4o8 



ILLUSTRATIONS OF THE 



valley, to the top of a fleep hill. Indeed, 

 if we fuppofe a great fragment of rock to 

 be hurried along on a horizontal or an inclined 

 plane, by the force of water, the moment it 

 comes to a deep valley, and has to rife up over 

 an afcent of a certain fleepnefs, it will remain at 

 reft ; the water itfelf will lofe its velocity, and the 

 heavy bodies Vv'hich it carried with it will pro- 

 ceed no farther. Thus, therefore, we have the 

 following dilemma. If the furface is not fup- 

 pofed to have had a certain degree of uniformi- 

 ty in paft times, a debacle is infufficient for the 

 tranfportation of ftones : If it is fuppofed to have 

 had that uniformity, a debacle is unnecelTary. 



364. Another fa6l, which has been fuppofed 

 favourable to the opinion of the adion of great 

 torrents at fome former period, is, that in coun- 

 tries like that round Edinburgh, where whin- 

 ftone hills rife up from among fecondary ftrata, 

 a remarkable uniformity is obferved in the di- 



1 



region of their abrupt faces. Thus, in the 

 country juft mentioned, the fteep faces general- 

 ly front the weft, while, in the oppofite diredion, 

 the flope is gentle, and the hills decline gradual- 

 ly into the plain. Hence it is fuppofed, that a 

 torrent, fweeping from weft to eaft, has carried 

 off" the ftrata from the weft fide of thefe hills, 



h 



|3iit, being obftrudled by the whinftone rock, 



has 



-f . 



