39'^ LITHOLOGICAL OBSERVATIONS 



almost vertical ; from which it may be inferred, 

 that they compose the body of the mountain it- 

 self. And Loch-Lomond is in fact, a vast hollow 

 scooped out of the same rocks ; for the strata on 

 the west, are found to be only a continuation of 

 those observed on the opposite side. In like man- 

 ner, the islands are formed by the same rocks 

 which occur on the mainland, in the general di- 

 rection already nientioned : so that the whole 

 must have originally constituted one great mass or 

 line of strata, which has been broken or worn 

 into its present shape. 



Ben-Lomond, which, viewed from certain posi- 

 tions, has an uncommonly noble and majestic ap- 

 pearance, rises to the height of 3200 feet. It 

 is composed of mica-slate, passing frequently into 

 talc-slate, and intermixed with vast beds of fel- 

 spar-porphyry and greenstone, which lie ira a po- 

 sition conformable with the strata of the includ- 

 ing rock. In this species of mica-slate, there is 

 much quartz ; particularly, towards the summit of 

 the mountain, the rock appears remarkably pene- 

 trated and traversed by that substance, in veins 

 and masses of every size and form. Indeed, it 

 is found to be the prevailing ingredient through- 

 out the whole formation, and often gives the mica- 

 slate a whitish colour, resembling at a distance 

 that of pure quartz. I did not, however, observe 

 quartz in regular beds. 



