Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/314

 rock composed of hornblende and mica, intermixed with a small quantity of felspar, quartz, and pyrites. It occurs in large masses irregularly heaped together, and the relative position of the schistose structure in the different masses preserves no uniformity. It is traversed by granite veins, varying from one to six inches in thickness, branching in different directions, and diminishing in thickness as they ascend. This schistose rock is very similar to one that occurs by the side of the road leading up to the Wych, where it is also traversed by granite veins.

§ 41. A deep but narrow valley separates Swinnit Hill from the Holly-Bush Hill. In this valley, and in the lower part of the latter hill, I found the following rocks:

a. Different varieties of gneiss, imperfectly characterized. it seems to bear the same relation to true gneiss, that the granite of these hills has been described to bear to Alpine granite.

b. A fine grained sandstone, consisting principally of quartz, with a few particles of felspar and mica: in some places it includes large rounded fragments of quartz and felspar, having the appearance of a breccia.

c. Granular quartz, mixed with small white specks of decomposed felspar.