GRANITES OF THE NUCLEUS. 11 



ponent minerals are the same. Both consist of quartz, fel- 

 spar, and mica, the two first being in nearly equal proportions, 

 the last in less quantity than either. In neither kind is the 

 mica replaced by hornblende, so as to form the variety called 

 syenite. This rock is indeed found in Arran, but not within 

 the district called the granite nucleus. There are, however, 

 several varieties of both kinds; but these are merely depend- 

 ent upon slight changes in the colour or size of the constituent 

 crystalline grains. The fine variety has often an arenaceous 

 aspect and sandy feel, from the minuteness of the grains. It 

 has a different " ring" under the hammer, and affects the 

 form of huge flat slabs or sheets, rather than the massive 

 rhombic-block form of the coarse granite, so well seen in the 

 " Cyclopean walls" of Goatfell, Ben-Ghnuis, and Cior-Mhor. 

 The distribution of the two granites within the area of 

 the nucleus is shewn on the accompanying map. The over- 

 lying fine-grained granite is by no means co-extensive with the 

 coarse-grained ; it is, in fact, almost limited to the mountain 

 sides and lower hill-tops within the lorsa basin; only a small 

 area of it spreads out across the watershed towards the north. 

 The coarse-grained variety constitutes the entire mass of the 

 Goatfell group, from the mill-dam round the convexity of the 

 great arch as far as Cior-Mhor, the bottom and sides of Glen 

 Rosa, the east front and highest crests of Ben-Ghnuis and 

 Cior-Mhor, the ridge of the Ceims, which connects them, Glen 

 Sannox, and the southern fronts and summit ridges of Cais- 

 tael-Abhael and Suidhe-Fergus. It occupies also the bottom 

 of Glen lorsa and the sides of that glen, to the height of 

 several hundred feet, running out south to contact with the 

 slate along the hill-sides between Loch lorsa and Loch 

 Ghnuis, and extending up the glen northwards as far as the 

 great waterfall, about a mile south of Loch-an-Davie. This 

 same variety forms the central and lower part of Glen Eas- 

 an-Bhiorach, the ridge on its east side, and the mountains on 

 the east side of Glen Catacol. The fine-grained variety 

 occupies the plateau of Loch-an-Davie, and extends some dis- 



