236 GRANITE. 



the trap family ; and is, in fact, only distinguished 

 by it geological connection with granite. Var. c. 

 is often similarly undistinguishable from basalt ; 

 occasionally from the non-fissile hornblende 

 schists; but, like var. b., it is connected with, 

 and passes into granite of the most common cha- 

 racters. 



These varieties occur in Aberdeenshire ; 

 where they are connected with the most ordinary 

 granite, subjacent to gneiss, both by transition 

 and alternation, in a manner so distinct as to 

 leave no doubt respecting their true place in a 

 geological classification, like the present. 



SECOND DIVISION. 

 Of three ingredients. 



A. Quartz, felspar, and mica. 



a. An uniform mixture of the different .ingre- 

 dients. 



b. Distinct additional crystals of felspar imbedded 

 in the general mixture : porphyritic granite. 



Cornwall presents very remarkable examples 

 of this variety. 



c. With two kinds of felspar, the common and the 

 glassy. 



