66 Dr. Mac Culloch's Shtch of the 



position or fragment and without symptom of vegetable life, from 

 the borders of the lake to the summits of the mountains. Of its 

 interior extent I have no means of judging, since it is inaccessible. 

 This rock is composed fundamentally of felspar and hornblende, 

 the parts being always distinct and crystallized in various sizes, so 

 as to form varieties more or less coarse. The felspar predominates 

 in the compound, and is either glassy or inclining to that variety ; 

 at times indeed quite opake. To these is superadded hypersthene, 

 but it is neither so abundant as the hornblende, nor is it found so 

 generally dispersed through the rocks. It is traversed by veins of 

 basalt, and by veins containing hypersthend in a larger and more 

 distinct form. 



The other rocks which are found in the Cuchullin hills may all 

 be comprehended under the general term of clinkstone. I find it 

 impossible even to conjecture the relative spaces which are occu- 

 pied by the rocks of this division and the greenstones, but I have 

 already said that the greenstones appeared to me most prevalent. 

 In the southern parts of the Cuchullin they undoubtedly are so, 

 but I am inclined to think that in Blaven, and in those hills which 

 contain the light coloured syenite mixed with darker coloured rocks 

 and which are as I have already noticed so easily distinguished at a 

 distance, the dark rocks will be chiefly found to consist of clink- 

 stone. The varieties which occur are as numerous as they usually 

 are in the different situations in the western islands where this 

 rock is found, with the single exception of Arran, which presents 

 an infinite and instructive variety of them in all their modifications 

 and transitions. In general the clinkstone is simple in its compo- 

 sition, and of a dark lead blue, which sometimes assumes a brighter 

 hue, and occasionally passes through various tints to a pale whitish 

 gray or ash-colour. In many places it is porphyritic, the porphy- 



