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Title: Theory of the Earth, Volume 1 (of 4)
Author: James Hutton
Release Date: July 9, 2004 [eBook #12861]
Language: English
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THEORY OF THE EARTH, VOLUME I
With Proofs and Illustrations, in Four Parts
By
JAMES HUTTON, M.D. & F.R.S.E.
1795.
CONTENTS.
PART I.
THEORY OF THE EARTH; with the Examination of different Opinions on
that Subject.
CHAP. I.
THEORY OF THE EARTH; or an Investigation of the Laws observable in the
Composition, Dissolution, and Restoration of Land upon the Globe.
SECT. I.--Prospect of the Subject to be treated of.
SECT. II.--An Investigation of the Natural Operations employed in
consolidating the Strata of the Globe.
SECT. III.--Investigation of the Natural Operations employed in the
Production of Land above the Surface of the Sea.
SECT. IV.--System of Decay and Renovation observed in the Earth.
CHAP. II.
An Examination of Mr KIRWAN's Objections to the Igneous Origin of Stony
Substances.
CHAP. III.
Of Physical Systems, and Geological Theories, in general.
CHAP. IV.
The Supposition of Primitive Mountains refuted.
CHAP. V.
Concerning that which may be termed the Primary Part of the Present
Earth.
CHAP. VI.
The Theory of interchanging Sea and Land, illustrated by an
Investigation of the Primary and Secondary Strata 421.
SECT. I.--A distinct view of the Primary and Secondary Strata.
SECT. II.--The Theory confirmed from Observations made on purpose to
elucidate the Subject.
CHAP. VII.
Opinions examined with regard to Petrifaction, or Mineral Concretion.
CHAP. VIII.
The Nature of Mineral Coal, and the Formation of Bituminous Strata,
investigated.
SECT. I.--Purpose of this Inquiry.
SECT. II.--Natural History of Coal Strata, and Theory of this
Geological Operation.
SECT. III.--The Mineralogical Operations of the Earth illustrated from
the Theory of Fossil Coal.
PART I.
THEORY OF THE EARTH;
WITH THE
EXAMINATION
OF
DIFFERENT OPINIONS ON THAT SUBJECT.
IN EIGHT CHAPTERS.
CHAPTER I.
THEORY of the EARTH; or an Investigation of the Laws observable in the
Composition, Dissolution, and Restoration, of Land upon the Globe.
SECTION I.
Prospect of the Subject to be treated of.
When we trace the parts of which this terrestrial system is composed,
and when we view the general connection of those several parts, the
whole presents a machine of a peculiar construction by which it is
adapted to a certain end. We perceive a fabric, erected in wisdom, to
obtain a purpose worthy of the power that is apparent in the production
of it.
We know little of the earth's internal parts, or of the materials which
compose it at any considerable depth below the surface. But upon the
surface of this globe, the more inert matter is replenished with plants,
and with animal and intellectual beings.
Where so many living creatures are to ply their respective powers, in
pursuing the end for which they were intended, we are not to look for
nature in a quiescent state; matter itself must be in motion, and the
scenes of life a continued or repeated series of agitations and events.
This globe of the earth is a habitable world; and on its fitness for
this purpose, our sense of wisdom in its formation must depend. To judge
of this point, we must keep in view, not only the end, but the means
also by which that end is obtained. These are, the form of the whole,
the materials of which it is composed, and the several powers which
concur, counteract, or balance one another, in procuring the general
result.
The form and constitution of the mass are not more evidently calculated
for the purpose of this earth as a habitable world, than are the various
substances of which that complicated body is composed. Soft and hard
parts variously combine to form a medium consistence, adapted to the use
of plants and animals; wet and dry are properly mixed for nutrition,
or the support of those growing bodies; and hot and cold produce a
temperature or climate no less required than a soil: Insomuch, that
there is not any particular, respecting either the qualities of the
materials, or the construction of the machine, more obvious to
our perception, than are the presence and efficacy of design and
intelligence in the power that conducts the work.
In taking this view of things, where ends and means are made the object
of attention, we may hope to find a principle upon which the comparative
importance of parts in the system of nature may be estimated, and also
a rule for selecting the object of our inquiries. Under this direction,
science may find a fit subject of investigation in every particular,
whether of _form_, _quality_, or _active power_, that presents itself in
this system of motion and of life; and which, without a proper
attention to this character of the system, might appear anomalous and
incomprehensible.
It is not only by seeing those general operations of the globe which
depend upon its peculiar construction as a machine, but also by
perceiving how far the particulars, in the construction of that machine,
depend upon the general operations of the globe, that we are enabled to
understand the constitution of this earth as a thing formed by design.
We shall thus also be led to acknowledge an order, not unworthy of
Divine wisdom, in a subject which, in another view, has appeared as the
work of chance, or as absolute disorder and confusion.
To acquire a general or comprehensive view of this mechanism of the
globe, by which it is adapted to the purpose of being a habitable world,
it is necessary to distinguish three different bodies which compose the
whole. These are, a solid body of earth, an aqueous body of sea, and an
elastic fluid of air.
It is the proper shape and disposition of these three bodies that form
this globe into a habitable world; and it is the manner in which these
constituent bodies are adjusted to each other, and the laws of action
by which they are maintained in their proper qualities and respective
departments, that form the Theory of the machine which we are now to
examine.
Let us begin with some general sketch of the particulars now mentioned.
_1st_, There is a central body in the globe. This body supports those
parts which come to be more immediately exposed to our view, or which
may be examined by our sense and observation. This first part is
commonly supposed to be solid and inert; but such a conclusion is only
mere conjecture; and we shall afterwards find occasion, perhaps, to form
another judgment in relation to this subject, after we have examined
strictly, upon scientific principles, what appears upon the surface, and
have formed conclusions concerning that which must have been transacted
in some more central part.
_2dly_, We find a fluid body of water. This, by gravitation, is reduced
to a spherical form, and by the centrifugal force of the earth's
rotation, is become oblate. The purpose of this fluid body is essential
in the constitution of the world; for, besides affording the means of
life and motion to a multifarious race of animals, it is the source of
growth and circulation to the organized bodies of this earth, in being
the receptacle of the rivers, and the fountain of our vapours.
_3dly_, We have an irregular body of land raised above the level of the
ocean. This, no doubt, is the smallest portion of the globe; but it is
the part to us by far most interesting. It is upon the surface of this
part that plants are made to grow; consequently, it is by virtue of
this land that animal life, as well as vegetation, is sustained in this
world.
_Lastly_, We have a surrounding body of atmosphere, which completes the
globe. This vital fluid is no less necessary, in the constitution of the
world, than are the other parts; for there is hardly an operation upon
the surface of the earth, that is not conducted or promoted by its
means. It is a necessary condition for the sustenance of fire; it is the
breath of life to animals; it is at least an instrument in vegetation;
and, while it contributes to give fertility and health to things that
grow, it is employed in preventing noxious effects from such as go into
corruption. In short, it is the proper means of circulation for the
matter of this world, by raising up the water of the ocean, and pouring
it forth upon the surface of the earth.
Such is the mechanism of the globe: Let us now mention some of those
powers by which motion is produced, and activity procured to the mere
machine.
First, There is the progressive force, or moving power, by which this
planetary body, if solely actuated, would depart continually from the
path which it now pursues, and thus be for ever removed from its end,
whether as a planetary body, or as a globe sustaining plants and
animals, which may be termed a living world.
But this moving body is also actuated by gravitation, which inclines
it directly to the central body of the sun. Thus it is made to revolve
about that luminary, and to preserve its path.
It is also upon the same principles, that each particular part upon the
surface of this globe, is alternately exposed to the influence of light
and darkness, in the diurnal rotation of the earth, as well as in its
annual revolution. In this manner are produced the vicissitudes of night
and day, so variable in the different latitudes from the equator to the
pole, and so beautifully calculated to equalise the benefits of light,
so variously distributed in the different regions of the globe.
Gravitation, and the _vis infita_ of matter, thus form the first two
powers distinguishable in the operations of our system, and wisely
adapted to the purpose for which they are employed.
We next observe the influence of light and heat, of cold and
condensation. It is by means of these two powers that the various
operations of this living world are more immediately transacted;
although the other powers are no less required, in order to produce or
modify these great agents in the economy of life, and system of our
changing things.
We do not now inquire into the nature of those powers, or investigate
the laws of light and heat, of cold and condemnation, by which the
various purposes of this world are accomplished; we are only to mention
those effects which are made sensible to the common understanding of
mankind, and which necessarily imply a power that is employed. Thus,
it is by the operation of those powers that the varieties of season
in spring and autumn are obtained, that we are blessed with the
vicissitudes of summer's heat and winter's cold, and that we possess the
benefit of artificial light and culinary fire.
We are thus bountifully provided with the necessaries of life; we are
supplied with things conducive to the growth and preservation of our
animal nature, and with fit subjects to employ and to nourish our
intellectual powers.
There are other actuating powers employed in the operations of this
globe, which we are little more than able to enumerate; such are those
of electricity, magnetism, and subterraneous heat or mineral fire.
Powers of such magnitude or force, are not to be supposed useless in a
machine contrived surely not without wisdom; but they are mentioned here
chiefly on account of their general effect; and it is sufficient to have
named powers, of which the actual existence is well known, but of which
the proper use in the constitution of the world is still obscure.
The laws of electricity and magnetism have been well examined by
philosophers; but the purposes of those powers in the economy of the
globe have not been discovered. Subterraneous fire, again, although the
most conspicuous in the operations of this world, and often examined by
philosophers, is a power which has been still less understood, whether
with regard to its efficient or final cause. It has hitherto appeared
more like the accident of natural things, than the inherent property of
the mineral region. It is in this last light, however, that I wish to
exhibit it, as a great power acting a material part in the operations of
the globe, and as an essential part in the constitution of this world.
We have thus surveyed the machine in general, with those moving powers,
by which its operations, diversified almost _ad infinitum_, are
performed. Let us now confine our view, more particularly, to that part
of the machine on which we dwell, that so we may consider the natural
consequences of those operations which, being within our view, we are
better qualified to examine.
This subject is important to the human race, to the possessor of this
world, to the intelligent being Man, who foresees events to come, and
who, in contemplating his future interest, is led to inquire concerning
causes, in order that he may judge of events which otherwise he could
not know.
If, in pursuing this object, we employ our skill in research, not in
forming vain conjectures; and if _data_ are to be found, on which
Science may form just conclusions, we should not long remain in
ignorance with respect to the natural history of this earth, a subject
on which hitherto opinion only, and not evidence, has decided: For in no
subject, perhaps, is there naturally less defect of evidence, although
philosophers, led by prejudice, or misguided by false theory, may have
neglected to employ that light by which they should have seen the system
of this world.
But to proceed in pursuing a little farther our general or preparatory
ideas. A solid body of land could not have answered the purpose of a
habitable world; for, a soil is necessary to the growth of plants; and a
soil is nothing but the materials collected from the destruction of the
solid land. Therefore, the surface of this land, inhabited by man,
and covered with plants and animals, is made by nature to decay, in
dissolving from that hard and, compact state in which it is found below
the soil; and this soil is necessarily washed away, by the continual
circulation of the water, running from the summits of the mountains
towards the general receptacle of that fluid. The heights of our land
are thus levelled with the shores; our fertile plains are formed from the
ruins of the mountains; and those travelling materials are still pursued
by the moving water, and propelled along the inclined surface of the
earth[1] These moveable materials, delivered into the sea, cannot, for
a long continuance, rest upon the shore; for, by the agitation of the
winds, the tides and currents, every moveable thing is carried
farther and farther along the shelving bottom of the sea, towards the
unfathomable regions of the ocean.
[Note 1: M. de Luc, in his second letter to me, published in the Monthly
Review for 1790, says, "You ought to have proved that both gravel and
sand are carried from our continents to the sea; which, on the contrary,
I shall prove not to be the case." He then endeavours to prove his
assertion, by observing, that, in certain places where there is not
either sufficient declivity in the surface, or force in the running
water, gravel and sand are made to rest, and do not travel to the sea.
This surely is a fact to which I most readily assent; but, on the other
hand, I hope he will acknowledge, that, where there is sufficient
declivity in the surface, or force in the running water, sand, gravel,
and stones, are travelled upon the land, and are thus carried into the
sea--at last. This is all that my theory requires, and this is what I
believe will be admitted, without any farther proof on my part.]
If the vegetable soil is thus constantly removed from the surface of the
land, and if its place is thus to be supplied from the dissolution of
the solid earth, as here represented, we may perceive an end to this
beautiful machine; an end, arising from no error in its constitution as
a world, but from that destructibility of its land which is so necessary
in the system of the globe, in the economy of life and vegetation.
The immense time necessarily required for this total destruction of
the land, must not be opposed to that view of future events, which is
indicated by the surest facts, and most approved principles. Time, which
measures every thing in our idea, and is often deficient to our schemes,
is to nature endless and as nothing; it cannot limit that by which alone
it had existence; and, as the natural course of time, which to us seems
infinite, cannot be bounded by any operation that may have an end, the
progress of things upon this globe, that is, the course of nature,
cannot be limited by time, which must proceed in a continual succession.
We are, therefore, to consider as inevitable the deduction of our land,
so far as effected by those operations which are necessary in the
purpose of the globe, considered as a habitable world; and, so far as
we have not examined any other part of the economy of nature, in which
other operations and a different intention might appear.
We have now considered the globe of this earth as a machine, constructed
upon chemical as well as mechanical principles, by which its different
parts are all adapted, in form, in quality, and in quantity, to a
certain end; an end attained with certainty or success; and an end from
which we may perceive wisdom, in contemplating the means employed.
But is this world to be considered thus merely as a machine, to last no
longer than its parts retain their present position, their proper forms
and qualities? Or may it not be also considered as an organized body?
such as has a constitution in which the necessary decay of the machine
is naturally repaired, in the exertion of those productive powers by
which it had been formed.
This is the view in which we are now to examine the globe; to see if
there be, in the constitution of this world, a reproductive operation,
by which a ruined constitution may be again repaired, and a duration or
stability thus procured to the machine, considered as a world sustaining
plants and animals.
If no such reproductive power, or reforming operation, after due
inquiry, is to be found in the constitution of this world, we should
have reason to conclude, that the system of this earth has either been
intentionally made imperfect, or has not been the work of infinite power
and wisdom.
Here is an important question, therefore, with regard to the
constitution of this globe; a question which, perhaps, it is in
the power of man's sagacity to resolve; and a question which, if
satisfactorily resolved, might add some lustre to science and the human
intellect.
Animated with this great, this interesting view, let us strictly examine
our principles, in order to avoid fallacy in our reasoning; and let us
endeavour to support our attention, in developing a subject that is
vast in its extent, as well as intricate in the relation of parts to be
stated.
The globe of this earth is evidently made for man. He alone, of all the
beings which have life upon this body, enjoys the whole and every part;
he alone is capable of knowing the nature of this world, which he thus
possesses in virtue of his proper right; and he alone can make the
knowledge of this system a source of pleasure, and the means of
happiness.
Man alone, of all the animated beings which enjoy the benefits of this
earth, employs the knowledge which he there receives, in leading him to
judge of the intention of things, as well as of the means by which they
are brought about; and he alone is thus made to enjoy, in contemplation
as well as sensual pleasure, all the good that may be observed in the
constitution of this world; he, therefore, should be made the first
subject of inquiry.
Now, if we are to take the written history of man for the rule by which
we should judge of the time when the species first began, that period
would be but little removed from the present state of things. The Mosaic
history places this beginning of man at no great distance; and there
has not been found, in natural history, any document by which a high
antiquity might be attributed to the human race. But this is not the
case with regard to the inferior species of animals, particularly those
which inhabit the ocean and its shores. We find, in natural history,
monuments which prove that those animals had long existed; and we thus
procure a measure for the computation of a period of time extremely
remote, though far from being precisely ascertained.
In examining things present, we have data from which to reason with
regard to what has been; and, from what has actually been, we have
data for concluding with regard to that which is to happen hereafter.
Therefore, upon the supposition that the operations of nature are
equable and steady, we find, in natural appearances, means for
concluding a certain portion of time to have necessarily elapsed, in the
production of those events of which we see the effects.
It is thus that, in finding the relics of sea-animals of every kind
in the solid body of our earth, a natural history of those animals
is formed, which includes a certain portion of time; and, for the
ascertaining this portion of time, we must again have recourse to the
regular operations of this world. We shall thus arrive at facts which
indicate a period to which no other species of chronology is able to
remount.
In what follows, therefore, we are to examine the construction of the
present earth, in order to understand the natural operations of time
past; to acquire principles, by which we may conclude with regard to the
future course of things, or judge of those operations, by which a world,
so wisely ordered, goes into decay; and to learn, by what means such a
decayed world may be renovated, or the waste of habitable land upon the
globe repaired.
This, therefore, is the object which we are to have in view during this
physical investigation; this is the end to which are to be directed all
the steps in our cosmological pursuit.
The solid parts of the globe are, in general, composed of sand, of
gravel, of argillaceous and calcareous strata, or of the various
compositions of these with some other substances, which it is not
necessary now to mention. Sand is separated and sized by streams and
currents; gravel is formed by the mutual attrition of stones agitated
in water; and marly, or argillaceous strata, have been collected, by
subsiding in water with which those earthy substances had been floated.
Thus, so far as the earth is formed of these materials, that solid body
would appear to have been the production of water, winds, and tides.
But that which renders the original of our land clear and evident,
is the immense quantities of calcareous bodies which had belonged
to animals, and the intimate connection of these masses of animal
production with the other strata of the land. For it is to be proved,
that all these calcareous bodies, from the collection of which the
strata were formed, have belonged to the sea, and were produced in it.
We find the marks of marine animals in the most solid parts of the
earth; consequently, those solid parts have been formed after the ocean
was inhabited by those animals which are proper to that fluid medium.
If, therefore, we knew the natural history of those solid parts, and
could trace the operations of the globe, by which they had been formed,
we would have some means for computing the time through which those
species of animals have continued to live. But how shall we describe a
process which nobody has seen performed, and of which no written
history gives any account? This is only to be investigated, _first_, in
examining the nature of those solid bodies, the history of which we want
to know; and, 2_dly_, In examining the natural operations of the globe,
in order to see if there now actually exist such operations, as, from
the nature of the solid bodies, appear to have been necessary to their
formation.
But, before entering more particularly into those points of discussion,
by which the question is to be resolved, let us take a general view of
the subject, in order to see what it is which science and observation
must decide.
In all the regions of the globe, immense masses are found, which, though
at present in the most solid state, appear to have been formed by the
collection of the calcareous _exuviae_ of marine animals. The question
at present is not, in what manner those collections of calcareous relics
have become a perfect solid body, and have been changed from an animal
to a mineral substance; for this is a subject that will be afterwards
considered; we are now only inquiring, if such is truly the origin of
those mineral masses.
That all the masses of marble or limestone are composed of the
calcareous matter of marine bodies, may be concluded from the following
facts:
1_st_, There are few beds of marble or limestone, in which may not be
found some of those objects which indicate the marine origin of the
mass. If, for example, in a mass of marble, taken from a quarry upon the
top of the Alps or Andes[2], there shall be found one cockle-shell, or
piece of coral, it must be concluded, that this bed of stone had been
originally formed at the bottom of the sea, as much as another bed which
is evidently composed almost altogether of cockle-shells and coral. If
one bed of limestone is thus found to have been of a marine origin,
every concomitant bed of the same kind must be also concluded to have
been formed in the same Manner.
[Note 2: "Cette sommité élevée de 984 toises au dessus de notre lac, et
par conséquent de 1172 au dessus de la mer, est remarquable en ce que
l'on y voit des fragmens d'huîtres pétrifiés.--Cette montagne est
dominée par un rocher escarpé, qui s'il n'est pas inaccessible, est du
moins d'un bien difficile accès; il paroît presqu'entièrement composé
de coquillages pétrifiés, renfermés dans un roc calcaire, ou marbre
grossier noirâtre. Les fragmens qui s'en détachent, et que l'on
rencontre en montant à la Croix de fer, sont remplis de _turbinites_ de
différentes espèces." M. DE SAUSSURE, _Voyage dans les Alpes_, p. 394.]
We thus shall find the greatest part of the calcareous masses upon this
globe to have originated from marine calcareous bodies; for whether
we examine marbles, limestones, or such solid masses as are perfectly
changed from the state of earth, and are become compact and hard, or
whether we examine the soft, earthy, chalky or marly strata, of which so
much of this earth is composed, we still find evident proofs, that those
beds had their origin from materials deposited at the bottom of the sea;
and that they have the calcareous substance which they contain, from the
same source as the marbles or the limestones.
2_dly_, In those calcareous strata, which are evidently of marine
origin, there are many parts that are of a sparry structure, that is
to say, the original texture of those beds, in such places, has been
dissolved, and a new structure has been assumed, which is peculiar to
a certain state of the calcareous earth. This change is produced by
crystallisation, in consequence of a previous state of fluidity, which
has so disposed the concreting parts, as to allow them to assume a
regular shape and structure proper to that substance. A body, whose
external form has been modified by this process, is called a _crystal_;
one whose internal arrangement of parts is determined by it, is said to
be of a _sparry structure_; and this is known from its fracture.
3_dly_, There are, in all the regions of the earth, huge masses of
calcareous matter, in that crystalline form of sparry state, in
which perhaps no vestige can be found of any organised body, nor any
indication that such calcareous matter had belonged to animals; but
as, in other masses, this sparry structure, or crystalline state, is
evidently assumed by the marine calcareous substances, in operations
which are natural to the globe, and which are necessary to the
consolidation of the strata, it does not appear, that the sparry masses,
in which no figured body is formed, have been originally different from
other masses, which, being only crystallised in part, and in part still
retaining their original form, leave ample evidence of their marine
origin[3].
[Note 3: M. de Saussure, describing the marble of Aigle, says, "Les
tables polies de ce marbre présentent fréquemment des coquillages, dont
la plupart sont des peignes striés, et de très-beaux madrépores. Tous
ces corps marins on pris entierement la nature et le grain même
du marbre, on n'y voit presque jamais la coquille sous sa forme
originaire."]
We are led, in this manner, to conclude, that all the strata of the
earth, not only those consisting of such calcareous masses, but others
superincumbent upon these, have had their origin at the bottom of the
sea, by the collection of sand and gravel, of shells, of coralline
and crustaceous bodies, and of earths and clays, variously mixed,
or separated and accumulated. Here is a general conclusion, well
authenticated in the appearances of nature, and highly important in the
natural history of the earth.
The general amount of our reasoning is this, that nine-tenths, perhaps,
or ninety-nine hundredths of this earth, so far as we see, have
been formed by natural operations of the globe, in collecting loose
materials, and depositing them at the bottom of the sea; consolidating
those collections in various degrees, and either elevating those
consolidated masses above the level on which they were formed, or
lowering the level of that sea.
There is a part of the solid earth which we may at present neglect, not
as being persuaded that this part may not also be found to come under
the general rule of formation with the rest, but as considering this
part to be of no consequence in forming a general rule, which shall
comprehend almost the whole, without doing it absolutely. This excluded
part consists of certain mountains and masses of granite. These are
thought to be still older in their formation, and are said never to
be found superincumbent on strata which must be acknowledged as the
productions of the sea.
Having thus found the greater part, if not the whole, of the solid land
to have been originally composed at the bottom of the sea, we may now,
in order to form a proper idea of these operations, suppose the whole of
this seaborn land to be again dispersed along the bottom of the ocean,
the surface of which would rise proportionally over the globe. We would
thus have a spheroid of water, with granite rocks and islands scattered
here and there. But this would not be the world which we inhabit;
therefore, the question now is, how such continents, as we actually have
upon the globe, could be erected above the level of the sea.
It must be evident, that no motion of the sea, caused by this earth
revolving in the solar system, could bring about that end; for let us
suppose the axis of the earth to be changed from the present poles, and
placed in the equinoctial line, the consequence of this might, indeed,
be the formation of a continent of land about each new pole, from whence
the sea would run towards the new equator; but all the rest of the globe
would remain an ocean. Some new points might be discovered, and others,
which before appeared above the surface of the sea, would be sunk by
the rising of the water; but, on the whole, land could only be gained
substantially at the poles. Such a supposition, as this, if applied to
the present state of things, would be destitute of every support, as
being incapable of explaining what appears.
But even allowing that, by the changed axis of the earth, or any other
operation of the globe, as a planetary body revolving in the solar
system, great continents of land could have been erected from the place
of their formation, the bottom of the sea, and placed in a higher
elevation, compared with the surface of that water, yet such a continent
as this could not have continued stationary for many thousand years; nor
could a continent of this kind have presented to us, every where within
its body, masses of consolidated marble, and other mineral substances,
in a state as different as possible from that in which they were, when
originally collected together in the sea.
Consequently, besides an operation, by which the earth at the bottom of
the sea should be converted into an elevated land, or placed high above
the level of the ocean, there is required, in the operations of the
globe, a consolidating power, by which the loose materials that had
subsided from water, should be formed into masses of the most perfect
solidity, having neither water nor vacuity between their various
constituent parts, nor in the pores of those constituent parts
themselves.
Here is an operation of the globe, whether chemical or mechanical, which
is necessarily connected with the formation of our present continents:
Therefore, had we a proper understanding of this secret operation, we
might thereby be enabled to form an opinion, with regard to the nature
of that unknown power, by which the continents have been placed above
the surface of that water wherein they had their birth.
If this consolidating operation be performed at the bottom of the
ocean, or under great depths of the earth, of which our continents are
composed, we cannot be witnesses to this mineral process, or acquire the
knowledge of natural causes, by immediately observing the changes which
they produce; but though we have not this immediate observation of those
changes of bodies, we have, in science, the means of reasoning from
distant events; consequently, of discovering, in the general powers of
nature, causes for those events of which we see the effects.
That the consolidating operation, in general, lies out of the reach of
our immediate observation, will appear from the following truth: All the
consolidated masses, of which we now inquire into the cause, are, upon
the surface of the earth, in a state of general decay, although the
various natures of those bodies admit of that dissolution in very
different degrees[4]
From every view of the subject, therefore, we are directed to look into
those consolidated masses themselves, in order to find principles from
whence to judge of those operations by which they had attained their
hardness or consolidated state.
It must be evident, that nothing but the most general acquaintance with
the laws of acting substances, and with those of bodies changing by the
powers of nature, can enable us to set about this undertaking with any
reasonable prospect of success; and here the science of Chemistry must
be brought particularly to our aid; for this science, having for its
object the changes produced upon the sensible qualities, as they are
called, of bodies, by its means we may be enabled to judge of that which
is possible according to the laws of nature, and of that which, in like
manner, we must consider as impossible.
[Note 4: Stalactical and certain ferruginous concretions may seem
to form an exception to the generality of this proposition. But an
objection of this kind could only arise from a partial view of things;
for the concretion here is only temporary; it is in consequence of a
solution, and it is to be followed by a dissolution, which will be
treated of in its proper place.]
Whatever conclusions, therefore, by means of this science, shall be
attained, in just reasoning from natural appearances, this must be held
as evidence, where more immediate proof cannot be obtained; and, in
a physical subject, where things actual are concerned, and not the
imaginations of the human mind, this proof will be considered as
amounting to a demonstration.
SECTION II.
An Investigation of the Natural Operations employed in consolidating
the Strata of the Globe.
We are now about to investigate those mineral operations of the globe by
which the qualities of hardness and solidity, consequently of strength
and durability, are procured to great bodies of this earth.
That those qualities are not original to such bodies, but actually
superinduced in the natural operations of the earth, will appear from
the examination of some of the hardest and most solid of those mineral
bodies. In such masses, (for example of flint and agate,) we find
included shells and coralline bodies. Consequently, there must be a
natural operation in the globe for consolidating and hardening its soft
and loose materials. It is concerning the nature of this consolidating
operation that we are now to inquire.
There are just two ways in which porous or spongy bodies can be
consolidated, and by which substances may be formed into masses of
a natural shape and regular structure; the one of these is simple
_congelation_ from a fluid state, by means of cold; the other is
_accretion_; and this includes a separatory operation, as well as that
by which the solid body is to be produced. But in whichever of these
ways solidity shall be procured, it must be brought about by first
inducing fluidity, either immediately by the action of heat, or
mediately with the assistance of a solvent, that is, by the operation
of solution. Therefore, fire and water may be considered as the general
agents in this operation, which we would explore.
Heat has been already mentioned as a general power, and as acting in all
the different parts of the globe; I would now wish more particularly to
call the attention of the reader to subterraneous fire, or heat, as
a powerful agent in the mineral regions, and as a cause necessarily
belonging to the internal constitution of this earth.
It is not our purpose at present to inquire into the particular nature
of this power of subterraneous heat, or to trace the proper connection
and analogy of the internal fire with that which is so necessary to our
life, and which acts so great a part upon the surface of the earth, this
being reserved for the last part. Our intention in here mentioning it,
is only to dispose the mind to look for active powers or efficient
causes, in that part of the earth which has been commonly considered as
passive and inert, but which will be found extremely active, and the
source of mighty revolutions in the fate of land.
There may, indeed, be some difficulty in conceiving all the
modifications of this mineral power; but as, on the one hand, we are not
arbitrarily to assume an agent, for the purpose of explaining events, or
certain appearances which are not understood; so, on the other, we must
not refuse to admit the action of a known power, when this is properly
suggested in the appearances of things; and, though we may not
understand all the modifications, or the whole capacity and regulation
of this power in bodies, we are not to neglect the appropriating to it,
as a cause, those effects which are natural to it, and which, so far as
we know, cannot belong to any other. On all occasions, we are to judge
from what we know; and, we are only to avoid concluding from our
suppositions, in cases where evidence or real information is necessarily
required. The subject now considered, subterraneous fire, will afford an
example of that truth; and, a general view of this great natural power
will here find a proper place, before the application of it for the
explanation of natural appearances.
No event is more the object of our notice, or more interesting as a
subject for our study, than is the burning of a fire: But, the more that
philosophers have studied this subject, the more they seem to differ
as to the manner in which that conspicuous event is to be explained.
Therefore, being so ignorant with regard to that fire of which we see
the origin as well as the more immediate effects, how cautious should
we be in judging the nature of subterraneous fire from the burning of
bodies, a subject which we so little understand.
But, though the cause of fire in general, or the operations of that
power in its extreme degrees, be for us a subject involved in much
obscurity, this is not the case with regard to the more common effects
of heat; and, tho' the actual existence of subterraneous fire, as the
cause of light and heat, might be a thing altogether problematical in
our opinion; yet, as to other effects, there are some of these from
which the action of that liquefying power may be certainly concluded as
having taken place within the mineral region, although the cause should
be in every other respect a thing to us unknown. In that case, where the
operation or effect is evident, and cannot be disputed, to refuse to
admit the power in question, merely because we had not seen it act, or
because we know not every rule which it may observe in acting, would
be only to found an argument upon our ignorance; it would be to
misunderstand the nature of investigating physical truths, which must
proceed by reasoning from effect to cause.
Our knowledge is extremely limited with regard to the effects of heat in
bodies, while acting under different conditions, and in various degrees.
But though our knowledge in these respects is limited, our judgment with
regard to the efficacy of this power of heat is in its nature positive,
and contains not any thing that is doubtful or uncertain. All mankind,
who have the opportunity, know that the hard substance of ice is by heat
converted into water, wherein no hardness remains; and the profound
philosophy of Dr Black, in relation to the subject of _latent heat_, as
that of Sir Isaac Newton, in relation to the weight of bodies, is not
necessary to convince the world that in the one case ice will melt, and
in the other, that heavy bodies will move when unsupported.
But though, in the abstract doctrine of _latent heat_, the ingenuity
of man has discovered a certain measure for the quantity of those
commutable effects which are perceived; and though this be a progress of
science far above the apprehension of the vulgar, yet still, that solid
bodies are changed into fluids, by the power of heat, is the same
unalterable judgment, which the savage forms as well as the philosopher.
Here, therefore, are evident effects, which mankind in general attribute
to the power of heat; and it is from those known effects that we are to
investigate subterraneous fire, or to generalise the power of heat, as
acting in the interior parts, as well as on the surface of this earth.
If, indeed, there were any other cause for fluidity besides the
operation of fire or the power of heat, in that case the most evident
proof, with regard to the flowing, or former fluidity, of mineral
bodies, would draw to no conclusion in proving the existence of mineral
fire; but when we have not the smallest reason for conjecturing any
other cause, or the least doubt with regard to that which, in the
doctrine of latent heat, has been properly investigated, the proofs
which we shall bring, of fusion in all the minerals of this earth,
must be held as proofs of mineral fire, in like manner as the proof of
subterraneous fire would necessarily imply mineral fusion as its natural
effect.
Thus we have, in our physical investigation, several points in view.
First, from the present state of things, to infer a former state of
fusion among mineral bodies. Secondly, from that former fusion, to infer
the actual existence of mineral fire in the system of the earth. And,
lastly, from the acknowledged fact of subterraneous fire as a cause, to
reason with regard to the effects of that power in mineral bodies.
But besides the power or effect of subterraneous heat in bodies which
are unorganised, and without system, in the construction of their
different parts, we have to investigate the proper purpose of this great
agent in the system of this world, which may be considered as a species
of organised body. Here, therefore, final causes are to be brought into
view, as well as those which are efficient. Now, in a subject involved
with so much obscurity, as must be for us the internal regions of the
globe, the consideration of efficient and final causes may contribute
mutually to each others evidence, when separately the investigation of
either might be thought unsatisfactory or insufficient.
So far it seemed necessary to premise with regard to the great mineral
power which we are to employ as an agent in the system of this earth;
and it may be now observed, that it is in the proper relation of this
power of heat and the fluidity or softness of bodies, as cause and
effect, that we are to find a physical principle or argument for
detecting those false theories of the earth that have been only
imagined, and not properly founded on fact or observation. It is also by
means of this principle, that we shall be enabled to form a true theory
of the mineral region, in generalising particular effects to a common
cause.
Let us now proceed in endeavouring to decide this important question,
viz. By what active principle is it, that the present state of things,
which we observe in the strata of the earth, a state so very different
from that in which those bodies had been formed originally, has been
brought about?
Two causes have been now proposed for the consolidating of loose
materials which had been in an incoherent state; these are, on the one
hand, fire; or, on the other, water, as the means of bringing about that
event. We are, therefore, to consider well, what may be the consequences
of consolidation by the one or other of those agents; and what may be
the respective powers of those agents with respect to this operation.
If we are not informed in this branch of science, we may gaze without
instruction upon the most convincing proofs of what we want to attain.
If our knowledge is imperfect, we may form erroneous principles, and
deceive ourselves in reasoning with regard to those works of nature,
which are wisely calculated for our instruction.
The strata, formed at the bottom of the sea, are to be considered
as having been consolidated, either by aqueous solution and
crystallization, or by the effect of heat and fusion. If it is in the
first of these two ways that the solid strata of the globe have attained
to their present state, there will be a certain uniformity observable
in the effects; and there will be general laws, by which this operation
must have been conducted. Therefore, knowing those general laws, and
making just observations with regard to the natural appearances of those
consolidated masses, a philosopher, in his closet, should be able to
determine, what may, and what may not have been transacted in the bowels
of the earth, or below the bottom of the ocean.
Let us now endeavour to ascertain what may have been the power of water,
acting under fixed circumstances, operating upon known substances, and
conducting to a certain end.
The action of water upon all different substances is an operation
with which we are familiar. We have it in our power to apply water in
different degrees of heat for the solution of bodies, and under various
degrees of compression; consequently, there is no reason to conclude
any thing mysterious in the operations of the globe, which are to be
performed by means of water, unless an immense compressing power should
alter the nature of those operations. But compression alters the
relation of evaporation only with regard to heat, or it changes the
degree of heat which water may be made to sustain; consequently, we are
to look for no occult quality in water acting upon bodies at the bottom
of the deepest ocean, more than what can be observed in experiments
which we have it in our power to try.
With regard again to the effect of time: Though the continuance of time
may do much in those operations which are extremely slow, where no
change, to our observation, had appeared to take place, yet, where it
is not in the nature of things to produce the change in question, the
unlimited course of time would be no more effectual, than the moment by
which we measure events in our observations.
Water being the general medium in which bodies collected at the bottom
of the sea are always contained, if those masses of collected matter are
to be consolidated by solution, it must be by the dissolution of
those bodies in that water as a menstruum, and by the concretion or
crystallization of this dissolved matter, that the spaces, first
occupied by water in those masses, are afterwards to be filled with a
hard and solid substance; but without some other power, by which the
water contained in those cavities and endless labyrinths of the strata,
should be separated in proportion as it had performed its task, it is
inconceivable how those masses, however changed from the state of their
first subsidence, should be absolutely consolidated, without any visible
or fluid water in their composition.
Besides this difficulty of having the water separated from the porous
masses which are to be consolidated, there is another with which, upon
this supposition, we have to struggle. This is, From whence should come
the matter with which the numberless cavities in those masses are to be
filled?
The water in the cavities and interstices of those bodies composing
strata, must be in a stagnating state; consequently, it can only act
upon the surfaces of those cavities which are to be filled up. But
with what are they to be filled? Not with water; they are full of that
already: Not with the substance of the bodies which contain that water;
this would be only to make one cavity in order to fill up another.
If, therefore, the cavities of the strata are to be filled with solid
matter, by means of water, there must be made to pass through those
porous masses, water impregnated with some other substances in a
dissolved state; and the aqueous menstruum must be made to separate
from the dissolved substance, and to deposit the same in those cavities
through which the solution moves.
By such a supposition as this, we might perhaps explain a partial
consolidation of those strata; but this is a supposition, of which the
case under consideration does not admit; for in the present case, which
is that of materials accumulated at the bottom of the ocean, there is
not proper means for separating the dissolved matter from the water
included in those enormous masses; nor are there any means by which a
circulation in those masses may be formed. In this case, therefore,
where the means are not naturally in the supposition, a philosopher, who
is to explain the phenomenon by the natural operation of water in this
situation, must not have recourse to another agent, still more powerful,
to assist his supposition which cannot be admitted.
Thus, it will appear, that, to consolidate strata formed at the bottom
of the sea, in the manner now considered, operations are required
unnatural to this place; consequently, not to be supposed, in order to
support a hypothesis.
But now, instead of inquiring how far water may be supposed instrumental
in the consolidation of strata which were originally of a loose
texture, we are to consider how far there may be appearances in those
consolidated bodies, by which it might be concluded, whether or not the
present state of their consolidation has been actually brought about by
means of that agent.
If water had been the menstruum by which the consolidating matter was
introduced into the interstices of strata, masses of those bodies could
only be found consolidated with such substances as water is capable of
dissolving; and these substances would be found only in such a state as
the simple separation of the solvent water might produce.
In this case, the consolidation of strata would be extremely limited;
for we cannot allow more power to water than we find it has in nature;
nor are we to imagine to ourselves unlimited powers in bodies, on
purpose to explain those appearances by which we should be made to know
the powers of nature. Let us, therefore, attend, with every possible
circumspection, to the appearances of those bodies, by means of which we
are to investigate the principles of mineralogy, and know the laws of
nature.
The question now before us concerns the consolidating substances of
strata. Are these such as will correspond to the dissolving power of
water, and to the state in which these substances might be left by the
separation of their menstruum? No; far, far from this supposition is the
conclusion that necessarily follows from natural appearances.
We have strata consolidated by calcareous spar, a thing perfectly
distinguishable from the stalactical concretion of calcareous earth,
in consequence of aqueous solution. We have strata made solid by the
formation of fluor, a substance not soluble, so far as we know, by
water. We have strata consolidated with sulphureous and bituminous
substances, which do not correspond to the solution of water. We have
strata consolidated with siliceous matter, in a state different from
that under which it has been observed, on certain occasions, to be
deposited by water. We have strata consolidated by feld-spar, a
substance insoluble in water. We have strata consolidated by almost all
the various metallic substances, with their almost endless mixtures
and sulphureous compositions; that is to say, we find, perhaps, every
different substance introduced into the interstices of strata which had
been formed by subsidence at the bottom of the sea.
If it is by means of water that those interstices have been filled with
those materials, water must be, like fire, an universal solvent, or
cause of fluidity, and we must change entirely our opinion of water in
relation to its chemical character. But there is no necessity thus to
violate our chemical principles, in order to explain certain natural
appearances; more especially if those appearances may be explained in
another manner, consistently with the known laws of nature.
If, again, it is by means of heat and fusion that the loose and porous
structure of strata shall be supposed to have been consolidated, then
every difficulty which had occurred in reasoning upon the power or
agency of water is at once removed. The loose and discontinuous body of
a stratum may be closed by means of softness and compression; the porous
structure of the materials may be consolidated, in a similar manner, by
the fusion of their substance; and foreign matter may be introduced into
the open structure of strata, in form of steam or exhalation, as well as
in the fluid state of fusion; consequently, heat is an agent competent
for the consolidation of strata, which water alone is not. If,
therefore, such an agent could be found acting in the natural place of
strata, we must pronounce it proper to bring about that end.
The examination of nature gives countenance to this supposition, so far
as strata are found consolidated by every species of substance,
and almost every possible mixture of those different substances;
consequently, however difficult it may appear to have this application
of heat, for the purpose of consolidating strata formed at the bottom of
the ocean, we cannot, from natural appearances, suppose any other cause,
as having actually produced the effects which are now examined.
This question, with regard to the means of consolidating the strata of
the globe, is, to natural history, of the greatest importance; and it is
essential in the theory now proposed to be given of the mineral system.
It would, therefore, require to be discussed with some degree of
precision in examining the particulars; but of these, there is so great
a field, and the subject is so complicated in its nature, that volumes
might be written upon particular branches only, without exhausting what
might be laid upon the subject; because the evidence, though strong in
many particulars, is chiefly to be enforced by a multitude of facts,
conspiring, in a diversity of ways, to point out one truth, and by the
impossibility of reconciling all these facts, except by means of one
supposition.
But, as it is necessary to give some proof of that which is to be
a principle in our reasoning afterwards, I shall now endeavour to
generalise the subject as much as possible, in order to answer that end,
and, at the same time, to point out the particular method of inquiry.
There are to be found, among the various strata of the globe, bodies
formed of two different kinds of substances, _siliceous_ bodies, and
those which may be termed _sulphureous_ or _phlogistic_. With one or
other, or both of those we substances, every different consolidated
stratum of the globe will be found so intimately mixed, or closely
connected, that it must be concluded, by whatever cause those bodies
of siliceous and sulphureous matter had been changed from a fluid to a
concreted state, the strata must have been similarly affected by the
same cause.
These two species of bodies, therefore, the siliceous and the
sulphureous, may now be examined, in relation to the causes of their
concretion, with a view to determine, what has been the general
concreting or consolidating power, which has operated universally in the
globe; and particularly to show, it has not been by means of any fluid
solution, that strata in general have been consolidated, or that those
particular substances have been crystallized and concreted.
Siliceous matter, physically speaking, is not soluble in water; that is
to say, in no manner of way have we been enabled to learn, that water
has the power of dissolving this matter.
Many other substances, which are so little soluble in water, that their
solubility could not be otherwise detected of themselves, are made to
appear soluble by means of siliceous matter; such is feld-spar, one of
the component parts of rock-granite.
Feld-spar is a compound of siliceous, argillaceous, and calcareous
earth, intimately united together. This compound siliceous body
being, for ages, exposed to the weather, the calcareous part of it is
dissolved, and the siliceous part is left in form of a soft white earth.
But whether this dissolution is performed by pure water, or by means
also of an acid, may perhaps be questioned. This, however, is certain,
that we must consider siliceous substances as insoluble in water.
The water of Glezer in Iceland undoubtedly contains this substance in
solution; but there is no reason to believe, that it is here dissolved
by any other than the natural means; that is, an alkaline substance, by
which siliceous bodies may be rendered soluble in water[5].
[Note 5: This conjecture, which I had thus formed, has been fully
confirmed by the accurate analysis of those waters. See vol. 3d. of the
Phil. Trans. of Edin.]
It may be, therefore, asserted, that no siliceous body having the
hardness of flint, nor any crystallization of that substance, has ever
been formed, except by fusion. If, by any art, this substance shall be
dissolved in simple water, or made to crystallise from any solution, in
that case, the assertion which has been here made may be denied.
But where there is not the vestige of any proof, to authorise the
supposition of flinty matter being dissolved by water, or crystallized
from that solution, such an hypothesis cannot be admitted, in opposition
to general and evident appearances[6].
[Note 6: The Chevalier de Dolomieu has imagined an ingenious theory for
the solution of siliceous substances in water [Journal de Physique, Mai
1792.]. This theory has not been taken up merely at a venture, but
is founded upon very accurate and interesting chemical experiments.
Hitherto, however, the nature of the siliceous substance is not
sufficiently known, to enable us to found, upon chemical principles, the
mineral operations of nature. That siliceous substance may be dissolved,
or rendered soluble in water, by means of alkaline salt, and that it may
be also volatilised by means of the fluor acid, is almost all that we
know upon the subject. But this is saying no more in relation to the
mineral operations employed upon the siliceous substance, than it would
be, in relation to those upon gold, to say that this metal is dissolved
by aqua regia.
It is to be admitted, that every simple substance may have its
menstruum, by means of which it may be retained with water in a
dissolved state; but from this it does not follow, that it is by the
means of aqueous solutions of all those mineral bodies, that nature
operates the consolidation of bodies, which we find actually
accomplished with all those different substances. It is the business of
this work to show, that from all appearances in the mineral regions, as
well as those upon the surface in the atmosphere, the supposition, of
that manner of consolidating bodies by solution, is inconsistent both
with natural appearances, and also with chemical principles.
Our ingenious author, who has, with, great diligence as well as an
enlightened mind, observed the operations of nature upon the surface
of the earth, here says, "ce n'est pas sans étonnement que je remarque
depuis long-temps que jamais aucune eau qui coule à la surface de la
terre n'attaque le quartz, aucune n'en tient en dissolution, pendant que
celles qui circulent intérieurement le corrodent aussi souvent qu'elles
le déposent."--How dangerous it is in science for ingenious men to allow
themselves to form conclusions, which the principles on which they
reason do not strictly warrant, we have a remarkable example in the
present case.
M. de Dolomieu sees no corrosion of quartz, or solution of that
substance, upon the surface of the earth; from this, then, he concludes,
that siliceous substance is not dissolved in that situation of things.
On the other hand, he finds siliceous bodies variously concreted among
the solid strata of the earth; and, from this he concludes, that
siliceous substance has been both dissolved by water in the strata, and
also there again concreted and crystallised in having been separated
from the water. This is certainly what we all perceive; but we do not
all allow ourselves to draw such inconclusive inferences from our
premises. Notwithstanding the greatest accuracy of our observations,
quartz may be dissolvable in a minute degree by water, upon the surface
of this earth; and, all the appearances of siliceous bodies, in the
mineral regions, where we cannot immediately see the operation, may be
better explained by fusion than by aqueous solution.
But, from his chemical experiments, our author has conjectured that
there may be a phlogistic substance, by means of which the siliceous
earth is dissolved when in darkness; and that this solvent loses its
power, if exposed to the light of day. I have one observation to oppose
to this ingenious theory. Under deep black mosses, through which no ray
of light can penetrate, every condition for dissolving siliceous bodies
should be found, according to the supposition in question; neither will
sufficient time be found wanting, in those deep mosses, upon the summits
of our mountains; yet, examine the matter of fact? not the smallest
solution is to be perceived in the siliceous parts of the stones which
are found under those mosses, but every particle of iron is dissolved,
so that the surface of every stone is white, and nothing but the
siliceous earth of the feld-spar, and perhaps the argillaceous, is left.
Here we have in this author an instructive example: No person, in my
opinion, has made such enlightened or scientific experiments, or such
judicious observations with regard to the nature of siliceous substance,
as a compound thing; no person reasons more distinctly in general, or
sees more clearly the importance of his principles; yet, with regard to
mineral concretions, how often has he been drawn thus inadvertently
into improper generalization! I appeal to the analogy which, in this
treatise, he has formed, between the stalactical concretions upon
the surface of the earth, and the mineral concretions of siliceous
substance. As an example of the great lights, and penetrating genius, of
this assiduous studier of nature, I refer to the judicious observations
which he has made upon the subject of aluminous earth, in this
dissertation.
I am surprised to find this enlightened naturalist seeking, in the
origin of this globe of our earth, a general principle of fluidity or
solution in water, like the alkahest of the alchymists, by means of
which the different substances in the chemical constitution of precious
stones might have been united as well as crystallised. One would
have thought, that a philosopher, so conversant in the operations of
subterraneous fire, would have perceived, that there is but one general
principle of fluidity or dissolution, and that this is heat.]
Besides this proof for the fusion of siliceous bodies, which is
indirect, arising from the in dissolubility of that substance in water,
there is another, which is more direct, being founded upon appearances
which are plainly inconsistent with any other supposition, except that
of simple fluidity induced by heat. The proof I mean is, the penetration
of many bodies with a flinty substance, which, according to every
collateral circumstance, must have been performed by the flinty matter
in a simply fluid state, and not in a state of dissolution by a solvent.
These are flinty bodies perfectly insulated in strata both of chalk and
sand. It requires but inspection to be convinced. It is not possible
that flinty matter could be conveyed into the middle of those strata, by
a menstruum in which it was dissolved, and thus deposited in that place,
without the smallest trace of deposition in the surrounding parts.
But, besides this argument taken from what does not appear, the actual
form in which those flinty masses are found, demonstrates, _first_,
That they have been introduced among those strata in a fluid state, by
injection from some other place. 2_dly_, That they have been dispersed
in a variety of ways among those strata, then deeply immersed at the
bottom of the sea; and, _lastly_, That they have been there congealed
from the state of fusion, and have remained in that situation, while
those strata have been removed from the bottom of the ocean to the
surface of the present land.
To describe those particular appearances would draw this paper beyond
the bounds of an essay. We must, therefore, refer those who would
inquire more minutely into the subject, to examine the chalk-countries
of France and England, in which the flint is found variously formed; the
land-hills interspersed among those chalk-countries, which have been
also injected by melted flint; and the pudding-stone of England, which
I have not seen in its natural situation. More particularly, I would
recommend an examination of the insulated masses of stone, found in
the sand-hills by the city of Brussels; a stone which is formed by an
injection of flint among sand, similar to that which, in a body of
gravel, had formed the pudding-stone of England[7].
[Note 7: Accurate descriptions of those appearances, with drawings,
would be, to natural history, a valuable acquisition.]
All these examples would require to be examined upon the spot, as a
great part of the proof for the fusion of the flinty substance, arises,
in my opinion, from the form in which those bodies are found, and the
state of the surrounding parts. But there are specimens brought from
many different places, which contain, in themselves, the most evident
marks of this injection of the flinty substance in a fluid state. These
are pieces of fossil wood, penetrated with a siliceous substance, which
are brought from England, Germany, and Lochneagh in Ireland.
It appears from these specimens, that there has sometimes been a prior
penetration of the body of wood, either with irony matter, or calcareous
substance. Sometimes, again, which is the case with that of Lochneagh,
there does not seem to have been any penetration of those two
substances. The injected flint appears to have penetrated the body
of this wood, immersed at the bottom of the sea, under an immense
compression of water. This appears from the wood being penetrated
partially, some parts not being penetrated at all.
Now, in the limits between those two parts, we have the most convincing
proofs, that it had been flint in a simple fluid state which had
penetrated the wood, and not in a state of solution.
_First_, Because, however little of the wood is left unpenetrated, the
division is always distinct between the injected part and that which is
not penetrated by the fluid flint. In this case, the flinty matter has
proceeded a certain length, which is marked, and no farther; and, beyond
this boundary, there is no partial impregnation, nor a gradation of the
flintifying operation, as must have been the case if siliceous matter
had been deposited from a solution. 2_dly_, The termination of the
flinty impregnation has assumed such a form, precisely, as would
naturally happen from a fluid flint penetrating that body.
In other specimens of this mineralising operation, fossil wood,
penetrated, more or less, with ferruginous and calcareous substances,
has been afterwards penetrated with a flinty substance. In this case,
with whatever different substances the woody body shall be supposed
to have been penetrated in a state of solution by water, the regular
structure of the plant would still have remained, with its vacuities,
variously filled with the petrifying substances, separated from the
aqueous menstruum, and deposited in the vascular structure of the wood.
There cannot be a doubt with regard to the truth of this proposition;
for, as it is, we frequently find parts of the consolidated wood, with
the vascular structure remaining perfectly in its natural shape and
situation; but if it had been by aqueous solution that the wood had been
penetrated and consolidated, all the parts of that body would be found
in the same natural shape and situation.
This, however, is far from being the case; for while, in some parts, the
vascular structure is preserved entire, it is also evident, that, in
general, the woody structure is variously broken and dissolved by the
fusion and crystallization of the flint. There are so many and such
various convincing examples of this, that, to attempt to describe them,
would be to exceed the bounds prescribed for this dissertation; but such
specimens are in my possession, ready for the inspection of any person
who may desire to study the subject.
We may now proceed to consider sulphureous substances, with regard to
their solubility in water, and to the part which these bodies have acted
in consolidating the strata of the globe.
The sulphureous substances here meant to be considered, are substances
not soluble in, water, so far as we know, but fusible by heat, and
inflammable or combustible by means of heat and vital air. These
substances are of two kinds; the one more simple, the other more
compound.
The most simple kind is composed of two different substances, viz.
phlogiston, with certain specific substances; from which result, on the
one hand, sulphur, and, on the other, proper coal and metals. The more
compound sort, again, is oily matter, produced by vegetables, and
forming bituminous bodies.
The _first_ of these is found naturally combined with almost all
metallic substances, which are then said to be mineralised with sulphur.
Now, it is well known, that this mineralising operation is performed by
means of heat or fusion; and there is no person skilled in chemistry
that will pretend to say, this may be done by aqueous solution. The
combination of iron and sulphur, for example, may easily be performed by
fusion; but, by aqueous solution, this particular combination is again
resolved, and forms an acido-metallic, that is, a vitriolic substance,
after the phlogiston (by means of which it is insoluble in water) has
been separated from the composition, by the assistance of vital air.
The variety of these sulphureo-metallic substances, in point of
composition, is almost indefinite; but, unless they were all soluble in
water, this could not have happened by the action of that solvent. If we
shall allow any one of those bodies to have been formed by the fluidity
of heat, they must all have been formed in the same manner; for there is
such a chain of connection among those bodies in the mineral regions,
that they must all have been composed, either, on the one hand, by
aqueous solution, or, on the other, by means of heat and fusion.
Here, for example, are crystallised together in one mass, 1_st,
Pyrites_, containing sulphur, iron, copper; 2_dly, Blend_, a composition
of iron, sulphur, and calamine; 3_dly, Galena_, consisting of lead
and sulphur; 4_thly, Marmor metallicum_, being the terra ponderosa,
saturated with the vitriolic acid; a substance insoluble in water;
5_thly, Fluor_, a saturation of calcareous earth, with a peculiar acid,
called the _acid of spar_, also insoluble in water; 6_thly, Calcareous
spar_, of different kinds, being calcareous earth saturated with fixed
air, and something besides, which forms a variety in this substance;
_lastly, Siliceous substance_, or _Quartz crystals_. All these bodies,
each possessing its proper shape, are mixed in such a manner as it would
be endless to describe, but which may be expressed in general by saying,
that they are mutually contained in, and contain each other.
Unless, therefore; every one of these different substances may be
dissolved in water, and crystallised from it, it is in vain to look for
the explanation of these appearances in the operations of nature, by the
means of aqueous solution.
On the other hand, heat being capable of rendering all these substances
fluid, they may be, with the greatest simplicity, transported from one
place to another; and they may be made to concrete altogether at
the same time, and distinctly separate in any place. Hence, for the
explanation of those natural appearances, which are so general, no
further conditions are required, than the supposition of a sufficient
intensity of subterraneous fire or heat, and a sufficient degree of
compression upon those bodies, which are to be subjected to that violent
heat, without calcination or change. But, so far as this supposition is
not gratuitous, the appearances of nature will be thus explained.
I shall only mention one specimen, which must appear most decisive
of the question. It is, I believe, from an Hungarian mine. In this
specimen, petro-silex, pyrites, and cinnabar, are so mixed together, and
crystallised upon each other, that it is impossible to conceive any one
of those bodies to have had its fluidity and concretion from a cause
which had not affected the other two. Now, let those who would deny the
fusion of this siliceous body explain how water could dissolve these
three different bodies, and deposit them in their present shape. If,
on the contrary, they have not the least shadow of reason for such a
gratuitous supposition, the present argument must be admitted in its
full force.
Sulphur and metals are commonly found combined in the mineral regions.
But this rule is not universal; for they are also frequently in a
separate state. There is not, perhaps, a metal, among the great number
which are now discovered, that may not be found native, as they are
called, or in their metallic state.
Metallic substances are also thus found in some proportion to the
disposition of the particular metals, to resist the mineralising
operations, and to their facility of being metallised by fire and
fusion. Gold, which refuses to be mineralised with sulphur, is found
generally in its native state. Iron, again, which is so easily
mineralised and scorified, is seldom found in its malleable state. The
other metals are all found more or less mineralised, though some of them
but rarely in the native state.
Besides being found with circumstances thus corresponding to the natural
facility, or to the impediments attending the metallization of those
different calces, the native metals are also found in such a shape, and
with such marks, as can only agree with the fusion of those bodies;
that is to say, those appearances are perfectly irreconcilable with any
manner of solution and precipitation.
For the truth of this assertion, among a thousand other examples, I
appeal to that famous mass of native iron discovered by Mr Pallas in
Siberia. This mass being so well known to all the mineralists of Europe,
any comment upon its shape and structure will be unnecessary[8].
[Note 8: Since this Dissertation was written, M. de la Peyrouse has
discovered a native manganese. The circumstances of this mineral are so
well adapted for illustrating the present doctrine, and so well related
by M. de la Peyrouse, that I should be wanting to the interest of
mineral knowledge, were I not to give here that part of his Memoir.
"Lorsque je fis insérer dans le journal de physique de l'année 1780, au
mois de Janvier, une Dissertation contenant la classification des mines
de manganèse, je ne connoissois point, à cette époque, la mine de
manganèse native. Elle a la couleur de son régule: Elle salit les doigts
de la même teinte. Son tissu parait aussi lamelleux, et les lames
semblent affecter une sorte de divergence. Elle a ainsi que lui, l'éclat
métallique; comme lui elle se laisse aplatir sous le marteau, et
s'exfolie si l'on redouble les coups; mais une circonstance qui est trop
frappante pour que je l'omette, c'est la figure de la manganèse native,
si prodigieusement conforme à celle du régule, qu'on s'y laisseroit
tromper, si la mine n'étoit encore dans sa gangue: Figure
très-essentielle à observer ici, parce qu'elle est due à la nature même
de la manganèse. En effet, pour réduire toutes les mines en général, il
faut employer divers flux appropriés. Pour la réduction de la manganèse,
bien loin d'user de ce moyen, il faut, au contraire, éloigner tout flux,
produire la fusion, par la seule violence et la promptitude du feu. Et
telle est la propension naturelle et prodigieuse de la manganèse à la
vitrification, qu'on n'a pu parvenir encore à réduire son régule en un
seul culot; on trouve dans le creuset plusieurs petits boutons, qui
forment autant de culots séparés. Dans la mine de manganèse native, elle
n'est point en une seule masse; elle est disposée également en plusieurs
culots séparés, et un peu aplatis, comme ceux que l'art produit;
beaucoup plus gros, à la vérité, parce que les agens de la nature
doivent avoir une autre énergie, que ceux de nos laboratoires; et cette
ressemblance si exacte, semble devoir vous faire penser que la mine
native à été produite par le feu, tout comme son régule. La présence
de la chaux argentée de la manganèse, me permettroit de croire que la
nature n'a fait que réduire cette chaux. Du reste, cette mine native
est très-pure, et ne contient aucune partie attirable à l'aimant. Cette
mine, unique jusqu'à ce moment, vient, tout comme les autres manganèse
que j'ai décrites, des mines de fer de _Sem_, dans la vallée de
_Viedersos_, en Comté de Foix."--_Journal de Physique, Janvier 1786_.]
We come now to the _second_ species of inflammable bodies called oily or
bituminous. These substances are also found variously mixed with mineral
bodies, as well as forming strata of themselves; they are, therefore, a
proper subject for a particular examination.
In the process of vegetation, there are produced oily and resinous
substances; and, from the collection of these substances at the bottom
of the ocean, there are formed strata, which have afterwards undergone
various degrees of beat, and have been variously changed, in consequence
of the effects of that heat, according as the distillation of the more
volatile parts of those bodies has been suffered to proceed.
In order to understand this, it must be considered, that, while immersed
in water, and under insuperable compression, the vegetable, oily, and
resinous substances, would appear to be unalterable by heat; and it is
only in proportion as certain chemical separations take place, that
these inflammable bodies are changed in their substance by the
application of heat. Now, the most general change of this kind is in
consequence of evaporation, or the distillation of their more volatile
parts, by which oily substances become bituminous, and bituminous
substances become coaly.
There is here a gradation which may be best understood, by comparing the
extremes.
On the one hand, we know by experiment, that oily and bituminous
substances can be melted and partly changed into vapour by heat, and
that they become harder and denser, in proportion as the more volatile
parts have evaporated from them. On the other hand, coaly substances are
destitute of fusibility and volatility, in proportion as they have
been exposed to greater degrees of heat, and to other circumstances
favourable to the dissipation of their more volatile and fluid parts.
If, therefore, in mineral bodies, we find the two extreme states of this
combustible substance, and also the intermediate states, we must either
conclude, that this particular operation of heat has been thus actually
employed in nature, or we must explain those appearances by some other
means, in as satisfactory a manner, and so as shall be consistent with
other appearances.
In this case, it will avail nothing to have recourse to the false
analogy of water dissolving and crystallising salts, which has been so
much employed for the explanation of other mineral appearances. The
operation here in question is of a different nature, and necessarily
requires both the powers of heat and proper conditions for evaporation.
Therefore, in order to decide the point, with regard to what is the
power in nature by which mineral bodies have become solid, we have
but to find bituminous substance in the most complete state of coal,
intimately connected with some other substance, which is more generally
found consolidating the strata, and assisting in the concretion of
mineral substances. But I have in my possession the most undoubted proof
of this kind. It is a mineral vein, or cavity, in which are blended
together coal of the most fixed kind, quartz and marmor metallicum. Nor
is this all; for the specimen now referred to is contained in a rock
of this kind, which every naturalist now-a-days will allow to have
congealed from a fluid state of fusion. I have also similar specimens
from the same place, in which the coal is not of that fixed and
infusible kind which burns without flame or smoke, but is bituminous or
inflammable coal.
We have hitherto been resting the argument upon a single point, for the
sake of simplicity or clearness, not for want of those circumstances
which shall be found to corroborate the theory. The strata of fossil
coal are found in almost every intermediate state, as well as in those
of bitumen and charcoal. Of the one kind is that fossil coal which melts
or becomes fluid upon receiving heat; of the other, is that species of
coal, found both in Wales and Scotland, which is perfectly infusible in
the fire, and burns like coals, without flame or smoke. The one species
abounds in oily matter, the other has been distilled by heat, until it
has become a _caput mortuum_, or perfect coal.
The more volatile parts of these bituminous bodies are found in their
separate state on some occasions. There is a stratum of limestone in
Fifeshire, near Raith, which, though but slightly tinged with a black
colour, contains bituminous matter, like pitch, in many cavities, which
are lined with calcareous spar crystallised. I have a specimen of such
a cavity, in which the bitumen is in sphericles, or rounded drops,
immersed in the calcareous spar.
Now, it is to be observed, that, if the cavity in the solid limestone or
marble, which is lined with calcareous crystals containing pyrites, had
been thus encrusted by means of the filtration of water, this water must
have dissolved calcareous spar, pyrites, and bitumen. But these natural
appearances would not even be explained by this dissolution and supposed
filtration of those substances. There is also required, _first_, A
cause for the separation of those different substances from the aqueous
menstruum in which they had been dissolved; _2dly_, An explanation of
the way in which a dissolved bitumen should be formed into round hard
bodies of the most solid structure; and, _lastly_, Some probable means
for this complicated operation being performed, below the bottom of the
ocean, in the close cavity of a marble stratum.
Thus, the additional proof, from the facts relating to the bituminous
substances, conspiring with that from the phenomena of other bodies,
affords the strongest corroboration of this opinion, that the various
concretions found in the internal parts of strata have not been
occasioned by means of aqueous solution, but by the power of heat and
operation of simple fusion, preparing those different substances to
concrete and crystallise in cooling.
The arguments which have been now employed for proving that strata have
been consolidated by the power of heat, or by the means of fusion, have
been drawn chiefly from the insoluble nature of those consolidating
substances in relation to water, which is the only general menstruum
that can be allowed for the mineral regions. But there are found, in
the mineral kingdom, many solid masses of saltgem, which is a soluble
substance. It may be now inquired, How far these masses, which are not
infrequent in the earth, tend either to confirm the present theory, or,
on the contrary, to give countenance to that which supposes water the
chief instrument in consolidating strata.
The formation of salt at the bottom of the sea, without the assistance
of subterranean fire, is not a thing unsupposable, as at first sight
it might appear. Let us but suppose a rock placed across the gut
of Gibraltar, (a case nowise unnatural), and the bottom of the
Mediterranean would be certainly filled with salt, because the
evaporation from the surface of that sea exceeds the measure of its
supply.
But strata of salt, formed in this manner at the bottom of the sea, are
as far from being consolidated by means of aqueous solution, as a bed of
sand in the same situation; and we cannot explain the consolidation of
such a stratum of salt by means of water, without supposing subterranean
heat employed, to evaporate the brine which would successively occupy
the interstices of the saline crystals. But this, it may be observed, is
equally departing from the natural operation of water, as the means for
consolidating the sediment of the ocean, as if we were to suppose
the same thing done by heat and fusion. For the question is not,
If subterranean heat be of sufficient intensity for the purpose of
consolidating strata by the fusion of their substances; the question is,
Whether it be by means of this agent, subterranean heat, or by water
alone, without the operation of a melting heat, that those materials
have been variously consolidated.
The example now under consideration, consolidated mineral salt, will
serve to throw some light upon the subject; for, as it is to be shown,
that this body of salt had been consolidated by perfect fusion, and
not by means of aqueous solution, the consolidation of strata of
indissoluble substances, by the operation of a melting heat, will meet
with all that confirmation which the consistency of natural appearances
can give.
The salt rock in Cheshire lies in strata of red marl. It is horizontal
in its direction. I do not know its thickness, but it is dug thirty or
forty feet deep. The body of this rock is perfectly solid, and the salt,
in many places, pure, colourless, and transparent, breaking with a
sparry cubical structure. But the greatest part is tinged by the
admixture of the marl, and that in various degrees, from the slightest
tinge of red, to the most perfect opacity. Thus, the rock appears as if
it had been a mass of fluid salt, in which had been floating a quantity
of marly substance, not uniformly mixed, but every where separating and
subsiding from the pure saline substance.
There is also to be observed a certain regularity in this separation of
the tinging from the colourless substance, which, at a proper distance,
gives to the perpendicular section of the rock a distinguishable figure
in its structure. When looking at this appearance near the bottom of
the rock, it, at first, presented me with the figure of regular
stratification; but, upon examining the whole mass of rock, I found,
that it was only towards the bottom that this stratified appearance took
place; and that, at the top of the rock, the most beautiful and regular
figure was to be observed; but a figure the most opposite to that of
stratification. It was all composed of concentric circles; and these
appeared to be the section of a mass, composed altogether of concentric
spheres, like those beautiful systems of configuration which agates so
frequently present us with in miniature. In about eight or ten feet from
the top, the circles growing large, were blended together, and gradually
lost their regular appearance, until, at a greater depth, they again
appeared in resemblance of a stratification.
This regular arrangement of the floating marly substance in the body
of salt, which is that of the structure of a coated pebble, or that
of concentric spheres, is altogether inexplicable upon any other
supposition, than the perfect fluidity or fusion of the salt, and the
attractions and repulsions of the contained substances. It is in vain
to look, in the operations of solution and evaporation, for that which
nothing but perfect fluidity or fusion can explain.
This example of a mineral salt congealed from a melted state, may be
confirmed from another which I have from Dr Black, who suggested it to
me. It is an alkaline salt, found in a mineral state, and described in
the Philosophical Transactions, _anno_ 1771. But to understand this
specimen, something must be premised with regard to the nature of fossil
alkali.
The fossil alkali crystallises from a dissolved state, in combining
itself with a large portion of the water, in the manner of alum; and,
in this case, the water is essential to the constitution of that
transparent crystalline body; for, upon the evaporation of the water,
the transparent salt loses its solidity, and becomes a white powder. If,
instead of being gently dried, the crystalline salt is suddenly exposed
to a sufficient degree of heat, that is, somewhat more than boiling
water, it enters into the state of aqueous fusion, and it boils, in
emitting the water by means of which it had been crystallised in the
cold, and rendered fluid in that heated state. It is not possible to
crystallise this alkaline salt from a dissolved state, without the
combination of that quantity of water, nor to separate that water
without destroying its crystalline state.
But in this mineral specimen, we have a solid crystalline salt, with
a structure which, upon fracture, appears to be sparry and radiated,
something resembling that of zeolite. It contains no water in its
crystallization, but melts in a sufficient heat, without any aqueous
fusion. Therefore, this salt must have been in a fluid state of fusion,
immediately before its congelation and crystallization.
It would be endless to give examples of particular facts, so many are
the different natural appearances that occur, attended with a variety of
different circumstances.
There is one, however, which is peculiarly distinct, admits of
sufficiently accurate description, and contains circumstances from which
conclusions may be drawn with clearness. This is the ironstone, which
is commonly found among the argillaceous strata, attendant upon fossil
coal, both in Scotland and in England.
This stone is generally found among the bituminous schistus, or black
argillaceous strata, either in separate masses of various shapes and
sizes, or forming of itself strata which are more or less continuous in
their direction among the schistous or argillaceous beds.
This mineral contains, in general, from 40 to 50 _per cent._ of iron,
and it loses near one third of its weight in calcination. Before
calcination it is of a grey colour, is not penetrable by water, and
takes a polish. In this state, therefore, it is perfectly solid; but
being calcined, it becomes red, porous, and tender.
The fact to be proved with regard to these iron-stones is this, That
they have acquired their solid state from fusion, and not in concreting
from any aqueous solution.
To abridge this disquisition, no argument is to be taken from contingent
circumstances, (which, however, are often found here as well as in the
case of marbles); such only are to be employed as are general to the
subject, and arise necessarily from the nature of the operation.
It will be proper to describe a species of these stones, which is
remarkably regular in its form. It is that found at Aberlady, in East
Lothian.
The form of these iron-stones is that of an oblate or much compressed
sphere, and the size from two or three inches diameter to more than
a foot. In the circular or horizontal section, they present the most
elegant septarium[9]; and, from the examination of this particular
structure, the following conclusions may be drawn.
_First_, That, the septa have been formed by the uniform contraction
of the internal parts of the stone, the volume of the central parts
diminishing more than that of the circumference; by this means, the
separations of the stone diminish, in a progression from the center
towards the circumference.
_2d_, That there are only two ways in which the septa must have received
the spar or spatthose ore with which they are filled, more or less,
either, _first_ By insinuation into the cavity of the septa after these
were formed; or, _2dly_, By separation from the substance of the stone,
at the same time that the septa were forming.
[Note 9: Plate I.]
Were the first supposition true, appearances would be observable,
showing that the sparry substance had been admitted, either through the
porous structure of the stone, or through proper apertures communicating
from without. Now, if either one or other of these had been the case,
and that the stone had been consolidated from no other cause than
concretion from a dissolved state, that particular structure of the
stone, by means of which the spar had been admitted, must appear at
present upon an accurate examination.
This, however, is not the case, and we may rest the argument here. The
septa reach not the circumference; the surface of the stone is solid and
uniform in every part; and there is not any appearance of the spar in
the argillaceous bed around the stone.
It, therefore, necessarily follows, that the contraction of the
iron-stone, in order to form septa, and the filling of these cavities
with spar, had proceeded _pari passu_; and that this operation must have
been brought about by means of fusion, or by congelation from a state of
simple fluidity and expansion.
It is only further to be observed, that all the arguments which have
been already employed, concerning mineral concretions from a simply
fluid state, or that of fusion, here take place. I have septaria of this
kind, in which, besides pyrites, iron-ore, calcareous spar, and another
that is ferruginous and compound, there is contained siliceous
crystals; a case which is not so common. I have them also attended with
circumstances of concretion and crystallization, which, besides being
extremely rare, are equally curious and interesting.
There is one fact more which is well worth our attention, being one
of those which are so general in the mineral regions. It is the
crystallizations which are found in close cavities of the most solid
bodies.
Nothing is more common than this appearance. Cavities are every where
found closely lined with crystallizations, of every different substance
which may be supposed in those places. These concretions are well known
to naturalists, and form part of the beautiful specimens which
are preserved in the cabinets of collectors, and which the German
mineralists have termed _Drusen_. I shall only particularise one
species, which may be described upon principle, and therefore may be
a proper subject on which to reason, for ascertaining the order of
production in certain bodies. This body, which we are now to examine, is
of the agate species.
We have now been considering the means employed by nature in
consolidating strata which were originally of an open structure; but in
perfectly solid strata we find bodies of agate, which have evidently
been formed in that place where they now are found. This fact, however,
is not still that of which we are now particularly to inquire; for this,
of which we are to treat, concerns only a cavity within this agate; now,
whatever may have been the origin of the agate itself, we are to show,
from what appears within its cavity, that the crystallizations which are
found in this place had arisen from a simply fluid state, and not from
that of any manner of solution.
The agates now in question are those of the coated kind, so frequent in
this country, called pebbles. Many of these are filled with a siliceous
crystallization, which evidently proceeds from the circumference
towards the centre. Many of them, again, are hollow. Those cavities are
variously lined with crystallized substances; and these are the object
of the present examination.
But before describing what is found within, it is necessary to attend to
this particular circumstance, that the cavity is perfectly inclosed with
many solid coats, impervious to air or water, but particularly with
the external cortical part, which is extremely hard, takes the highest
polish, and is of the most perfect solidity, admitting the passage of
nothing but light and heat.
Within these cavities, we find, _1st_, The coat of crystals with which
this cavity is always lined; and this is general to all substances
concreting, in similar circumstances, from a state of fusion; for when
thus at liberty they naturally crystallise. _2dly_, We have frequently
a subsequent crystallization, resting on the first, and more or less
immersed in it. _3dly_, There is also sometimes a third crystallization,
superincumbent on the second, in like manner as the second was on the
first. I shall mention some particulars.
I have one specimen, in which the primary crystals are siliceous, the
secondary thin foliaceous crystals of deep red but transparent iron-ore,
forming elegant figures, that have the form of roses. The tertiary
crystallization is a frosting of small siliceous crystals upon the edges
of the foliaceous crystals.
In other specimens, there is first a lining of colourless siliceous
crystals, then another lining of amethystine crystals, and sometimes
within that, fuliginous crystals. Upon these fuliginous and amethystine
crystals are many sphericles or hemispheres of red compact iron-ore,
like haematites.
In others, again, the primary crystals are siliceous, and the secondary
calcareous. Of this kind, I have one which has, upon the calcareous
crystals, beautiful transparent siliceous crystals, and iron sphericles
both upon all these crystals, and within them.
_Lastly_, I have an agate formed of various red and white coats, and
beautifully figured. The cavity within the coated part of the pebble is
filled up without vacuity, first, with colourless siliceous crystals;
secondly, with fuliginous crystals; and, lastly, with white or
colourless calcareous spar. But between the spar and crystals there are
many sphericles, seemingly of iron, half sunk into each of these two
different substances.
From these facts, I may now be allowed to draw the following
conclusions:
1_st_, That concretion had proceeded from the surface of the agate body
inwards. This necessarily follows from the nature of those figured
bodies, the figures of the external coats always determining the shape
of those within, and never, contrarily, those within affecting those
without.
2_dly_, That when the agate was formed, the cavity then contained every
thing which now is found within it, and nothing more.
3_dly_, That the contained substances must have been in a fluid state,
in order to their crystallizing.
_Lastly_, That as this fluid state had not been the effect of solution
in a menstruum, it must have been fluidity from heat and fusion.
Let us now make one general observation and argument with regard to
the formation of those various coated, concreted, crystallized, and
configured bodies. Were the crystallization and configuration found
to proceed from a central body, and to be directed from that centre
outwards, then, without inquiring into collateral appearances, and other
proofs with regard to the natural concretion of those substances, we
might suppose that these concretions might have proceeded from that
central body gradually by accretion, and that the concreting and
crystallizing substances might have been supplied from a fluid which had
before retained the concreting substance in solution; in like manner as
the crystallizations of sugar, which are formed in the solution of
that saccharine substance, and are termed candies, are formed upon the
threads which are extended in the crystallizing vessel for that purpose.
But if, on the contrary, we are to consider those mineral bodies as
spheres of alternate coats, composed of agate, crystal, spars, etc.; and
if all those crystallizations have their _bases_ upon the uncrystallized
coat which is immediately external to it, and their _apices_ turned
inwards into the next internal solid coat, it is not possible to
conceive that a structure of this kind could have been formed in
any manner from a solution. But this last manner is the way without
exception in which those mineral bodies are found; therefore we are to
conclude, that the concretion of those bodies had proceeded immediately
from a state of fusion or simple fluidity.
In granite these cavities are commonly lined with the crystal
corresponding to the constituent substances of the stone, viz. quartz,
feld-spar, and mica or talk. M. de Saussure, (Voyages dans les Alpes,
tom. ii. §722.), says, "On trouve fréquemment des amas considérables de
spath calcaire, crystallisé dans les grottes ou se forme le crystal de
roche; quoique ces grottes soient renfermées dans le coeur des montagnes
d'un granit vif, & qu'on ne voie aucun roc calcaire au dessus de ces
montagnes."
So accurate an observer, and so complete a naturalist, must have
observed how the extraneous substance had been introduced into this
cavity, had they not been formed together the cavity and the calcareous
crystals. That M. de Saussure perceived no means for that introduction,
will appear from what immediately follows in that paragraph. "Ces rocs
auroient-ils été détruits, ou bien ce spath n'est il que le produit
d'une sécrétion des parties calcaires que l'on fait êtres dispersées
entre les divers élémens du granit?"
Had M. de Saussure allowed himself to suppose all those substances in
fusion, of which there cannot be a doubt, he would soon have resolved
both this difficulty, and also that of finding molybdena crystallized
along with feld-spar, in a cavity of this kind. §718.
To this argument, taken from the close cavities in our agates, I am now
to add another demonstration. It is the case of the calcedony agate,
containing a body of calcareous spar; here it is to be shown, that,
while the calcareous body was altogether inclosed within the calcedony
nodular body, these two substances had been perfectly soft, and had
mutually affected each others shape, in concreting from a fluid state.
In order to see this, we are to consider that both those substances have
specific shapes in which they concrete from the third state; the
sparry structure of the one is well known; the spherical or mammelated
crystallization of the calcedony, is no less conspicuous; this last
is, in the present case, spherical figures, which are some of
them hemispheres, or even more. The figures which we have now in
contemplation are so distinctly different as cannot be mistaken; the
one is a rhombic figure bounded by planes; the other is a most perfect
spherical form; and both these are specific figures, belonging
respectively to the crystallization of those two substances.
The argument now to be employed for proving that those two bodies had
concreted from the fluid state of fusion, and not from any manner of
solution, is this: That, were the one of those bodies to be found
impressing the other with its specific figure, we must conclude that the
impressing body had concreted or crystallized while the impressed body
was in a soft or fluid state; and that, if they are both found mutually
impressing and impressed by each other, they must have both been in
the fluid and concreting state together. Now the fact is, that the
calcareous body is perfectly inclosed within the solid calcedony, and
that they are mutually impressed by each others specific figure, the
sparry structure of the calcareous body impressing the calcedony with
its type of planes and angles, at the same time that, in other parts,
the spherical figures of the calcedony enter the solid body of the
spar, and thus impress their mammelated figures into that part which is
contiguous. It is therefore inconceivable, that these appearances
could have been produced in any other manner than by those two bodies
concreting from a simply fluid state.
There are in jaspers and agates many other appearances, from whence the
fusion of those substances may be concluded with great certainty and
precision; but it is hoped, that what has been now given may suffice for
establishing that proposition without any doubt.
It must not be here objected, That there are frequently found siliceous
crystals and amethysts containing water; and that it is impossible
to confine water even in melted glass. It is true, that here, at the
surface of the earth, melted glass cannot, in ordinary circumstances, be
made to receive and inclose condensed water; but let us only suppose a
sufficient degree of compression in the body of melted glass, and we
can easily imagine it to receive and confine water as well as any
other substance. But if, even in our operations, water, by means of
compression, may be made to endure the heat of red hot iron without
being converted into vapour, what may not the power of nature be able to
perform? The place of mineral operations is not on the surface of the
earth; and we are not to limit nature with our imbecility, or estimate
the powers of nature by the measure of our own.[10]
[Note 10: This is so material a principle in the theory of consolidating
the strata of the earth by the fusion of mineral substances, that I beg
the particular attention of the reader to that subject. The effect of
compression upon compound substances, submitted to increased degrees of
heat, is not a matter of supposition, it is an established principle
in natural philosophy. This, like every other physical principle, is
founded upon matter of fact or experience; we find, that many compound
substances may with heat be easily changed, by having their more
volatile parts separated when under a small compression; but these
substances are preserved without change when sufficiently compressed.
Our experiments of this kind are necessarily extremely limited; they
are not, however, for that reason, the less conclusive. The effects of
increasing degrees of heat are certainly prevented by increasing degrees
of compression; but the rate at which the different effects of those
powers proceed, or the measure of those different degrees of increase
that may be made without changing the constitution of the compound
substance, are not known; nor is there any limit to be set to that
operation, so far as we know. Consequently, it is a physical principle,
That the evaporation of volatile substances by heat, or the reparation
of them from a compound substance, consequently the effect of fire in
changing that compound substance, may be absolutely prevented by means
of compression.
It now remains to be considered, how far there is reason to conclude
that there had been sufficient degrees of compression in the mineral
regions, for the purpose of melting the various substances with which we
find strata consolidated, without changing the chemical constitution of
those compound substances.
Had I, in reasoning _a priori_, asserted, That all mineral bodies might
have been melted without change, when under sufficient compression,
there might have arisen, in the minds of reasoning men, some doubt with
regard to the certainty of that proposition, however probable it were to
be esteemed: But when, in reasoning _a posteriori_, it is found that all
mineral bodies have been actually melted, then, all that is required to
establish the proposition on which I have founded my theory, is to
see that there must have been immense degrees of compression upon the
subjects in question; for we neither know the degree of heat which had
been employed, nor that of compression by which the effect of the heat
must have been modified.
Now, in order to see that there had been immense compression, we have
but to consider that the formation of the strata, which are to be
consolidated, was at the bottom of the ocean, and that this place is to
us unfathomable. If it be farther necessary to show that it had been at
such unfathomable depth strata were consolidated, it will be sufficient
to observe, it is not upon the surface of the earth, or above the level
of the sea, that this mineral operation can take place; for, it is there
that those consolidated bodies are redissolved, or necessarily going
into decay, which is the opposite to that operation which we are now
inquiring after; therefore, if they were consolidated in any other place
than at the bottom of the sea, it must have been between that place of
their formation and the surface of the sea; but that is a supposition
which we have not any reason to make; therefore, we must conclude that
it was at the bottom of the ocean those stratified bodies had been
consolidated.]
To conclude this long chemico-mineral disquisition, I have specimens in
which the mixture of calcareous, siliceous, and metallic substances,
in almost every species of concretion which is to be found in mineral
bodies, may be observed, and in which there is exhibited, in miniature,
almost every species of mineral transaction, which, in nature, is found
upon a scale of grandeur and magnificence. They are nodules contained in
the whin-stone, porphyry, or basaltes of the Calton-hill, by Edinburgh;
a body which is to be afterwards examined, when it will be found to have
flowed, and to have been in fusion, by the operation of subterraneous
heat.
This evidence, though most conclusive with regard to the application of
subterraneous heat, as the means employed in bringing into fusion all
the different substances with which strata may be found consolidated, is
not directly a proof that strata had been consolidated by the fusion of
their proper substance. It was necessary to see the general nature of
the evidence, for the universal application of subterraneous heat, in
the fusion of every kind of mineral body. Now, that this has been done,
we may give examples of strata consolidated without the introduction
of foreign matter, merely by the softening or fusion of their own
materials.
For this purpose, we may consider two different species of strata,
such as are perfectly simple in their nature, of the most distinct
substances, and whose origin is perfectly understood, consequently,
whose subsequent changes may be reasoned upon with certainty and
clearness. These are the siliceous and calcareous strata; and these
are the two prevailing substances of the globe, all the rest being, in
comparison of these, as nothing; for unless it be the bituminous or coal
strata, there is hardly any other which does not necessarily contain
more or less of one or other of these two substances. If, therefore,
it can be shown, that both of those two general strata have been
consolidated by the simple fusion of their substance, no _desideratum_
or doubt will remain, with regard to the nature of that operation which
has been transacted at great depths of the earth, places to which all
access is denied to mortal eyes.
We are now to prove, _first_, That those strata have been consolidated
by simple fusion; and, _2dly_, That this operation is universal, in
relation to the strata of the earth, as having produced the various
degrees of solidity or hardness in these bodies.
I shall first remark, that a fortuitous collection of hard bodies, such
as gravel and sand, can only touch in points, and cannot, while in that
hard state, be made to correspond so precisely to each others shape as
to consolidate the mass. But if these hard bodies should be softened in
their substance, or brought into a certain degree of fusion, they
might be adapted mutually to each other, and thus consolidate the open
structure of the mass. Therefore, to prove the present point, we have
but to exhibit specimens of siliceous and calcareous strata which have
been evidently consolidated in this manner.
Of the first kind, great varieties occur in this country. It is,
therefore, needless to describe these particularly. They are the
consolidated strata of gravel and sand, often containing abundance of
feld-spar, and thus graduating into granite; a body, in this respect,
perfectly similar to the more regular strata which we now examine.
The second kind, again, are not so common in this country, unless
we consider the shells and coralline bodies in our lime-stones, as
exhibiting the same example, which indeed they do. But I have a specimen
of marble from Spain, which may be described, and which will afford the
most satisfactory evidence of the fact in question.
This Spanish marble may be considered as a species of pudding-stone,
being formed of calcareous gravel; a species of marble which, from Mr
Bowles' Natural History, appears to be very common in Spain. The gravel
of which this marble is composed, consists of fragments of other marbles
of different kinds. Among these, are different species of _oolites_
marble, some shell marbles, and some composed of a chalky substance, or
of undistinguishable parts. But it appears, that all these different
marbles had been consolidated or made hard, then broken into fragments,
rolled and worn by attrition, and thus collected together, along with
some sand or small siliceous bodies, into one mass. Lastly, This
compound body is consolidated in such a manner as to give the most
distinct evidence, that this had been executed by the operation of heat
or simple fusion.
The proof I give is this, That besides the general conformation of those
hard bodies, so as to be perfectly adapted to each other's shape, there
is, in some places, a mutual indentation of the different pieces of
gravel into each other; an indentation which resembles perfectly that
junction of the different bones of the _cranium_, called sutures, and
which must have necessarily required a mixture of those bodies while in
a soft or fluid state.
This appearance of indentation is by no means singular, or limited to
one particular specimen. I have several specimens of different marbles,
in which fine examples of this species of mixture may be perceived. But
in this particular case of the Spanish pudding-stone, where the mutual
indentation is made between two pieces of hard stone, worn round by
attrition, the softening or fusion of these two bodies is not simply
rendered probable, but demonstrated.
Having thus proved, that those strata had been consolidated by simple
fusion, as proposed, we now proceed to show, that this mineral operation
had been not only general, as being found in all the regions of the
globe, but universal, in consolidating our earth in all the various
degrees, from loose and incoherent shells and sand, to the most solid
bodies of the siliceous and calcareous substances.
To exemplify this in the various collections and mixtures of sands,
gravels, shells, and corals, were endless and superfluous. I shall only
take, for an example, one simple homogeneous body, in order to exhibit
it in the various degrees of consolidation, from the state of simple
incoherent earth to that of the most solid marble. It must be evident
that this is chalk; naturally a soft calcareous earth, but which may be
also found consolidated in every different degree.
Through the middle of the Isle of Wight, there runs a ridge of hills of
indurated chalk. This ridge runs from the Isle of Wight directly west
into Dorsetshire, and goes by Corscastle towards Dorchester, perhaps
beyond that place. The sea has broke through this ridge at the west
end of the Isle of Wight, where columns of the indurated chalk remain,
called the Needles; the same appearance being found upon the opposite
shore in Dorsetshire.
In this field of chalk, we find every gradation of that soft earthy
substance to the most consolidated body of this indurated ridge, which
is not solid marble, but which has lost its chalky property, and has
acquired a kind of stony hardness.
We want only further to see this cretaceous substance in its most
indurated and consolidated state; and this we have in the north of
Ireland, not far from the Giants Causeway. I have examined cargoes of
this lime-stone brought to the west of Scotland, and find the most
perfect evidence of this body having been once a mass of chalk, which is
now a solid marble.
Thus, if it is by means of fusion that the strata of the earth have
been, in many places, consolidated, we must conclude, that all the
degrees of consolidation, which are indefinite, have been brought about
by the same means.
Now, that all the strata of the mineral regions, which are those only
now examined, have been consolidated in some degree, is a fact for which
no proof can be offered here, but must be submitted to experience and
inquiry; so far, however, as they shall be considered as consolidated in
any degree, which they certainly are in general, we have investigated
the means which had been employed in that mineral operation.
We have now considered the concretions of particular bodies, and the
general consolidation of strata; but it may be alleged, that there is
a great part of the solid mass of this earth not properly comprehended
among those bodies which have been thus proved to be consolidated by
means of fusion. The body here alluded to is granite; a mass which is
not generally stratified, and which, being a body perfectly solid,
and forming some part in the structure of this earth, deserves to be
considered.
The nature of granite, as a part of the structure of the earth, is too
intricate a subject to be here considered, where we only seek to prove
the fusion of a substance from the evident marks which are to be
observed in a body. We shall, therefore, only now consider one
particular species of granite; and if this shall appear to have been in
a fluid state of fusion, we may be allowed to extend this property to
all the kind.
The species now to be examined comes from the north country, about four
or five miles west from Portfoy, on the road to Huntly. I have not been
upon the spot, but am informed that this rock is immediately connected
or continuous with the common granite of the country. This indeed
appears in the specimens which I have got; for, in some of these, there
is to be perceived a gradation from the regular to the irregular sort.
This rock may indeed be considered, in some respects, as a porphyry; for
it has an evident ground, which is feld-spar, in its sparry state;
and it is, in one view, distinctly maculated with quartz, which is
transparent, but somewhat dark-coloured[11].
[Note 11: Plate II. fig. 1. 2. 3.]
Considered as a porphyry, this specimen is no less singular than as a
granite. For, instead of a siliceous ground, maculated with the rhombic
feld-spar, which is the common state of porphyry, the ground is
uniformly crystallised, or a homogeneous regular feld-spar, maculated
with the transparent siliceous substance. But as, besides the feld-spar
and quartz, which are the constituent parts of the stone, there is also
mica, in some places, it may, with propriety, be termed a granite.
The singularity of this specimen consists, not in the nature or
proportions of its constituent parts, but in the uniformity of the
sparry ground, and the regular shape of the quartz mixture. This
siliceous substance, viewed in one direction, or longitudinally, may
be considered as columnar, prismatical, or continued in lines running
nearly parallel. These columnar bodies of quartz are beautifully
impressed with a figure on the sides, where they are in contact with the
spar. This figure is that of furrows or channels, which are perfectly
parallel, and run across the longitudinal direction of the quartz. This
is represented in fig. 4. This striated figure is only seen when, by
fracture, the quartz is separated from the contiguous spar.
But what I would here more particularly represent is, the transverse
section of those longitudinal siliceous bodies These are seen in fig. 1.
2. and 3. They have not only separately the forms of certain typographic
characters, but collectively give the regular lineal appearance of types
set in writing.
It is evident from the inspection of this fossil, that the sparry and
siliceous substances had been mixed together in a fluid state; and that
the crystallization of the sparry substance, which is rhombic, had
determined the regular structure of the quartz, at least in some
directions.
Thus, the siliceous substance is to be considered as included in the
spar, and as figured, according to the laws of crystallization proper
to the sparry ground; but the spar is also to be found included in the
quartz. It is not, indeed, always perfectly included or inclosed on all
sides; but this is sometimes the case, or it appears so in the section.
Fig. 5. 6. 7. 8. 9. and 10. are those cases magnified, and represent the
different figured quartz inclosing the feld-spar. In one of them, the
feld-spar, which is contained within the quartz, contains also a small
triangle of quartz, which it incloses. Now, it is not possible to
conceive any other way in which those two substances, quartz and
feld-spar, could be thus concreted, except by congelation from a fluid
state, in which they had been mixed.
There is one thing more to be observed with regard to this curious
species of granite. It is the different order or arrangement of the
crystallization or internal structure of the feld-spar ground, in two
contiguous parts of the same mass. This is to be perceived in the
polished surface of the stone, by means of the reflection of light.
There is a certain direction in which, viewing the stone, when the light
falls with a proper obliquity, we see a luminous reflection from the
internal parts of the stone. This arises from the reflecting surfaces
of the sparry structure or minute cracks, all turned in one direction,
consequently, giving that luminous appearance only in one point of view.
Now, all the parts of the stone in which the figured quartz is directed
in the same manner, or regularly placed in relation to each other,
present that shining appearance to the eye at one time, or in the same
point of direction. But there are parts of the mass, which, though
immediately contiguous and properly continuous, have a different
disposition of the figured quartz; and these two distinguished masses,
in the same surface of the polished stone, give to the eye their shining
appearance in very different directions. Fig. 3. shows two of those
figured and shining masses, in the same plane or polished surface.
It must be evident, that, as the crystallization of the sparry structure
is the figuring cause of the quartz bodies, there must be observed a
certain correspondency between those two things, the alinement (if I may
be allowed the expression) of the quartz, and the shining of the sparry
ground. It must also appear, that at the time of congelation of the
fluid spar, those two contiguous portions had been differently disposed
in the crystallization of their substance. This is an observation which
I have had frequent opportunities of making, with respect to masses of
calcareous spar.
Upon the whole, therefore, whether we shall consider granite as a
stratum or as an irregular mass, whether as a collection of several
materials, or as the separation of substances which had been mixed,
there is sufficient evidence of this body having been consolidated by
means of fusion, and in no other manner.
We are thus led to suppose, that the power of heat and operation
of fusion must have been employed in consolidating strata of loose
materials, which had been collected together and amassed at the bottom
of the ocean. It will, therefore, be proper to consider, what are the
appearances in consolidated strata that naturally should follow, on the
one hand, from fluidity having been, in this manner, introduced by means
of heat, and, on the other, from the interstices being filled by means
of solution; that so we may compare appearances with the one and other
of those two suppositions, in order to know that with which they may be
only found consistent.
The consolidation of strata with every different kind of substance was
found to be inconsistent with the supposition, that aqueous solution
had been the means employed for this purpose. This appearance, on the
contrary, is perfectly consistent with the idea, that the fluidity of
these bodies had been the effect of heat; for, whether we suppose the
introduction of foreign matter into the porous mass of a stratum for its
consolidation, or whether we shall suppose the materials of the mass
acquiring a degree of softness, by means of which, together with an
immense compression, the porous body might be rendered solid; the power
of heat, as the cause of fluidity and vapour, is equally proper and
perfectly competent. Here, therefore, appearances are as decidedly in
favour of the last supposition, as they had been inconsistent with the
first.
But if strata have been consolidated by means of aqueous solution, these
masses should be found precisely in the same state as when they were
originally deposited from the water. The perpendicular section of those
masses might show the compression of the bodies included in them, or of
which they are composed; but the horizontal section could not contain
any separation of the parts of the stratum from one another.
If, again, strata have been consolidated by means of heat, acting in
such a manner as to soften their substance, then, in cooling, they must
have formed rents or separations of their substance, by the unequal
degrees of contraction which the contiguous strata may have suffered.
Here is a most decisive mark by which the present question must be
determined.
There is not in nature any appearance more distinct than this of the
perpendicular fissures and separations in strata. These are generally
known to workmen by the terms of veins or backs and cutters; and there
is no consolidated stratum that wants these appearances. Here is,
therefore, a clear decision of the question, Whether it has been by
means of heat, or by means of aqueous solution, that collections of
loose bodies at the bottom of the sea have been consolidated into the
hardest rocks and most perfect marbles[12].
[Note 12: This subject is extremely interesting, both to the theory of
the earth, and to the science cf the mining art; I will now illustrate
that theory, with an authority which I received after giving this
dissertation to the Royal Society. It is in the second volume of M. de
Saussure's _voyages dans les Alpes_. Here I find proper examples for
illustrating that subject of mineralogy; and I am happy to have this
opportunity of giving the reasoning of a man of science upon the
subject, and the opinion of a person who is in every respect so well
qualified to judge upon a point of this kind.
The first example is of a marble in the Alps, (_voyages dans les
Alpes._) tom. 2. page 271.
"La pâte de ces brèches est tantôt blanche, tantôt grise, et les
fragmens qui y font renfermés font, les uns blancs, les autres gris,
d'autres roux, et presque toujours d'une couleur différente de celle de
la pâte qui les lit. Ils sont tous de nature calcaire; tels étaient au
moins tous ceux que j'ai pus observer; et ce qu'il-y-a de remarquable,
c'est qu'ils sont tous posés dans le sens des feuillets de la pierre; on
diroit en les voyant, qu'ils ont tous été comprimés et écrasés dans
le même sens. Cette même pierre est mêlée de mica, sur-tout dans les
interstices des couches et entre les fragmens et la pâte qui les réunit;
mais on ne voit point de mica dans les fragmens eux-mêmes. On trouve
aussi dans ces brèches des infiltrations de quartz. Cette pierre est
coupée par des fréquentes fissures perpendiculaires aux plans des
couches. On voit clairement que ces fentes out été formées par l'inégal
affaissement des couches, et non par une retraite spontanée: car les
morceaux ou fragmens étrangers sont tous partagés et coupés net par ces
fissures au lieu que dans les divisions naturelles des couches, ces
mêmes fragmens sont entiers et saillans au dehors de la surface. Les
noeuds de quartz et les divers crystaux, que renferment les roches
feuilletées, présentent le même phénomène, et l'on peut en tirer la même
conséquence; ils font partagés dans les fentes, et entiers dans les
séparations des couches."
He finds those particular strata in the other side of the mountain _col
de la Seigne_, and gives us the following observations:
"Plus bas on passe entre deux bancs de ces mêmes brèches, entre lesquels
sont interposées des couches d'ardoises noires et de grès feuilletés
micacés, dont la situation est la même.
"On retrouve encore ces brèches vers le has de la descente, au pied de
pyramides calcaires dont j'ai parlé plus haut. Je trouvai en 1774 de
très-jolis crystaux de roche qui s'étaient formés dans les fentes de
cette brèche. Il y avoit même un mélange de quartz et de mica qui
s'étoit moulé dans quelques-une de ces fentes. C'étoit donc une roche
semblable aux primitives, et pourtant d'une formation postérieure à
celle de la pierre calcaire. Et quel système pourroit nous persuader que
la nature ne puisse encore produire ce qu'elle a produit autrefois!"
M. de Saussure has here given us an example of a calcareous Braccia,
as he calls it, but which is rather a pudding stone, with veins or
contractions of the mass. He does not seem to understand these as
consequences of the consolidation of those strata; this, however, is
the only light in which these appearances may be explained, when those
bodies are thus divided without any other separation in the mass.
The second example is found in the vertical strata of those mountains
through which the Rhône has made its way in running from the great
valley of the _Vallais_ towards the lake of Geneva. (Chapitre xlviii.)
"C'est une espèce de pétrosilex gris, dur, sonore, un peu transparent,
qui se débite en feuillets minces parfaitement plans et réguliers. Ces
feuillets, ou plutôt ces couches, courent à 35 degrés du nord par est,
en montant du coté de l'ouest sous un angle de 80 degrés. Ces couches
sont coupées par des fentes qui leur sont à-peu-près perpendiculaires et
qui le sont aussi à l'horizon. Cette pierre s'emploie aux mêmes usage
que l'ardoise, mais elle est beaucoup plus forte et plus durable, parce
qu'elle est plus dure et moins accessible aux impressions de l'eau et de
l'air.
§ 1047. "Ces pétrosilex feuilletés changent peu-à-peu de nature, en
admettant dans les interstices de leurs feuillets des parties de
feldspath. Ils out alors l'apparence d'une roche feuilletée, quartzeuse
et micacée, (_quartzum fornacum W._). Mais cette apparence est
trompeuse; car on n'y trouve pas un atome de quartz: toutes les parties
blanches qui donnent du feu contre l'acier, font du feldspath; et les
parties grise écailleuses ne font point du mica, ce sont de lames minces
du pétrosilex dont j'ai déjà parlé."
Here is evidently what I would call petuntze strata, or porcelane stone,
that is, strata formed by the deposits of such materials as might come
from the _detritus_ of granite, arranged at the bottom of the sea, and
consolidated by heat in the mineral regions. We have precisely such
stratified masses in the Pentland hills near Edinburgh. I have also a
specimen of the same kind, brought from the East Indies, in which there
is the print of an organized body. I believe it to be of some coralline
or zoophite.
§ 1048. "Cette roche mélangée continue jusqu'à ce que le rocher
s'éloigne un peu du grand chemin. Là, ce rocher se présente coupé à
pic dans une grande étendue, et divisé par de grandes fentes obliques,
à-peu-près parallèles entr'elles. Ces fentes partagent la montagne en
grandes tranches de 50 à 60 pieds d'épaisseur, que de loin semblent être
des couches. Mais lorsqu'on s'en approche, on voit, par le tissu même
de la pierre feuilletée, que ses vraies couches font avec l'horizon des
angles de 70 à 75 degré, et que ces grandes divisions sont de vraies
fentes par lesquelles un grand nombre de couches consécutives sont
coupées presque perpendiculairement à leurs plans. Les masses de rocher,
comprises entre ces grandes fentes, sont encore divisées par d'autres
fentes plus petites, dont la plupart sont paralleles aux grandes,
d'autres leur sont obliques; mais toutes sont à très-peu-près
perpendiculaires aux plans des couchés dont la montagne est composée."
Here is a distinct view of that which may be found to take place in all
consolidated strata, whatever be the composition of the stratum; and
it is this appearance which is here maintained to be a physical
demonstration, that those strata had been consolidated by means of
heat softening their materials. In that case, those stratified
bodies, contracting in cooling, form veins and fissures traversing
perpendicularly their planes; and these veins are afterwards filled with
mineral substances. These are what I have here distinguished as the
_particular_ veins of mineral masses; things perfectly different from
proper mineral or metallic veins, which are more general, as belonging
to immense masses of those strata; and which had been formed, not from
the contraction, but from the disrupture of those masses, and by the
forcible injection of fluid mineral substances from below. Now these two
species of veins, the particular and the general, although occasionally
connected, must be in science carefully distinguished; in the one, we
see the means which had been employed for the consolidation of the
strata; in the other, we see that power by which the strata have been
raised from the bottom of the sea and placed in the atmosphere.]
Error never can be consistent, nor can truth fail of having support from
the accurate examination of every circumstance. It is not enough to
have found appearances decisive of the question, with regard to the
two suppositions which have been now considered, we may farther seek
confirmation of that supposition which has been found alone consistent
with appearances.
If it be by means of heat and fusion that strata have been consolidated,
then, in proportion to the degree of consolidation they have undergone
from their original state, they should, _caeteris paribus_, abound more
with separations in their mass. But this conclusion is found consistent
with appearances. A stratum of porous sand-stone does not abound so much
with veins and cutters as a similar stratum of marble, or even a
similar stratum of sand-stone that is more consolidated. In proportion,
therefore, as strata have been consolidated, they are in general
intersected with veins and cutters; and in proportion as strata are
deep in their perpendicular section, the veins are wide, and placed at
greater distances. In like manner, when strata are thin, the veins are
many, but proportionally narrow.
It is thus, upon chemical principles, to be demonstrated, That all the
solid strata of the globe have been condensed by means of heat, and
hardened from a state of fusion. But this proposition is equally to
be maintained from principles which are mechanical. The strata of the
globe, besides being formed of earths, are composed of sand, of gravel,
and fragments of hard bodies, all which may be considered as, in their
nature, simple; but these strata are also found composed of bodies which
are not simple, but are fragments of former strata, which had been
consolidated, and afterwards were broken and worn by attrition, so as
to be made gravel. Strata composed in this manner have been again
consolidated; and now the question is, By what means?
If strata composed of such various bodies had been consolidated, by any
manner of concretion, from the fluidity of a dissolution, the hard and
solid bodies must be found in their entire state, while the interstices
between those constituent parts of the stratum are filled up. No partial
fracture can be conceived as introduced into the middle of a solid mass
of hard matter, without having been communicated from the surrounding
parts. But such partial separations are found in the middle of those
hard and solid masses; therefore, this compound body must have been
consolidated by other means than that of concretion from a state of a
solution.
The Spanish marble already described, as well as many consolidated
strata of siliceous gravel, of which I have specimens, afford the
clearest evidence of this fact. These hard bodies are perfectly united
together, in forming the most solid mass; the contiguous parts of some
of the rounded fragments are interlaced together, as has already been
observed; and there are partial shrinkings of the mass forming veins,
traversing several fragments, but perfectly filled with the sparry
substance of the mass, and sometimes with parts of the stone distinctly
floating in the transparent body of spar. Now, there is not, besides
heat or fusion, any known power in nature by which these effects might
be produced. But such effects are general to all consolidated masses,
although not always so well illustrated in a cabinet specimen.
Thus we have discovered a truth that is confirmed by every appearance,
so far as the nature of the subject now examined admits. We now return
to the general operation, of forming continents of those materials which
had been deposited at the bottom of the sea.
SECTION III.
Investigation of the Natural Operations employed in the Production of
Land above the Surface of the Sea.
We seek to know that operation by means of which masses of loose
materials, collected at the bottom of the sea, were raised above its
surface, and transformed into solid land.
We have found, that there is not in this globe (as a planet revolving
in the solar system) any power or motion adapted to the purpose now in
view; nor, were there such a power, could a mass of simply collected
materials have continued any considerable time to resist the waves and
currents natural to the sea, but must have been quickly carried away,
and again deposited at the bottom of the ocean. But we have found, that
there had been operations, natural to the bowels of this earth; by which
those loose and unconnected materials have been cemented together, and
consolidated into masses of great strength and hardness; those bodies
are thus enabled to resist the force of waves and currents, and to
preserve themselves, for a sufficient time, in their proper shape and
place, as land above the general surface of the ocean.
We now desire to know, how far those internal operations of the globe,
by which solidity and stability are procured to the beds of loose
materials, may have been also employed in raising up a continent of
land, to remain above the surface of the sea.
There is nothing so proper for the erection of land above the level of
the ocean, as an expansive power of sufficient force, applied directly
under materials in the bottom of the sea, under a mass that is proper
for the formation of land when thus erected. The question is not, how
such a power may be procured; such a power has probably been employed.
If, therefore, such a power should be consistent with that which we
found had actually been employed in preparing the erected mass; or,
if such a power is to be reasonably concluded as accompanying those
operations which we have found natural to the globe, and situated in the
very place where this expansive power appears to be required, we should
thus be led to perceive, in the natural operations of the globe, a power
as efficacious for the elevation of what had been at the bottom of the
sea into the place of land, as it is perfect for the preparation of
those materials to serve the purpose of their elevation.
In opposition to this conclusion, it will not be allowed to allege; that
we are ignorant how such a power might be exerted under the bottom of
the ocean; for, the present question is not, what had been the cause of
heat, which has appeared to have been produced in that place, but if
this power of heat, which has certainly been exerted at the bottom of
the ocean for consolidating strata, had been employed also for another
purpose, that is, for raising those strata into the place of land.
We may, perhaps, account for the elevation of land, by the same cause
with that of the consolidation of strata, already investigated, without
explaining the means employed by nature in procuring the power of heat,
or showing from what general source of action this particular power had
been derived; but, by finding in subterranean heat a cause for any other
change, besides the consolidation of porous or incoherent bodies, we
shall generalise a fact, or extend our knowledge in the explanation of
natural appearances.
The power of heat for the expansion of bodies, is, so far as we know,
unlimited; but, by the expansion of bodies placed under the strata at
the bottom of the sea, the elevation of those strata may be effected;
and the question now to be resolved regards the actual exertion of
this power of expansion. How far it is to be concluded as having been
employed in the production of this earth above the level of the sea.
Before attempting to resolve that question, it may be proper to observe,
there has been exerted an extreme degree of heat below the strata formed
at the bottom of the sea; and this is precisely the action of a power
required for the elevation of those heated bodies into a higher place.
Therefore, if there is no other way in which we may conceive this event
to have been brought about, consistent with the present state of things,
or what actually appears, we shall have a right to conclude, that such
had been the order of procedure in natural things, and that the
strata formed at the bottom of the sea had been elevated, as well as
consolidated, by means of subterraneous heat.
The consolidation of strata by means of fusion or the power of heat, has
been concluded from the examination of nature, and from finding, that
the present state of things is inconsistent with any other supposition.
Now, again, we are considering the only power that may be conceived as
capable of elevating strata from the bottom of the sea, and placing such
a mass above the surface of the water. It is a truth unquestionable,
that what had been originally at the bottom of the sea, is at present
the highest of our land. In explaining this appearance, therefore, no
other alternative is left, but either to suppose strata elevated by the
power of heat above the level of the present sea, or the surface of the
ocean reduced many miles below the height at which it had subsisted
during the collection and induration of the land which we inhabit.
Now, if, on the one hand, we are to suppose no general power of
subterraneous fire or heat, we leave to our theory no means for the
retreat of the sea, or the lowering of its surface; if, on the other
hand, we are to allow the general power of subterraneous heat, we cannot
have much difficulty in supposing, either the surface of the sea to have
subsided, or the bottom of the ocean, in certain parts, to have been
raised by a subterranean power above the level of its surface, according
as appearances shall be found to require the one or other of those
conclusions. Here, therefore, we are again remitted to the history of
nature, in order to find matter of fact by which this question may be
properly decided.
If the present land had been discovered by the subsiding of the waters,
there has not been a former land, from whence materials had been
procured for the construction of the present, when at the bottom of the
sea; for, there is no vestige remaining of that land, the whole land of
the present earth having been formed evidently at the bottom of the sea.
Neither could the natural productions of the sea have been accumulated,
in the shape in which we now find them, on the surface of this earth;
for, How should the Alps and Andes have been formed within the sea
from the natural productions of the water? Consequently, this is a
supposition inconsistent with every natural appearance.
The supposition, therefore, of the subsidence of the former ocean,
for the purpose of discovering the present land, is beset with more
difficulty than the simple erection of the bottom of the former ocean;
for, _first_, There is a place to provide for the retirement of the
waters of the ocean; and, _2dly_, There is required a work of equal
magnitude; this is, the swallowing up of that former continent, which
had procured the materials of the present land.
On the one hand, the subsiding of the surface of the ocean would but
make the former land appear the higher; and, on the other, the sinking
the body of the former land into the solid globe, so as to swallow up
the greater part of the ocean after it, if not a natural impossibility,
would be at least a superfluous exertion of the power of nature. Such an
operation as this would discover as little wisdom in the end elected, as
in the means appropriated to that end; for, if the land be not wasted
and worn away in the natural operations of the globe, Why make such a
convulsion in the world in order to renew the land? If, again, the land
naturally decays, Why employ so extraordinary a power, in order to hide
a former continent of land, and puzzle man?
Let us now consider how far the other proposition, of strata being
elevated by the power of heat above the level of the sea, may be
confirmed from the examination of natural appearances.
The strata formed at the bottom of the ocean are necessarily horizontal
in their position, or nearly so, and continuous in their horizontal
direction or extent. They may change, and gradually assume the nature of
each other, so far as concerns the materials of which they are formed;
but there cannot be any sudden change, fracture, or displacement,
naturally in the body of a stratum. But, if these strata are cemented by
the heat of fusion, and erected with an expansive power acting below,
we may expect to find every species of fracture, dislocation, and
contortion, in those bodies, and every degree of departure from a
horizontal towards a vertical position.
The strata of the globe are actually found in every possible position:
For, from horizontal, they are frequently found vertical; from
continuous, they are broken and separated in every possible direction;
and, from a plane, they are bent and doubled. It is impossible that they
could have originally been formed, by the known laws of nature, in their
present state and position; and the power that has been necessarily
required for their change, has not been inferior to that which might
have been required for their elevation from the place in which they had
been formed.
In this cafe, natural appearances are not anomalous. They are, indeed,
infinitely various, as they ought to be, according to the rule; but all
those varieties in appearances conspire to prove one general truth, viz.
That all which we see had been originally composed according to certain
principles, established in the constitution of the terraqueous globe;
and that those regular compositions had been afterwards greatly changed
by the operations of another power, which had introduced apparent
confusion among things first formed in order and by rule.
It is concerning the operation of this second power that we are now
inquiring; and here the apparent irregularity and disorder of the
mineral regions are as instructive, with regard to what had been
transacted in a former period of time, as the order and regularity of
those same regions are conclusive, in relation to the place in which a
former state of things had produced that which, in its changed state, we
now perceive.
We are now to conclude, that the land on which we dwell had been
elevated from a lower situation by the same agent which had been
employed in consolidating the strata, in giving them stability, and
preparing them for the purpose of the living world. This agent is matter
actuated by extreme heat, and expanded with amazing force.
If this has been the case, it will be reasonable to expect, that some of
the expanded matter might be found condensed in the bodies which have
been heated by that igneous vapour; and that matter, foreign to the
strata, may have been thus introduced into the fractures and separations
of those indurated masses.
We have but to open our eyes to be convinced of this truth. Look into
the sources of our mineral treasures; ask the miner, from whence has
come the metal into his vein? Not from the earth or air above,--not from
the strata which the vein traverses; these do not contain one atom of
the minerals now considered. There is but one place from whence these
minerals may have come; this is the bowels of the earth, the place of
power and expansion, the place from whence must have proceeded that
intense heat by which loose materials have been consolidated into rocks,
as well as that enormous force by which the regular strata have been
broken and displaced.
Our attention is here peculiarly called upon, where we have the
opportunity of examining those mineral bodies, which have immediately
proceeded from the unknown region, that place of power and energy which
we want to explore; for, if such is the system of the earth, that
materials are first deposited at the bottom of the ocean, there to be
prepared in a certain manner, in order to acquire solidity, and then to
be elevated into the proper place of land, these mineral veins, which
contain matter absolutely foreign to the surface of the earth, afford
the most authentic information with regard to the operations which we
want to understand. It is these veins which we are to consider as,
in some measure, the continuation of that mineral region, which lies
necessarily out of all possible reach of our examination. It is,
therefore, peculiarly interesting to know the state in which things
are to be found in this place, which may be considered as intermediate
between the solid land, upon the one hand, and the unknown regions of
the earth, upon the other.
We are now to examine those mineral veins; and these may be considered,
first, in relation to their form, independent of their substance or
particular contents; and, secondly, in relation to the contained bodies,
independent of their form.
In examining consolidated strata, we remarked veins and cutters as a
proof of the means by which those bodies had been consolidated. In that
case, the formation of these veins is a regulated process, determined
by the degree of fusion, and the circumstances of condensation or
refrigeration. In respect of these, the mineral veins now to be examined
are anomalous. They are; but we know not why or how. We see the effect;
but, in that effect, we do not see the cause. We can say, negatively,
that the cause of mineral veins is not that by which the veins and
fissures of consolidated strata have been formed; consequently, that
it is not the measured contraction and regulated condensation of the
consolidated land which has formed those general mineral veins; however,
veins, similar in many respects, have been formed by the cooperation of
this cause.
Having thus taken a view of the evident distinction between the veins or
contractions that are particular to the consolidated body in which they
are found, and those more general veins which are not limited to that
cause, we may now consider what is general in the subject, or what is
universal in these effects of which we wish to investigate the cause.
The event of highest generalization or universality, in the form of
those mineral veins, is fracture and dislocation. It is not, like that
of the veins of strata, simple separation and measured contraction; it
is violent fracture and unlimited dislocation. In the one case, the
forming cause is in the body which is separated; for, after the body had
been actuated by heat, it is by the reaction of the proper matter of the
body, that the chasm which constitutes the vein is formed. In the other
case, again, the cause is extrinsic in relation to the body in which the
chasm is formed. There has been the most violent fracture and divulsion;
but the cause is still to seek; and it appears not in the vein; for it
is not every fracture and dislocation of the solid body of our earth, in
which minerals, or the proper substances of mineral veins, are found.
We are now examining matter of fact, real effects, from whence we would
investigate the nature of certain events which do not now appear. Of
these, two kinds occur; one which has relation to the hardness and
solidity, or the natural constitution of the body; the other, to its
shape or local situation. The first has been already considered; the
last is now the subject of inquiry.
But, in examining those natural appearances, we find two different kinds
of veins; the one necessarily connected with the consolidating cause;
the other with that cause of which we now particularly inquire. For,
in those great mineral veins, violent fracture and dislocation is the
principle; but there is no other principle upon which strata, or masses
formed at the bottom of the sea, can be placed at a height above its
surface. Hence, in those two different operations, of forming mineral
veins, and erecting strata from a lower to a higher place, the principle
is the same; for, neither can be done without violent fracture and
dislocation.
We now only want to know, how far it is by the same power, as well as
upon the same principle, that these two operations have been made.
An expansive force, acting from below, is the power most proper for
erecting masses; but whether it is a power of the same nature with that
which has been employed in forming mineral veins, will best appear in
knowing the nature of their contents. These, therefore, may be now
considered.
Every species of fracture, and every degree of dislocation and
contortion, may be perceived in the form of mineral veins; and there is
no other general principle to be observed in examining their form. But,
in examining their contents, some other principle may appear, so far as,
to the dislocating power or force, there may be superadded matter, by
which something in relation to the nature of the power may be known.
If, for example, a tree or a rock shall be found simply split asunder,
although there be no doubt with regard to some power having been applied
in order to produce the effect, yet we are left merely to conjecture at
the power. But when wedges of wood or iron, or frozen water, should be
found lodged in the cleft, we might be enabled, from this appearance, to
form a certain judgment with regard to the nature of the power which
had been applied. This is the case with mineral veins. We find them
containing matter, which indicates a cause; and every information in
this case is interesting to the theory.
The substances contained in mineral veins are precisely the same with
those which, in the former section, we have considered as being made
instrumental in the consolidation of strata; and they are found mixed
and concreted in every manner possible.
But, besides this evidence for the exertion of extreme heat, in that
process by which those veins were filled, there is another important
observation to be gathered from the inspection of this subject. There
appears to have been a great mechanical power employed in the filling of
these veins, as well as that necessarily required in making the first
fracture and divulsion.
This appears from the order of the contents, or filling of these veins,
which is a thing often observed to be various and successive. But what
it is chiefly now in view to illustrate, is that immense force which is
manifested in the fracture and dispersion of the solid contents which
had formerly filled those veins. Here we find fragments of rock and spar
floating in the body of a vein filled with metallic substances; there,
again, we see the various fragments of metallic masses floating in the
sparry and siliceous contents.
One thing is demonstrable from the inspection of the veins and their
contents; this is, the successive irruptions of those fluid substances
breaking the solid bodies which they meet, and floating those fragments
of the broken bodies in the vein. It is very common to see three
successive series of those operations; and all this may be perceived in
a small fragment of stone, which a man of science may examine in his
closet, often better than descending to the mine, where all the examples
are found on an enlarged scale.
Let us now consider what power would be required to force up, from the
most unfathomable depth of the ocean, to the Andes or the Alps, a column
of fluid metal and of stone. This power cannot be much less than that
required to elevate the highest land upon the globe. Whether, therefore,
we shall consider the general veins as having been filled by mineral
steams, or by fluid minerals, an elevating power of immense force is
still required, in order to form as well as fill those veins. But such a
power acting under the consolidated masses at the bottom of the sea, is
the only natural means for making those masses land.
If such have been the operations that are necessary for the production
of this land; and if these operations are natural to the globe of this
earth, as being the effect of wisdom in its contrivance, we shall
have reason to look for the actual manifestation of this truth in the
phaenomena of nature, or those appearances which more immediately
discover the actual cause in the perceived effect.
To see the evidence of marble, a body that is solid, having been formed
of loose materials collected at the bottom of the sea, is not always
easy, although it may be made abundantly plain; and to be convinced that
this calcareous stone, which calcines so easily in our fires, should
have been brought into fusion by subterraneous heat, without suffering
calcination, must require a chain of reasoning which every one is not
able to attain[13]. But when fire bursts forth from the bottom of the
sea, and when the land is heaved up and down, so as to demolish cities
in an instant, and split asunder rocks and solid mountains, there
is nobody but must see in this a power, which may be sufficient to
accomplish every view of nature in erecting land, as it is situated in
the place most advantageous for that purpose.
[Note 13: Mr le Chevalier de Dolomieu, in considering the different
effects of heat, has made the following observation; Journal de
Physique, Mai 1792.
"Je dis _le feu tel que nous l'employons_ pour distinguer le feu naturel
des volcans, du feu de nos fourneaux et de celui de nos chalumeaux. Nous
sommes obligés de donner une grande activité à son action pour suppléer
et au volume qui ne seroit pas à notre disposition et au tems que nous
sommes forcés de ménager, et cette manière d'appliquer une chaleur
très-active, communique le mouvement et le désordre jusques dans les
molécules constituantes. Agrégation et composition, tout est troublé.
Dans les volcans la grand masse du feu supplée à son intensité, le
tems remplace son activité, de manière qu'il tourmente moins les corps
fournis à son action; il ménage leur composition en relâchant leur
agrégation, et les pierres qui eut été rendues fluides par l'embrasement
volcanique peuvent reprendre leur état primitif; la plupart des
substances qu'un feu plus actif auroit expulsées y restent encore. Voilà
pourquoi les laves ressemblent tellement aux pierres naturelles des
espèces analogues, qu'elles ne peuvent en être distinguées; voilà
également pourquoi les verres volcaniques eux-même renferment encore des
substances élastiques qui les font boursoufler lorsque nous les fondons
de nouveau, et pourquoi ces verres blanchissent aussi, pour lors, par
la dissipation, d'une substance grasse qui a résisté à la chaleur des
volcans, et que volatilise la chaleur par laquelle nous obtenons leur
second fusion."
No doubt, the long application of heat may produce changes in bodies
very different from those which are occasioned by the sudden application
of a more intense heat; but still there must be sufficient intensity in
that power, so as to cause fluidity, without which no chemical change
can be produced in bodies. The essential difference, however, between
the natural heat of the mineral regions, and that which we excite upon
the surface of the earth, consists in this; that nature applies heat
under circumstances which we are not able to imitate, that is, under
such compression as shall prevent the decomposition of the constituent
substances, by the separation of the more volatile from the more fixed
parts. This is a circumstance which, so far as I know, no chemist
or naturalist has hitherto considered; and it is that by which the
operations of the mineral regions must certainly be explained. Without
attending to this great principle in the mineralizing operations
of subterraneous fire, it is impossible to conceive the fusion and
concretion of those various bodies, which we examine when brought up to
the surface of the earth.]
The only question, therefore, which it concerns us to decide at present,
is, Whether those operations of extreme heat, and violent mechanic
force, be only in the system as a matter of accident; or if, on the
contrary, they are operations natural to the globe, and necessary in the
production of such land as this which we inhabit? The answer to this is
plain: These operations of the globe remain at present with undiminished
activity, or in the fullness of their power.
A stream of melted lava flows from the sides of Mount Aetna. Here is a
column of weighty matter raised from a great depth below, to an immense
height above, the level of the sea, and rocks of an enormous size
are projected from its orifice some miles into the air. Every one
acknowledges that here is the liquefying power and expansive force of
subterranean fire, or violent heat. But, that Sicily itself had been
raised from the bottom of the ocean, and that the marble called Sicilian
Jasper, had its solidity upon the same principle with the lava, would
stumble many a naturalist to acknowledge. Nevertheless, I have in my
possession a table of this marble, from which it is demonstrable, that
this calcareous stone had flowed, and been in such a state of fusion and
fluidity as lava.
Here is a comparison formed of two mineral substances, to which it is of
the highest importance to attend. The solidity and present state of the
one of these is commonly thought to be the operation of fire; of the
other, again, it is thought to be that of water. This, however, is not
the case. The immediate state and condition of both these bodies is now
to be considered as equally the effect of fire or heat. The reason of
our forming such a different judgment with regard to these two subjects
is this; we see, in the one case, the more immediate connection of the
cause and the effect, while, in the other, we have only the effects from
whence we are in science to investigate the cause.
But, if it were necessary always to see this immediate connection, in
order to acknowledge the operation of a power which, at present, is
extinguished in the effect, we should lose the benefit of science, or
general principles, from whence particulars may be deduced, and we
should be able to reason no better than the brute. Man is made for
science; he reasons from effects to causes, and from causes to effects;
but he does not always reason without error. In reasoning, therefore,
from appearances which are particular, care must be taken how we
generalise; we should be cautious not to attribute to nature, laws which
may perhaps be only of our own invention.
The immediate question now before us is not, If the subterraneous fire,
or elevating power, which we perceive sometimes as operating with such
energy, be the consolidating cause of strata formed at the bottom of the
sea; nor, if that power be the means of making land appear above the
general surface of the water? for, though this be the end we want to
arrive at ultimately, the question at present in agitation respects the
laws of nature, or the generality of particular appearances.
Has the globe within it such an active power as fits it for the
renovation of that part of its constitution which may be subject to
decay? Are those powerful operations of fire, or subterraneous heat,
which so often have filled us with terror and astonishment, to be
considered as having always been? Are they to be concluded as proper to
every part upon the globe, and as continual in the system of this earth?
If these points in question shall be decided in the affirmative, we can
be at no loss in ascertaining the power which has consolidated strata,
nor in explaining the present situation of those bodies, which had their
origin at the bottom of the sea. This, therefore, should be the object
of our pursuit; and in order to have demonstration in a case of physical
inquiry, we must again have recourse to the book of nature.
The general tendency of heat is to produce fluidity and softness; as
that of cold is, on the contrary, to harden soft and fluid bodies. But
this softening power of heat is not uniform in its nature; it is made to
act with very different effect, according to the nature of the substance
to which it is applied. We are but limited in the art of increasing the
heat or the cold of bodies; we find, however, extreme difference in
their substances with respect to fusibility.
A fusible substance, or mineral composition in a fluid state, is emitted
from those places of the earth at which subterraneous fire and expansive
force are manifested in those eruptive operations. In examining these
emitted bodies, men of science find a character for such productions, in
generalising the substance, and understanding the natural constitution
of those bodies. It is in this manner that such a person, finding a
piece of lava in any place of the earth, says with certainty, Here is a
stone which had congealed from a melted state.
Having thus found a distinguishing character for those fused substances
called, in general, Lavas, and having the most visible marks for that
which had been actually a volcano, naturalists, in examining different
countries, have discovered the most undoubted proofs of many ancient
volcanos, which had not been before suspected. Thus, volcanos will
appear to be not a matter of accident, or as only happening in a
particular place, they are general to the globe, so far as there is
no place upon the earth that may not have an eruption of this kind;
although it is by no means necessary for every place to have had those
eruptions.
Volcanos are natural to the globe, as general operations; but we are
not to consider nature as having a burning mountain for an end in her
intention, or as a principal purpose in the general system of this
world. The end of nature in placing an internal fire or power of heat,
and a force of irresistible expansion, in the body of this earth, is to
consolidate the sediment collected at the bottom of the sea, and to form
thereof a mass of permanent land above the level of the ocean, for the
purpose of maintaining plants and animals. The power appointed for this
purpose is, as on all other occasions, where the operation is important,
and where there is any danger of a shortcoming, wisely provided
in abundance; and there are contrived means for disposing of the
redundancy. These, in the present case, are our volcanos.
A volcano is not made on purpose to frighten superstitious people
into fits of piety and devotion, nor to overwhelm devoted cities with
destruction; a volcano should be considered as a spiracle to the
subterranean furnace, in order to prevent the unnecessary elevation of
land, and fatal effects of earthquakes; and we may rest assured, that
they, in general, wisely answer the end of their intention, without
being in themselves an end, for which nature had exerted such amazing
power and excellent contrivance.
Let us take a view of the most elevated places of the earth; if the
present theory is just, it is there that we should find volcanos. But is
not this the case? There are volcanos in the Andes; and round the Alps
we find many volcanos, which are in France upon the one side, and in
Germany upon the other, as well as upon the Italian side, where Vesuvius
still continues to exhibit violent eruptions.
It is not meant to allege, that it is only upon the summit of a
continent volcanos should appear. Subterraneous fire has sometimes made
its appearance in bursting from the bottom of the sea. But, even in
this last case, land was raised from the bottom of the sea, before the
eruption made its exit into the atmosphere. It must also be evident,
that, in this case of the new island near Santorini, had the expansive
power been retained, instead of being discharged, much more land might
have been raised above the level of the ocean.
Now, the eruption of that elastic force through the bottom of the sea,
may be considered as a waste of power in the operations of the globe,
where the elevation of indurated strata is an object in the exertion of
that power; whereas, in the centre of a continent sufficiently elevated
above the level of the sea, the eruption of that fiery vapour calculated
to elevate the land, while it may occasionally destroy the habitations
of a few, provides for the security and quiet possession of the many.
In order to see the wisdom of this contrivance, let us consider the
two extreme places at which this eruption of ignited matter may be
performed. These are, on the one hand, within a continent of land, and,
on the other, at the bottom of the ocean. In the one case, the free
eruption of the expanding power should be permitted; because the purpose
for which it had been calculated to exist has been accomplished. In
the other, again, the free eruption of that powerful matter should be
repressed; because there is reserved for that power much of another
operation in that place. But, according to the wise constitution of
things, this must necessarily happen. The eruption of the fiery
vapour from volcanos on the continent or land, is interrupted only
occasionally, by the melted bodies flowing in the subterraneous
chimney; whereas, at the bottom of the ocean, the contact of the water
necessarily tends to close the orifice, by accumulating condensed matter
upon the weakest place.
If this be a just theory of the natural operations of the globe, we
shall have reason to expect, that great quantities of this melted
matter, or fusible substance, may be found in form of lava, among the
strata of the earth, where there are no visible marks of any volcano, or
burning mountain, having existed. Here, therefore, is an important point
to be determined; for, if it shall appear that much of this melted
matter, analogous to lava, has been forced to flow among the strata
which had been formed at the bottom of the sea, and now are found
forming dry land above its surface, it will be allowed, that we have
discovered the secret operations of nature concocting future land, as
well as those by which the present habitable earth had been produced
from the bottom of the abyss. Here, therefore, we shall at present rest
the argument, with endeavouring to show that such is actually the case.
It appears from Cronstedt's Mineralogy, that the rock-stone, called trap
by the Swedes, the amygdaloides and the schwarts-stein of the Germans,
are the same with the whin-stone of this country. This is also fully
confirmed by specimens from Sweden, sent me by my friend Dr Gahn.
Whatever, therefore, shall be ascertained with regard to our whin-stone,
may be so far generalized or extended to the countries of Norway,
Sweden, and Germany.
The whin-stone of Scotland is also the same with the toad-stone of
Derbyshire, which is of the amygdaloides species; it is also the same
with the flagstone of the south of Staffordshire, which is a simple
whin-stone, or perfect trap. England, therefore, must be included in
this great space of land, the mineral operations of which we explore;
and also Ireland, of which the Giant's Causeway, and many others, are
sufficient proof.
In the south of Scotland, there is a ridge of hills, which extends
from the west side of the island in Galloway to the east side in
Berwickshire, composed of granite, of schistus, and of siliceous strata.
The Grampians on the north, again, form another range of mountains of
the same kind; and between these two great fields of broken, tumbled,
and distorted strata, there lies a field of lesser hardness and
consolidation, in general; but a field in which there is a great
manifestation of subterraneous fire, and of exerted force.
The strata in this space consist, in general, of sand-stone, coal,
lime-stone or marble, iron-stone, and marl or argillaceous strata, with
strata of analogous bodies, and the various compositions of these. But
what is to the present purpose is this, that, through all this space,
there are interspersed immense quantities of whinstone; a body which is
to be distinguished as very different from lava; and now the disposition
of this whin-stone is to be considered.
Sometimes it is found in an irregular mass or mountain, as Mr Cronstedt
has properly observed; but he has also said, that this is not the case
in general. His words are: "It is oftener found in form of veins in
mountains of another kind, running commonly in a serpentine manner,
contrary or across to the direction of the rock itself."
The origin of this form, in which the trap or whin-stone appears, is
most evident to inspection, when we consider that this solid body had
been in a fluid state, and introduced, in that state, among strata,
which preserved their proper form. The strata appear to have been
broken, and the two correspondent parts of those strata are separated to
admit the flowing mass of whin-stone.
A fine example of this kind may be seen upon the south side of the
Earn, on the road to Crief. It is twenty-four yards wide, stands
perpendicular, and appears many feet above the surface of the ground. It
runs from that eastward, and would seem to be the same with that which
crosses the river Tay, in forming Campsy-lin above Stanley, as a lesser
one of the same kind does below it. I have seen it at Lednoc upon the
Ammon, where it forms a cascade in that river, about five or six
miles west of Campsy-lin. It appears to run from the Tay east through
Strathmore, so that it may be considered as having been traced for
twenty or thirty miles, and westwards to Drummond castle, perhaps much
farther.
Two small veins of the same kind, only two or three feet wide, may be
seen in the bed of the Water of Leith, traversing the horizontal strata,
the one is above St Bernard's well, the other immediately below it. But,
more particularly, in the shire of Ayr, to the north of Irvine, there
are to be seen upon the coast, between that and Scarmorly, in the space
of about twenty miles, more than twenty or thirty such dykes (as they
are called) of whin-stone. Some of them are of a great thickness; and,
in some places, there is perceived a short one, running at right angles,
and communicating with other two that run parallel.
There is in this country, and in Derbyshire[14], another regular
appearance of this stone, which Cronstedt has not mentioned. In this
case, the strata are not broken in order to have the whin-stone
introduced, they are separated, and the whin-stone is interjected in
form of strata, having various degrees of regularity, and being of
different thickness. On the south side of Edinburgh, I have seen, in
little more than the space of a mile from east to west, nine or ten
masses of whin-stone interjected among the strata. These masses of
whin-stone are from three or four to an hundred feet thick, running
parallel in planes inclined to the horizon, and forming with it an angle
of about twenty or thirty degrees, as may be seen at all times in the
hill of Salisbury Craggs.
[Note 14: See Mr Whitehurst's Theory of the Earth.]
Having thus described these masses, which have flowed by means of
heat among the strata of the globe, strata which had been formed by
subsidence at the bottom of the sea, it will now be proper to examine
the difference that subsists between these subterraneous lavas, as they
may be termed, and the analogous bodies which are proper lavas, in
having issued out of a volcano.[15]
[Note 15: The Chevalier de Dolomieu, in his accurate examination of
Aetna and the Lipari islands, has very well observed the distinction of
these two different species of lavas; but without seeming to know the
principle upon which this essential difference depends. No bias of
system, therefore, can here be supposed as perverting the Chevalier's
view, in taking those observations; and these are interesting to the
present theory, as corresponding perfectly with the facts from whence it
has been formed. It will be proper to give the account of these in his
own words.
La zéolite est très-commune dans certains laves de l'Ethna; il seroit
peut-être possible d'y en rencontrer des morceaux aussi gros que ceux
que fournit l'isle de Ferroé. Quoique cette substance semble ici
appartenir aux laves, je ne dirai cependant point que toutes les
zéolites soient volcaniques, ou unies à des matières volcaniques; celles
que l'on trouve en Allemagne sont, dit-on, dans des circonstances
différentes; mais je doit annoncer que je n'ai trouvé cette substance en
Sicile, que dans les seules laves qui évidemment ont coulé dans la mer,
et qui out été recouvertes par ses eaux. La zéolite des laves n'est
point une déjection volcanique, ni une production du feu, ni même un
matière que les laves aient enveloppée lorsqu'elles étoient fluides;
elle est le résultat d'une opération et d'une combinaison postérieure,
auxquelles les eaux de la mer ont concouru. Les laves qui n'ont pas été
submergées, n'en contiennent jamais. J'ai trouvé ces observations si
constantes, que par-tout où je rencontrois de la zéolite, j'étois sûr
de trouver d'autres preuves de submersion, et partout où je voyois des
laves recouvertes des dépôts de l'eau, j'étois sûr de trouver de la
zéolite, et un de ces faits m'a toujours indiqué l'autre. Je me suis
servi avec succès de cette observation pour diriger mes recherches, et
pour connoître l'antiquité des laves. _Minéralogie de Volcans, par
M. Faujas de Saint-Fond_. Here would appear to be the distinction of
subterraneous lava, in which zeolite and calcareous spar may be found,
and that which has flowed from a volcano, in which neither of these are
ever observed.]
There can be no doubt that these two different species of bodies have
had the same origin, and that they are composed of the same materials
nearly; but from the different circumstances Of their production, there
is formed a character to these bodies, by which, they may be perfectly
distinguished. The difference of those circumstances consists in this;
the one has been emitted to the atmosphere in its fluid state the other
only came to be exposed to the light in a long course of time, after it
had congealed under the compression of an immense load of earth, and
after certain operations, proper to the mineral regions, had been
exercised upon the indurated mass. This is the cause of the difference
between those erupted lavas, and our whin-stone, toad-stone, and the
Swedish trap, which may be termed subterraneous lava. The visible
effects of those different operations may now be mentioned.
In the erupted lavas, those substances which are subject to calcine and
vitrify in our fires, suffer similar changes, when delivered from a
compression which had rendered them fixed, though in an extremely heated
state. Thus, a lava in which there is much calcareous spar, when it
comes to be exposed to the atmosphere, or delivered from the compressing
force of its confinement, effervesces by the explosion of its fixed
air; the calcareous earth, at the same time, vitrifies with the other
substances. Hence such violent ebullition in volcanos, and hence the
emission of so much pumice-stone and ashes, which are of the same
nature.
In the body of our whin-stone, on the contrary, there is no mark of
calcination or vitrification. We frequently find in it much calcareous
spar, or the _terra calcarea aerata_, which had been in a melted state
by heat, and had been crystallized by congelation into a sparry form.
Such is the _lapis amygdaloides_, and many of our whin-stone rocks,
which contain pebbles crystallized and variously figured, both
calcareous, siliceous, and of a mixture in which both these substances
form distinct parts. The specimens of this kind, which I have from the
whin-stone or porphyry rock of the Calton-hill, exhibit every species
of mineral operation, in forming jasper, figured agate, and marble; and
they demonstrate, that this had been performed by heat or fusion.
I do not mean to say, that this demonstration is direct; it is
conditional, and proceeds upon the supposition, that the basaltic or
porphyry rock, in which those specimens are found, is a body which had
been in a melted state. Now, this is a supposition for which I have
abundance of evidence, were it required; but naturalists are now
sufficiently disposed to admit that proposition; they even draw
conclusions from this fact, which, I think, they are not sufficiently
warranted in doing; that is, from this appearance, they infer the former
existence of volcanos in those places. For my part, though I have made
the most strict examination, I never saw any vestige of such an event.
That there are, in other countries, evident marks of volcanos which
have been long extinguished, is unquestionably true; but naturalists,
imagining that there are no other marks of subterraneous fire and
fusion, except in the production of a lava, attribute to a volcano, as
a cause, these effects, which only indicate the exertion of that power
which might have been the cause of a volcano.
If the theory now given be just, a rock of marble is no less a mark
of subterraneous fire and fusion, than that of the basaltes; and the
flowing of basaltic streams among strata broken and displaced, affords
the most satisfactory evidence of those operations by which the body of
our land had been elevated above the surface of the sea; but it gives no
proof that the eruptive force of mineral vapours had been discharged in
a burning mountain. Now, this discharge is essential in the proper idea
of a volcano.
Besides this internal mark of an unerupted lava in the substance of the
stone or body of the flowing mass, there are others which belong to it
in common with all other mineral strata, consolidated by subterraneous
fire, and changed from the place of their original formation; this is,
the being broken and dislocated, and having veins of foreign matter
formed in their separations and contractions.
If these are mineral operations, proper to the lower regions of the
earth, and exerted upon bodies under immense compression, such things
will be sometimes found in the unerupted lavas, as well as in the
contiguous bodies with which they are associated. If, on the contrary,
these are operations proper to the surface of the earth, where the
dissolving power of water and air take place, and where certain
stalactical and ferruginous concretions are produced by these means;
then, in erupted lavas, we should find mineral concretions, which
concretions should be denied to bodies which had been consolidated at
the bottom of the sea; that is to say, where, without the operation of
subterraneous fire, no changes of that kind could have taken place, as
has already been observed. But in the unerupted species of lava, that
is to say, in our whin-stone, every species of mineral appearance is
occasionally to be found. Let those who have the opportunity to examine,
say, what arc to be found in proper lavas, that is, those of the erupted
kind. Sir William Hamilton informed me, when I showed him those mineral
veins and spars in our whin-stone, that he had never observed the like,
in lavas We have now formed some conclusions with regard to the nature
and production of those parts of the land of this globe which we
have had the means of examining perfectly; but; from the accounts of
travellers, and from, the specimens which are brought to us from distant
parts, we have reason to believe, that all the rest of the earth is
of the same nature with that which has been now considered. The great
masses of the earth are the same every where; and all the different
species of earths, of rocks or stone, which have as yet appeared, are to
be found in the little space of this our island.
It is true, that there are peculiar productions in the mineral kingdom
which are rare, as being found only in few places; but these things are
merely accidental in relation to the land, for they belong in property
to those parts of the mineral region which we never see. Such are, the
diamond of the east, the platina of the west, and the tin of Cornwall,
Germany, and Sumatra. Gold and silver, though found in many countries,
do not appear to be immediately necessary in the production of a
habitable country. Iron, again, is universal in the operations of the
globe, and is found often in that profusion which equals its utility.
Between these two extremes, we find all other minerals, that is to say,
here and there in moderate quantity, and apparently in some proportion
to their use. But all these substances are to be considered as the
vapours of the mineral regions, condensed occasionally in the crevices
of the land; and it is only the rocks and strata (in which those mineral
veins are found) that are now examined with regard to their original
composition, at the bottom of the sea, as well as to that, operation by
which those bodies had been indurated in their substance, and elevated
from the place in which they had been formed.
Thus, we have sufficient reason to believe, that, in knowing the
construction of the land in Europe, we know the constitution of the land
in every part of the globe. Therefore, we may proceed to form general
conclusions, from the knowledge of the mineral region, thus acquired in
studying those parts which are seen.
Having thus found, _first_, That the consolidated and indurated masses
of our strata had suffered the effects of violent heat and fusion;
_2dly_, That those strata, which had been formed in a regular manner at
the bottom of the sea, have been violently bended, broken, and removed
from their original place and situation; and, _lastly_, Having now found
the most indubitable proof, that the melting, breaking, and removing
power of subterraneous fire, has been actually exerted upon this land
which we examine, we cannot hesitate in ascribing these operations as a
cause to those effects which are exposed to our view. Now, these may be
considered as consisting in the solid state and present situation of
those stratified bodies, originally formed by subsidence in the ocean;
appearances which cannot, in reason, be ascribed to any other cause, and
which, upon this principle, are perfectly explained.
It is not meant to specify every particular in the means employed by
nature for the elevation of our land. It is sufficient to have shown,
that there is, in nature, means employed for the consolidating of
strata, formed originally of loose and incoherent materials; and that
those same means have also been employed in changing the place and
situation of those strata. But how describe an operation which man
cannot have any opportunity of perceiving? Or how imagine that, for
which, perhaps, there are not proper data to be found? We only know,
that the land is raised by a power which has for principle subterraneous
heat; but, how that land is preserved in its elevated station, is a
subject in which we have not even the means to form conjecture; at
least, we ought to be cautious how we indulge conjecture in a subject
where no means occur for trying that which is but supposition.
We now proceed, from the facts which have been properly established, to
reason with regard to the duration of this globe, or the general view of
its operations, as a living world, maintaining plants and animals.
SECTION IV.
System of Decay and Renovation observed in the Earth.
Philosophers observing an apparent disorder and confusion in the solid
parts of this globe, have been led to conclude, that there formerly
existed a more regular and uniform state, in the constitution of this
earth; that there had happened some destructive change; and that the
original structure of the earth had been broken and disturbed by some
violent operation, whether natural, or from a super-natural cause. Now,
all these appearances, from which conclusions of this kind have been
formed, find the most perfect explanation in the theory which we have
been endeavouring to establish; for they are the facts from whence we
have reasoned, in discovering the nature and constitution of this earth:
Therefore, there is no occasion for having recourse to any unnatural
supposition of evil, to any destructive accident in nature, or to the
agency of any preternatural cause, in explaining that which actually
appears.
It is necessary for a living or inhabited world, that this should
consist of land and water. It is also necessary, that the land should be
solid and stable, refilling, with great power, the violent efforts
of the ocean; and, at the same time, that this solid land should be
resolved by the influence of the sun and atmosphere, so as to decay,
and thus become a soil for vegetation. But these general intentions are
perfectly fulfilled in the constitution of our earth, which has been now
investigated. This great body being formed of different mixed masses,
having various degrees of hardness and solubility, proper soil for
plants is supplied from the gradual resolution of the solid parts;
fertility in those soils arises from the mixture of different elementary
substances; and stability is procured to that vegetable world, by the
induration of certain bodies, those rocks and stones, which protect the
softer masses of clay and soil.
In this manner, also, will easily be explained those natural appearances
which diversify the surface of the earth for the use of plants and
animals, and those objects which beautify the face of nature for the
contemplation of mankind. Such are, the distinctions of mountains and
valleys, of lakes and rivers, of dry barren deserts and rich watered
plains, of rocks which stand apparently unimpaired by the lapse of time,
and sands which fluctuate with the winds and tides. All these are the
effects of steady causes; each of these has its proper purpose in the
system of the earth; and in that system is contained another, which is
that of living growing bodies, and of animated beings.
But, besides this, man, the intellectual being, has, in this subject of
the mineral kingdom, the means of gratifying the desire of knowledge, a
faculty by which he is distinguished from the animal, and by which he
improves his mind in knowing causes. Man is not satisfied, like the
brute, in seeing things which are; he seeks to know how things have
been, and what they are to be. It is with pleasure that he observes
order and regularity in the works of nature, instead of being disgusted
with disorder and confusion; and he is made happy from the appearance of
wisdom and benevolence in the design, instead of being left to suspect
in the Author of nature, any of that imperfection which he finds in
himself.
Let us now take a view of that system of mineral economy, in which may
be perceived every mark of order and design, of provident wisdom and
benevolence.
We have been endeavouring to prove, that all the continents and islands
of this globe had been raised above the surface of the ocean; we have
also aimed at pointing out the cause of this translation of matter, as
well as of the general solidity of that which is raised to our view;
but however this theory shall be received, no person of observation can
entertain a doubt, that all, or almost all we see of this earth, had
been originally formed at the bottom of the sea. We have now another
object in our view; this is to investigate the operations of the globe,
at the time that the foundation of this land was laying in the waters of
the ocean, and to trace the existence and the nature of things, before
the present land appeared above the surface of the waters. We should
thus acquire some knowledge of the system according to which this world
is ruled, both in its preservation and production; and we might be thus
enabled to judge, how far the mineral system of the world shall appear
to be contrived with all the wisdom, which is so manifest in what are
termed the animal and vegetable kingdoms.
It must not be imagined that this undertaking is a thing unreasonable
in its nature; or that it is a work necessarily beset with any
unsurmountable difficulty; for, however imperfectly we may fulfill this
end proposed, yet, so far as it is to natural causes that are to be
ascribed the operations of former time, and so far as, from the present
state of things, or knowledge of natural history, we have it in our
power to reason from effect to cause, there are, in the constitution of
the world, which we now examine, certain means to read the annals of a
former earth.
The object of inquiry being the operations of the globe, during the time
that the present earth was forming at the bottom of the sea, we are now
to take a very general view of nature, without descending into those
particulars which so often occupy the speculations of naturalists, about
the present state of things. We are not at present to enter into any
discussion with regard to what are the primary and secondary mountains
of the earth; we are not to consider what is the first, and what the
last, in those things which now are seen; whatever is most ancient in
the strata which we now examine, is supposed to be collecting at the
bottom of the sea, during the period concerning which we are now to
inquire.
We have already considered those operations which had been necessary
in forming our solid land, a body consisting of materials originally
deposited at the bottom of the ocean; we are now to investigate the
source from whence had come all those materials, from the collection of
which the present land is formed; and from knowing the state in
which those materials had existed, previously to their entering the
composition of our strata, we shall learn something concerning the
natural history of this world, while the present earth was forming in
the sea.
We have already observed, that all the strata of the earth are composed
either from the calcareous relicts of sea animals, or from the
collection of such materials as we find upon our shores. At a gross
computation, there may perhaps be a fourth part of our solid land, which
is composed from the matter that had belonged to those animals. Now,
what a multitude of living creatures, what a quantity of animal economy
must have been required for producing a body of calcareous matter
which is interspersed throughout all the land of the globe, and which
certainly forms a very considerable part of that mass! Therefore, in
knowing how those animals had lived, or with what they had been fed, we
shall have learned a most interesting part of the natural history of
this earth; a part which it is necessary to have ascertained, in order
to see the former operations of the globe, while preparing the materials
of the present land. But, before entering upon this subject, let us
examine the other materials of which our land is formed.
Gravel forms a part of those materials which compose our solid land; but
gravel is no other than a collection of the fragments of solid stones
worn round, or having their angular form destroyed by agitation in
water, and the attrition upon each other, or upon similar hard bodies.
Consequently, in finding masses of gravel in the composition of our
land, we must conclude, that there had existed a former land, on which
there had been transacted certain operations of wind and water, similar
to those which are natural to the globe at present, and by which new
gravel is continually prepared, as well as old gravel consumed or
diminished by attrition upon our shores.
Sand is the material which enters, perhaps in greatest quantity, the
composition of our land. But sand, in general, is no other than small
fragments of hard and solid bodies, worn or rounded more or less by
attrition; consequently, the same natural history of the earth, which
is investigated from the masses of gravel, is also applicable to those
masses of sand which we find forming so large a portion of our present
land throughout all the earth[16].
[Note 16: Sand is a term that denotes no particular substance; although
by it is commonly meant a siliceous substance, as being by far the most
prevalent. Sand is one of the modifications, of size and shape, in a
hard body or solid substance, which may be infinitely diversified. The
next modification to be distinguished in mineral bodies is that of
gravel; and this differs in no respect from sand, except in point of
size. Next after gravel, in the order of ascent, come stones; and these
bear nearly the same relation to gravel as gravel does to sand. Now,
by stones is to be understood the fragments of rocks or solid mineral
bodies; and there is a perfect gradation from those stones to sand.
I have already endeavoured to explain the formation of those stony
substances; and now I am treating of a certain system of circulation,
which is to be found among minerals.
M. de Luc censures me for not giving the origin of sand, of which I form
the strata of the earth. He seems to have misunderstood my treatise. I
do not pretend, as he does in his theory, to describe the beginning of
things; I take things such as I find them at present, and from these
I reason with regard to that which must have been. When, from a thing
which is well known, we explain another which is less so, we then
investigate nature; but when we imagine things without a pattern or
example in nature, then, instead of natural history, we write only
fable.
M. de Luc, in the letter already mentioned, says, "that sand may be, and
I think it is, a substance which has formed _strata_ by _precipitation
in a liquid_." This is but an opinion, which may be either true or
false. If it be true, it is an operation of the mineral kingdom of which
I am ignorant. In all the sand which I have ever examined, I have never
seen any that might not be referred to the species of mineral substance
from which it had been formed. When this author shall have given us
any kind of information with regard to the production of sand _by
precipitation in a liquid_, it will then be time enough to think of
forming the strata of the earth with that sand.]
Clay is now to be considered as the last of those materials of which
our strata are composed; but, in order to understand the nature of this
ingredient, something must be premised.
Clay is a mixture of different earths or hard substances, in an
impalpable state. Those substances are chiefly the siliceous and
aluminous earths. Other earths are occasionally mixed in clays, or
perhaps always to be found in some small portion. But this does not
affect the general character of clay; it only forms a special variety in
the subject. A sensible or considerable portion of calcareous earth, in
the composition of clay, constitutes a marl, and a sufficient admixture
of sand, a loam.
An indefinite variety of those compositions of clay form a large portion
of the present strata, all indurated and consolidated in various
degrees; but this great quantity of siliceous, argillaceous, and
other compound substances, in form of earth or impalpable sediment,
corresponds perfectly with that quantity of those same substances which
must have been prepared in the formation of so much gravel and sand, by
the attrition of those bodies in the moving waters.
Therefore, from the consideration of those materials which compose the
present land, we have reason to conclude, that, during the time this
land was forming, by the collection of its materials at the bottom of
the sea, there had been a former land containing materials similar to
those which we find at present in examining the earth. We may also
conclude, that there had been operations similar to those which we
now find natural to the globe, and necessarily exerted in the actual
formation of gravel, sand, and clay. But what we have now chiefly in
view to illustrate is this, that there had then been in the ocean a
system of animated beings, which propagated their species, and which
have thus continued their several races to this day.
In order to be convinced of that truth, we have but to examine the
strata of our earth, in which we find the remains of animals. In this
examination, we not only discover every genus of animal which at present
exists in the sea, but probably every species, and perhaps some species
with which at present we are not acquainted. There are, indeed,
varieties in those species, compared with the present animals which we
examine, but no greater varieties than may perhaps be found among the
same species in the different quarters of the globe. Therefore, the
system of animal life, which had been maintained in the ancient sea, had
not been different from that which now subsists, and of which it belongs
to naturalists to know the history.
It is the nature of animal life to be ultimately supported from matter
of vegetable production. Inflammable matter may be considered as the
_pabulum_ of life. This is prepared in the bodies of living plants,
particularly in their leaves exposed to the sun and light. This
inflammable matter, on the contrary, is consumed in animal bodies, where
it produces heat or light, or both. Therefore, however animal matter, or
the pabulum of life, may circulate through a series of digesting powers,
it is constantly impaired or diminishing in the course of this economy,
and, without the productive power of plants, it would finally be
extinguished.[17]
[Note 17: See Dissertations on different subjects of Natural Philosophy,
part II.]
The animals of the former world must have been sustained during
indefinite successions of ages. The mean quantity of animal matter,
therefore, must have been preserved by vegetable production, and the
natural waste of inflammable substance repaired with continual addition;
that is to say, the quantity of inflammable matter necessary to the
animal consumption, must have been provided by means of vegetation.
Hence we must conclude, that there had been a world of plants, as well
as an ocean replenished with living animals.
We are now, in reasoning from principles, come to a point decisive of
the question, and which will either confirm the theory, if it be just,
or confute our reasoning, if we have erred. Let us, therefore, open
the book of Nature, and read in her records, if there had been a world
bearing plants, at the time when this present world was forming at the
bottom of the sea.
Here the cabinets of the curious are to be examined; but here some
caution is required, in order to distinguish things perfectly different,
which sometimes are confounded.
Fossil wood, to naturalists in general, is wood dug up from under
ground, without inquiring whether this had been the production of the
present earth, or that which had preceded it in the circulation of land
and water. The question is important, and the solution of it is, in
general, easy. The vegetable productions of the present earth, however
deep they may be found buried beneath its surface, and however ancient
they may appear, compared with the records of our known times, are new,
compared with the solid land on which they grew; and they are only
covered with the produce of a vegetable soil, or the alluvion of the
present land on which we dwell, and on which they had grown. But the
fossil bodies which form the present subject of inquiry, belonged to
former land, and are found only in the sea-born strata of our present
earth. It is to these alone that we appeal, in order to prove the
certainty of former events.
Mineralised wood, therefore, is the object now inquired after; that wood
which had been lodged in the bottom of the sea, and there composed part
of a stratum, which hitherto we have considered as only formed of the
materials proper to the ocean. Now, what a profusion of this species of
fossil wood is to be found in the cabinets of collectors, and even in
the hands of lapidaries, and such artificers of polished stones! In some
places, it would seem to be as common as the agate.
I shall only mention a specimen in my own collection. It is wood
petrified with calcareous earth, and mineralised with pyrites. This
specimen of wood contains in itself, even without the stratum of stone
in which it is embedded, the most perfect record of its genealogy.
It had been eaten or perforated by those sea worms which destroy the
bottoms of our ships. There is the clearest evidence of this truth.
Therefore, this wood had grown upon land which flood above the level of
sea, while the present land was only forming at the bottom of the ocean.
Wood is the most substantial part of plants, as shells are the more
permanent part of marine animals. It is not, however, the woody part
alone of the ancient vegetable world that is transmitted to us in
the record of our mineral pages. We have the type of many species
of foliage, and even of the most delicate flower; for, in this way,
naturalists have determined, according to the Linnaean system, the
species, or at least the genus, of the plant. Thus, the existence of a
vegetable system at the period now in contemplation, so far from being
doubtful, is a matter of physical demonstration.
The profusion of this vegetable matter, delivered into the ocean, which
then generated land, is also evidenced in the amazing quantities of
mineral coal which is to be found in perhaps every region of the earth.
Nothing can be more certain, than that all the coaly or bituminous
strata have had their origin from the substance of vegetable bodies
that grew upon the land. Those strata, tho', in general, perfectly
consolidated, often separate horizontally in certain places; and there
we find the fibrous or vascular structure of the vegetable bodies.
Consequently, there is no doubt of fossil coal being a substance
of vegetable production, however animal substances also may have
contributed in forming this collection of oleaginous or inflammable
matter.
Having thus ascertained the state of a former earth, in which plants
and animals had lived, as well as the gradual production of the present
earth, composed from the materials of a former world, it must be
evident, that here are two operations which are necessarily consecutive.
The formation of the present earth necessarily involves the destruction
of continents in the ancient world; and, by pursuing in our mind the
natural operations of a former earth, we clearly see the origin of that
land, by the fertility of which, we, and all the animated bodies of the
sea, are fed. It is in like manner, that, contemplating the present
operations of the globe, we may perceive the actual existence of those
productive causes, which are now laying the foundation of land in the
unfathomable regions of the sea, and which will, in time, give birth to
future continents.
But though, in generalising the operations of nature, we have arrived at
those great events, which, at first sight, may fill the mind with
wonder and with doubt, we are not to suppose, that there is any violent
exertion of power, such as is required in order to produce a great event
in little time; in nature, we find no deficiency in respect of time, nor
any limitation with regard to power. But time is not made to flow in
vain; nor does there ever appear the exertion of superfluous power, or
the manifestation of design, not calculated in wisdom to effect some
general end.
The events now under consideration may be examined with a view to see
this truth; for it may be inquired, Why destroy one continent in order
to erect another? The answer is plain; Nature does not destroy a
continent from having wearied of a subject which had given pleasure, or
changed her purpose, whether for a better or a worse; neither does she
erect a continent of land among the clouds, to show her power, or to
amaze the vulgar man; Nature has contrived the productions of vegetable
bodies, and the sustenance of animal life, to depend upon the gradual
but sure destruction of a continent; that is to say, these two
operations necessarily go hand in hand. But with such wisdom has nature
ordered things in the economy of this world, that the destruction of one
continent is not brought about without the renovation of the earth in
the production of another; and the animal and vegetable bodies, for
which the world above the surface of the sea is leveled with its bottom,
are among the means employed in those operations, as well as the
sustenance of those living beings is the proper end in view.
Thus, in understanding the proper constitution of the present earth, we
are led to know the source from whence had come all the materials which
nature had employed in the construction of the world which appears; a
world contrived in consummate wisdom for the growth and habitation of a
great diversity of plants and animals; and a world peculiarly adapted
to the purposes of man, who inhabits all its climates, who measures its
extent, and determines its productions at his pleasure.
The whole of a great object or event fills us with wonder and
astonishment, when all the particulars, in the succession of which the
whole had been produced, may be considered without the least emotion.
When, for example, we behold the pyramids of Egypt, our mind is agitated
with a crowd of ideas that highly entertains the person who understands
the subject; but the carrying a heavy stone up to the top of a hill or
mountain would give that person little pleasure or concern. We wonder at
the whole operation of the pyramid, but not at any one particular part.
The raising up of a continent of land from the bottom of the sea, is an
idea that is too great to be conceived easily in all the parts of its
operations, many of which are perhaps unknown to us; and, without being
properly understood, so great an idea may appear like a thing that is
imaginary. In like manner, the co-relative, or corresponding operation,
the destruction of the land, is an idea that does not easily enter into
the mind of man in its totality, although he is daily witness to part of
the operation. We never see a river in a flood, but we must acknowledge
the carrying away of part of our land, to be sunk at the bottom of the
sea; we never see a storm upon the coast, but we are informed of a
hostile attack of the sea upon our country; attacks which must, in time,
wear away the bulwarks of our soil, and sap the foundations of our
dwellings. Thus, great things are not understood without the analysing
of many operations, and the combination of time with many events
happening in succession.
Let us now consider what is to be the subject of examination, and where
it is that we are to observe those operations which must determine
either the stability or the instability of this land on which we live.
Our land has two extremities; the tops of the mountains, on the one
hand, and the sea-shores, on the other: It is the intermediate space
between these two, that forms the habitation of plants and animals.
While there is a sea-shore and a higher ground there is that which is
required in the system of the world: Take these away, and there would
remain an aqueous globe, in which the world would perish. But, in the
natural operations of the world, the land is perishing continually; and
this is that which now we want to understand.
Upon the one extremity of our land, there is no increase, or there is no
accession of any mineral substance. That place is the mountain-top, on
which nothing is observed but continual decay. The fragments of the
mountain are removed in a gradual succession from the highest station to
the lowest. Being arrived at the shore, and having entered the dominion
of the waves, in which they find perpetual agitation, these hard
fragments, which had eluded the resolving powers natural to the surface
of the earth, are incapable of resisting the powers here employed for
the destruction of the land. By the attrition of one hard body upon
another, the moving stones and rocky shore, are mutually impaired. And
that solid mass, which of itself had potential liability against the
violence of the waves, affords the instruments of its own destruction,
and thus gives occasion to its actual instability.
In order to understand the system of the heavens, it is necessary to
connect together periods of measured time, and the distinguished places
of revolving bodies. It is thus that system may be observed, or wisdom,
in the proper adapting of powers to an intention. In like manner, we
cannot understand the system of the globe, without seeing that progress
of things which is brought about in time, thus measuring the natural
operations of the earth with those of the heavens. This is properly the
business of the present undertaking.
Our object is to know the time which had elapsed since the foundation of
the present continent had been laid at the bottom of the ocean, to the
present moment in which we speculate on these operations. The space is
long; the data for the calculations are, perhaps, deficient: No matter;
so far as we know our error, or the deficiency in our operation, we
proceed in science, and shall conclude in reason. It is not given to man
to know what things are truly in themselves, but only what those things
are in his thought. We seek not to know the precise measure of any
thing; we only understand the limits of a thing, in knowing what it is
not, either on the one side or the other.
We are investigating the age of the present earth, from the beginning of
that body which was in the bottom of the sea, to the perfection of its
nature, which we consider as in the moment of our existence; and we have
necessarily another aera, which is collateral, or correspondent, in the
progress of those natural events. This is the time required, in the
natural operations of this globe, for the destruction of a former
earth; an earth equally perfect with the present and an earth equally
productive of growing plants and living animals. Now, it must appear,
that, if we had a measure for the one of those corresponding operations,
we would have an equal knowledge of the other.
The formation of a future earth being in the bottom of the ocean, at
depths unfathomable to man, and in regions far beyond the reach of his
observation, here is a part of the process which cannot be taken as a
principle in forming an estimate of the whole. But, in the destruction
of the present earth, we have a process that is performed within the
limits of our observation; therefore, in knowing the measure of this
operation, we shall find the means of calculating what had passed on a
former occasion, as well as what will happen in the composition of a
future earth. Let us, therefore, now attempt to make this estimate of
time and labour.
The highest mountain may be levelled with the plain from whence it
springs, without the loss of real territory in the land; but when the
ocean makes encroachment on the basis of our earth, the mountain,
unsupported, tumbles with its weight; and with the accession of hard
bodies, moveable with the agitation of the waves, gives to the sea the
power of undermining farther and farther into the solid basis of our
land. This is the operation which is to be measured; this is the mean
proportional by which we are to estimate the age of worlds that have
terminated, and the duration of those that are but beginning.
But how shall we measure the decrease of our land? Every revolution of
the globe wears away some part of some rock upon some coast; but the
quantity of that decrease, in that measured time, is not a measurable
thing. Instead of a revolution of the globe, let us take an age. The age
of man does no more in this estimate than a single year. He sees,
that the natural course of things is to wear away the coast, with the
attrition of the sand and stones upon the shore; but he cannot find a
measure for this quantity which shall correspond to time, in order to
form an estimate of the rate of this decrease.
But man is not confined to what he sees; he has the experience of former
men. Let us then go to the Romans and the Greeks in search of a measure
of our coasts, which we may compare with the present state of things.
Here, again, we are disappointed; their descriptions of the shores of
Greece and of Italy, and their works upon the coast, either give no
measure of a decrease, or are not accurate enough for such a purpose.
It is in vain to attempt to measure a quantity which escapes our notice,
and which history cannot ascertain; and we might just as well attempt to
measure the distance of the stars without a parallax, as to calculate
the destruction of the solid land without a measure corresponding to the
whole.
The description which Polybius has given of the Pontus Euxinus, with
the two opposite Bosphori, the Meotis, the Propontis, and the Port of
Byzantium, are as applicable to the present state of things as they were
at the writing of that history. The filling up of the bed of the
Meotis, an event which, to Polybius, appeared not far off, must also be
considered as removed to a very distant period, though the causes still
continue to operate as before.
But there is a thing in which history and the present state of things do
not agree. It is upon the coast of Spain, where Polybius says there was
an island in the mouth of the harbour of New Carthage. At present, in
place of the island, there is only a rock under the surface of the
water. It must be evident, however, that the loss of this small island
affords no proper ground of calculation for the measure or rate of
wasting which could correspond to the coast in general; as neither
the quantity of what is now lost had been measured, nor its quality
ascertained.
Let us examine places much more exposed to the fury of the waves and
currents than the coast of Carthagena, the narrow fretum, for example,
between Italy and Sicily. It does not appear, that this passage is
sensibly wider than when the Romans first had known it. The Isthmus of
Corinth is also apparently the same at present as it had been two or
three thousand years ago. Scilla and Charibdis remain now, as they had
been in ancient times, rocks hazardous for coasting vessels which had to
pass that strait.
It is not meant by this to say, these rocks have not been wasted by the
sea, and worn by the attrition of moving bodies, during that space of
time; were this true, and that those rocks, the bulwarks of the land
upon those coasts, had not been at all impaired from that period, they
might remain for ever, and thus the system of interchanging the place of
sea and land upon this globe might be frustrated. It is only meant
to affirm, that the quantity which those rocks, or that coast, have
diminished from the period of our history, has either been too small
a thing for human observation, or, which is more probable, that no
accurate measurement of the subject, by which this quantity of decrease
might have been ascertained, had been taken and recorded. It must be
also evident, that a very small operation of an earthquake would be
sufficient to render every means of information, in this manner of
mensuration, unsatisfactory or precarious.
Pliny says Italy was distant from Sicily a mile and a half; but we
cannot suppose that this measure was taken any otherwise than by
computation, and such a measure is but little calculated to afford us
the just means of a comparison with the present distance. He also says,
indeed, that Sicily had been once joined with Italy. His words are:
"Quondam Brutio agro cohaerens, mox interfuso mari avulsa.[18]" But all
that we can conclude from this history of Pliny is, that, in all times,
to people considering the appearances of those two approached coasts,
it had seemed probable, that the sea formed a passage between the two
countries which had been once united; in like manner as is still more
immediately perceived, in that smaller disjunction which is made between
the island of Anglesey and the continent of Wales.
[Note 18: Lib. 3. cap. 8.]
The port of Syracuse, with the island which forms the greater and
lesser, and the fountain of Arethusa, the water of which the ancients
divided from the sea with a wall, do not seem to be altered. From Sicily
to the coast of Egypt, there is an uninterrupted course of sea for a
thousand miles; consequently, the wind, in such a stretch of sea, should
bring powerful waves against those coasts: But, on this coast of Egypt,
we find the rock on which was formerly built the famous tower of Pharos;
and also, at the eastern extremity of the port Eunoste, the sea-bath,
cut in the solid rock upon the shore. Both those rocks, buffeted
immediately with the waves of the Mediterranean sea, are, to all
appearance, the same at this day as they were in ancient times.[19]
[Note 19: Lettres sur l'Egypte, M. Savary.]
Many other such proofs will certainly occur, where the different parts
of those coasts are examined by people of observation and intelligence.
But it is enough for our present purpose, that this decrease of the
coasts in general has not been observed; and that it is as generally
thought, that the land is gaining upon the sea, as that the sea is
gaining upon the land.
To sum up the argument, we are certain, that all the coasts of the
present continents are wasted by the sea, and constantly wearing away
upon the whole; but this operation is so extremely slow, that we cannot
find a measure of the quantity in order to form an estimate: Therefore,
the present continents of the earth, which we consider as in a state of
perfection, would, in the natural operations of the globe, require a
time indefinite for their destruction.
But, in order to produce the present continents, the destruction of a
former vegetable world was necessary; consequently, the production of
our present continents must have required a time which is indefinite.
In like manner, if the former continents were of the same nature as the
present, it must have required another space of time, which also is
indefinite, before they had come to their perfection as a vegetable
world.
We have been representing the system of this earth as proceeding with
a certain regularity, which is not perhaps in nature, but which is
necessary for our clear conception of the system of nature. The
system of nature is certainly in rule, although we may not know every
circumstance of its regulation. We are under a necessity, therefore, of
making regular suppositions, in order to come at certain conclusions
which may be compared with the present state of things.
It is not necessary that the present land should be worn away and
wasted, exactly in proportion as new land shall appear; or, conversely,
that an equal proportion of new land should always be produced as the
old is made to disappear. It is only required, that at all times, there
should be a just proportion of land and water upon the surface of the
globe, for the purpose of a habitable world.
Neither is it required in the actual system of this earth, that every
part of the land should be dissolved in its structure, and worn away by
attrition, so as to be floated in the sea. Parts of the land may often
sink in a body below the level of the sea, and parts again may be
restored, without waiting for the general circulation of land and water,
which proceeds with all the certainty of nature, but which advances with
an imperceptible progression. Many of such apparent irregularities may
appear without the least infringement on the general system. That system
is comprehended in the preparation of future land at the bottom of the
ocean, from those materials which the dissolution and attrition of
the present land may have provided, and from those which the natural
operations of the sea afford.
In thus accomplishing a certain end, we are not to limit nature with the
uniformity of an equable progression, although it be necessary in our
computations to proceed upon equalities. Thus also, in the use of means,
we are not to prescribe to nature those alone which we think suitable
for the purpose, in our narrow view. It is our business to learn of
nature (that is by observation) the ways and means, which in her wisdom
are adopted; and we are to imagine these only in order to find means for
further information, and to increase our knowledge from the examination
of things which actually have been. It is in this manner, that intention
may be found in nature; but this intention is not to be supposed, or
vainly imagined, from what we may conceive to be.
We have been now supposing, that the beginning of our present earth had
been laid in the bottom of the ocean, at the completion of the former
land; but this was only for the sake of distinctness. The just view is
this, that when the former land of the globe had been complete, so as
to begin to waste and be impaired by the encroachment of the sea, the
present land began to appear above the surface of the ocean. In this
manner we suppose a due proportion to be always preserved of land and
water upon the surface of the globe, for the purpose of a habitable
world, such as this which we possess. We thus, also, allow time and
opportunity for the translation of animals and plants to occupy the
earth.
But, if the earth on which we live, began to appear in the ocean at
the time when the last began to be resolved, it could not be from the
materials of the continent immediately preceding this which we examine,
that the present earth had been constructed; for the bottom of the ocean
must have been filled with materials before land could be made to appear
above its surface.
Let us suppose that the continent, which is to succeed our land, is at
present beginning to appear above the water in the middle of the Pacific
Ocean, it must be evident, that the materials of this great body, which
is formed and ready to be brought forth, must have been collected from
the destruction of an earth, which does not now appear. Consequently,
in this true statement of the case, there is necessarily required the
destruction of an animal and vegetable earth prior to the former land;
and the materials of that earth which is first in our account, must have
been collected at the bottom of the ocean, and begun to be concocted for
the production of the present earth, when the land immediately preceding
the present had arrived at its full extent.
This, however, alters nothing with regard to the nature of those
operations of the globe. The system is still the same. It only protracts
the indefinite space of time in its existence, while it gives us a view
of another distinct period of the living world; that is to say, the
world which we inhabit is composed of the materials, not of the earth
which was the immediate predecessor of the present, but of the earth
which, in ascending from the present, we consider as the third, and
which had preceded the land that was above the surface of the sea, while
our present land was yet beneath the water of the ocean. Here are three
distinct successive periods of existence, and each of these is, in our
measurement of time, a thing of indefinite duration.
We have now got to the end of our reasoning; we have no data further
to conclude immediately from that which actually is: But we have got
enough; we have the satisfaction to find, that in nature there is
wisdom, system, and consistency. For having, in the natural history of
this earth, seen a succession of worlds, we may from this conclude that
there is a system in nature; in like manner as, from seeing revolutions
of the planets, it is concluded, that there is a system by which they
are intended to continue those revolutions. But if the succession of
worlds is established in the system of nature, it is in vain to look for
any thing higher in the origin of the earth. The result, therefore, of
this physical inquiry is, that we find no vestige of a beginning,--no
prospect of an end.
CHAPTER II.
An Examination of Mr KIRWAN'S Objections to the Igneous Origin of Stony
Substances.
A theory which is founded on a new principle, a theory which has to make
its way in the public mind by overturning the opinions commonly received
by philosophising men, and one which has nothing to recommend it but the
truth of its principles, and the view of wisdom or design to which it
leads, neither of which may perhaps be perceived by the generality of
people, such a theory, I say, must meet with the strongest opposition
from the prejudices of the learned, and from the superstition of those
who judge not for themselves in forming their notions, but look up to
men of science for authority. Such is the case with some part of the
Theory of the Earth, which I have given, and which will probably give
offence to naturalists who have espoused an opposite opinion. In order,
then, to obtain the approbation of the public, it may not be enough to
give a theory that should be true, or altogether unexceptionable it may
be necessary to defend every point that shall be thought exceptionable
by other theorists, and to show the fallacy of every learned objection
that may be made against it. It is thus, in general, that truth and
error are forced to struggle together, in the progress of science; and
it is only in proportion as science removes erroneous conceptions, which
are necessarily in the constitution of human knowledge, that truth will
find itself established in natural philosophy.
Mr Kirwan has written a dissertation, entitled, _Examination of the
Supposed Igneous Origin of Stony Substances_, which was read in the
Royal Irish Academy. The object of that dissertation is to state certain
objections, which have occurred to him, against the Theory of the Earth
published in the Transactions of the Edinburgh Royal Society; and he has
attacked that theory in all the points where it appears to him to be
vulnerable. It is to these objections that I am now to give an answer.
The authority given to this dissertation, by the Royal Irish Academy,
as well as the reputation of the author, make it necessary for me
to endeavour to put in their true light the facts alleged in that
performance, and to analyse the arguments employed, in order to judge of
the reasoning by which the theory of mineral fusion is refuted in this
Examination.
A theory founded on truth, and formed according to the proper rules of
science, can ever suffer from a strict examination, by which it would
be but the more and more confirmed. But, where causes are to be traced
through a chain of various complicated effects, an examination not
properly conducted upon accurate analytical principles, instead of
giving light upon a subject in which there had been obscurity and doubt,
may only serve to perplex the understanding, and bring confusion into a
subject which was before sufficiently distinct. To redress that evil,
then, must require more labour and some address; and this is an
inconveniency that may be looked for, more or less, in every
controversial discussion.
I do not mean to enter any farther into the defence of my theory in
this chapter, than what is necessary to answer a man of science and
respectability, who has stated his objections. The observations which
he has made appear to me to be founded on nothing more than common
prejudice, and misconceived notions of the subject. I am therefore
to point out that erroneous train of reasoning, into which a hasty
superficial view of things, perhaps, has led the patron of an opposite
opinion to see my theory in an unfavourable light. This, however, is not
all; for, that train of inconsequential reasoning is so congenial with
the crude and inconsiderate notion generally entertained, of solid
mineral bodies having been formed by the infiltration of water into
the earth, that no opportunity should be lost of exposing an erroneous
manner of reasoning, which is employed in supporting a hypothesis
founded upon certain operations of the surface of this earth that cannot
be properly applied to the formation of mineral bodies. This object,
therefore, so far as it may come in the way, will be attended to in
this discussion, although I shall have another opportunity of farther
enlarging upon that subject.
Our author begins by examining a geological operation, the very opposite
to that of mineral consolidation, and which would seem to have little
connection with the subject of this dissertation. In my theory, I
advanced two propositions with regard to the economy of this world:
First, That the solid masses of this earth, when exposed to the
atmosphere, decay, and are resolved into loose materials, of which the
vegetable soil upon the surface is in part composed; and, secondly, That
these loose materials are washed away by the currents of water, and
thus carried at last into the sea. Our author says "Here are two
suppositions, neither of which is grounded on facts;" and yet he has
but the moment before made the following confession: "That the soil,
however, receives an increase from some species of stones that moulder
by exposition to the air cannot be denied, but there is no proof that
all soil has arisen from decomposition."--Surely _all soil_, that
is made from the _hard and compact_ body of the land, which is my
proposition, must have arisen from _decomposition_; and I have no where
said, that _all_ the soil of this earth is made from the decomposition
or detritus of those stony substances; for, masses of looser sand and
softer substances contribute still more to the formation of vegetable
soils.
With regard to the other proposition, our author says, "Soil is not
constantly carried away by the water, even from mountains."--I have not
said that it is _constantly_ washed away; for, while it is soil in which
plants grow, it is not travelling to the sea, although it be on the road,
and must there arrive in time. I have said, that it is _necessarily_
washed away, that is, occasionally. M. de Luc's authority is then
referred to, as refuting this operation of water and time upon the soil.
Now, I cannot help here observing, that our author seems to have as
much misapprehended M. de Luc's argument as he has done mine. That
philosopher, in his letters to the Queen, has described most accurately
the decay of the rocks and solid mountains of the Alps and Jura, and the
travelling of their materials by water, although he does not carry them
to the sea. It is true, indeed, that this author, who supposes the
present earth on which we dwell very young, is anxious to make an earth,
_in time_, that shall not decay nor be washed away at all; but that time
is not come yet; therefore the authority, here given against my
theory, is the speculative supposition, or mere opinion, of a natural
philosopher, with regard to an event which may never come to pass, and
which I shall have occasion to consider fully in another place.
Our author had just now said, that I have advanced two suppositions,
_neither of which is grounded on facts_: Now, with regard to the one, he
has acknowledged, that the mouldering of stones takes place, which is
the fact on which that proposition is grounded; and with regard to the
other, the only authority given against it is founded expressly upon
the moving of soil by means of the rain water, in order to make sloping
plains of mountains. Here, therefore, I have grounded my propositions
upon facts; and our author has founded his objections, first, upon a
difficulty which he has himself removed; and, secondly, upon nothing but
a visionary opinion, with regard to an earth which is not yet made, and
which, when once made, is never more to change.
After making some unimportant observations,--of all water not flowing
into the sea,--and of the travelled materials being also deposited upon
the plains, etc. our author thus proceeds: "Hence the conclusion of our
author relative to the imperfect constitution of the globe falls to the
ground; and the pains he takes to learn, _by what means a decayed world
may be renovated_, are superfluous."--The object of my theory is
to show, that this decaying nature of the solid earth is the very
_perfection_ of its constitution, as a living world; therefore, it
was most proper that I should _take pains to learn_ by what means the
decayed parts might be renovated. It is true, indeed, that this will be
superfluous, when once that constitution of the earth, which M. de Luc
thinks is preparing, shall be finished; but, in the mean time, while
rivers carry the materials of our land, and while the sea impairs the
coast, I may be allowed to suppose that this is the actual constitution
of the earth.
I cannot help here animadverting upon what seems to be our author's
plan, in making these objections, which have nothing to do with his
examination. He accuses me of giving this world a false or imperfect
constitution, (in which the solid land is considered as resolvable, and
the materials of that land as being washed away into the sea,) for no
other reason, that I can see, but because this may imply the formation
of a future earth, which he is not disposed to allow; and, he is now to
deny the stratified construction of this present earth to have been made
by the deposits of materials at the bottom of the sea, because that
would prove the existence of a former earth, which is repugnant to his
notion of the origin of things, and is contrary, as he says, to reason,
and the tenor of the Mosaic history. Let me observe, in passing, that M.
de Luc, of whose opinions our author expresses much approbation, thinks
that he proves, from the express words and tenor of the Mosaic history,
that the present earth was at the bottom of the sea not many years ago,
and that the former earth had then disappeared.
But, what does our author propose to himself, in refusing to admit my
view of the operations which are daily transacting upon the surface of
this earth, where there is nothing dark or in the least mysterious, as
there may be in the mineral regions? Does he mean to say, that it is not
the purpose of this world to provide soil for plants to grow in? Does
he suppose that this soil is not moveable with the running water of the
surface? and, Does he think that it is not necessary to replace that
soil which is removed? This is all that I required in that constitution
of the world which he has thus attacked; and I wish that he or any
person would point out, in what respect I had demanded any thing
unreasonable, or any thing that is not actually to be observed every
day.
Thus I have endeavoured to show, that our author has attacked my theory
in a part where I believe it must be thought invulnerable; but this is
only, I presume, in order that he may make an attack with more advantage
upon another part, viz. the composition of strata from the materials of
an earth thus worn out in the service of vegetation,--materials which
are necessarily removed in order to make way for that change of things
in which consists the active and living system of this world. If he
succeed in this attempt to refute my theory of the original formation
of strata, he would then doubtless find it more easy to persuade
philosophers that the means which I employ in bringing those materials
again to light, when transformed into such solid masses as the system of
this earth requires, are extravagant, unnatural, and unnecessary. Let us
then see how he sets about this undertaking.
With regard to the composition of the earth, it is quoted from my
theory, that _the solid parts of the globe are in general composed
of sand, gravel, argillaceous and calcareous strata, or of various
compositions of these with other substances_; our author then adds,
"This certainly cannot be affirmed as a fact, but rather the contrary;
it holds only true of the surface, the basis of the greater part of
Scotland is evidently a granitic rock, to say nothing of the continents,
both of the Old and New World, according to the testimony of all
mineralogists." This proposition, with regard to the general composition
of the earth, I have certainly not assumed, I have maintained it as a
fact, after the most scrupulous examination of all that, with the most
diligent search, I have been able to see, and of all that authors
have wrote intelligibly upon the subject. If, therefore, I have so
misrepresented this great geological fact on which my theory is
absolutely founded, I must have erred with open eyes; and my theory
of the earth, like others which have gone before it, will, upon close
examination, appear to be unfounded, as the dissertation now before us
is endeavouring to represent it.
Our author here, I think, alleges that the contrary to this, my
fundamental proposition, is the truth; and he has given us Scotland as
an example in which his assertion (founded upon the testimony of all
mineralogists), is illustrated. Now my geological proposition should
certainly be applicable to Scotland, which is the country that I ought
to be best acquainted with; consequently, if what our author here
asserts be true, I would have deserved that blame which he is willing to
throw on me. Let me then beg the readers attention for a moment, that I
may justify myself from that charge, and place in its proper light this
authority, upon so material a point in geology.
I had examined Scotland from the one end to the other before I saw one
stone of granite in its native place, I have moreover examined almost
all England and Wales, (excepting Devonshire and Cornwall) without
seeing more of granite than one spot, not many hundred yards of extent;
this is at Chap; and I know, from information, that there is another
small spot in the middle of England where it is just seen. But, let me
be more particular with regard to Scotland, the example given in proof.
I had travelled every road from the borders of Northumberland and
Westmoreland to Edinburgh; from Edinburgh, I had travelled to
Port-Patrick, and from that along the coast of Galloway and Airshire
to Inverary in Argyleshire, and I had examined every spot between the
Grampians and the Tweedale mountains from sea to sea, without seeing
granite in its place. I had also travelled from Edinburgh by Grief,
Rannock, Dalwhiny, Fort Augustus, Inverness, through east Ross and
Caithness, to the Pentland-Frith or Orkney islands, without seeing one
block of granite in its place. It is true, I met with it on my return
by the east coast, when I just saw it, and no more, at Peterhead and
Aberdeen; but that was all the granite I had ever seen when I wrote
my Theory of the Earth. I have, since that time, seen it in different
places; because I went on purpose to examine it, as I shall have
occasion to describe in the course of this work.
I may now with some confidence affirm, from my own observation, and from
good information with regard to those places where I have not been,
except the northwest corner, I may affirm, I say, that instead of the
basis of the greatest part of Scotland being a granitic rock, which our
author has maintained as an evident thing, there is very little of it
that is so; not perhaps one five hundred part. So far also as I am to
judge from my knowledge of the mineral construction of England and
Wales, which I have examined with the greatest care, and from the
mineral chart which my friend Mr Watt made for me from his knowledge of
Cornwall, I would say that there is scarcely one five hundred part
of Britain that has granite for its basis. All the rest, except the
porphyry and basaltes, consists of stratified bodies, which are composed
more or less of the materials which I mentioned, generally, in the above
quotation, and which our author would dispute.
But do not let me take the advantage of this error of our author with
regard to the mineralogy of Scotland, and thus draw what may be thought
an undue conclusion in favour of my general theory; let us go over and
examine the continent of Europe, and see if it is any otherwise there
than in Britain. From the granite of the Ural mountains, to that which
we find in the Pyrenees, there is no reason, so far as I have been able
to learn, to conclude that things are formed either upon any other
principle, or upon a different scale. But, instead of one five hundred
part, let us suppose there to be one fiftieth part of the earth in
general resting upon granite, I could not have expressed myself
otherwise than I have done; for, when I maintained that the earth in
general consisted of stratified bodies, I said that this was only _nine
tenths, or perhaps ninety-nine hundredths_ of the whole, and I mentioned
that there were other masses of a different origin, which should be
considered separately. Our author, on the contrary, asserts that the Old
and New Worlds, as well as Scotland, are placed upon granite as a basis,
which he says is according to the testimony of all mineralogists.
I shall have occasion to examine this opinion of mineralogists, in
comparing it with those masses of granite which appear to us; and I hope
fully to refute the geological, as well as mineralogical notions with
regard to that body. In the mean time, let me make the following
reflection, which here naturally occurs.
My Theory of the Earth is here examined,--not with the system of
nature, or actual state of things, to which it certainly should have
corresponded,--but with the systematic views of a person, who has formed
his notions of geology from the vague opinion of others, and not from
what he has seen. Had the question been, How far my theory agreed with
other theories, our author might very properly have informed his readers
that it was diametrically opposite to the opinions of mineralogists;
but, this was no reason for concluding it to be erroneous; on the
contrary, it is rather a presumption that I may have corrected the error
of mineralogists who have gone before me, in like manner as it is most
reasonable to presume that our author may have corrected mine. Let us
then proceed to examine how far this shall appear to be the case.
Our author has stated very fairly from the Theory, viz. _That all the
strata of the earth, not only those consisting of calcareous masses, but
others superincumbent on these, have had their origin at the bottom
of the sea, by the collection of sand, gravel, shells, coralline, and
crustaceous bodies, and of earths and clays variously mixed, separated,
and accumulated._ He then adds, "Various geological observations
contradict this conclusion. There are many stratified mountains of
argillaceous slate, gneiss, serpentine, jasper, and even marble, in
which either sand, gravel, shells, coralline, or crustaceous bodies are
never, or scarce ever found."
Here our author seems to have deceived himself, by taking a very partial
view of things which should be fully examined, and well understood,
before general conclusions are to be drawn from those appearances; for,
although those particular objects may not be visible in the strata which
he has enumerated, or many others, they are found in those strata which
are either immediately connected and alternated with them, or with
similar strata; something to that purpose I think I have said; and, if
I had not, it certainly requires no deep penetration to have seen this
clear solution of that appearance of those objects not being found in
every particular stratum. He says that those marks of known materials
are never or scarce ever found;--by _scarce ever_ he surely means that
they are sometimes found; but if they shall only _once_ be found, his
argument is lost. I have not drawn my geological conclusion from every
particle in strata being distinguishable, but from there being certain
distinguishable particles in strata, and from our knowing what had been
the former state and circumstances of those distinguished parts.
If every stone or part of a stratum, in which those known objects are
not immediately visible, must be considered as so _many geological
observations that contradict my theory_, (of strata being formed from
the materials of a former earth), then, surely every stone and every
stratum which visibly contains any of those materials, must prove my
theory. But if every stratum, where these are found in any part of it,
is to be concluded as having had its origin at the bottom of the sea;
and, if every concomitant stratum, though not having those objects
visible or sufficiently distinct, must be considered as having had the
same or a similar origin, that pretended contradiction of my theory
comes to no more than this, that every individual stone does not bear
in it the same or equal evidence of that general proposition which
necessarily results from the attentive consideration of the whole,
including every part.
But to see how necessary it is to judge in this manner, not partially,
but upon the whole, we may observe, that there are two ways by which the
visible materials or distinguishable bodies of a former earth, not only
_may_ be rendered invisible in the composition of our present earth,
but _must_ be so upon many occasions. These are, _first_, by mechanical
comminution, which necessarily happens, more or less, in that operation
by which bodies are moved against one another, and thus transported from
the land to the bottom of the deepest seas; _secondly_, by chemical
operations, (whatever these may be, whether the action of water or of
fire, or both), which are also necessarily employed for consolidating
those loose materials, that are to form the rocks and stones of
this earth, and by means of which those materials are to have their
distinguishable shapes affected in all degrees and obliterated.
Therefore, to demand the visible appearance of those materials in every
stratum of the earth, or in every part of a stratum, is no other than to
misunderstand the subject altogether. The geological observations,
which have been thus alleged as contradicting my theory, are stratified
bodies, containing proofs of the general origin which I attribute to the
earth, but proofs which may not always be seen with equal facility as
those which even convince the vulgar.
Our author has surely perplexed himself with what writers of late have
said concerning primitive mountains as they are called, a subject of
deeper search, than is commonly imagined, as I hope to show in the
course of this work. It is an interesting subject of investigation,
as giving us the actual view of those operations of nature which, in
forming my Theory of the Earth, more general principles had led me to
conclude _might be_. But, it is a subject which, I am afraid, will lead
me to give farther offence to our author, however innocent I may be in
giving nothing but what I have from nature.
The reason for saying so is this; I am blamed for having endeavoured
to trace back the operations of this world to a remote period, by the
examination of that which actually appears, contrary, as is alleged,
"to reason, and the tenor of the Mosaic history, thus leading to an
abyss, from which human reason recoils, etc." In a word, (says our
author), "to make use of his own expression, _We find no vestige of
a beginning._ Then this system of successive worlds must have been
eternal." Such is the logic by which, I suppose, I am to be accused of
atheism. Our author might have added, that I have also said--_we see
no prospect of an end_; but what has all this to do with the idea of
eternity? Are we, with our ideas of _time_, (or mere succession), to
measure that of eternity, which never succeeded any thing, and which
will never be succeeded? Are we thus to measure eternity, that boundless
thought, with those physical notions of ours which necessarily limit
both space and time? and, because we see not the beginning of created
things, Are we to conclude that those things which we see have always
been, or been without a cause? Our author would thus, inadvertently
indeed, lead himself into that gulf of irreligion and absurdity into
which, he alleges, I have _boldly plunged_.
In examining this present earth, we find that it must have had its
origin at the bottom of the sea, although our author seems willing to
deny that proposition. Farther, in examining the internal construction
of this stratified and sea-born mass, we find that it had been composed
of the moved materials of a former earth; and, from the most accurate
and extensive examination of those materials, which in many places are
indeed much disguised, we are led necessarily to conclude, that there
had been a world existing, and containing an animal, a vegetable, and a
mineral system. But, in thus tracing back the natural operations which
have succeeded each other, and mark to us the course of time past, we
come to a period in which we cannot see any farther. This, however,
is not the beginning of those operations which proceed in time and
according to the wise economy of this world; nor is it the establishing
of that, which, in the course of time, had no beginning; it is only the
limit of our retrospective view of those operations which have come to
pass in time, and have been conducted by supreme intelligence.
My principal anxiety was to show how the constitution of this world
had been wisely contrived; and this I endeavoured to do, not from
supposition or conjecture, but from its answering so effectually the end
of its intention, viz. the preserving of animal life, which we cannot
doubt of being its purpose. Here then is a world that is not eternal,
but which has been the effect of wisdom or design.
With regard again to the prospective view of the creation, How are we to
see the end of that wise system of things which so properly fulfils the
benevolent intention of its maker,--in giving sustenance to the animal
part, and information to intellectual beings, who, in these works of
nature, read what much concerns their peace of mind,--their intellectual
happiness? What then does our author mean, in condemning that
comprehensive view which I have endeavoured to take of nature? Would he
deny that there is to be perceived wisdom in the system of this world,
or that a philosopher, who looks into the operations of nature, may not
plainly read the power and wisdom of the Creator, without recoiling, as
he says, from the abyss? The abyss, from which a man of science should
recoil, is that of ignorance and error.
I have thus shown, that, from not perceiving the wise disposition of
things upon the surface of this earth for the preservation of vegetable
bodies, our author has been led to deny the necessary waste of the
present earth, and the consequent preparation of materials for the
construction of another; I have also shown, that he denies the origin
which I had attributed to the stratified parts of this earth, as having
been the collection of moving materials from a former earth; and now
I am come to consider the professed purpose of this paper, viz. the
examination of solid stony substances which we find in those strata
of our earth, as well as in more irregular masses. Here, no doubt, my
theory would have been attacked with greater success, had our author
succeeded in pointing out its error with regard to the original
composition of those indurated bodies, to which I ascribe fusion as the
cause of their solidity. For, if we should, according to our author's
proposition, consider those consolidated bodies as having been
originally formed in that solid state, here the door might be shut
against any farther investigation;--But to what purpose?--Surely not to
refute my theory, but to explode every physical inquiry farther on the
subject, and thus to lead us back into the science of darkness and of
scepticism. But let us proceed to see our author's sentiments on this
subject.
As I had proved from matter of fact, or the actual appearances of
nature, that all the strata of the earth had been formed at the bottom
of the sea, by the subsidence of those materials which either come from
the decaying land, or are formed in the sea itself, it was necessary
that I should consider in what manner those spongy or porous bodies of
loose materials, gathered together at the bottom of the sea, could have
acquired that consolidated state in which we find them, now that they
are brought up to our examination. Upon this occasion, our author says,
"The particles which now form the solid parts of the globe need not be
supposed to have originally been either spongy or porous, the interior
parts at the depth of a few miles might have been originally, as at
present, a solid mass." If, indeed, we shall make that supposition, we
may then save ourselves the trouble of considering either how the strata
of the earth have been formed or consolidated; for, they might have been
so originally. But, how can a naturalist who had ever seen a piece of
Derbyshire marble, or any other shell limestone, make that supposition?
Here are, to the satisfaction of every body of common understanding who
looks at them, bodies which are perfectly consolidated, bodies which
have evidently been formed at the bottom of the sea, and therefore which
were not originally a solid mass. Mr Bertrand, it is true, wrote a book
to prove that those appearances were nothing but a _lusus naturae_; and,
I suppose he meant, with our author, that those strata had been also
originally, as at present, a solid mass.
With regard to the consolidation of strata, that cardinal point for
discussion, our author gives the following answer: "Abstracting from his
own gratuitous hypothesis, it is very easy to satisfy our author on this
head; the concreting and consolidating power in most cases arises from
the mutual attraction of the component particles of stones to each
other." This is an answer with regard to the _concreting power_, a
subject about which we certainly are not here inquiring. Our author,
indeed, has mentioned a _consolidating power_; but that is an improper
expression; we are here inquiring, How the interstices, between the
collected materials of strata, deposited at the bottom of the sea, have
been filled with a hard substance, instead of the fluid water which had
originally occupied those spaces. Our author then continues; "If these
particles leave any interstices, these are filled with water, which no
ways obstructs their solidity when the points of contact are numerous;
hence the decrepitation of many species of stones when heated."
If I understand our author's argument, the particles of stone are, by
their mutual attractions, to leave those hard and solid bodies which
compose the strata, that is to say, those hard bodies are to dissolve
themselves; but, To what purpose? This must be to fill up the
interstices, which we must suppose occupied by the water. In that case,
we should find the original interstices filled with the substances which
had composed the strata, and we should find the water translated into
the places of those bodies; here would be properly a transmutation, but
no consolidation of the strata, such as we are here to look for, and
such as we actually find among those strata. It may be very easy for
our author to form those explanations of natural phenomena; it costs
no tedious observation of facts, which are to be gathered with labour,
patience, and attention; he has but to look into his own fancy, as
philosophers did in former times, when they saw the abhorrence of a
vacuum and explained the pump. It is thus that we are here told the
consolidation of strata _arises from the mutual attraction of the
component particles of stones to each other_; the power, by which the
particles of solid stony bodies retain their places in relation to each
other, and resist separation from the mass, may, no doubt, be properly
enough termed their mutual attractions; but we are not here inquiring
after that power; we are to investigate the power by which the particles
of hard and stony bodies had been separated, contrary to their mutual
attractions, in order to form new concretions, by being again brought
within the spheres of action in which their mutual attractions might
take place, and make them one solid body. Now, to say that this is by
their mutual attraction, is either to misunderstand the proper question,
or to give a most preposterous answer.
It is not every one who is fit to reason with regard to abstract general
propositions; I will now, therefore, state a particular case, in
illustration of that proposition which has been here so improperly
answered. The strata of Derbyshire marbles were originally immense
collections at the bottom of the sea, of calcareous bodies consisting
almost wholly of various fragments of the _entrochi_; and they were then
covered with an indefinite number of other strata under which these
_entrochi_ must have been buried. In this original state of those
strata, I suppose the interstices between the fragments of the coralline
bodies to have been left full of sea-water; at present we find those
interstices completely filled with a most perfectly solid body of
marble; and the question is, whether that consolidating operation
has been the work of water and solution, by our naturalist's termed
infiltration; or if it has been performed, as I have maintained, by the
softening power or heat, or introduction of matter in the fluid state
of fusion. Our author does not propose any other method for the
consolidation of those loose and incoherent bodies, but he speaks of the
_mutual attraction of the component particles of stone to each other_;
Will that fill the interstices between the coralline bodies with solid
marble, as well as consolidate the coralline bodies themselves? or, if
it should, How are those interstices to be thus filled with a substance
perfectly different from the deposited bodies, which is also frequently
the case? But, how reason with a person who, with this consolidation of
strata, confounds the well known operation by which the mortar, made
with caustic lime and sand, becomes a hard body! One would imagine
that he were writing to people of the last age, and not to chemical
philosophers who know so well how that mortar is concreted.
To my argument, That these porous strata are found _consolidated with
every different species of mineral substance_, our author makes the
following observation: "Here the difficulties to the supposition of an
aqueous solution are placed in the strongest light; yet it must be owned
that they partly arise from the author's own gratuitous supposition,
that strata existed at the bottom of the sea previous to their
consolidation;"--gratuitous supposition!--so far from being a
supposition of any kind, it is a self evident proposition; the terms
necessarily imply the conclusion. I beg the readers attention for a
moment to this part of our author's animadversion, before proceeding to
consider the whole; for, this is a point so essential in my theory,
that if it be a gratuitous supposition, as is here asserted, it would
certainly be in vain to attempt to build upon it the system of a world.
That strata may exist, whether at the bottom of the sea, or any other
where, without being consolidated, will hardly be disputed; for, they
are actually found consolidated in every different degree. But, when
strata are found consolidated, at what time is it that we are to suppose
this event to have taken place, or this accident to have happened to
them?--Strata are formed at the bottom of water, by the subsidence or
successive deposits of certain materials; it could not therefore
be during their formation that such strata had been consolidated;
consequently, we must necessarily _conclude_, without any degree of
_supposition_, that _strata had existed at the bottom of the sea
previous to their consolidation_, unless our author can show how they
may have been consolidated previous to their existing.
This then is what our author has termed a gratuitous supposition of
mine, and which, he adds, "is a circumstance which will not be allowed
by the patrons of the aqueous origin of stony substances, as we have
already seen."--I am perfectly at a loss to guess at what is here
alluded to _by having been already seen_, unless it be that which I have
already quoted, concerning things which have been never seen, that
is, _those interior parts of the earth which were originally a solid
mass_.--I have hardly patience to answer such reasoning;--a reasoning
which is not founded upon any principle, which holds up nothing
but chimera to our view, and which ends in nothing that is
intelligible;--but, others, perhaps, may see this dissertation of our
author's in a different light; therefore, it is my duty to analyse the
argument, however insignificant it may seem to me.
I have minutely examined all the stratified bodies which I have been
able, during a lifetime, to procure, both in this country of Britain,
and from all the quarters of the globe; and the result of my inquiry has
been to conclude, that there is nothing among them in an original state,
as the reader will see in the preceding chapter. With regard again to
the masses which are not stratified, I have also given proof that they
are not in their original state, such as granite, porphyry, serpentine,
and basaltes; and I shall give farther satisfaction, I hope, upon that
head, in the course of this work. I have therefore concluded, That there
is nothing to be found in an original state, so far as we see, in the
construction of this earth. But, our author answers, That the interior
parts _might have been in an original state of solidity_.--So might
they have been upon the surface of the earth, or on the summits of our
mountains; but, we are not inquiring What they _might have been_, but
What they truly _are_. It is from this actual state in which the solid
parts of the earth are found, that I have endeavoured to trace back the
different states in which they must have been; and, by generalising
facts, I have formed a theory of the earth. If this be a wrong principle
or manner of proceeding in a physical investigation, or if, proceeding
upon that principle, I have made the induction by reasoning improperly
on any occasion, let this be corrected by philosophers, who may reason
more accurately upon the subject. But to oppose a physical investigation
with this proposition, _that things might have been otherwise_, is to
proceed upon a very different principle,--a principle which, instead of
tending to bring light out of darkness, is only calculated to extinguish
that light which we may have acquired.
I shall afterwards have occasion to examine how far the philosophers,
who attribute to aqueous solution the origin of stony substances, have
proceeded in the same inductive manner of reasoning from effect to
cause, as they ought to do in physical subjects, and not by feigning
causes, or following a false analogy; in the mean time, I am to answer
the objections which have been made to the theory of the earth.
In opposition to the theory of consolidating bodies by fusion, our
author has taken great pains to show, that I cannot provide materials
for such a fire as would be necessary, nor find the means to make it
burn had I those materials. Had our author read attentively my theory he
would have observed, that I give myself little or no trouble about that
fire, or take no charge with regard to the procuring of that power, as I
have not founded my theory on the _supposition_ of subterraneous
fire, however that fire properly follows as a conclusion from those
appearances on which the theory is founded. My theory is founded upon
the general appearances of mineral bodies, and upon this, that mineral
bodies must necessarily have been in a state of fusion. I do not pretend
to prove, demonstratively, that they had been even hot, however that
conclusion also naturally follows from their having been in fusion. It
is sufficient for me to demonstrate, That those bodies must have been,
more or less, in a state of softness and fluidity, without any species
of solution. I do not say that this fluidity had been without heat;
but, if that had been the case, it would have answered equally well the
purpose of my theory, so far as this went to explain the consolidation
of strata or mineral bodies, which, I still repeat, must have been
by simple fluidity, and not by any species of solution, or any other
solvent than that universal one which permeates all bodies, and which
makes them fluid.
Our author has justly remarked the difficulty of fire burning below the
earth and sea. It is not my purpose here to endeavour to remove those
difficulties, which perhaps only exist in those suppositions which are
made on this occasion; my purpose is to show, that he had no immediate
concern with that question, in discussing the subject of the
consolidation which we actually find in the strata of the earth, unless
my theory, with regard to the igneous origin of stony substances, had
proceeded upon the supposition of a subterraneous fire. It is surely one
thing to employ fire and heat to melt mineral bodies, in supposing this
to be the cause of their consolidation, and another thing to acknowledge
fire or heat as having been exerted upon mineral bodies, when it is
clearly proved, from actual appearances, that those bodies had been in
a melted state, or that of simple fluidity. Here are distinctions which
would be thrown away upon the vulgar; but, to a man of science, who
analyses arguments, and reasons strictly from effect to cause, this is,
I believe, the proper way of coming at the truth. If the patrons of
the aqueous origin of stony substances can give us any manner of
scientifical, _i.e._ intelligible investigation of that process, it
shall be attended to with the most rigid impartiality, even by a patron
of the igneous origin of those substances, as he wishes above all things
to distinguish, in the mineral operations, those which, on the one hand,
had been the effect of water, from those which, on the other hand, had
been the immediate effect of fire or fusion;--this has been my greatest
study. But, while mineralists or geologists give us only mere opinions,
What is science profited by such inconsequential observations, as are
founded upon nothing but our vulgar notions? Is the figure of the
earth, _e.g._ to be doubted, because, according to the common notion of
mankind, the existence of an antipod is certainly to be denied?
I am not avoiding to meet that question with regard to the providing
of materials for such a mineral fire as may be required; no question I
desire more to be asked to resolve; but it must not be in the manner
that our author has put that question. He has included this supposed
difficulty among a string of other arguments by which he would refute my
theory with regard to the igneous origin of stony substances, as if I
had made that fire a necessary condition or a principle in forming my
theory of consolidation. Now, it is precisely the reverse; and this is
what I beg that mineral philosophers will particularly attend to, and
not give themselves so much unnecessary trouble, and me so disagreeable
a talk. I have proved that those stony substances have been in the fluid
state of fusion; and from this, I have inferred the former existence of
an internal heat, a subterraneous fire, or a certain cause of fusion by
whatever name it shall be called, and by whatever means it shall have
been procured. The nature of that operation by which strata had been
consolidated, like that by which they had been composed, must, according
to my philosophy, be decided by ocular demonstration; from examining the
internal evidence which is to be found in those bodies as we see them in
the earth; because the consolidating operation is not performed in our
sight, no more than their stratification which our author has also
denied to have been made, as I have said, by the deposits of materials
at the bottom of the sea. Now, with regard to the means of procuring
subterraneous fire, if the consolidating operation shall be thus decided
to have been that of fusion, as I think I have fully shown, and for
which I have as many witnesses, perhaps as there are mineral bodies,
then our author's question, (how I am to procure a fire) in the way that
he has put it, as an argument against the fusion, would be at least
useless; for, though I should here confess my ignorance with regard to
the means of procuring fire, the evidence of the melting operation, or
former fluidity of those mineral bodies, would not be thereby in the
least diminished. If again no such evidence for the fusion of those
bodies shall appear, and it be concluded that they had been consolidated
by the action of water alone, as our author seems inclined to maintain,
he would have no occasion to start difficulties about the procuring of
fire, in order to refute a theory which then would fall of itself as
having no foundation.
But in order to see this author's notion of the theory which he is here
examining, it may be proper to give a specimen of his reasoning upon
this subject of heat. He says, "That my supposition of heat necessary
for consolidating strata is _gratuitous_, not only because it is
unnecessary, as we have already shown, but also because it is
inconsistent with our author's own theory." Let us now consider those
two propositions. _First_, it is unnecessary, _as we have already
shown_;--I have already taken particular notice of what we have been
shown on this occasion, viz. That the earth at a certain depth _may
have been originally in a solid state_; and, that, where it is to be
consolidated, this is done by the _mutual attraction of the stony
particles_. Here is all that we have been shown to make subterraneous
heat, for the consolidation of strata, unnecessary; and now I humbly
submit, if this is sufficient evidence, that mineral heat is a
gratuitous supposition.
Secondly, "_it is inconsistent with our author's own theory._" Here
I would beg the readers attention to the reasoning employed on
this occasion. He says, "according to him these strata, which were
consolidated by heat, were composed of materials gradually worn from a
preceding continent, casually and successively deposited in the sea;
Where then will he find, and how will he suppose, to have been formed
those enormous masses of sulphur, coal, or bitumen, necessary to produce
that immense heat necessary for the fusion of those vast mountains of
stone now existing? All the coal, sulphur, and bitumen, now known, does
not form the 100,000 part of the materials deposited within one quarter
of a mile under the surface of the earth; if, therefore, they were, as
his hypothesis demands, carried off and mixed with the other materials,
and not formed in vast and separate collections, they could never
occasion, by their combustion, a heat capable of producing the smallest
effect, much less those gigantic effects which he requires."
Here is a comparative estimate formed between two things which have not
any necessary relation; these are, the quantity of combustible materials
found in the earth, on the one hand, and the quantity which is supposed
necessary for hardening and consolidating strata, on the other. If this
earth has been consolidated by the burning of combustible materials,
there must have been a superfluity, so far as there is a certain
quantity of these actually found unconsumed in the strata of the earth.
Our author's conclusion is the very opposite; let us then see how he
is to form his argument, by which he proves that the supposition of
subterraneous heat for hardening bodies is gratuitous and unnecessary,
as being inconsistent with my theory.
According to my theory, the strata of this earth are composed of the
materials which came from a former earth; particularly these combustible
strata that contain plants which must have grown upon the land. Let
us then suppose the subterraneous fire supplied with its combustible
materials from this source, the vegetable bodies growing upon the
surface of the land. Here is a source provided for the supplying of
mineral fire, a source which is inexhaustible or unlimited, unless
we are to circumscribe it with regard to time, and the necessary
ingredients; such as the matter of light, carbonic matter, and the
hydrogenous principle. But it is not upon any deficiency of this kind
that our author founds his estimate; it is upon the superfluity of
combustible materials which is actually found in this earth, after it
had been properly consolidated and raised above the surface of the sea.
This is a method of reasoning calculated to convince only those who do
not understand it; it is as if we should conclude that a person had died
of want, because he had left provision behind him. Our author certainly
means to employ nothing but the combustible minerals of the present
earth, in feeding the subterraneous fire which is to concoct a future
earth; in that case, I will allow that his provision is deficient; but
this is not my theory.
I am not here to enter into any argument concerning subterraneous
fire; the reader will find, in the foregoing theory, my reasons for
concluding, That subterraneous fire had existed previous to, and ever
since, the formation of this earth,--that it exists in all its vigour
at this day,--that there is, in the constitution of this earth, a
superfluity of subterranean heat,--and that there is wisely provided a
proper remedy against any destructive effect to the system, that might
arise from that superabundant provision of this necessary agent. Had our
author attended to the ocular proof that we have of the actual existence
of subterraneous fire, and to the physical demonstrations which I have
given of the effects of heat in melting mineral bodies, he must have
seen that those arguments of his, with regard to the difficulty or
impossibility of procuring that fire, can only show the error of his
reasoning. I am far from supposing that my theory may be free from
inconsistency or error; I am only maintaining that, in all his confident
assertions, this author has not hitherto pointed any of these out.
So far I have answered our author's objections as to consolidation, and
I have given a specimen of his reasoning upon that subject; but with
regard to my Theory of the Earth, although simple fluidity, without
heat, would have answered the purpose of consolidating strata that had
been formed at the bottom of the sea, it was necessary to provide a
power for raising those consolidated strata from that low place to the
summits of the continents; now, in supposing heat to be the cause of
that fluidity which had been employed in the consolidation of those
submarine masses, we find a power capable of erecting continents, and
the only power, so far as I see, which natural philosophy can employ
for that purpose. Thus I was led, from the consolidation of strata, to
understand the nature of the elevating power, and, from the nature of
that power, again to understand the cause of fluidity by which the rocks
and stones of this earth had been consolidated.
Having thus, without employing the evidence of any fire or _burning_,
been necessarily led to conclude an extreme degree of heat exerted in
the mineral regions, I next inquire how far there are any appearances
from whence we might conclude whether that active subterraneous power
still subsists, and what may be the nature of that power. When first I
conceived my theory, naturalists were far from suspecting that basaltic
rocks were of volcanic origin; I could not then have employed an
argument from these rocks as I may do now, for proving that the fires,
which we see almost daily issuing with such force from volcanos, are a
continuation of that active cause which has so evidently been exerted
in all times, and in all places, so far as have been examined of this
earth.
With regard to the degree of heat in that subterraneous fire, our
author, after proving that combustible materials would not burn in the
mineral regions, then says, that suppose they were to burn, this would
be "incapable of forming a heat even equal to that of our common
furnaces, as Mr Dolomieu has clearly shown to be the case with respect
to volcanic heat." The place to which he alludes, I believe to be that
which I have quoted from the Journal de Physique (Part I. page 139) to
which I here beg leave to refer the reader. After what I have already
said, this subject will appear to be of little concern to me; but, it
must be considered, that my object, in these answers, is not so much to
justify the theory which I have given, as it is to remove that prejudice
which, to those who are not master of chemical and mineral subjects,
will naturally arise from the opinion or authority of a scientific man,
and a chemist; therefore, I think it my business to show how much he
has misconceived the matter which he treats of, and how much he
misunderstands the subject of my theory.
Mr Dolomieu alleges that the volcanic fire operates in the melting of
bodies, not by the intensity of its heat, which is the means employed by
us in our operations, but in the long continuance of its action. But in
that proposition, this philosopher is merely giving us his opinion; and,
this opinion our author mistakes, I suppose, for the fact on which that
opinion had been (perhaps reasonably) founded. The reader will see, in
the place quoted, or in the _avant-propos_ to his _Mémoire sur les Iles
Ponces_, the fact to be this; That the Chevalier Dolomieu finds those
bodies which we either cannot melt in our fires, or which we cannot melt
without changing them by calcination and vitrification, he finds, I say,
these substances had actually been melted with his lavas; he also finds
those substances, which are necessarily dissipated in our fires, to have
been retained in those melted mineral substances. Had our author quoted
the text, instead of giving us his own interpretation, he could not have
offered a stronger confirmation of my theory; which certainly is not
concerned with the particular intensity of volcanic fire, and far less
with what may be the opinion of any naturalist with regard to that
intensity, but only with the efficacy of that volcanic heat for the
melting of mineral substances. Now this efficacy of volcanic fire, so
far as we are to found upon the authority given on this occasion, is
clearly confirmed by the observations of a most intelligent mineralist,
and one who is actually a patron of the opposite theory to that which I
have given. This being the state of the case, Must I not conclude, that
our author has misunderstood the subject, and that he has been led to
give a mutilated opinion of Mr Dolomieu, in order to refute my theory,
when either the entire opinion, or the facts on which the opinion had
been founded, would have confirmed it?
I have thus endeavoured to put in its true light a species of reasoning,
which, while it assumes the air and form of that inductive train of
thought employed by men of science for the investigation of nature, is
only fit to mislead the unwary, and, when closely examined, will appear
to be inconsequential or unfounded. How mortifying then to find, that
one may be employed almost a lifetime in generalising the phenomena of
nature, or in gathering an infinity of evidence for the forming of a
theory, and that the consequence of this shall only be to give offence,
and to receive reproach from those who see not things in the same
light!--While man has to learn, mankind must have different opinions.
It is the prerogative of man to form opinions; these indeed are often,
commonly I may say, erroneous; but they are commonly corrected, and it
is thus that truth in general is made to appear.
I wrote a general Theory for the inspection of philosophers, who
doubtless will point out its errors; but this requires the study of
nature, which is not the work of a day; and, in this political age, the
study of nature seems to be but little pursued by our philosophers. In
the mean time, there are, on the one hand, sceptical philosophers, who
think there is nothing certain in nature, because there is misconception
in the mind of man; on the other hand, there are many credulous
amateurs, who go to nature to be entertained as we go to see a
pantomime: But there are also superficial reasoning men, who think
themselves qualified to write on subjects on which they may have read
in books,--subjects which they may have seen in cabinets, and which,
perhaps, they have just learned to name; without truly knowing what they
see, they think they know those regions of the earth which never can be
seen; and they judge of the great operations of the mineral kingdom,
from having kindled a fire, and looked into the bottom of a little
crucible.
In the Theory of the Earth which was published, I was anxious to warn
the reader against the notion that subterraneous heat and fusion could
be compared with that which we induce by our chemical operations
on mineral substances here upon the surface of the earth; yet,
notwithstanding all the precaution I had taken, our author has bestowed
four quarto pages in proving to me, that our fires have an effect upon
mineral substances different from that of the subterraneous power which
I would employ.
He then sets about combining metals with sulphur in the moist way, as if
that were any more to his purpose than is the making of a stalactite for
the explanation of marble. Silver and lead may be sulphurated, as he
says, with hepatic gas; but, Has the sulphurated solid ores of those
metals, and that of iron, been formed in the moist way, as in some
measure they may be by the fusion of our fires? But, even suppose that
this were the case, Could that explain a thousand other appearances
which are inconsistent with the operation of water? We see aerated lead
dissolved in the excavations of our mines, and again concreted by the
separation of the evaporated solvent, in like manner as stalactical
concretions are made of calcareous earth; but, so far from explaining
mineral appearances, as having had their concretions formed in the same
manner, here is the most convincing argument against it; for, among the
infinite variety of mineral productions which we find in nature, Why
does no other example of aqueous concretion ever occur upon the surface
of the earth except those which we understand so well, and which we
therefore know cannot be performed in the bodies of strata not exposed
to the evaporation of the solvent, a circumstance which is necessary.
I have given a very remarkable example of mineral fusion, in reguline
manganese, (as the reader will see in page 68.) It is not that this
example is more to the purpose of my theory than what may be found in
every species of stone; but this example speaks so immediately to
the common sense of mankind, (who are often convinced by a general
resemblance of things, when they may not see the force of demonstration
from an abstract principle) that I thought it deserved a place on that
account, as well as being a curious example, But more particularly to my
antagonist, who has been pleased (very improperly indeed) to try some
part of my theory in the fire, here is an example which should have
been absolutely in point, and without any manner of exception:--Has he
acknowledged this?--No; he has, on the contrary, endeavoured to set this
very example aside.
On this occasion, he says, "Manganese has been found in a reguline state
by M. de la Peyrouse, and in small grains, as when produced by fire.
True; but it was mixed with a large quantity of iron, which is often,
found in that form without any suspicion of fusion. A fire capable of
melting quartz might surely produce it in larger masses." We have here
a kind of two arguments, for removing the effect of this example; and I
shall consider them separately.
The first of these is, the not being suspected of having been in fusion;
now, if this were to be admitted as an argument against the igneous
origin of stony substances, it might have superseded the adducing of any
other, for it is applicable perhaps to every mineral; but we must here
examine the case more minutely.
This argument, of the manganese being in a mine of iron, if I understand
it rightly, amounts to this, that, as iron ore is not suspected of
having been melted, therefore, we should doubt the manganese having been
so. If this be our author's meaning, it is not the fair conclusion which
the case admits of; for, so far as the manganese appears evidently to
have been in a melted state, the iron ore should be _suspected_ of
having been also in fusion, were there no other evidence of that fact.
In science, however, it is not suspicion that should be employed in
physical investigation; the question at present is; If the phenomena of
the case correspond to the conclusion which the intelligent mineralist,
who examined them, has formed? and, to this question, our author gives
no direct answer. He says, _iron is often found in that form without any
suspicion of fusion_. This is what I am now to answer.
The form in which the manganese appears is one of the strongest proofs
of those masses having been in fusion; and, if iron should ever be found
in that form, it must give the same proof of mineral fusion as this
example of manganese; let us then see the nature of this evidence. The
form of the manganese is that of a fluid body collecting itself into a
spherical figure by the cohesion or attraction of its particles, so far
as may be admitted by other circumstances; but, being here refilled by
the solid part on which it rests, this spherical body is flattened by
the gravitation of its substance. Now here is a regular form, which
demonstrates the masses to have been in the state of fusion; for, there
is no other way in which that form of those reguline masses could have
been induced.
There now remains to be considered what our author has observed
respecting the intensity of the fire and size of the masses. "A
fire capable of melting quartz might surely produce it (meaning the
manganese) in larger masses." M. de la Peyrouse says, that those masses
were in all respects as if formed by art, only much larger, as the
powers of nature exceed those of our laboratories. What then is it that
is here meant to be disputed? We are comparing the operation of nature
and that of art, and these are to be judged of by the product which we
examine; but the quantity, in this case, or the size of the masses,
makes no part of the evidence, and therefore is here most improperly
mentioned by our author. With regard again to the nature of the fire by
which the fusion had been produced, he is much mistaken if he imagines
that the reduction of the reguline or metallic manganese depends upon
the intensity of the heat; it depends upon circumstances proper for the
separation of the oxygenating principle from the calx, in like manner as
the calcination of calcareous spar must depend upon circumstances proper
for allowing the separation of the carbonic acid or fixed air.
But do not let us lose sight of our proper subject, by examining things
foreign or not so immediately to the purpose. We are only inquiring if
those flattened spheres of native manganese had been formed by water, or
if it were by fusion; for, our author agrees that there is no other way.
Why then does he endeavour to evade giving a direct answer, and fly away
to consider the quantity of the product, as if that had any thing to do
with, the question, or as if that quantity were not sufficient, neither
of which is the case. In short, our author's whole observation, on this
occasion, looks as if he were willing to destroy, by insinuation, the
force of an argument which proves the theory of mineral fusion; and that
he wishes to render doubtful, by a species of sophistry, what in fair
reasoning he cannot deny.
Our author has written upon the subject of phlogiston; one would suppose
that he should be well acquainted with inflammable bodies at least; let
us see then what he has to observe upon that subject. He quotes from
my Theory, that spar, quartz, pyrites, crystallised upon or near each
other, and adhering to coal, or mixed with bitumen, etc. are found;
circumstances that cannot be explained in the hypothesis of solution
in the moist way.--He then answers;--"Not exactly, nor with certainty;
which is not wonderful: But they are still less explicable in the
hypothesis of dry solution, as must be apparent from what has been
already said. How coal, an infusible substance, could be spread into
strata by mere heat, is to me incomprehensible."--It is only upon the
last sentence that I am here to remark: This, I believe, will be a
sufficient specimen of our author's understanding, with regard at least
to my Theory which he is here examining.
The reader will see what I have said upon the subject of coal, by
turning back to the second section of the preceding chapter. I had given
almost three quarto pages upon that subject, endeavouring to explain how
all the different degrees of _infusibility_ were produced, by means of
heat and distillation, in strata which had been originally more or less
oily, bituminous, and _fusible_; and now our author says, that it is
incomprehensible to him, how coal, _an infusible substance_, could be
spread into strata by mere heat.--So it truly may, either to him or to
any other person; but, it appears to me almost as incomprehensible, how
a person of common understanding should read my Dissertation, and impute
to it a thing so contrary to its doctrine.
Nothing can better illustrate the misconceived view that our author
seems to have taken of the two opposite theories, (_i. e_. of
consolidation by means of heat, and by means of water alone,) than
his observation upon the case of mineral alkali. To that irrefragable
argument (which Dr Black suggested) in proof of this substance having
been in a state of fusion in the mineral regions, our author makes the
following reply; "What then will our author say of the vast masses
of this salt which are found with their full quantity of water of
crystallization?"--There is in this proposition, insignificant as it may
seem, a confusion of ideas, which it certainly cannot be thought worth
while to investigate; but, so far as the doctrine of the aqueous theory
may be considered as here concerned, it will be proper that I should
give some answer to the question so triumphantly put to me.
Our author is in a mistake in supposing that Dr Black had written any
thing upon the subject; he had only suggested the argument of this
example of mineral alkali to me, as I have mentioned; and, the use I
made of that argument was to corroborate the example I had given of sal
gem. If, therefore, our author does not deny the inference from the
state of that mineral alkali, his observation upon it must refer to
something which this other example of his is to prove on the opposite
side, or to support the aqueous instead of the igneous theory; and, this
is a subject which I am always willing to examine in the most impartial
manner, having a desire to know the true effect of aqueous solution in
the consolidation of mineral bodies, and having no objection to allow it
any thing which it can possibly produce, although denying that it can do
every thing, as many mineralists seem to think.
The question, with regard to this example of our author's of a mineral
alkali with its water of crystallization, must be this, Whether those
saline bodies had been concreted by the evaporation of the aqueous
solvent with which they had been introduced, or by the congelation of
that saline substance from a fluid state of fusion; for, surely, we are
not to suppose those bodies to have been created in the place and state
in which we find them. With regard to the evaporation or separation
of the aqueous solvent, this may be easily conceived according to the
igneous theory; but, the aqueous theory has not any means for the
producing of that effect in the mineral regions, which is the only place
we are here concerned with. Therefore, this example of a concreted body
of salt, whatever it may prove in other respects, can neither diminish
the evidence of my Theory with regard to the igneous origin of stony
substances, nor can it contribute to support the opposite supposition of
an aqueous origin to them.
But to show how little reason our author had for exulting in that
question which he so confidently proposed in order to defeat my
argument, let us consider this matter a little farther. I will for a
moment allow the aqueous theory to have the means for separating
the water from the saline solution, and thus to concrete the saline
substance in the bowels of the earth; this concretion then is to be
examined with a view to investigate the last state of this body, which
is to inform us with regard to those mineral operations. But, our author
has not mentioned whether those masses appear to have been crystallised
from the aqueous solution, or if they appear to have been congealed from
the melted state of their _aqueous fusion_.--Has he ever thought of
this? Now this is so material a point in the view with which that
example has been held out to us, that, without showing that this salt
had crystallised from the solution, he has no right to employ it as an
example; and if, on the other hand, it should appear to have simply
congealed from the state of aqueous fusion, then, instead of answering
the purpose for which our author gave it, it would refute his
supposition, as certainly as the example which I have given.
So far I have reasoned upon the supposition of this alkali, with its
water of crystallization, being truly a mineral concretion; but, I see
no authority for such a supposition: It certainly may be otherwise;
and, in that case, our author would have no more right to give it as an
example in opposition to Dr Black's argument, than he would have to give
the crystallization of sea-salt, on Turk's Island, in opposition to the
example which I had given, of the salt rock, at Northwych in Cheshire,
having been in the state of fusion.
It certainly was incumbent on our author to have informed us, if those
masses of salt were found in, what may be properly termed, their mineral
state; or, if the state in which they are found at present had been
produced by the influences of the atmosphere, transforming that saline
substance from its mineral state, as happens upon so many other
occasions; I am inclined to suspect that this last is truly the case.
It may be thought illiberal in me to suppose a natural philosopher thus
holding out an example that could only serve to lead us into error, or
to mislead our judgment with regard to those two theories which is the
subject of consideration. This certainly would be the case, almost
on any other occasion; but, when I find every argument and example,
employed in this dissertation, to be either unfounded or misjudged,
Whether am I to conclude our author, on this occasion, to be consistent
with himself, or not?
I have but one article more to observe upon. I had given, as I thought,
a kind of demonstration, from the internal evidence of the stone, that
granite had been in the fluid state of fusion, and had concreted by
crystallization and congelation from that melted state. This no doubt
must be a stumbling block to those who maintain that granite mountains
are the primitive parts of our earth; and who, like our author, suppose
that "things may have been originally, as at present, in a solid state."
It must also be a great, if not an invincible obstacle in the way of the
aqueous theory, which thus endeavours to explain those granite veins
that are found traversing strata, and therefore necessarily of a
posterior formation.
To remove that obstacle in the way of the aqueous theory, or to carry
that theory over the obstacle which he cannot remove, our author
undertakes to refute my theory with regard to the igneous origin of
stony substances, by giving an example of granite formed upon the
surface of the earth by means of water, or in what is called the
moist way; and he closes his Dissertation with this example as an
_experimentum crucis_. It is therefore necessary that I take this
demonstration of our author into particular consideration; for, surely,
independent of our controversy, which is perhaps of little moment, here
is the most interesting experiment, as it is announced, that mineralogy
could be enriched with.
"To close this controversy," says our author, "I shall only add,
that granite, recently formed in the moist way, has been frequently
found."--Of that remarkable event, however, he has selected only one
example. This is to be found upon the Oder; and the authority upon which
our author has given it, is that of Lasius Hartz.
The formation of a granite stone, from granite sand, by means of water,
is inconsistent with our chemical knowledge of those mineral substances
which constitute that stone; it is repugnant to the phenomena which
appear from the inspection of the natural bodies of this kind; and it
is directly contrary to the universal experience in granite countries,
where, instead of any thing concreting, every thing is going into
decay, from the loose stones and sand of granite, to the solid rock and
mountains which are always in a state of degradation. Therefore, to have
any credit given to such a story, would require the most scientific
evidence in its favour. Now, in order that others may judge whether this
has been the case in this example, I will transcribe what our author has
said upon the subject; and then I will give the view in which it appears
to me.
He says, "a mole having been constructed in the Oder in the year 1723,
350 feet long, 54 feet in height, 144 feet broad at bottom, and 54 at
the top, its sides only were granite, without any other cement than
moss; the middle space was entirely filled with granite sand. In a short
time this concreted into a substance so compact as to be impenetrable by
water."--Here is an example, according to our author, of _granite formed
in the moist way_. But now, I must ask to see the evidence of that fact;
for, from what our author has told us, I do not even see reason to
conclude that there was the least concretion, or any stone formed at
all. A body of sand will be _so compacted as to be impenetrable by
water_, with the introduction of a very little mud, and without any
degree of concretion; muddy water, indeed, cannot be made to pass
through such a body without compacting it so; and this every body finds,
to their cost, who have attempted to make a filter of that kind.
But I shall suppose Lasius has informed our author that there had been
a petrifaction in this case; and, before I admit this example of the
formation of granite, I must ask what sort of a granite it was;--whether
of two, three, or four ingredients; and, how these were disposed. If,
again, it were not properly a granite, but a stone formed of granite
sand, What is the cementing substance?--Is it quartz, felt-spar, mica,
or schorl?--or, Was it calcareous? If our author knows any thing about
these necessary questions, Why has he not informed us, as minutely as
he has done with regard to the dimensions of the mole, with which we
certainly are less concerned? If, again, he knows no more about the
matter than what he has informed us of, he must have strangely imposed
upon himself, to suppose that he was giving us an example of the
_formation of granite in the moist way_, when he has only described an
effectual way of retaining water, by means of sand and mud.
CHAP. III.
Of Physical Systems, and Geological Theories, in general.
In the first chapter I have given a general theory of the earth,
with such proofs as I thought were sufficient for the information of
intelligent men, who might satisfy themselves by examining the facts on
which the reasoning in that theory had been founded.
In the second chapter, I have endeavoured to remove the objections which
have been made to that theory, by a strenuous patron of the commonly
received opinion of mineralogists and geologists,--an opinion which, if
not diametrically opposite, differs essentially from mine. But now I am
to examine nature more particularly, in order to compare those different
opinions with the actual state of things, on which every physical theory
must be founded. Therefore, the opinions of other geologists should be
clearly stated, that so a fair comparison may be made of theories which
are to represent the system of this earth.
Now, if I am to compare that which I have given as a theory of the
earth, with the theories given by others under that denomination, I
find so little similarity, in the things to be compared, that no other
judgment could hence be formed, perhaps, than that they had little or no
resemblance. I see certain treatises named Theories of the Earth; but, I
find not any thing that entitles them to be considered as such, unless
it be their endeavouring to explain certain appearances which are
observed in the earth. That a proper theory of the earth should explain
all those appearances is true; but, it does not hold, conversely, that
the explanation of an appearance should constitute a theory of the
earth. So far as the theory of the earth shall be considered as the
philosophy or physical knowledge of this world, that is to say, a
general view of the means by which the end or purpose is attained,
nothing can be properly esteemed such a theory unless it lead, in some
degree, to the forming of that general view of things. But now, let us
see what we have to examine in that respect.
We have, first, Burnet's Theory of the Earth. This surely cannot be
considered in any other light than as a dream, formed upon the poetic
fiction of a golden age, and that of iron which had succeeded it; at the
same time, there are certain appearances in the earth which would, in a
partial view of things, seem to justify that imagination. In Telliamed,
again, we have a very ingenious theory, with regard to the production of
the earth above the surface of the sea, and of the origin of those
land animals which now inhabit that earth. This is a theory which has
something in it like a regular system, such as we might expect to find
in nature; but, it is only a physical romance, and cannot be considered
in a serious view, although apparently better founded than most of that
which has been wrote upon the subject.
We have then a theory of a very different kind; this is that of the
Count de Buffon. Here is a theory, not founded on any regular system,
but upon an irregularity of nature, or an accident supposed to have
happened to the sun. But, are we to consider as a theory of the earth,
an accident by which a planetary body had been made to increase the
number of these in the solar system? The circumvolution of a planetary
body (allowing it to have happened in that manner) cannot form the
system of a world, such as our earth exhibits; and, in forming a theory
of the earth, it is required to see the aptitude of every part of this
complicated machine to fulfil the purpose of its intention, and not to
suppose the wise system of this world to have arisen from, the cooling
of a lump of melted matter which had belonged to another body. When
we consider the power and wisdom that must have been exerted in the
contriving, creating, and maintaining this living world which sustains
such a variety of plants and animals, the revolution of a mass of dead
matter according to the laws of projectiles, although in perfect wisdom,
is but like a unite among an infinite series of ascending numbers.
After the theory of that eloquent writer, founded on a mere accident, or
rather the error of a comet which produced the beautiful system of this
world, M. de Luc, in his Theory of the earth, has given us the history
of a disaster which befell this well contrived world;--a disaster which
caused the general deluge, and which, without a miracle, must have
undone a system of living beings that are so well adapted to the present
state of things. But, surely, general deluges form no part of the theory
of the earth; for, the purpose of this earth is evidently to maintain
vegetable and animal life, and not to destroy them.
Besides these imaginary great operations in the natural history of this
earth, we have also certain suppositions of geologists and mineralists
with regard to the effect of water, for explaining to us the
consolidation of the loose materials of which the strata of the earth
had been composed, and also for producing every other appearance, or any
which shall happen to occur in the examination of the earth, and require
to be explained. That this is no exaggerated representation, and
that this is all we have as a theory, in the suppositions of those
geologists, will appear from the following state of the case.
They suppose water the agent employed in forming the solid bodies of the
earth, and in producing those crystallised bodies which appear in
the mineral kingdom. That this is a mere supposition will appear by
considering; first, that they do not know how this agent water is to
operate in producing those effects; nor have they any direct proof
of the fact which is alleged, from a very fallaceous analogy; and,
secondly, that they cannot tell us where this operation is to be
performed. They cannot say that it is in the earth above the level of
the sea: for, the same appearances are found as deep as we can examine
below that level; besides, we see that water has the opposite effect
upon the surface of the earth, through which it percolates dissolving
soluble substances, and thus resolving solid bodies in preparing soil
for plants. If, again, it be below the level of the sea, that strata of
the earth are supposed to be consolidated by the infiltration of that
water which falls from the heavens; this cannot be allowed, so far as
whatever of the earth is bibulous, in that place, must have been always
full of water, consequently cannot admit of that supposed infiltration.
But allowing those suppositions to be true, there is nothing in them
like a theory of the earth,--a theory that should bring the operations
of the world into the regularity of ends and means, and, by generalizing
these regular events, show us the operation of perfect intelligence
forming a design; they are only an attempt to show how certain things,
which we see, have happened without any perceivable design, or without
any farther design than this particular effect which we perceive. If we
believe that there is almighty power, and supreme wisdom employed for
sustaining that beautiful system of plants and animals which is so
interesting to us, we must certainly conclude, that the earth, on which
this system of living things depends, has been constructed on principles
that are adequate to the end proposed, and procure it a perfection which
it is our business to explore. Therefore, a proper system of the earth
should lead us to see that wise contraction, by which this earth is made
to answer the purpose of its intention and to preserve itself from every
accident by which the design of this living world might be frustrated as
this world is an active scene, or a material machine moving in all its
parts, we must see how this machine is so contrived, as either to have
those parts to move without wearing and decay, or to have those parts,
which are wasting and decaying, again repaired.
A rock or stone is not a subject that, of itself, may interest a
philosopher to study; but, when he comes to see the necessity of those
hard bodies, in the constitution of this earth, or for the permanency
of the land on which we dwell, and when he finds that there are means
wisely provided for the renovation of this necessary decaying part, as
well as that of every other, he then, with pleasure, contemplates this
manifestation of design, and thus connects the mineral system of
this earth with that by which the heavenly bodies are made to move
perpetually in their orbits. It is not, therefore, simply by seeing the
concretion of mineral bodies that a philosopher is to be gratified in
his his intellectual pursuit, but by the contemplation of that system in
which the necessary resolution of this earth, while at present it serves
the purpose of vegetation, or the fertility of our soil, is the very
means employed in furnishing the materials of future land.
It is such a view as this that I have endeavoured to represent in the
theory which I have given. I have there stated the present situation of
things, by which we are led to perceive a former state; and, from that
necessary progress of actual things, I have concluded a certain system
according to which things will be changed, without any accident or
error. It is by tracing this regular system in nature that a philosopher
is to perceive the wisdom with which this world has been contrived; but,
he must see that wisdom founded upon the aptitude of all the parts to
fulfil the intention of the design; and that intention is to be deduced
from the end which is known to be attained. Thus we are first to reason
from effect to cause, in seeing the order of that which has already
happened; and then, from those known causes, to reason forwards, so as
to conceive that which is to come to pass in time. Such would be the
philosophy of this earth, formed by the highest generalisation
of phenomena, a generalisation which had required the particular
investigation of inductive reasoning.
That no such theory as this, founded upon water as an agent operating in
the changes of this earth, has yet appeared, will, I believe be easily
allowed. With regard again to fire as an agent in the mineral operations
of this earth, geologists have formed no consistent theory. They see
volcanoes in all the quarters of the globe, and from those burning
mountains, they conjecture other mountains have been formed. But a
burning mountain is only a matter of fact; and, they have not on this
formed any general principle, for establishing what may be called a
theory of the earth. Those who have considered subterraneous fires as
producing certain effects, neither know how these have been procured,
nor do they see the proper purpose for which they are employed in the
system of this world. In this case, the agent fire is only seen as
a destructive element, in like manner as deluges of water have been
attributed by others to changes which have happened in the natural state
of things. These operations are seen only as the accidents of nature,
and not as part of that design by which the earth, which is necessarily
wasted in the operations of the world, is to be repaired.
So far from employing heat or subterraneous fire as an agent in the
mineral operations of the earth, the volcanic philosophers do not
even attempt to explain upon that principle the frequent nodules of
calcareous, zeolite, and other spatose and agaty substances, in those
basaltic bodies which they consider as lavas. Instead then of learning
to see the operation of heat as a general principle of mineral
consolidation and crystallization, the volcanic philosophers endeavour
to explain those particular appearances, which they think inconsistent
with fusion, by aqueous infiltration, no otherwise than other
mineralists who do not admit the igneous origin of those basaltic
bodies. Thus, that great agent, subterraneous heat, has never been
employed by geologists, as a general principle in the theory of the
earth; it has been only considered as an occasional circumstance, or as
the accident of having certain mineral bodies, which are inflammable,
kindled in the earth, without so much as seeing how that may be done.
This agent heat, then, is a new principle to be employed in forming a
theory of the earth; a principle that must have been in the constitution
of this globe, when contrived to subsist as a world, and to maintain
a system of living bodies perpetuating their species. It is therefore
necessary to connect this great mineral principle, subterraneous fire
or heat, with the other operations of the world, in forming a general
theory. For, whether we are to consider those great and constant
explosions of mineral fire as a principal agent in the design, or only
as a casual event depending upon circumstances which give occasion to an
operation of such magnitude, here is an object that must surely have its
place in every general theory of the earth.
In examining things which actually exist, and which have proceeded in a
certain order, it is natural to look for that which had been first; man
desires to know what had been the beginning of those things which now
appear. But when, in forming a theory of the earth, a geologist shall
indulge his fancy in framing, without evidence, that which had preceded
the present order of things, he then either misleads himself, or writes
a fable for the amusement of his reader. A theory of the earth, which
has for object truth, can have no retrospect to that which had preceded
the present order of this world; for, this order alone is what we have
to reason upon; and to reason without data is nothing but delusion. A
theory, therefore, which is limited to the actual constitution of this
earth, cannot be allowed to proceed one step beyond the present order of
things.
But, having surveyed the order of this living world, and having
investigated the progress of this active scene of life, death and
circulation, we find ample data on which to found a train of the most
conclusive reasoning with regard to a general design. It is thus that
there is to be perceived another system of active things for the
contemplation of our mind;--things which, though not immediately within
our view, are not the less certain in being out of our sight; and things
which must necessarily be comprehended in the theory of the earth, if we
are to give stability to it as a world sustaining plants and animals.
This is a mineral system, by which the decayed constitution of an earth,
or fruitful surface of habitable land, may be continually renewed in
proportion as it is wasted in the operations of this world.
It is in this mineral system that I have occasion to compare the
explanations, which I give of certain natural appearances, with the
theories or explanations which have been given by others, and which are
generally received as the proper theory of those mineral operations. I
am, therefore, to examine those different opinions, respecting the
means employed by nature for producing particular appearances in the
construction of our land, appearances which must be explained in some
consistent mineral theory.
These appearances may all be comprehended under two heads, which are now
to be mentioned, in order to see the importance of their explanation, or
purpose which such an explanation is to serve in a theory of the earth.
The first kind of these appearances is that of known bodies which we
find composing part of the masses of our land, bodies whose natural
history we know, as having existed in another state previous to the
composition of this earth where they now are found; these are the
relicts or parts of animal and vegetable bodies, and various stony
substances broken and worn by attrition, all which had belonged to a
former earth. By means of these known objects, we are to learn a great
deal of the natural history of this earth; and, it is in tracing that
history, from where we first perceive it, to the present state of
things, that forms the subject of a geological and mineralogical theory
of this earth. But, we are more especially enabled to trace those
operations of the earth, by means of the second kind of appearances,
which are now to be mentioned.
These again are the evident changes which those known bodies have
undergone, and which have been induced upon such collected masses of
which those bodies constitute a part. These changes are of three sorts;
_first_, the solid state, and various degrees of it, in which we now
find those masses which had been originally formed by the collection of
loose and incoherent materials; _secondly_, the subsequent changes which
have evidently happened to those consolidated masses which have been
broken and displaced, and which have had other mineral substances
introduced into those broken and disordered parts; and, _lastly_, that
great change of situation which has happened to this compound mass
formed originally at the bottom of the sea, a mass which, after being
consolidated in the mineral region, is now situated in the atmosphere
above the surface of the sea.
In this manner we are led to the system of the world, or theory of the
earth in general; for, that great change of situation, which our land
has undergone, cannot be considered as the work of accident, or any
other than an essential part in the system of this world. It is
therefore a proper view of the necessary connection and mutual
dependence of all those different systems of changing things that forms
the theory of this earth as a world, or as that active part of nature
which the philosophy of this earth has to explore. The animal system is
the first or last of these; next comes the vegetable system, on which
the life of animals depends; then comes the system of this earth,
composed of atmosphere, sea, and land, and comprehending the various
chemical, mechanical, and meteorologically operations which take place
upon that surface where vegetation must proceed; and, lastly, we have
the mineral system to contemplate, a system in which the wasting surface
of the earth is employed in laying the foundation of future land within
the sea, and a system in which the mineral operations are employed in
concocting that future land.
Now, such must surely be the theory of this earth, if the land is
continually wasting in the operations of this world; for, to acknowledge
the perfection of those systems of plants and animals perpetuating their
species, and to suppose the system of this earth on which they must
depend, to be imperfect, and in time to perish, would be to reason
inconsistently or absurdly. This is the view of nature that I would wish
philosophers to take; but, there are certain prejudices of education or
prepossession of opinion among them to be overcome, before they can be
brought to see those fundamental propositions,--the wasting of the land,
and the necessity of its renovation by the co-operation of the mineral
system. Let us then consider how men of science, in examining the
mineral state of things, and reasoning from those appearances by which
we are to learn the physiology of this earth, have misled themselves
with regard to physical causes, and formed certain mineralogical and
geological theories, by which their judgment is so perverted, in
examining nature, as to exclude them from the proper means of correcting
their first erroneous notions, or render them blind to the clearest
evidence of any other theory that is proposed.
When men of science reason upon subjects where the ideas are distinct
and definite, with terms appropriated to the ideas, they come to
conclusions in which there is no difference of opinion. It is otherwise
in physical subjects, where things are to be assimilated, in being
properly compared; there, things are not always compared in similar and
equal circumstances or conditions; and there, philosophers often draw
conclusions beyond the analogy of the things compared, and thus judge
without data. When, for example, they would form the physical induction,
with regard to the effect of fire or water upon certain substances in
the mineral regions, from the analogy of such events as may be observed
upon the surface of the earth, they are apt to judge of things acting
under different circumstances or conditions, consequently not producing
similar effects; in which case, they are judging without reason, that
is, instead of inductive reasoning from actual data or physical truth,
they are forming data to themselves purely by supposition, consequently,
so far as these, imagined data may be wrong, the physical conclusion, of
these philosophers may be erroneous.
It is thus that philosophers have judged, with regard to the effects of
fire and water upon mineral substances below the bottom of the sea,
from what their chemistry had taught them to believe concerning bodies
exposed to those agents in the atmosphere or on the surface of the
earth. If in those two cases the circumstances were the same, or
similar, consequently the conditions of the action not changed, then,
the inductive reasoning, which they employ in that comparison, would be
just; but, so far as it is evidently otherwise, to have employed that
inductive conclusion for the explanation of mineral appearances, without
having reason to believe that those changed circumstances of the case
should not make any difference in the action or effect, is plainly to
have transgressed the rules of scientific reasoning; consequently,
instead of being a proper physical conclusion, it is only that imperfect
reasoning of the vulgar which, by comparing things not properly analysed
or distinguished, is so subject to be erroneous. This vague reasoning,
therefore, cannot be admitted as a part of any geological or mineral
theory. Now I here maintain, that philosophers have judged in no other
manner than by this false analogy, when they conclude that water is the
agent by which mineral concretions have been formed. But it will be
proper to state more particularly the case of that misunderstanding
among mineral philosophers.
In forming a geological theory, the general construction of this earth,
and the materials of which it is composed, are such visible objects, and
so evident to those who will take the pains to examine nature, that
here is a subject in which there cannot be any doubt or difference of
opinion. Neither can there be any dispute concerning the place and
situation of mass when it was first formed or composed; for, this is
clearly proved, from every concomitant circumstance, to have been at the
bottom of the sea. The only question in this case, that can be made, is,
How that mass comes now to be a solid body, and above the surface of the
sea in which it had been formed?
With regard to the last, the opinions of philosophers have been so
dissonant, so vague, and so unreasonable, as to draw to no conclusion.
Some suppose the land to be discovered by the gradual retreat of the
ocean, without proposing to explain to us from whence had come the known
materials of a former earth, which compose the highest summits of the
mountains in the highest continents of the earth. Others suppose the
whole of a former earth to have subsided below the bottom even of the
present sea, and together with it all the water of the former sea, from
above the summits of the present mountains, which had then been at the
bottom of the former sea. The placing of the bottom of the sea, or any
part of it, in the atmosphere so as to be dry land, is no doubt a great
operation to be performed, and a difficult task to be explained; but
this is only an argument the more for philosophers to agree in adopting
the most reasonable means.
But though philosophers differ so widely in that point, this is not the
case with regard to the concretion of mineral bodies; here mineralists
seem to be almost all of one mind, at the same time without any reason,
at least, without any other reason than that false analogy which they
have inconsiderately formed from the operations of the surface of this
earth. This great misunderstanding of mineralists has such an extensive
and baneful effect in the judging of geological theories, that it
will be proper here to explain how that has happened, and to shew the
necessity of correcting that erroneous principle before any just opinion
can be formed upon the subject.
Fire and water are two great agents in the system of this earth; it is
therefore most natural to look for the operation of those agents in the
changes which are made on bodies in the mineral regions; and as the
consolidated state of those bodies, which had been collected at the
bottom of the sea, may have been supposed to be induced either by
fusion, or by the concretion from a solution, we are to consider how far
natural appearance lead to the conclusion of the one or other of those
two different operations. Here, no doubt, we are to reason analogically
from the known power and effects of those great agents; but, we must
take care not to reason from a false analogy, by misunderstanding the
circumstances of the case, or not attending to the necessary conditions
in which those agents act.--We must not conclude that fire cannot burn
in the mineral regions because our fires require the ventilation of the
atmosphere; for, besides the actual exigence of mineral fire being a
notorious matter of fact, we know that much more powerful means _may_
be employed by nature, for that mineral purpose of exciting heat, than
those which we practise.--We must not conclude that mineral marble is
formed in the same manner as we see a similar stony substance produced
upon the surface of the earth, unless we should have reason to suppose
the analogy to be complete. But, this is the very error into which
mineral philosophers have fallen; and this is the subject which I am now
to endeavour to illustrate.
The manner in which those philosophers have deceived themselves when
reasoning upon the subject of mineral concretion, is this: They see,
that by means of water a stony substance is produced; and, this stony
body so much resembles mineral marble as to be hardly distinguishable in
certain cases. These mineral philosophers then, reasoning in the manner
of the vulgar, or without analysing the subject to its principle,
naturally attribute the formation of the mineral marble to a cause
of the same sort; and, the mineral marble being found so intimately
connected with all other mineral bodies, we must necessarily conclude,
in reasoning according to the soundest principles, that all those
different substances had been concreted in the same manner. Thus, having
once departed one step from the path of just investigation, our physical
science is necessarily bewildered in the labyrinth of error. Let us
then, in re-examining our data, point out where lies that first devious
step which had been impregnated with fixed air, or carbonic acid gas,
(as it is called), dissolves a certain portion of mild calcareous
earth or marble; consequently such acidulated water, that is, water
impregnated with this gas, will, by filtrating through calcareous
substances, become saturated with that solution of marble; and, this
solution is what is called a _petrifying water_. When this solution is
exposed to the action of the atmosphere, the acid gas, by means of which
the stony substance is dissolved, evaporates from the solution, in
having a stronger attraction for the atmospheric air; it is then that
the marble, or calcareous substance, concretes and crystallises,
separating from the water in a sparry state, and forming a very solid
stone by the successive accretion from the solution, as it comes to
be exposed to the influence of the atmosphere in flowing over the
accumulating body. Here is the source of their delusion; for, they do
not distinguish properly the case of this solution of a stony substance
concreting by means of the separation of its solvent, and the case of
such a solution being in a place where that necessary condition cannot
be supposed to exist; such as, e.g., the interstices among the particles
of sand, clay, etc. deposited at the bottom of the sea, and accumulated
in immense stratified masses.
No example can better illustrate how pernicious it is to science to have
admitted a false principle, on which a chain of reasoning is to proceed
in forming a theory. Mineral philosophers have founded their theory upon
that deceitful analogy, which they had concluded between the stalactical
concretions of petrifying waters and the marble formed in the mineral
regions; thus, blinded by prejudice, they shut the door against the
clearest evidence; and it is most difficult to make them see the error
of their principle. But this is not to be wondered at, when we consider
how few among philosophising men remount to the first principles of
their theory; and, unless they shall thus remount to that first step,
in which the concreting operation of a dissolved stony substance
is supposed to take place without the necessary conditions for the
petrifying operation, it is impossible to be convinced that their
theory, thus formed with regard to mineral concretion, is merely
supposition, and has no foundation in matter of fact from whence it
should proceed.
But this is not all; for, even supposing their theory to be well founded
and just, it is plainly contradicted by natural appearances. According
to that theory of aqueous consolidation, all the stratified bodies, of
which this earth in general consists, should be found in the natural
order of their regular formation; but, instead of this, they are found
every where disturbed in that order more or less; in many places this
order and regularity is so disturbed as hardly to be acknowledged; in
most places we find those stratified bodies broken, dislocated, and
contorted, and this aqueous theory of mineralists has neither the means
for attaining that end, were it required in their theory, nor have they
any such purpose in their theory, were that end attainable by the means
which they employ. Thus blinded by the prejudice of a false analogy,
they do not even endeavour to gratify the human understanding (which
naturally goes in quest of wisdom and design) by forming a hypothetical
or specious theory of the mineral system; and they only amuse themselves
with the supposition of an unknown operation of water for the
explanation of their cabinet specimens, a supposition altogether
ineffectual for the purpose of forming a habitable earth, and a
supposition which is certainly contradicted by every natural appearance.
Thus, in examining geological and mineralogical theories, I am laid
under the disagreeable necessity of pointing out the errors of physical
principles which are assumed, the prejudices of theoretical opinions
which have been received, and the misconceived notions which
philosophers entertain with regard to the system of nature, in which may
be perceived no ineffectual operation, nor any destructive intention,
but the wise and benevolent purpose of preserving the present order of
this world. But, though thus misled with regard to the cause of things,
naturalists are every where making interesting observations in the
mineral kingdom, I shall therefore avail myself of that instructive
information, for the confirmation of my theory.
It may now be proper to consider what must be required, in order to have
a geological and mineral theory established upon scientific principles,
or on such grounds as must give conviction to those who will examine
the subject; for, unless we may clearly see that there are means for
attaining that desirable end, few philosophers will be persuaded to
pursue this branch of knowledge.
A theory is nothing but the generalization of particular facts; and, in
a theory of the earth, those facts must be taken from the observations
of natural history. Nature is considered as absolutely true; no error or
contradiction can be found in nature. For, if such contradiction were
truly found, if the stone, for example, which fell to day were to rise
again to-morrow, there would be an end of natural philosophy, our
principles would fail, and we would no longer investigate the rules of
nature from our observations.
Every natural appearance, therefore, which is explained, _i.e._ which is
made to come into the order of things that happen, must so far confirm
the theory to which it then belongs. But is it necessary, that every
particular appearance, among minerals, should be thus explained in
a general theory of the earth? And, is any appearance, which is not
explained by it, to be considered as sufficient to discredit or confute
a theory which corresponded with every other appearance? Here is a
question which it would require some accuracy to resolve.
If we knew all the powers of nature, and all the different conditions in
which those powers may have their action varied, that is to say, if we
were acquainted with every physical cause, then every natural effect, or
all appearances upon the surface of this earth, might be explained in a
theory that were just. But, seeing that this is far from being the case,
and that there may be many causes of which we are as yet ignorant, as
well as certain conditions in which the known action of powers may be
varied, it must be evident, that a theory of the earth is not to be
confuted by this argument alone, That there are, among natural bodies,
certain appearances which are not explained by the theory. We must
admit, that, not having all the data which natural philosophy requires,
we cannot pretend to explain every thing which appears; and that our
theories, which necessarily are imperfect, are not to be considered as
erroneous when not explaining every thing which is in nature, but only
when they are found contrary to or inconsistent with the laws of nature,
which are known, and with which the case in question may be properly
compared.
But we may have different theories to compare with nature; and, in that
case, the question is not, How far any of those theories should explain
all natural appearances? but, How far any one particular theory might
explain a phenomenon better than another? In this case of comparison, it
will be evident, that if one theory explains natural appearances, then
the opposite to that theory cannot be supposed to explain the same
appearances. If for example, granite, porphyry, or basaltes, should be
found naturally formed by fusion, the formation of those stones could
not be supposed in any case as formed by water, although it could not
be demonstrated that water is incapable of forming those mineral
productions.
In like manner, if those three bodies were proved to have been actually
formed by water alone, then, in other cases where we should have no
proof, they could not be supposed as having been formed by fire or
fusion. It must be evident, that an equal degree of proof of those two
different propositions would leave our judgment in suspence, unless that
proof were perfect, in which case, we would have two different causes
producing similar effects. But, if we shall have a sufficient proof
upon the one side, and only a presumptive proof or probability upon the
other, we must reject that probability or presumption, when opposed by
a proof, although that proof were only an induction by reasoning from
similar effects as following similar causes. _A fortiori_, if there be
on one side a fair induction, without the least suspicion of error,
and on the other nothing but a mere presumption founded upon a distant
analogy, which could not even properly apply, then, the inductive proof
would be as satisfactory as if there had not been any supposition on the
opposite side.
So far as a theory is formed in the generalization of natural
appearances, that theory must be just, although it may not be perfect,
as having comprehended every appearance; that is to say, a theory is
not perfect until it be founded upon every natural appearance; in which
case, those appearances will be explained by the theory. The theory of
gravitation, though no ways doubtful, was not so perfect before the
shape of this globe had been determined by actual measurement, and
before the direction of the plummet had been tried upon Shihallion, as
after those observations had been made. But a theory which should be
merely hypothetical, or founded upon a few appearances, can only be
received as a theory, after it has been found to correspond properly
with nature; it would then be held a proper explanation of those natural
appearances with which it corresponded; and, the more of those phenomena
that were thus explained by the theory, the more would that, which had
been first conjectural, be converted into a theory legitimately founded
upon natural appearances.
Matter of fact is that upon which science proceeds, by generalization,
to form theory, for the purpose of philosophy, or the knowledge of all
natural causes; and it is by the companion of these matters of fact with
any theory, that such a theory will be tried. But, in judging of matter
of fact, let us be cautious of deceiving ourselves, by substituting
speculative reasoning in place of actual events.
Nature, as the subject of our observation, consists of two sorts of
objects; for, things are either active, when we perceive change to take
place in consequence of such action, or they are quiescent, when we
perceive no change to take place. Now, it is evident, that in judging
of the active powers of nature from the quiescent objects of our
information, we are liable to error, in misinterpreting the objects
which we see; we thus form to ourselves false or erroneous opinion
concerning the general laws of action, and the powers of nature. In
comparing, therefore, generalised facts, or theory, with particular
observations, there is required the greatest care, neither, on the one
hand, to strain the appearances, so as to bring in to the theory a fact
belonging to another class of things; nor, on the other, to condemn a
proper theory, merely because that theory has not been extended to the
explanation of every natural appearance.
But, besides the misinterpretation of matters of fact, we are also to
guard against the misrepresentation of natural appearances. Whether
warped by the prejudice of partial and erroneous theory, or deceived by
the inaccuracy of superficial observation, naturalists are apt to see
things in an improper light, and thus to reason from principles which
cannot be admitted, and, which often lead to false conclusions. A
naturalist, for example, comes to examine a cavity in the mines, he
there finds water dropping down all around him, and he sees the cavity
all hung with siliceous crystals; he then concludes, without hesitation,
that here is to be perceived cause and effect, or that he actually sees
the formation of those crystallizations from the operation of water. It
is thus that I have been told by men of great mineral knowledge, men who
must have had the best education upon that subject of mineralogy, and
who have the superintendance of great mineral concerns in Germany, that
they had actually seen nature at work in that operation of forming
rock-crystal;--they saw what I have now described; they could see no
more; but, they saw what had convinced them of that which, there is
every reason to believe, never happened. With regard to my theory,
I wish for the most rigorous examination; and do not ask for any
indulgence whatever, whether with regard to the principles on which the
theory is built, or for the application of the theory to the explanation
of natural appearances. But, let not geologists judge my theory by their
imperfect notions of nature, or by those narrow views which they take of
the present state of things;--let not mineralogists condemn my theory,
for no other reason but because it does not correspond with their false
principles, and those gratuitous suppositions by which they had been
pleased to explain to themselves every thing before. First let them look
into their own theory, and correct that erroneous principle, with regard
to the action of water, or the assumption of unknown causes, upon which
they have reasoned in forming their vague notions of the mineral region,
before they can be properly qualified to examine, impartially, a theory
which employs another principle. Every thing which has come under my
observation shall be, as far as I can, faithfully related; nor shall I
withhold those which neither the present theory, nor any other that I am
acquainted with, can, I think, explain.
Appearances cannot well be described except in relation to some theory
or general arrangement of the subject; because the particular detail,
of every part in a complicated appearance, would be endless and
insignificant. When, however, any question in a theory depends upon the
nature of an appearance, we cannot be too particular in describing that
by which the question is to be decided. But though it be sometimes
proper to be minute in a particular, it is always, and above all things,
necessary to be distinct; and not to confound together things which are
of different natures. For, though it be by finding similarity, in things
which at first sight may seem different, that science is promoted and
philosophy attained, yet, we must have a distinct view of those things
which are to be assimilated; and surely the lowest state of knowledge
in any subject, is the not distinguishing things which, though not to
common observation different, are not truly the same.
To confound, for example one stone with another, because they were both
hard, friable, and heavy, would be to describe, with the superficial
views of vulgar observation; whereas science specifies the weight and
hardness, and thus accurately distinguishes the stone.
Before naturalists had learned to distinguish what they saw, and to
describe, in known terms, those natural appearances, a theorist must
have generalised only from his proper observation. This has been my
case. When I first conceived my theory, few naturalists could write
intelligibly upon the subject; but that is long ago, and things are much
altered since; now there are most enlightened men making observations,
and communicating natural knowledge. I have the satisfaction, almost
every day, to compare the theory, which I had formed from my proper
observations, with the actual state of things in almost every quarter of
the globe.
Whether, therefore, we mean to try a theory by its application to
such phenomena as are well understood, or to learn something from the
application of particular phenomena to a well established theory,
we shall always find it interesting to have appearances described;
particularly such as may be referred to some general rule, as
circumscribing it to certain conditions, or as finding rule in rule,
that is to say, discovering those particular conditions in which the
general laws of action may be affected.
Instead, for example, of the rule which we find in the application of
heat for the fusion and evaporation of mineral substances upon the
surface of this earth, we may find it necessary to consider the effect
which changed circumstances produce in the mineral regions, and occasion
a change of that rule of action which we have learned from experience,
when melting and evaporating those substances in the atmosphere or on
the surface of the earth.
It is in this manner that a theory, which was formed by the
generalization of particular facts, comes to be a source of information,
by explaining to us certain appearances which otherwise we could not
understand. Thus, it was not the appearance of the tides that taught the
theory of gravitation; it was the theory of gravitation that made us
understand the appearance of the tides. In like manner, the law of
gravitation, which was demonstrated from the motion of the moon in her
orbit round this earth, when applied to the paths of comets, explained
that appearance. Our theory, of a central fire, has been formed upon
the consolidation of the strata of this earth; but this theory is to be
applied for the explanation of various different appearances. In this
manner, two different purposes will be served; the trying of the theory
by its application to phenomena; and the explanation of phenomena by the
principles laid open in the theory.
I may repeat it; a theory of the earth must ultimately depend upon
matter of fact or particular observation; but those observations must be
distinct, and those distinguished things must be generalised. We have
just now given for an example, a distinction among stones, in knowing
them by their sensible qualities. But, besides distinguishing those
objects, we are also to inquire into the origin and cause of those
things which are distinguished. Here, again, we take into our aid the
chemical as well as the mechanical properties of these several things;
and hence learn to know on what their natural form and constitution may
depend. Having thus attained the natural philosophy of stones, we next
inquire into the place and application of those things in nature; and
in this manner we acquire some knowledge with regard to the natural
constitution of this earth. We find this earth composed of known things;
it is therefore the operations, required in these compositions, which
form the natural philosophy of this earth, considered as a body of solid
land. But, the solid land is only one part of the globe; therefore,
the philosophy of the globe proceeds still farther by knowing the
constitution of this planetary body, as consisting of different parts
united for a purpose, which is that of a world.
The general theory of this earth as a world, will thus appear to be a
complex thing, which however founded upon simple principles, contains
many subjects of discussion, and requires attention to a variety of
particulars. For, not only the great features of this earth are to be
explained by the theory, but also the most minute appearance, such as
are to be found, even with microscopic observation, in every particular
part.
Thus the nature, constitution, and cause of every particular appearance
in the construction of this earth, are to be investigated in a
geological theory, as well as that general constitution of the world in
which all the particular parts are to be employed for a purpose.
If the subject here examined shall be found properly explained, there
will remain little doubt with regard to the justness of the theory,
which will then be applicable to other appearances that may occur;
although every appearance is not to be explained, in a manner equally
satisfactory, by any theory which is not perfect.
The first subject to be examined is the modern theory of primitive
mountains. I have written several chapters upon that subject, having
successively acquired more light in this interesting part of the theory,
by observations of my own in several places of this country, as well as
from the natural history of other countries. I shall give these nearly
in the order in which they occurred, or had been written.
CHAP. IV.
The Supposition of Primitive Mountains refuted.
In the theory now given, the earth has been represented as a composition
of different materials, which had existed in another form, and as the
effect of natural operations; therefore, however various may be found
the structure of our earth, and however dissimilar some parts of
its composition may be in comparison with others, no part should be
considered as original, in relation to the globe, or as primitive, in
relation to second causes, _i.e._ physical operations by which those
parts should have been formed. But it is pretended by naturalists, that
there are certain primitive mountains in the earth, bodies which have
had another origin than that of the general strata of the globe and
subsequent masses; an origin, therefore, which cannot be considered as
having been produced from natural operations, or as effected in the
course of known causes. Now, if it can be made to appear, that there is
no solid ground for this distinction; and if it can be shown, that there
is truly no mineral body in this earth which may not have been produced
by operations natural to the globe, we should thus procure a certain
confirmation of the doctrine. This also will be the more interesting,
in being deduced from a part of natural appearances, which seemed to be
inconsistent with the theory.
Certain masses or mountains of granite, are the only bodies of this
earth which have apparently a certain pretension to this species
of originality. These, therefore, must be now the subject of our
examination.
Granite, considered by itself, does not appear to have any claim to
originality in its nature. It is composed of bodies which are capable of
being analyzed; and these are then found to be compositions of different
substances, which are also sometimes variously proportioned. The
feldspar and the mica, for example, as well as the schorl, are found
variously coloured in different granites, and coloured in various
proportions. Besides the variety in the composition, or chemical mixture
of the different bodies which compose granite, this rock admits of a
great diversity, from the variety of its mechanical mixture, or from
the different species of bodies which are its constituent parts. M. de
Saussure, who has examined this subject perhaps more than any other
person, and who has had the very best opportunities for this purpose,
says, that this composition may be found in all the different
combinations which may be produced by every possible composition of 7
or 8 different kinds of stone, (page 108, Voyage dans les Alpes, etc.).
Neither does this fill up the measure of its variety; for, another
source of change is found in the grain of this rock stone; I have a
specimen of this variety from the size almost of sand to that of some
inches.
Were granite, therefore, to be supposed as in the original state of its
creation, nature would be considered as having operated in an indefinite
diversity of ways, without that order and wisdom which we find in all
her works; for here would be change without a principle, and variety
without a purpose. There is no reason, however, to suppose granite
original, more than any other composite rock, although we may be
ignorant of the particular process in which it is formed, and although,
comparatively in relation to certain other rocks, granite, or certain
masses of this composition, may be found of a more ancient date.
If granite be truly stratified, and those strata connected with the
other strata of the earth, it can have no claim to originality; and
the idea of primitive mountains, of late so much employed by natural
philosophers, must vanish, in a more extensive view of the operations of
the globe; but it is certain that granite, or a species of the same kind
of stone, is thus found stratified. It is the _granit feuilletée_ of
M. de Saussure, and, if I mistake not, what is called _gneis_ by the
Germans. We have it also in our north alpine country of Scotland; of
this I have specimens, but have not seen it in its place.
Granite being thus found stratified, the masses of this stone cannot be
allowed to have any right of priority over the schistus, its companion
in the alpine countries, although M. de Saussure, whose authority I
would revere, has given it for the following reason; that it is found
the most centrical in the chains of high mountains, or in alpine
countries. Now, supposing this fact to be general, as he has found it in
the Alps, no argument for the priority of those masses can be founded
either upon the height or the situation of those granite mountains; for
the height of the mountain depends upon the solidity and strength of the
stone. Now though it is not to be here maintained that granite is the
most durable of those alpine rocks, yet as a mountain, either granite in
general, or in particular, certain species of it, may be esteemed such,
consequently, this massy stone, remaining highest in the mountainous
region, will naturally be considered as the centre, and according to
this rule, as having the pre-eminence in point of seniority.
The rock which stands in competition with granite for the title of
primitive in the order of mountains, is that micaceous stratified stone
which is formed chiefly of quartz, but which admits of great variety
like the granite. The difference between those two bodies does not
consist in the materials of which they are composed, for, in their
varieties, they may be in this respect the same, but in a certain
regularity of composition, in this alpine stone, which evidently arises
from stratification or subsidence in water.
If we shall thus consider all the varieties of this alpine stone as
being of one kind, and call it granite, then we shall distinguish in
this body two different species, from whence perhaps some interesting
conclusion may be formed with regard to the operations of the globe.
These two species are, _first_, granite regular in its composition, or
stratified in its construction; and, _secondly_, granite in mass, or
irregular in its construction. Let us now endeavour to make use of these
generalizations and distinctions.
In examining the great diversity of our whinstone, trap, or basaltes, it
is found at last to granulate into granite; at the same time those two
different species of rock-stone may be distinguished. A perfect granite
has not in its composition necessarily any argillaceous earth, farther
than may be in the natural constitution of its distinct parts; whereas,
a perfect basalt may have abundance of this substance, without any
quartz or any siliceous body. A perfect granite, is, therefore, an
extremely hard stone, having quartz and feldspar for its basis; but a
perfect whin or basaltes may be extremely soft, so as to cut easily with
a knife. In like manner granite is a composition which graduates into
porphyry; but porphyry is only whinstone of a harder species. Therefore,
though perfectly distinct, those three things graduate into each other,
and may be considered as the same.
Granite and whinstone, or basaltes, though distinct compositions, thus
graduating into each other; and whinstone, as well as porphyry, being
without doubt a species of lava, we may consider the granite which is
found in mass without stratification, in like manner as we do the masses
of whinstone, basaltes, or Swedish trap, as having flowed in the bowels
of the earth, and thus been produced by the chance of place, without any
proper form of its own, or in an irregular shape and construction. In
this manner would be explained the irregular shape or structure of those
granite masses; and thus great light would be thrown upon the waved
structure of the stratified alpine stone, which, though it has not been
made to flow, has been brought to a great degree of softness, so as to
have the original straight lines of its stratification changed to
those undulated or waving lines which are in some cases extremely much
incurvated.
It remains only to confirm this reasoning, upon our principles, by
bringing actual observation to its support; and this we shall do from
two of the best authorities. The Chevalier de Dolomieu, in describing
the volcanic productions of Etna, mentions a lava which had flowed from
that mountain, and which may be considered as a granite. But M. de
Saussure has put this matter out of doubt by describing most accurately
what he had seen both in the Alps and at the city of Lyons. These are
veins of granite which have flowed from the contiguous mass into the
stratified stone, and leave no doubt with regard to this proposition,
that the granite had flowed in form of subterranean lava, although M. de
Saussure has drawn a very different conclusion from this appearance. I
have also a specimen from this country of a vein of granite in a granite
stone, the vein being of a smaller grain than that of the rock which it
traverses.[20]
[Note 20: This is what I had wrote upon, the subject of granite, before
I had acquired such ample testimony from my own observations upon
that species of rock. I have given some notice, in the 3d vol. of the
Transactions of the Edinburgh R.S. concerning the general result of
those observations, which will be given particularly in the course of
this work.]
It will thus appear, that the doctrine which of late has prevailed, of
primitive mountains, or something which should be considered as original
in the construction of this earth, must be given up as a false view of
nature, which has formed the granite upon the same principle with that
of any other consolidated stratum; so far as the collection of different
materials, and the subsequent fusion of the compound mass, are necessary
operations in the preparation of all the solid masses of the earth.
Whatever operations of the globe, therefore, may be concluded from the
composition of granite masses, as well as of the alpine strata, these
must be considered as giving us information with regard to the natural
history of this earth; and they will be considered as important, in
proportion as they disclose to us truths, which from other strata might
not be so evident, or at all made known.
Let us now examine the arguments, which, may be employed in favour of
that supposition of primitive mountains.
The observations, on which naturalists have founded that opinion of
originality in some of the component parts of our earth, are these;
_first_, They observe certain great masses of granite in which
stratification is not to be perceived; this then they say is an original
mass, and it is not to be derived from any natural operation of the
globe; _secondly_, They observe considerable tracts of the earth
composed of matter in the order of stratification as to its general
composition, but not as to its particular position, the vertical
position here prevailing, instead of the horizontal which is proper to
strata formed in water; this, therefore, they also term primitive, and
suppose it to be from another origin than that of the subsidence of
materials moved in the waters of the globe; _lastly_, They observe both
strata and masses of calcareous matter in which they cannot distinguish
any marine body as is usual in other strata of the same substance; and
these calcareous masses being generally connected with their primitive
mountains, they have also included these collections of calcareous
matter, in which marine bodies are not observed, among the primitive
parts which they suppose to be the original construction of this globe.
It may be proper to see the description of a calcareous alpine mountain.
M. de Saussure gives us the following observations concerning a mountain
of this kind in the middle of the Alps, where the water divides in
running different ways towards the sea. It is in describing the passage
of the Bon-Homme, (Tom. 2. V. dans les Alpes).
"§ 759. Sur la droite ou au couchant de ces rochers, on voit une
montagne calcaire étonnante dans ce genre par la hardiesse avec laquelle
elle élève contre le ciel ses cimes aigues et tranchantes, taillées
à angles vifs dans le costume des hautes cimes de granit. Elle est
pourtant bien sûrement calcaire, je l'ai observée de près, et on
rencontre sur cette route les blocs qui s'en détachent.
"Cette pierre porte les caractères des calcaires les plus anciennes; sa
couleur est grise, son grain assez fin, on n'y apperçoit aucun vestige
de corps organisés; ses couches sont peu épaisses, ondées et coupées
fréquemment par des fentes parallèles entr'elles et perpendiculaires à
leurs plans. On trouve aussi parmi ces fragmens des brèches calcaires
grises."
Here is a mountain which will rank with the most primitive of the earth;
But why? only because it is extremely consolidated without any mark of
organised body. Had there been in this mountain but one single shell, we
should not then have scrupled to conclude that the origin of this lofty
mountain had been the same with every marble or limestone in the earth.
But though, from the structure of this stone, there is no mark of its
having been formed immediately of the calcareous parts of animals, there
is every mark of those calcareous strata having been formed like other
marbles by deposit in the waters of the globe.
These two things are also homologated by the equal or perfect
consolidation of their substance; for, as it is to be proved that
all stratified marbles have been consolidated by the fusion of their
substance, we must attribute the same consolidating cause to those
alpine masses; the frequent veins that divide those calcareous strata
which M. de Saussure has here described, also prove the nature of the
consolidating cause, (see Chap. 1. page 111.).
This mountain, considered by itself, may perhaps afford no data by which
a naturalist might read the circumstances of its origin. But, Is a
theory of the earth to be formed upon such a negative observation? and,
Is there any particular in this mountain, that may not be shown in
others of which the origin is not in any degree doubtful?
It is not to be disputed, that there are parts of the solid body of our
earth which may be considered as primary or prior, compared with others
that are posterior, in relation to the time of their formation, and much
less changed with regard to the state in which they had been originally
formed:--But it is here denied, that there are any parts of the earth
which do not appear to have had the same origin with all the rest, so
far as this consists in the collection of materials deposited at the
bottom of the waters[21]; for there is no solid mass of land that may
not be traced to this origin, either from its composition, or from its
local connection with other masses, the nature of which in this respect
are known. We have already given examples of this from sufficient
authority. The evidence, therefore, of those primary masses being
original in relation to the natural operations of the globe, is reduced
to this assertion, that there are no vestiges of organised bodies to be
found in those primary masses. Let us now examine how far this testimony
for the originality of those masses is to be admitted in fact and sound
reasoning.
[Note 21: There are no collection of those alpine masses in which may
not be found in some of them sand, mica, and gravel; but these materials
prove the existence of an earth, on which those fragments of greater
masses had been formed, and more or less worn by attrition.]
The matter in question at present is this, that there are certain tracts
of countries in which no vestige of organised bodies are found; now, let
us suppose the fact to be true or well grounded, Can we conclude
from this that there had been originally no organised bodies in the
composition of those masses?--Such a conclusion could only be formed in
making a supposition, that every organised body deposited in a mass
of matter, whether homogeneous or heterogeneous, should be preserved
without change, while the collected mass, in which it had been
deposited, changes as much as possible by the operation both of fire and
water. But this supposition is erroneous, and cannot be admitted; and
the study of marbles will demonstrate this truth, that the calcareous
relics of organised bodies are changed, in the consolidating operations
of the globe, in every degree, from the smallest alteration to the
greatest, when they become indistinguishable any farther to our sight.
Therefore, from the supposition of no appearance of marine bodies in the
pretended primitive masses, there is no sufficient evidence or reason to
conclude, that those masses have not had a marine origin; because, the
traces of organised bodies may be obliterated by the many subsequent
operations of the mineral region; and which operations, the present
state of those masses certify beyond dispute.
We are now to examine the fact, how far the ground on which that false
reasoning had been founded is strictly true.
In the first place, then, it must be considered, that the alledged fact
is nothing but a negative assertion, importing that no mark of organised
bodies had been observed, in certain stones and strata which some
naturalists have examined with that view. But, though many naturalists
have looked for them without success, it does not follow that such marks
may not be found; it indeed proves that such a task is difficult, and
the success of it, to a particular, most precarious; accident, however,
may bring about what the greatest industry has not been able to attain.
Secondly, there is good reason to believe that this asserted negation
is not absolutely true; for I have in my possession what I consider as
proof of the contrary; I found it in Wales, and I think it is in what
may be considered as primitive mountains;--it is the mark of shells in a
stone of that kind.
Thus, I had formed my opinion with regard to this alleged fact, long
before I had seen any description either of the Alps or Pyrennean
mountains; and now I have no reason to change that opinion. It may
indeed be alleged, that the strata of marble or limestone, containing
marine bodies found in those mountains, are secondary strata, and not
the primitive. To this I can give no reply, as the descriptions given of
those strata do not enable me to decide this point.
At the village of Mat, under the Mont Blatten for example, there is a
quarry of schistus or black slate, in which are often found the print
and the bones of fishes. (Discours sur l'Histoire Naturelle de la
Suisse, page 225.). If this may be considered as an alpine or primitive
schistus, it would be decisive of the question: But it would require to
have it well ascertained that this schistus is truly one of those which
are esteemed primitive, or that it is properly connected with them.
But though I cannot find in those interesting descriptions which we now
have got, any one which is demonstrative of this truth, that calcareous
marine objects are found in the primitive strata, this is not the
case with regard to another object equally important in deciding this
question, Whether the primitive strata are found containing the marks of
organised bodies?
M. de Dellancourt, in his _Observations Minéralogiques_, Journal de
Physique Juillet 1786, in describing the mountains of Dauphiné, gives us
the following fact with regard to those alpine vertical strata.
"La pierre constituante de la montagne d'Oris est en général le _Kneifs_
ou la roche feuilletée mica et quartz à couches plus ou moins ferrées
quelquefois le schorl en roche pénétré de stéatite. Les couches varient
infiniment quant à leur direction et à leur inclinaisons. Cette montagne
est cultivée et riche dans certain cantons, surtout autour du village
d'Oris, mais elle est très-escarpée dans beaucoup d'autres. Entre le
village d'Oris et celui du Tresnay est une espèce de combe assez creuse
formée par la chute des eaux des cimes supérieures des rochers. Cette
combe offre beaucoup de schiste dont les couches font ou très-inclinées
ou perpendiculaires. Entre ces couches il s'en est trouvé de plus noires
que les autres et capable de brûler, mais difficilement. Les habitans
ont extrait beaucoup de cette matière terreuse, et lui ont donné le nom
de charbon de terre. Ils viennent même à bout de la faire brûler, et
de s'en servir l'hiver en la mêlant avec du bois. Ce schiste noir
particulier m'a paru exister principalement dans les endroits ou les
eaux se sont infiltrées entre les couches perpendiculaires, et y ont
entraîné diverse matières, et sur-tout des débris de végétaux que
j'ai encore retrouvés à demi-noirs, pulvérulens et comme dans un état
charbonneux."
This formation of coal, by the infiltration of water and carrying in of
vegetable bodies, certainly cannot be admitted of; consequently, from
this description, there would seem to be strata of coal alternated with
the alpine schisti. But the formation of mineral coal requires vegetable
matter to have been deposited along with those earthy substances, at the
bottom of the sea. The production of vegetable bodies, again, requires
the constitution of sea and land, and the system of a living world,
sustaining plants at least, if not animals.
In this natural history of the alpine schisti, therefore, we have a
most interesting fact, an example which is extremely rare. Seldom are
calcareous organised bodies found among those alpine strata, but still
more rarely, I believe, are the marks of vegetable bodies having
contributed in the formation of those masses. But however rare this
example, it is equally decisive of the question, Whether the alpine
schisti have had a similar origin as the other strata of the globe,
in which are found abundance of animal and vegetable bodies, or their
relics? and we are authorised to say, that since those perfect alpine
strata of Dauphiné have had that origin, all the alpine schisti of the
globe have been originally formed in a similar manner. But to put this
matter out of doubt:
In this summer 1788, coming from the Isle of Man, Mr Clerk and I
traveled through the alpine schistus country of Cumberland and
Westmoreland. We found a limestone quarry upon the banks of Windermere,
near the Low-wood Inn. I examined this limestone closely, but despaired
of finding any vestige of organised body. The strata of limestone
seem to graduate into the slate or schistus strata, between which the
calcareous are placed. Fortunately, however, I at last found a fragment
in which I thought to perceive the works of organised bodies in a
sparry state; I told Mr Clerk so, and our landlord Mr Wright, who had
accompanied us. I have brought home this specimen, which I have now
ground and polished; and now it is most evidently full of fragments of
entrochi. Mr Wright then told me he had seen evident impressions of
marine objects, as I understood from the description, in the slate of
those mountains; and he was to send me specimens so soon as he could
procure them.
Here is one specimen which at once overturns all the speculations formed
upon that negative proposition. The schistus mountains of Cumberland
were, in this respect, as perfect primitive mountains as any upon the
earth, before this observation; now they have no claim upon that score,
no more than any limestone formed of shells.
When I first announced my belief that such objects in natural history
might be found, I little thought to have seen it realised, to such a
degree as has now happened in the little circle of my knowledge. In the
summer 1791,
Professor Playfair was to pass through Cumberland. I begged that he
would inquire of Mr Wright, at the Low-wood Inn, for those objects which
he was to endeavour to procure for me, and to examine the limestone
quarry in which I had found the specimen with entrochi. He went through
another part of those primary mountains, and has found examples of this
kind in the schisti; concerning which he has written me the following
account.
"In a visit which I made to the Lakes of Cumberland in September 1791,
in company with the Hon. Francis Charteris, I met with a limestone
full of marine objects, though from its position it is certainly to be
reckoned among the primary strata. The place where we found this stone
was in the district of Lancashire, that is west of Windermere Lake, on
the road from Ambleside to the north end of Coniston Lake, and not far
from the point when you come in sight of the latter. Just about this
spot we happened to meet with one of those people who serve as guides
to travelers in those parts, and who told us, among other things, that
stones with shells in them were often found not far from where we were
then walking. We immediately began to look about for specimens of that
kind, and soon met with several; the most remarkable of which was in a
rock that rose a little above the surface, about 300 or 400 yards to
the right of the road. It was a part of a limestone stratum, nearly
vertical, and was full of bivalves with the impressions as strong as
in a common secondary limestone. The strata on both sides had the same
inclination, and were decidedly primary, consisting of the ordinary
micaceous schistus. This however I need not remark to you, who know so
well from your own observations that the whole of the country I am now
speaking of has every character of a primary one. I, only mention it,
that it may not be supposed that the rock in question was some fragment
of a secondary stratum that remained, after the rest was washed away,
superincumbent on the primary.
"After I had seen this rock, I recollected that you had told me of
something of the same kind that you saw in a quarry at Low-wood Inn; and
it may be that both belonged to the same stratum or body of strata; for
the direction of the strata, as nearly as I could observe, was from S.W.
to N.E.; and this also is nearly the bearing of Low-wood from the place
where we now were. I send you a specimen, which you can compare with
those you brought from the lime quarry at Low-wood."
I have examined this specimen, and find it to be the common schistus
of that country, only containing many bivalve shells and fragments of
entrochi and madrapore bodies, and mixed with pyrites.
I have already observed that one single example of a shell, or of its
print, in a schistus, or in a stone stratified among those vertical or
erected masses, suffices to prove the origin of those bodies to have
been, what I had maintained them to be, water formed strata erected from
the bottom of the sea, like every other consolidated stratum of the
earth. But now, I think, I may affirm, that there is not, or rarely, any
considerable extent of country of that primary kind, in which some mark
of this origin will not be found, upon careful examination; and now I
will give my reason for this assertion. I have been examining the south
alpine country of Scotland, occasionally, for more than forty years
back, and I never could find any mark of an organised body in the
schistus of those mountains. It is true that I know of only one place
where limestone is found among the strata; this is upon Tweed-side near
the Crook. This quarry I had carefully examined long ago, but could find
no mark of any organised body in it. I suppose they now are working some
other of the vertical strata near those which I had examined; for, in
the summer 1792, I received a letter from Sir James Hall, which I shall
now transcribe. It is dated at Moffat, June 2. 1792.
"As I was riding yesterday between Noble-house and Crook, on the road to
this place, I fell in with a quarry of alpine limestone; it consists of
four or five strata, about three feet thick, one of them single, and the
rest contiguous; they all stand between the strata of slate and schist
that are at the place nearly vertical. In the neighbourhood, a slate
quarry is worked of a pure blue slate; several of the strata of slate
near the limestone are filled with fragments of limestone scattered
about like the fragments of schist in the sandstone in the neighbourhood
of the junction on our coast.[22]
[Note 22: This has a reference to very curious observations which we
made upon the east coast where these mountains terminate, and which I am
to describe in the course of this work.]
"Among the masses of limestone lately broken off for use, and having the
fractures fresh, I found the forms of cockles quite distinct; and in
great abundance.--I send you three pieces of this kind," etc.
It may perhaps be alleged that those mountains of Cumberland and
Tweedale are not the primary mountains, but composed of the secondary
schistus, which is every where known to contain those objects belonging
to a former earth. Naturalists who have not the opportunity of
convincing themselves by their proper examination, must judge with
regard to that geological fact by the description of others. Now it is
most fortunate for natural history, that it has been in this range of
mountains that we have discovered those marks of a marine origin; for,
I shall afterwards have occasion to give the clearest light into this
subject, from observations made in other parts of those same mountains
of schist, by which it will be proved that they are the primary
strata; and thus no manner of doubt will then remain in the minds
of naturalists, who might otherwise suspect that we were deceiving
ourselves, by mistaking the secondary for the primitive schistus.
I have only farther to observe, that those schisti mountains of Wales,
of Cumberland, and of the south alpine part of Scotland, where these
marine objects have been found, consist, of that species of stone which
in some places makes the most admirable slate for covering houses; and,
in other parts, it breaks into blocks that so much resemble wood in
appearance, that, without narrow inspection, it might pass for petrified
wood.
We are therefore to conclude that the marks of organised bodies in those
primary mountains are certainly found; at the same time the general
observation of naturalists has some foundation, so far as the marks of
organised bodies are both rarely to be met with in those masses, and not
easily distinguished as such when they are found.
But this scarcity of marine objects is not confined to those primary
mountains, as they are called; for among the most horizontal strata, or
those of the latest production, there are many in which, it is commonly
thought, no marine calcareous objects are to be found; and this is a
subject that deserves to be more particularly considered, as the theory
may thus receive some illustration.
Sandstone, coal, and their accompanying strata, are thought to be
destitute of calcareous marine productions, although many vestiges of
plants or vegetable productions are there perceived. But this general
opinion is neither accurate nor true; for though it be true that in the
coal and sandstone strata it is most common to find marks of vegetable
production, and rarely those calcareous bodies which are so frequent in
the limestone, yet it is not unusual for coal to be accompanied
with limestone formed of shells and corals, and also with ironstone
containing many of those marine objects as well as wood. Besides,
sandstone frequently contains objects which have been organised bodies,
but which do not belong to the vegetable kingdom, at least to no plant
which grows upon the land, but would seem to have been some species of
zoophite perhaps unknown.
I have also frequently seen the vestige of shells in sandstone, although
in these strata the calcareous bodies are in general not perceived.
The reason of this is evident. When there is a small proportion of the
calcareous matter in the mass of sand which is pervious to steam and to
the percolation of water, the calcareous bodies may be easily dissolved,
and either carried away or dispersed in the mass; or even without being
thus dispersed by means of solution, the calcareous matter may be
absorbed by the siliceous substance of the stratum by means of fusion,
or by heat and cementation. The fact is, that I have seen in sandstone
the empty mould of marine shells with some siliceous crystallization,
so far as I remember, which corresponded perfectly with that idea. The
place I saw this was in a fine white sandstone accompanying the coal,
upon the sea side at Brora in Sutherland.
Mineralogy is much indebted to Mr Pallas for the valuable observations
which he has given of countries so distant from the habitations of
learned men. The physiology of the globe has also been enriched with
some interesting observations from the labours of this learned traveller.
But besides giving us facts, Mr Pallas has also reasoned upon the
subject, and thus entered deep into the science of Cosmogeny; here it
is that I am afraid he has introduced some confusion into the natural
history of the earth, in not properly distinguishing the mineral
operations of the globe, and those again which belong entirely to the
surface of the earth; perhaps also in confounding the natural effects of
water upon the surface of the earth, with those convulsions of the sea
which may be properly considered as the accidental operations of the
globe. This subject being strictly connected with the opinions of that
philosopher with regard to primitive mountains, I am obliged to examine
in this place matters which otherwise might have come more properly to
be considered in another.
M. Pallas in his _Observations sur la formation des montagnes_, (page
48) makes the following observations.
"J'ai déjà dit que _la bande de montagnes primitives schisteuses_
hétérogènes, qui, par toute la terre, accompagne les chaînes
granitiques, et comprend les roches quartzeuses et talceuses mixtes,
trapézoïdes, serpentines, le schiste corne, les roches spathiques et
cornées, les grais purs, le porphyre et le jaspre, tous rocs fêlés
en couches, ou presque perpendiculaires, ou du moins très-rapidement
inclinées, (les plus favorables à la filtration des eaux), semble
aussi-bien que le granit, antérieure à la création organisée. Une raison
très-forte pour appuyer cette supposition, c'est que la plupart de ces
roches, quoique lamelleuse en façon d'ardoise, n'a jamais produit
aux curieux la moindre trace de pétrifactions ou empreintes de corps
organisés. S'il s'en est trouvé, c'est apparemment dans des fentes de
ces roches où ces corps ont été apportés par un deluge, et encastrées
apres dans une matière infiltrée, de même qu'on a trouvé des restes
d'Eléphans dans le filon de la mine d'argent du Schlangenberg.[23] Les
caractères par lesquels plusieurs de ces roches semblent avoir souffert
des effets d'un feu-très-violent, les puissantes veines et amas des
minéraux les plus riches qui se trouvent principalement dans la bande
qui en est composée, leur position immédiate sur le granit, et même le
passage, par lequel on voit souvent en grand, changer le granit en une
des autres espèces; tout cela indique une origine bien plus ancienne,
et des causes bien différentes de celles qui ont produit les montagnes
secondaires."
[Note 23: This is a very natural way of reasoning when a philosopher
finds a fact, related by some naturalists, that does not correspond with
his theory or systematic view of things. Here our author follows the
general opinion in concluding that no organised body should be found in
their primitive strata; when, therefore, such an object is said to have
been observed, it is supposed that there may have been some mistake with
regard to the case, and that all the circumstances may not have been
considered. This caution with regard to the inaccurate representation of
facts, in natural history, is certainly extremely necessary; the relicts
of an elephant found in a mineral vein, is certainly a fact of that
kind, which should not be given as an example in geology without the
most accurate scientifical examination of the subject.]
Here M. Pallas gives his reason for supposing those mountains primitive
or anterior to the operations of this globe as a living world; _first_,
because they have not, in general, marks of animals or plants; and that
it is doubtful if they ever properly contain those marks of organised
bodies; _secondly_, because many of those rocks have the appearance of
having suffered the effects of the most violent fire. Now, What are
those effects? Is it in their having been brought into a fluid state of
fusion. In that case, no doubt, they may have been much changed from the
original state of their formation; but this is a very good reason why,
in this changed state, the marks of organised bodies, which may have
been in their original constitution, should be now effaced.
The _third_ reason for supposing those mountains primitive, is taken
from the metallic veins, which are found so plentifully in these masses.
Now, had these masses been the only bodies in this earth in which those
mineral veins were found, there might be some species of reason for
drawing the conclusion, which is here formed by our philosopher. But
nothing is so common (at least in England) as mineral veins in the
strata of the latest formation, and in those which are principally
formed of marine productions; consequently so far from serving the
purpose for which this argument was employed, the mineral veins in the
primitive mountains tend to destroy their originality, by assimilating
them in some respect with every other mass of strata or mountain upon
the globe.
_Lastly_, M. Pallas here employs an argument taken from an appearance
for which we are particularly indebted to him, and by which the
arguments which have been already employed in denying the originality
of granite is abundantly confirmed. It has been already alleged, that
granite, porphyry, and whinstone, or trap, graduate into each other; but
here M. Pallas informs us that he has found the granite not only changed
into porphyry, but also into the other alpine compositions. How an
argument for the originality of these mountains can be established upon
those facts, I am not a little at a loss to conceive.
The general mineralogical view of the Russian dominions, which we have,
in this treatise, may now be considered with regard to that distinction
made by naturalists, of primitive, secondary, and tertiary mountains, in
order to see how far the observations of this well informed naturalist
shall be found to confirm the theory of the earth which has been already
given, or not.
The Oural mountains form a very long chain, which makes the natural
division betwixt Europe and Asia, to the north of the Caspian. If in
this ridge, as a centre of elevation, and of mineral operations, we
shall find the greatest manifestation of the violent exertion of
subterraneous fire, or of consolidating and elevating operations; and if
we shall perceive a regular appearance of diminution in the violence or
magnitude of those operations, as the places gradually recede from
this centre of active force; we may find some explanation of those
appearances, without having recourse to conjectures which carry no
scientific meaning, and which are more calculated to confound our
acquired knowledge, than to form any valuable distinction of things. Let
us consult M. Pallas how far this is the case, or not.
After having told us that all those various alpine schisti, jaspers,
porphyries, serpentines, etc. in those mountains, are found mutually
convertible with granite, or graduating into each other, our author thus
continues, (p. 50).
"On entrevoit de certaines loix a l'égard de l'arrangement respectif
de cet ordre secondaire d'anciennes roches, par tous les systèmes de
montagnes qui appartiennent à l'Empire Russe. La chaîne Ouralique, par
exemple, a du côté de l'Orient sur tout sa longueur, une très-grande
abondance de schistes cornés, serpentins et talceux, riches en filons
de cuivre, qui forment le principal accompagnement du granite, et en
jaspres de diverses couleurs plus extérieurs et souvent comme entrelacés
avec les premiers, mais formant des suites de montagnes entières, et
occupant de très-grands espaces. De ce même côté, il y paraît beaucoup
de quartz en grandes roches toutes pures, tant dans la principale chaîne
que dans le noyau des montagnes de jaspre, et jusques dans la plaine.
Les marbres spateux et veinés, percent en beaucoup d'endroits. La
plupart de ces espèces ne paraissent point du tout à la lisière
occidentale de la chaîne, qui n'est presque que de roche mélangée de
schistes argileux, alumineux, phlogistique, etc. Les filons des mines
d'or mêlées, les riches mines de cuivre en veines et chambrées, les
mines de fer et d'aimant par amas et montagnes entières, sont l'apanage
de la bande schisteuse orientale; tandis que l'occidentale n'a pour elle
que des mines de fer de dépôts, et se montre généralement très-pauvre en
métaux. Le granit de la chaîne qui borde la Sibérie, est recouvert du
côté que nous connaissons de roches cornées de la nature des pierres à
fusil, quelquefois tendant à la nature d'un grais fin et de schistes
très-métallières de différente composition. Le jaspre n'y est qu'en
filons, ou plans obliques, ce qui est très-rare pour la chaîne
Ouralique, et s'observe dans la plus grande partie de la Sibérie, à
l'exception de cette partie de sa chaîne qui passe près de la mer
d'Okhotsk, ou le jaspre forme derechef des suites de montagnes, ainsi
que nous venons de le dire des monts Ourals; mais comme cette roche
tient ici le côté méridionale de la chaîne Sibérienne, et que nous
ne lui connaissons point ce côté sur le reste de sa longueur, il se
pourrait que le jaspre y fût aussi abondant. Il faudrait, au reste, bien
plus de fouilles et d observations pour établir quelque chose de certain
sur l'ordre respectif qu'observent ces roches."
I would now ask, if in all this account of the gradation of rock from
the Oural mountains to the sandy coast of the Baltic, there is to be
observed any clear and distinctive mark of primitive, secondary, and
tertiary, mountains, farther than as one stratum may be considered as
either prior or posterior to another stratum, according to the order of
superposition in which they are found. We have every where evident marks
of the formation of strata by materials deposited originally in water;
for the most part, there is sufficient proof that this water in which
those materials had been deposited was the sea; we are likewise assured
that the operations of this living world producing animals, must
have, for a course of time, altogether inconceivably been exerted,
in preparing materials for this mass; and, lastly, from the changed
constitution of those masses, we may infer certain mineral operations
that melt the substance and alter the position of those horizontal
bodies. Such is the information which we may collect from this mineral
description of the Russian Dominions.
If we compare some of the Oural mountains with the general strata of
the Russian plains, then, as to the contained minerals, we may find a
certain diversity in those two places; at the same time, no greater
perhaps than may be found betwixt two different bodies in those same
plains, for example, chalk and flint. But when we consider those bodies
of the earth, or solid strata of the globe, in relation to their proper
structure and formation, we surely can find in this description nothing
on which may be founded any solid opinion with regard to a different
original, however important conclusions may perhaps be formed with
regard to the operations of the globe, from the peculiar appearances
found in alpine.
From this detail of what is found in the Oural mountains, and in the
gradation of country from those mountains to the plains of Russia, we
have several facts that are worthy of observation. First extensive
mountains of jasper. I have a specimen of this stone; it is striped red
and green like some of our marly strata. It has evidently been formed of
such argillaceous and siliceous materials, not only indurated, so as to
lose its character, as an argillaceous stone, but to have been brought
into that degree of fusion which produces perfect solidity. Of the same
kind are those hornstein rocks of the nature of flint, sometimes tending
to the nature of a fine sandstone. Here is the same induration of
sandstone by means of fusion, that in the argillaceous strata has
produced jasper. But oblique veins of jasper are represented as
traversing these last strata; now this is a fact which is not
conceivable in any other way, than by the injection or transfusion of
the fluid jasper among those masses of indurated strata.
All this belongs to the east side of the mountains. On the west, again,
we find the same species of strata; only these are not changed to such a
degree as to lose their original character or construction, and thus to
be termed differently in mineralogy.
Our author then proceeds. (p. 53.)
"Nous pourrons parler plus décisivement sur les _montagnes secondaires
et tertiaires_ de l'Empire, et c'est de celles-là, de la nature, de
l'arrangement et du contenu de leurs couches, des grandes inégalités et
de la forme du continent d'Europe et d'Asie, que l'on peut tirer avec
plus de confiance quelques lumières sur les changemens arrivés aux
terres habitables. Ces deux ordres de montagnes présentent la chronique
de notre globe la plus ancienne, la moins sujette aux falsifications, et
en même-tems plus lisible que le caractère des chaînes primitives;
ce font les archives de la nature, antérieures aux lettres et aux
traditions les plus reculées, qu'il étoit réservé à notre siècle
observateur de feuiller, de commenter, et de mettre au jour, mais que
plusieurs siècles après le nôtre n'épuiseront pas.
"Dans toute l'étendue de vastes dominations Russes, aussi bien que
dans l'Europe entière, les observateurs attentifs ont remarqué
que généralement la band schisteuse des grandes chaînes se trouve
immédiatement recouverte ou cottée par la _bande calcaire_. Celle-ci
forme deux ordres de montagnes, très-différentes par la hauteur, la
situation de leurs couches, et la composition de la pierre calcaire qui
les compose; différence qui est très-évidente dans cette bande calcaire
qui forme la lisière occidentale de toute la chaîne Ouralique, et dont
le plan s'étend par tout le plat pays de la Russie. L'on observerait
la même chose à l'orient de la chaîne, et dans toute l'étendue de la
Sibérie, si les couches calcaires horizontales n'y étaient recouvertes
par les dépôts postérieures, de façon qu'il ne paraît à la surface que
les parties les plus faillantes de la bande, et si ce pays n'étoit trop
nouvellement cultivé et trop peu exploité par des fouilles et autres
opérations, que des hommes industrieux ont pratiqué dans les pays
anciennement habités. Ce que je vais exposer sur les deux ordres de
montagnes calcaires, se rapportera donc principalement à celles qui sont
à l'occident de la chaîne Ouralique.
"Ce côté de la dite chaîne consiste sur cinquante à cent verstes de
largeur, de roche calcaire solide, d'un grain uni, qui tantôt ne
contient aucune trace de productions marines, tantôt n'en conserve
que des empreintes aussi légères qu'éparses. Cette roche s'élève en
montagnes d'une hauteur très-considérable, irrégulières, rapides, et
coupées de vallons escarpés. Ses couches, généralement épaisses, ne sont
point de niveau, mais très-inclinées à l'horizon, paralleles, pour la
plupart, à la direction de la chaîne, qui est aussi ordinairement celle
de la bande schisteuse;--au lieu que du côté de l'orient les couches
calcaires sont au sens de la chaîne en direction plus ou moins
approchante de l'angle droite. L'on trouve dans ces hautes montagnes
calcaires de fréquentes grottes et cavernes très-remarquables, tant
par leur grandeur que par les belles congélations et crystallizations
stalactiques dont elles s'ornent. Quelques-unes de ces grottes ne
peuvent être attribuées qu'à quelque bouleversement des couches;
d'autres semblent devoir leur origine à l'écoulement des sources
souterraines qui ont amolli, rongé et charrié une partie de la roche qui
en étoit susceptible.
"En s'éloignant de la chaîne, on voit les couches calcaires s'aplanir
assez rapidement, prendre une position horizontale, et devenir
abondantes en toute forte de coquillages, de madrépores, et d'autres
dépouilles marines. Telles on les voit par-tout dans les vallées les
plus basses qui se trouvent aux pieds des montagnes (comme aux environs
de la rivière d'Oufa); telles aussi, elles occupent tout l'étendue de la
grande Russie, tant en collines qu'en plat pays; solides tantôt et comme
semées de productions marines; tantôt toutes composées de coquilles et
madrépores brisées, et de ce gravier calcaire qui se trouve toujours sur
les parages ou la mer abonde en pareilles productions; tantôt, enfin,
dissoutes en craie et en marines, et souvent entremêlées de couches de
gravier et de cailloux roulés."
How valuable for science to have naturalists who can distinguish
properly what they see, and describe intelligibly that which they
distinguish. In this description of the strata, from the chain of
mountains here considered as primitive, to the plains of Russia, which
are supposed to be of a tertiary formation, our naturalist presents us
with another species of strata, which he has distinguished, on the one
hand, in relation to the mountains at present in question, and on the
other, with regard to the strata in the plains, concerning which there
is at present no question at all. Now, let us see how these three things
are so connected in their nature, as to form properly the contiguous
links of the same chain.
The primary and tertiary masses are bodies perfectly disconnected;
and, without a medium by which they might be approached, they would be
considered as things differing in all respects, consequently as having
their origins of as opposite a nature as are their appearances. But the
nature and formation of those bodies are not left in this obscurity;
for, the secondary masses, which are interposed, participate so
precisely of what is truly opposite and characteristic in the primary
and tertiary masses, that it requires nothing more than to see this
distinction of things in its true light, to be persuaded, that in those
three different things we may perceive a certain gradation, which
here takes place among the works of nature, and forms three steps
distinguishable by a naturalist, although in reality nothing but the
variable measure of similar operations.
We are now to assimilate the primary and tertiary masses, which are so
extremely different, by means of the secondary masses, which is the
mean. The primary and tertiary differ in the following respects: The one
of these contains the relicts of organised bodies which are not observed
in the other. But in the species containing these distinguishable
bodies, the natural structure and position of the mass is little
affected, or not so much as to be called into doubt. This, however, is
not the case with the other; the species in which organised bodies do
not appear, is in general so indurated or consolidated in its structure,
and changed in its position, that this common origin of those masses is
by good naturalists, who have also carefully examined them, actually
denied. Now, the secondary masses may be considered, not only as
intermediate with respect to its actual place, as M. Pallas has
represented it, but as uniting together the primary and tertiary, or as
participating of the distinguishing characters of the other two. It
is homologated with the primitive mountains, in the solidity of its
substance and in the position of its strata; with the tertiary species,
again, in its containing marks of organised bodies. How far this view
of things is consistent with the theory of the earth now given, is
submitted to the consideration of the unprejudiced.
Let us see what our learned author has said farther on this subject,
(page 65).
"Je dois parler d'un ordre de montagnes très-certainement postérieur aux
couches marines, puisque celles-ci, généralement lui servent de base.
On n'a point jusqu'ici observé une suite de ces _montagnes tertiaires_,
effet des catastrophes les plus modernes de notre globe, si marquée
et si puissante, que celle qui accompagne la chaine Ouralique ou côté
occidentale fur tout la longueur. Cette suite de montagnes, pour la
plupart composées de grais, de marnes rougeâtres, entremêlées de couches
diversement mixtes, forme une chaîne par-tout séparée par une vallée
plus ou moins large de la bande de roche calcaire, dont nous avons
parlé. Sillonnée et entrecoupée de fréquens vallons, elles s'élève
souvent à plus de cent toises perpendiculaires, se répand vers les
plaines de la Russie en traînées de collines, qui séparent les rivières,
en accompagnant généralement la rive boréale ou occidentale, et dégénère
enfin en déserts sableux qui occupent de grands espaces, et s'étendent
surtout par longues bandes parallèles aux principales traces qui suivent
les cours des rivieres. La principale force de ces montagnes tertiaires
est plus près de la chaîne primitive par-tout le gouvernement
d'Orenbourg et la Permie, ou elle consiste principalement en grais, et
contient un fond inépuisable de mines de cuivre sableuses, argileuses,
et autres qui se voient ordinairement dans les couches horizontales.
Plus loin, vers la plaine, sont des suites de collines toutes marneuses,
qui abondent autant en pierres gypseuses, que les autres en minerais
cuivreux. Je n'entre pas dans le détail de celles-ci, qui indiquent
sur-tout les sources salines; mais je dois dire des premières, qui
abondent le plus et dont les plus hautes élévations des plaines, même
celle de Moscou, sont formées, qu'elles contiennent très-peu de traces
de productions marines, et jamais des amas entiers de ces corps, tels
qu'une mer reposée pendant des siècles de suite a pu les accumuler dans
les bancs calcaires. Rien, au contraire, de plus abondant dans ces
montagnes de grais stratifié sur l'ancien plan calcaire, que des troncs
d'arbres entières et des fragmens de bois pétrifié, souvent minéralisé
par le cuivre ou le fer; des impressions de troncs de palmires, de
tiges de plantes, de roseau, et de quelques fruits étrangers; enfin des
ossemens d'animaux terrestres, si rares dans les couches calcaires. Les
bois pétrifiés se trouvent jusques dans les collines de sable de la
plaine; l'on en tire, entr'autres, des hauteurs sablonneuses aux
environs de Sysran sur la Volga, changés en queux très-fin, qui a
conservé jusqu'à la texture organique du bois, et remarquables sur-tout
par les traces très-évidentes de ces vers rongeurs qui attaquent les
vaisseaux, les pilotis et autres bois trempés dans la mer, et qui sont
proprement originaires de la mer des Indes."
This philosopher has now given us a view of what, according to the
present fashion of mineral philosophy, he has termed _montagnes
primitives, secondaires, et tertiaires_. The first consists in masses
and strata, much indurated and consolidated, and greatly displaced in
their position; but the character of which is chiefly taken from this,
that they contain not any visible mark of animal or vegetable bodies.
The second are formed in a great measure of marine productions, are
often no less consolidated than those of the first class, and frequently
no less changed in their natural shape and situation.
The third again have for character, according to this learned theorist,
the containing of those organised bodies which are proper to the earth,
instead of those which in the second class had belonged to the sea;
in other respects, surely there is no essential difference. It is not
pretended that these tertiary strata had any other origin, than that of
having been deposited in water; it is not so much as suspected, that
this water had been any other than that of the sea; the few marine
bodies which M. Pallas here acknowledges, goes at least to prove this
fact: and with regard to the mineral operations which had been employed
in consolidating those water formed strata, it is impossible not to be
convinced that every effect visible in the other two are here also to be
perceived.
From this view of mineral bodies, taken from the extensive observations
of the Russian dominions, and from the suppositions of geologists in
relation to those appearances, we should be led to conclude that the
globe of this earth had been originally nothing but an ocean, a world
containing neither plant nor animal to live, to grow and propagate its
species. In following a system founded on those appearances, we must
next suppose, that to the sterile unorganised world there had succeeded
an ocean stored with fish of every species. Here it would be proper to
inquire what sustained those aquatic animals; for, in such a system as
this, there is no provision made for continuing the life even of the
individuals, far less of feeding the species while, in an almost
infinite succession of individuals, they should form a continent of land
almost composed of their _exuviae_.
If fish can be fed upon water and stone; if siliceous bodies can, by
the digesting powers of animals, be converted into argillaceous and
calcareous earths; and if inflammable matter can be prepared without the
intervention of vegetable bodies, we might erect a system in which this
should be the natural order of things. But to form a system in direct
opposition to every order of nature that we know, merely because we may
suppose another order of things different from the laws of nature which
we observe, would be as inconsistent with the rules of reasoning in
science, by which the speculations of philosophy are directed, as it
would be contrary to common sense, by which the affairs of mankind are
conducted.
Still, however, to pursue our visionary system, after a continent had
been formed from the relicts of those animals, living, growing, and
propagating, during an indefinite series of ages, plants at last are
formed; and, what is no less wonderful, those animals which had formed
the earth then disappear; but, in compensation, we are to suppose, I
presume, that terrestrial animals began. Let us now reason from those
facts, without either constraining nature, which we know, or forming
visionary systems, with regard to things which are unknown. It would
appear, that at one period of time, or in one place, the matter of the
globe may be deposited, in strata, without containing any organised
bodies; at another time, or in another place, much animal matter may be
deposited in strata, without any vegetable substance there appearing;
but at another period, or at another time, strata may be formed with
much vegetable matter, while there is hardly to be observed any animal
body. What then are we to conclude upon the whole? That nature, forming
strata, is subject to vicissitudes; and that it is not always the same
regular operation with respect to the materials, although always forming
strata upon the same principles. Consequently, upon the same spot in
the sea, different materials may be accumulated at different periods of
time, and, conversely, the same or similar materials may be collected in
different places at the same time. Nothing more follows strictly from
the facts on which we now are reasoning; and this is a conclusion which
will be verified by every appearance, so far as I know.
Of this I am certain, that in a very little space of this country, in
many places, such a course of things is to be perceived. Nothing so
common as to find alternated, over and over again, beds of sand-stone
without animal bodies, beds of coal and schistus abounding with
vegetable bodies, beds of lime-stone formed of shells and corals, and
beds or particular strata of iron-stone containing sometimes vegetable
sometimes animal bodies, or both. Here, indeed, the strata are most
commonly inclined; it is seldom they are horizontal; consequently, as
across the whole country, all the strata come up to the day, and may be
seen in the beds of our rivers, we have an opportunity of observing that
great variety which is in nature, and which we are not able to explain.
This only is certain, from what we see, that there is nothing formed
in one epoch of nature, but what has been repeated in another, however
dissimilar may be the operations which had intervened between those
several epochs.
It must not be alleged, that the heights of the Oural mountains, or the
hardness of their rocks, make an essential distinction between them
and the argillaceous or arenaceous strata of the plains; solidity and
hardness, as well as changes in their height and natural position, has
been superinduced in operations posterior to the collection of those
masses,--operations which may be formed in various degrees, even in the
different parts of the same mass. If this is the case, there can be no
difficulty in conceiving a stratum, which appears to be argillaceous
or marly in the plains, to be found jasper in the Oural mountains. But
there is nothing in the Oural mountains, that may not be found some
where or other in the plains, although the soft and easily decomposing
argillaceous strata be not found upon the Oural mountains, or the Alps,
for this reason, that had those mountains been formed of such materials,
there had not been a mountain there at this day.
But surely the greatest possible error, with regard to the philosophy of
this earth, would be to confound the sediment of a river with the strata
of the globe; bodies deposited upon the surface of the earth, with those
sunk at the bottom of the sea; and things which only form the travelled
or transported soil, with those which constitute the substratum or the
solid earth. How far M. Pallas has committed this oversight, I leave
others to determine. After mentioning those strata in which wood is
found petrified, and metallic minerals formed, he thus proceeds, (page
69).
"Dans ces mêmes dépôts sableux et souvent limoneux, gisent les restes
des grands animaux de l'Inde: ces ossemens d'éléphans, de rhinocéros, de
buffles monstrueux, dont on déterre tous les jours un si grand nombre,
et qui font l'admiration des curieux. En Sibérie, où l'on à découvert le
long de presque toutes les rivières ces restes d'animaux étrangers,
et l'ivoire même bien conservé en si grande abondance, qu'il forme un
article de commerce, en Sibérie, dis je, c'est aussi la couche la plus
moderne de limon sablonneux qui leur sert de sépulture, et nulle part
ces monumens étrangers sont si frequens, qu'aux endroits où la grande
chaine, qui domine surtout la frontière méridionale de la Sibérie, offre
quelque dépression, quelque ouverture considérable.
"Ces grands ossemens, tantôt épars tantôt entassés par squelettes,
et même par hécatombes, considérée dans leurs sites naturels, m'ont
sur-tout convaincu de la réalité d'un déluge arrivé sur notre terre,
d'une catastrophe, dont j'avoue n'avoir pu concevoir la vraisemblance
avant d'avoir parcouru ces places, et vu, par moi-même, tout ce qui peut
y servir de preuve à cet évènement mémorable[24]. Une infinité de ces
ossemens couchés dans des lits mêlés de petites tellines calcinées, d'os
de poissons, de glossopètres, de bois chargés d'ocre, etc. prouve déjà
qu'ils ont été transportés par des inondations. Mais la carcasse d'un
rhinocéros, trouvé avec sa peau entière, des restes de tendons, de
ligamens, et de cartilages, dans les terres glacées des bords du
Viloûi, dont j'ai déposé les parties les mieux conservées au cabinet de
l'Académie, forme encore une preuve convaincante que ce devait être
un mouvement d'inondation des plus violens et des plus rapides, qui
entraîna jadis ces cadavres vers nos climats glacés, avant que la
corruption eût le tems, d'en détruire les parties molles. Il seroit à
souhaiter qu'un observateur parvint aux montagnes qui occupent l'espace
entre les fleuves Indighirka et Koylma où selon le rapport des
chasseurs, de semblables carcasses d'éléphans et d'autres animaux
gigantesques encore revêtues de leurs peaux, ont été remarquées à
plusieurs reprises."
[Note 24: Voyez le Mémoire, imprimé dans le XVII. volume des nouveaux
Commentaires de l'Académie Imperiale de Petersbourgh.]
The question here turns upon this, Are the sea shells and glossopetrae,
which are thus found deposited along with those skeletons, in their
natural state, or are they petrified and mineralised. If the productions
of the sea shall here be found collected along with bodies belonging to
the surface of the earth, and which had never been within the limits of
the sea, this would surely announce to us some strange catastrophe,
of which it would be difficult, perhaps, to form a notion; if, on the
contrary, those marine productions belong to the solid strata of the
earth, in the resolution or decay of which they had been set at liberty,
and were transported in the floods, our author would have no reason from
those appearances to conclude, there had existed any other deluge than
those produced by the waters of the land[25].
[Note 25: Since writing this, I find my doubts in a great measure
resolved, in reading M. Pallas's Journal, translated from the German by
M. Gauthier de la Peyronie. What I had suspected is, I think, confirmed
in the distinct account which M. Pallas has given of those occasions
in which the bones of land animals and marine objects are found buried
together. The marine objects are mineralised; consequently, they have
proceeded from the decomposition of the solid strata; and, having been
travelled in the running water of the surface of the earth, they must
have been deposited in those beds of rivers, which now are dry, alongst
with the bones, or the entire bodies of terrestrial animals, the remains
of which are now found there. This argument, from the state of those
marine bodies will not be allowed, perhaps by the generality of
mineralists, who attribute to the operations of water every species of
petrifaction or mineralisation; but, until some species of proof be
given with regard to the truth of that theory, which vulgar error first
suggested, I must reason from a theory, in proof of which I have given
clear examples, and, I think, irrefragable arguments, which shall be
more and more illustrated. Thus may be removed the necessity of a
general deluge, or any great catastrophe, in order to bring together
things so foreign to each other; but at the same time we would ascertain
this fact, That formerly the Elephant and Rhinoceros had lived in
Siberia. (See Voyage de Pallas, Tom. II. p. 377 and 403.)]
Having thus endeavoured to remove this prevailing prejudice, of there
being primitive parts in this earth, parts of which the composition and
constitution are not to be explained upon the principles of natural
philosophy, it will be proper to inquire, how far there may be in the
theory, which has now been given, principles by which may be explained
those appearances that have led natural philosophers to form
conclusions, of there being in this earth parts whose origin may not be
traced; and of there being parts whose origin may not be explained upon
the same principles which apply so well to all the rest.
CHAP. V.
Concerning that which may be termed the Primary Part of the Present
Earth.
In the present theory, it is maintained, that there is no part of the
earth which has not had the same origin, so far as this consists in that
earth being collected at the bottom of the sea, and afterwards produced,
as land, along with masses of melted substances, by the operation of
mineral causes. But, though all those things be similar, or equal, as to
the manner of their production, they are far from being so with regard
to the periods of their original composition, or to the subsequent
operations which they may have undergone.
There is a certain order established for the progress of nature, for the
succession of things, and for the circulation of matter upon the surface
of this globe; and, the order of time is associated with this change of
things. But it is not in equal portions that time is thus combined with
dissimilar things, nor always found, in our estimation, as equally
accompanying those which we reckon similar. The succession of light and
darkness is that which, in those operations, appears to us most steady;
the alternation of heat and cold comes next, but not with equal
regularity in its periods. The succession of wet and dry upon the
surface of the earth, though equally the work of nature and the effect
of regular causes, is often to us irregular, when we look for equal
periods in the course of things which are unequal. It is by equalities
that we find order in things, and we wish to find order every where.
The present object of our contemplation is the alternation of land
and water upon the surface of this globe. It is only in knowing this
succession of things, that natural appearances can be explained; and
it is only from the examination of those appearances, that any certain
knowledge of this operation is to be obtained. But how shall we acquire
the knowledge of a system calculated for millions, not of years only,
nor of the ages of man, but of the races of men, and the successions of
empires? There is no question here with regard to the memory of man, of
any human record, which continues the memory of man from age to age; we
must read the transactions of time past, in the present state of natural
bodies; and, for the reading of this character, we have nothing but
the laws of nature, established in the science of man by his inductive
reasoning.
It has been in reasoning after this manner, that I have endeavoured to
prove, that every thing which we now behold, of the solid parts of this
earth, had been formerly at the bottom of the sea; and that there is, in
the constitution of this globe, a power for interchanging sea and land.
If this shall be admitted as a just view of the system of this globe,
we may next examine, how far there are to be found any marks of certain
parts of our earth having more than once undergone that change of
posture, or vicissitude of things, and of having had reiterated
operations of the mineral kingdom changing their substance, as well as
altering their positions in relation to the atmosphere and sea.
Besides the gradual decay of solid land, exposed to the silent
influences of the atmosphere, and to the violent operations of the
waters moving upon the surface of the earth, there is a more sudden
destruction that may be supposed to happen sometimes to our continents
of land. In order to see this, it must be considered, that the
continents of our earth are only raised above the level of the sea by
the expansion of matter, placed below that land, and rarified in that
place: We may thus consider our land as placed upon pillars, which may
break, and thus restore the ancient situation of things when this land
had been originally collected at the bottom of the ocean. It is not here
inquired by what mechanism this operation is to be performed; it is
certainly by the exertion of a subterranean power that the land is
elevated from the place in which it had been formed; and nothing is more
natural than to suppose the supports of the land in time to fail, or be
destroyed in the course of mineral operations which are to us unknown.
In that case, whatever were remaining of that land, which had for
millions of ages past sustained plants and animals, would again be
placed at the bottom of the sea; and strata of every different species
might be deposited again upon that mass, which, from an atmospheric
situation, is now supposed to be lower than the surface of the sea.
Such a compound mass might be again resuscitated, or restored with the
new superincumbent strata, consolidated in their texture and inclined in
their position. In that case, the inferior mass must have undergone a
double course of mineral changes and displacement; consequently, the
effect of subterranean heat or fusion must be more apparent in this
mass, and the marks of its original formation more and more obliterated.
If, in examining our land, we shall find a mass of matter which had been
evidently formed originally in the ordinary manner of stratification,
but which is now extremely distorted in its structure, and displaced in
its position,--which is also extremely consolidated in its mass, and
variously changed in its composition,--which therefore has the marks
of its original or marine composition extremely obliterated, and many
subsequent veins of melted mineral matter interjected; we should then
reason to suppose that here were masses of matter which, though not
different in their origin from those that are gradually deposited at the
bottom of the ocean, have been more acted upon by subterranean heat and
the expanding power, that is to say, have been changed in a greater
degree by the operations of the mineral region. If this conclusion shall
be thought reasonable, then here is an explanation of all the peculiar
appearances of the alpine schistus masses of our land, those parts which
have been erroneously considered as primitive in the constitution of the
earth.
We are thus led to suppose, that some parts of our earth may have
undergone the vicissitudes of sea and land more than once, having been
changed from the summit of a continent to the bottom of the sea, and
again erected, with the rest of that bottom, into the place of land. In
that case, appearances might be found to induce natural philosophers to
conclude that there were in our land primary parts, which had not the
marine origin which is generally to be acknowledged in the structure
of this earth; and, by finding other masses, of marine origin,
superincumbent upon those primary mountains, they might make strange
suppositions in order to explain those natural appearances.
Let us now see what has been advanced by those philosophers who, though
they term these parts of the earth _primordial_, and not _primitive_, at
the same time appear to deny to those parts an origin analogous to that
of their secondary mountains, or strata that are aquiform in their
construction.
M. de Luc, after having long believed that the strata of the Alps had
been formed like those of the low countries, at the bottom of the sea,
gives an account of the occasion by which he was first confirmed in the
opposite opinion.[26] Like a true philosopher, he gives us the reason of
this change.
[Note 26: Lettres Physique et Morales sur l'Histoire de la Terre, tom.
2. pag. 206.]
"Ce fut une espèce de _montagne_ très commune, et que j'avois souvent
examinée qui dessilla mes yeux. La pierre qui la compose est de
la classe appellée _schiste_; son caractère générique est d'être
_feuilletée_; elle renferme _l'ardoise_ dont on couvre les toits. Ces
_feuillets_ minces, qu'on peut prendre pour des _couches_, et qui le
font en effet dans quelques pierres de ce genre, rappelloient toujours
l'idée vague de dépôts des eaux. Mais il y a des masses dont la
composition est plutôt par fibres que par feuillets, et dont le moëllon
ressemble aux copeaux de bois d'un chantier. Le plus souvent aussi les
feuillets sont situés en toute suite de sens dans une même _montagne_,
et quelquefois même verticalement, Enfin il s'en trouve de si tortillés,
qu'il est impossible de les regarder comme des dépôts de l'eau.
"Ce fut donc cette espèce de montagne qui me persuada la première
que toutes les montagnes n'avoient pas une même origine. Le lieu où
j'abjurai mon erreur, étoit un de ces grands _chantiers_ pétrifiés, qui,
par la variété du tortillement, et des zig-zags des fibres du moëllon
qui le composoit, attira singulièrement mon attention. C'étoit un sort
grand talus qui venoit d'une face escarpée; j'y montai pour m'approcher
du rocher, et je remarquai, avec étonnement, des multitudes de paquets
enchevêtrés les uns dans les autres, sans ordre ni direction fixe; les
uns presqu'en rouleaux; les autres en zig-zag; et même ce qui, séparé de
la montagne, eût peu être pris pour des _couches_, le trouvoit incliné
de toute manière dans cette même face de rocher. _Non_, me dis-je alors
à moi-même; _non, l'eau n'a pu faire cette montagne.... Ni celle-là
donc_, ajoutai-je en regardant ailleurs.... _Et pourquoi mieux celle-là?
Pourquoi toutes les montagnes devroient-elles être le produit des eaux,
seulement parce qu'il y en a quelques-unes qui annoncent cette origine_?
En effet, puis qu'on n'a songé aux eaux, comme cause des montagnes,
que par les preuves évidentes que quelques-unes offroient de cette
formation; pourquoi étendre cette conséquence à toutes, s'il y en
a beaucoup qui manquent de ces caractères? C'est comme le dit Mr.
d'Alembert, qu'on généralise ses premières remarques l'instant d'apres
qu'on ne remarquoit rien."
Science is indebted to this author for giving us so clear a picture
of natural appearances, and of his own reasoning upon those facts, in
forming his opinion; he thus leads astray no person of sound judgment,
although he may be in error. The disposition of things in the present
case are such, that, reasoning from his principles, this author could
not see the truth; because he had not been persuaded, that aquiform
strata could have been so changed by the chemical power of fusion, and
the mechanical force of bending while in a certain state of softness.
But though, in this case, the reasoning of this philosopher is to be
justified, so far as he proceeded upon principles which could not lead
him to the truth, his conduct is not so irreproachable in applying them
to cases by which their fallacy might have been detected. This author
acknowledges calcareous strata to be aquiform in their original; but,
in those mountains which he has so much examined, he will find those
aquiform bodies have undergone the same species of changes, which made
him conclude that those schistus mountains had not been truly aquiform,
as he at first had thought them. This would have led him to reason back
upon his principles, and to say, _If one species of strata may be thus
changed in its texture, and its shape, may not another be equally so?
Therefore, may not the origin of both be similar_?
But least I should do injustice to this author, to whom we are indebted
for many valuable observations in natural history, I shall transcribe
what he has said upon the subject, being persuaded that my readers will
not think this improper in me, or impertinent to the argument.
"Quand nous fumes une fois persuadés que la mer n'avoit pas fait
toutes les _montagnes_, nous entreprîmes de découvrir les caractères
distinctifs de celles qui lui devoient leur origine; et s'il étoit, par
exemple, des matières qui leur fussent propres. Mais nous y trouvâmes
les mêmes difficultés qu'on rencontre dans tout ce qu'on veut classer
dans la nature. On peut bien distinguer entr'elles les choses qui
ont fortement l'empreinte de leur classe; mais les confins échappent
toujours.
"C'est là, pour le dire en passant, ce qui a pu conduire quelques
philosophes à imaginer cette _chaîne des êtres_ où ils supposent,
que, de la pierre à l'homme et plus haut, les nuances sont réellement
imperceptibles. Comme si, quoique les limites soyent cachées à nos sens,
notre intelligence ne nous disoit pas, qu'il y a un _saut_, une distance
même infinie, entre le plus petit degré d'organization _propageante_,
et la matière unie par la simple cohésion: entre le plus petit degré de
_sensibilité_, et la matière insensible: entre la plus petite capacité
d'observer et de transmettre ses observations, et l'instinct constamment
le même dans l'espèce. Toutes ces différences tranchées existent dans la
nature; mais notre incapacité de rien connoître à fond, et la necessité
où nous sommes de juger de tout sur des apparences, nous fait perdre
presque toutes les limites, parce que sur ces bords, la plupart des
phénomènes sont équivoques. Ainsi la plante nous paroît se rapprocher de
la pierre, mais n'en approche jamais réellement.
"On éprouve la même difficulté à classer les montagnes; et quoique
depuis quelque tems plusieurs naturalistes ayent aussi observé qu'elles
n'ont pas toutes la même origine, je ne vois pas qu'on soit parvenu à
fixer des caractères infaillibles, pour les placer sûrement toutes dans
leurs classes particulières.
"Après avoir examiné attentivement cet objet, d'après les phénomènes que
j'ai moi-même observés, et ce que j'ai appris par les observations des
autres; j'ai vu que c'étoit là un champ très vaste, quand on vouloit
l'embrasser en entier, et trop vaste pour moi, qui n'étoit pas libre d'y
consacrer tout le tems qu'il exige. Je me suis donc replié sur mon objet
principal, savoir _la cause qui a laissé des dépouilles marines dans nos
continens_, et l'examen des hypothèses sur cette matière.
"Les phénomènes ainsi limités, se réduisent à ceci: qu'il y a dans nos
continens des montagnes visiblement formées par des _dépôts successifs
de la mer_ et a l'égard des quelles il n'y a besoin de rien imaginer, si
ce n'est la manière dont elles en sont sorties: qu'il y en a d'autres au
contraire, qui ne portent aucun des caractères de cette cause, et qui,
si elles ont été produites dans la _mer_, doivent être l'effet de toute
autre cause que de simples dépôts successifs, et avoir même précédé
l'existence des animaux marins. J'abandonne donc les classes confuses
où ces caractères sont équivoques, jusqu'à ce qu'elles servent à fonder
quelque hypothèse; ayant assez de ces deux classes très distinctes pour
examiner d'apres elles tous les systèmes qui me sont connus.
"Là où ces deux classes de montagnes sont mêlées, on remarque que celles
qui sont formées par _couches_, et qui renferment des _corps marins_,
recouvrent souvent celles de l'autre classe, mais n'en sont jamais
recouvertes. On a donc naturellement conclu, que lors même que la _mer_
auroit en quelque part à la formation des montagnes où l'on ne reconnoît
pas son caractère, celles auxquelles elle a travaillé seule, en enlevant
des matières dans certaines parties de son fond et les déposant dans
d'autres, font au moins les dernières formées. On les a donc nommées
_secondaires_, et les autres _primitives_.
"J'adopterai la première de ces expressions; car c'est la même qui nous
étoit venu à l'esprit à mon frère, et à moi longtemps avant que nous
l'eussions vue employer; mais je substituerai celle de _primordiales à_
_primitives_ pour l'autre classe de _montagnes_, afin de ne rien décider
sur leur origine. Il est des _montagnes_, dont jusqu'à present on n'a pu
démêler la cause: voila le fait. Je ne dirai donc pas qu'elles ont
été créées ainsi, parce qu'en physique je ne dois pas employer des
expressions sur lesquelles on ne s'entend pas. Sans doute cependant,
que l'histoire naturelle ni la physique ne nous conduisent nullement à
croire que notre globe ait existé de toute éternité; et lorsqu'il prit
naissance, il fallut bien que la matière qui le composa fut de quelque
nature, ou sous quelque première forme intégrante. Rien donc jusqu'ici
n'empêche d'admettre que ces _montagnes_ que je nommerai _primordiales_,
ne soient réellement _primitives_; je penche même pour cette opinion
à l'égard de quelques unes. Mais il y a une très grande variété
entr'elles; et quoiqu'elles soyent toutes également exclues de la classe
_secondaire_, elles ne sont pas toutes semblables: il y en a même un
grand nombre dont les matières ont une certaine configuration qui semble
annoncer qu'elles ayent été molles et durcies ensuite, quoique par
une toute autre cause que celle qui a agi pour former les montagnes
secondaires."
Here I would beg leave to call the attention of philosophers to this
observation of a naturalist who explains all petrification, and the
consolidation of strata by aqueous infiltration. If he has here found
reason to conclude that, in those primordial parts of the earth, there
are a great number which, from their present configuration, must have
been in a soft state and then hardened, and this by a quite different
cause from that which he supposes had produced the consolidation and
hardness of the secondary parts; this is entering precisely into my
views of the subject, in ascribing all the consolidation of the earth,
whether primary or secondary, to one general cause, and in tracing this
cause, from its effects, to be no other than the fusion of those bodies.
It must be evident, that if this philosopher has seen good reason for
concluding such a softening cause, which had operated upon the primary
parts, to be quite different from that which he ascribes to the
consolidation of the secondary, which is the effect of water, it must
then, I say, be evident that the softening cause of the primary parts,
if not heat, by which every degree of fusion may be produced, must be an
occult cause, one which cannot be admitted into natural philosophy.
By thus choosing to consider mountains as of two distinct kinds, one
aquiform which is understood, and the other primordial which is not to
be known, we supersede the necessity of reconciling a theory with many
appearances in nature which otherwise might be extremely inconvenient
to our explanation, if not inconsistent with our system. Our author no
doubt has thus relieved himself from a considerable difficulty in the
philosophy of this earth, by saying here is a great part which is not
to be explained. But I would beg leave to observe, that this form of
discussion, with regard to a physical subject, is but a mere confession
of our ignorance, and has no tendency to clear up another part of the
subject of which one treats, however it may impress us with a favourable
opinion of the theorist, in allowing him all the candour of the
acknowledgement.
The general result of the reasoning which we now have quoted, and what
follows in his examination, seems to terminate in this; that there are
various different compositions of mountains which this author cannot
allow to be the production of the sea; but it is not upon account of
the matter of which they are formed, or of the particular mixture and
composition of those species of matter, of which the variety is almost
indefinite. According to this philosopher, the distinction that we are
to make of those primordial and secondary competitions, consists in
this, that the first are in such a shape and structure as cannot be
conceived to be formed by subsidence in water.
M. de Saussure has carefully examined those same objects; and he seems
inclined to think that they must have been the operation of the ocean;
not in the common manner of depositing strata, but in some other way by
crystallization. The present theory supposes all those masses formed
originally in the ordinary manner, by the deposits or subsidence
of materials transported in the waters, and that those strata were
afterwards changed by operations proper to the mineral regions.
But the subject of the present investigation goes farther, by inquiring
if, in the operations of the globe, a primary and secondary class of
bodies may be distinguished, so far as the one may have undergone the
operations of the globe, or the vicissitudes of sea and land, oftener
than the other, consequently must be anterior to the later productions
both in time and operation, although the original of all those bodies
be the same, and the operations of the earth, so far as we see in the
effects, always proceed upon the same principles. This is an extensive
view of nature to which few have turned their thoughts. But this is
a subject to which the observations described by this author have
evidently a reference.
In his 113th letter, he has given us a view of one of those parts of the
earth that are proper to be examined in determining this question so
important in the genealogy of land, although no ways concerned in
altering the principles upon which nature in forming continents must
proceed.
It is in describing the nature of the mountains about _Elbingerode_; and
he begins in ascending from Hefeld.
"Cette partie extérieure de la chaîne est _primordiale_: c'est du
_granit_ à _Hereld_ et au commencement de la route; puis quand on passe
dans d'autres vallées, on trouve les _schistes_ et la _roche grise_ dans
tout le pied des montagnes: mais des qu'on est arrivé à une certain
hauteur, on voit de la _pierre à chaux_ par couches étendue sur ces
matières; et c'est elle qui forme le sommet de ces mêmes montagnes;
tellement que la plaine élevée, qui conduit à _Elbingerode_, est
entièrement de _pierre à chaux_, excepté dans sa partie la plus haute ou
cette pierre est recouverte des mêmes _grès_ et sables _vitrescibles_
qui sont sur le schiste du Bruchberg et sur la _pierre à chaux_ dans la
_Hesse_ et le pays de Gottingue.
"Les environs d'Elbingerode étant plus bas que ces parties recouvertes
de matières vitrescibles, montrent la _pierre à chaux_ à nud; et l'on y
trouve de très beaux marbres, dont les nuances jaunes, rouges et vertes
sont souvent très vives, et embellies par les coupes des _corps marins_.
"Cependant le schiste n'est pas enseveli partout sous ces dépôts de la
mer; on le retrouve en quelques endroits, et même avec de _filons_.
"Ainsi au milieu de ces matières _calcaires_ qui forment le sol montueux
des environs _d'Elbingerode_, paroît encore le _schiste_ sur lequel
elles ont été déposées: Et en montant à la partie la plus élevée de
ces mêmes environs, on trouve que la _pierre à chaux_ est recouverte
elle-même d'une _pierre sableuse_ grise par couches, dans laquelle on
voit quantité de petits fragmens de _schiste_ posés de plat. C'est la
que se trouve une des mines de _fer_ dont le minerai va en partie à la
_Koningshutte_, mais en plus grande partie à la _Rothechutte_, qui n'est
qu'à une lieue de distance. On perce d'abord la couche sableuse; sous
elle se trouve de la _pierre à chaux_ grise; puis une couche de
_pierre à chaux ferrugineuse_, remplie de _corps marins_, et surtout
_d'entroques_: C'est cette _couche_ qui est ici le _minerai_; et elle
appartient à la formation de cette éminence comme toutes les autres
_couches_. Cette mine se nomme _bomshey_: elle n'est pas riche; mais
elle sert de _fondant_ aux matières ferrugineuses tirées des filons des
montagnes primordiales en même tems qu'elle leur ajoute son _fer_ dans
la fonte. A quelque distance de là on a percé un autre puits; qui a
transversé d'abord une sorte de pierre, que je ne saurois nommer, mais
qui ressemble fort à une _lave_ poreuse. Au dessous de cette couche on a
retrouvé la _pierre à chaux_ ordinaire; puis la _couche ferrugineuse_ y
continue; mais elle diffère un peu de ce qu'elle est dans l'autre mine,
une partie de sa substance étant convertie en _jaspe_.
"Mais ce qui est digne de la plus grande attention dans cette contrée,
est un filon peu distant nomme _Buchenberg_, qui appartient en partie au
Roi, et en partie à Mr. le Comte de _Wernigerode_. La montagne en cette
endroit montre une vallée artificielle de 70 à 80 pieds de profondeur,
de 20 à 30 de largeur dans le haut, et de 400 toises en étendue. C'est
le creusement qu'on a déjà fait en suivant ce _filon_ de _fer_, que l'on
continue à exploiter de la même manière sur les terres de Mr. le Comte
de _Wernigerode_. La matière propre de la montagne _est_ de _schiste_;
et la vallée qui se forme de nouveau à mesure qu'on enlève la _gangue_
du _filon_, a sûrement déjà existé dans la mer sous la forme d'une
_fente_, qui a été remplie, et en particulier des ingrédiens dont on
fait aujourd'hui le _fer_."
Here is a supposition of our author that corresponds to nothing which
has yet been observed any where else, so far as I know. It is concerning
a mineral vein, one which does not appear to differ in any respect from
other mineral veins, except in being worked in that open manner which
has given our author an idea of its being a valley. He then supposes
that valley (or rather empty vein) to have been in this mountain when at
the bottom of the sea, and that this mineral vein had then been filled
with those materials which now are found in that space between the two
sides of the separated rock. This is a very different operation from
that of infiltration, which is commonly supposed to be the method of
filling mineral veins; but, we shall soon see the reason why our author
has here deserted the common hypothesis, and has adopted another to
serve the occasion, without appearing to have considered how perfectly
inconsistent those two suppositions are to each other. That mineral
veins have been filled with matter in a fluid state, is acknowledged by
every body who has either looked at a mineral vein in the earth, or in a
cabinet specimen; mineralists and geologists, in general, suppose this
to have been done by means of solutions and concretions, a supposition
by no means warranted by appearances, which, on the contrary, in general
demonstrate that the materials of those veins had been introduced in the
fluid state of fusion. But here is a new idea with regard to the filling
of those veins; and, I would now beg the reader's attention to the facts
which follow in this interesting description, and which have suggested
that idea to our author.
"Quand cette matière accidentelle est enlevée, on voit la coupe du
_schiste_ des deux côtes de la _fente_, faisant un _toit_ et un _mur_,
parce que la _fente_ n'est pas absolument verticale: des qu'il y a
un peu d'inclinaison, on distingue un _toit_ et un mur, comme j'ai
l'honneur de l'expliquer à V.M. On ne connoît point encore l'étendue de
ce filon, ni dans sa profondeur, où l'on ne peut pas s'enfoncer beaucoup
de cette manière, ni dans la longueur, selon laquelle on continue à
l'exploiter.
"Voilà donc un _filon_, à la rigueur de la définition que j'en ai donné
à V.M. c'est à dire, une _fente_ dans la montagne naturelle, _comblée_
de _matière_ étrangère. Mais ce qu'il y a d'extraordinaire ici, c'est
que cette _matière_ vient de la _mer_: ce sont différentes _couches
aquiformes_, dont quelques unes sont remplies de _corps marins_. Il y
a des _couches_ d'une _terre martiale_ fort brune et sans liaison:
d'autres, au contraire toujours _martiales_, sont très dures et
renferment de très beau jaspe sanguin: d'autres enfin sont de vrai
_marbre_ gris veinées de rouge. C'est dans ce marbre que font les _corps
marins_, savoir des coquillages et des spongites; et il est lui-même
martial comme tout le reste: les mineurs le nomment _Kubrimen_, et ne
l'employent que comme un _fondant_ pour d'autres _minéraux de fer_.
"A ce _filon_, s'en joignent d'autres plus embarrassans. Ils viennent du
_toit_, qu'ils divisent par de larges _fentes_ comblées, aboutissantes
au _filon_ principale. Ils font de même _calcaires_ et marins faits par
_couches_; mais ces _couches_ ont une si grande inclinaison, que je ne
puis les comprendre: il faut qu'il y ait eu d'étranges bouleversemens
dans ces endroits-là[27].
[Note 27: Here, no doubt, are appearances which it is impossible to
explain by the theory of infiltration; it is the filling of mineral
veins, and their branches or ramifications, with marble containing marks
of marine objects. But, if we shall suppose this marble to have been in
the fluid state of fusion, as well as the iron-ore and jasper, we may
easily conceive it introduced into the principal vein and its branches.
The description here given of those appearances is by no means such as
to enable us to judge particularly of this case, which surely merits the
most accurate investigation, and which, I doubt not, will give physical
demonstration of the fusion of those mineral substances. I know that
shells have been found within the body of veins in Germany; but, a
stratification of those materials in a vein was never heard of before,
so far as I know.]
"Ces _fentes_ se sont faites, et ont été remplies, dans la _mer_;
puisque les matières qui les remplissent sont de la classe de ses dépôts
très connoissables, et qu'il contiennent des _dépouilles marines_. Mais
ce qui embarrasse alors c'est que les autres _filons_ ne soyent pas dans
le même cas. N'est ce point là encore un indice, que ces _fentes_ out
été d'abord et principalement remplies de matières, poussées du fond par
la même force qui secouoit les montagnes[28].
[Note 28: But what is this power by which matter is to be forced from
the bottom of the sea to the top of the mountains? For, unless we can
form some idea of that power which, as a cause, we ascribe to the
perceived effect, we either say nothing to the purpose, or we employ a
preternatural cause. It is not sufficient to imagine a power capable of
raising from the bottom of the sea the materials deposited in the abyss;
it is also necessary to find a power capable of softening bodies which
are hard, and of thus consolidating those masses which are formed of
loose or unconnected materials. Such a power, indeed, the present theory
assumes; and, so far as this shall be implied in the supposition of our
author, it will thus have received a certain conformation.]
"Ce _filon_ n'est pas le seul dans le _Hartz_ qui donne des signes
_marins_. Il y en a un autre, qui même se rapproche davantage de
la nature du commun des _filons_, et où l'on trouve aussi des
_coquillages_. C'est celui de _Haus-Hartzbergerzug_, pres de
_Clausthal_, où, dans les _Halles_ de quelques mines de plomb
abandonnées, et dans une forte _d'ardoise_, on trouve de petites
_moules_ ou _tellines_ striées, d'une espèce particulière que j'ai vue
dans des _ardoises secondaires d'Arotzen_ en _Waldek_ et de _Sombernon_
en _Bourgogne_. Il y a donc certainement quelques _filons_ faits par les
dépôts de la _mer_ dans les _fentes_ de montagnes _primordiales_; comme
au contraire il y a des _filons_ métalliques sans indices _marins_,
dans des montagnes évidemment _secondaires_, telles que celles de
_Derbyshire_, ou les _filons_ de _plomb_ traversent des couches de
_pierre à chaux_."
Here again our author seems to me to refute his own supposition, That a
chasm in the schistus rock may have existed at the bottom of the sea,
and been then filled from above with such materials as were transported
by the moving water to that place, is not impossible; but nobody, who
knows the nature of a common metallic vein, can ever suppose it to have
been filled in that manner. Our author then adds, "On ne fait réellement
que commencer dans ce genre d'observations, considérées quant à la
Cosmologie; ainsi il ne faut point désespérer que tout cela ne se
dévoile un jour, et que nous n'acquerrions ainsi un peu plus de
connoissance sur ce qui se passoit dans la _mer ancienne_.
"En revenant vers _Elbingerode_, nous retrouvâmes ces _schistes_, qui
paroissent au travers des _marbres:_ ils sont donc la continuation de la
masse _schisteuse_ à laquelle appartient le _filon_, dont je viens de
parler. Ce _filon_ à été formé dans une _fente_, restée ouverte et vide:
les dépôts de la _mer_ l'ont comblée, en même tems qu'ils formoient
les couches de _marbre_, qui sont à l'extérieur. En effet, ce _filon_
contient des _couches marines ferrugineuses_, de la même nature que
celles des collines calcaires voisines formées sur le schiste.
"Nous partîmes _d'Elbingerode_ dans l'après midi pour nous rapprocher
de Clausthal. Notre chemin fut encore quelque tems sur des sommités
_calcaires_; et avant que d'en sortir, nous trouvâmes une autre mine
singulière à _Arenfeld_. C'est encore un vrai _filon_; mais dans une
montagne de _pierre à chaux:_ C'est à-dire, que cette montagne a aussi
été _fendue_, et que la _fente_ a été remplie d'une _gangue_. La matière
de ce _filon_ est encore _calcaire_ en plus grande partie; mais
cette _pierre à chaux_ distincte est _ferrugineuse_, et parsemée de
concrétions de _jaspe_ comme celles _d'Elbingerode:_ on y trouve aussi
une matière verdâtre, qui, comme le _jaspe_, ne fait pas effervescence
avec l'eau forte."
Here is a phenomenon which is altogether incompatible with the theory
that this author has given us for the explanation of those appearances.
He supposes empty crevices in the schistus mountains at the bottom of
the sea; these crevices he supposes filled by the deposits of the sea,
at the same time, and with the same materials with which the lime-stone
strata were formed above the schistus mountains; but we find one of
those same veins in these secondary calcareous strata. Now, tho' we
should be disposed to allow, that, in the primordial mountain, of which
we are supposed not to know the origin, there might have been empty
crevices which were afterwards filled with materials transported by the
sea, this cannot be admitted as taking place in the loose or incoherent
materials deposited above the schistus. Consequently, this theory of our
author, which is evidently erroneous with regard to the veins in the
lime-stone, must, in the other case, be at least examined with a jealous
eye.
"Le haut de cette partie des montagnes _calcaires_ étoit encore
recouvert de _sable_ et de grès _vitrescibles_: et continuant à marcher,
sans aucune inflexion sensible, nous nous trouvâmes subitement sur les
_schistes_; d'où nous montâmes plus rapidement. Puis traversant quelques
petites vallées nous arrivâmes sur les montagnes qui appartiennent au
prolongement du _Brocken_ ou _Blocksberg_. La matière dominante est
alors le _granit_; mais il est tout en blocs le long de cette route, et
ces blocs se trouvent à une telle distance de tout sommité intacte de
cette pierre, qui est aisé de juger non seulement qu'ils ne sont pas
dans leur place originaire, mais encore qu'il ne sont arrivés là par
aucune des causes naturelles qui agissent dans les montagnes; savoir,
la pesanteur, la pente, et le cours des eaux. Ce sont donc de violentes
explosions qui ont dispersé ces blocs; et alors ils deviennent un
nouveau trait cosmologique de quelque importance: car rien ne se meut,
ni ne paroît s'être mu depuis bien des siècles, dans ces lieux qui
montrent tant de désordre: un tapis de verdure couvre tout, en
conservant les contours baroques du sol. Le bétail ne sauroit pâturer
dans de telles prairies; mais l'industrieux montagnard fait y
faucher[29].
[Note 29: M. de Saussure endeavours to explain those appearances of
transported blocks of granite by another cause; this is a certain
_debacle_ of the waters of the earth, which I do not understand. M. de
Luc again attempts to explain it by violent explosions; I suppose he
means those of a volcano. But he has not given us the evidence upon
which such an opinion may be founded, farther than by saying that those
blocks could not have come there by the natural operations of the
surface. By this must be meant, that, from the nearest summit of
granite, there is not, at present, any natural means by which these
blocks might be transported to that place. But it is not with the
present state of things that we are concerned, in explaining the
operations of a distant period. If the natural operations of the surface
change the shape of things, as is clearly proved by every natural
appearance, Why form an argument against a former transaction, upon the
circumstances of the present state of things? Our author does not
seem to perceive, that, from this mode of reasoning, there is is an
insuperable objection to his violent explosions having been employed in
producing those effects. For, had there been such a cause, the evidence
of this must have remained; if the surface of the earth does not undergo
great changes: If, again, this surface be in time much changed, How can
we judge from the present shape, what might have been the former posture
of things?
This author, indeed, does not allow much time for the natural operations
of the globe to change its surface; but, if things be not greatly
removed from the state in which the violent operations of the globe had
placed them, Why does he not point out to us the source of this great
disorder which he there perceives? From what explosion will be explained
the blocks of granite which are found upon the Jura, and which must have
come from the mass of _Mont Blanc_? If these dispersed blocks of
stone are to be explained by explosion, there must: have been similar
explosions in other countries where there is not the smallest appearance
of volcanic eruptions; for, around all our granite mountains, and I
believe all others, there are found many blocks of granite, traveled at
a great distance, and in all directions.]
"_Oberbruck_, ou nous avions été la précédente fois, se trouva sur notre
route, et nous y passames aussi la nuit, dans l'espérance de pouvoir
monter le lendemain sur le _Brocken_; mais il fut encore enveloppé de
nuages; ainsi nous continuâmes à marcher vers _Clausthal_, passant de
nouveau par le _Bruchberg_, où le _sable_ et ses gres recouvrent le
_schiste_; puis arrivant à une autre sommité, nous y trouvâmes la même
pierre _sableuse_ par couches, mêlée de parcelles de _schiste_, que nous
avions vue sur les montagnes _calcaires d'Elbingerode_. Il est donc
toujours plus certain que le sol primordial de toutes ces montagnes
existoit sous les eaux de l'ancienne mer; puisqu'il est recouvert de
diverses fortes de dépôts, connus pour appartenir à la _mer_; et que les
_fentes_ des _filons_ existoient dans cette _mer ancienne_; puisqu'elle
en a rempli elle-même quelques unes, et qu'elle a recouvert de ses
dépôts quelques autres _filons_ tout formés. Quant à celles des matières
de ces _filons_, qui ne paroissent pas être _marines_ (et c'est de
beaucoup la plus grande quantité), j'ai toujours plus de penchant d'en
attribuer une partie à l'opération des _feux souterreins_, à mesure que
je vois diminuer la probabilité de les assigner entièrement à _l'eau_.
Mais quoi-qu'il en soit, ces gangues ne font pas de même date que les
montagnes[30].
[Note 30: I most willingly admit the justness of our author's view, if
he thus perceives the operation of fire in the solids of our earth; but
it is not for the reasons he has given us for discovering it here more
than in other places; for there is not a mineral vein, (so far at least
as I have seen), in which the appearances may be explained by any thing
else besides the operation of fire or fusion. It is not easy to conceive
in what manner our author had conceived the opinions which he has
displayed in these letters. He had no opinion of this kind, or rather he
was persuaded that subterraneous fire had no hand in the formation of
this earth before he came to this place of the Hartz; here he finds
certain appearances, by which he is confirmed in his former opinion,
that water had operated in forming mineral veins; and then he forms the
idea that subterraneous fire may have operated also. But, before the
discovery of the chasms in the schistus mountains having been filled
with the stratified materials of the sea, How had he supposed veins to
be filled? If this philosopher had before no opinion of subterraneous
fire, as instrumental in that operation, How comes he now to change that
former opinion? For, unless it be the extraordinary manner of filling
these open crevices in the mountains by matter deposited immediately
from the sea, there is certainly no other appearance in this mineral
country of the Hartz, that may not be found in any other, only perhaps
upon a smaller scale.]
"Le lendemain de notre arrivée a _Clausthal_, qui étoit le 13e, nous
allâmes visiter d'autres mines de _fer_ en montagnes secondaires,
situées au côté opposé du Hartz. Elles sont auprès de _Grund_ l'une
des _villes de mines_, et près du lieu ou sortira la nouvelle _galerie
d'écoulement_ à laquelle on travaille, etc.
"Arrivés à _Grund_ les officiers mineurs vinrent, comme à l'ordinaire,
accompagner Mons. de _Reden_ aux _mines_ de leur département. Celles-ci,
sans être plus extraordinaires que celles qui nous avions vues à
_Elbingerod_, ou sans aider mieux jusqu'ici à expliquer ce qu'elles ont
toutes d'extraordinaire, nous donnent au moins des indices probables
de grands accidens. Ces montagnes de _Grund_ sont encore de l'espèce
remarquable, dont la base est de _schiste_, et le haut de _pierre à
chaux_. Les mines qu'on y exploit sont de _fer_, et se trouvent dans
cette matière _calcaire_; mais elles y sont sous des apparences
tout-à-fait étranges. La montagne où nous les vîmes principalement le
nomme _Iberg_. On y poursuit des masses de _pierre à fer_, de l'ensemble
desquelles les mineurs ne peuvent encore se rendre compte d'une manière
claire. Ils ont trouvé dans cette montagne des _ca__vernes_, qui
ressemblent à l'encaissement de _sillons_ déjà exploités, ou non formés;
c'est-à-dire, que ce sont des _fentes_ presque verticales, et vides, Le
_minerai_ qu'ils poursuivent est en _Rognons_; c'est à dire, en grandes
masses sans continuité décidée. Cependant ces masses semblent se
succéder dans la montagne suivant une certaine direction; tellement que
les mineurs savent déjà les chercher, par des indices d'habitude.
La substance de cette _pierre à fer_ particulière renferme des
crystallizations de diverses espèces. Il y a des _druses de quartz_, ou
de petits cristaux de quartz qui tapissent des cavités; il y a aussi du
_spath_ commun, et de celui qu'on nomme pesant; on y trouve enfin une
forte de crystallization nommée _Eisenman_ (_homme de fer_) par les
mineurs; se sont des amas de cristaux noir-âtres, qui ressemblent à
des groupes de grandes lentilles plattes, et ces cristaux sont
_ferrugineux_.
"Entre les signes de bouleversement que renferme ce lieu, est un
rocher nommé _Gebichensten_, qui est en _pierre à chaux_, ce que
_l'Ebrenbreitstein_ de _Coblentz_ est en pierre sableuse: c'est-à-dire,
que ses _couches_, remplies de _corps marins_, sont presque verticales;
ceux de ces corps qu'on y trouve en plus grande quantité, sont des
_madrépores_. Ce rocher s'élève comme un grand obélisque, au-dessus des
_cavernes_, dont j'ai parlé; montrant par le côté ses _couches_, qui se
trouvent, comme je l'ai dit, dans une situation presque verticale. Sa
base est déjà bien minée, tant par les _cavernes_, que par la _pierre
à fer_ qu'on en tire; et je ne me hasardai dessus, que parce que je me
dis, qu'il y a des millions contre un à parier, que ce n'est pas le
moment où il s'enfoncerait. Mais je n'en dirois pas autant, s'il
s'agissoit de m'y loger à demeure.
"Quoique tout ce lieu là soit fort remarquable, il se pourrait que ce
ne fut qu'un phénomène particulier. Les _cavernes_ peuvent devoir leur
origine à la même cause que celle de Schartzfeld; et le dérangement des
rochers supérieurs à des enfoncemens occasionnés par ces _cavernes_.
Rien n'est si difficile que de retracer aujourd'hui ces fortes
d'accidens à cause des changemens que le tems y a opérés. S'ils sont
arrivés sous les eaux de la _mer_, on conçoit aisément les altérations
qui ont dû succéder; et si c'est depuis que nos continens sont à sec,
les eaux encore, tant intérieures qu'extérieures, et la végétation, en
ont beaucoup changé l'aspect."
This author has a theory by which he explains to himself the former
residence of the sea, above the summits of our mountains; this,
however, is not the theory by which we are now endeavouring to explain
appearances; we must therefore be allowed to reason from our own
principles, in considering the facts here set forth by our author.
Nothing, I think, is more evident, than that in this mineral country of
the Hartz, we may find the clearest marks of fracture, elevation, and
dislocation of the strata, and of the introduction of foreign matter
among those separated bodies. All those appearances, our author would
have to be nothing but some particular accident, which is not to enter
into the physiology of the earth. I wish again to generalise these
facts, by finding them universal in relation to the globe, and
necessarily to be found in all the consolidated parts of our land.
It was not to refute our author's reasoning that I have here introduced
so much of his observations, but to give an extensive view of the
mineral structure of this interesting country. This therefore being
done, we now proceed to what is more peculiarly our business in this
place, or the immediate subject of investigation, viz. the distinction
of primary and secondary strata.
"Dans le voisinage de cette montagne, il y a une autre fort
intéressante, que je vis le jour suivant. Quoiqu'en traitant des
volcans, j'aie démontré que la formation des montagnes, par soulèvement,
étoit sans exemple dans les faits, et sans fondement dans la théorie, je
ne laisseroi pas de m'arrêter au phénomène que présente cette montagne;
parce qu'il prouvera directement que les _couches calcaires_ au moins,
ont été formées _à la hauteur ou elles sont_; c'est-a-dire qu'elles
n'ont pas été soulevées.
"Voulant prendre l'occasion de mon retour à _Hanovre_, pour traverser
les avant-corps du _Hartz_, dans quelque nouvelle direction; je résolus
de faire ce voyage à cheval, et de prendre ma route droite vers
_Hanovre_, au-travers des collines; ce qui me conduisit encore à _Grund_
puis à _Münchehof Brunshausen, Engelade, Winsenburg_ et _Alfeld_, où
enfin, traversant la _Leine_ j'entrai dans la grande route.
"Je quittai donc _Clausthal_ (et avec bien du regret) le 14 au matin;
et revenant d'abord à _Grund_, je le laissai sur ma droite, ainsi
que _l'Iberg_; et plus loin, du même côté, une autre montagne nommée
_Winterberg_ dont la base est _schiste_, et le sommet plus haut que
Clausthal, entièrement composé de _couches calcaires_. De _Grund_ je
montai vers une montagne nommée _Ost Kamp_; et je commençai là à donner
une attention particulière au sol. Le long de mon chemin, je ne trouvai
longtemps que des schistes, qui montroient leurs points en haut, comme à
l'ordinaire, et avec tous leurs tortillemens de feuillets. Mais arrivé
au haut de la montagne, j'y vis des carrières de _pierre à chaux_, où
les couches absolument régulières, et qui ont peu d'épaisseur sur le
_schiste_ suivent parfaitement les contours du _sommet_. Ces lits de
_pierre à chaux_ n'ont certainement pas été soulevés du fond de la _mer_
sur le dos des schistes; lors même qu'à cause de la grande inclinaison
des feuillets de ceux-ci on voudroit le attribuer à quelque révolution
telle que le _soulèvement_; (ce que je n'admettrois point). Car si ces
lits _calcaires_, ayant été faits au fond de la _mer_, avoyent été
soulevés avec les schistes, ne feroient-ils pas brisés et bouleversés
comme eux? Il est donc evident, que quoiqu'il soi arrivé au schiste qui
les porte, ces lits, et tous les autres de même genre qui sont au haut
de ces montagnes, ont été déposées au niveau où ils sont; et que
par conséquent la _mer_ les surpassoit alors. Ainsi le système de
soulèvement perd son but, s'il tend à expliquer pourquoi nous avons des
_couches_, formées par la mer, qui se trouvent maintenant si fort au
dessus de son niveau. Il est évident que ces _couches_ n'ont pas été
soulevées; mais que la _mer_ s'est _abaissée_. Or c'est là le grand
point cosmologique à expliquer: tous les autres, qui tiennent à la
structure de certaines montagnes inintelligibles, n'appartiendront qu'à
_l'histoire naturelle_, tant qu'ils ne se lieront pas avec celui-la."
Here are two things to be considered; the interesting facts described
by our author, and the inference that he would have us draw from those
facts. It would appear from the facts, that the body of schistus below,
and that of lime-stone above, had not undergone the same disordering
operations, or by no means in the same degree. But our author has formed
another conclusion; he says, that these lime-stone strata must have been
formed precisely in the place and order in which they lie at present;
and the reason for this is, because these strata appeared to him to
follow perfectly the contour of the summit of this mountain. Now, had
there been in the top of this mountain a deep hollow encompassed about
with the schistus rock; and had this cavity been now found filled with
horizontal strata, there might have been some shadow of reason for
supposing those strata to have been deposited upon the top of the
mountain. But to suppose, _first_, that shells and corals should be
deposited upon the convex summit of a mountain which was then covered by
the sea; _secondly_, that these moveable materials should remain upon
the summit, while the sea had changed its place; and, _lastly_, that
those shells and corals left by the sea upon the top of a mountain
should become strata of solid limestone, and have also metallic veins
in it, certainly holds of no principle of natural philosophy that I am
acquainted with. If, therefore, such an appearance as this were to be
employed either in illustration or confirmation of a theory, it
would itself require to be explained; but this is a task that this
cosmologists does not seem willing to undertake.
He has formed a hypothesis for explaining the general appearance of that
which was once the bottom of the sea being now found forming the summits
of our mountains; but surely this philosopher will acknowledge, that
those natural appearances, in any particular place, will be the same,
whether we suppose the bottom of the sea to have been raised, as in the
present theory, or the surface of the sea to have sunk according to his
hypothesis. For, it is equally easy to suppose a portion of the earth
to have been raised all this height, as to suppose all the rest of the
surface of the globe to have sunk an equal space, while a small portion
of the bottom of the sea, remaining here and there fixed in its place,
became the highest portion of the globe. Consequently, whatever evidence
this philosopher shall find in support of his theory of the present
earth, (a subject which it is not our purpose to examine) it cannot be
allowed that he has here brought any argument capable of disproving the
elevation of the bottom of the sea; a supposition which other theories
may require.
I would now observe, in relation to the present theory, that so far
as this author has reasoned justly from natural appearances, his
conclusions will be found to confirm the present supposition, that there
is to be perceived the distinction of primordial, and that of secondary,
in the masses of this earth, without altering the general theory either
with respect to the original formation of those masses, or to their
posterior production.
Here one of two things must be allowed; either that those strata
of schistus had been broken and distorted under a mass of other
superincumbent strata; or that those superincumbent strata had been
deposited upon the broken and distorted strata at the bottom of the sea.
Our author, who has examined the subject, inclines to think, that this
last has been the case. If, therefore, strata had been deposited upon
broken and bare rocks of schistus, it is probable that these had been
sunk in the sea after having been exposed to the atmosphere, and served
the purpose of land upon the globe.[31]
[Note 31: This is also supported by another very interesting observation
contained in this letter. M. de Luc observes, that in this country the
schistus is generally covered by strata of lime-stone, and that these
lime-stone strata are again covered with those of sand-stone, in which
are found a great many fragments of schistus lying flat. Therefore,
while those sand-stone strata were collecting at the bottom of the sea,
there had been rocks of schistus in some other place, from whence those
fragments bad been detached.]
An example of the same kind also occurs in the _Discours sur l'Histoire
Naturelle de la Suisse_; and this author of the _Tableaux de la Suisse_
has given a very distinct description of that appearance, which is
perhaps the more to be valued as a piece of natural history, as this
intelligent author does not pretend to any geological theory, but simply
narrates what he has seen, with such pertinent observations on
the subject as naturally must occur to a thinking person on the
spot.--(Discours, etc. page 228. Entrée au pays de Grisons).
"Du village d'Elen on continue à monter le reste du petit vallon pendant
une lieue et demie parmi les mêmes espèces de pierres qu'on vient de
décrire; en passant au travers de bois et de forêts de sapins et de
quelques pâturages dont ce haut est couvert, on parvient au pied du
Bundnerberg, montagne des grisons, qui forme la tête du vallon. On
laisse à droite un fond ou espèce d'entonnoir, entouré de très-hautes
montagnes inaccessibles, pour s'enfourrer à gauche entre des rochers qui
font fort resserrés, où coule un torrent. Ce lieu seroit horreur si
on ne se trouvoit accoutumé, par degrés, à voir de ces positions
effrayantes: tout y est aride, il n'y a plus d'arbres ni de végétaux ce
sont des rochers entassés les un sur les autres; ce lieu paroit d'autant
plus affreux que le passage a été subit, et qu'en sortant de bois et des
forêts, on se trouve tout-à-coup parmi ces rochers qui s'élèvent comme
des murailles, et dont on ne voit pas la cime; cette gorge ou cette
entrée qui se nomme Jetz, est la communication du Canton du Glaris aux
Gritons; on a dit précédemment qu'il y en avoit une plus aisée par
le Gros-Thal ou le grand vallon. Ce passage est très-curieux pour la
Lithogeognosie, il est rare de trouver autant de phénomènes intéressans
rassemblés, et des substances aussi variées par rapport à leurs
positions; c'est le local qui mérite le plus d'être examiné en Suisse,
et la plus difficile que nous ayons parcouru. On se souviendra que nous
avons continuellement monté depuis Glaris, et que nous nous trouvons au
pied de ces montagnes ou de ces pics étonnans qui dominent les hautes
Alpes; on trouve ici la facilité peu commune de pouvoir examiner, et
voir le pied ou les fondemens de ces colosses qui couronnent le globe,
parce qu'ils sont ordinairement entourés de leurs débris et de leurs
éboulemens qui en cachent le pied. Ici c'est une roche de schiste
bleuâtre, dure et compact, traversée de filons de quartz blanc, et
quelquefois jaunâtre, dans laquelle on a taillé un sentier pour pouvoir
en franchir le pied. Cette roche s'élève à une hauteur prodigieuse,
est presque verticale, et ces couches sont à quatre-vingt degrés
d'inclinaison. L'imagination est effrayée de voir que de pareilles
masses ayent pu être ébranlées et déplacées au point d'avoir fait
presque un quart de conversion. Après avoir monté et suivi cette roche
parmi les pierres et les décombres, une heure et demie, on trouve
cette roche de schiste surmontée d'autres rochers fort hauts qui sont
calcaires, et dont les lits sont fort horizontaux. Les schistes,
qui sont directement sous les roches calcaires, conservent la même
inclinaison qu'elles ont à leur pied."
Here is an observation which certainly agrees with that given by M. de
Luc, and would seem to confirm this conclusion, that strata had been
deposited upon those _schisti_ after they had been changed from their
natural or horizontal position, and become vertical; at the same time,
this conclusion is not of necessary consequence, without examining
concomitant appearances, and finding particular marks by which this
operation might be traced; for the simply finding horizontal strata,
placed above vertical or much inclined schiste, is not sufficient, of
itself, to constitute that fact, while it is acknowledged that every
species of fracture, dislocation, and contortion, is to be found among
the displaced strata of the globe.
Since writing this chapter, I am enabled to speak more decisively upon
that point, having acquired more light upon the subject, as will appear
in the next chapter.
CHAP. VI.
The Theory of interchanging Sea and Land illustrated by an
Investigation of the Primary and Secondary Strata.
SECT. I.--A distinct View of the Primary and Secondary Strata.
Having given a view of what seems to be the primary and secondary
strata, from the observations of authors, and having given what was
my opinion when I first wrote that chapter, I am now to treat of this
subject from observations of my own, which I made since forming that
opinion.
From Portpatrick, on the west coast, to St Abb's Head, on the east,
there is a tract of schistus mountains, in which the strata are
generally much inclined, or approaching to the vertical situation; and
it is in these inclined strata that geologists allege that there is not
to be found any vestige of organised body. This opinion, however, I have
now proved to be erroneous.
There cannot be any doubt with regard to the original formation of those
stratified bodies, as having been formed of the materials that are
natural to this earth, viz. the detritus of former bodies; and as having
been deposited in water, like the horizontal strata: For the substances
and bodies of which they are visibly composed are no other than those
which form the most regular horizontal strata, and which are continually
traveling, or transported at the bottom of the sea, such as gravel, and
sand, argillaceous and micaceous bodies.
On each side of this ridge of mountains, which towards the east end is
but narrow, there is a lower country composed of strata in general more
horizontal; and among which strata, besides coal, there are also found
the relics of organised bodies.
Abstracting at present from any consideration of organised bodies among
the materials of those strata, it may be affirmed, that the materials
which form the strata in the mountains and in the low country, are
similar, or of the same nature; that they have, in both places, been
consolidated by the same means, viz. heat and fusion; and that the same
or similar accidents have happened to them, such as change from their
original position, and mineral veins traversing them in various shapes.
Yet still there is a distinctive character for those two bodies, the
alpine and the horizontal strata; for, while the horizontal position
appears natural to the one, and the changes from that particular state
to be only an accident, the vertical position appears to be more natural
to the other, which is seldom found horizontal.
Therefore, altho' it is unquestionable that the strata in the alpine and
low countries had the same or a similar original, yet, as the vertical
position, which is the greatest possible change in that respect, is more
natural to the alpine strata, or only necessary in the natural order of
those bodies, we are to consider this great disorder or change from the
natural state of their original formation, as the proper character of
those alpine strata. But then it is also necessary to include in this
character a general hardness and solidity in those vertical strata,
otherwise they would not have been properly alpine, or have resisted the
wearing and washing powers of the globe, so as to have remained higher
than the others; for, the vertical position, or great inclination of
those strata, should rather have disposed them the more to dissolution
and decay. Let us now see how far we shall be justified in that general
conclusion, by the examination of those bodies.
The fact is certain, that those alpine bodies are much harder, or less
subject to dissolution and decay, than the horizontal strata. But this
must be taken in the general, and will by no means apply to particular
cases which might be compared. Nothing, for example, more solid than the
lime-stones, or marbles, and iron-stones; nothing more hard or solid
than the chirt or flint; and all these are found among the horizontal
strata. But, while some strata among those horizontal beds are
thus perfectly solid, others are found with so slight degrees of
consolidation, that we should not be able to ascribe it to the proper
cause, without that gradation of the effect, which leads us to impute
the slightest degree of consolidation to the same operations that have
produced the complete solidity. While, therefore, the most perfect
solidity is found in certain strata, or occasionally among the
horizontal bodies, this forms no part of their character in general, or
cannot be considered as a distinctive mark, as it truly is with
regard to the alpine strata. These last have a general character of
consolidation and indissolubility, which is in a manner universal. We
are, therefore, now to inquire into the cause of this distinction, and
to form some hypothesis that may be tried by the actual state of things,
in being compared with natural appearances.
As the general cause of consolidation among mineral bodies, formed
originally of loose materials, has been found to consist in certain
degrees of fusion or cementation of those materials by means of heat;
and as, in the examination of the horizontal strata we actually
find very different degrees of consolidation in the several strata,
independent of their positions in relation to height or depth, we have
reason to believe that the heat, or consolidating operation, has not
been equally employed in relation to them all.
We are not now inquiring how an inferior stratum should have been heated
in a lesser degree, or not consolidated, while a superior stratum had
been consolidated in the most perfect manner; we are to reason upon a
fact, which is, that the horizontal strata in general appear not to have
been equally or universally consolidated; and this we must attribute to
an insufficient exertion of the consolidating cause. But, so far as the
erecting cause is considered as the same with that by which the elevated
bodies were consolidated, and so far as the vertical situation is a
proof of the great exertion of that subterraneous power, the strata
which are most erected, should in general be found most consolidated.
Nothing more certain than that there have been several repeated
operations of the mineralising power exerted upon the strata
in particular places; and all those mineral operations tend to
consolidation: Therefore, the more the operations have been repeated in
any place, the more we should find the strata consolidated, or changed
from their natural state. Vertical strata have every appearance from
whence we should be led to conclude, that much of the mineral power
had been exerted upon them, in changing their original constitution or
appearance. But the question now to be considered is this, How far
it may appear that these masses of matter, which now seem to be so
different from the ordinary strata of the globe, had been twice
subjected to the mineral operations, in having been first consolidated
and erected into the place of land, and afterwards sunk below the
bottom of the sea, in order a second time to undergo the process of
subterraneous heat, and again be elevated into the place where they now
are found.
It must be evident, here is a question that may not be easy to decide.
It is not to the degree of any change to which bodies may be subject,
that we are to appeal, in order to clear up the point in question,
but to a regular course of operations, which must appear to have been
successively transacted, and by which the different circumstances or
situations of those masses are to be discovered in their present state.
Now, though it does not concern the present theory that this question be
decided, as it is nothing but a repetition of the same operations that
we look for; nevertheless, it would be an interesting fact in the
natural history of this earth; and it would add great lustre to a theory
by which so great, so many operations were to be explained. I am far
from being sanguine in my expectations of giving all the satisfaction
in relation to this subject that I could wish; but it will be proper to
state what I have lately learned with regard to so curious a question,
that others, who shall have the opportunity, may be led to inquire, and
that thus the natural history of the earth may be enlarged, by a proper
investigation of its mineral operations.
With this view I have often considered our schistus mountains, both in
the north and south; but I never found any satisfactory appearance from
whence conclusions could be formed, whether for the question or against
it. The places I examined were those between the alpine countries and
the horizontal strata; here, indeed, I have frequently found a confused
mass, formed of the fragments of those alpine strata mixed with the
materials of the horizontal bodies; but not having seen the proper shape
and connection of those several deposits, I always suspended my judgment
with regard to the particular operations which might have been employed
in producing those appearances.
I had long looked for the immediate junction of the secondary or low
country strata with the alpine schistus, without finding it; the first
place in which I observed it was at the north end of the island of
Arran, at the mouth of Loch Ranza; it was upon the shore, where the
inclined strata appeared bare, being; washed by the sea. It was but a
very small part that I could see; but what appeared was most distinct.
Here the schistus and the sandstone strata both rise inclined at an
angle of about 45°; but these primary and secondary strata were inclined
in almost opposite directions; and thus they met together like the
two sides of a _lambda_, or the rigging of a house, being a little in
disorder at the angle of their junction. From this situation of those
two different masses of strata, it is evidently impossible that either
of them could have been formed originally in that position; therefore, I
could not here learn in what state the schistus strata had been in when
those of the sand-stone, &c, had been superinduced.
Such was the state of my mind, in relation to that subject:, when at
Jedburgh upon a visit to a friend, after I had returned from Arran, and
wrote the history of that journey; I there considered myself as among
the horizontal strata which had first appeared after passing the Tweed,
and before arriving at the Tiviot. The strata there, as in Berwickshire,
which is their continuation to the east, are remarkably horizontal for
Scotland; and they consist of alternated beds of sand-stone and marl, or
argillaceous and micaceous strata. These horizontal strata are traversed
in places with small veins of whin-stone, as well as greater masses
forming rocks and hills of that material; but, except it be these, (of
which there are some curious examples), I thought there could be nothing
more of an interesting nature to observe. Chance, however, discovered to
me what I could not have expected or foreseen.
The river Tweed, below Melrose, discovers in its bed the vertical strata
of the schistus mountains, and though here these indurated bodies are
not veined with quartz as in many places of the mountains, I did not
hesitate to consider them as the same species, that is to say, the marly
materials indurated and consolidated in those operations by which they
had been so much changed in their place and natural position. Afterwards
in travelling south, and seeing the horizontal softer strata, I concluded
that I had got out of the alpine country, and supposed that no more of
the vertical strata were to be observed.
The river Tiviot has made a wide valley as might have been expected, in
running over thole horizontal strata of marly or decaying substances;
and the banks of this river declining gradually are covered with gravel
and soil, and show little of the solid strata of the country. This,
however, is not the case with the Jed, which is to the southward of the
Tiviot; that river, in many places, runs upon the horizontal strata, and
undermines steep banks, which falling shows high and beautiful sections
of the regular horizontal strata. The little rivulets also which fall
into the Jed have hollowed out deep gullies in the land, and show the
uniformity of the horizontal strata.
In this manner I was disposed to look for nothing more than what I had
seen among those mineral bodies, when one day, walking in the beautiful
valley above the town of Jedburgh, I was surprised with the appearance
of vertical strata in the bed of the river, where I was certain that
the banks were composed of horizontal strata. I was soon satisfied with
regard to this phenomenon, and rejoiced at my good fortune in stumbling
upon an object so interesting to the natural history of the earth, and
which I had been long looking for in vain.
Here the vertical strata, similar to those that are in the bed of
the Tweed, appear; and above those vertical strata, are placed the
horizontal beds, which extend along the whole country.
The question which we would wish to have solved is this; if the vertical
strata had been broken and erected under the superincumbent horizontal
strata; or if, after the vertical strata had been broken and erected,
the horizontal strata had been deposited upon the vertical strata,
then forming the bottom of the sea. That strata, which are regular and
horizontal in one place, should be found bended, broken, or disordered
at another, is not uncommon; it is always found more or less in all our
horizontal strata. Now, to what length this disordering operation might
have been carried, among strata under others, without disturbing the
order and continuity of those above, may perhaps be difficult to
determine; but here, in this present case, is the greatest disturbance
of the under strata, and a very great regularity among those above. Here
at least is the most difficult case of this kind to conceive, if we are
to suppose that the upper strata had been deposited before those below
had been broken and erected.
Let us now suppose that the under strata had been disordered at the
bottom of the sea, before the superincumbent bodies were deposited; it
is not to be well conceived, that the vertical strata should in that
case appear to be cut off abruptly, and present their regular edges
immediately under the uniformly deposited substances above. But, in the
case now under consideration, there appears the most uniform section
of the vertical strata, their ends go up regularly to the horizontal
deposited bodies. Now, in whatever state the vertical strata had been in
at the time of this event, we can hardly suppose that they could have
been so perfectly cut off, without any relict being left to trace that
operation. It is much more probable to suppose, that the sea had washed
away the relics of the broken and disordered strata, before those that
are now superincumbent had been begun to be deposited. But we cannot
suppose two such contrary operations in the same place, as that of
carrying away the relics of those broken strata, and the depositing of
sand and subtile earth in such a regular order. We are therefore led
to conclude, that the bottom of the sea, or surface of those erected
strata, had been in very different situations at those two periods, when
the relics of the disordered strata had been carried away, and when the
new materials had been deposited.
If this shall be admitted as a just view of the subject, it will be fair
to suppose, that the disordered strata had been raised more or less
above the surface of the ocean; that, by the effects of either rivers,
winds, or tides, the surface of the vertical strata had been washed
bare; and that this surface had been afterwards sunk below the influence
of those destructive operations, and thus placed in a situation proper
for the opposite effect, the accumulation of matter prepared and put in
motion by the destroying causes.
I will not pretend to say that this has all the evidence that should be
required, in order to constitute a physical truth, or principle from
whence we were to reason farther in our theory; but, as a simple fact,
there is more probability for the thing having happened in that manner
than in any other; and perhaps this is all that may be attained, though
not all that were to be wished on the occasion. Let us now see how
far any confirmation may be obtained from the examination of all the
attending circumstances in those operations.
I have already mentioned, that I had long observed great masses of
_debris_, or an extremely coarse species of pudding-stone, situated on
the south as well as north sides of those schistus mountains, where the
alpine strata terminate in our view, and where I had been looking for
the connection of those with the softer strata of the low country.
It has surely been such appearances as these which have often led
naturalists to see the formation of secondary and tertiary strata formed
by the simple congestion of _debris_ from the mountains, and to suppose
those masses consolidated by the operation of that very element by which
they had been torn off from one place and deposited in another. I never
before had data from whence to reason with regard to the natural history
of those masses of gravel and sand which always appeared to me in an
irregular shape, and not attended with such circumstances as might give
light into their natural history; but now I have found what I think
sufficient to explain those obscure appearances, and which at the same
time will in some respect illustrate or confirm the conjecture which
has now been formed with regard to the operations of the globe in those
regions.
In describing the vertical and horizontal strata of the Jed, no mention
has been made of a certain pudding-stone, which is interposed between
the two, lying immediately upon the one and under the other. This
puddingstone corresponds entirely to that which I had found along
the skirt of the schistus mountains upon the south side, in different
places, almost from one end to the other. It is a confused mass of
stones, gravel, and sand, with red marly earth; these are consolidated
or cemented in a considerable degree, and thus form a stratum extremely
unlike any thing which is to be found either above or below.
When we examine the stones and gravel of which it is composed, these
appear to have belonged to the vertical strata or schistus mountains.
They are in general the hard and solid parts of those indurated
strata, worn and rounded by attrition; particularly sand or marl-stone
consolidated and veined with quartz, and many fragments of quartz, all
rounded by attrition. In this pudding-stone of the Jed, I find also
rounded lumps of porphyry, but have not perceived any of granite.[32]
This however is not the case in the pudding-stone of the schistus
mountains, for, where there is granite in the neighbourhood, there is
also granite in the pudding-stone.
[Note 32: A view of this object is seen in plate 3d. It is from a
drawing taken by Mr Clerk of Eldin.]
From this it will appear, that the schistus mountains or the vertical
strata of indurated bodies had been formed, and had been wasted and worn
in the natural operations of the globe, before the horizontal strata
were begun to be deposited in those places; the gravel formed of those
indurated broken bodies worn round by attrition evince that fact. But
it also appears that the mineral operations of the globe, melting and
consolidating bodies, had been exerted upon those deposited strata above
the vertical bodies.
This appears evidently from the examination of our pudding-stone. The
vertical strata under it are much broken and injected with ferruginous
spar; and this same spar has greatly penetrated the pudding-stone above,
in which are found the various mineral appearances of that spar and iron
ore.
But those injecting operations reach no farther up among the marl strata
in this place; and then would appear to have been confined to the
pudding-stone. But in another place, about half a mile farther up the
river, where a very deep section of the strata is discovered, there
are two injections from below; the one is a thin vein of whin-stone or
basaltes, full of round particles of steatites impregnated with copper;
it is but a few inches wide, and proceeds in a kind of zigzag. The other
appears to have been calcareous spar, but the greatest part of it is now
dissolved out. The strata here descend to the bottom of the river, which
is above the place of the pudding-stone and vertical strata. Neither are
these last discoverable below the town of Jedburgh, at least so far as
I have seen; and the line of division, or plane of junction of the
vertical and horizontal strata, appears to decline more than the bed of
the river.
But it may be asked, how the horizontal strata above, among which are
many very strong beds, have been consolidated. The answer to this
question is plain. Those strata have been indurated or consolidated
in no other manner than the general strata of the earth; these being
actually the common strata of the globe; while the vertical or schistus
strata are the ordinary strata still farther manufactured, (if we may be
allowed the expression) in the vicissitude of things, and by the mineral
operations of the globe. That those operations have been performed by
subterraneous heat has been already proved; but I would now mention some
particular appearances which are common or general to those strata, and
which can only be explained upon that principle.
The red marly earth is prevalent among those strata; and it is with this
red ferruginous substance that many of the sand-stone strata are tinged.
It is plain that there had been an uniform, deposits of that sand and
tinging earth; and that, however different matter might be successively
deposited, yet that each individual stratum should be nearly of the same
colour or appearance, so far as it had been formed uniformly of the same
subsiding matter. But, in the most uniform strata of red sand-stone,
the fracture of the stone presents us with circular spots of a white or
bluish colour; those little spheres are in all respects the same with
the rest of the stone, they only want the tinging matter; and now it may
be inquired how this has come about.
To say that sphericles of white sand should have been formed by
subsiding along with the red sand and earth which composed the uniform
stratum whether of sand-stone or marl, (for it happens equally in both,)
is plainly impossible, according to our notion of that operation in
which there is nothing mysterious. Those foliated strata, which are of
the most uniform nature, must have been gradually accumulated from the
subsiding sand and earth; and the white or colourless places must have
had their colour destroyed in the subsequent cementing operations. It
is often apparent, that the discharging operation had proceeded from a
centre, as some small matter may be perceived in that place. I know not
what species of substance this has been, whether saline or phlogistic,
but it must have had the power of either volatilising or changing the
ferruginous or red tinging substance so as to make it lose its colour.
I have only mentioned spherical spots for distinctness sake; but this
discharging operation is found diversifying those strata in various
ways, but always referable to the same or similar causes. Thus, in many
of the veins or natural cracks of those strata, we find the colour
discharged for a certain space within the strata; and we often see
several of those spots united, each of them having proceeded from its
own centre, and uniting where they approached. In the two veins above
mentioned, of whin-stone and spar traversing the strata, the colour of
the strata is, discharged more or less in the places contiguous with the
veins.
I am now to mention another appearance of a different kind. Those strata
of marl are in general not much consolidated; but among, them there
are sometimes found thin calcareous strata extremely consolidated,
consequently much divided by veins. It is in the solid parts of those
strata, perfectly disconnected from the veins, that there are frequent
cavities curiously lined with crystals of different sorts, generally
calcareous, sometimes containing also those that are siliceous, and
often accompanied with pyrites. I am persuaded that the origin of those
cavities may have been some hollow shells, such as _echini_ or some
marine object; but that calcareous body has been so changed, that it is
not now distinguishable; therefore, at present, I hold this opinion only
as conjecture.
Having, in my return to Edinburgh, traveled up the Tiviot, with a view
to investigate this subject of primary and secondary operations of the
earth, I found the vertical strata, or alpine schistus, in the bed of
the river about two miles below Hawick. This was the third time I had
seen those vertical bodies after leaving the mountains of Lauderdale.
The first place was the bed of the river Tweed, at the new bridge below
Melrose; but here no other covering is to be seen above those vertical
strata besides the soil or traveled earth which conceals every thing
except the rock in the bed of the river. The second place was Jedburgh,
where I found the vertical strata covered with the horizontal sandstone
and marl, as has been now described. The third place was the Tiviot, and
this is that which now remains to be considered.
Seeing the vertical strata in the bed of the river, I was desirous to
know if those were immediately covered with the horizontal strata. This
could not be discovered in the bed of the river where the rock was
covered upon the banks with travelled earth. I therefore left the river,
and followed the course of a brook which comes from the south side. I
had not gone far up the bank, or former boundary of the Tiviot, when
I had the satisfaction to find the vertical strata covered with the
pudding-stone and marly beds as in the valley of the Jed.
It will now be reasonable to suppose that all the schistus which we
perceive, whether in the mountains or in the valleys, exposed to our
view had been once covered with those horizontal strata which are
observed in Berwickshire and Tiviotdale; and that, below all those
horizontal strata in the level country, there is at present a body or
basis of vertical or inclined schistus, on which the horizontal strata
of a secondary order had been deposited. This is the conclusion that I
had formed at Jedburgh, before I had seen the confirmation of it in the
Tiviot; it is the only one that can be formed according to this view of
things; and it must remain in the present state until more evidence be
found by which the probability may be either increased or diminished.
Since writing this, I have read, in the Esprit de Journaux, an abstract
of a memoir of M. Voigt, upon the same subject, which I shall now
transcribe.
"La mer a commencé par miner les montagnes primitives dont les débris se
sont précipités au fond. Ces débris forment la premiere couche qui est
posée immédiatement sur les montagnes primitives. D'après l'ancien
langage de mineurs, nous avons jusqu'aujourd'hui appellé cette couche
_le sol mort rouge_, parce qu'il y a beaucoup de rouge dans son mélange,
qu'elle forme le sol ou la base d'autres couches, et peut-être de
toutes, qu'elle est entierement inutile et, en quelque facon, morte pour
l'exploitation des mines. Plusieurs se sont efforcés de lui donner un
nom harmonieux; mais ils ne l'ont pu sans occasionner des équivoques.
Les mots _Brèche Puddinstone Conglomérations_, &_c_. désignent toujours
des substances autres que cette espèce de pierre.
"Il est très agréable de l'examiner dans les endroits où elle forme des
montagnes entières. Cette couche est composée d'une quantité prodigieuse
de pierres arrondies, agglutinées ensemble par une substance argileuse
rouge et même grise, et le toute a acquis assez de dureté. On ne trouve
dans sa composition aucune espèce de pierre qui, à en juger par les
meilleures observations, puisse avoir été formée plus tard qu'elle;
on n'y voit par-tout que des parties et des produit des montagnes
primitives principalement de celles qui abondent le plus dans ces
contrées. Le sol mort, par exemple, qui compose les montagnes des
environs de Walbourg, près d'Eisenach, contient une quantité de gros
morceaux de granit et de schiste micacé; c'est vraisemblablement parce
que les montagnes primitives les plus voisines de Rhula, etc. sont,
pour la plus part, formées de ces deux espèces de pierres. Près de
Goldlauter, le sol mort consiste presque tout en porphyre, substance
dont sont formées les montagnes primitives qui y dominent; et le
Kiffauserberg dans la Thuringe a probablement reçu ces morceaux arrondis
de schiste argileux des montagnes voisine du Hartz. Vous trouverez
ici que le schiste argileux existoit déjà lorsque la mer a jetté les
premiers fondemens de nos montagnes stratifiées. Je serois fort étonné
que quelqu'un me montrât un sol mort qui contînt un morceaux de gypse,
de marne, de pierre puante et autres. Quoiqu'il en soit il n'est pas
aisé d'expliquer pourquoi on ne trouve point de corps marins pétrifiés
dans cette espèce de pierre. C'est peut-être que, par l'immense quantité
de pierres dures roulées dans le fond de la mer, ils ont été brisés
avant qu'ils aient commencé de s'agglutiner ensemble. Mais on rencontre
sur-tout au Kiffhauserberg des troncs d'arbres entiers pétrifiés; preuve
qu'il y avoit déjà ou de la végétation avant que l'océan destructeur se
fût emparé de ces cantons, ou du moins que quelques isles avoient existé
au-dessus de la surface."
Here we find the same observations in the mountains of Germany that
I have been making with regard to those of Scotland. I have formerly
observed masses of the same kind in the west of England, to the east of
the Severn; but I could not discover any proper connection of that mass
with the regular strata. I have also long observed it in many parts of
Scotland, without being able to attain a sufficiently satisfactory idea
with regard to those particulars by which the alternation of land and
water, of the superficial and internal mineral operations of the globe,
might be investigated.
It will be very remarkable if similar appearances are always found upon
the junction of the alpine with the level countries. Such an appearance,
I am inclined to think, may be found in the Val d'Aoste, near Yvrée. M.
de Saussure describes such a stone as having been employed in building
the triumphal arch erected in honour of Augustus. "Cet arc qui étoit
anciennement revêtu de marbre, est construit de grands quartiers d'une
espèce assez singulière de poudingue ou de grès à gros grains. C'est une
assemblage de fragmens, presque touts angulaires, de toutes sortes de
roches primitives feuilletées, quartzeuses, micacées; les plus gros de
ces fragmens n'atteignent pas le volume, d'une noisette. La plupart des
édifices antiques de la cité l'Aoste et de ses environs, sont construits
de cette matière; et les gens du pays sont persuadés que c'est une
composition; mais j'en ai trouvé des rochers en place dans les montagnes
au nord et au-dessus de la route d'Yvrée."
We may now come to this general conclusion, that, in this example of
horizontal and posterior strata placed upon the vertical _schisti_ which
are prior in relation to the former, we obtain a further view into the
natural history of this earth, more than what appears in the simple
succession of one stratum above another. We know, in general, that all
the solid parts of this earth, which come to our view, have either
been formed originally by subsidence at the bottom of the sea, or been
transfused in a melted state from the mineral regions among those solid
bodies; but here we further learn, that the indurated and erected
strata, after being broken and washed by the moving waters, had again
been sunk below the sea, and had served as a bottom or basis on which to
form a new structure of strata; and also, that those new or posterior
strata had been indurated or cemented by the consolidating operations
of the mineral region, and elevated from the bottom of the sea into the
place of land, or considerably above the general surface of the waters.
It is thus that we may investigate particular operations in the general
progress of nature, which has for object to renovate the surface of the
earth necessarily wasted in the operation of a world sustaining plants
and animals.
It is necessary to compare together every thing of this kind which
occurs; it is first necessary to ascertain the fact of their being a
prior and posterior formation of strata, with the mineral operations
for consolidating those bodies formed by collection of the moveable
materials; and, secondly, it is interesting to acquire all the data we
can in order to form a distinct judgment of that progress of nature in
which the solid body of our land is alternately removed from the bottom
of the sea into the atmosphere, and sunk again at the bottom of the sea.
I shall now transcribe what M. Schreiber has wrote in relation to
this subject. It is in a memoir concerning the gold mine of Gardette,
published in the Journal de Physique.
"Avant de quitter la montagne de la Gardette qu'il me soit permis de
rapporter une observation qui peut-être n'est pas dénuée de tout
intérêt pour les naturalistes; je l'ai faite dans une galerie à environ
cinquante-trois toises à l'ouest du principal puit laquelle a été
poussée sur la ligne de réunion de la pierre calcaire, et du granit
feuilleté ou gneiss pour fonder le filon dans cet endroit. Ce filon
a six pouces d'épaisseur, et consiste en quartz entre-mêlé d'ochre
martiale, de pyrite cuivreuse et galène. Cette dernière est souvent
recouverte de chaux de plomb grise, et de petits cristaux de mine de
plomb jaune donnant dans l'analyse un indice d'or. Ce filon finit à la
réunion de la pierre calcaire au gneiss. Cette réunion se fait ici dans
la direction d'une heure 6/8 de la boussole de raineur, et sous un
inclinaison, occidentale de 26 degrés.
"Mais ce qu'il y a de remarquable, c'est que le gneis ne participe en
rien de la pierre calcaire quoiqu'il n'en soit séparé que par une couche
d'une pouce d'épaisseur de terre argileuse et calcaire, tandis que le
rocher calcaire renferme beaucoup de fragmens de granit et de gneis,
dans le voisinage de cette réunion.
"Cette observation prouve incontestablement que le granit et le gneis
avoient déjà acquis une dureté capable de résister aux infiltration
des parties calcaire, et qu'ils existoient à-peu-près tels qu'ils sont
aujourd'hui lorsque la pierre calcaire commença à se former; autrement
elle n'auroit pu saisir et envelopper des morceaux détachés de ces
rochers auxquels on donne avec raison l'épithète de primitif ou de
première formation."
M. Schreiber continues his reasoning upon those mineral appearances, in
adducing another argument, which I do not think equally conclusive. He
says, "Le filon de la Gardette devoit pareillement exister avant la
montagne calcaire, car s'il s'étoit formé apres, je ne voit pas la
raison pour laquelle il s'y seroit arrêté court, et pourquoi il ne se
seroit pas prolongé dans cette espèce de rocher." It is not necessary,
in the formation of a vein, that it should proceed in traversing all the
strata which then are superincumbent; it is reasonable to suppose, and
consistent with observation to find them stop short in proceeding from
one stratum to another. Had M. Schreiber found any pieces of the vein
contained in the calcareous rock, he would have had good reason for
that assertion; but, to conclude that fact from grounds which do not
necessarily imply it, is not to be permitted in sound reasoning, if
certainty is the object, and not mere probability.
SECT. II.--The Theory confirmed from Observations made on purpose to
elucidate the subject.
Having got a distinct view of the primary and secondary mineral bodies
or strata of the globe, and having thus acquired a particular object to
inquire after, with a view to investigate or illustrate this piece of
natural history, I was considering where we might most probably succeed
in finding the junction of the low country strata and alpine schistus.
I inquired of Mr Hall of Whitehall, who had frequent opportunities of
traversing those mountains which lie between his house in the Merse and
Edinburgh; and I particularly entreated him to examine the bed of the
Whittater, which he executed to my satisfaction.
Mr Hall having had occasion to examine the Pease and Tour burns, in
planning and superintending the great improvement of the post road upon
Sir James Hall's estate while Sir James was abroad, he informed me that
the junction of the schistus and sand-stone strata was to be found in
the Tour burn. Professor Playfair and I had been intending a visit to
Sir James Hall at Dunglass; and this was a motive, not so much to hasten
our visit, as to chose the most proper time for a mineral expedition
both upon the hills and along the sea shore.
It was late in the spring 1788 when Sir James left town, and Mr Playfair
and I went to Dunglass about the beginning of June. We had exceeding
favourable weather during the most part of our expedition; and I now
propose to give an account of the result of our observations.
Dunglass burn is the boundary between the counties of East Lothian and
Berwickshire; and it is almost the boundary between the vertical and
horizontal strata. To the north-west of this burn and beautiful dean are
situated the coal, lime-stone, marl, and sand-stone strata; they are
found stretching away along the shore in a very horizontal direction
for some time, but become more and more inclined as they approach the
schistus of which the hills of Lammermuir to the south are composed.
Though the boundary between the two things here in question be easily
perceivable from the nature of the country at the first inspection, by
the rising of the hills, yet this does not lead one precisely to the
junction; and in the extensive common boundary of those two things, the
junction itself is only to be perceived in few places, where the rock is
washed bare by the rivers or the sea, and where this junction is exposed
naked to our view. The sea is here wearing away the coast; and the bank,
about 200 feet high, is gradually falling down, making in some places a
steep declivity, in others a perpendicular cliff. St Abb's Head and Fast
Castle are head lands projecting into the sea, and are the bulwarks of
this shore, which is embayed to the westward, where the sea preys upon
the horizontal strata. The solid strata are every where exposed either
in the cliff or on the shore; we were therefore certain of meeting with
the junction in going from Dunglass to Fast Castle, which is upon the
schistus. But this journey can only be made by sea; and we first set out
to examine the junction in the Tour and Pease burns, where we had been
informed it was to be found.
In the bottom of those rivulets the sand-stone and marly strata appear
pretty much inclined, rising towards the schistus country. The two burns
unite before they come to the shore; and it is about midway between this
junction and the bridges which are thrown over those two hollows, that
the junction is to be found.
The schistus strata here approach towards vertical; and the sand-stone
strata are greatly inclined. But this inclination of those two different
strata are in opposite directions; neither does the horizontal section
of those two different strata run parallel to the junction; that is to
say, the intersection of those two different strata is a line inclined
to the horizon.
At Jedburgh the schistus was vertical, and the strata horizontal; and
there was interposed a compound bed of pudding-stone, formed of various
water-worn bodies, the gravel of the schistus strata, and porphyries.
Here again, though we have not a regular pudding-stone, we have
that which corresponds to it, as having been the effect of similar
circumstances. These are the fracture and detritus of the schistus,
while the strata were deposited upon the broken ends of the schistus at
the bottom of the sea. Most of the fragments of the schistus have their
angles sharp; consequently, they had not travelled far, or been much
worn by attrition. But more or less does not alter the nature of an
operation; and the pudding-stone, which at Jedburgh is interposed
between the vertical schistus and horizontal strata, is here properly
represented by the included fragments of schistus in the inclined
strata.
The line of this junction running, on the one hand, towards Fast Castle
eastward, and, on the other, towards the head of Dunglass burn
westward, our business was to pursue this object in those two different
directions. But it was chiefly in the sea coast that was placed our
expectations, having recollection of the great banks of gravel under
which the strata are buried about Oldhamstocks, near which, from all
appearances, the junction was to be expected.
Having taken boat at Dunglass burn, we set out to explore the coast;
and, we observed the horizontal sand-stone turn up near the Pease burn,
lifting towards the schistus. We found the junction of that schistus
with the red sand-stone and marly strata on the shore and sea bank, at
St. Helens, corresponding in general with what we had observed in the
burns to the westward. But, at Siccar Point, we found a beautiful
picture of this junction washed bare by the sea. The sand-stone strata
are partly washed away, and partly remaining upon the ends of the
vertical schistus; and, in many places, points of the schistus strata
are seen standing up through among the sand-stone, the greatest part of
which is worn away. Behind this again we have a natural section of those
sand-stone strata, containing fragments of the schistus.
After this nothing appears but the schistus rocks, until sand-stone and
marl again are found at Red-heugh above the vertical strata. From that
bay to Fast Castle we had nothing to observe but the schistus, which is
continued without interruption to St Abb's Head. Beyond this, indeed,
there appears to be something above the schistus; and great blocks of a
red whin-stone or basaltes come down from the height and lie upon the
shore; but we could not perceive distinctly how the upper mass is
connected with the vertical schistus which is continued below.
Our attention was now directed to what we could observe with respect
to the schisti, of which we had most beautiful views and most perfect
sections. Here are two objects to be held in view, in making those
observations; the original formation or stratification of the schisti,
and the posterior operations by which the present state of things has
been procured. We had remarkable examples for the illustration of both
those subjects.
With regard to the first, we have every where among the rocks many
surfaces of the erected strata laid bare, in being separated. Here we
found the most distinct marks of strata of sand modified by moving
water. It is no other than that which we every day observe upon the
sands of our own shore, when the sea has ebbed and left them in a waved
figure, which cannot be mistaken. Such figures as these are extremely
common in our sand-stone strata; but this is an object which I never had
distinctly observed in the alpine schisti; although, considering that
the original of those schisti was strata of sand, and formed in water,
there was no reason to doubt of such a thing being found. But here the
examples are so many and so distinct, that it could not fail to give us
great satisfaction.
We were no less gratified in our views with respect to the other object,
the mineral operations by which soft strata, regularly formed in
horizontal planes at the bottom of the sea, had been hardened and
displaced. Fig. 4. represents one of those examples; it was drawn by Sir
James Hall from a perfect section in the perpendicular cliff at Lumesden
burn. Here is not only a fine example of the bendings of the strata, but
also of a horizontal shift or hitch of those erected strata.
St Abb's Head is a promontory which, at a distance, one would naturally
conclude to be composed of the schisti, as is all the shore to that
place; but, as we approached it, there was some difference to be
perceived in the external appearance, it having a more rounded and
irregular aspect. Accordingly, upon our arrival, we found this head-land
composed of a different substance. It is a great mass of red whin-stone,
of a very irregular structure and composition. Some of it is full of
small pebbles of calcareous spar, surrounded with a coat of a coloured
substance, different both from the whin-stone ground and the inclosed
pebble. Here ended our expedition by water.
Having thus found the junction of the sand-stone with the schistus
or alpine strata to run in a line directed from Fast Castle to
Oldhamstocks, or the heads of Dunglass burn, we set out to trace this
burn, not only with a view to observe the junction, if it should there
appear, but particularly to discover the source of many blocks of
whin-stone, of all sizes, with which the bed of this burn abounds.
The sand-stone and coal strata, which are nearly horizontal at the mouth
of this burn, or on the coast, become inclined as we go up the course of
the rivulet; and of this we have fine sections in the bank. The Dean of
Dunglass is formed of precipitous and perpendicular rocks, through which
the running water has worn its way more than a hundred feet deep; above
this Dean the banks are steep and very high, but covered with
soil, which here is a deep gravel. The burn runs all the way up to
Oldhamstocks upon the sand-stone strata; but there, these are traversed
by a high whin-stone dyke, which crosses the burn obliquely, as we found
it on both banks though not in the bed of the burn; it is in the south
bank below the village, and on the north above it. Here is the source
of the whin-stone which we were looking for; it is the common blue
basaltes, of the same nature with the Giant's Causeway, but with no
regular columner appearance.
Above Oldhamstocks we again found the sand-stone in the bank, but it
soon disappeared under a deep cover of gravel, and the burn then divided
into several rivulets which come from the hills. We traced the one which
led most directly up to the mountains, in expectation of meeting with
the schistus, at least, if not the junction of it with the sandstone.
But in this we were disappointed. We did not however lose our labour;
for, though the junction which we pursued be not here visible, we met
with what made it sufficiently evident, and was at the same time an
object far more interesting in our eyes.
I have already quoted Mr Voigt's description of the _sol mort rouge_; he
says, that in places it forms entire mountains; here we have a perfect
example of the same thing; and the moment we saw it, we said, here is
the _sol mort rouge_. We ascended to the top of the mountain through
a gully of solid pudding-stone going into decay, and furnishing the
country below with that great covering of gravel, soil, and water worn
stones. We were now well acquainted with the pudding-stone, which is
interposed between the horizontal and alpine strata; but from what we
had seen to the eastward, we never should have dreamed of meeting with
what we now perceived. What we had hitherto seen of this pudding-stone
was but a few fragments of the schistus in the lower beds of sand-stone;
here a mountain of water-worn schisti, imbedded in a red earth and
consolidated, presented itself to our view. It was evident that the
schisti mountains, from whence those fragments had come, had been prior
to this secondary mass; but here is a secondary mountain equal in height
to the primary, or schisti mountains, at the basis of which we had seen
the strata superinduced on the shore. Still, however, every thing here
is formed upon the same principle, and nothing here is altered except
the scale on which the operation had been performed.
Upon the coast, we have but a specimen of the pudding-stone; most of
the fragments had their angles entire; and few of them are rounded by
attrition. Here, on the contrary, the mountain is one pudding-stone;
and most of the fragments are stones much rounded by attrition. But the
difference is only in degree, and not in kind; the stones are the same,
and the nature of the composition similar. Had we seen the mass of which
this mountain is only a relict, (having been degraded by the hands of
time), we should have found this pudding-stone at the bottom of
our sand-stone strata; could we have penetrated below this mass of
pudding-stone, we should have found our schistus which we left on the
shore at St. Helens and in the Tour burn. In Tiviotdale the vertical
schisti are covered with a bed of pudding-stone, the gravel of which had
been much worn by attrition, but the thickness of that bed is small;
here again the wearing operation has been great, and the quantity of
those materials even more than in proportion to those operations. We
returned perfectly satisfied; and Sir James Hall is to pursue this
subject farther when he shall be in those mountains shooting muir game.
We had now only one object more to pursue; this was to examine the south
side of those mountains of Lammermuir upon the sea shore, in order
to see the junction of the primary schistus with the coal strata
of Berwickshire. Mr Hall was to meet us at the Press, and we were
afterwards to go with him to Whitehall. We met accordingly; but the
weather was rainy; and we went directly to Whitehall. I had often seen
the pudding-stone in great masse; in the banks of the Whiteader, as
it comes out of the mountains, but then I had not seen its connection
neither, on the one hand, with the schisti, nor, on the other, with the
sand-stone strata. We knew that at Lammerton upon the sea coast there
was coal, and consequently the sand-stone strata; and reasoning upon
those data we were sure that our proper course of investigation was to
trace the river Ey to the shore, and then go south the coast in search
of the junction of the schistus with the horizontal strata. This we
executed as well as the weather would permit; but had it to regret,
that the rainy season was not so favourable for our views, as it was
agreeable to the country which had been suffering with the drought.
It is needless now to enlarge upon this subject. I shall only mention
that we found the red marly strata above the pudding-stone in the bed of
the Ey and its branches; we then traced the schistus down the Ey, and
found a mass of the most consolidated pudding-stone upon the coast to
the north of the harbour of Eymouth. But this mass did not rest on the
schistus; it is immediately upon a mass of whin-stone; and the schistus
is in the harbour, so that this whin-stone mass seems to be here
interposed between the pudding-stone and schistus. We then pursued
the coast southwards until we found the junction of the schistus and
sand-stone strata about two miles from Eymouth; but here the junction
was not attended with any pudding-stone that we could perceive.
Having found the same or similar appearances from the one end to the
other, and on both sides of that range of mountains which run from sea
to sea in the south of Scotland, we may now extend our view of this
mineral operation in comprehending every thing of the same kind which we
meet with in our island or any other distant country.
Thus perhaps the pudding-stone of the south of England will be
considered in the same light as having been formed of the _débri_ and
_détritus_ of the flinty bodies.
In the island of Arran, there is also a pudding-stone, even in some
of the summits of the island, exactly upon the border of the schistus
district, as will be described in the natural history of that island.
This pudding-stone is composed of gravel formed of the hardest parts
of the schistus and granite or porphyry mountains. That compound
parasitical stone has been also again cemented by heat and fusion; I
have a specimen in which there is a clear demonstration of that fact.
One of the water-worn stones which had been rounded by attrition, has in
this pudding-stone been broken and shifted, the one half slipping over
the other, three quarters of an inch, besides other smaller slips in
the same stone. But the two pieces are again cemented; or they had been
shifted when the stone was in that soft state, by which the two pieces
are made perfectly to cohere. Those shifts and veins, in this species of
stone, are extremely instructive, illustrating the mineral operations of
the globe.
In like manner to the north of the Grampians, along the south side of
Loch Ness, there are mountains formed of the debris of schistus and
granite mountains, first manufactured into sand and gravel, and then
consolidated into a pudding-stone, which is always formed upon the same
principle. The same is also found upon the south side of those mountains
in the shire of Angus.
I may also give for example the African _Brechia_, which is a
pudding-stone of the same nature. This stone is composed of granites or
porphyries, serpentines and schisti, extremely indurated and perfectly
consolidated. It is also demonstrable from the appearance in this stone
that it has been in a softened state, from the shape and application
of its constituent parts; and in a specimen of it which I have in my
cabinet, there is also a demonstration of calcareous spar flowing among
the gravel of the consolidated rock.
This fact therefore of pudding-stone mountains, is a general fact, so
far as it is founded upon observations that are made in Africa, Germany,
and Britain. We may now reason upon this general fact, in order to see
how far it countenances the idea of primitive mountains, on the one
hand, or on the other supports the present theory, which admits of
nothing primitive in the visible or examinable parts of the earth.
To a person who examines accurately the composition of our mountains,
which occupy the south of Scotland, no argument needs be used to
persuade him that the bodies in question are not primitive; the thing
is evident from inspection, as much as would be the ruins of an ancient
city, although there were no record of its history. The visible
materials, which compose for the most part the strata of our south
alpine schisti, are so distinctly the _debris_ and _detritus_ of a
former earth, and so similar in their nature with those which for the
most part compose the strata on all hands acknowledged as secondary,
that there can remain no question upon that head. The consolidation,
again, of those strata, and the erection of them from their original
position, and from the place in which they had been formed, is another
question.
But the acknowledging strata, which had been formed in the sea of loose
materials, to be consolidated and raised into the place of land, is
plainly giving up the idea of primitive mountains. The only question,
therefore, which remains to be solved, must respect the order of things,
in comparing the alpine schisti with the secondary strata; and this
indeed forms a curious subject of investigation.
It is plain that the schisti had been indurated, elevated, broken, and
worn by attrition in water, before the secondary strata, which form the
most fertile parts of our earth, had existed. It is also certain that
the tops of our schistus mountains had been in the bottom of the sea
at the time when our secondary strata had begun to be formed; for the
pudding-stone on the top of our Lammermuir mountains, as well as the
secondary strata upon the vertical schisti of the Alps and German
mountains, affords the most irrefragable evidence of that fact.
It is further to be affirmed, that this whole mass of water-formed
materials, as well as the basis on which it rested, had been subjected
to the mineral operations of the globe, operations by which the loose
and incoherent materials are consolidated, and that which was the bottom
of the sea made to occupy the station of land, and serve the purpose for
which it is destined in the world. This also will appear evident, when
it is considered that it has been from the appearances in this very
land, independent of those of the alpine schisti, that the present
theory has been established.
By thus admitting a primary and secondary in the formation of our land,
the present theory will be confirmed in all its parts. For, nothing but
those vicissitudes, in which the old is worn and destroyed, and new
land formed to supply its place, can explain that order which is to be
perceived in all the works of nature; or give us any satisfactory
idea with regard to that apparent disorder and confusion, which would
disgrace an agent possessed of wisdom and working with design.
CHAP. VII.
Opinions examined with regard to Petrifaction, or Mineral Concretion.
The ideas of naturalists with regard to petrifaction are so vague and
indistinct, that no proper answer can be given to them. They in general
suppose water to be the solvent of bodies, and the vehicle of petrifying
substances; but they neither say whether water be an universal
menstruum, nor do they show in what manner a solid body has been formed
in the bowels of the earth, from that solution. It may now be proper to
examine this subject, not with a view to explain all those petrifactions
of bodies which is performed in the mineral regions of the earth, those
regions that are inaccessible to man, but to show that what has been
wrote by naturalists, upon this subject, has only a tendency to corrupt
science, by admitting the grossest supposition in place of just
principle or truth, and to darken natural history by introducing an ill
conceived theory in place of matter of fact.
M. le Comte de Buffon has attempted to explain the crystallization
of bodies, or production of mineral forms, by the accretion or
juxtaposition of elementary bodies, which have only form in two
dimensions, length and breadth; that is to say, that mineral concretions
are composed of surfaces alone, and not of bodies. This however is only
an attempt to explain, what we do not understand, by a proposition which
is either evidently contradictory, or plainly inconceivable. It is
true that this eloquent and ingenious author endeavours to correct the
palpable absurdity of the proposition, by representing the constituent
parts of the mineral bodies as "_de lames infiniment minces_;" but who
is it does not see, that these infinitely thin plates are no other than
bodies of three dimensions, contrary to the supposition; for, infinitely
thin, means a certain thickness; but the smallest possible or assignable
thickness differs as much from a perfect superficies as the greatest.
M. de Luc has given us his ideas of petrifaction with sufficient
precision of term and clearness of expression; his opinion, therefore,
deserves to be examined; and, as his theory of petrifaction is equally
applicable to every species of substance, it is necessary again to
examine this subject, notwithstanding of what has been already said,
in the first part of this work, concerning consolidation and mineral
concretion from the fluid state of fusion.
This author has perhaps properly exposed Woodward's Theory of
Petrification in saying[33], "Son erreur à cet égard vient de ce qu'il
n'a point réfléchi sur la manière dont se fait la _pétrifaction_. Il
ramollit d'abord les _pierres_ pour y faire entrer les coquilles, sans
bien connoître l'agent qu'il y employe; et il les duroit ensuite, sans
réfléchir au comment." To avoid this error or defect, M. de Luc, in his
Theory of Petrifaction, sets out with the acknowledged principle of
cohesion; and, in order to consolidate strata of a porous texture, he
supposes water carrying minute bodies of all shapes and sizes, and
depositing them in such close contact as to produce solidity and
concretion. Now, if Dr Woodward softened stones without a proper
cause, M. de Luc, in employing the specious principle of cohesion, has
consolidated them upon no better grounds; for, the application of this
principle is as foreign to his purpose, as is that of magnetism. Bodies,
it is true, cohere when their surfaces are closely applied to each
other; But how apply this principle to consolidation?--only by supposing
all the separate bodies, of which the solid is to be composed, to be
in perfect contact in all their surfaces. But this, in other words,
is supposing the body to be solid; and, to suppose the agent, water,
capable of thus making hard bodies solid, is no other than having
recourse to the fortuitous concourse of atoms to make a world; a thought
which this author would surely hold in great contempt.
[Note 33: Lettres Physiques et Morales.]
He then illustrates this operation of nature by those of art, in
building walls which certainly become hard, and which, as our author
seems to think, become solid. But this is only an imperfect or erroneous
representation of this subject; for, mortar does not become hard upon
the principle of petrification adopted by our author. Mortar, made of
clay, instead of lime, will not acquire a stony hardness, nor ever, by
means of water, will it be more indurated than by simply drying; neither
will the most subtile powder of chalk, with water and sand, form any
solid body, or a proper mortar. The induration of mortar arises from the
solution of a stony substance, and the subsequent concretion of that
dissolved matter, operations purely chemical. Now, if this philosopher,
in his Theory of Petrifaction, means only to explain a chemical
operation upon mechanical principles, why have recourse, for an example
in this subject, to mineral bodies, the origin of which is questioned?
Why does he not rather explain, upon this principle, the known
concretion of some body, from a fluid state, or, conversely, the
known solution of some concreted body? If again he means to explain
petrifaction in the usual way, by a chemical operation, in that case,
the application of his polished surfaces, so as to cohere, cannot take
place until the dissolved body be separated from the fluid, by means of
which it is transported from place to place in the mineral regions. But
it is in this preliminary step that lies all the difficulty; for, could
we see how every different substance might be dissolved, and every
dissolved substance separated from its solvent at our pleasure, we
should find no difficulty in admitting the cohesion of hard bodies,
whether by means of this doctrine of polished surfaces, or by the
principle of general attraction, a principle which surely comprehends
this particular, termed a cohesive power.
It must not be alleged, that seeing we know not how water dissolves
saline bodies, therefore, this fluid, for any thing that we know, may
also dissolve crystal; and, if water thus dissolves a mineral substance
in a manner unknown to us, it may in like manner deposit it, although
we may not be able to imagine how. This kind of reasoning is only
calculated to keep us in ignorance; at the same time, the reasoning of
philosophers, concerning petrifaction, does not in general appear to be
founded on any principle that is more sound. That water dissolves salt
is a fact. That water dissolves crystal is not a fact; therefore, those
two propositions, with regard to the power of water, are infinitely
removed, and cannot be assimilated in sound physical reasoning. It is
no more a truth that water is able to dissolve salt, than that we never
have been able to detect the smallest disposition in water to dissolve
crystal, flint, quartz, or metals. Therefore, to allege the possibility
of water being capable of dissolving those bodies in the mineral
regions, and of thus changing the substance of one body into another, as
naturalists have supposed, contrary to their knowledge, or in order to
explain appearances, is so far from tending to increase our science,
that it is abandoning the human intellect to be bewildered in an error;
it is the vain attempt of lulling to sleep the scientific conscience,
and making the soul of man insensible to the natural distress of
conscious ignorance.
But besides that negative argument concerning the insolubility of
crystal, by which the erroneous suppositions of naturalists are to
be rejected, crystal in general is found regularly concreted in the
cavities of the most solid rock, in the heart of the closest agate, and
in the midst of granite mountains. But these masses of granite were
formed by fusion; I hope that I shall give the most satisfactory proof
of that truth: Consequently, here at least there is no occasion for the
action of water in dissolving siliceous substances in one place, in
order to concrete and crystallise it in another.
In these cavities of the solid granite rock, where crystal is found
regularly shooting from a basis which is the internal surface of the
cavity, we find the other constituent substances of the granite also
crystallised. I have those small cavities, in this rock, from the island
of Arran, containing crystal, felt-spar, and mica, all crystallised in
the same cavity[34]. But this is nothing to the _druzen_ or crystalline
concretions, which are found in a similar manner among metallic and
mineral substances in the veins and mines; there, every species of
mineral and metallic substance, with every variety of mixture and
composition, are found both concreted and crystallised together in every
imaginable shape and situation.
[Note 34: The Chevalier Dolomieu makes the following observation.
Journal de Physique, Juillet 1791.
"J'ai été étonné de trouver au centre d'un énorme massif de granit, que
l'on avoit ouvert avec la poudre pour pratiquer un chemin, des
morceaux, gros comme le poing et au dessous, de spath calcaire blanc,
très-effervescent, en grandes écailles, ou lames entrecroisées. Il
n'occupoit point des cavités particulières, il n'y paroissoit le
produit d'une infiltration qui auroit rempli des cavités, mais il étoit
incorporé avec les feld-spath, le mica, et le quartz, faissoit masse
avec eux, et ne pouvoit se rompre sans les entraîner avec lui."
This great naturalist is convinced that the spar had not been here
introduced by infiltration, although that is the very method which he
employs to form concretions, not only of spar but of crystal, zeolite,
and pyrites, in the closest cavities of the most solid rocks of
basaltes. These four substances in this stone were so mixed together
that nothing but the fusion of the whole mass could explain the state in
which they appeared; but, thinking that such a supposition could not
be allowed, this naturalist, like a man of science when his data fail,
leaves the matter without any interpretation of his own. This however is
what he has not done in the case of basaltes, or that which he mistakes
for proper lavas, as I shall have occasion to show.]
Here is an infinite operation, but an operation which is easily
performed by the natural arrangement of substances acting freely in
a fluid state, and concreting together, each substance, whether more
simple or more compound, directing itself by its internal principle of
attraction, and affecting mechanically those that are concreting around
it.
We see the very same thing happen under our eye, and precisely in the
same manner. When a fluid mass of any mineral or metallic substance is
made to congeal by sudden cooling on the outside, while the mass within
is fluid, a cavity is thus sometimes formed by the contraction of the
contained fluid; and in this cavity are found artificial _druzen_, as
they may be called, being crystallizations similar to those which the
mineral cavities exhibit in such beauty and perfection.
Petrification and consolidation, in some degree, may doubtless be
performed, in certain circumstances, by means of the solution of
calcareous earth; but the examples given by M. de Luc, of those bodies
of lime-stone and agate petrified in the middle of strata of loose or
sandy materials, are certainly inexplicable upon any other principle
except the fusion of those substances with which the bodies are
petrified[35].
[Note 35: Vid. Lettre 28 et Lettre 103. Lettres Physiques et Morales.]
This subject deserves the strictest attention; I propose it as a
touchstone for every theory of petrification or perfect consolidation.
First, There are found, among argillaceous strata, insulated bodies of
iron-stone, perfectly consolidated; secondly, There are found, in strata
of chalk and lime-stone, masses of insulated flints; thirdly, There
are found, in strata of sea sand, masses of that sand cemented by a
siliceous substance; fourthly, In the midst of blocks of sand-stone,
there are found masses of loose or pure sand inclosed in crystallised
cavities; and in this sand are found insulated masses of crystallised
spar, including within them the sand, but without having the sparry
or calcareous crystallization disturbed by it. There are also other
globular masses of the same kind, where the sparry crystallization is
either not to be observed, or appears only partially[36]: And now,
lastly, In strata of shell-sand, there are found masses of consolidated
lime-stone or marble. In all those cases, the consolidated bodies are
perfectly insulated in the middle of strata, in which they must of
necessity have been petrified or consolidated; the stratum around the
bodies has not been affected by the petrifying substance, as there
is not any vestige of it there; and here are examples of different
substances, all conspiring to prove one uniform truth. Therefore, a
general theory of petrification or consolidation of mineral bodies must
explain this distinct fact, and not suffer it any longer to remain a
_lusus naturae_.
[Note 36: Mem. de l'Académie Royale des Sciences, an. 1775.]
Let us now consider what it is that we have to explain, upon the
supposition of those concretions being formed from a solution. We have,
first, To understand what sort of a solution had been employed for the
introducing of those various substances; secondly, How those concretions
had been formed from such solutions within those bodies of strata; and,
lastly, How such concretions could have been formed, without any vestige
appearing of the same substance, or of the same operation, in the
surrounding part of the stratum. Whatever may be the difficulty
of explaining those particular appearances by means of fusion and
mechanical force, it is plainly impossible to conceive those bodies
formed in those places by infiltration, or any manner of concretion from
a state of solution.
Naturalists, in explaining the formation of stones, often use a chemical
language which either has no proper meaning, or which will not apply to
the subject of mineral operations. We know the chemical process by which
one or two stony concretions may be formed among bodies passing from
one state to another. When, therefore, a change from a former state of
things in mineral bodies is judged by naturalists to have happened, the
present state is commonly explained, or the change is supposed to have
been made by means of a similar process, without inquiring if this had
truly been the case or not. Thus their knowledge of chemistry has led
naturalists to reason erroneously, in explaining things upon false
principles. It would be needless to give an example of any one
particular author in this respect; for, so far as I have seen, it
appears to be almost general, every one copying the language of another,
and no one understanding that language which has been employed.
These naturalists suppose every thing done by means of solution in the
mineral kingdom, and yet they are ignorant of those solvents. They
conceive or they imagine concretions and crystallizations to be formed
of every different substance, and in every place within the solid body
of the earth, without considering how far the thing is possible which
they suppose. They are constantly talking of operations which could only
take place in the cavities of the earth above the level of the sea, and
where the influence of the atmosphere were felt; and yet this is the
very place which we have it in our power to examine, and where, besides
the stalactite, and one or two more of the same kind, or formed on the
same principle, they have never been able to discover one of the many
which, according to their theory, ought always to be in action or
effect. So far from knowing that general consolidating operation, which
they suppose to be exerted in filling up the veins and cavities of the
earth by means of the infiltrating water of the surface, they do not
seem fully to understand the only operation of this kind which they see.
The concretion of calcareous matter upon the surface of the earth is
perhaps the only example upon which their theory is founded; and
yet nothing can be more against it than the general history of this
transaction.
Calcareous matter, the great _vinculum_ of many mineral bodies, is in
a perpetual state of dissolution and decay, in every place where the
influences of air and water may pervade. The general tendency of this
is to dissolve calcareous matter out of the earth, and deliver that
solution into the sea. Were it possible to deny that truth, the
very formation of stalactite, that operation which has bewildered
naturalists, would prove it; for it is upon the general solubility of
calcareous matter exposed to water that those cavities are formed, in
which may be found such collections of stalactical concretion; and the
general tendency of those operations is to waste the calcareous bodies
through which water percolates. But how is the general petrifaction or
consolidation of strata, below the surface of the sea, to be explained
by the general dissolution of that consolidating substance in the
earth above that level? Instead of finding a general petrifying or
consolidating operation in the part of the earth which we are able to
examine, we find the contrary operation, so far at least as relates to
calcareous spar, and many other mineral bodies which are decomposed and
dissolved upon the surface of the earth.
Thus in the surface of the earth, above the level of the sea, no
petrifying operation of a durable nature is found; and, were such an
operation there found, it could not be general, as affecting every kind
of substance. But, even suppose that such a general operation were found
to take place in the earth above the level of the sea, where there might
be a circulation of air and percolation of water, How could the strata
of the earth below the level of the sea be petrified? This is a question
that does not seem to have entered into the heads of our naturalists
who attempt to explain petrifaction or mineral concretion from aqueous
solutions. But the consolidation of loose and incoherent things,
gathered together at the bottom of the sea, and afterwards raised
into rocks of various sorts, forms by far the greatest example of
petrification or mineral operation of this globe. It is this that must
be explained in a mineral theory; and it is this great process of
petrifaction to which the doctrine of infiltration, whether for the
mechanical purpose of applying cohesive surfaces, or the chemical one of
forming crystallizations and concretions, will not by any means apply.
Nothing shows more how little true science has been employed for the
explanation of phenomena, than the language of modern naturalists, who
attribute, to stalactical and stalagmical operations, every superficial
or distant resemblance to those calcareous bodies, the origin of which
we know so well. It is not a mere resemblance that should homologate
different things; there should be a specific character in every thing
that is to be generalised. It will be our business to show that, in the
false stalactites, there is not the distinctive character of those water
formed bodies to be found.
In the formation of stalactical concretions, besides the incrustation as
well as crystallization of the stony substance from the aqueous vehicle
by which it had been carried in the dissolved state, we have the other
necessary accompanyments of the operation, or collateral circumstances
of the case. Such, for example, is that tubular construction of the
stalactite, first formed by the concretion of the calcareous substance
upon the outside of the pendant gut of water exposed to the evaporation
of the atmosphere; we then see the gradual filling up of that pervious
tube through which the petrifying water had passed for a certain time;
and, lastly, we see the continual accretion which this conducting body
had received from the water running successively over every part of
it. But among the infinite number of siliceous concretions and
crystallizations, as well as those of an almost indefinite variety of
other substances, all of which are attributed to solution, there is not
the least vestige of any collateral operation, by which the nature of
that concretion might be ascertained in the same manner. In all
those cases, we see nothing but the concreted substances or their
crystallizations; but, no mark of any solvent or incrusting process is
to be perceived. On the contrary, almost all, or the greatest part
of them, are so situated, and attended with such circumstances, as
demonstrate the physical impossibility of that being the manner in which
they had been concreted; for, they are situated within close cavities,
through which nothing can pervade but heat, electricity, magnetism,
etc.; and they fill those cavities more or less, from the thinnest
incrustation of crystals to the full content of those cavities with
various substances, all regularly concreted or crystallised according to
an order which cannot apply to the concretion of any manner of solution.
That there is, in the mineral system, an operation of water which may
with great propriety be termed _infiltration_, I make no doubt. But this
operation of water, that may be employed in consolidating the strata
in the mineral regions, is essentially different from that which is
inconsiderately employed or supposed by mineralists when they talk
of infiltration; these two operations have nothing in common except
employing the water of the surface of the earth to percolate a porous
body. Now, the percolation of water may increase the porousness of that
body which it pervades, but never can thus change it from a porous to a
perfect solid body. But even the percolation of water through the strata
deposited at the bottom of the sea, necessarily required, according to
the supposition of naturalists, must be refused; for, the interstices of
those strata are, from the supposition of the case, already filled with
water; consequently, without first removing that stagnant water, it is
in vain to propose the infiltration of any fluid from the surface.
This is a difficulty which does not occur in our theory, where the
strata, deposited at the bottom of the sea, are to be afterwards heated
by the internal fires of the earth. The natural consequence of those
heating operations may be considered as the converting of the water
contained in the strata into steam, and the expulsion of steam or
vapour, by raising it up against the power of gravity, to be delivered
upon the surface of the earth and again condensed to the state of water.
Let us now conceive the strata, which had been deposited at the bottom
of the sea, as exhausted of their water, and as communicating with the
surface of the earth impregnated with water. Here again we have the
power of gravity to operate in carrying down water to that place which
had been before exhausted by the power of heat; and in this manner, by
alternately employing those two great physical agents, we cannot doubt
that nature may convey soluble substances from above, and deposit them
below for the purpose of consolidating porous bodies, or of filling with
saline and earthy matter those interstices which had been originally
filled with water, when the strata were deposited at the bottom of the
sea. How far any marks of this operation may be perceived, by carefully
examining our mines and minerals, I know not; I can only say that, on
the contrary, whenever those examined objects were clear and distinct,
with the concomitant circumstances, so as to be understood, I have
always found the most certain marks of the solid bodies having concreted
from the fluid state of fusion. This, however, does not exclude the case
of infiltration having been previously employed; and I would intreat
mineralists, who have the opportunity of examining the solid parts of
the earth, to attend particularly to this distinction. But do not let
them suppose that infiltration can be made to fill either the pores or
veins of strata without the operation of mineral heat, or some such
process by which the aqueous vehicle may be discharged.
Not only are mineral philosophers so inconsiderate, in forming
geological theories upon a mere supposition or false analogy, they
have even proceeded, upon that erroneous theory, to form a geological
supposition for explaining the appearances of strata and other stony
masses in employing a particular physical operation, which is, that
of _crystallization_[37]. Now crystallization may be considered as a
species of elective concretion, by which every particular substance, in
passing from a fluid to a solid state, may assume a certain peculiar
external shape and internal arrangement of its parts, by which it is
often distinguished. But, to suppose the solid mineral structure of the
earth explained, like an enigma, by the word _crystallization_, is to
misunderstand the science by which we would explain the subject of
research; and, to form a general mineral theory thus upon that term,
is an attempt to generalise without a reason. For, when it were even
admitted that every solid body is crystallised, we thus know no more of
the geology of this earth, or understand as little of the general theory
of mineral concretion, as we did before;--we cannot, from that, say
whether it be by the operation of solution or of fusion which had
produced the perceived effect.
[Note 37: Journal de Physique; Avril 1753.]
M. de Carosi has wrote a treatise upon certain petrifactions[38]. In the
doctrine of this treatise there is something new or extraordinary. It
will therefore be proper to make some observations on it.
[Note 38: Sur la Génération du Silex et du Quartz en partie.
Observations faites en Pologne 1783, à Cracovie.]
The object of this treatise is to describe the generation of silex and
quartz, with their modifications or compositions, formed within mineral
bodies of a different substance. The natural history contained in this
little treatise is well described and sufficiently interesting. But It
is chiefly in order to examine the means which, according to the theory
of this treatise, are employed in petrifying bodies, that I consider it
in this place.
The first section of this treatise has for title, _Génération du Caillou
et du Quartz de la terre calcaire pure_. It may be worth while to
compare the natural history of this part of the earth with the flint and
chert found in our chalk and lime-stone countries. I shall therefore
transcribe what is worth observing upon that subject (p. 5.).
"Nous rencontrons chez nous dans les parties le plus montagneuses, et
les moins couvertes de terreau, ou tout-au plus de sable, entre de purs
rochers calcaires une quantité incroyable de cailloux (silex) tant en
boules, que veines, couches, et débris. Au premier coup d'oeil l'on
s'imagine que ce font des débris de montagnes éloignées, qui y furent
amenés par les eaux, mais, en examinant la chose de plus pres, on est
convaincu, que ce sont tout au contraire, des parties détachées des
montagnes de la contrée. Car il y a sur presque toute l'étendue de nos
montagnes calcaires une couche, ou pour mieux dire, un banc composé
de plusieurs couches de base calcaire, mais qui ou sont parsemées
irrégulièrement de boules, de rognons, de veines, et de petits filons
de silex, ou qui contiennent cette pierre en filon, veines, et couches
parallèles, et régulièrement disposées. Les boules et rognons de silex
y font depuis moins de la grandeur d'une petite noisette, jusqu'au
diamètre de plus de six pouces de nôtre mesure. La plupart de ces boules
tant qu'elles sont dans l'intérieur caché de la roche vive, et qu'elles
n'ont rien souffert de l'impression de l'air, ont, pour l'ordinaire, une
croûte de spath calcaire, au moyen de la quelle elles sont accrues à
la roche mere; ou pour mieux dire la croûte spatheuse fait l'intermède
entre le silex, et la roche calcaire, par où se fait le passage de l'une
à l'autre. Mais ceci ne vaut que de boules de silex entièrement formées.
C'est dont on peut même se convaincre à la vue, par beaucoup de pierres
dont le pavé de la ville de Cracovie est composé. Mais là, ou le silex
n'est pas encore entièrement achevé, la croûte spatheuse manque, en
revanche on y voit évidemment le passage par degrés successifs de la
roche calcaire au silex qui y est contenu, et les nuances de ce passage
sont souvent si peu marquées que même les acides minéraux ne suffisent
pas à les déterminer, ce n'est que le briquet, qui nous aide à les
découvrir. On voit bien ou la pierre calcaire s'enfonce en couleur, l'on
s'apperçoit, où sa dureté, ses cassures changent, mais, comme elle y
souffre encore quelque impression des acides, l'on ne sauroit déterminer
au juste le point, ou elle a déjà plus de la nature du silex, que de
celle de la chaux, qu'en la frappant du briquet.
"Tels sont les cailloux en boules et rognons avant leur état de
perfection, il y aura même au milieu une partie de pierre calcaire non
changée.
"Ceux au contraire, ou la nature à achevé son ouvrage, ont une croûte de
chaux endurcie, et sont purement du silex fini, mais de toutes couleurs,
d'un grain et d'une texture plus ou moins fine, qui passe assez souvent
par degrés dans les différentes variétés du noble silex. Ils ont, pour
l'ordinaire, dans leur intérieur une cavité, mais pas toujours au
centre, et qui vient apparemment de la consommation de cette partie
calcaire qui y resta la dernière, et n'en fut changée ou dissolute et
séparée, que lorsque le reste du silex étoit déjà entièrement fini. Ces
cavités sont toujours, ou enduites de calcédoine en couche concentriques
recouverte de petits cristaux fort brillans et durs de quartz, ou bien
seulement de ces derniers-ci. Par-fois il y a aussi du spath calcaire
crystallisé, mais cela est extrêmement rare. Quelque-fois enfin ces
cavités sont remplies d'une noix de calcédoine. Je n'ai réussi qu'une
seule fois en cassant un pareil silex en boule d'y trouver encore le
reste de l'eau de crystallisation."
The only remark that I would here make is this, that, if the
crystallization of those close cavities in the _silex_ had at any time
required water of solution, it must always have required it. But, if
there had been water of solution contained in those close cavities, for
the crystallization of the various things which are often found within
them, How comes it that this water is almost never found? I have good
reason to believe that water contained within a solid flint will not
make its escape, as does that contained in the _anhydrites_ of Mount
_Berico_, which are composed of a porous calcedony. But the siliceous
crystallizations within close cavities is a curious subject, which we
shall have occasion to examine more particularly in treating of agates.
We now proceed to the next section, which is the generation of silex and
quartz in marl, (p. 19.)
"Il y a des contrées, chez nous, qui out des étendus assez considérables
en long et en large, de montagnes de pierre de marne calcaire, dans
lesquelles on rencontre le même phénomène que dans celles de chaux pure;
c. a. d. nous y trouvons du silex de différentes variétés, et dans tous
les degrés successifs de leur formation, et de leur perfection. Outre
cela, nous y voyons encore quelque chose, qui semble nous conduire à
la découverte des moyens, dont se sort la nature pour effecteur cette
opération, et qui nous étoit caché dans les montagnes de chaux pure: ces
bancs de pierre marnesilicieuse, contiennent une partie considérable de
pyrites sulfureuses, qui non seulement y forment une grande quantité
de petits sillons, mais toute la masse de la montagne est rempli de
parcelles souvent presqu'imperceptibles de ce minéral. Ces pyrites sont
évidemment des productions du phlogistique et de l'acide contenu dans la
montagne.
"L'eau, qui s'y trouve ordinairement en assez grande abondance, en
détacha, extraha d'un et l'autre, et les combina après tous les deux
ensemble. Cette même eau les dissout derechef, et en fait de nouvelles
combinaisons. C'est ce qu'on voit évidemment là, ou la nature, ayant
commencé ses opérations, il n'y est resté de la pyrite, qu'une portion
de la partie inflammable liée à une base terrestre. Dans ces endroits
la marne n'est que fort peu sensible aux acides, et de blanche qu'elle
étoit, sa couleur est devenue presque noire. C'est là qu'on observe les
différens degrés du changement de la marne en silex, contenant, même
encore, par fois, de parties pyritéiques non détruites dans son
intérieur. Et comme la nature forme ici, de même, que dans la chaux pure
les silex, la plupart en boules ou rognons; comme les différent degrés
de métamorphoses de la marne en silex, sont ici beaucoup plus nombreuses
que là, de sorte qu'il y a des bandes entières, qui mériteroient plutôt
d'être appellés bandes silicieuses, que marneuses; comme il y a, enfin,
une grande quantité de pyrites, qu'ailleurs, il est très probable
qu'elle se serve là du même moyen qu'ici pour opérer la métamorphose en
question.
"Ne nous précipitons, cependant, pas à en tirer plus de conséquences;
poursuivons plutôt le fil de notre récit.
"Le silex, qui se trouve ici, est non seulement de différents degrés de
perfection, il est de plus d'une espèce. Il y a de la pierre à feu, 2 de
la calcédoine, 3 des agathes, et 4 différentes nuances et passages des
espèces ordinaires aux fines du silex.
"La pierre à feu, est, ordinairement dans son état de perfection d'un
grain assez fin, d'une couleur grise plus ou moins foncée, et même
donnant, dans le noirâtre, plus ou moins diaphane; ses cassures sont
concentriques ou coquillées, et sa masse est assez compacte. Outre sa
conformation ordinaire en boules et rognons, elle fait presque toujours
la noix de ursins marins, qui y font en grand nombre, et dont la
coquille est le plus souvent, et presque toujours de spath calcaire,
même au milieu d'une boule de silex parfait.
"Les calcédoines et agathes de ces couches sont toujours (au moins, je
ne les ai pas encore vues autrement) de coraux et autres corps marins
pétrifiés. Donc, il faut que les couches de pierres roulées, d'où j'ai
tiré ma collection citée plus haut, soyent des débris de montagne»
détruites de cette espèce. Il y en a qui sont très parfaites comme
celles qui composent ma collection, d'autres méritent plutôt d'être
rangées parmi les passages du silex ordinaire, et ses espèces plus
fines; d'autres encore sont, en effet, de vraies agathes, mais qui
renferment dans leur intérieur plus ou moins de parties non parfaites
presque calcaires, qui s'annoncent d'abord par leur couleur blanche,
par leur gros grains relativement au reste, par leur opacité, par leur
mollesse respective, et souvent même par leur sensibilité pour les
acides minéraux. Mais celles, qui sont finies, quoiqu'elles ayent, pour
la plupart, une couleur presque noire, ne laissent, cependant, pas
d'avoir aussi des teintes plus claires comme brunâtres, verdâtres,
rougeâtres, jaunâtres, bleuâtres, tachetées, veinées, etc. Leur clarté
n'est pas moins variable, que leur couleur, il y en a de presqu'opaques,
comme aussi de presque transparentes, sur tout là, ou la calcédoine
prédomine.
"Le quartz s'y trouve comme dans les pierres de la première section, c,
a, d, crystallisé, en groupes dans de petites cavités; quelquefois aussi
en veines. La calcédoine y est de même, ou bien en mamelons, ou bien en
stalactites, lorsqu'elle a de la place pour s'y déposer.
"Un phénomène encore plus curieux que cela est cette belle pyrite
sulphureuse jaune, comme de l'or, qui est quelquefois parsemée par tout
la substance de pétrifications agathisées, et qui apparemment y fut
déposée après la dite métamorphose à la faveur des petits pores, qui y
étoient restés ouverts."
I would beg that mineralists, who use such language as this, would
consider if it contains a distinct idea of the operation which they
would thereby describe, or if it does not contain either a contradiction
or an inconceivable proposition. It supposes a calcareous body to be
metamorphosed, somehow by means of the mountain acid, into a siliceous
body. But, finding many bodies of pyrites contained within that solid
flint, it is said, that, when the calcareous body was flintified, there
were left in it cavities which were afterwards filled with pyrites. Let
us reflect a moment upon this doctrine. These cavities were first open
to the outside of the flinty body; but now the pyrites with which they
had been filled is insulated in the solid flint. Here three things are
required; first, The calcareous body is to be flintified, at the same
time leaving the body full of small cavities open to the outside;
secondly, These cavities are to be filled with pyrites; lastly, These
mineral bodies are to be so inclosed within the flint, as to leave no
vestige of the former processes. This marly mountain itself, which had
been formed of loose materials gathered together at the bottom of the
sea, was first to be filled with pyrites, in various shapes, by means of
the phlogistic and the acid of the mountain. Here is proposed to us an
operation which is totally unknown, or of which we have no kind of
idea. But, let us suppose pyrites formed in this mountain, (of whatever
chemical substances), by means of water; Why should water again undo
that pyrites, in order to form other concretions? And, Why should the
flint be formed first with cavities, and then made solid, after pyrites
had been introduced into those cavities of the agate, and, as our author
expresses it, _parsemée pour toute la substance?_ Here are suppositions
which are not only perfectly gratuitous, but are also inconsistent with
any thing that we understand. This is not explaining nature; it is only
feigning causes[39].
[Note 39: The description of those insulated siliceous bodies,
containing in their closed cavities all the usual concretions of
calcedony and crystals, as well as full of small pyrites floating in the
solid flint, are extremely interesting to a mineral system, or such a
geological theory as should explain the present state of things in those
strata that had been formed by deposits of known materials at the bottom
of the sea; they are indeed such appearances as may be found, more or
less, in all consolidated strata. But it is this author's explanation of
that petrifaction which is our present object to consider; and, as he is
so particular in giving us his theory upon the subject, it is easy to
detect the error of his reasoning. Were those naturalists who explain
things only in general, by saying that water is the agent, and
infiltration the means employed by nature;--were these naturalists, I
say, to give us as particular a description of their process, it would
appear as inconsistent with the nature of things as that which we have
from this author, who examines nature very minutely, and who sees
distinctly that the infiltrating theory is inapplicable for the
explanation of those petrifactions.]
The third section has for title, "_Generation du Silex et Quartz de la
Pierre Puante_." Here we find an example worthy of being recorded,
as contributing to throw great light upon those mineral operations;
however, the opinion of our author and mine, upon this subject, differ
widely. He proceeds thus:
"Cette pierre n'est, comme chacun le sçait, qu'une pierre calcaire
contenant du bitume.
"Nos montagnes n'en contiennent seulement pas de simples couches, mais
il y en a même de grandes bancs fort épais.
"Le caillou, ou silex qui s'y génère, forme, tantôt de gros blocs
informes, qui occupent des cavités dans l'intérieure des montagnes,
tantôt, enfin, en forme de filons.
"J'ai remarqué cette métamorphose sur trois endroits différens, dans
chacun des quels la nature a autrement opéré.
"Sur l'un, la pierre puante fait un banc horizontal dans une montagne de
pierre calcaire crystalline, ou d'une espèce de marbre, qui contient
des couches et filons de métal. Ce banc de pierre puante y fait le toit
d'une couche de galène de plomb et de pierre calaminaire, et dans ses
cavités et fentes il y a non seulement des blocs de grandeur différente,
mais aussi des veines et petites bandes courtes de silex, tant
ordinaire, que noble c, a, d, de la pierre à feu, de calcédoine,
d'agathes, et même d'une espèce de cornaline jaune et rouge pâle. Je ne
m'arrêterai pas à en détailler les variétés, parce qu'elles sont trop
accidentelles. Je ne les connois pas même toutes, il s'en faut de
beaucoup, parce qu'elles se trouvent dans des anciennes mines négligées,
peut être depuis plus d'un siècle, et par conséquent peu accessibles. Je
ne doute, cependant pas, que, si l'on pouvoit mieux sonder le terrain,
on y trouveroit bien plus encore du peu que j'ai cité. Parmi ce silex,
il y a aussi de petites groupes et de petites veines de quartz solide et
crystallisé.
"Au second endroit la pierre puante fait un filon, ou si l'on veut,
une couche ou bande verticale, qui partage la montagne en deux parties
presqu'égales de l'épaisseur de trois aunes à peu près. La montagne,
ou cela se voit est aussi une ancienne mine de cuivre et de plomb,
consistant en plusieurs variétés de marbre, différent en couleur et en
grain, déposées par couches les unes sur les autres. Le filon de silex
est formé de feuilles alternatives de pierre puante et de silex, tous
les deux de couleur brun de bois à peu prés; mais le silex est plus
foncé que sa compagne. Ces feuilles alternatives, consistent d'autres
bien plus minces encore, qui souvent n'ont pas l'épaisseur d'une ligne,
mais ce qu'il y a de plus curieux, c'est que la même feuille est d'un
but de pierre porque, qui, vers le milieu, passe successivement en
silex, qui, à son tour, vers l'autre but, qui étoit exposé à l'air
repasse par les mêmes gradations en une espèce de tuffe calcaire. Ce qui
nous fait voir évidemment la génération et la destruction du silex, même
avec une partie des moyens par lesquels elle s'opère. Comme l'endroit de
cette découverte n'est accessible qu'à la superficie, je ne saurois dire
s'il y a d'autres variétés de silex outre la dite. Il l'est à supposer
autant par analogie, que par quelques morceaux qui ont de petites veines
transversales d'une espèce de calcédoine, et qui sont, même, sur leur
fentes, garnis de petits cristaux de roche. Mais ce qu'il y a de sur
c'est que ce filon, parvenu à une certaine profondeur, s'ennoblit et
contient du métal, c. a. d. de la galène de plomb, et de la pyrite
cuivreuse, j'y en ai trouvés de morceaux, qui en font de preuves
incontestables. Le caillou d'ici est un grain fin d'une texture forte,
peu transparent, donne beaucoup d'étincelles au briquet, mais ses
cassures sont écailleuses.
"La montagne calcaire du troisième lieu a une couche de pierre puante
épaisse de plusieurs aunes, qui, derechef contient de petites couches
irrégulières et des bandes transversales de silex, qui ont jusques â
six pouces passés d'épaisseur. La pierre puante est d'une couleur
gris-brune, d'un grain assez fin, et d'un tissu assez dur; ses cassures
sont irrégulières, mais plus la pierre s'approche du silex, plus elles
donnent dans le coquillé. Le silex ordinaire est d'un brun de bois, d'un
grain assez fin, et d'un tissu résistant, et ses cassures sont égales à
la pierre porque. Ce n'est pas là la seule variété, il y a, aussi, de la
calcédoine et des agathes de couleurs différentes. Même la pierre à
feu est assez souvent traversée de veines de calcédoine, de quartz
crystallisé, et de spath calcaire blanc en feuilles et en crystaux. Il
arrive que la même veine est composée de ces trois espèces de pierres à
la fois, de sorte que l'une semble passer dans l'autre, parce que les
limites réciproques sont, souvent, assez indistinctes. Il est évident,
que le silex est formé de la pierre puante, parce qu'on remarque ici
les mêmes phénomènes dont j'ai parlé plus haut, c. a. d. les passages
successifs de l'une dans l'autre pierre, tant en montant qu'en
descendant."
There is nothing particular in the siliceous mixture in this species of
lime-stone, except the vein of that substance. It is evident that this
vein, traversing the mountain, had been introduced in the fluid state
of fusion. I do not mean to say, that, in this particular case now
described, the evidence of that truth peculiarly appears; but that, from
the general nature of mineral veins breaking and traversing the solid
strata of the globe, no other conclusion can be formed; and that in
the particulars of this example there is nothing that could lead us to
suppose any other origin to the petrifactions contained in this vein
of stinking lime-stone. It is plain, that our author has imagined to
himself an unknown manner of executing his mineral metamorphoses. He
sees plainly that the common notion of infiltration will not at all
explain the evident confusion of those calcareous and siliceous bodies
which appear to him to be metamorphosing into each other. Nothing,
indeed, can explain those phenomena but a general cause of fluidity; and
there is no such general cause besides that of heat or fusion.
But to show how mineralists of great merit, gentlemen who have examined
systematically and with some accuracy, may impose upon themselves in
reasoning for the explanation of mineral appearances from limited
notions of things, and from the supposition of these having been formed
where they now are found, that is, upon the surface of the earth, I
would beg leave to transcribe what this author has said upon this
species of petrifaction. It is not that he is ignorant of what
mineralists have already said upon the subject; it is because he sees
the incompetency of their explanations in those particular cases; and
that he would employ some other more effectual means. (p. 50.)
"Toute terre calcaire à changer dans une autre doit, avant toute chose,
être rendue réfractaire ce qui ne peut se faire qu'en la saturant avec
un acide. Mais une terre simplement, saturée d'un acide, est d'une
réduction fort aisée, vu que l'acide n'y tient pas trop fort, d'ailleurs
ce n'est qu'un sel neutre terreux fort facile â dissoudre dans une
quantité suffisante d'eau. Or pour rendre cette union plus constante, il
faut que la terre alcaline s'assimile intimement à l'acide, ce qui ne
se sera jamais sans un intermedeliant, qui homogène les parties de ce
nouveau corps, et pour que cela ce fasse il est indispensable, qu'il
s'opère une dissolution foncière des parties terrestres de la chaux, qui
facilite l'ingress à l'acide, et à l'intermède pour qu'ils s'y lie bien
fortement. Supposons qu'il se forme une liqueur savonneuse de l'acide et
du phlogistique, que l'air fixe, mis en liberté, ouvre les interstices
des parties qui constituent la terre alcaline, qu'apres cela cette
liqueur savonneuse ayant l'entrée libre s'assimile à la terre en
proportion requise, que l'eau, qui servoit de véhicule dans cette
operation, s'évapore successivement, et emporte le superflu des
ingrediens, pour qu'il se puisse opérer le rapprochement le plus exacte
des parcelles ou molécules homogénées de nouveau corps qu'enfin les
molécules les plus pures et les mieux affinées soyent réunies en forme
liquide dans des cavités, et que par l'évaporation et séparation de
l'eau, ou elles nageoient, il s'en forme des crystaux n'aurons-nous
pas une boule de silex, avec de crystaux de quartz dans ses creux
intérieurs."
The supposed case is this; a calcareous body is to be metamorphosed
into a siliceous nodule, having a cavity within it lined with quartz,
crystals, etc. M. de Carosi means to inform us how this may be done.
Now, as this process requires no other conditions than those that may
be found upon the surface of this earth, the proper way to prove this
hypothetical theory, would be to exhibit such a mineral body produced
by those means. But, even supposing that such a process were to be
exhibited, still it would remain to be explained, how this process,
which requires conditions certainly not be found at the bottom of the
sea, could be accomplished in that place, where the strata of the earth
had been deposited, accumulated, consolidated, and metamorphosed.
This mineral process, which has been now described, will no doubt revolt
the opinions of many of our chemists as well as naturalists; and I
should not have thought of transcribing it, but as an example of that
inconclusive reasoning which prevails in mineralogical writings upon
this subject.
But this is not all. We have, upon this occasion, a most remarkable
example of the fallaceous views that may be taken of things; and of the
danger to science when men of sense and observation form suppositions
for the explanation of appearances without that strict conformity with
the principles of natural philosophy which is requited on all occasions.
Both M. de Carosi, and also M. Macquart[40], to whom our author
communicated his ideas and proper specimens, assert, that from their
accurate experience, they find calcedony growing daily, not only in the
solid body of gypsum, etc. while in the mine, but also in the solid
stone when taktn out of the mine, and preserved in their cabinet.
[Note 40: Vid. Essais de Minéralogie par M. Macquart.]
What answer can be made to this positive testimony of these gentlemen,
by a person who has not seen any such a thing, and who has not the
opportunity of examining the cases in which those naturalists may have
perhaps been led into some delusion? Were I however to conjecture upon a
subject in which I have not any positive information, I should suppose
that some part of the calcedony, like the _oculus mundi_ when dipped in
water, may be so transparent, while containing some portion of humidity,
that it is not easily distinguishable from the gypsum in which it is
concreted; but that in having the humidity evaporated, by being taken
out of the mine and exposed to the dry air, those portions of calcedony,
which did not before appear, may be perceived by becoming more
opaque[41].
[Note 41: From the description given in this treatise, and from the
drawings both of M. de Carosi and M. Macquart, I find a very valuable
inference to be made, so much the more interesting, as I have not found
any example of the like before. This arises from the intimate connection
which is here to be perceived between agate and gypsum. Now, upon this
principle, that the agate-calcedony had been formed by fusion, a truth
which, from the general testimony of minerals, I must presume, it is
plain, that those nodules of gypsum had been in the fluid state of
fusion among those marly strata, and that the gypseous bodies had been
penetrated variously with the siliceous substance of the calcedony.
The description of those siliceous penetrations of gypsum is followed by
this conclusion: "En voila assez, je crois pour faire voir que le silex
ci-décrit est effectivement une émanation du gypse, et non pas une
matière hétérogène amenée d'autre part et déposée, ou nous la voyons."
In this instance our author had convinced himself that the calcedony
concretions had not been formed, as he and other mineralists had before
supposed, by means of infiltration; he has not, however, substituted
any thing more intelligible in its stead. I do not pretend that we
understand mineral fusion; but only that such mineral fusion is a thing
demonstrable upon a thousand occasions; and that thus is to be explained
the petrification and consolidation of the porous and naturally
incoherent strata of the earth.]
There is, however, a subject in which I can more freely accuse this
author of being deceived. This naturalist says, that calcareous stones
become silex by a certain chemical operation; and that those flinty
bodies, in being exposed upon the surface of the earth, out of their
natural bed, are again, by a contrary chemical operation, changed from
flint to a calcareous substance. I will give it in his own words, (p.
56.)
"Cela dit, venons au fait. Tout silex progénéré de chaux, détaché de son
lieu natal, et exposé aux changemens de saisons, s'amollit, reçoit de
crevasses, perd sa transparence, devient, enfin, tout-à-fait opaque, le
phlogistique s'en évapore, l'acide en est détaché, lavé, et de
terre vitrescible, qu'il étoit, il redevient chaux, comme il étoit
auparavant."
Here is no question with regard to mere opinion, but to matter of fact;
and, in this case, nothing is more evident, than that upon the surface
of this earth, that is, in the examinable parts above the level of the
sea, there is no transition either of calcareous bodies into flint,
nor of flinty bodies into calcareous substance. Calcareous matter is
constantly dissolved by water, when it is exposed to the washing of
that fluid; and it is even dissolved out of the most perfect union or
combination with siliceous substance, and the most solid composition of
an insoluble body, as may be perceived in the decaying of feld-spar. A
superficial view of flints, which have come out of a body of chalk, may
have created such an opinion, which will not either bear the light of
chemical or mineral investigation. The subject of these chalk flints
will be minutely examined in its proper place.
Our author has carefully examined the subject of flintification; and the
country where he makes his observations would seem to be well disposed
for such a research. He has had great opportunity and inclination to
examine the subject which he writes upon; and he has given a distinct
account of what be has seen. His description of the flintification of
sand-stone is extremely interesting. I will therefore transcribe it,
both as a valuable portion of natural history, and also in order to
contrast this author's opinion, with regard to the means employed by
nature in petrifying bodies, and that which I maintain to be the general
consolidating operation of the globe. It is Section V. _Generation du
Caillou du Silex du Grès, ou Pierre Sablonneuse_.
"Tout grès est susceptible de cette métamorphose quant au grain et quant
à la couleur; depuis la bréccia quartzeuse jusqu'à la pierre à rasoir;
et depuis le grès blanc jusqu'au brun et presque noirâtre, tient ou non
tient, dur, ou presque friable, c'est indifférent, toutes ces variétés
donnent du silex, et surtout de la calcédoine, de la cornaline, et des
agathes. Quant au ciment je l'y ai toujours remarqué calcaire et faisant
effervescence avec les acides dans les endroits de la pierre qui
n'étoient point encore changés; et jamais je n'ai vu ce changement dans
du grès dont le ciment fut ou quartzeux ou argileux et réfractaire.
Ainsi le ciment entre pour quelque chose dans ce changement.
"Le commencement de cette métamorphose paroit (autant que j'ai pu
l'observer dans mes débris roulés) se faire par le ciment, qui dissout
là, où les agens eurent l'accès libre, rend les grains en quartz
mobiles, les emporte, les mêle avec sa masse dense-liquide, les dissout,
même en partie, et forme, dans cet état, des veines et de masses
calcédonieuse, carneoliques, ou d'une autre espèce de silex, au milieu
du grés peu, ou pas du tout, changé. Car autant que je puis voir, ce
n'est pas par couches ou veines qu'elle s'opère, mais par boules et
masses rond-oblongues. Au commencement ces veines et tâches sont fort
minces, et le reste du grés n'est point du tout, ou à peine sensiblement
changé hormis qu'il gagne, plus de consistence, à proportion du
changement souffert. Mais à mesure que le silex y augmente et se
perfectionne, on y apperçoit les degrés par lesquels a passé cette
operation. Les nuance du passage d'une pierre à l'autre deviennent plus
visibles, les veines et masses de silex grandissent au point, même,
qu'il y a jusqu'aux trois quart du grés changé en silex clair comme de
l'eau n'ayant que fort peu de grains de sable nageants dans sa masse.
Des morceaux de cette espèce sont rares à la vérité, mais j'en ai,
cependant, trouvé quelques uns. Ordinairement, dans les beaux morceaux,
le silex fait la base, et le sable y est, comme nageant tantôt en grains
séparés tantôt en parties et flocons. Dans les pieces moins belles, le
sable fait la base, et le silex sert à la fois de ciment, et forme aussi
plus ou moins de veines, qui traversent la masse en maintes et maintes
directions. Mais si c'est un grès à gros grains, ou de la bréccia, alors
le reste prend la nature silicieuse mêlé de sable fin, et les gros
grains de quartz restent tels, qu'ils étoient, sans changer. J'ai
déjà remarqué que cette métamorphose semble s'opérer, comme celle des
cailloux d'origine calcaire en forme approchans la sphérique, il faut
encore y a jouter, que j'ai lieu de croire, qu'elle se fasse aussi du
dedans en dehors, tout, comme la décomposition se fait du dehors au
dedans.
"Il arrive dans cette pierre, comme dans toute autre, qu'il se forme
des crystallisations dans les cavités. Lorsqu'elles sont de silex, leur
figure est toujours mamelonnée, mais leur eau ou pureté, leur grandeur
et leur couleur n'est pas par tout égale. Il y en a qui sont grands, et
de la plus pure calcédoine, d'autres sont petits et chaque goutte ou
mamelon contient un grain de sable, de facon que cela a l'air d'un grès
crystallisé en mamelons ou stalagmitique. D'autres encore sont, de
calcédoine, mais recouverts d'une croûte, tantôt blanche qui fait
effervescence avec l'acide minéral, et qui est, par conséquent, de
nature calcaire; tantôt cette croûte est bleue foncée nuancée de
bleu-celeste; tantôt, enfin, elle est noire, mais toutes les deux
réfractaires. Outre ces crystallisations silicieuses, il y en a, quoique
rarement, de quartzeuses, qui ou forment de petites veines de crystal,
ou bien des groupes de crystaux quartzeux, ou qui enfin, enduisent les
mamelons de silex."
Our author then makes a specification of the different varieties; after
which he continues, p. 69.
"Après tout ceci, l'on conviendra j'espère, que nôtre grais est une
pierre bien singulière, et surpassant, à bien des égards, le grais,
faussement dit crystallisé, de Fontainebleau. La raison de la figure du
grais François est fort évidente, c'est le spath calcaire, qui lui
sert de ciment, qui la lui fit prendre; mais qu'est-ce qui opère les
métamorphoses racontées dans notre grais siliceux? Seroit-ce son ciment
calcaire ou marneux par les mêmes raisons, qui font changer la marne en
silex? La chose est très-probable, et je n'en saurois pas même, deviner
d'autre. En ce cas la nature auroit un moyen d'opérer par la voie
humide, ce que nous faisons dans nos laboratoires en quelque façon, par
la voie sèche, c, a, d, de fondre et liquéfier la terre vitrescible, au
moyen des alcalis; secret que nous lui avons déjà arraché en partie, en
faisant la liqueur silicieuse."
"Je n'ose, cependant, décider pas même hypothétiquement, sur cette
matière, pour n'avoir pu observer la nature dans ses ateliers, et parce
que je ne possède que des pièces, qui détachées de leur lieu natal,
depuis un très long-tems, furent exposées aux intempéries des saisons,
où elles peuvent avoir souffert bien de changemens."
There cannot be a more fair exposition of facts; and it is only our
author's opinion of this mineral transmutation that I would controvert.
I do not pretend to understand the manner of operating that our author
here supposes nature to take. I only maintain, that here, as every where
in general, the loose and incoherent strata of the globe have been
petrified, that is, consolidated, by means of the fusion of their
substances; and this I think is confirmed from the accurate description
here given of the flintification of sand-stone. Here is described very
distinctly an appearance which is very common or general on those
occasions; this is the parts or particles of stone floating in the fluid
siliceous substance, and there dissolving more or less.
M. de Carosi describes very systematically the generation of silex,
calcedony, onyx, and quartz, in calcareous earth, marl, gypsum,
sand-stone, and also what he terms _terre glaise, ou de l'Argile_. It is
in this last that we find a perfect analogy with what is so frequent in
this country of Scotland. These are the agates, calcedonies, calcareous
and zeolite nodules, which are found produced in our whin-stone
or subterraneous lavas, that is, the amygdaloides of Crondstedt.
Naturalists explain the formation of those nodular bodies differently.
The Chevalier de Dolomieu supposes these rocks to have been erupted
lavas, originally containing cavities; and that these cavities in the
solid rock had been afterwards filled and crystallised, by means of
infiltration, with the different substances which are found variously
concreted and crystallised within the solid rocks. Our author, on the
contrary, supposes these formed by a species of chemical transmutation
of calcareous and argillaceous earths, which, if not altogether
incomprehensible, is at least not in any degree, so far as I know, a
thing to be understood.
This is not the place where that subject of these particular rocks,
which is extremely interesting, is to be examined. We shall afterwards
have occasion to treat of that matter at large. It is sufficient here to
observe, that our author finds occasion to generalise the formation of
those petrifactions with the flintifications in calcareous and gypseous
bodies. When, therefore, the formation of any of them shall be
demonstrated, as having taken its origin in the fusion of those
substances, this mode of operation, which is generalised in the
consolidation of strata, will be properly inferred in all the rest.
Petrifaction is a subject in which mineralogists have perhaps wandered
more widely from the truth than in any other part of natural history;
and the reason is plain. The mineral operations of nature lie in a part
of the globe which is necessarily inaccessible to man, and where the
powers of nature act under very different conditions from those which we
find take place in the only situation where we can live. Naturalists,
therefore, finding in stalactical incrustation a cause for the formation
of stone, in many respects analogous to what is found in the strata of
the earth, and which had come from the mineral region in a consolidated
state, have, without due consideration, attributed to this cause all the
appearances of petrifaction or mineral concretion. It has been one of
the objects of this work to show that this operation of incrustation,
or petrifaction by means of solution, is altogether ineffectual for
producing mineral concretions; and that, even were it capable of forming
those mineral bodies, yet that, in the solid parts of this earth, formed
by a deposit of travelled materials at the bottom of the sea, the
conditions necessary to this incrustating process do not take place.
Those enlightened naturalists who have of late been employed in
carefully examining the evidences of mineral operations, are often
staggered in finding appearances inconsistent with the received doctrine
of infiltration; they then have recourse to ingenious suppositions, in
order to explain that enigma. In giving examples of this kind. I have in
view both to represent the natural history these mineralists furnish
us with, which is extremely interesting, and also to show the various
shapes in which error will proceed, when ingenious men are obliged to
reason without some necessary principle in their science. We have just
now had an example in Europe; I will next present the reader with one
from Asia.
M. Patrin, in his _Notice Minéralogique de la Daourie_, (Journal de
Physique, Mars 1791) gives us a very distinct account of what he met
with in that region. Describing the country of Doutchersk upon the river
Argun, in Siberia, he proceeds thus:
"Ces colines sont formées d'un hornstein gris qui paroit se convertir en
pierre calcaire par l'action des météores; car tout celui qu'on prend
hors du contact de l'air donne les plus vives étincelles, et ne fait pas
la moindre effervescence avec les acides, même après avoir été calciné;
et l'on observe celui qui est à découvert, passer, par nuances
insensibles, jusqu'à l'état de pierre calcaire parfaite de couleur
blanchâtre."
Here M. Patrin has persuaded himself, probably from an imperfect
examination of the subject, that there takes place a mineral
metamorphosis, which certainly is not found in any other part of the
earth, and for which he does not find any particular cause. The natural
effect of the meteors, in other parts of the earth, is to dissolve the
calcareous substance out of bodies exposed to those agents; and the
gradation from the one of those two things to the other, which seems to
be the data on which he had proceeded in forming his conclusion, is not
sufficient to prove the metamorphosis, even were there not so strong a
physical objection to it; for, it is by no means unusual for mineral
bodies to graduate thus from one substance to another. However that be,
this is not the principal object of the example[42].
[Note 42: Here we have well informed naturalists reasoning with all the
light of our present mineralogy, and maintaining, on the one hand, that
gypsum is transformed into calcedony, by the operation of the meteors,
or some such cause; and, on the other, that a siliceous substance is by
the same means converted into lime-stone. What should we now conclude
from this?--That calcareous and siliceous substances were mutually
convertible. But then this is only in certain districts of Poland and
Siberia. Every where, indeed, we find strange mixtures of calcareous and
siliceous bodies; but neither mineralists nor chemists have, from these
examples, ventured to affirm a metamorphosis, which might have spared
them much difficulty in explaining those appearances.
This is a subject that may be taken in very different lights. In one
view, no doubt, there would appear to be absurdity in the doctrine of
metamorphosis, as there is now a days acknowledged to be in that of
_lusus naturae_; and those reasoning mineralists might thus, in the
opinion of some philosophers, expose their theory to contempt and
ridicule. This is not the light in which I view the subject. I give
those gentlemen credit for diligently observing nature; and I applaud
them for having the merit to reason for themselves, which would seem to
be the case with few of the many naturalists who now speak and write
upon the subject.
Let us now draw an inference, with regard to this, in judging of the
different theories. Either the received system concerning mineral
operations is just, in which case those gentlemen, who employ a secret
metamorphosis, may be to blame in laying it aside; or it is erroneous
and deficient; and, in that case, they have the merit of distinguishing
the error or deficiency of the prevailing system. How far they have seen
the system of nature, in those examples which they have described,
is another question. In the mean time, I am to avail myself of the
testimony of those gentlemen of observation, by which the insufficiency
at least of the received mineral system is acknowledged.]
After speculating upon the effect of the ancient ocean upon the
mountains of that country, he proceeds as follows:
"Je laisse ces conjectures pour remarquer un fait singulier: la colline,
qui est au nord de l'église de la fonderie, a son arrête composée de ce
hornstein qui se décompose en pierre calcaire; mais ici, les parties,
qui sont ainsi décomposées, offrent une substance calcédonieuse
disposées par zones concentriques, comme on l'observe dans les agates
d'oberstein; mais ce ne sont point ici des corps parasites formés par
infiltration dans des cavités pré-existantes comme les agates; on voit
que ce sont les parties constituantes de la roche qui, _par un
travail interne_, et par une sorte de crystallisation, out pris cette
disposition régulière (que ce mot de _crystallisation_ ne révolte point,
j'appelle ainsi toute tendance à prendre une forme constante, polyèdre
ou non polyèdre.) Les couches les plus voisine du centre sont nettes et
distinctes; peu-à-peu elles le sont moins, et enfin elles s'évanouissent
et se confondent avec le fond de la roche. Chaque assemblage de ces
zones a une forme ronde ou ovale plus ou moins régulière de sept à huit
pouces de diamètre.
"Cela ressemble en grand à ce qu'on observe dans les pierres oeillées,
et la cause est vraisemblablement la même. Je le répète, je regarde
cette disposition régulière comme une véritable cristallisation, qui
peut s'opérer et qui s'opère en effet dans l'intérieur des corp les plus
solide, tant qu'ils sont fournis à l'action des agens de la nature.
"Tous ceux qui visitent l'intérieur de la terre savent que les roches
mêmes le plus compactes y sont intimement pénétrées d'humidité, et ce
fluide n'est certainement pas l'eau pure; c'est l'agent qui opère toutes
les agrégations, toutes les cristallisations, tous les travaux de la
nature dans le règne minéral. On peut donc aisément concevoir qu'à la
faveur de ce fluide, il règne, dans les parties les plus intimes des
corps souterrains, une circulation qui fait continuellement changer de
place aux élémens de la matière, jusqu'a ce que réunis par la force des
affinités, les corpuscules similaires prennent la forme que la nature
leur a assignée."
Those nodular bodies or figured parts which are here inclosed in the
rock, are evidently what may be called calcedony agates. M. Patrin is
persuaded, from the examination of them, that they had not been formed
in the manner of German agates, which he supposes is by mean of
infiltration; and he has endeavoured to conceive another manner of
operating, still however by means of water, which I suppose, according
to this hypothesis, is to dissolve substances in one part, and deposits
them in another, There must certainly be some great _desideratum_ in
that mineral philosophy which is obliged to have recourse to such
violent suppositions. First, water is not an universal solvent, as it
would require to be, upon this supposition; secondly, were water allowed
to be an universal menstruum, here is to be established a circulation
that does not naturally arise from the mixture of water and earth; and,
lastly, were this circulation to be allowed, it would not explain the
variety which is found in the consolidation and concretion of mineral
bodies.
So long, therefore, as we are to explain natural appearances by
reasoning from known principles, and not by ascribing those effects to
preternatural causes, we cannot allow of this regular operation which
M. Patrin alleges to be acting in the interior parts of the most solid
bodies. This is indeed evident, that there has been a cause operating
in the internal parts of the most solid bodies, a cause by which the
elements, or constituent parts of those solid bodies, have been moved
and regularly disposed, as this author very well observes must have been
the case in our agates or eyed stones; but to ascribe to water this
effect, or to employ either an ineffectual or an unknown cause, is not
to reason philosophically with regard to the history of nature; it is to
reason phantastically, and to imagine fable.
M. Monnet has imagined a petrifying power in water very different
from any that has hitherto been conceived, I believe, by natural
philosophers, and I also believe, altogether inconsistent with
experience or matter of fact; but as it is not without good reason that
this naturalist has been induced to look out for a petrifying cause
different from any hitherto supposed, and as he has endeavoured very
properly to refute the systems of petrification hitherto received,
I would beg leave to transcribe his reasoning upon the subject in
corroboration of the present theory of consolidation by the means of
fusion.
It is upon occasion of describing one of the species of alpine stone
or schistus which contains quartzy particles. _Nouveau voyage
minéralogique, etc._ Journal de Physique Aoust 1784.
"Il y a loin de cette pierre, que je regarde comme une variété de roches
ardoisées, aux véritable ardoises. La composition de toutes ces pierres
est due aux terres quartzeuses et argileuses, et à la terre talqueuse,
que je démontrerai un jour être une espèce particulière et distincte des
autres, qui constitue les bonnes ardoises, et fait, ainsi que le quartz,
qu'elles résistent aux injures de l'air, sans s'effleurir, comme je
ferai voir que cette terre, qu'on désignera sous la dénomination de
terre talqueuse, si l'on veut, résiste au grand feu sans se fondre. Les
différences de toutes ces pierres, quoique composées des mêmes matières,
mais dans des proportions différentes, sont frappantes, et pourroient
faire croire qu'elles n'appartiennent pas à ce genre. Mais qui ne voit
ici que toutes ces différences, ou ces variétés, ne sont dues qu'aux
modifications de la matière première, qu'elle a éprouvées, soit en se
mêlant avec des matières hétérogènes, prévenantes du débris des êtres
qui ont existé, comme l'argile, par exemple, qui, de l'aveu de presque
tous les naturalistes, est le produit de l'organization des plantes, ou
soit en se mêlant avec de la matière déjà solidifiée depuis long-temps?
Or nous ne craignons pas de dire, ce que nous avons dit plusieurs fois
quand l'occasion s'en est présentée, que cette matière unique, que
se modifie selon les occasions et les circonstances, et qui prend
un caractère analogue au matières qu'elle rencontre, est l'eau, que
beaucoup de naturalistes cherchent vainement ailleurs. Ils ne peuvent
comprendre, malgré les exemples frappans qui pourroient les porter à
adopter cette opinion, que ce fluide général soit l'élément des corps
solides du règne minéral, comme il est de ceux du règne végétal et du
règne animal. L'on cherche sérieusement, par des expériences chimiques,
à découvrir si l'eau est susceptible de se convertir en terre comme
si la nature n'avoit pas d'autre moyen que nous de la faire passer de
l'état fluide à l'état solide. Voyez le spath calcaire et le quartz
transparens; est il à présumer qu'ils ne sont que le résultat du dépôt
des matières terreuses fait par les eaux? Mais, dans ce ca-là encore,
il faut supposer que l'eau qui est restée entre ces partie s'est
solidifiée; car, qu'est-elle donc devenue, et quel est donc le lien qui
a uni ces parties et leur a fait prendre une forme régulière? Il est
vrai qu'on nous parle d'un suc lapidifique; mais c'est-la un être de
raison, dont il seroit bien plus difficile d'établir l'existence, que de
croire à la solidification de l'eau. On nous donne cependant comme un
principe certain que l'eau charie d'un lieu à un autre les matières
qu'il a dissoutes, et qu'elle les dépose à la maniere des sels. Mais
c'est supposer une chose démentie par l'experience; savoir, que l'eau
ait la propriété de dissoudre les matières terreuses, telles que la
quartzeuse. A la vérité, M. Auchard de Berlin y joint de l'air fixe;
mais cet air fixe ne sauroit tenir en dissolution un atome de quartz
dans l'eau; et quelle qu'ait été l'exactitude de ceux qui ont répété
les expériences de M. Auchard, on n'a pu réussir à imiter la nature,
c'est-à-dire, à former des cristaux quartzeux, comme il a annoncé. Que
l'eau ait la faculté de tenir en dissolution quelques petites parties
de terre calcaire, au moyen de cet air fixe, il n'en faut pas conclure
qu'elle puisse former de cette maniere tous les cristaux calcaires, sans
que l'eau elle-même y concoure pour sa part; car ce seroit conclure
quelque fois que la partie seroit égale au tout. Voyez ces géodes
calcaire et argileuses, qui renferment des cristaux nombreux de quartz
ou de spath calcaire; ne sont ils que le résultat du dépôt de l'eau
qui y a été renfermée, ou que la cristallization pure et simple des
molécules que vous supposez avoir été tenues en dissolution par cette
eau? Il naîtroit de cette opinion une foule d'objections qu'il seroit
impossible de résoudre. Cependant M. Guettard, dans la minéralogie du
Dauphiné, qui vient de paroître, ouvrage très-estimable à beaucoup
d'égards, explique, selon cette maniere de penser, la formation de
cristallizations quartzeuses qu'on trouve dans certaines géodes de
cette province, et celle des mines de cristal des hautes montagnes. En
supposant même comme vraie l'explication qu'il en donne, on trouveroit
en cela un des plus grands problème, et des plus difficiles à résoudre
qu'il y ait en minéralogie; car d'abord il faudroit expliquer comment un
si petite quantité d'eau que celle qui a été renfermée dans les géodes,
et celle qui est parvenue dans les fentes des rochers, ont pu fournir
un si grande quantité de matière que celle qui constitue ces
cristallisations, et ce qui n'est pas le moins difficile à concevoir,
comment l'eau a pu charrier cette matière à travers tant de matières
différentes, et la conserver précisément pour cette destination;
comment, par exemple, l'eau est venue déposer de la terre quartzeuse
dans les masses énormes de pierres calcaires, qui forment la côté qui
domine le village de Champigny, à quatre lieues de Paris, au delà de
Saint-maur; car s'il nous faut citer un exemple frappant de cette
singularité, et à portée d'être vue des naturalistes qui sont dans la
capitale, je ne puis mieux faire que de citer cette côté, une des plus
curieuses de la France, et que je me propose de fair connoître en détail
dans la troisième partie de la minéralogie de la France. On verra,
dis-je, dans cette bonne pierre à chaux, et une de plus pure des
environs de Paris, de très-abondantes cristallisations de quartz
transparent, et quelque fois de belle eau, que les ouvriers sont forcés
de séparer de la partie calcaire, à laquelle elles adhèrent fortement.
Mais c'est trop nous arrêter à combattre une opinion qui doit son
origine aux premières idées qu'ont eues les premiers observateurs en
minéralogie, qui se détruira d'elle même comme tant d'autres dont il
nous reste à peine le souvenir."
We find here an accurate naturalist, and a diligent observer, who, in
conformity with what my sentiments are upon the subject, thinks it
impossible that the crystallizations in close cavities, and concretions
of different solid substances within each other, which so frequently
occur in the mineral regions, could have been produced, by means of
solution and crystallization, from a fluid vehicle. But what has he
now substituted in place of this solution, in order to explain
appearances?--a mere supposition, viz. that nature may have the power
of converting water, in those secret places, into some other thing; or
rather that the substance of water is here converted into every other
thing; for, though he has only mentioned quartz and calcareous spar,
what mineral substance is there that may not be found in those close
cavities? They are actually almost all, not even excepting gold; for,
small grains of gold are inclosed within the cavities of a porous stone,
in the Siberian mine. Now, for what purpose should nature, (to the power
of which we are not to set a limit) have such an object in view as
to convert water into every thing, unless it were to confound human
understanding? For, so far as human experience has been as yet able to
reach, there would appear to be certain elementary substances; and among
these is water, or the principles of that fluid[43]. But because water
is so generally found in bodies, and so necessarily in most of the
operations of this world, why convert it into every other thing? Surely,
for no better reason than that there has not occurred to this mineralist
any other way of explaining certain natural appearances which aqueous
solution could not produce. Here is no dispute about a matter of fact;
it is on all hands allowed, that in certain cavities, inaccessible to
any thing but heat and cold, we find mineral concretions, which contain
no water, and which, according to the known operations of nature, water
could not have produced; must we therefore have recourse to water acting
according to no known principle, that is to say, are we to explain
nature by a preternatural cause?
[Note 43: Water is now considered by men of science, as a compound
substance; this doctrine, which seems to follow so necessarily from the
experiments of the French philosophers, must be tried by the growing
light of chemical science. In the oxygenating operation of inflammable
and combustible bodies when burning, those ingenious chemists overlooked
the operation of _phlogistic matter_, which has no weight, and
which escapes on that occasion, as I have had occasion to show in a
dissertation upon phlogiston, and in the Philosophy of Light, Heat,
and Fire. How far this view, which I have given of those interesting
experiments, may lead to the explanation of other collateral phenomena,
such as that of the water produced, I will not pretend to conjecture.
One thing is evident, that if the weight of the water, procured in
burning inflammable and vital air, be equal to that of those two gasses,
we would then have reason to conclude, either that water were a compound
substance, or that vital air, and inflammable vapour were compounds of
water and the matter of light, or solar substance.]
I dare say that this is not the view that M. Monnet takes of the
subject, when he thinks to explain to himself the concretion of
those different substances by means of water; but, according to my
apprehension of the matter, his theory, when sifted to the bottom, will
bear no other construction; and, unless he shall consider water like the
matter of heat, as capable of producing the fluidity of fusion, and of
being also again abstracted from the fluid, by pervading the most solid
body, which would then be a substance different from water, he must
employ this aqueous substance as a menstruum or solvent for solid
bodies, in the same manner as has been done by those naturalists whom
he he justly censure, and conform to those erroneous ideas which first
observations, or inaccurate knowledge of minerals, may have suggested to
former naturalists.
It is the dissolution and concretion of siliceous substance, no
doubt, that gives such difficulty to our naturalists in explaining
petrifaction: they have, however, something apparently in their favour,
which it may be proper now to mention.
In the _first_ place, although siliceous substance is not soluble, so
far as we know, by simple water, it is soluble by means of alkaline
substance; consequently, it is possible that it may be dissolved in the
earth.
_Secondly_, The water of Giezer in Iceland, actually petrifies bodies
which are alternately imbibed with that hot water and exposed to the
air. This water, therefore, not only contains siliceous substance in a
dissolved state, but deposits this again, either by means of cooling,
or being aerated, or of evaporating. Consequently, without knowing the
principle upon which it proceeds, we here perceive a natural operation
by which siliceous petrifaction may be performed.
_Lastly_, We have another principle for the dissolution of siliceous
substance. This is the fluor acid which volatilises the siliceous
substance. This, however, requires certain conditions, which cannot be
found as a general cause in the mineral regions.
Thus we would seem to have every thing necessary for explaining the
concretion and crystallization of siliceous bodies, provided we could
find the proper conditions requisite for that operation; for whether it
shall be by means of acid or alkaline substances that siliceous matter
is to be dissolved, volatilised, and transported from one place to
another, it is necessary that those dissolving substances should be
present upon those occasions. Nor is it sufficient only to dissolve the
siliceous substance which is to be transported; the necessary conditions
for the concretion again of the dissolved substances, whatever these may
be, are also absolutely required for this operation. Now, though those
requisite conditions may be, upon many occasions, allowed in the earth,
it is not according to the theory of our modern naturalists, who explain
petrifaction upon the principles of simple infiltration of water,
that any advantage can be taken of those conditions; nor are natural
appearances to be explained without employing more complicated chemical
agents in the mineral regions.
To this subject of the petrifactions of Giezier, I may now add the
information which we have received in consequence of a new voyage from
this country to Iceland.
When Sir Joseph Banks returned from his expedition to Iceland, he landed
at this place; and, having brought specimens of the petrifications of
Giezer, Dr Black and I first discovered that these were of a siliceous
substance. I have always conjectured that the water of Giezer must be
impregnated with flinty matter by means of an alkaline substance, and
so expressed my opinion in the Theory of the Earth published in the
Transactions of the Edinburgh Royal Society. We have therefore been very
desirous of procuring some of that water, in order to have it analysed.
An opportunity favourable to our views has occurred this summer. Mr
Stanley set out from this place with the same purpose of examining
Iceland. He was so good as to ask of Dr Black and I what inquiries we
would incline that he should make. We have now, by the favour of this
gentleman, obtained specimens of the petrifactions of Giezer; and, what
is still more interesting, we have procured some of the water of those
petrifying boiling springs.
It appears from these specimens, that the boiling water which is ejected
from those aqueous volcanoes, if we may use the expression, is endued
with the quality of forming two different species of petrifaction or
incrustation; for, besides the siliceous bodies, of which we had before
received specimens, the same stream of water incrustates its channel
with a calcareous substance. All the specimens which I have seen consist
of incrustation, some purely siliceous, some calcareous, and others
mixed of those two, more or less.
Dr Black has been analysing the water; and he finds in it siliceous
matter dissolved by an alkaline substance, in the manner of liquor
silicum[44]. My conjecture has thus been verified.
[Note 44: See Trans. of the Edin. Royal Society.]
It must not be alleged that nature may operate in the mineral regions,
as she does here upon the surface in the case of Giezer. Such an
argument as this, however sound it may be in general, will not apply to
the subject of which we treat at present. There is no question about
the limiting the powers of nature; we are only considering nature as
operating in a certain determined manner, viz. by water acting simply
upon the loose materials of the land deposited at the bottom of the
sea, and accumulated in regular strata, one upon another, to the most
enormous depth or thickness. This is the situation and condition of
things in which nature is to operate; and we are to find the means of
consolidating those strata, and concreting every species of substance
in almost every possible composition, according to some known physical
principle. Here is an operation which is limited; for, we must reason
strictly, according to the laws of nature, in the case which we have
under consideration; and we cannot suppose nature as ever transgressing
those laws.
It is acknowledged, that, by means sometimes of an aeriform, sometimes
of an alkaline, perhaps also of an acid substance, calcareous matter is
dissolved in the earth, and certain metallic substances, such as lead
and iron. This solution also, upon particular occasions, (where the
proper conditions for separating the solvent from the dissolved
substance exist), forms certain concretions; these are sometimes a mere
incrustation, as in the case of the siliceous incrustation of Giezer,
sometimes again in a crystallised or sparry form, as in the case of
stalactical concretions. But here is no question of those cases where
the proper conditions may be found; first, of dissolving the substance
which is afterwards to be concreted; secondly, of separating the
menstruum from the dissolved substance; and, lastly, of removing the
fluid deprived of its solution, and of supplying a new solution in its
room; the question is, how far those concretions are formed where those
conditions do not take place. Now, this last case is that of almost all
mineral concretions.
It must not be here alleged that certain concretions have been found in
mines posterior to these having been worked by man; consequently, that
those concretions have been formed by nothing but the infiltration of
water. In those cases, where such concretions are truly found, I am
persuaded that all the conditions proper to that operation will also
be found; and it is only, I believe, in those cases where such proper
conditions may be found, that this aqueous concretion ever appears. Now,
if we shall except calcareous stalactite, and the bog ore of iron, How
seldom is it that any appearance of those aqueous mineral concretion
ever is found? Those very few cases in which they are found, afford the
strongest proof against these being operations general to the globe, or
proper mineral concretions; because it is only where all the necessary
conditions conspire in each contributing its part, that the effect is
accomplished; and this is a thing which cannot possibly take place in
the aquiform strata below the surface of the sea. But, without attending
to this clear distinction of things perfectly different, naturalists are
apt to see false analogies, and thus in generalising to form the most
erroneous theories.
I shall now give an example of this fallaceous manner of reasoning; it
is in the case of certain mineral appearances which are erroneously
considered as stalactical concretions.
The only true stalactical bodies are of a calcareous substance; they are
formed by water containing this substance in a dissolved state; and the
principles upon which this particular concretion is formed are well
known. It is therefore easy to compare other concretions, which may have
some superficial resemblance to these stalactical bodies, in order to
see if they have proceeded upon the same principle of concretion from
a dissolved state, or by water depositing its dissolved substance in a
similar manner.
There are two different mineral substances which give appearances of
this sort. These are certain concretions of calcedony, and also of
iron-ore, which are thought to have such resemblance to stalactical
concretions as, by some superficial observers, to be reckoned of the
same kind. It is now proposed to show that those conclusions are not
well founded; and that, in this case of calcedony and iron-ore, it could
not be upon the principle of stalactical concretion that the bodies now
in question had their forms.
The principle upon which calcareous substance is dissolved in water, and
made to concrete by the evaporation of the acid substance, or fixed
air by which it had been dissolved, is too well known to require any
explanation in this place; we are only to consider the sensible effects
of those operations of which we know so well the proper conditions.
There are just two distinct views under which we may consider all
stalactical concretions formed; these are the incrustation of
the calcareous substance concreting upon a foreign body, and the
incrustation of the same substance upon itself. By the first any manner
of shape may be formed, provided there be a solid body, upon the surface
of which the calcareous solution is made to pass. By the second, again,
we have various forms; but we know the principles upon which they had
been made. These are the shape and motions of the fluid which gives the
calcareous concretion. Now, these principles are always to be perceived,
more or less, in all the bizarre or fantastical, as well as regular
shapes which are produced by stalactical concretions. At present, we
shall confine our views to one particular shape, which is simple,
regular, and perfectly understood wherever it is formed.
Drops of water falling from a roof, and forming stalactite, produce
first tubular bodies, and then gradually consolidate and increase those
pendulous bodies by incrustation. These appearances are thought to be
observed in the calcedony and ferruginous concretions, which has led
some mineralists to conclude, that those concretions had been formed
in the same manner, by means of water. We are now to show that these
mineral appearances are not analogous to stalactites in their formation,
and that they have evidently been formed in a different manner.
It must be evident, that, in the formation of those pendulous bodies,
each distinct stalactite must be formed by a separate drop of water;
consequently, that no more stalactites can be formed in a given space,
than there could have subsisted separate drops of water. Now, a drop of
water is a very determined thing; and thus we have a principle by which
to judge of those mistaken appearances.
Let us suppose the gut of water to be but one eighth of an inch,
although it is a great deal more, we should have no stalactites formed
nearer to each other than that measure of space. But those mineral
concretions, which are supposed to be stalactical, are contained in half
that space, or are nearer to each other than the tenth or twentieth of
an inch. I have them like needles, and in every degree of proximity or
contiguity, at the same time that they are perfectly solid. Therefore,
it is plainly impossible that they could have been formed upon this
principle of calcareous stalactite. But, it is only by this false
resemblance, that any argument can be formed for the concretion of those
bodies from an aqueous solution; in every other respect they are true
mineral concretions; and, that these have had a very different origin,
has been already the subject of investigation, and will be more
particularly examined in the course of this work.
The term _infiltration_, which has been much employed for explaining
mineral appearances, is too vague, imperfect, or unexplicit, for
science, whether as the means of knowing nature, or the subject of
confutation. This is not the case with that of stalactite; here is
a term that implies a certain natural operation, or a most distinct
process for attaining a certain end; and we know the principles upon
which it proceeds, as well as the several steps that may be traced in
the general result. It is an operation which has not only been analysed
to its principles; it is also a process which is performed by man,
proceeding on his acquired knowledge. Now, were this operation common to
the mineral regions, as it is proper to the surface of this earth; we
could not remain in any degree of suspense with regard to the origin of
those mineral bodies; for, having the true clue of knowledge, we should
be able to unravel the most intricate and mysterious appearance. But, so
far from this being the case, the more we come to inquire into nature,
and employ this principle, the less we find it applicable, and the more
involved in darkness is our science.
The places where these false appearances of stalactite are found, are
precisely those in which, from the nature of things, all possibility for
such an operation is excluded. For, How can this take place within a
closs cavity in the mineral regions? The term _vegetation_ may as well
be employed for the explanation of those appearances: But what would
now be said of such an explication? It is high time that science were
properly applied to the natural history of this earth, and mineralists
not allowed to impose upon themselves with false reasoning, or to please
themselves with the vain attempt of explaining visible effects by
unknown causes.
Such various inconsistent opinions, respecting petrifaction or mineral
concretion, as I have now exposed, opinions that are not founded on any
sound physical principle, authorise me to conclude that they are all
erroneous. If this be admitted, it will follow that we have no proof
of any proper mineral concretion except that which had proceeded by
congelation from the fluid state of fusion. This has been the doctrine
which I have held out in my Theory of the Earth; and this will be more
and more confirmed as we come to examine particular mineral appearances.
CHAP. VIII.
The Nature of Mineral Coal, and the Formation of Bituminous Strata,
investigated.
SECT. I.--Purpose of this Inquiry.
In the first chapter, I have given a perfect mark by which to judge,
of every consolidated stratum, how far that had been the operation or
effect of water alone, or if it had been that of heat and fusion. This
is the particular veins or divisions of the consolidated stratum,
arising from the contraction of the mass, distended by heat, and
contracted in cooling. It is not an argument of greater or lesser
probability; it is a physical demonstration; but, so far as I see, it
would appear to be for most mineralists an unintelligible proposition.
Time, however, will open the eyes of men; science will some day find
admittance into the cabinet of the curious. I will therefore now give
another proof,--not of the consolidation of mineral bodies by means
of fusion, for there is no mineral body in which that proof is not
found,--but of the inconsistency of aqueous infiltration with the
appearances of bodies, where not only fusion had been employed for the
consolidation, but where the application of heat is necessary, and along
with it the circumstances proper for _distillation_.
Short-sighted naturalists see springs of water issuing from the earth,
one forming calcareous incrustations, the other depositing bituminous
substances. Here is enough for them to make the theory of a world; on
the one hand, solid marble is explained, on the other, solid coal.
Ignorance suspects not error; their first step is to reason upon a false
principle;--no matter, were they only to reason far enough, they would
soon find their error by the absurdity into which it lands them. The
misfortune is, they reason no farther; they have explained mineralogy
by infiltration; and they content themselves with viewing the beautiful
specimens in their cabinet, the supposed product of solution and
crystalization. How shall we inform such observators; How reason with
those who attend not to an argument!
As naturalists have explained all mineral concretions from aqueous or
other solution, and attributed to infiltration the formation of those
stony bodies in which there are marks of their original composition,
so have they explained to themselves, I suppose, the origin of those
bituminous bodies which are found among the strata of the earth. In the
case of stony substances, I have shown how unfounded all their theories
are for the production of those concretions, crystallizations, and
consolidated bodies. I am here to examine the subject of inflammable and
combustible bodies, which I believe have been little considered by those
theorists who suppose mineral bodies consolidated by infiltration. It is
here that we shall find an infinite difference between the aqueous and
igneous theories; for, we shall find it impossible to explain by the one
certain operations which must have necessarily required the great agent
generally employed in the other.
The subject of this chapter is a touch-stone for every theory of the
earth. In every quarter of this globe, perhaps in every extensive
country, bituminous strata are to be found; they are alternated with
those which are called aquiform, or which had been evidently formed by
subsidence of certain moved materials at the bottom of the sea; so far,
therefore, all those strata have had the same origin. In this point
I think I may assert, that all the different theories at present are
agreed; and it is only concerning certain transformations of those
strata, since their original collection, that have been ascribed to
different causes.
Of these transformations, which the strata must have undergone, there
are two kinds; one in relation to change of place and position; the
other in relation to solidity or consistence. It is only the last of
those two changes which is here to be the subject of consideration;
because, with regard to the first, there is nothing peculiar in these
bituminous strata to throw any light, in that respect, upon the others.
This is not the case with regard to the transformation in their chemical
character and consistence; bituminous bodies may not be affected by
chemical agents, such as fire and water, in the same manner as the
argillaceous, siliceous, micaceous, and such other strata that are
alternated with the bituminous; and thus we may find the means for
investigating the nature of that agent by which those strata in general
have been transformed in their substance; or we may find means for the
detecting of false theories which may have been formed with regard
to those operations in which the original deposits of water had been
changed.
We have had but two theories, with regard to the transformation of
those bodies which have had a known origin, or to the change of their
substance and consistence; the one of these which I have given is that
of heat or fusion; the other, which I wish to be compared with mine,
is that of water and infiltration. It is by this last that all authors
hitherto, in one shape or another, have endeavoured to explain the
changes that those strata must have undergone since the time of their
first formation at the bottom of the sea. They indiscriminately apply
the doctrine of infiltration to those strata of mineral coal as to any
other; they say that bituminous matter is infiltrated with the water,
impregnates certain strata of earth with bituminous matter, and thus
converts them into mineral coal, and bituminous strata. This is not
reasoning physically, or by the inductive method of proceeding upon
matter of fact; it is reasoning fantastically, or by making gratuitous
supposition founded merely on imagination. It was thus that natural
philosophers reasoned before the age of science; the wonder now is,
how men of science, in the present enlightened age, should suffer such
language of ignorance and credulity to pass uncensured.
The subject which I am now to treat of consists of peculiar strata of
the earth, bodies which we may investigate through all the stages of
their change, which is extreme; for, from vegetable bodies produced upon
the habitable earth, they are now become a mineral body, and the most
perfect coal,--a thing extremely different from what it had been, and
a thing which cannot be supposed to have been accomplished by the
operation of water alone, or any other agent in nature with which we
are acquainted, except the action of fire or heat. It is therefore
impossible for a philosopher, reasoning upon actual physical principles,
not to acknowledge in this a complete proof of the theory which has been
given, and a complete refutation of that aqueous operation which has
been so inconsiderately supposed as consolidating the strata of the
earth, and forming the various mineral concretions which are found in
that great body.
To see this, it will be sufficient to trace the progress of vegetable
and animal substances, (bodies which had certainly lived by means of a
former earth), to this changed state in which they have become perfect
mineral bodies, and constitute a part of the present earth. For, as
these changes are perfectly explained by the one theory, and absolutely
inconsistent with the other, there arises from this a conviction that
must be irresistible to a person who can give proper attention to a
chain of reasoning from effect to cause.
But if we thus succeed to illustrate the theory of the earth by the
natural history of those particular strata, we have but one step farther
to make in order to bring all the other parts of the earth, whether
stratified or not, into the most perfect consistence with the theory;
now this step, it will be most easy to make; and I shall now mention
it, that so the reader may keep it in his view: Pyrites is a
sulphureo-metallic substance, which cannot be produced by means of
water, a substance which the influences of the atmosphere decomposes or
separates into its elements, and which even our imperfect art may
be considered as able to produce, by means of fusion in our fires.
Therefore, the finding of this creature of fire intimately connected
with those consolidated strata of mineral coal, adds the greatest
confirmation, were it necessary, to the doctrine of those mineral bodies
having been consolidated by fusion. This confirmation, however, is
not necessary, and it is not the only thing which I am at present to
illustrate in that doctrine. What I have now in view is, to homologate
the origin of those coal strata, with the production of every other
mineral substance, by heat or fusion; and this is what the intimate
connection of pyrites with those strata will certainly accomplish. This
will be done in the following manner:
Pyrites is not only found in great masses along with the coal strata; it
is contained in the veins which traverse those strata, and in the minute
ramifications of those veins, which are occasioned by the contraction of
the mass, and generally divide it into small cubical pieces; but besides
that extrinsic connection, (as it may be called,) with the stratum of
coal, pyrites is found intimately connected with that solid body, in
being mixed with its substance. If, therefore, it were proved, that
either the one or other of those two substances had been consolidated by
fusion, the other must be acknowledged as having had the same origin;
but now I am to prove, from the natural history of mineral coal, that
pyrites had been there formed by fusion; and then, by means of the
known origin of that sulphureo-metallic substance, we shall extend our
knowledge to the origin of every other mineral body.
The process of this argument is as follows: Every mineral body, I
believe, without exception, will be found so intimately connected with
pyrites, that these two things must be concluded as having been together
in a fluid state, and that, whatever may have been the cause of fluidity
in the one, this must have also caused the fluidity in the other;
consequently, whatever shall be proved with regard to the mineral
operations of pyrites, must be considered as proved of every other
mineral substance. But, from the connection of pyrites with mineral
coal, it is to be proved that the origin of this metallic body had been
fusion; and then it will appear, that all other mineral bodies must have
been more or less in fusion, or that they must have been consolidated
by means of heat, and not by any manner of solution or aqueous
infiltration. I therefore now proceed to take a view of the natural
history of coal strata,--a subject which mineralogists seem not inclined
to engage with, although the most ample data are to be found for that
investigation.
SECT. II.--Natural History of Coal Strata, and Theory of this
Geological Operation.
Fossil coal is the species of stratum best understood with regard to its
accidents, as being much sought after; at least, this is the case in
many parts of Britain, where it supplies the place of wood for burning.
This fossil body has the most distinguished character; for, being
inflammable or combustible in its nature, there is no other species of
stratum that may be confounded with it.
But, though coal be thus the most distinguishable mineral, and that
which is best understood in the science of mining, it is perhaps the
most difficult to be treated of in the science of mineralogy; for,
not having properly any distinguishable parts, we have nothing in the
natural constitution of this body, as we have in most other strata, to
lead us to the knowledge of its original state or first formation.
The varieties of coal are distinguished by their different manner of
burning; but, from appearances of this kind, no perfect judgement can be
formed with regard to the specific manner in which those strata had been
made; although, from chemical principles, some conclusion may be drawn
concerning certain changes which they have undergone since they had been
formed.
Thus we have one species of coal which is extremely fusible, abounds
with oil, and consequently is inflammable; we have another species again
which is perfectly fixed and infusible in the fire; therefore, we may
conclude upon principle, that, however, both those coals must have
undergone the operation of heat and fusion, in bringing them to their
present state, it is only the last that has become so much evaporated as
to become perfectly fixed, or so perfectly distilled, as to have been
reduced to a caput mortuum.
The argument here employed is founded upon this fact; that, from the
fusible species of coal, a caput mortuum may be formed by distillation,
and that this chemical production has every essential quality, or every
peculiar property, of the fixed and infusible species; although, from
the circumstances of our operation, this caput mortuum may not have
precisely the exterior appearance of the natural coal. But, we have
reason to believe, it is not in the nature of things to change the
infusible species, so as to make it fusible or oily. Now, that this body
was not formed originally in its present state, must appear from this,
that the stratum here considered is perfectly solid; but, without
fusion, this could not have been attained; and the coal is now supposed
to be infusible. Consequently, this fixed substance, which is now,
properly speaking, a perfect coal, had been originally an oily
bituminous or fusible substance. It is now a fixed substance, and an
infusible coal; therefore, it must have been by means of heat and
distillation that it had been changed, from the original state in which
this stratum had been formed.
We have thus, in the examination of coal strata upon chemical
principles, received a certain lesson in geology, although this does not
form a proper distinction by which to specify those strata in general,
or explain the variety of that mineral. For, in this manner, we
could only distinguish properly two species of those strata; the one
bituminous or inflammable; the other proper coal, burning without smoke
or flame. Thus it will appear that, as this quality of being perfectly
charred is not originally in the constitution of the stratum, but an
accident to which some strata of every species may have been subjected,
we could not class them by this property without confounding together
strata which had differences in their composition or formation.
Therefore, we are led to inquire after some other distinction, which may
be general to strata of fossil coal, independent of those changes which
this substance may have undergone after it had been formed in a stratum.
Perfect mineral coal being a body of undistinguishable parts, it is only
in its resolution that we may analyse it, and this is done by burning.
Thus, in analysing coal by burning, we have, in the ashes alone, that by
which one species of coal may be distinguished from another; and, if we
should consider pure coal as having no ashes of itself, we should then,
in the weight of its ashes, have a measure of the purity of the coal,
this being inversely as the quantity of the ashes. Now, though this be
not accurately true, as the purest coal must have some ashes proper to
itself, yet, as this is a small matter compared with the quantity of
earthy matter that may be left in burning some species of coal, this
method of analysis may be considered as not far removed from the truth.
But, in distinguishing fossil coal by this species of chemical analysis,
not only is there to be found a perfect or indefinite gradation from a
body which is perfectly combustible to one that is hardly combustible in
any sensible degree, we should also fall into an inconveniency similar
to that already mentioned, of confounding two things extremely different
in their nature, a bituminous body, and a perfect charcoal. Thus, if we
shall found our distinction upon the fusibility and different degree of
having been charred, we shall confound fossil coals of very different
degrees of value in burning, or of very different compositions as
strata; if, again, we found it upon the purity of composition, in
judging from the ashes, we shall confound fossil bodies of very
different qualities, the one burning with much smoke and flame, the
other without any; the one fusible almost like wax, the other fixed and
infusible as charcoal.
It will now appear, that what cannot be done in either the one or other
of those two methods, may in a great degree, or with considerable
propriety, be performed in employing both.
Thus, whether for the economical purposes of life, or the natural
history of fossil coal, those strata should be considered both with
regard to the purity of their composition as inflammable matter
deposited at the bottom of the sea, and to the changes which they
have afterwards undergone by the operation of subterranean heat and
distillation.
We have now considered the original matter of which coal strata are
composed to be of two kinds; the one pure bitumen or coal, as being
perfectly inflammable or combustible; the other an earthy matter,
with which proper coal may be variously mixed in its composition, or
intimately connected, in subsiding from that suspended state by which it
had been carried in the ocean. It is a matter of great importance, in
the physiology of this globe, to know that the proper substance of coal
may be thus mixed with heterogeneous bodies; for, supposing that this
earthy matter, which has subsided in the water along with coal, be no
farther connected with the combustible substance of those strata, than
that it had floated in the waters of the ocean, and subsided _pari
passu_ with the proper materials of the coal, we hence learn a great
deal with regard to the state in which the inflammable matter must have
been at the time of its formation into strata. This will appear by
considering, that we find schistus mixed with coal in the most equal or
uniform manner, and in almost every conceivable degree, from the purest
coal to the most perfect schistus. Hence we have reason to conclude,
that, at the formation of those strata, the bituminous matter, highly
subtilised, had been uniformly mixed with the earth subsiding in the
water.
Not only is the bituminous matter of coal found mixed in every different
proportion with the earthy or uninflammable materials of strata, but the
coaly or bituminous composition is found with perhaps every different
species of substance belonging to strata. This is certain, that we have
the coaly matter intimately mixed with argillaceous and with calcareous
strata.
Thus it will appear, that it is no proper explanation of the formation
of coal strata, to say that vegetable matter is the basis of those
strata; for though, in vegetation, a substance proper for the formation
of bituminous matter is produced, it remains to know by what means, from
a vegetable body, this bituminous matter is produced, and how it comes
to be diffused in that subtile state by which it may be uniformly mixed
with the most impalpable earth in water. Could we once resolve this
question, every other appearance might be easily explained. Let us
therefore now endeavour to discover a principle for the resolving of
this problem.
There are two ways in which vegetable bodies may be, in part at least,
resolved into that subtilised state of bituminous matter after which we
inquire; the one of these is by means of fire, the other by water. We
shall now consider these severally as the means of forming bituminous
strata, although they may be both employed by nature in this work.
When vegetable bodies are made to burn, there is always more or less of
a fuliginous substance formed; but this fuliginous substance is no
other than a bituminous body in that subtilised state in which it is
indefinitely divided, and may be mixed uniformly with any mass of matter
equally subtilised with itself. But this is precisely what we want, in
order to compose the strata of coal in question. If, therefore, there
were to be found in the ocean such a fund of this fuliginous substance
as might suffice for the formation of bituminous strata, no difficulty
would be left in explaining the original of fossil coal. But tho'
sufficient quantity of this fuliginous matter might not be found for the
explanation of natural appearances, yet there cannot be a doubt that
more or less of this matter must be produced in the mineral operations
of the globe, and be found precisely in that place where it is required
for the forming of those strata of coal.
In order to conceive this, we are to consider, that there are actually
great quantities of coal strata in a charred state, which indicates
that all their more volatile oleaginous or fuliginous matter had been
separated by force of subterranean heat; and, we are to suppose that
this had been transacted at the bottom of the ocean: Consequently, a
subtile oleaginous, bituminous, or fuliginous substance, must have been
diffused in that ocean; and this bituminous matter would be employed in
forming other strata, which were then deposited at the bottom of the
waters.
But besides this quantity of bituminous matter which is necessarily
formed in the mineral operations of the earth, and with regard to the
quantity of which we can never form a proper estimate, there must enter
into this same calculation all the fuliginous matter that is formed in
burning bodies upon the surface of this earth. This bituminous matter of
smoke is first delivered into the atmosphere, but ultimately it must
be settled at the bottom of the sea. Hence though, compared with the
quantity that we think required, each revolution of the globe produces
but a little in our estimation, yet the progress of time, in reforming
worlds, may produce all that is necessary in the formation of our
strata.
There now remains to explain the other way in which bituminous matter
may be obtained from vegetable bodies, that is, by means of water. For
this purpose we must begin with a part of natural history that will
throw some light upon the subject.
All the rivers in Scotland run into the sea tinged with a brown
substance; this is most evident in some of them after a flood, and while
yet the river is swelled; but, in travelling to the north of Scotland
in the summer season, without any rain, I saw all the rivers, without
exception, of a brown colour, compared with a river of more clear water.
This colour proceeds from the moss water, as it is called, which runs
into the rivers, or the infusion of that vegetable substance which
forms combustible turf, called peat. Now, this moss water leaves, upon
evaporation, a bituminous substance, which very much resembles fossil
coal. Therefore, in order to employ this vegetable infusion, delivered
into the ocean for the purpose of forming bituminous strata at its
bottom, it is only required to make this bituminous matter separate and
subside.
If now we consider the immense quantity of inflammable vegetable
substance, dissolved in water, that is carried into the sea by all the
rivers of the earth, and the indefinite space of time during which those
rivers have been pouring in that oily matter into the sea; and if we
consider, that the continual action of the sun and atmosphere upon this
oily substance tends, by inspissation, to make it more and more dense or
bituminous, we cannot hesitate in supposing a continual separation
of this bituminous matter or inspissated oil from the water, and
a precipitation of it to the bottom of the sea. This argument is
corroborated by considering, that, if it were otherwise, the water of
the sea must have, during the immense time that rivers are proved
to have run, be strongly impregnated with that oily or bituminous
substance; but this does not appear; therefore we are to conclude, that
there must be the means of separating that substance from the water in
which it had been dissolved.
If there is thus, from the continual perishing of animal and vegetable
bodies upon the surface of this earth and in the sea, a certain supply
of oily or bituminous matter given to the ocean, then, however small a
portion of this shall be supposed the whole oily or inflammable matter
produced upon the surface of the earth, or however long time it may
require for thus producing a stratum or considerable body of coal,
we must still see in this a source of the materials proper for the
production of that species of strata in the bottom of the sea.
We have now considered the proper materials of which pure fossil coal
is chiefly formed; we have at present to consider what should be the
appearances of such a substance as this collected at the bottom of the
sea, and condensed or consolidated by compression and by heat. We should
thus have a body of a most uniform structure, black, breaking with a
polished surface, and more or less fusible in the fire, or burning with
more or less smoke and flame, in proportion as it should be distilled
or inspissated, less or more, by subterranean heat. But this is the
description of our purest fossil coals, which burn in giving the
greatest quantity of heat, and leave the smallest quantity of ashes.
In order to form another regular species of coal, let us suppose that,
along with the bituminous substance now considered, there shall be
floating in the water of the ocean a subtile earthy substance, and that
these two different substances shall subside together in an uniform
manner, to produce a stratum which shall be covered with immense weight,
compressed, condensed, and consolidated as before, we should thus have
produced a most homogeneous or uniform body to appearance, but not so
in reality. The mixture of heterogeneous matter, in this case, is too
minute to be discovered simply by inspection; it must require deep
reflection upon the subject, with the help of chemical analysis,
to understand the constitution of this body, and judge of all the
circumstances or particulars in which it differs from the former. It is
worth while to examine this subject with some attention, as it will give
the most instructive view of the composition of bituminous strata, both
those which are not considered as coal, and also the different species
of that mineral body.
In the first place then, if the mixture of those two different
substances had been sufficiently perfect, and the precipitation uniform,
the solid body of coal resulting from this mixture, would not only
appear homogeneous, but might break equally or regularly in all
directions; but the fracture of this coal must visibly differ from the
former, so far as the fracture of this heterogeneous coal cannot have
the polished surface of the pure bituminous body; for, the earthy matter
that is interposed among the bituminous particles must affect the
fracture in preventing its surface from being perfectly smooth. This
imperfect plane of the fracture may be improved by polishing; in which
case the body might be sufficiently smooth to have an agreeable polish;
but it cannot have a perfect polish like a homogeneous body, or appear
with that glassy surface which is naturally in the fracture of the pure
bituminous coal.
But this is also a perfect description of that species of coal which is
called in England Kennel coal, and in Scotland Parrot coal. It is so
uniform in its substance that it is capable of being formed on the
turning loom; and it receives a certain degree of polish, resembling
bodies of jet.
Thus, we have a species of coal in which we shall find but a small
degree of fusibility, although it may not be charred in any degree.
Such an infusible coal may therefore contain a great deal of aqueous
substance, and volatile oily matter; consequently may burn with smoke
and flame. But this same species of coal may also occasionally be
charred more or less by the operation of subterranean heat; and, in
that case, we should have a variety of coal which could only be
distinguished, from a similar state of pure bituminous coal, by the
ashes which they leave in burning. At least, this must be the case, when
both species are, by sufficient distillation, reduced to the state of
what may be properly termed a chemical coal.
But in the natural state of its composition, we find those strata of
kennel or parrot coal, possessing a peculiar property, which deserves to
be considered, as still throwing more light upon the subject.
We have been representing these strata of coal as homogeneous to
appearance, and as breaking indifferently in all directions; this last,
perhaps, is not so accurate; for they would seem to break chiefly into
two directions, that is, either parallel or perpendicular to the bed.
Thus we have this coal commonly in rectangular pieces, in which it
is extremely difficult to distinguish the direction of the bed, or
stratification of the mass. By an expert eye, however, this may be in
general, or at least sometimes, distinguished, and then, by knowing
the habit of the coal in burning, a person perfectly ignorant of the
philosophy of the matter may exhibit a wonderful sagacity, or even of
power over future events, in applying this body to fire; for, at his
pleasure, and unknown to those who are not in the secret; he may
apparently, in equal circumstances, make this coal either kindle
quietly, or with violent cracking and explosions, throwing its splinters
at a distance.
The explanation lies in this, that, though the rectangular mass of coal
appears extremely uniform in its structure, it is truly a stratified
mass; it is therefore affected, by the sudden approach of fire in a very
different manner, according as the edge of the stratum, which is seen in
four of the sides of this supposed cube, shall be applied to the fire,
or the other two sides, which are in the line of the stratum, or
parallel to the bed of coal. The reason of this phenomenon now remains
to be considered.
When the edge of the coal is exposed to the fire, the stratification of
the coal is opened gradually by the heat and expanding vapours, as a
piece of wood, of a similar shape, would be by means of wedges placed in
the end way of the timber. The coal then kindles quietly, and quickly
flames, while the mass of this bituminous schistus is opening like the
leaves of a book, and thus exhibits an appearance in burning extremely
like wood. But let the fire be applied to the middle of the bed, instead
of the edge of the leaves, and we shall see a very different appearance;
for here the expanded aqueous vapours, confined between the _laminae_,
form explosions, in throwing off splinters from the kindling mass; and
this mass of coal takes fire with much noise and disturbance.
The ashes of this coal may be determined as to quality, being in general
a subtile white earth; but, as to quantity, the measure of that earth
produces an indefinite variety in this species of coal; for, from the
kennel or parrot coal, which is valuable for its burning with much
flame, to that black schistus which our masons use in drawing upon
stone, and which, though combustible in some degree, is not thought to
be a coal, there is a perfect gradation, in which coal may be found with
every proportion of this earthy alloy.
Among the lowest species of this combustible schistus are those
argillaceous strata in Yorkshire from whence they procure alum in
burning great heaps of this stone, which also contains sulphur, to
impregnate the aluminous earth with its acid. We have also, in this
country, strata which differ from those aluminous schisti only in the
nature of the earth, with which the bituminous sediment is mixed. In
the strata now considered, the earth, precipitated with the bituminous
matter, being calcareous, has produced a limestone, which, after burning
especially, is perfectly fissile.
Therefore, with regard to the composition of mineral coal, the theory
is this. That inflammable, vegetable, and animal substances, in a
subtilised state, had subsided in the sea, being mixed more or less with
argillaceous, calcareous, and other earthy substances in an impalpable
state. Now, the chemical analysis of fossil coal justifies that theory;
for, in the distillation of the inflammable or oily coal, we procure
volatile alkali, as might be naturally expected.
Thus we have considered fossil coal as various, both in its state and
composition; we have described coal which is of the purest composition,
as well as that which is most impure or earthy; and we have shown that
there is a gradation, from the most bituminous state in which those
strata had been formed in being deposited at the bottom of the sea,
to the most perfect state of a chemical coal, to which they have been
brought by the operation of subterranean fire or heat.
We have been hitherto considering fossil coal as formed of the
impalpable parts of inflammable bodies, united together by pressure, and
made to approach in various degrees to the nature of a chemical coal,
by means of subterranean heat; because, from the examination of those
strata, many of them have evidently been formed in this manner.
But vegetable bodies macerated in water, and then consolidated by
compression, form a substance of the same kind, almost undistinguishable
from some species of fossil coal. We have an example of this in our turf
pits or peat mosses; when this vegetable substance has been compressed
under a great load of earth, which sometimes happens, it is much
consolidated, and hardens, by drying, into a black body, not afterwards
dilutable or penetrated by water, and almost undistinguishable in
burning from mineralised bodies of the same kind.
Also, when fossil wood has been condensed by compression and changed by
the operation of heat, as it is frequently found in argillaceous strata,
particularly in the aluminous rock upon the coast of Yorkshire, it
becomes a jet almost undistinguishable from some species of fossil coal.
There cannot therefore be a doubt, that if this vegetable substance,
which is formed by the collection of wood and plants in water upon the
surface of the earth, were to be found in the place of fossil coal, and
to undergo the mineral operations of the globe, it must at least augment
the quantity of those strata, though it should not form distinct strata
by itself.
It may perhaps be thought that vegetable bodies and their impalpable
parts are things too far distant in the scale of magnitude to be
supposed as subsiding together in the ocean; and this would certainly be
a just observation with regard to any other species of bodies: But the
nature of vegetable bodies is to be floatant in water; so that we may
suppose them carried at any distance from the shore; consequently, the
size of the body here makes no difference with regard to the place or
order in which these are to be deposited.
The examination of fossil coal fully confirms those reasonable
suppositions. For, _first_, The strata that attend coal, whether the
sandstone or the argillaceous strata, commonly, almost universally,
abound with the most distinct evidence of vegetable substances; this
is the impressions of plants which are found in their composition.
_Secondly_, There is much fossil coal, particularly that termed in
England clod coal, and employed in the iron foundry, that shows
abundance of vegetable bodies in its composition. The strata of this
coal have many horizontal interstices, at which the more solid shining
coal is easily separated; here the fibrous structure of the compressed
vegetable bodies is extremely visible; and thus no manner of doubt
remains, that at least a part of this coal had been composed of the
vegetable bodies themselves, whatever may have been the origin of the
more compact parts where nothing is to be distinguished.
The state in which we often find fossil wood in strata gives reason to
conclude that this body of vegetable production, in its condensed state,
is in appearance undistinguishable from fossil coal, and may be also in
great quantity; as, for example, the Bovey coal in Devonshire.
Thus the strata of fossil coal would appear to be formed by the
subsidence of inflammable matter of every species at the bottom of the
sea, in places distant from the shore, or where there had been much
repose, and where the lightest and most floatant bodies have been
deposited together. This is confirmed in examining those bodies of
fossil coal; for, though there are often found beds of sand-stone
immediately above and below the stratum of the coal, we do not find any
sand mixed in the strata of the coal itself.
Having found the composition of coal to be various, but all included
within certain rules which have been investigated, we may perceive in
this an explanation of that diversity which is often observed among the
various strata of one bed of coal. Even the most opposite species of
composition may be found in the thickness of one bed, although of very
little depth, that is to say, the purest bituminous coal may, in the
same bed, be conjoined with that which is most earthy.
Fossil coal is commonly alternated with regular sand-stone and
argillaceous strata; but these are very different bodies; therefore,
it may perhaps be inquired how such different substances came to be
deposited in the same place of the ocean. The answer to this is easy; we
do not pretend to trace things from their original to the place in which
they had been ultimately deposited at the bottom of the sea. It is
enough that we find the substance of which we treat delivered into
the sea, and regularly deposited at the bottom, after having been
transported by the currents of the ocean. Now the currents of the ocean,
however regular they may be for a certain period of time, and however
long this period may be protracted, naturally change; and then the
currents, which had given birth to one species of stratum in one place,
will carry it to another; and the sediment which the moment before
had formed a coal stratum, or a bed of that bituminous matter, may
be succeeded either with the sediment of an argillaceous stratum, or
covered over with a bed of sand, brought by the changed current of the
sea.
We have now considered all the appearances of coal strata, so far as
these depend upon the materials, and their original collection. But,
as those bituminous strata have been changed in their substance by the
operation of subterranean heat and inspissation, we are now to look for
the necessary consequences of this change in the body of the stratum;
and also for other mineral operations common to fossil coal with
consolidated strata of whatever species.
If coal, like other mineral strata, have been inspissated and
consolidated by subterranean heat, we should find them traversed with
veins and fissures; and, if the matter found in those veins and fissures
corresponds to that found in similar places of other strata, every
confirmation will be hence given to the theory that can be expected from
the consideration of those bituminous strata. But this is the case; we
find those fissures filled both with calcareous, gypseous, and pyritous
substances. Therefore, we have reason to conclude, that the strata of
fossil coal, like every other indurated or consolidated body in the
earth, has been produced, _first_, by means of water preparing and
collecting materials proper for the construction of land; and,
_secondly_, by the operation of internal fire or subterranean heat
melting and thus consolidating every known substance of the globe.
Not only are those sparry and pyritous substances, which are more
natural to coal strata, found forming veins traversing those strata in
various directions, but also every other mineral vein may occasionally
be found pervading coal mines, or traversing bituminous strata. Gold,
silver, copper, lead, calamine, have all, in this manner, been found in
coal.
There remains now only to consider those bituminous strata of fossil
coal in relation to that change of situation which has happened more
or less to every stratum which we examine; but which is so much better
known in those of coal, by having, from their great utility in the arts
of life, become a subject for mining, and thus been traced in the earth
at great expense, and for a long extent.
Coal strata, which had been originally in a horizontal position, are now
found sometimes standing in an erect posture, even almost perpendicular
to the plane in which they had been formed. Miners therefore distinguish
coal strata according as they deem them to approach to the one or other
of those two extremes, in terming them either flat or edge seams or
veins. Thus, it will appear, that every possible change from the
original position of those strata may have happened, and are daily found
from our experience in those mines.
But besides the changed position of those strata, in departing from the
horizontal line or flat position in which they had been formed, there is
another remarkable change, termed by miners a _trouble_ in the coal. The
consideration of this change will further illustrate the operations of
nature in placing that which had been at the bottom of the sea above its
surface.
Strata, that are in one place regularly inclined, may be found bended,
or irregularly inclined, in following their course. Here then is a
source of irregularity which often materially effects the estimates
of miners, judging from what they see, of those parts which are to be
explored; and this is an accident which they frequently experience.
But, without any change in the general direction of the stratum, miners
often find their coal broke off abruptly, those two parts being placed
upon a higher and lower situation in respect to each other, if flat
beds, or separated laterally if they are edge seams. This is by miners
termed a _slip, hitch_, or _dyke_.
These irregularities may either be attended with an injected body of
subterraneous lava or basaltes, here termed whin-stone, or they may not
be attended, at least apparently, _i.e._ immediately, with any such
accident. But experienced miners know, that, in approaching to any of
those injected masses of stone, which are so frequent in this country,
their coal is more and more subject to be troubled.
As there is, in this country of Scotland, two different species of
mountains or hills, one composed both in matter and manner exactly
similar to the Alps of Switzerland, the other of whin-stone, basaltic
rock, or subterraneous lava; and as the fossil coal, argillaceous and
sand-stone strata, are found variously connected with those hills,
nothing can tend more to give a proper understanding, with regard to the
construction of the land in general, of the globe than a view of those
different bodies, which are here found much mixed together in a little
space of country, thus exhibiting, as it were in miniature, what may be
found in other parts of the world, upon a larger scale, but not upon any
other principle. I will therefore endeavour to give a short description
of the mineral state of this country with regard to coal, so far as my
experience and memory will serve.
This country might very properly be considered as consisting of primary
and secondary mountains; not as supposing the primary mountains original
and inexplicable in their formation, any more than those of the latest
production, but as considering the one to be later in point of time, or
posterior in the progress of things. The first are those which commonly
form the alpine countries, consisting of various schisti, of quartzy
stone, and granites. The second, again, are the whinstone or basaltic
hills scattered up and down the low country, and evidently posterior to
the strata of that country, which they break, elevate, and displace.
Thus there are in this country, as well as every where else, three
things to be distinguished; first, the alpine or elevated country;
secondly, the flat or low country; and, thirdly, that which has been of
posterior formation to the strata which it traverses, in whatever shape
or quality; whether as a mountain, or only as a vein; whether as a
basaltes, a porphyry, or a granite, or only as a metal, a siliceous
substance, or a spar.
Those three things which are here distinguished do not differ with
regard to the chemical character of their substances; for, in each of
these, every different substance is to be found, more or less; and it
is not in being composed of materials peculiar to itself, that makes an
alpine country be distinguished from a flat country; it is chiefly in
the changes which the strata of the alpine country have been made to
undergo, posterior to their original collection, that the rocks of the
alpine country differ from those of the flat country.
But the observation that is most to the purpose of the present subject
of bituminous strata, is this; it is chiefly in the strata of the flat
country that fossil coal are found; there are none that I know of in
all the alpine countries of Scotland; and it is always among the strata
peculiar to the flat country that fossil coal is found. Now, this
appearance cannot be explained by saying that the materials of mineral
coal had not existed in the world while those primary strata were formed
in the sea. I have already shown, (chap. 4.) that there had been the
same system of a world, producing plants, and thus maintaining animals,
while the primary strata were formed in the sea; I have even adduced an
example of coal strata among those primary schisti, although this be an
extremely rare occurrence: Consequently, we are under the necessity of
looking out for some other cause.
If the changes which have been evidently superinduced in the strata of
alpine countries arise from the repeated operations of subterranean
fire, or to the extreme degree in which those strata have been affected
by this consolidating and elevating cause, it will be natural to suppose
that the bituminous or combustible part among those stratifications, may
have been mostly consumed upon some occasion during those various and
long continued operations; whereas, in the flat beds of the low country,
although there is the most perfect evidence for the exertion of heat in
the consolidation of those strata, the general quantity of this has been
a little thing, compared with the universal manifestation of this cause
in the operations of the alpine countries, the strata of which have been
so much displaced in their situations and positions.
To illustrate this, strata of sand-stone are found in both the alpine
and flat countries of Scotland. About Leadhills, for example, there are
abundance of those strata; but, in the flat country, the generality of
the sand-stone is so little changed as to appear to every enlightened
naturalist aquiform strata; whereas the most enlightened of those
philosophers will not perhaps attribute the same original to a similar
composition in the alpine country, which is so much changed from its
original state. It is not because there had been wanting a sufficient
degree of heat to consolidate the sand-stone in the coal country; for I
can show specimens of sand-stone almost contiguous with coal, that have
been extremely much consolidated in this manner. But this is only a
particular stratum; and the general appearance of the sand-stone, as
well as other strata in the coal countries, is that of having been
little affected by those subterranean operations of heat by which those
bodies in the alpine country have been changed in their structure,
shape, and position.
If we shall thus allow the principle of consolidation, consequently also
of induration, to have been much exerted upon the strata of the alpine
country, and but moderately or little upon those of the low country of
Scotland, we shall evidently see one reason, perhaps the only one, for
the lesser elevation of the one country above the level of the sea, than
the other. This is because the one resists the powers which have been
employed in leveling what has been raised from the bottom of the sea,
more than the other; consequently, we find more of the one remaining
above the level of the sea than of the other.
Let us now take the map of Scotland, in order to observe the mixture of
those two different species of countries, whereof the one is generally
low and flat, the other high and mountainous; the one more or less
provided with fossil coal, the other not.
From St Abb's Head, on the east of Scotland, to the Mull of Galloway,
on the west, there runs a ridge of mountains of granite, quartz, and
schistus strata, which contain not coal. On each side of this ridge we
find coal countries; Northumberland, on the one side, and, on the other,
the shires of Ayr, Lanark, and the Lothians; the one is a mountainous
country, the others are comparatively low or flat countries. Let us now
draw another alpine line from Buchan and Caithness, upon the east, to
the island of Jura, on the west; this traverses a mountainous country
destitute of coal, and, so far as I know, of any marks of marine bodies.
But, on each side of this great alpine ridge, we find the hard country
skirted with one which is lower, flatter, or of a softer nature,
in which coal is found, upon the one side, in the shires of Fife,
Clackmannan, and Stirling; and, on the other, in that hollow which runs
from the Murray Frith south-west, in a straight line, directed upon the
end of Mull, and composed, for the most part, of water very little above
the level of the sea. Here, to be sure, the coal is scarce, or not so
evident; but there is coal upon the sea coast in several places of this
great Bay betwixt Buchan and Caithness; and the lowness of the country,
across this part of the island, is almost sufficient testimony that it
had been composed of softer materials.
Thus the coal country of Scotland may be considered as in one band
across the island, and included in the counties of Ayr, Lanark, and all
those which border upon the Frith of Forth. Now, in all this tract of
coal and tender strata, we do not find ridges of alpine stone or primary
mountains, but we find many hills of solid rock, little mountains, from
500 to 1000 feet high; such as that beautiful conical hill North Berwick
Law, Torpender Law, Arthur's Seat, the Lowmands, and others of inferior
note. That is to say, the whole of this included space, both sea and
land, has been invaded from below with melted masses of whin-stone,
breaking up through the natural strata of the country, and variously
embossing the surface of the earth at present, when all the softer
materials, with which those subterranean lavas had been covered, are
washed away or removed from those summits of the country. Hence there is
scarcely a considerable tubercle, with which this country also abounds,
that may not be found containing a mass of whin-stone as a nucleus.
But besides those insulated masses of whinstone that form a gradation
from a mountain to a single rock, such, for example, as that on which
the Castle of Edinburgh is built, we find immense quantities of the same
basaltic rock interjected among the natural strata, always breaking and
disordering them, but often apparently following their directions for a
considerable space with some regularity. We also find dykes of the same
substance bisecting the strata like perpendicular veins of rock; and, in
some places, we see the connection of these rocks of the same substance,
which thus appear to be placed in such a different form in relation to
the strata.
It will thus appear, that the regular form, and horizontal direction of
strata throughout this country of coal, now under contemplation, has
been broken and disordered by the eruption and interjection of those
masses of basaltic stone or subterraneous lava; and thus may be
explained not only the disorders and irregularities of coal strata, but
also the different qualities of this bituminous substance from its
more natural state to that of a perfect coal or fixed infusible and
combustible substance burning without smoke. This happens sometimes to a
part of a coal stratum which approaches the whin-stone.
Having thus stated the case of combustible or bituminous strata, I would
ask those naturalists, who adhere to the theory of infiltration and the
operation of water alone, how they are to conceive those strata formed
and consolidated. They must consider, that here are immense bodies of
those combustible strata, under hundreds, perhaps thousands, of fathoms
of sand-stone, iron-stone, argillaceous and calcareous strata. If they
are to suppose bituminous bodies collected at the bottom of the sea,
they must say from whence that bitumen had come; for, with regard to the
strata below those bituminous bodies, above them, and between them,
we see perfectly from whence had come the materials of which they are
formed. They cannot say that it is from a collection of earthy matter
which had been afterwards bituminized by infiltration; for, although
we find many of those earthy strata variously impregnated with the
bituminous and coaly matter, I have shown that the earthy and the
bituminous matter had subsided together; besides, there are many of
those coaly and bituminous strata in which there is no more than two or
three _per cent._ of earthy matter or ashes after burning; therefore
the strata must have been formed of bituminous matter, and not simply
impregnated with it.
To avoid this difficulty, we shall allow them to form their strata,
which certainly is the case in great part, by the collection of
vegetable bodies; then, I desire them to say, in what manner they are
to consolidate those bodies. If they shall allege that it is by simple
pressure, How shall we conceive the numerous veins of spar and pyrites,
which traverse those strata in all directions, to be formed in
those bodies consolidated by the compression of the superincumbent
masses?--Here is a manifest inconsistency, which proves that it could
not be. But, even were we to suppose all those difficulties to be over
come, there is still an impossibility in the way of that inconsiderate
theory, and this will appear more fully in the following chapter.
SECT. III.--The Mineralogical Operations of the Earth illustrated from
the Theory of Fossil Coal.
There is not perhaps a greater difference among the various qualities of
bodies than that which may be observed to subsist between the burning of
those two substances, that is, the inflammable bodies on the one hand,
and those that are combustible on the other. I have treated of that
distinction in Dissertations upon subjects of Natural Philosophy, part
3d. where I have considered the different effects of those two kinds
of bodies upon the incident light; and, in a Dissertation upon the
Philosophy of Fire, etc. I have distinguished those two kinds of
substances in relation to their emitting, in burning, the fixed light
which had constituted a part of those inflammable and combustible
bodies.
All animals and vegetable bodies contain both those different chemical
substances united; and this phlogistic composition is an essential part
in every animal and vegetable substance. There are to be found in those
bodies particular substances, which abound more or less with one of
those species of phlogistic matter, but never is the one species of
those burning substances to be found naturally, in animal and vegetable
bodies, without being associated with the other; and it is all that the
chemical art can do to separate them in a great degree upon occasion.
Pure ardent spirit may perhaps be considered as containing the one, and
the most perfect coal the other; the chemical principle of the one
is proper carbonic matter; and of the other it is the hydrogeneous
principle, or that of inflammable air.
Thus we so far understand the composition of animal and vegetable
substances which burn or maintain our fires; we also understand the
chemical analysis of those bodies, in separating the inflammable from
the combustible substance, or the volatile from the fixed matter, the
oil from what is the proper coal. It is by distillation or evaporation,
the effect of heat, that this separatory operation is performed; and we
know no other means by which this may be done. Therefore, wherever we
find peculiar effects of that separatory operation, we have a right to
infer the proper cause.
The subject, which we are to consider in this section, is not the
composition of strata in those of mineral coal, but the transformation
of those, which had been originally inflammable bodies, into bodies
which are only combustible, an end which is to be attained by the
separation of their volatile or inflammable substances. In the last
section, I have shown of what materials the strata of mineral coal had
been originally formed; these are substances containing abundance of
inflammable oil or bitumen, as well as carbonic matter which is properly
combustible; and this is confirmed by the generality of those strata,
which, though perfectly consolidated by fusion, retain still their
inflammable and fusible qualities. But now the object of investigation
is that mineral operation by which some of those strata, or some parts
of a fusible and inflammable stratum, have been so changed as to become
infusible and only combustible.
We have now examined those strata which may be considered as either
proper mineral coal, or as only a bituminous schistus; we are now to
class along with these another species of this kind of matter, which has
had a similar origin, although it may assume a different character.
According to the common observations of mankind, the eminent quality by
which coal is to be distinguished, is the burning of that substance,
or its capacity for making a fire. Therefore, however similar in other
respects, a substance which had not that eminent quality of coal could
hardly be considered as being allied to it; far less could it be
supposed, as being in every other respect the same. We are however
to endeavour to show, that there are truly substances of this kind,
substances which to common observation, having none of the properties of
coal with respect to fire, consequently, no utility for the purpose of
burning, might be considered as another species of mineral, while at the
same time they are truly at bottom a composition very little different
from those which we have considered as the most perfect coal.
It must be recollected that we have distinguished coal in general as
of two different species, one perfect or proper coal, containing no
perceptible quantity of either oil or phlegm; the other as burning with
smoke and flame, consequently containing both aqueous and oleaginous
substances which it emits in distillation. It is the first of these
which we are now to consider more particularly, in order to see the
varieties which may be found in this species of mineral substance.
When that bituminous fossil, which is the common coal of this country,
is submitted to heat it is subject to melt more or less, and emits smoke
which is composed of water and oil. If it be thus completely distilled,
it becomes a perfect coal of a porous or spongy texture. Such a
substance as this is extremely rare among minerals; I have however found
it. It is in the harbour of Ayr, where a whinstone dyke traverses the
coal strata, and includes some of that substance in the state of coals
or cinder. I pointed this out many years ago to Dr Black; and lately I
showed it to Professor Playfair.
But the culm of South Wales, the Kilkenny coal of Ireland, and the blind
coal of Scotland, notwithstanding that these are a perfect coal, or
charred to a coal, have nothing of the porous construction of the
specimen which I have just now mentioned; they are perfectly solid, and
break with a smooth shining surface like those which emit smoke and
flame.
Here is therefore a mineral operation in the preparation of those coals
which we cannot imitate; and here is the clearest evidence of the
operation of mineral fire or heat, although we are ignorant of the
reason why some coal strata are charred, while others are not, and why,
in some particular cases, the charred coal may be porous or spongy like
our coals, while in general those blind coals (as they are called) are
perfectly solid in their structure.
But to what I would call more particularly the attention of mineral
philosophers is this, that it is inconceivable to have this effect
produced by means of water; we might as well say that heat were to be
the cause of ice. The production of coal from vegetable bodies, in which
that phlogistic substance is originally produced, or from animal bodies
which have it from that source, is made by heat, and by no other means,
so far as we know. But, even heat alone is not sufficient to effect that
end, or make a perfect coal; the phlogistic body, which is naturally
compound, consisting of both inflammable and combustible substances,
must be separated chemically, and this must be the operation of heat
under the proper circumstances for distillation or evaporation.
Here is the impossibility which in the last chapter I have alleged the
aqueous theory has to struggle against; and here is one of the absolute
proofs of the igneous theory. Not only must the aqueous part of those
natural phlogistic bodies be evaporated, in order to their becoming
coal, but the oily parts must also, by a still increased degree of heat,
be evaporated, or separated by distillation from the combustible part.
Here, therefore, is evidently the operation of heat, not simply that
of fusion in contradiction to the fluidity of aqueous solution, but
in opposition to any effect of water, as requiring the absence or
separation of that aqueous substance.
But those natural appearances go still farther to confirm our theory,
which, upon all occasions, considers the compression upon the bodies
that are submitted to the operation of heat, in the mineral regions, as
having the greatest efficacy in modifying that operation. Coal strata,
which are in the neighbourhood of each other, being of those two
opposite species, the one fusible and inflammable, the other infusible
and combustible, afford the clearest proof of the efficacy of
compression; for, it is evident, that the coal, which was once
bituminous or fusible, cannot be charred without the distillation of
that substance; therefore, prevent the distillation by compression and
the charring operation cannot proceed, whatever should be the intensity
of the heat; and then, fusion alone must be the effect upon the
bituminous body. But now, as we have both those species of coal in the
vicinity of each other, and even the same strata of coal part charred,
while the rest is not, this natural appearance, so far from being a
stumbling block, as it must be to the opposite theory, is most clearly
explained by the partial escape of vapours from the mineral regions, and
thus confirms the theory with regard to the efficacy of compression.
It is owing to the solidity of those natural charred coals, and the want
of oil, that they are so very difficult of kindling; but, when once
kindled in sufficient quantity, they make a fire which is very durable.
There are even some of them which, to common observation, seem to be
altogether incombustible. I have of this kind a specimen from a stratum
at Stair, which shall be afterwards mentioned.
M. Struve, in the Journal de Physique for January 1790, describes a
mineral which he calls _plombagine charbonneuse ou hexaëdre_; and gives
for reason, _parce qu'elle ressemble extrêmement au charbon de pierre
schisteux, ou d'hexaëdre_. He says farther, "Il est très commun, dans
une roche qui forme un passage entre les granits et les brèches, qu'on
n'a trouvée jusqu'a présent qu'on masses roulées dans le pays de Vaud."
He concludes his paper thus: "Ce fossile singulier ne paroît pas
appartenir à la Suisse seule. J'ai dans ce moment devant les yeux une
substance parfaitement semblable, si on excepte la couleur qui tient le
milieu entre le gris de fer et le rouge modéré; elle vient du pays de
Gotha de la Friedrischs-grube, proche d'Umneau. On le regarde comme un
eisenrahm uni à du charbon de pierre."
The specimen which I have from Stair upon the water of Ayr, so far as I
can understand, perfectly resembles this _plombagine_ of M. Struve. It
consumes very slowly in the fire, and deflagrates like plumbago with
nitre. Now this comes from a regular coal stratum; and what is more
remarkable, in this stratum is contained a true plumbago, Farther up the
country, the Earl of Dumfries has also a mine containing plumbago along
with other coal strata; and though the plumbago of these two mines have
not all the softness and beauty of the mineral of the same species from
Cumberland, they are nevertheless perfect plumbago.
I have a specimen of steatetical whinstone or basaltes from some part of
Cumberland, in which is contained many nodules of the most perfect and
beautiful plumbago. It is dispersed through this stone in rounded masses
of all sizes from a nut to a pin's head; and many of these are mixed
with pyrites. There is therefore reason to believe that this plumbago
had been in fusion.
Now, if we consider that every species of coal and every species of
plumbago are equally, that is, perfectly combustible, and yield, in
burning, the same volatile principles, differing only perhaps a little
in the small quantity of fixed matter which remains, we shall be
inclined to believe, that they have all the same origin in a vegetable
substance; and that they are diversified by some very small composition
of other matter. This being allowed, one thing is certain, that it is by
the operation of mineral fire or heat that those combustible substances,
however composed, have been brought to their present state of coal,
although we are ignorant of the circumstances by which their differences
and their peculiar chemical and mechanical qualities have been produced.
Let us resume in a few words. There is not perhaps one substance in the
mineral kingdom by which the operation of subterraneous heat is, to
common understanding, better exemplified than that of mineral coal.
Those strata are evidently a deposit of inflammable substances which all
come originally from vegetable bodies. In this state of their formation,
those coal strata must all be oleagenous or bituminous. In many of them,
however, these volatile parts are found wanting; and, the stratum is
found in the state of the most perfect coal or caput mortuum. There, is,
I presume, no other means to be found by which this eminent effect could
be produced, except by distillation; and, this distillation perhaps
proceeded under the restraining force of an immense compression.
To this theory it must not be objected, that all the strata of coal,
which are found in the same place or neighbourhood, are not reduced to
that caput mortuum or perfect coaly state. The change from a bituminous
to a coaly substance can only take place in proportion as the
distillation of the volatile parts is permitted. Now this distillation
must be permitted, if any passage can be procured from the inflammable
body submitted to the operation of subterraneous heat; and, one stratum
of coal may find vent for the passage of those vapours, through some
crevice which is not open to another. In this way, doubtless, some of
those bodies have been inspissated or reduced to a fixed coal, while
others, at a little distance, have retained most of their volatile
parts.
We cannot doubt of this distilling operation in the mineral regions,
when we consider that in most places of the earth we find the evident
effects of such distillation of oily substances in the naphta and
petroleum that are constantly emitted along with water in certain
springs. These oily substances are no other than such as may be
procured, in a similar manner, from the fusible or inflammable coal
strata; we have therefore every proof of this mineral operation that the
nature of things admit of. We have also sufficient evidence that those
fusible and inflammable coals, which have not been distilled to a caput
mortuum, had been subjected to the operation of subterraneous heat,
because we find those fusible coals subject to be injected with pyrites,
as well as the more perfect coal.
If we now consider those various appearances of mineral bodies which
are thus explained by the theory of mineral fire, or exertion of
subterraneous heat, appearances which it is impossible to reconcile by
any supposition of aqueous solution, or that unintelligible language
of mineral infiltration which has of late prevailed, we shall be fully
satisfied, that there is a uniform system in nature of providing a power
in the mineral regions, for consolidating the loose materials deposited
at the bottom of the sea, and for erecting those masses of mineralized
substances into the place of land; we shall thus be led to admire the
wisdom of nature, providing for the continuation of this living world,
and employing those very means by which, in a more partial view of
things, this beautiful structure of an inhabited earth seems to be
necessarily going into destruction.
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