The beds which present the most definite appearances of abrupt fracture, are those of that grey or black limestone above described (Chap. x. Sec. 4), formed into a number of thin layers or leaves, commonly separated by filmy spreadings of calcareous sand, hard when dry, but easily softened by moisture; the whole, considered as a mass, easily friable, though particular beds may be very thick and hard. Imagine a layer of such substance, three or four thousand feet thick, broken with a sharp crash through the middle, and one piece of it thrown up as in Fig. 11. It is evident that the first result of such a shock would be a complete shattering of the consistence of the broken edges, and that these would fall, some on the instant, and others tottering and crumbling away from time to time, until the cliff had got in some degree settled into a tenable form. The fallen fragments would lie in a confused heap at the bottom, hiding perhaps one half of its height, as in Fig. 12; the top of it, wrought into somewhat less ragged shape, would thenceforth submit itself only to the gradual influences of time and storm. [Illustration: FIG. 11.] [Illustration: FIG. 12.] I do not say that this operation has actually taken place. I merely say that such cliffs do in multitudes _exist_ in the form shown at Fig. 12, or, more properly speaking, in that form modified by agencies in visible operation, whose work can be traced upon them, touch by touch. But the condition at Fig. 12 is the first rough blocking out of their form, the primal state in which they demonstrably were, some thousands of years ago, but beyond which no human reason can trace them without danger of error. The cloud fastens upon them there. Sec. 15. It is rare, however, that such a cliff as that represented in Fig. 12 can maintain itself long in such a contour. Usually it moulders gradually away into a steep mound or bank; and the larger number of bold cliffs are composed of far more solid rock, which in its general make is quite unshattered and flawless; apparently unaffected, as far as its coherence is concerned, by any shock it may have suffered in being raised to its position, or hewn into its form. Beds occur in the Alps composed of solid coherent limestone (such as that familiar to the English traveller in the cliffs of Matlock and Bristol), 3000 or 4000 feet thick, and broken short off throughout a great part of this thickness, forming nearly[50] sheer precipices not less than 1500 or 2000 feet in height, after all deduction has been made for slopes of debris at the bottom, and for rounded diminution at the top.