beds of ancient streams. They widen and contract without any general rule; their waters sometimes expand into lakes, and sometimes descend in torrents; and here and there the rocks, suddenly approaching from each side, form transverse dikes, over which the waters fall into cataracts. The shattered strata of these valleys expose their edges on one side, and present on the other side large portions of their surface lying obliquely; they do not correspond in height, but those which on one side form the sum. mit of the declivity, often dip so deep on the other as to be altogether concealed." These proofs also correspond with the opinions entertained by Mr. Kirwan. He states that no masses, or strata, containing shells, or other petrified organic remains, are found higher than 8500 or 9000 feet above the present level of the sea.* Hence the earth, since the creation of animated beings, was covered with water to that level, and consequently the revolutions which appear to have taken place in the higher mountains were produced at a period anterior to the existence of animal life. Cuvier does not go into detail on this subject, but refers for proofs more at large to Pallas, Saussure, Deluc, and others, and concludes the section thus: "Hence, it is impossible to deny, that the waters of the sea have formerly, and for a long time, covered those masses of matter which now constitute our highest mountains; and farther, that these waters, during a long time, did not support any living bodies. Thus, it has not been only since the commencement of animal life that these numerous changes and revolutions have taken place in the constitution of the external covering of our globe: for the masses formed previous to that event have suffered changes, as well as those which have been formed since; they have also suffered vioTent changes in their positions, and a part of these assuredly took place while they exist. ed alone, and before they were covered over by the shelly masses. The proof of this lies in the overturnings, the disruptions, and the fissures which are observable in their strata, as well as in those of more recent formation, which are there even in greater number and better defined. "But these primitive masses have also suffered other revolutions, posterior to the formation of the secondary strata, and have perhaps given rise to, or at least have partaken of, some portion of the revolutions and changes which these latter strata have experienced. There are actually considerable portions of the primitive strata uncovered, although placed in lower situations than many of the secondary strata; and we cannot conceive how it should have so happened, unless the primitive strata, in these places, See Kirwan's Geological Essays. had forced themselves into view, after the formation of those which are secondary. In some countries, we find numerous and prodigiously large blocks of primitive substances scattered over the surface of the secondary strata, and separated by deep valleys from the peaks or ridges whence these blocks must have been derived. It is necessary, therefore, either that these blocks must have been thrown into those situations by means of eruptions, or that the valleys, which otherwise must have stopped their course, did not exist at the time of their being transported to their present sites. series of epochs anterior to the present time, and of which the successive steps may be ascertained with perfect certainty, although the periods which intervened cannot be determined with any degree of precision. These epochs form so many fixed points, answering as rules for directing our inquiries respecting this ancient chronology of the earth." "Thus we have a collection of facts, a In order to show that "the causes which act at present on the surface of our globe," are imcompetent to produce the revolutions above referred to, he next enters into their examination, in which he treats "of slips, or falling down of the materials of mountains ;" "of alluvial formations;"" of the formation of Downs ;" "of the formation of cliffs or steep shores;" "of depositions formed in water;" "of stalactites;" "of lithophites;" " of incrustations;" and "of volcanoes," from which he draws the following conclusions: "Thus we shall seek in vain, among the various forces which still operate on the surface of our earth, for causes competent to the production of those revolutions and catastrophes of which its external crust exhibits so many traces: and if we have recourse to the constant external causes with which we have been hitherto acquainted, we shall have no greater success." He also concludes (p. 56) that astronomical causes could not have produced these revolutions, at least such as have a slow and gradual operation. The mutation of the earth's axis never exceeds 10 or 11 degrees, and this gradually advances to its maximum, and as gradually returns. This, and the subsidence of the waters from the earth, and the changes from heat to cold, or from cold to heat, are all incompetent, since in acting slowly, they could not have produced sudden effects. After these remarks, he observes that naturalists have been led to make many extraordinary suppositions, and to lose themselves in "erroneous and contradictory speculations." Hence he is led to take a view" of former systems of geology," in which he gives a summary of the prin cipal theories of the earth, that have been "Thus, in the opinion of Burnet, the whole earth at the first consisted of a uniform light crust, which covered over the abyss of the sea, and which, being broken for the production of the deluge, formed the mountains by its fragments. According to Woodward, the deluge was occasioned by a momentary suspension of cohesion among the particles of mineral bodies; the whole mass of the globe was dissolved, and the soft paste became penetrated by shells. Scheuchzer conceived that God raised up the mountains for the purpose of allowing the waters of the deluge to run off, and accordingly selected those portions which contained the greatest abundance of rocks, without which they could not have supported themselves. Whiston fancied that the earth was created from the atmosphere of one comet, and that it was deluged by the tail of another. The heat which remained from its first origin, in his opinion, excited the whole antediluvian population, men and animals, to sin, for which they were all drowned in the deluge, excepting the fish, whose passions were apparently less violent. "It is easy to see, that though naturalists might have a range sufficiently wide within the limits prescribed by the book of Genesis, they very soon found themselves in too narrow bounds: and when they had succeeded in converting the six days employed in the work of creation into so many periods of indefinite length, their systems took a flight proportioned to the periods, which they could then dispose of at pleasure. "Even the great Leibnitz, as well as Descartes, amused his imagination by conceiving the world to be an extinguished sun, or vitrified globe: upon which the vapours, condensing in proportion as it cooled, formed the seas, and afterwards deposited calcarious strata. "By Demaillet, the globe was conceived to have been covered with water for many thousand years. He supposed that this water had gradually retired; that all the terrestrial animals were originally inhabitants of the sea; that man himself began his career as a fish and he asserts, that it is not uncommon, even now, to meet with fishes in the ocean, which are still only half men, : but whose descendants will in time become "The system of Buffon is merely an ex- "In the present day, men of bolder imaginations than ever, have employed themselves on this great subject. Some writers have revived and greatly extended the ideas of Demaillet. They suppose that every thing was originally fluid; that this universal fluid gave existence to animals, which were at first of the simplest kind, such as the monads and other infusory microscopic animalcules that, in process of time, and by acquiring different habits, the races of these animals became complicated, and assumed that diversity of nature and character in which they now exist. It by all those races of animals that the waters of the ocean have been gradually converted into calcarious earth; while the vegetables, concerning the origin and metamorphoses of which these authors give us no account, have converted a part of the same water into clay; and these two earths, after being stript of the peculiar characters they had received respectively from animal and vegetable life, are resolved by a final analysis into silex: hence the more ancient mountains are more silicious than the rest. Thus, according to these authors, all the solid particles of our globe owe their existence to animal or vegetable life, and without this our globe would still have continued entirely liquid. "Other writers have preferred the ideas of Kepler, and, like that great astronomer, have considered the globe itself as possessed A proof living faculties. According to them, it contains a circulating vital fluid. cess 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 of its molecules, which attract and repel each other according to sympathies and antipathies. Each kind of mineral substance is capable of converting immense masses of matter into its own peculiar nature, as we convert our aliment into flesh and blood. The mountains are the respiratory organs of the globe, and the schists its organs of secretion. By the latter it decomposes the waters of the sea in order to produce volcanic eruptions. The veins in strata are caries, or abscesses of the mineral kingdom, and the metals are products of rottenness and disease, to which it is owing that almost all of them have so bad a smell. "It must, however, be noticed, that these are what may be termed extreme examples, and that all geologists have not permitted themselves to be carried away by such bold or extravagant conceptions as those we have just cited. Yet, among those who have proeeeded with more caution, and have not searched for geological causes beyond the established limits of physical and chemical science, there still remain much diversity and contradiction. "According to one of these writers, every thing has been successively precipitated and deposited, nearly as it exists at present; but the sea, which covered all, has gradually retired. "Another conceives, that the materials of the mountains are incessantly wasted and floated down by the rivers, and carried to the bottom of the ocean, to be there heated under an enormous pressure, and to form strata which shall be violently lifted up at some future period, by the heat that now consolidates and hardens them. "A third supposes the fluid materials of the globe to have been divided among a multitude of successive lakes, placed like the benches of an amphitheatre; which, after having deposited our shelly strata, have successively broken their dikes, to descend and fill the basin of the ocean. "According to a fourth, tides of seven or eight hundred fathoms have carried off from time to time the bottom of the ocean, throwing it up in mountains and hills on the primitive valleys and plains of the continent. "A fifth conceives the various fragments of which the surface of the earth is composed, to have fallen successively from heaven, in the manner of meteoric stones, and alleges that they still retain the marks of their origin in the unknown species of animals whose exuviæ they contain. "By a sixth, the globe is supposed to be hollow, and to contain in its cavity a nucleus of loadstone, which is dragged from one pole of the earth to the other by the attraction of comets, changing the centre of gravity, and consequently hurrying the great body of the ocean along with it, so as alternately to drown the two hemispheres." Cuvier bestows much and deserved praise upon Saussure and Werner, and their pupils, for the pains they have taken in investigating the strata of the earth, and ascertaining their respective antiquity, and thus establishing a system of mineral geology as distinguished from his own, or fossil geology. He admits that other authors and naturalists have studied the fossil remains of organized bodies, but "they have almost always neglected to investigate the general laws affecting their position, or the relation of the extraneous fossils with the strata in which they are found." Hence originates his "Theory of the Earth," the substance of which is contained in the 23d and 24th sections of the essay before us. These sections offer proofs of the revolutions heretofore stated to have been numerous and sudden; and as the merits of the subject rest upon this part of the work, we quote at large, to afford a full, entire, and satisfactory view of the theory of our author. "The study of the mineralogical part of geology, though not less necessary, and even a great deal more useful to the practical arts, is yet much less instructive so far as respects the objects 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 strata are composed. We are ignorant even of the agents which may have held some of these substances in a state of solution; and it is still disputed respecting several of them, whether they have owed their origin to the agency of water or fire. After all, philosophers are only agreed on one point, which is, that the sea has changed its place; and this could never have been certainly known, but for the existence of extraneous fossils. These fossils, then, which have given rise to the theory of the earth, have at the same time furnished its principal illustrationsthe only ones, indeed, that have as yet been generally received and acknowledged. "This is the consideration by which I have been encouraged to investigate the subject of extraneous fossils. But the field is extensive; and it is only a very inconsiderable portion of it that can be cultivated by the labour of a single individual. It was necessary, therefore, to select a paritcular department, and I very soon made my choice. That class of extraneous fossils, which forms the peculiar subject of this Essay, engaged my attention at the very outset, because it is evidently the most fertile in affording precise results, yet at the same time less known than others, and richer in new objects of research. "It is obvious that the fossil remains of the bones of quadrupeds must lead to more rigorous 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 been subjected. The remains of shells certainly indicate that the sea has once existed in the places where these collections have been formed: but the changes which have taken place in their species, when rigorously inquired into, may possibly have been occasioned by slight changes in the nature of the fluid in which they were formed, or only in its temperaaccidental causes. ture, and may even have arisen from other We can never be per fectly assured that certain species, and even genera, inhabiting the bottom of the sea, aud occupying certain fixed spaces for a longer or shorter time, may not have been driven away from these 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 carcasses, clearly establishes that the bed in which they are found must have been previously laid dry, or at least that dry land must have existed in its immediate neighbourhood. Their disappearance as certainly announces that this stratum must have been inundated, or that the dry land had ceased to exist in that state. It is from them, therefore, that we learn with perfect certainty the important fact of the repeated irruptions of the sea upon the land, which the extraneous fossils and other productions of marine origin could not of themselves have proved; and, by a careful investigation of them, we may hope to ascertain the number and the epochs of those irruptions of the sea. "Secondly, the nature of the revolutions which have changed the surface of our earth, must have exerted a more powerful action upon terrestrial quadrupeds than upon marine animals. As these revolutions have consisted chiefly in changes of the bed of the sea, and as the waters must have destroyed all the quadrupeds which they reached, if their irruption over the land was general, they must have destroyed the entire class, or, if confined only to certain continents at one time, they must have destroyed at least all the species inhabiting these continents, without having the same effect upon the marine animals. On the other hand, millions of aquatic animals may have been left quite dry, or buried in newly-formed strata, or thrown violently on the coasts, while their races may have been still preserved in more peaceful parts of the sea, whence they might again propagate and spread after the agitation of the water had ceased. "Thirdly, this more complete action is also more easily ascertained and demonstrated; because, as the number of terrestrial quadrupeds is limited, and as most of their species, at least the large ones, are well known, we can more easily determine whe ther fossil bones belong to a species which still exists, or to one that is now lost. As, en the other hand, we are still very far from being acquainted with all the testaceous animals and fishes belonging to the sea, and as we probably still remain ignorant of the greater part of those which live in the extensive deeps of the ocean, it is impossible to know, with any certainty, whether a species found in a fossil state may not still exist somewhere alive." The doubt with which the above quotation concludes, whether any petrifactions of shells are of extinct animals, has also been suggested with respect to the fossil bones of quadrupeds. Nay, we have even been asked the question whether we believed in the reality of organic remains so VOL. III.-No. I 8 frequently met with, belonging to extinct animals. This question as may well be supposed, was not asked by a naturalist, but, as all our readers may not have dip ped into this branch of science, it may be well to inform them that the fact is certain, and that it is as clearly and satisfactorily ascertained as any problem in Euclid. This certainty arises from a knowledge of the natural history of the animat creation; and the more perfect we become in this science, the greater is the conviction that there are organic remains which belong to extinct species. And when to this is added the information derived from comparative anatomy, nothing can be more clear. It has been supposed that there are many species of animals yet unknown to naturalists. This is no doubt true respecting the smaller ones, but of the larger animals, particularly quadrupeds, there is little or no probability of many new species to be found. This subject is investigated (sect. 25, p. 74) by an examination of the information which the ancients possessed, and of the voyages and travels of modern times; and also (p. 85) by an "Inquiry respecting the fabulous animals of the ancients;" from which, our author concludes, that none of the bones of the larger quadrupeds, found in a fossil state, belong to present existing species. Although there exists some difficulty in distinguishing the fossil bones of quadrupeds, yet comparative anatomy clearly demonstrates that there is a certain determinate correspondency between the various organs and the different bones of the skeleton of an animal; "Thus, if the viscera of an animal are so organized as only to be fitted for the digestion of recent flesh, it is also requisite that the jawз should be so constructed as to fit them for devouring prey; the claws must be constructed for seizing and tearing it to pieces; the teeth for cutting and dividing its flesh; the entire system of the limbs or organs of motion, for pursuing and overtaking it; and the organs of sense, for discovering it at a distance. Nature also must have endowed the brain of the animal with instincts sufficient for concealing itself, and for laying plans to catch its necessary victims." "To enable the claws of a carnivorous animal to seize its prey, a considerable degree of mobility is necessary in their paws and toes, and a considerable strength in the claws themselves. From these circumstances, there necessarily result certain determinate forms in all the bones of their paws, and in the distribution of the muscles and tendons by which they are moved. The fore-arm must possess a certain facility of moving in various directions, and consequently requires certain determinate forms in the bones of which it is composed. As the bones of the fore-arm are articulated with the arm-bone or humerus, no change can take place in the form and structure of the former without occasioning correspondent changes in the form of the latter. The shoulder blade also, or scapula, requires a correspondent degree of strength in all animals destined for catching prey, by which it likewise must necessarily have an appropriate form. The play and action of all these parts require certain proportions in the muscles which set them in motion, and the impressions formed by these muscles, must still farther determine the forms of all these bones. "After these observations, it will be easily seen that similar conclusions may be drawn with respect to the hinder limbs of carnivorous animals, which require particular conformations to fit them for rapidity of motion in general; and that similar considerations must influence the forms and connexions of the vertebræ and other bones constituting the trunk of the body, to fit them for flexibility and readiness of motion in all directions. The bones also of the nose, of the orbit, and of the ears, require certain forms and structures to fit them for giving perfection to the senses of smell, sight, and hearing, so necessary to animals of prey. In short, the shape and structure of the teeth regulate the forms of the condyle, of the shoulder-blade, and of the claws, in the same manner as the equation of a curve regulates all its other properties; and, as in regard to any particular curve, all its properties may be ascertained by assuming each separate property as the foundation of a particular equation; in the same manner, a claw, a shoulder-blade, a condyle, a leg or arm bone, or any other bone separately considered, enables us to consider the description of teeth to which they have belonged; and so also reciprocally we may determine the forms of the other bones from the teeth. Thus, commencing our investigation by a careful survey of any one bone by itself, a person who is sufficiently master of the laws of organic structure, may, as it were, reconstruct the whole animal to which that bone had belonged. This principle is sufficiently evident, in its general acceptation, not to require any more ninute demonstration; but when it comes to be applied in practice, there is a great number of cases in which our theoretical knowledge of these relations of forms is not sufficient to guide us, unless assisted by observation and experience. "For example, we are well aware that all hoofed animals must necessarily be herbivorous, because they are possessed of no means of seizing upon prey. It is also evident, having no other use for their fore-legs than to support their bodies, that they have no occasion for a shoulder so vigorously organized as that of carnivorous animals; owing to which, they have no clavicles or accromion pro cesses, and their shoulder-blades are proportionally narrow. Having also no occasion to turn their fore-arms, their radius is joined by ossification to the ulna, or is at least articulated by gynglymus with the humerus. Their food, being entirely herbaceous, requires teeth with flat surfaces, on purpose to bruise the seeds and plants on which they feed. For this purpose also, these surfaces require to be unequal, and are consequently composed of alternate perpendicular layers of hard enamel and softer bone. Teeth of this structure nécessarily require horizontal motions, to enable them to triturate or grind down the herbaceous food; and, accordingly, the condyles of the jaw could not be formed into such confined joints as in the carnivorous animals, but must have a flattened form, correspondent to sockets in the temporal bones, which also are more or less flat for their reception. The hollows likewise of the temporal bones, having smaller muscles to contain, are narrower, and not so deep, &c. All these circumstances are deducible from each other, according to their greater or less generality, and in such manner that some are essentially and exclusively appropriated to hoofed quadrupeds, while other circumstances, though equally necessary to that description of animals, are not exclusively so, but may be found in animals of other descriptions, where other conditions permit or require their existence. "When we proceed to consider the dif ferent orders or subdivisions of the class of hoofed animals, and examine the modifica tions to which the general conditions are liable, or rather the particular conditions which are conjoined, according to the respective characters of the several subdivisions, the reasons upon which these particu lar conditions or rules of conformation are founded become less evident. We can easily conceive, in general, the necessity of a more complicated system of digestive organs in those species which have less perfect masticatory systems; and hence we may presume that these latter animals require especially to be ruminant, which are in want of such or such kinds of teeth; and may also deduce, from the same considerations, the necessity of a certain conformation of the esophagus, and of corresponding forms in the vertebræ of the neck, &c. But I doubt whether it would have been discovered, independently of actual observation, that ruminant animals should all have cloven hoofs, and that they should be the only animals having that particular conformation; that the ruminant animals only should be provided with horns on their foreheads; that those among them which have sharp tusks, or canine teeth, should want horns, &c. "As all these relative conformations are constant and regular, we may be assured that they depend upon some sufficient cause; and, since we are not acquainted with that cause, we must here supply the defect of theory by observation, and in this way lay down empirical rules on the subject, which |