37S 



ILLUSTRATIONS OF THE 



ferve, in fome degree, to meafure the quantity 

 of them which time has deftroyed. 



339. If the theory of unftratified mountains 

 namely thofe of whinftone, porphyry, and gra- 

 nite, be admitted as laid down above, it will 

 furnifh a meafure of the deftrudlion which has 

 taken place in the ftratified rocks, and of the 

 vaft depredations which have been made upon 

 them lince they were raifed up from the bottom 

 of the fea. Like every other meafure, however, 

 of wafting, by a thing that is itfelf fubjed to 

 wafte, it, can only give a minimum, or a limit 

 which the quantity wafted muft neeeflarily ex- 

 ceed. 



The abrupt face of a whinftone rock muft be 

 underftood as an evidence, that fome body of 

 ftrata which fupported it when fluid, remain- 

 ed in contad: with it, when it was become fo- 

 lid ; and if this part of the mould in which 

 the whinftone was caft, has difappeared, it 

 muft generally be" afcribed to the operation 

 of wafte and decompolition. 



Such 



a 



face 



for inftance, as that which. Salift}ury Craij pre- 

 fents tothe weft, viz. aperpendicular wall of whin- 

 ftone, about ninety feet high, raifed on a body of 

 fandftone ftrata of the height of about 300 fe^tf 

 can have been produced only by having been abut- 

 ted againft fome ftratified rock, equally abrupt, 



and 



