39^ 



ILLUSTRATIONS OF THE 



the tranfportation of ftones. Thefe, when they 

 defcend from the fides of mountains, ani even 



where the declivity of their courfe is not very 

 great, produce efFeds which nothing but dired 

 experience could render credible. The frag- 

 ments of rock which oppofe the torrent, are ren- 

 dered fpecifically lighter by the fluid in which 

 they are immerfed, and lofe by that means at 

 leaft a third part of their weight : they are, at 

 the fame time, impelled by a force proportional 



4 



to the fquare of the velocity with which the 

 water ruOies againft them, and proportional alfo 

 to the quantity of gravel and ftones which it 

 has already put in motion. Perhaps, after ta- 

 king all thefe circumftances into computation, 

 in the midft of a fcene perfedly quiet and undi- 



llurbed, a philofopher might remain in doubt as 



to the power of torrents to move the enormous 

 bodies of rock which are feen in the bottom of 

 the narrow valleys or deep glens of a mountain- 

 ous country ; but his incredulity, fays an expe- 

 rienced traveller, will ceafe altogether, if he has 

 been furprifed by a ftorm in the midft of feme 

 Alpine region ; if he has feen the number and 

 impetuolity of the cataradls which ruftied down 

 the fides of the mountains, and beheld the ruin 

 which accompanied them ; and if, when the tem- 



peft 



pafled, he has viewed thofe meadows, 



which 



