Part 4

In our own times, men of still bolder imaginations have exercised their minds upon this great subject. Some writers have revived and greatly extended the ideas of Demaillet. They suppose that every thing was originally fluid; that this fluid gave existence to animals, which were at first of the most simple kind, such as the monads and other infusory and microscopic species; that, in process of time, and by assuming different habits, the races of animals became complicated, and assumed that diversity of nature and character in which they now appear. By means of those various races of animals, part of the waters of the sea have gradually been converted into calcareous earth; while the vegetables, concerning the origin and metamorphoses of which these writers are totally silent, have, on their part, converted a portion of the same water into clay: These two earths, on being stripped of the characters which life had impressed upon them, are resolved, by a final analysis, into silex; and hence the reason that the oldest mountains are more siliceous than the rest. All the solid parts of the earth, therefore, owe their existence to life, and, without life, the globe would still be entirely liquid[22].

Other writers have preferred the ideas of Kepler, and, like that great astronomer, have considered the globe itself as possessed of vital faculties. According to them a vital fluid circulates in it; a process of assimilation goes on in it, as well as in animated bodies; every particle of it is alive; it possesses instinct and volition, even to the most elementary molecules, which attract and repel each other according to sympathies and antipathies. Each kind of mineral has the power of converting immense masses into its own nature, as we convert our food into flesh and blood. The mountains are the respiratory organs of the globe, and the schists its organs of secretion; it is by these latter that it decomposes the water of the sea, in order to produce the matters ejected by volcanoes. The veins are carious sores, abscesses of the mineral kingdom; and the metals are products of rottenness and disease, which is the reason that almost all of them have so bad a smell[23].

More recently still, a philosophy, which substitutes metaphor for reasoning, and proceeds on the system of absolute identity or of pantheism, attributes the production of all phenomena, or which, in the eyes of its supporters, is the same thing, all beings, to polarization, such as is manifested by the two electricities; and denominating every kind of opposition or difference, whether of situation, of nature, or of function, by the title of Polarisation, opposes to each other, in the first place, God and the universe; then, in the universe, the sun and the planets; next, in each planet, the solid and the liquid; and, pursuing this course, changing its figures and allegories according to its necessities, at length arrives at the last details of organic species[24].

It must, however, be observed, that these are what may be termed extreme examples, and that all geologists have not carried the extravagance of their conceptions to such a length as those which we have just cited. Yet, among those who have proceeded with more caution, and have not searched for geological causes beyond the limits of physical and chemical science, much diversity and contradiction still prevail.

_Diversities of all the Systems._

According to one system, every thing has been successively precipitated by crystallization, and deposited nearly as it exists at present; but the sea, which covered all, has gradually retired[25].

According to another, the materials of which the mountains consist, are incessantly worn down and carried off by the rivers to be deposited at the bottom of the sea, where they are heated under an enormous pressure, and form strata, which are one day to be violently lifted up by the heat which consolidates them[26].

A third supposes the fluid divided into a multitude of lakes, placed, like the seats of an amphitheatre, above each other, which, after having deposited our shelly strata, have successively broken their dikes, to descend and fill the basin of the ocean[27].

According to a fourth, tides of seven or eight hundred fathoms depth have carried off, from time to time, the matter lying at the bottom of the sea, and have thrown it, in the form of mountains and hills, upon the original valleys or plains of the continent[28].

A fifth makes the various fragments of which the earth is composed, fall successively from heaven, in the manner of meteoric stones, bearing the impress of their foreign origin in the unknown beings whose remains they contain[29].

A sixth represents the globe as hollow, and places within it a loadstone nucleus, which is transported from one pole to the other, by the attraction of comets, carrying along with it the centre of gravity, and the mass of waters at the surface; thus alternately drowning the two hemispheres[30].

We might mention twenty other systems, as different from one another as those enumerated. And to prevent mistake, we may here state, that our intention is not captiously to criticize or find fault with their authors; on the contrary, we admit that these ideas have generally been conceived by men of intellect and knowledge, who were not ignorant of facts, several of whom had even travelled extensively for the purpose of examining them, and who, in this manner, made numerous and important additions to science.

_Causes of these differences._

Whence comes it, then, that there should be so much contrariety in the solutions of the same problem, that are given by men who proceed upon the same principles? May not this have been occasioned by the conditions of the problem never having been all taken into consideration at once; by which it has remained hitherto indeterminate, and susceptible of many solutions,--all equally good, when such or such conditions are abstracted; and all equally bad, when a new condition comes to be known, or when the attention is directed to some condition which had been formerly neglected?

_Nature and Conditions of the Problem._

To quit the language of mathematics, it may be asserted, that almost all the authors of these systems, confining their attention to certain difficulties which struck them more forcibly than others, have endeavoured to solve these in a manner more or less plausible, and have left unnoticed others, equally numerous, and equally important. For example, the only difficulty with one consisted in explaining the changes that had taken place in the level of the sea; with another, it consisted in accounting for the solution of all terrestrial substances in one and the same menstruum; and with a third, in shewing how animals that were believed to be natives of the torrid zone could live in the frigid zone. Exhausting all the powers of the mind upon these questions, they conceived that they had done every thing that was necessary when they had contrived some method of answering them; and yet, while they neglected all the other phenomena, they did not always think of determining with precision the measure and limits of those which they had endeavoured to explain.

This is peculiarly the case with regard to the secondary formations, which constitute, however, the most important and most difficult part of the problem. During a long time, all that was done with respect to these, consisted of feeble attempts to determine the order of superposition of their strata, and the connections of these strata with the species of animals and plants whose remains they contain.

Are there certain animals and plants peculiar to certain strata, and not found in others? What are the species that appear first in order, and what those which succeed? Do these two kinds of species sometimes accompany each other? Are there alternations in their appearance; or, in other words, do the first reappear a second time, and do the others then disappear? Have these animals and plants all lived in the places where their remains are found, or have they been transported thither from other places? Do they all live at the present day in some part of the earth, or have they been partially or totally destroyed? Is there any constant connection between the antiquity of the strata and the resemblance, or non-resemblance, of the fossils contained in them to the animals and plants which now exist? Is there any connexion, in regard to climate, between the fossils and such living beings as resemble them most? May it be concluded, that the transportation of these living beings, if such a thing ever happened, has taken place from north to south, or from east to west; or were they irregularly scattered and mingled together; and can the epochs of these transportations be determined by the characters which they have impressed upon the strata?

What can be said regarding the causes of the existing state of the globe, if no reply can be made to these questions,--if there be no sufficient grounds to determine the choice between answering in the affirmative or negative? It is but too true, that, for a long time, none of these points was satisfactorily determined; and scarcely even would geologists seem to have had any idea of the propriety of clearing them up before constructing their systems.

_Reason for which the Conditions of the Problem have been neglected._

The reason of this strange procedure will be discovered, when we reflect, that all geologists have hitherto been, either mere cabinet naturalists, who had themselves paid little attention to the structure of mountains, or mere mineralogists, who had not studied in sufficient detail the innumerable varieties of animals, and the infinite complication of their various parts. The former of these have only constructed systems: the latter have furnished excellent observations, and have laid the foundation of true geological science; but have been unable to complete the edifice.

_Progress of Mineral Geology._

The purely mineral part of the great problem of the Theory of the Earth has been investigated with admirable care by Saussure, and has been since carried to an astonishing degree of development by Werner, and by the numerous enlightened pupils of his school.

The former of these celebrated men, by a laborious investigation of the most inaccessible districts, continued for twenty years, in which he examined the Alps on all sides, and penetrated through all their defiles; has laid open to our view the entire disorder of the primitive formations, and has distinctly traced the limits by which they are distinguished from the secondary formations. The other, taking advantage of the numerous excavations made in the most ancient mining district in the world, has fixed the laws by which the succession of the strata are regulated, pointing out the relative antiquity of these strata, and tracing each of them through all its metamorphoses. It is from him, and from him alone, that we date the commencement of real geology, in so far as concerns the mineral nature of the strata: but neither he nor Saussure have determined the fossil organic species occurring in each kind of stratum, with the accuracy which has become necessary, now that the number of animals already known is so great.

Other naturalists, it is true, have examined the the fossil remains of organised bodies; they have collected and figured them by thousands, and their works will serve as so many precious collections of materials. But, considering these animals and plants more with reference to their own nature, than as connected with the theory of the earth; or regarding these petrifactions as curiosities, rather than as historical documents; or, lastly, contenting themselves with practical explanations regarding the position of each fragment, they have almost always neglected to investigate the general laws affecting the geological position of organic remains, or their connection with the strata.

_Importance of Fossil Remains in Geology._

And yet, the idea of such an investigation was very natural; for it is abundantly obvious, that it is to these fossil remains alone that we owe even the commencement of a theory of the earth, and that, without them, we should perhaps never have even suspected that there had existed any successive epochs, and a series of different operations, in the formation of the globe. By them alone we are, in fact, enabled to ascertain, that the globe has not always had the same external crust; because, we are thoroughly assured, that the plants and animals must have lived at the surface before they had thus come to be buried deep beneath it. It is only by analogy that we have been enabled to extend to the primitive formations, the conclusion which is furnished directly for the secondary by the organic remains which they contain; and if there had only existed formations in which no fossil remains were inclosed, it could never have been shewn that these formations had not all been of simultaneous origin.

It is also by means of the organic remains, slight as is the knowledge we have hitherto acquired of them, that we have been enabled to discover the little that we yet know respecting the nature of the revolutions of the globe. From them we have learned, that the strata in which they are buried have been quietly deposited in a fluid; that their variations have corresponded with those of the fluid in question; that their being laid bare has been occasioned by the transportation of this fluid to some other place; and that this circumstance must have befallen them more than once. Nothing of all this could have been known with certainty, had no fossil remains existed.

The study of the mineral part of geology, though not less necessary, and even of much more utility to the practical arts, is yet much less instructive with reference to the object of our present inquiry.

We remain in utter ignorance respecting the causes which have given rise to the variety in the mineral substances of which the strata are composed. We are even ignorant of the agents which may have held some of these substances in solution; and it is still disputed, respecting several of them, whether they have owed their origin to water or to fire. After all, philosophers are only agreed on one point, which is, that the sea has changed its place; and how should this have been known, unless by means of the fossil remains?

The organic remains, therefore, which have given rise to the theory of the earth, have, at the same time, furnished it with its principal illustrations;--the only ones, indeed, that have as yet been generally acknowledged.

It is this consideration which has encouraged us to investigate the subject. But the field is vast; and it is but a very small portion of it that could be cultivated by the labour of a single individual. It was necessary, therefore, to select a particular department; and the choice was soon made. The class of fossil remains which forms the subject of this work, engaged our attention at the very outset, because it appeared to us to be that which is the most fertile in precise results, and yet, at the same time, less known, and richer in new objects of research[31].

_High importance of the Fossil Bones of Quadrupeds._

It is obvious, in fact, that the fossil bones of quadrupeds must lead to more accurate conclusions than any other remains of organized bodies, and that for several reasons.

In the first place, they indicate much more clearly the nature of the revolutions to which they have already been subjected. Shells certainly announce the fact, that the sea has once existed in the places where they have been formed; but the changes which have taken place in their species, when rigorously inquired into, may have arisen from slight changes in the nature of the fluid in which they lived, or merely in its temperature. They may even have been produced by causes still more accidental. We can never be perfectly assured that certain species, and even genera, inhabiting the bottom of the sea, and occupying certain fixed spaces, for a longer or shorter time, may not have been driven away and supplanted by other species or genera.

In regard to quadrupeds, on the contrary, every thing is precise. The appearance of their bones in strata, and still more of their entire carcases, announces, either that the stratum itself which contains them has, at a former period, been laid dry, or, at least, that dry land must have existed in its neighbourhood. Their disappearance renders it certain, that this stratum has been inundated, or that the dry land in question has ceased to exist. It is from them, therefore, that we learn with perfect certainty the important fact of repeated irruptions of the sea, which the shells and other marine productions could not of themselves have proved; and it is by a careful investigation of them, that we may hope to ascertain the number and the epochs of these irruptions.

Secondly, The nature of the revolutions which have altered the surface of the globe, must have exerted a more powerful action upon terrestrial quadrupeds, than upon marine animals. As these revolutions have consisted chiefly of changes in the bed of the sea, and as the waters must have destroyed all the quadrupeds which they reached, if their irruption was general, it would necessarily have destroyed the entire class; or if it only overwhelmed certain continents at one time, it would at least have destroyed the species peculiar to those continents, without having the same effect upon the marine animals. On the other hand, millions of aquatic animals would have been left dry, or buried under newly-formed strata, or thrown violently on the coasts; while their races would still have been preserved in some more peaceful parts of the sea, whence they might again be propagated after the agitation of the waters had ceased.

Thirdly, This more complete action is also more easily ascertained. It is more easy to demonstrate its effects, because, the number of quadrupeds being limited, and the greater part of their species, at least the large ones, being known, we have more means of determining whether fossil bones belong to them, or to a species that is now lost. As, on the other hand, we are very far from being acquainted with all the testaceous animals and fishes which inhabit the sea, and as we are still probably ignorant of the greater number of those which live in deep water, it is impossible to know with certainty, whether a species which occurs in a fossil state, may not still exist somewhere alive. And hence, we see naturalists persisting in giving the name of pelagic shells, that is to say, shells inhabiting the open sea, to the belemnites, cornua-ammonis, and other testaceous remains, which have hitherto been found only in the older strata; meaning by this, that if they have not yet been discovered in a living state, it is because they inhabit the depths of the sea, far beyond the reach of our nets.

_Small probability of discovering New Species of large Quadrupeds._

Naturalists, certainly, have not yet explored all the continents, nor do they even know all the quadrupeds which inhabit the countries that they have explored. New species of this class are discovered from time to time; and those who have not examined with attention all the circumstances belonging to these discoveries, might also imagine that the unknown quadrupeds, whose bones are found in our strata, may remain to this day concealed, in some islands not yet discovered by navigators, or in some of the vast deserts which occupy the middle of Asia, Africa, the two Americas, and New Holland.

However, if we carefully examine what kinds of quadrupeds have been recently discovered, and in what circumstances they have been found, we shall see that there is little hope of our ever finding alive those which have hitherto been observed only in a fossil state.

Islands of moderate extent, and at a considerable distance from the continents or large islands, possess very few quadrupeds, and these, for the greater part, of diminutive size. When they happen to contain any of the larger species, these must have been carried to them from other countries. Bougainville and Cook found no other large quadrupeds than hogs and dogs in the South Sea Islands; and the largest species of the West India Islands was the _agouti_.

It is true that the great continents, such as Asia, Africa, the two Americas, and New Holland, possess large quadrupeds, and, generally speaking, contain species peculiar to each; insomuch, that whenever large countries of this description have been discovered, which their situation has kept isolated from the rest of the world, the class of quadrupeds which they contained has been found entirely different from any that existed elsewhere. Thus, when the Spaniards first penetrated into South America, they did not find a single species of quadruped the same as any of Europe, Asia, or Africa. The puma, the jaguar, the tapir, the cabiai, the llama, the vicuna, the sloths, the armadilloes, the opossums, and the whole tribe of sapajous, were to them entirely new animals, of which they had no idea. Similar circumstances have recurred in our own time, when the coasts of New Holland and the adjacent islands were first explored. The various species of kangaroo, phascolomys, dasyurus, and perameles, the flying phalangers, the ornithorynchi and echidnæ, have astonished naturalists by the strangeness of their conformations, which presented proportions contrary to all former rules, and were incapable of being arranged under any of the systems then in use.

If there yet remained some great continent to be discovered, we might still hope to become acquainted with new species, among which there might be found some having more or less similarity to those of which we have discovered the remains in the bowels of the earth. But it is sufficient to cast a glance over the map of the world, and see the innumerable directions in which navigators have traversed the ocean, in order to be satisfied that there remains no other large land to be discovered, unless it may be situated towards the South Pole, where the existence of life would necessarily be precluded by the accumulation of ice.

Hence, it is only from the interior of the large divisions of the world, that we can have any hope of still procuring quadrupeds hitherto unknown. But a little reflection will be sufficient to convince us, that our expectations from this source have as little foundation as from that of the islands.

Doubtless, the European traveller cannot easily traverse vast extents of countries, which are either destitute of inhabitants, or are peopled only with ferocious tribes; and this is more especially true with regard to Africa. But there is nothing to prevent the animals themselves from roaming over these countries in all directions, and penetrating to the coasts. Even when there may be great chains of mountains between the coasts and the deserts of the interior, they must always be broken in some places to allow the rivers to pass through; and, in these burning deserts, the quadrupeds naturally follow the banks of rivers. The inhabitants of the coasts also ascend these rivers, and soon become acquainted with all the remarkable species which exist even to their sources, either from personal observation, or by means of intercourse with the inhabitants of the interior. At no period, therefore, could civilized nations have frequented the coast of a large country for any considerable length of time, without gaining some tolerable knowledge of such of the animals which it contained as were remarkable for their size or configuration.