12 



GEOLOGY OF ARRAN. 



tance northwards, on both sides of the stream, down into 

 Eas-an-Bhiorach. On the western side of the lorsa valley 

 it is continuous over the whole surface, from the level of the 

 great fall on the lorsa to the summits of the hills, and attain- 

 ing, on the east side of Ben-Bharrain, an elevation nearly as 

 great as the depression between the two summits, which, as 

 well as the whole central and western parts of this group, 

 are composed entirely of the coarse variety. The junction 

 of the two kinds and their interlacing veins are finely seen 

 on the southern front of Sail-Chalmadale. 



On the eastern side of the lorsa valley the fine-grained 

 granite stretches continuously along the western base of the 

 Cior-Mhor and Ben-Ghnuis group, rising high on the western 

 side of these mountains, Caistael-Abhael and the Ceims, and 

 forming the summits of the passes into Glen Sannox and 

 Glen Rosa, on the northern and southern sides of Cior-Mhor. 

 Mantling round the southern flanks of Ben-Ghnuis, the fine 

 granite runs out against the slate, which it penetrates and 

 alters. The relation of the rocks here is shewn in the an- 

 nexed diagram (fig. 4), which is a ground plan : 



c . Fig. 4. c 



a, Coarse granite ; b, fine granite ; c, slate altered and banded. 



The coarse variety is seen in close proximity, impenetrated 

 also by veins of the fine-grained granite. By the fall of the 

 ground both ways eastwards towards the Garbh-Alt and 

 Glen Rosa, and westwards towards the lorsa the coarse- 

 grained granite soon emerges from beneath the fine, and thus 



