish-American War her flag no longer waves over any
portion of the New World. The French territory, once embracing a large
portion of what is now Canada and the United States, is at present
represented by the islands Martinique and Guadeloupe with its
dependencies, in the West Indies, and the islands Miquelon and St.
Pierre, adjacent to the south coast of Newfoundland; in all, comprising
about 1,161 square miles. The French have, in addition, certain treaty
rights pertaining to fisheries on the northern and western shores of
Newfoundland.
Between the two forms of government, monarchical and republican,
North America is somewhat equally divided, so far as extent of territory
is concerned (Plate VII), but not as respects population. The people
under republican organization far outnumber those still acknowledging
allegiance to hereditary rulers. The countries self-governed, or forming
parts of American republics, embraced in 1900 all of the continental
mainland south of the United-States-Canadian boundary, together with
Alaska, Cuba, San Domingo and Haiti, and Porto Rico. The provinces,
islands, etc., still controlled by European powers are Canada,
Newfoundland, Bermuda, and all of the West Indies except the islands
just referred to, which are more definitely designated in the table on
page 424. The population of the American republics is in the
neighbourhood of 97,000,000, and of the European dependencies somewhat
less than 7,000,000. A republican form of government, more or less
definitely foreshadowed by the tribal confederations of the aborigines,
the most conspicuous example of which is furnished by the Iroquois or
"Six Nations," has thus become the characteristic feature of the
political organizations of North America; the same is true also of South
America. The New World is thus conspicuously republican, in distinction
from the Old World, which is characteristically monarchical.
The immigration to North America since its discovery by Columbus has
been from all the nations of the Old World, but most largely from
Europe. Negroes were brought as slaves, and their descendants, now free,
form a large percentage of the population, especially in the
southeastern part of the United States and the West Indies. Chinese,
since about 1870, have arrived in large numbers, but their immigration
to the United States is now restricted. Of the nations of Europe, the
strongest influx has come from Great Britain, France, Germany, Spain,
and Italy. To a marked degree this westward migration has been along
parallels of latitude, but the migratory streams on reaching North
America subdivided into many distributaries, and a mingling of
nationalities on a vast scale has resulted. This amalgamation has been
so great and so long-continued that several new and somewhat strongly
individualized nationalities have arisen, the most instructive
being in the temperate portion of the continent.
The dominant language, as in the case of political control, has been
inherited from Great Britain. English is the universal language to the
northward of Mexico and on certain of the West Indian islands. To the
south of the United-States-Mexican boundary, but beginning in the
southwestern portion of the United States, and including also the
greater part of the population of the West Indies, Spanish is the
current language, except among the uncivilized aborigines. French is
commonly spoken by many thousands of people in the province of Quebec,
Canada, and in certain of the West Indies.
The ideal nation, from the point of view of the geographer, is one so
situated that it is self-sustaining--that is, contains within its own
domain all the conditions necessary for its life and growth. It should
have favourable climatic conditions, agricultural land, forests, mines,
fisheries, etc. More than this, even if all material wants are supplied
from within its own border, intellectual desires demand outside stimuli.
The ideal nation should therefore touch the ocean, in order to have
avenues for travel open to its people. I am well aware that a more
commanding, or, perhaps better, a more modern view, would show that
improved methods of transportation have made the whole world
commercially one; but invisible tariff walls still separate peoples and
wars break lines of communication.
It might be expected that in the New World, conditions being also new
and room for development abundant, civilized nations would have adjusted
their boundaries so as to make an ideal subdivision of territory in
accord with natural conditions. A study of the boundaries separating the
nations of North America, however, fails to furnish evidence of such an
adjustment. On the contrary, even between the most highly civilized
countries, in which the people speak the same language, the dividing
lines are entirely arbitrary, so far as relation to soil, climate,
mineral and timber resources, fisheries, etc., are concerned. The line
separating Alaska and Canada is mainly a meridian of longitude, which
passes through a rich mining district. The southern boundary of
Canada is for the most part a parallel of latitude dividing
agricultural, mining, and timber lands. The material advancement of the
inhabitants on the opposite sides of these unnatural dividing lines is
retarded by them and the progress of civilization delayed. The same is
true of the invisible wall separating the United States from Mexico, and
the various partitions intersecting Central America. There has evidently
been but little, if any, tendency to draw the boundaries referred to in
conformity with natural conditions. What, then, is the force which sets
nature at naught? The reply is not obscure. In one word, it is _greed_.
"To have and to hold" is the unwritten motto of republics as well as of
monarchies.
The absurdity of disregarding geographical relations, and in consequence
checking national development, and leading to stagnation and to material
and intellectual decline, is sadly illustrated by the subdivision of the
West Indies. In an admirable account of the Caribbean region by R. T.
Hill, in which its present commercial depression is described and the
reasons for it judiciously analyzed, occurs the following passage
relative to the case in point:
"A greater drawback to the West Indies than the one-sided
agriculture--the raising of sugar-cane--is their political condition.
Their distribution among too many nationalities necessitates the support
of expensive and useless administrations, and prevents federation of
interests and the development of trade among themselves and with the
United States, the nearest and largest natural consumer of their
products. Very ridiculous some of these political conditions seem. The
island of St. Martin, not as large as an average county in the United
States, is divided into two principalities, the French and the Dutch,
each of which maintains an administrative force as large as that of the
State of Texas. Then, as we sail down the eastern islands, hardly a
score in number, and within sight of one another, aggregating in area
less than our little State of Delaware, about 2,000 square miles, we
find five foreign and no less than a dozen distinct colonial
governments, each responsible to Europe, with no shadow of
federation between them, or even cooperation of any kind--a condition
not only pitiable, but absurd. Why should Dominica, whose people are
French in language and institutions, be sandwiched in between Martinique
and Guadeloupe, and within easy sight of both, yet so cut off from them
by quarantine and tariff laws that it is commercially nearer England,
some 3,000 miles distant, than to its neighbours?"
The conditions necessary for an ideal, self-contained government were
briefly referred to above. In North America, perhaps, several such
eligible sites for a definite number of people might be chosen, but in
no case without the drawing of unnatural boundaries. The continent, as
is shown by its geology and geography, is a unit, and the most typical
of comparable size of any on the earth. These same conditions point to a
single political unit. Arguing from geographical relations simply, and
not considering the racial differences and local self-interests, the one
boundary in North America should be the shore boundary, except at the
30-mile-wide Isthmus of Panama. To the geographer North America presents
an example of a region containing within itself essentially all of the
elements necessary to a high industrial, social, educational, and
ethical development of its inhabitants. The industrial needs are met by
a range of products, whether of soils, mines, forests, or fisheries, as
varied or nearly so as is presented by the entire earth. Although the
continent is broadest at the far north, where climatic extremes prohibit
a dense population, yet in the temperate region, or between the mean
annual isotherms of 45 and 75, a space of some 1,200 miles in latitude,
it is from 2,500 to 4,000 miles wide. In this temperate region there is
at present greater commercial and mental activity than elsewhere on the
continent, and it is here that the dominant power of the future will be
located. Supplementing the agriculture, manufactures, etc., of the
temperate belt are the vast forested and fur-bearing regions on the
north and the exuberant tropical countries on the south. Each of these
three great regions are parts of a whole and mutually supplement each
other.
The distribution of the population of North America, in respect to
political subdivisions during the year 1900, is indicated, as nearly as
it has been found practicable to ascertain it, in the following table:
POPULATION OF NORTH AMERICA IN 1900
--------------------------------------------+--------------+-----------
Government. |Area in square|Population.
| miles. |
--------------------------------------------+--------------+-----------
_American Governments_ | |
| |
United States (inclusive of Alaska | 3,626,533 | 76,265,469
and Porto Rico)[7] | |
Mexico | 767,005 | 13,570,545
Guatemala[8] | 63,400 | 1,574,338
Salvador[9] | 7,225 | 803,534
Nicaragua | 49,200 | 420,000
Honduras[10] | 45,250 | 407,000
Costa Rica[11] | 23,000 | 310,000
Panama (Department of Colombia) | 32,380 | 290,000
San Domingo[13] | 20,596 | 1,244,650
Haiti[13] | 9,242 | 500,000
Cuba | 44,000 | 1,572,797
+--------------+-----------
Total for American governments | 4,687,831 | 96,958,333
| |
_Possessions still held by | |
European Governments_ | |
United Kingdom of Great Britain | |
and Ireland:[12] | |
Canada | 3,653,946 | 4,846,377
Newfoundland and Labrador | 49,734 | 201,934
Bermuda | 19 | 15,013
West Indies (Bahamas, Jamaica, etc.) | 12,059 | 1,357,254
British Honduras | 7,562 | 31,471
+--------------+-----------
Total for the United Kingdom | 3,723,320 | 6,452,049
France: | |
Miquelon and St. Pierre | 93 | 6,250
West Indies (Guadeloupe, | |
Martinique, etc.) | 1,068 | 354,790
+--------------+-----------
Total for France | 1,161 | 361,040
Denmark: | |
West Indies (St. Thomas, St. John, | |
and St. Croix) | 149 | 35,900
Holland: | |
West Indies (St. Martin in part, St. | |
Eustace, and Saba) | 29 | 7,236
+--------------+-----------
Total for European governments | 3,724,659 | 6,856,225
+--------------+-----------
Total for North America | 8,412,490 |103,814,558
--------------------------------------------+--------------+-----------
[7] The area of Alaska is 590,884 square miles; its population, 63,592.
The area of Porto Rico is 3,600 square miles; its population (1899),
953,243. Hawaii, not included above, has an area of 6,449 square miles
and a population of 154,000.
[8] In 1894.
[9] In 1896.
[10] In 1899.
[11] In 1891.
[12] In 1898.
[13] Together occupying the island Santo Domingo or Haiti.
LITERATURE
Twelfth Census of the United States.
_British America._ By several authors. Published by Kegan Paul,
Trench, Trübner & Co., London, 1900.
_Stanford's Compendium of Geography and Travel._ North America.
Vol. i, Canada and Newfoundland, by S. E. Dawson. Vol. ii, The
United States, by Henry Gannett; Central America and the West
Indies, by A. H. Keane.
HILL, R. T. _Cuba, Porto Rico, and the other West India Islands._
The Century Company, New York, 1899.
GANNETT, H. _Boundaries of the United States._ United States
Geological Survey, Bulletin No. 171, second edition, Washington,
1900.
INDEX
Aborigines, 355-407.
Adams, Mt., Wash., height of, 156.
Adirondack Mountains, brief account of, 83-84.
Adobe used for bricks, 389.
Agassiz, A., cited, 12, 21. Work of, in Caribbean region, 16.
Alaska, area and population of, 424.
Boundary of, 416.
Coast topography of, 45-46.
Indians of, 397.
Map of coast of, 47.
Alaska Commercial Company, 375.
Albemarle Sound, origin of, 42.
Aleutian Islands, topography of, 40.
Aleutians, brief account of, 373-376.
Aleuts, brief account of, 373-376.
Algonkian system, 310.
Allen, J. A., cited, 260, 290.
Alpine flora, 254-257.
American governments, enumeration of, 424.
Animal life, 258-298.
Anticlinal valleys, 78.
Antillean Mountains, brief account of, 169-171.
Antiquity of the aborigines, 357-363.
Apatite, 350.
Appalachian Mountains, description of, 74-82.
Map of, 74.
Archean period, 308-310.
Arches in Maya houses, 392.
Arctic climatic province, 203.
Arctogæic life realm, 259.
Areas of various governments, 424.
Arkansas Plateau, brief account of, 109-110.
Asbestos, 349-350.
Astronomical boundaries, 409-411.
Atlantic coastal plain, 62-64.
Forest, brief account of, 227.
Mountains, 60, 73-89.
Austral climatic provinces, 191-197.
Aves, orders of, 289.
Aztecs, advancement of, 364.
Badlands, brief account of, 110-111.
Bahama Islands, topography of, 19.
Baker, Mt., Wash., height of, 156.
Bald, Mt., N. B., height of, 85.
Bancroft, George, reference to, 395.
Barren grounds, absence of trees on, 253.
Bartlett Deep, 20.
Basement complex, 310.
Bay of Fundy, tides in, 29.
Bear, Polar, 266.
Bears, brief account of, 279, 282-284.
Bell, R., exploration by, 88.
Bermuda, area and population of, 424.
"Bermuda Mountain," 4.
Bering Sea, depth of, 2.
Bighorn, brief account of, 272-273.
Big trees of California, 242-246.
Bird migrations, 292-296.
Birds, brief account of, 289-298.
Bison, brief account of, 275-278.
Map showing range of, 276.
Blackfoot Indians, lodge of, 387.
Black Hills of Dakota, 116-119.
Boreal climatic province, 201-203.
Forest, 235-237.
Boston, Mt., Mo., height of, 92.
Boundaries, classification of, 408-418.
British Honduras, area and population of, 424.
Brownson Deep, 20.
Buffalo, brief account of, 275-277.
Cacti, 225-226.
California, boundary of, 416.
Cambrian system, 310-312.
Canada, area and population of, 424.
Boundary of, 417, 418.
Mountains of Western, 167-169.
Treatment of Indians by, 397-399.
Canadian Coast Ranges, 168.
Rockies, 167-169.
Cape Cod, map of, 37.
Hatteras, continental shelf bordering, 2.
Lisburne, depth of water near, 2.
Sheridan, tides at, 30.
Capulin, Mt., N. M., height of, 119.
Carborundum, 351.
Caribbean region, submarine topography of, 16-23.
Caribou, brief account of, 266-269.
Cascade Mountains, brief account of, 147-158.
Igneous rocks of, 316-322.
_Castor canadensis_, 279.
Catlinite, 379, 380.
Cats, brief account of, 284-285.
Cedar trees in Pacific forest, 240.
Census of various nations, 424.
Of aborigines, 406.
Central America, Indians of, 403-405.
Chamberlin, T. C., cited, 316.
_Characeæ_, lime secreted by, 335.
Chart of geological history, 309.
Chelan, Lake, Wash., 157-158.
Chesapeake Bay, origin of, 42.
Chickasaw plum, 385.
Chinook winds, 115, 204-205.
Classification of boundaries, 408-418.
Geological terranes, 308-309.
Clays, 345.
Climate, 173-214.
Elements of, 173-184.
Climatic provinces, 184-203.
Coal, 336-338.
Fields, map of, 336.
Coastal plains, 62-69.
Coast boundaries, 409.
Mountains, 162-169.
Topography of, 31-55.
Columbia River lava, 319-320.
Commercial geology, 328-353.
Communal dwellings of Indians, 388-389.
Concentration of mineral substances, 328-353.
Consequent drainage, examples of, 118.
Contact of aborigines with foreign people, 396-406.
Continental borer, description of, 89-120.
Shelf, 1-16.
Cope, E. D., cited, 260, 311, 312.
Coral growths on continental shelf, 6.
Reefs in the West Indies, 18.
Corundum, 351.
Costa Rica, area and population of, 424.
Crater Lake, Ore., brief account of, 153-155.
Map of, 153.
Cross, W., cited, 321.
Cuba, area and population of, 424.
Banks near, 20.
Culture of the aborigines, 363-365.
Currents, ocean, 23-27.
Cyclones, 208-212.
Cypresses, 233.
Dall, W. H., cited, 367, 373, 374.
Dana, J. D., cited, 300.
Davis, W. M., cited, 79.
Dawson, J. W., cited, 312.
Death Valley, Cal., 145.
Débris forming continental shelf, 5-8.
"Deeps" of the West Indies, 20-21.
Deer, brief account of, 271-272.
Delaware, boundary of, 416.
Bay, origin of, 42.
River, submerged channel of, 43.
Deltas, 52-55.
Denmark, possessions of, 424.
Dikes, 320.
Diller, J. S., cited, 152, 153, 164.
Dismal Swamp, brief account of, 63-64.
Divide boundaries, 414-415.
Dog, Eskimo, 266.
Drowned river-valleys, 43, 48, 49.
Dutton, C. E., cited, 134, 136, 153.
Economic geology, 328-352.
Edwards Plateau, Tex., brief account of, 107-108.
El Llano Estacado, brief account of, 106-109.
_Enhydra marina_, 278.
Eschscholtz Bay, Alaska, ice near, 68.
Eskimo, meaning of the word, 356.
Dog, 266.
Meaning of the term, 356.
Eskimos, brief account of, 365-376.
Census of, 406.
Estuaries, 55-58.
Ethnological studies, 394-396.
Evaporation, 212-213.
Fall line in Atlantic coast rivers, 66.
Ferns, 222.
Fir trees in Pacific forest, 240.
Flora, 215-257.
Florida, continental shelf bordering, 2.
Fontaine, W. M., cited, 312.
Food supply of Indians, 381-387.
Forests, description of, 217-249.
Map of, 215.
Fossil floras, 256.
France, possessions of, 419, 424.
Fur-bearing animals, 278-282.
Galveston, Tex., destruction of, 38.
Tides at, 27.
Gardens of the Indians, 384-387.
Gas, natural, 340.
Gaspé Peninsula, 84.
Geographical distribution of animals, 258-263.
Geology, 299-354.
Gilbert, G. K., cited, 118, 131, 321.
Glacial epoch, brief account of, 314-316.
Extent of glaciers during, 7-8.
Glacier Peak, Wash., height of, 156.
Glass sand, 333.
Glottoff, reference to, 374.
Gold, 345-346, 351-352.
Mountains, Canada, 168.
Governor's palace, Uxmal, 393, 394.
Grand Cañon of the Colorado, 134-135.
Sketch of, 135.
Gray, A., cited, 389.
Great Abaco, reference to, 18.
Great Bahama Bank, brief account of, 18.
Basin, brief account of, 136-146.
Basin, map of, 137.
Lakes, 99.
Plains, brief account of, 102-106.
Plateaus, brief account of, 102-106.
Salt Lake, Utah, 140-142.
Valley of California, 158-161.
"Greater St. Lawrence," 9.
Growth of the continent, 300-306.
Guatemala, area and population of, 424.
Gulf of California, 49.
of Mexico, continental shelf on border of, 1-2.
of Mexico, map of west coast of, 38.
Plains, brief account of, 94-95.
Stream, 16.
Stream, volume, etc., of, 24-25.
Haida Indians, 397.
Haiti, area and population of, 424.
Harbours, 53-58.
Harney Peak, S. D., elevation of, 116.
Hawaiian Islands, 4.
Hawaii, area and population of, 424.
Hayden, F. V., cited, 113.
Hayes, C. W., cited, 79.
Heilprin, A., cited, 260.
Henry Mountains, Utah, 131, 321.
Henshaw, W. H., cited, 395.
Hetch Hetchy Valley, Cal., 150.
High plateaus, brief account of, 132-134.
Hill, R. T., cited, 22, 169, 220, 422.
Map by, 17.
Holland, possessions of, 424.
Holmes, W. H., cited, 390, 392, 393, 394.
Honduras, area and population of, 424.
Hood, Mt., Ore., height of, 156.
Hornaday, W. T., cited, 277.
Horticulture by Indians, 384-387.
Houses of Indians, 387-394.
Innuits, 368-369.
Hudson River, submerged channel of, 8-9, 43.
Humboldt, A. von, cited, 12.
Huxley, T. H., cited, 259.
Hydrocarbons, 338-342.
Ice, changes in coasts due to, 50-51.
Subsoil, in Alaska, 68.
Deposited débris on continental shelf, 6-7.
Palace, Montreal, 199.
Igneous rocks, brief account of, 316-326.
Terranes, economic importance of, 331-332.
Impracticable boundaries, 417-418.
Indians, account of, 376-406.
Census of, 406.
Treatment of, by United States and Canada, 397-403.
Innuit, meaning of the term, 356.
Innuits, brief account of, 366-372.
Intrusive sheets, 320-321.
Iron Mountain, Mo., 92.
Iron ores, 342-344.
Iroquois, houses of, 387-388.
Irrigation practised by Indians, 386.
Irving, W., reference to, 395.
Islands, 30-31.
Isobars, 173.
Isotherms, 173.
Jackson, S., reference to, 269.
Jamaica, terraces on, 22.
James River, Va., submerged channel of, 42.
Japan current, reference to, 25.
Jeff Davis Peak, Nev., height of, 146.
Jefferson, Mt., Ore., height of, 156.
Johnson, W. D., cited, 109.
Judas-tree, 233.
Kamlayka, 370.
Kara Sea, life in, 14.
Katahdin, Mt., Me., height of, 85.
Kayaks, 370-371.
Kittatinny peneplain, 80.
Knowlton, F. H., cited, 312.
Kowak River, Alaska, ice near, 68.
Labrador, boundary of, 418.
Topography of, 71-72.
Laccoliths, 131, 321.
Lake plains, brief account of, 99-101.
Lakes, enclosed, 141.
Languages, 359-360.
Language spoken in America, 421.
Laurentian Highlands, brief account of, 87-88.
Lakes, 99.
Leidy, J., cited, 313-314.
Lesquereux, L., cited, 312.
Life on the continental shelf, 10-16.
Realms, 259-260.
Regions and life-zones, 260-262.
Limestones, 334-335.
Little Bahama Bank, brief account of, 18.
Llano Estacado, El, 106-109.
Lodge of Blackfoot Indians, 387.
Logan, Mt., Yukon, height of, 166.
Longhouse of Iroquois, 387-388.
Lookout Mountain, Tenn., section through, 78.
Lost mountains, 143.
Lower Austral climatic province, 191-194.
Luigi, Prince, ascent of Mt. St.
Elias, 166.
_Lutra canadensis_, 278.
Mackenzie River, delta of, 52.
McKinley, Mt., Alaska, height of, 166.
Magnolia, 230.
Maine, map of coast of, 45.
Mammalian families peculiar to America, 287-288.
Mammals, classification of, 262-264.
Mansfield, Mt., N. H., height of, 83.
Marcy, Mt., N. Y., height of, 84.
Marl, 335.
Marsh, O. C., cited, 312, 313, 314.
Massachusetts, boundary of, 418.
Mauvaises terres, 110.
Maya houses, 392.
Mayas, culture of, 364.
Mazama, Mt., Ore., 153-155.
Height of, 156.
_Mazama_, 273-275.
Mazamas, the, 273.
_Mephitis mephitica_, 280.
Merriam, C. H., cited, 185, 259, 260.
Merrimac River, boundary near, 418.
Metamorphic rocks, 323-324.
Terranes, economic importance of, 347-353.
Metamorphism, nature of, 324.
Mexico, area and population of, 424.
Boundary of, 418.
Indians of, 403.
Mica, 350.
Migration of birds, 292-296.
Miquelon, retained by France, 419.
Mississippi Delta, map of, 53.
River, delta of, 53-55.
Mobile Bay, 36.
Monadnock, definition of, 70.
Moose, brief account of, 269-270.
Morgan, L. H., cited, 388, 395.
Mountain boundaries, 413-414.
Sheep, brief account of, 272-273.
Goat, 273-275.
Muir, John, cited, 151, 244.
Musk-ox, 265-266.
Navidad Bank, reference to, 18.
Neogæic life realm, 259.
Neolithic, 364.
Newark system, 320.
Newberry, J. S., cited, 312.
New Brunswick, mountains of, 84.
Newcastle, Del., boundary in reference to, 416.
New England, mountains of, 82-83.
Newfoundland, area and population of, 424.
Continental shelf bordering, 2.
French rights in, 419.
Jurisdiction over Labrador, 417.
New Hampshire, boundary of, 418.
New Jersey, boundary of, 411-412.
Subsidence of coast of, 63.
New York, boundary of, 411-412.
Mountains of, 83.
Nicaragua, area and population of, 424.
Nordenskiöld cited, 15.
Notogæic life realm, 259.
Notre Dame Mountains, 84.
Olympic Mountains, Wash., 165.
Onyx marble, 335.
Oomiak, 370.
Ores, deposition of, 345.
Origin of the aborigines, 356-357.
Otter, 278.
Ouachita Mountains, 93.
Ozark Uplift, description of, 91-94.
Pacific forest, 238-249.
Mountains, 60, 120-136.
Paleolithic, 364.
Palms, 220-224.
Panama, area and population of, 424.
Park Mountains, 127-130.
Parkies, 370.
Peneplain, definition of, 69-70.
Pennsylvania, boundary of, 416.
Perry, W. A., cited, 270.
Petroleum, 338-340.
Physiographic divisions, map of, 61.
Piedmont plateau, 64, 69-70.
Pines, 232-233, 247-249.
Pitt, Mt., Ore., height of, 156.
Planetary winds, 178-179.
Plant life, 215-257.
Plateaus, treeless, 252-253.
Platinum, 352.
Playas, characteristics of, 253.
Examples of, 141.
Description of, 121.
Plutonic plug, 321.
Point Barrow, Alaska, life in the sea near, 14.
Tides at, 30.
Polar bear, 266.
Political control, 419-424.
Geography, 408-426.
Population of North America, 424.
Porto Rico, area and population of, 424.
Possessions held by European governments, 424.
Potomac River, submerged channel of, 43.
Pourtales, L. F., work of in Caribbean region, 16.
Powell, J. W., cited, 90, 104, 124, 127, 251, 357, 359.
Prairies, brief account of, 250, 253.
Prairie plains, brief account of, 95-99.
Prescott, W. H., reference to, 395.
_Pteranodon_, 313.
Pueblo Indians, 390.
Pueblos, 388.
Puget Sound basin, 158-161.
Origin of, 47.
Map of, 161.
Pyramid Lake, Nev., 140.
Rainier, Mt., Wash., photograph of, 156.
Height of, 156.
Raton Mesa, N. M., 120.
Redwood forests of California, 242-246.
Reindeer in Alaska, 269.
Reptiles of the Mesozoic, 313.
Republics, American, 420.
Resources used by Indians, 379-387.
River deltas, 52-55.
Rocky Mountains, brief account of, 122-136.
Of Canada, 124.
Rogers, H. D., cited, 312.
Russian-American Company, 375.
Houses, 369.
St. Elias, Mt., Alaska, height of, 166.
Elevation of coast near, 46.
Not a volcano, 167.
St. François Mountains, Mo., height of, 92.
St. Helens, Mt., Wash., height of, 156.
St. John, N. B., tides at, 30.
St. Lawrence estuary, 55-56.
River, submerged channel of, 9.
St. Pierre, retained by France, 419.
Salt, 341-342.
Salvador, area and population of, 424.
San Clemente Island, Cal., 10.
San Domingo, area and population of, 424.
San Francisco Bay, Cal., origin of, 49.
San Juan Islands, Wash., 413.
San Louis Park, Col., 128.
Sand-hills, 112-113.
Sandstone, 332-333.
Santa Catalina Island, Cal., 10.
Santa Cruz Island, Cal., 10.
Santa Domingo, area and population of, 424.
Santa Rosa Island, Cal., 10.
Sargent, C. S., cited, 249.
Schaffner, D. C., maps compiled by, 301.
Schooley peneplain, 80-81.
Schools for Indians, 401-402.
Sclater, P. L., cited, 259.
Scott, Mt., Ore., height of, 156.
Seasons, 179-182.
Section through Black Hills of Dakota, 117.
Lookout Mountain, Tenn., 78.
Sedimentary rocks, brief account of, 306-316.
Terranes, economic importance of, 331-346.
_Sequoia gigantea_, 242, 244-246.
_Sempervirens_, 242-244.
Shenandoah peneplain, 81.
Sierra Blanca, N. M., 129.
Sierran epoch, mention of, 315.
Sierra Nevada Mountains, Cal., brief account of, 147-158.
Sigsbee Deep, 20.
Silver, 346.
Pine, 248.
Six Nations of New York, 405.
Skunk, brief account of, 280-282.
Solóvioff, I. M., reference to, 374.
Spain, former possessions of, 419.
_Sphagnum_, 67.
Spring-time music, 296-298.
Stony Mountains, 124-127.
Stream deposits, changes in coast-lines due to, 51-55.
Subarctic forest plains, 101-102.
Submerged river channels, 8-10.
Subsequent drainage, example of, 118.
Subsidences of coasts, 62-63.
Subtuberant mountains, 322.
Sugar-pine, 247.
Superimposed drainage, example of, 118.
Susquehanna River, submerged channel of, 43.
Sutton, Mt., N. B., height of, 84.
Synclinal mountains, 78.
Tahoe Lake, Cal.--Nev., 140.
Talc, 350.
Tarr, R. S., map of co-tidal lines by, 28.
Tepee of Indians, 387, 388.
Terraces on islands of California coast, 10.
Sea, 33-34.
Thomas, C, cited, 395.
Thunder-storms, 206-207.
Tides, 27-30.
in rivers, 44.
Timber-line, 254.
Tlingit Indians, 397.
Topography of coasts, 31-55.
Tornadoes, 207.
Transition climatic province, 197-201.
Treaty of Ghent, reference to, 418.
Treeless mountain tops, 254-257.
Plains, brief account of, 250-253.
Tropical climatic province, 186-191.
Forests, 219-227.
Tundra, brief account of, 67-68.
Turner, H. W., cited, 148.
Tyrrell, J. B., cited, 66, 268.
Union, Mt., Ore., height of, 156.
United Kingdom, possessions of, 424.
United States, area and population of, 424.
Boundaries of, 417-418.
Treatment of Indians by, 399-403.
Coast and Geodetic Survey, reference to work of, 16.
Fish Commission, reference to work of, 16.
Upper Austral climatic province, 194-197.
Uxmal, Yucatan, panorama of, 390.
Vancouver, B. C., firs of, 241.
Mountains, B. C., 165.
Van Hise, C. R., cited, 310.
"Vega," voyage of, 15.
Veniaminoff, reference to, 375.
Virginia creeper, 234.
Volcanic mountains, 120-121.
Volcanoes, 317-318.
Wallace, A. R., cited, 30, 259.
Wapiti, brief account of, 270-271.
Ward, L. F., cited, 312.
Washington, Mt., N. H., height of, 83.
Water boundaries, 411-413.
Mineral, 353.
West Indian hurricanes, 210.
West Indies, Danish, area and population of, 424.
French, area and population of, 424.
Indians of, 404.
Political division of, 422-423.
Whirlwinds, 203.
White, D., cited, 312.
White, I. C., cited, 312.
White, Mt., Nev., height of, 146.
White Mountains, N. H., forests of, 86.
Whiteface, Mt., N. Y., height of, 84.
Whitney, J. D., cited, 251.
Whitney, Mt., Cal., height of, 149.
Willis, Bailey, cited, 79.
Winds, planetary, 178-179.
Winnemucca Lake, Nev., 140.
Wolves, brief account of, 285-287.
Yellow pine, 248.
Yosemite Valley, Cal., 150.
Yucatan, continental shelf bordering, 2.
Topography of, 19.
Yukon River, delta of, 52.
Zuñi, 389.
THE END
* * * * *
List Of Corrections
Transcriber's Note: Blank pages have been deleted. Some illustrations have
been moved. We have rendered consistent on a per-word-pair basis the
hyphenation or spacing of such pairs when repeated in the same grammatical
context. Detected publisher's errors were corrected as listed below:
Page Correction
5 both calcareous and silicious[siliceous]
12 Carribbean[Caribbean]
18 Gulf of Mexico and the Carribean[Caribbean] region:
60 Taking the better-known[better known] portions of North America
72 and are hard and resistent[resistant]
103 "Land oh[ho]!" is no more thrilling
105 where preciptation[precipitation] is abundant
126 Bamf[Banff], Lake Louise, Glacier House,
131 related to this phase of volcanism[vulcanism] is the
139 in Nevada and southestern[southeastern] California
150 hard rocks thus exposed [were] rounded
176 to take a more criticial[critical] view
179 wind blows with remarkable unformity[uniformity]
203 are cultivated with moderate successs[success].
263 the terra calente[caliente] of Mexico
271 from civilization is[are] great
281 skunks belong to the family Mustalidæ[Mustelidæ]
290 and the pecular[peculiar] hoazin, represented
363 the plating[plaiting] of baskets and the art
430 Sub-soil[Subsoil], in Alaska, 68.
431 Mephities[Mephitis] mephitica, 280.
431 Micquelon[Miquelon], retained by France, 419.
433 St. Francois[François] Mountains, Mo., height of,
433 Solóvieff[Solóvioff], I. M., reference to, 374
433 St. Helena[Helens], Mt., Wash., height of, 156.
434 Wapati[Wapiti], brief account of, 270-271.
* * * * *
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