THEORY OF THE EARTH. 9 



beds, we here discover it at once by their exposed 

 edges, as we follow the valleys that have been ' 

 produced by their disjunction. Great masses 

 of debris form at the foot of the cliffs, rounded 

 hills, the height of which is augmented by every 

 thaw and tempest. 



These inclined strata, which form the ridges 

 of the secondary mountains, do hot rest upon 

 the horizontal strata of the hills which are situ- 

 ate at their base, and which form the first steps 

 in approaching them ; but, on the contrary, dip 

 under them, while the hills in question rest upon 

 their declivities. When we dig through the 

 horizontal strata in the vicinity of mountains 

 whose strata are inclined, we find these inclined 

 strata re-appearing below ; and even sometimes, 

 when the inclined strata are not too elevated, their 

 summit is crowned by horizontal ones *. The in- 

 clined strata are therefore older than the hori- 

 zontal strata ; and as they must necessarily, at 

 least the greater number of them, have been 

 formed in a horizontal position, it is evident that 

 they have been raised f , and that this change in 

 their direction has been effected before the others 

 were superimposed upon them $. 



* See Note A, at the end of thia Essay, 

 t See Note B. 



J The opinion maintained by some geologists, that cer- 

 tain strata have been formed in the inclined position in which 



