Dr. Mac Culloch oji Qjiartz Rock. 475 



On the borders of Loch Leven, and on its northern side, irLs 

 most abundant, and appears to constitute large portions of the 

 mountains, having an evident similarity of direction and dispo- 

 sition, to those masses of it which form the principal parts of the 

 mountains of Ben-na-vear on the opposite or southern side of this 

 lake, and which I am now about to describe. 



I have already had occasion to mention in a note supplementary 

 to the account of Cruachan, that granite is found at the base of 

 the group of mountains called Ben-na-vear, extending from Bala- 

 hulish towards Glenco in one direction, and for a considerable 

 space along the Appin road in the other. On ascending this group, 

 the granite continues for some way. This is followed by a rock, 

 which, although it forms here as in many other places, considerable 

 portions of mountain masses, has scarcely received a name and an 

 establishment in the system of rocks. It is a sort of schistose 

 quartz ; it is not graywacke, nor is it micaceous schist, though it 

 contains grains of quartz, and mica, and clay : neither is it gneiss, 

 although it contains grains of felspar. Previous prejudices might 

 perhaps find it a place among either of these, according as the 

 predominant system dictated. But the best idea of its general 

 structure may be conveyed by saying, that if it was a floetz rock it 

 would be called a schistose sandstone. There is in many cases so 

 strong an affinity between the rocks of the primary and of the 

 secondary, or flcetz, classes, that it can scarcely lead to error, if, 

 pursuing this analogy, I should call it a schistose quartz rock. It- 

 will in fact be found to form the same connexion between the mi- 

 caceous or clay slate and the quartz rock, as the schistose sandstones 

 which alternate with thin laminae of clay slate do between the latest 

 clay slates or shales and common sandstone. And thus, as in other 



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