LES REVOLUTIONS DTJ GLOBE 11 



the vertical direction of the sedimentary strata in 

 mountain chains. In the plains these strata are 

 horizontal and almost all filled with innumerable 

 marine products, especially shells, which have 

 passed their existence in the spots in which they 

 are found, these fossil shells denoting important 

 changes both in extent and in position in the basin 

 of the seas. In mountains of the second class the 

 conchological deposits are as rich as those of the 

 plains, but the strata are no longer horizontal ; they 

 lie obliquely or even vertically, and their succession 

 is easy to observe in the cuttings of the valleys. 

 Still higher up, towards the summits of the great 

 primitive crests, the remains of animals become 

 more rare, and even vanish altogether ; yet the 

 stratification shows that these deposits have also 

 taken place under water, that they have been over- 

 turned, upheaved, and again thrown down at a 

 very remote period, and that their summits were 

 already above the water level when their concho- 

 logical deposits were formed.* 



What geologist, however, if imbued with the 

 importance of active causes in geology, would 

 refuse at the present day to consider these upheavals 

 and folds in sedimentary strata as phenomena 

 relatively sudden, as violent crises which have inter- 

 rupted at various epochs the quiet continuity of 

 the history of the earth ? 



On the other hand Cuvier saw less happily, no 



* Can we not see in this account a very clear glimpse of the suc- 

 cessive phenomena of the wrinkling of the earth's crust and even of 

 the method of determining the age of mountain chains which were 

 shortly afterwards to be exactly set forth in the remarkable researches 

 of Elie de Beaumont in 1829 ? 



