170 EFFECTS of HEAT 



ned to his native fpot, can form no idea of thofe truths, 

 which at every ftep in an alpine diftricl force themfelves 

 on the mind of a geological obferver. Unfortunately for 

 the progrefs of geology, both London and Paris, are pla- 

 ced in countries of little intereft ; and thofe fcenes by which 

 the principles of this fcience are brought into view in the 

 mod finking manner, are unknown to many perfons bell 

 capable of appreciating their value. The moft important, 

 and at the fame time, the moll aftonifhing truth which we 

 learn by any geological obfervations, is, that rocks and moun- 

 tains now placed at an elevation of more than two miles 

 above the level of the fea, muft at one period have lain at 

 its bottom. This is undoubtedly true of thofe flrata of lime- 

 flone which contain fhells ; and the fame conclunon muft be ex- 

 tended to the circumjacent flrata. The imagination flruggles 

 againft the admifllon of fo violent a pofition ; but mufl yield 

 to the force of unqueflionable evidence ; and it is proved by 

 the example of the moll eminent and cautious obfervers, that 

 the conclufion is inevitable *. 



Another queflion here occurs, which has been well treat- 

 ed by Mr Playfair. Has the fea retreated from the moun- 

 tains ? or have they rifen out of the fea ? He ha* fhewn, 

 that the balance of probability is incomparably in favour of 

 the latter fuppofition ; hnce, in order to maintain the former, 

 we mull difpofe of an enormous mafs of fea, whofe depth 

 is feveral miles, and whofe bafe is greater than the furface 

 of the whole fea. Whereas the elevation of a continent 

 out of a fea like ours, would not change its level above a 

 few feet ', and even were a great derangement thus occa- 

 sioned, 



* Saussure, Voyages dans les Alpes, torn. ii. p. 99. — 104. 



