In the immediate vicinity of Castleton and Invercauld, the geological phenomena of the district are very accessible as well as instructive, in consequence of the comparative smallness of the mountains, and isolated position into which they are thrown. A magnificent amphitheater of hill and plain is spread out before the traveler, through which the Dee, after a course of upward of twenty miles from its wells—mysterious as the fountains of the Nile—rolls its waters, now joined by the Quioch, Clunie, Candlie, and all the tributaries of the surrounding peaks. Some of the hills present bare precipitous cliffs, as Craig Koynach and the Lion’s Face, where the granite, schistose, and calcareous rocks are finely exposed to view. Their strike is continued westward, when they are severally crossed in the easy ascent of Morne, half of whose dome-shaped top is covered with quartz-rock, which here, as in most of the neighboring heights, attains to an enormous thickness, and shows in weathering the yellow granular texture of sandstone. So remarkably like are some specimens we picked up by the roadside, that for a time we imagined ourselves to be approaching a region of secondary deposits. Internally, however, the bright crystalline structure is uninvaded by decay. Ben-Beck, Cairn-a-drochel, and Ben-Viach behind Mar Lodge, are chiefly composed of gneiss, passing into a slaty micaceous schist. The same character of rock continues upward through Glen-lui until its junction with Glen-lui-beg and Glen-derry, where the granite maintains its sovereignty over all that primitive lofty region. The geologist, in penetrating these primeval wilds, has but little choice left him as to the comforts of his pathway. Arrived at the top of Glen-lui, the two diverging passes, right and left, are equally desolate, savage, and grand. He may make his selection as the feeling of the moment prompts, but he will not be able to congratulate himself as the traveler in a different field— Hic locus est, partes ubi se via fundit in ambas: _Dextera_, quæ ditis magni sub mænia tendit; Hac iter Elysium nobis: ut _læva_ malorum Exercet pænas, et ad impia Tartara mittit. No “fiends,” indeed, as Dryden renders it, are here, unless the belated traveler may allow his fancy to shape these gnarled withered stumps of the old forest, as it well may, into grisly living forms; or the red deer breaking from their coverts, and gazing in wild amazement from the crags, startle him from his propriety. Still Loch Avon, black as pitch, and imbosomed in horrid rocks, is not an unfitting emblem of the Tartarean lake.