Page:A Treatise on Geology, volume 1.djvu/137

 CHAP. VI. —the Sugarloaf in Wicklow,—the wildly broken crags of mica schist in the Trosachs, are too familiar to need description; but, picturesque effects of this high order depend on a combination of circumstances; the position and hardness of the rocks—relative depth of valleys and other causes; and large tracts of gneiss in Ross and Sutherland, and of mica schist in Argyle, can by no fancy be transformed into the sublime or beautiful. Yet, even in the dreariest wastes around the heads of the highland glens the hills of gneiss, mica schist or quartz rock, contain elements of form and colour which the artist knows how to value. Monotonous as they sometimes are, the irregularity of their outline prevents formality; the immensity of the mountains fills while it saddens the mind; and if the scarcity of wood gives a wildness to the fairest lakes, the partial herbage, lichens and mosses, cover the hills with tints suitable to the other features of the landscape. It is not prettiness nor gentle beauty, nor antithetic effect of colour or outline, which reward the wanderer among the Grampian Hills; but a deep feeling of the grand and awful harmonies of nature is sure to steal into his mind, and linger there even after he has climbed the snowy Alps or sunny Pyrenees.

Igneous Rock.—Granite, as was stated before, is found almost universally beneath gneiss and mica schist,— sometimes touching one (gneiss most frequently), some. times the other. It generally appears to have been in a state of fusion since the deposition of these superincumbent strata, since veins of it are injected into their cracks and fissures. (Examples may be seen in Glen Tilt, in Arran, in Skiddaw, in Wicklow, &c.) Porphyritic dykes divide mica schist under Ben Cruachan, and gneiss in Glen Coe. A mass of porphyry has perforated the granite and mica schist of Ben Nevis. Greenstone and other trap dykes are frequent (Perthshire). Serpentine occurs at Portsoy, in Iona, Lewis, and Zetland, in Connemara, &c. Very long and remarkable trap dykes run east and west through the mica