298 Dr. Mac Culloch on the Geology of Gkn Tilt, 



different. It is also no less inconvenient than unnecessary and im- 

 proper, that the designation of a granite vein, when on entering a 

 schistose rock it acquires hornblende, should be changed from 

 granite to syenite. This mineral ought to be regarded as accidental, 

 and whether present or absent it makes no alteration in the rock 

 considered as a mass, nor can it alter or affect the validity of any 

 geological reasonings which may be deduced from the relations of 

 the granite in which it is found, to other rocks. 



It has with equal want of proof been said that granite of dif- 

 ferent aspects belonged to different epochas or periods of forma- 

 tion, and we thus read of newer and older granites, as if mineralo- 

 gists had established criteria by which these several varieties could 

 be referred to a prior or posterior sera. If the connection of trap, 

 sometimes with primary rocks, sometimes with those which con- 

 tain animal remains, gives a support to these speculations where the 

 rocks of this family are concerned, there are no such connections 

 between granite and the surrounding rocks known as to justify them 

 in this case. 



In this place as in many others different varieties of granite are 

 found together, not forming veins nor distinct masses, but gra- 

 duating into each other by an indistinct transition. The several 

 colours succeed each other at the same time with as little order as 

 do the aspect* and proportions of the constituent parts. 



The quartz rock appears again to the eastward of Connalach beg, 

 similar in its aspect to that one last named, and after continuing for 

 a few hundred yards, it is succeeded by another variety of granite 

 of a small grain and flesh colour, which forms a large mass of the 

 mountain. 



A superficial view of this perpetual repetition of granite and 

 quartz rock, would lead to the false conclusion that these two rocks 



