Nowhere can this first lesson in geology be more forcibly taught than by an examination of the sterile rocks and rapidly decomposing precipices of this bleak and hoary region. Once through the glens, and fairly commencing the ascent of the center mountain, every symptom of existing life has disappeared; and amid the huge, tabular masses that accompany you in the upward journey, there is no trace of organic forms in these vestiges of the past. The nucleus of the whole group is granite, one dense aggregation of crystals; now rent and furrowed by a thousand seams, the heart and penetralia bared and open, a convulsed sea of molten matter still and motionless as the grave! The associated rocks, all of the primary class, are gneiss, mica-slate, quartz-rock, chlorite-slate, and limestone; and these inclose no relic of a living thing. Geology thus ascends the stream of Time; but it gives no farther tidings of a scene like this, save that it arose from the depth beneath at the Creator’s bidding. THE STRUCTURE OF THE DISTRICT.—The mountain of Ben-Mac-Dhui, according to recent measurements, is 4,418 feet in height, and covers a superficial area of nearly forty miles in extent. It occupies a central position in the Grampian range, being about equidistant betwixt Aberdeen on the German Sea and the western coast, so ribbed and indented by the Atlantic. Ranges of granitoid rocks, of the primary class, diverge for nearly forty miles south and north of Ben-Mac-Dhui, thereby giving this mountain a prominence in position possessed by no other within the boundaries of the island. The valleys by which this monarch is surrounded, open in every direction, and run toward every point of the compass. Two great rivers, the Don and Dee, take their rise in some of the deep gullies of the mountain, while the Spey is fed by the innumerable streams that issue from its sides. These rivers have each an easterly direction, which, by their water-shed, give shape and character to the whole district. A hundred lateral glens, with their tributary streams, and all their tarn-head or loch, debouch upon the three principal straths, whereby their deepest solitudes are reached, and the very foundations of their loftiest peaks bared and laid open. There, remote from human habitation, the geologist sees as it were two conditions of the world,—the one, the shattered framework and fragments of its early convulsions, huge mountains prostrate and crumbling beneath his feet,—and the other, the spring-heads of renewed vitality collecting in countless dripping rills, each to sustain its own little plot of pasturage and flowerets, not the less welcome that they are all so rare and alpine, and looking in their freshness as if they were there purposely to cicatrize and heal up the deep scars in the rugged precipices around.