282. The island of Arran, remarkable for collecting into a very small compass a great number of the most interesting facts of geology, exhibits many instances of the penetration of schistus by veins of granite. A group of granite mountains occupies the northern extremity of the island, the highest of which, Goatfield, rises nearly to the height of 3000 feet, and on the south side is covered with schistus to the height of 1100. From thence, the line of junction, or that at which the granite emerges from under the schistus, winds, so far as I was able to observe, round the whole group of mountains, with many wavings and irregularities, rising sometimes to a greater, and descending sometimes to a much lower level, than that just mentioned. Along this line, particularly on the south, wherever the rock is laid bare, and cut into by the torrents, innumerable veins of granite are to be seen entering into the schistus, growing narrower as they advance into it; and being directed, in very many cases, from below upwards, they are precisely of the kind which the infiltration of water could not produce, even were that fluid capable of dissolving the substances which the vein consists of. From this south face of the mountain, and from the bed of a torrent that intersects it very deeply, Dr Hutton brought a block of schistus, of several hundred weight, curiously penetrated by granite veins, including in them many insulated fragments of the schistus. From this point, the common section of the granite and schistus descends towards the west side of the mountain, and is visible at the bottom of a deep glen, (Glen-Rosa,) which detaches Goatfield from the hills farther to the west. The junction is laid bare at several places in the bed of the river which runs in the bottom of this glen; and in all of them exhibits, in a greater or less degree, the appearances of disturbance and violence which have accompanied the injection of the granite veins. Many circumstances render this spot interesting to a geologist, and, among others, an intersection of the granite, a little above its junction with the schistus, by a dike or vein of very compact whinstone. The same line of junction is found on the opposite, or north-east, side of the mountain, where it is intersected by another little river, the Sannax, which on this side determines the base of the mountain. This junction is no less remarkable than the other two. The island of Arran contains, I have no doubt, many other spots where these phenomena are to be seen; but I have had no opportunity of observing them, nor do I find that Dr Hutton met with any others in his visit to this island.