Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/157

 which the little river Walkham flows, and near the point at which it falls into the Tavy, a remarkable change of strata occurs; the side of a very abrupt hill, on the top of which is West Down, in the parish of Whitchurch, is composed of a considerable cluster of detached masses of granitic rocks, which are piled on each other in the most picturesque manner, and form a lofty and steep bank to the river. Killas occurs in the same hill, on each side, and is the only rock observable on that which rises from the opposite edge of the valley.

If we turn from the country on the east and north of Morwel Down, to that on the west of it, we shall find that the Cornwall side of the river Tamar is more diversified in the rocks that occur; killas generally prevails, but granite crowns the summit of Kithill, which rises gradually from the banks of the river to the height of 1400 feet, and the same rock is to be found near the base of the mountain, at Gunnis Lake Copper Mine, near New Bridge, and again a little higher up the stream, at a place called the Clitter, a provincial word, signifying a collection of loose masses of rock. The killas district is nearly surrounded on the three sides above