Considerations on the place that the granitic 

 rocks of Mont Blanc and other central sum- 

 mits of the Alps ought to occupy in the order 

 of anteriority of the primitive series. By M. 

 Brochant de Villiers. 



(Anuales des Mines, for 1819.) 

 Read at the Royal Academy of Sciences, May 27, 1816. 



The name of granite was formerly given to all mixed rocl^s 

 composed of crystalline minerals. Saussure has often em- 

 ployed it in this general sense in his works. 



The high Alps of Mont Blanc and St. Bernard, having 

 been much more visited than other pa:rts of the same chain, 

 granites have been mentioned as occurring there, and have 

 been cited in all works on geology. 



During the last fifteen years, mineralogists have agreed to 

 restrain the meaning of the word granite, and only to apply 

 this name to rocks composed of felspar, quartz, and mica,* 

 in a crystalline and not schistose state, and many other rocks 

 formerly confounded with them, have been removed from 

 them. 



* Dr. Mac Culloch has observed (Classification of Rocks, p. 230 and 

 231), that " this distinction is too limited for practical purposes; and, in 

 a geological sense in particular, it is inadmissible :" he states granite as 

 consisting fundamentally of quartz, felspar, mica, and hornblende, va- 

 riously combined, other minerals occasionally entering into its composi- 

 tion and forming integrant parts of it. For a synopsis of this substance 

 consult the work cited above. (Trans.) 



