2o6 The Founders of Geology LECT. 



enormous duration of time was indicated by the erosion of 

 the lavas of these volcanoes, and the transport and deposit 

 of their detritus in the white limestone. 



The fourth age in the Vivarais was represented by cer- 

 tain carbonaceous shales or slates, containing the remains 

 of primordial vegetation to which it was difficult to dis- 

 cover the modern analogues. Giraud-Soulavie believed 

 that he could observe among these slates a succession of 

 organic remains similar to that displayed by the lime- 

 stones, those strata which lay on the oldest marble con- 

 taining ammonites, while the most recent enclosed, but only 

 rarely, unknown plants mingled with known forms. It 

 would thus appear that the deposits of the so-called fourth 

 age were more or less equivalents of those of the three 

 calcareous ages. 



The fifth age was characterized by deposits of conglom- 

 erate and modern alluvium, containing fossil trees, together 

 with bones and teeth of elephants and other animals. " Such 

 is the general picture," the Abb remarks, " presented by 

 our old hills of the Vivarais, and of the modern plains 

 around them. The progress of time and, above all, of 

 increased observation will augment the number of epochs 

 which I have given, and fill up the blanks ; but they will 

 not change the relative places which I have assigned to 

 these epochs." J He felt confident that if the facts observed 

 by him in the Vivarais were confirmed in other regions, a 

 historical chronology of fossil and living organisms would 

 be established on a basis of incontestible truth. In his 

 last volume, replying to some objections made to his 

 opinions regarding the succession of animals in time, he 



1 Op. cit. p. 350. 



