TR:E SURFACE OF THE GLOBE. 25 



their summit is crowned with horizontal layers. The oblique layers 

 are then more ancient than the horizontal layers ; and as it is impos- 

 sible, at least with regard to the greater number, that they were 

 originally formed obliquely, it is evident that they have been lifted 

 up ; that they have been so before the others were deposited on 

 them.* 



Thus the sea, previously to the formation of horizontal layers, had 

 formed, others which certain causes had broken up, formed again, 

 and destroyed in a thousand ways ; and, as many of these oblique 

 banks which it had at first formed are loftier than those horizontal 

 layers which have succeeded them, and which environ them, the 

 causes which have given this obliquity to these banks have also forced 

 them above the level of the sea, and formed them into islands, or at 

 least into rocks and inequalities, whether elevated at one end, or that 

 the sinking of the other end had thrown off the waters ; a second 

 result not less clear nor less apparent than the former to any one who 

 will give himself the trouble to study the monuments which authen- 

 ticate this fact. 



Proofs that these Revolutions have been numerous.. 



But the revolutions and changes which have left the earth as we 

 now find it, are not confined to the overthrow of the ancient layers, 

 to this retreat of the sea after the formation of new layers. 



When we compare in detail the various layers one with another, 

 and the productions of nature which they comprise, we soon discover 

 that this ancient sea has not always deposited stones exactly similar, 

 nor the remains of animals of the same species, and that each of its 

 deposites has not extended over the whole surface that it has covered. 

 There have been successive variations there established, the first of 

 which has been in great measure general, and the others appear to be 

 less so. The more ancient the layers are, the greater their uniformity 

 and extent ; the more recent, the more limited and more subject are 

 they to vary at short distances. Thus the displacing of the layers was 

 accompanied and followed by alterations in the nature of the liquid 

 and the materials which it held in solution : and when certain layers, 

 raising themselves above the waters, had divided the surface of the 



* The idea supported by some geologists, that certain layers have been formed in 

 the oblique position in which we now find them, in supposing it true with respect to 

 some that are crystallized, as Mr. Greenhough says, in the same manner as a deposit 

 incrusts the inside of all vessels in which gypseous waters are boiled, it cannot be 

 applied to those which contain shells or round stones, which could not remain thus 

 suspended, awaiting the formation of the cement which was necessary to conglo- 

 merate them. 



