46 ON THE REVOLUTIONS OF 



them, that we owe the little knowledge we have attained respecting 

 the nature of the revolutions of the globe. They have taught us, that 

 the layers which comprise them have been undisturbedly deposited in 

 a liquid ; that their alterations have corresponded with those of the 

 liquid ; that their exposure was occasioned by the removal of this 

 liquid ; that these exposures have taken place more than once. None 

 of these facts could have been decided on without these fossils. 



The study of the mineral portion of geology, which is not less ne- 

 cessary, which is even of still greater utility with regard to the me- 

 chanical arts, is yet much less instructive with relation to the object of 

 which we are treating. 



We are in positive ignorance regarding the causes which can have 

 produced the changes of the substances composing the layers ; we do 

 not even know the agents which could have held certain of them in 

 solution ; and it is yet a matter of controversy, whether certain of them 

 owe their origin to water or fire. To come at once to the point, we 

 observe that there is a general agreement on one point only ; namely, 

 that the sea has changed its situation. And how should we know that 

 if we had no fossils ? 



Fossils, which have given birth to the theory of the earth, have also 

 furnished it with its principal lights, the only ones which have been 

 generally recognized down to the present period. 



It is this idea which has encouraged us to take up the subject ; but 

 the field is immense ; a single person could only glance over but a 

 very trifling part. A choice was to be made therefore, and we did not 

 hesitate. The class of fossils which forms the object of this work at 

 once determined us, because we saw that it is at the same time more 

 pregnant with precise results, and yet less known and more rich in 

 novel matters of research *. 



Paramount importance of the Fossil Bones of Quadrupeds. 



It is apparent, that the bones of quadrupeds conduct us, by various 

 reasonings, to more precise results than any other relics of organized 

 bodies. 



In the first place, they characterize more clearly the revolutions 

 which have effected them. Shells prove that the sea was once where 

 they are now found ; but their change of species could only at the ut- 

 most proceed from slight variations in the nature of the liquid or 

 merely in its temperature. 



* My work has in fact proved the situation of this subject -when I took it up, hi 

 spite of the admirable labours of Camper, Pallas, Blumenbach, Merk, Sceinmeiing, 

 Ruscn, Mullcr, Fischer, Faujas, Home, and other learned men, whose works I have 

 quoted with much care in those chapters of my books to which they relate. 



