Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/156

 144 an individual fact, and one of so little extent, were it not that it offers an exception to what I consider as a general law in Cornwall, I mean, the direction and inclination of the grauwacke strata.

A semi-circular beach, covered with fine sand, in front of which stands, in a magnificent bay, St. Michael's Mount, topped by its gothic castle, affords a delightful walk the whole way from Marazion to Penzance. The land rising on both sides, breaks the uniform though imposing grandeur of a horizon bounded by the vault of heaven, and the picture taken in its whole extent, forms one of the most beautiful landscapes that the human eye can contemplate.

At the entrance of Penzance, I remarked some rocks of common grauwacke, which were not I believe in situ. We find in the neighbourhood, indications of this rock, but only close by the sea, shewing, that its geological situation is the same throughout the whole extent of Cornwall. Thus, on leaving the village of Newlyn, on the road from St. Paul, it is seen distinctly in situ, but one hundred and fifty paces farther, the land rising, though but a little, the grauwacke is lost, and we enter upon the granite. From St. Paul to Mouse-hole, by the sea side, the land again falls, and we re-enter the grauwacke about two or three hundred paces from the churchyard of St. Paul. It is remarkable that the grauwacke, although in so low a situation, is no longer slaty, but compact; it is here, however, near the point of its junction with the granite, a circumstance which, more than its absolute height above the level of the sea, determines its particular structure. At the south end of the village of Mouse-hole, the granite lowers so much, that the grauwacke can only be seen at low water. It contains much quartz, and even felspar, and at the place of junction, there are several veins of granite seen shooting through it.