§ 4. Accordingly, these slaty coherents, being usually composed of many elements imperfectly united, are also for the most part grey, black, or dull purple; those which are purest and hardest verging most upon purple, and some of them in certain lights displaying, on their smooth sides, very beautiful zones and changeful spaces of grey, russet, and obscure blue. But even this beauty is strictly connected with their preservation of such firmness of form as properly belongs to them; it is seen chiefly on their even and silky surfaces; less, in comparison, upon their broken edges, and is lost altogether when they are reduced to powder. They then form a dull grey dust, or, with moisture, a black slime, of great value as a vegetative earth, but of intense ugliness when it occurs in extended spaces in mountain scenery. And thus the slaty coherents are often employed to form those landscapes of which the purpose appears to be to impress us with a sense of horror and pain, as a foil to neighboring scenes of extreme beauty. There are many spots among the inferior ridges of the Alps, such as the Col de Ferret, the Col d'Anterne, and the associated ranges of the Buet, which, though commanding prospects of great nobleness, are themselves very nearly types of all that is most painful to the human mind. Vast wastes of mountain ground, covered here and there with dull grey grass, or moss, but breaking continually into black banks of shattered slate, all glistening and sodden with slow tricklings of clogged, incapable streams; the snow water oozing through them in a cold sweat, and spreading itself in creeping stains among their dust; ever and anon a shaking here and there, and a handful or two of their particles or flakes trembling down, one sees not why, into more total dissolution, leaving a few jagged teeth, like the edges of knives eaten away by vinegar, projecting through the half-dislodged mass from the inner rock, keen enough to cut the hand or foot that rests on them, yet crumbling as they wound, and soon sinking again into the smooth, slippery, glutinous heap, looking like a beach of black scales of dead fish, cast ashore from a poisonous sea, and sloping away into foul ravines, branched down immeasurable slopes of barrenness, where the winds howl and wander continually, and the snow lies in wasted and sorrowful fields, covered with sooty dust, that collects in streaks and stains at the bottom of all its thawing ripples. I know no other scenes so appalling as these in storm, or so woful in sunshine.
§ 5. Where, however, these same rocks exist in more favorable positions, that is to say, in gentler banks and at lower elevations, they form a ground for the most luxuriant vegetation; 4. Great power of supporting vegetation. and the valleys of Savoy owe to them some of their loveliest solitudes,—exquisitely rich pastures, interspersed with arable and orchard land, and shaded by groves of walnut and cherry. Scenes of this kind, and of that just described, so singularly opposed, and apparently brought together as foils to each other, are, however, peculiar to certain beds of the slaty coherents, which are both vast in elevation, and easy of destruction. In Wales and Scotland, the same groups of rocks possess far greater hardness, while they attain less elevation; and the result is a totally different aspect of scenery. The severity of the climate, and the comparative durableness of the rock, forbid the rich vegetation; but the exposed summits, though barren, are not subject to laws of destruction so rapid and fearful as in Switzerland; and the natural color of the rock is oftener developed in the purples and greys which, mingled with the heather, form the principal elements of the deep and beautiful distant blue of the British hills. Their gentler mountain streams also permit the beds of rock to remain in firm, though fantastic, forms along their banks, and the gradual action of the cascades and eddies upon the slaty cleavage produces many pieces of foreground scenery to which higher hills can present no parallel. Of these peculiar conditions we shall have to speak at length in another place.
§ 6. As far as regards ministry to the purposes of man, the slaty coherents are of somewhat more value than the slaty crystallines. Most of them can be used in the same way for rough 5. Adaptation to architecture and the fine arts. buildings, while they furnish finer plates or sheets for roofing. It would be difficult, perhaps, to estimate the exact importance of their educational influence in the form of drawing-slate. For sculpture they are, of course, altogether unfit, but I believe certain finer conditions of them are employed for a dark ground in Florentine mosaic.
§ 7. It remains only to be noticed, that the direction of the lamination (or separation into small folio) is, in these rocks, not always, nor even often indicative of the true direction of their larger beds. It is not, however, necessary for the reader to enter into questions of such complicated nature as those which belong to the study of slaty cleavage; and only a few points, which I could not pass over, are noted in the Appendix; but it is necessary to observe here, that all rocks, however constituted, or however disposed, have certain ways of breaking in one direction rather than another, and separating themselves into blocks by means of smooth cracks or fissures, technically called joints, which often influence their forms more than either the position of their beds, or their slaty lamination; and always are conspicuous in their weathered masses. Of these, however, as it would be wearisome to enter into more detail at present, I rather choose to speak incidentally, as we meet with examples of their results in the scenery we have to study more particularly.
[48] Compare the close of § 11, Chap. III. Vol. III., and, here, Chap. III. § 23.