Page:A Treatise on Geology, volume 2.djvu/120

 106 iron, and apparently some fragments of clay slate. At the time of their formation, the mineral masses which they traverse must have undergone a considerable disturbance; for the broken ends of the schistose beds and granite veins, where they pass, are distinctly heaved from their original position.

"Still further west we found the rocks beautifully intersected by granitic veins; the higher part being traversed by innumerable ramifications, while the lower part is cut through by one well-defined vein about a foot thick, which, after keeping nearly in the direction of the beds of slate for about sixty feet, suddenly starts off at right angles to its former direction, and rises up to the top of the cliff. The whole system of veins here described afterwards unites in one trunk, which traverses a projecting ledge of rock, and descends obliquely into a mass of granite which forms the eastern side of the entrance into a singular natural cavern. Both sides of its entrance are of granite, but the roof is formed by undisturbed beds of killas. The granitic masses, however, soon contract their dimensions, and wedge out in the schistose rocks, which form both the roof and walls of the cavern, about 50 feet from its commencement.

"From the very point which is marked by so much confusion, two large veins, separated by a lancet-shaped mass of slate, rise towards the west at an angle of about 15°. Within a few feet of the other two, a third vein starts out nearly at the same angle, and proceeds in the same direction. These three veins are throughout nearly of the same thickness, viz. each about five feet. The highest, at some distance from its base, begins to ascend more rapidly, and is lost in the alluvial soil at the summit. The other two preserve their course, without being much deflected, for some hundred feet from the place where we first remarked them, and disappear behind a projecting part of the cliff. On turning this projecting ledge, we suddenly reached a recess, the lower part of which was filled with the ruins from the higher part of the overhanging rocks.