184 DOMAIN II. SILICEOUS. 



" In short, my guides found also in these 

 same rocks a palaiopetre y or primitive petrosilex, 

 of a grey approaching a little to green, trans- 

 lucent at the thickness of a line, and even to 

 1, 2, scaly in its fracture, hard, interspersed in- 

 ternally with dots of a deep green, which are 

 scarcely visible but with a magnifying glass, and 

 which appear to be steatite ; and also some rare 

 dots of pyrites, which, in decomposing, stain of 

 a rusty colour the vicinity of the places they 

 occupy. This stone melts under the blow-pipe 

 into a white and bubbly glass, like that of the 

 felspar." 



Our intelligent author thus describes the rocks 

 he observed on the summit itself of this cele- 

 brated mountain : 



1990. " These rocks, situated nearly 2400 

 fathoms above the sea, are interesting by their 

 being the most elevated of our globe that have 

 been observed by naturalists. M. Bouguer and 

 de la Condamine ascended the Andes of Quito 

 to an equal height, and even some fathoms 

 higher than that of these rocks (2470 fathoms) : 

 they were not however acquainted with rocks; 

 but as they are said to have sent to France 

 chests full of specimens of the mountains, on 

 which their trigonometric operations had con- 

 ducted them, I could have much wished that 



