From the above stones forming a regular chain, as well as from the immense size of the two largest, it is impossible to suppose that they have been moved; and it is infinitely more probable, that they are parts of a granite vein, which runs across the sandstone strata, and of which some parts have resisted the action of the weather, while the rest have yielded to it. The whole geological history of this part of Africa seems highly interesting, since, as far as can be collected from the accounts of the ingenious traveller just mentioned, it consists of horizontal beds of sandstone or limestone, resting immediately on granite, or on primary schistus. Loose blocks of granite are seen in great abundance at the foot of the Table Mountain, and along the sea shore. * * * * * 358. The system which accounts for such phenomena as have been considered in this and some of the preceding notes, by the operation of a great deluge, or _debacle_, as it is called, has been already mentioned. In Dr Hutton's theory, nothing whatever is ascribed to such accidental and unknown causes; and, though their existence is not absolutely denied, their effects, whatever they may have been, are alleged to be entirely obliterated, so that they can be referred to no other class but that of mere possibilities. A minute discussion, however, of the question, Whether there are, on the surface of the earth, any effects that require the interposition of an extraordinary cause, would lead into a longer digression than is suited to this place. I shall briefly state what appear to be the principal objections to all such explanations of the phenomena of geology. 359. The general structure of valleys among mountains, is highly unfavourable to the notion that they were produced by any single great torrent, which swept over the surface of the earth. In some instances, valleys diverge, as it were from a centre, in all directions. In others, they originate from a ridge, and proceed with equal depth and extent on both sides of it, plainly indicating, that the force which produced them was _nothing_, or evanescent at the summit of that ridge, and increased on both sides, as the distance from the ridge increased. The working of water collected from the rains and the snows, and seeking its way from a higher to a lower level, is the only cause we know of, which is subject to this law.