300 M. Elie de Beaumont on the Relative Age of Mountains. 



tions of the strata which so many systems of mountains present 

 to us, or, in other words, to shew by examples that the disloca- 

 tion of a certain portion of the external crust of the globe has 

 formed an essential integrant part of each of the abrupt changes 

 of which zoologists and geologists have discovered the traces, 

 and to which the labours of M. Cuvier have so strongly called 

 the attention of the learned world. 



M. Cuvier has shewn that the surface of the globe has expe- 

 rienced a series of sudden and violent revolutions. M. Leopold 

 de Buch has pointed out precise and distinct differences between 

 the various systems of mountains which are raised upon the sur- 

 face of Europe. The present essay of M. Elie de Beaumont 

 is a first attempt to establish a kind of alliance between these 

 two ideas. 



In the four separate chapters of which his memoir is compos- 

 ed, the author has successively considered four of the most 

 marked solutions of continuity which the series of sedimentary 

 deposites presents, and has tried to connect each of them with 

 the raising of the sedimentary strata in a determinate system of 

 mountains. -■ 



" To attribute," says he in concluding, " to slow and progres- 

 sive modifications the whole of the changes that have been ef- 

 fected upon the earth's surface, and to overlook the traces of 

 sudden revolutions which have almost periodically renewed the 

 state of that surface, would be to suppress one of the most im- 

 portant and most striking features of its history. Every thing 

 leads us more and more to divide the facts which the sediments 

 ary formations present to our observation into two distinct clas- 

 ses ; the one comprehending the facts relating to the tranquil and 

 progressive course which the accumulation of each of the sedi- 

 mentary deposites has followed, the other containing the facts 

 relating to the sudden interruptions which have established lines 

 of demarcation between the different consecutive deposites. 



" After thus admitting violent and transitory phenomena, it 

 is more easy to perceive the resemblance to the phenomena of 

 the present period presented by those which were repeated on 

 the surface of the globe during the different periods of tranquil- 

 lity in the course of which the various sedimentary deposites 

 ■were successively formed." 



M. Elie de Beaumont announced further, that he had no in- 



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