Sec. 1. Between the aiguilles, or other conditions of central peak, and the hills which are clearly formed, as explained in Chap. XII. Sec. 11, by the mere breaking of the edges of solid beds of coherent rock, there occurs almost always a condition of mountain summit, intermediate in aspect, as in position. The aiguille may generally be represented by the type _a_, Fig. 42; the solid and simple beds of rock by the type _c_. The condition _b_, clearly intermediate between the two, is, on the whole, the most graceful and perfect in which mountain masses occur. It seems to have attracted more of the attention of the poets than either of the others; and the ordinary word, crest, which we carelessly use in speaking of mountain summits, as if it meant little more than "edge" or "ridge," has a peculiar force and propriety when applied to ranges of cliff whose contours correspond thus closely to the principal lines of the crest of a Greek helmet. [Illustration: FIG. 42.] Sec. 2. There is another resemblance which they can hardly fail to suggest when at all irregular in form,--that of a wave about to break. Byron uses the image definitely of Soracte; and, in a less clear way, it seems to present itself occasionally to all minds, there being a general tendency to give or accept accounts of mountain form under the image of waves; and to speak of a hilly country, seen from above, as looking like a "sea of mountains." Such expressions, vaguely used, do not, I think, generally imply much more than that the ground is waved or undulated into bold masses. But if we give prolonged attention to the mountains of the group _b_ we shall gradually begin to feel that more profound truth is couched under this mode of speaking, and that there is indeed an appearance of action and united movement in these crested masses, nearly resembling that of sea waves; that they seem not to be heaped up, but to leap or toss themselves up; and in doing so, to wreathe and twist their summits into the most fantastic, yet harmonious, curves, governed by some grand under-sweep like that of a tide, running through the whole body of the mountain chain. [Illustration: FIG 43.] For instance, in Fig. 43, which gives, rudely, the leading lines of the junction of the "Aiguille pourri"[66] (Chamouni) with the Aiguilles Rouges, the reader cannot, I think, but feel that there is something which binds the mountains together--some common influence at their heart which they cannot resist: and that, however they may be broken or disordered, there is as true unity among them as in the sweep of a wild wave, governed, through all its foaming ridges, by constant laws of weight and motion. [Illustration: FIG. 44.] Sec. 3. How far this apparent unity is the result of elevatory force _in_ mountain, and how far of the sculptural force of water _upon_ the mountain, is the question we have mainly to deal with in the present chapter. [Illustration: FIG. 45.]