Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/311



§. 33. In the road which leads up to the Wych, the rocks are laid bare in several places. That which is the most prevalent, is the fine grained greenstone I have mentioned, as forming so great a part of the northern end of these hills, §§ 17.24. There are besides, several other compounds of hornblende, felspar, quartz, and mica, united in various proportions, which are very similar to those I have already spoken of, and which it is now unnecessary to describe in a more detailed manner. These are traversed in many places by veins or shoots of granite: in one of these, the constituent parts are of a larger size than usual, and the mica is regularly crystallized; but it is decomposed near the surface. In one place, there is a vein of white opake quartz intermixed with silvery mica. All these rocks are so confusedly heaped together, and in so shivery a state, that it requires some attention before their real nature, and their relative situation can be well understood.

§ 34. At the Wych, where the rocks have been cut through, as mentioned in § 7. granite is the prevailing rock; in this, red felspar predominates, and the mica, which is also in some places very abundant, is of a dark green colour. Blender veins of calcareous spar are occasionally met with in this granite. There is a considerable quantity of another rock, which seems to fill up the spaces that intervene between the masses of granite. It is chiefly argillaceous, of a dark olive-green colour, with an imperfect slaty structure, and when broken across, shews an earthy fracture: the flat thin masses into which it splits have smooth and shining surfaces, as if polished by friction; it occasionally contains veins of calcareous spur. In some place it is found decomposed, and in that state it becomes very friable. I did not meet with this argillaceous rock in any part of the range that lies to the the north of the Wych. I found here some small portion of a granite partially decomposed, and the surface of the fragments