too 



ILLUSTRATIONS OF THE 



and nearly horizontal *. The higheft fummit 

 of this mountain is, by Sauffure's meafurement^ 

 ^4S0 toifes, or- 14739 Englifii feet, above the 

 level of the fea, or lower than the top of Mont 

 Blanc only by 20 toifes, or 128 feet f . This is, 

 I believe, the higheft point on the earth's fur- 



fa 



at 



h the marks of reg 



ftratifica 



inly knowa to exift ; for though 



by the account of the fame 



mineralo 



gift, Mont Blanc itfelf is ftratified, yet, as the 



r 



rock is granite, the ftratification vertical, and 

 fomewhat ambiguous, it is much lefs proper 

 than Mont Pvofa for afcertaining the limit in 

 queftion. 



r 



178. Again, in the ntw continent, we have 

 an inftance of Qiells contained in a rock, not 



4 



much lower than the fummit of Mont Rofa. 

 This is one defcribed by Don Ulloa, near the 

 quickfilver mine of Guanca- Veiica, in Peru. 

 The height at which a fpecimen of thefe fliells, 



found, 



was 2 2 22-i toifes, or 141 90 feet Englifti, above 

 the level of the fea {. This height agrees with 

 the preceding, within 549 feet, a quantity com- 

 paratively fmall. 



\ 



given by Ulloa to M. le Gentil, 



was 



179 



The 



* Voyages aux Alpes, torn, iv, § 2138. 

 f IduL § 2135. 



i See Hill. Acad, del Sciences, 1770. Phjf. Genc- 

 ral€,^No. 7. 



