MODE V. GRANITE. 181 



1987. " The naked rocks that we there meet Summit of 



Mont Blanc. 



with, and which form two kinds of arretes or 

 crests, of a black colour, and somewhat saliant, 

 which we clearly see from the banks of our lake 

 to the left of the highest summit of Mont Blanc, 

 are granites, here detached in scattered frag- 

 ments ; there, in solid rocks, divided by fissures 

 nearly vertical, whose direction is conformable to 

 that which generally predominates in these moun- 

 tains, that is, from the north-east to the south- 

 west, and which I consequently regard as layers. 



" The felspar which enters into the compo- 

 sition of these rocks is white approaching to 

 grey, or green, or redish; it yields under the 

 blow-pipe a glass, from which we may obtain 

 globules of 0,6, transparent, colourless, but full 

 of bubbles. 



" The felspar is here pure, there covered or 

 even mixed with a substance of a grey, inclining 

 to a sea-green, colour; without lustre, earthy, 

 soft; when scratched, whitish grey. This sub- 

 stance appears to be an earthy steatite; it is 

 difficult to obtain pieces of it free from felspar ; 

 those that I separated, melted under the blow- 

 pipe into a greenish glass, translucent, and of a 

 very unctuous aspect. They became discoloured 

 on the iron rod, and dissolved with effervescence. 



" The whitish, semi-transparent quartz, which 



