DOMAIN II. SILICEOUS. 



mit of Mont Blanc consists of granitel*, or a 

 mixture of felspar and siderite ; and the base of 

 all lavas consists of one of these two substances. 

 Whether however we join the Huttonians, in 

 considering granite as the newest substance, the 

 last ejected from the bowels of the earth; or the 

 Wernerians, in regarding it as the most ancient, 

 being deposited from above, we must be allowed 

 to view a substance composed of felspar, quartz, 

 and siderite, as not only a complete and genuine 

 granite, but as perhaps the most noble denomi- 

 nation of that class. 



As Mont Blanc is the most remarkable gra- 

 nitic mountain in the world, it may be instructive 

 to translate Saussure's curious and interesting 

 account of its summit. Of the rocks which that 

 great observer discovered near the summit of that 

 mountain, he gives the following description j 

 which shall be followed by that of the rocks 

 observed on the summit itselff . 



* This, as Saussure especially mentions, 1Q94, was the syenite 

 of Werner at the time when he wrote, A. D. 1795; but Karsten 

 about the same period denned the syenite of Werner to consist of 

 quartz, siderite, and felspar. Jameson however regards syenite as 

 composed of felspar and hornblende; but Kirwan agrees with 

 Karsten. Daubuisson, who is commonly exact, says that syenite is 

 composed of felspar and siderite ; and that any quartz or mica is 

 accidental. 



v f Saussure, 1999, supposes that the summit of Mont Blanc 

 was originally about two leagues under the surface of the earth. 



