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.