Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/315



These several rocks are all found within a very limited space; but it was impossible to form any conclusion as to their relation to each other, in regard to position, for they are only seen in separate masses projecting above the surface. The gneiss seems, however, to be the prevailing rock on the northern side, as well as in the upper part of the Holly-Bush Hill, and in the latter place, the slaty structure of the rock is perpendicular to the plane of the horizon.

§ 42. On the south side of the Holly-Bush Hill, there is a rock of a dark brown colour, composed of compact felspar, hornblende, quartz, and steatite, with a few detached crystals of felspar imbedded in it, producing a kind of porphyritic structure: this appearance becomes more distinct, when the rock is a little decomposed. It has an earthy texture, with somewhat of an uneven fracture, and is attracted by the magnet. In a small quarry, about a quarter of a mile to the westward, I found the same rock in various stages of decomposition. Where it is most decomposed, it becomes a friable mass of an ochre yellow colour.

§ 43. The last place, where I found the rock exposed at the south end of the range, was about half a mile beyond the Holly-Bush Hill ; it was called the Ragstone Hill by some quarries whom I found at work. The rock that occurs here is different from any other I met within these hills. It is of an olive green colour, and, as far as the closeness of its texture enables me to say, is composed of felspar and mica, united by a ferruginous clay, forming nearly a homogeneous mass, and occasionally traversed by veins of calcareous spar. It occurs massive, without any signs of stratification.

§ 44. Before concluding this enumeration of the unstratified rocks, I may notice a breccia, of which I found a loose block in a lane near the Holly-Bush Hill on the western side, but which I could not discover any where in situ. It is composed of rounded fragments of