Sec. 4. By what secondary laws this structure may ultimately be discovered to have been produced is of no consequence to us at present; all that it is needful for us to note is the beneficence which appointed it for the mountains destined to assume the boldest forms. For into whatever outline they may be sculptured by violence or time, it is evident at a glance that their stability and security must always be the greatest possible under the given circumstances. Suppose, for instance, that the peak is in such a form as _a_ in Fig. 26, then, however steep the slope may be on either side, there is still no chance of one piece of rock sliding off another; but if the same outline were given to beds disposed as at _b_, the unsupported masses might slide off those beneath them at any moment, unless prevented by the inequalities of the surfaces. Farther, in the minor divisions of the outline, the tendency of the peak at _a_ will be always to assume contours like those at _a_ in Fig. 28, which are, of course, perfectly safe; but the tendency of the beds at _b_ in Fig. 27 will be to break into contours such as at _b_ here, which are all perilous, not only in the chance of each several portion giving way, but in the manner in which they would _deliver_, from one to the other, the fragments which fell. A stone detached from any portion of the peak at _a_ would be caught and stopped on the ledge beneath it; but a fragment loosened from _b_ would not stay till it reached the valley by a series of accelerating bounds. Sec. 5. While, however, the secure and noble form represented at _a_ in Figs. 26 and 28 is for the most part ordained to be that of the highest mountains, the contours at _b_, in each figure, are of perpetual occurrence among the secondary ranges, in which, on a smaller scale, they produce some of the most terrific and fantastic forms of precipice; not altogether without danger, as has been fearfully demonstrated by many a "bergfall" among the limestone groups of the Alps; but with far less danger than would have resulted from the permission of such forms among the higher hills; and with collateral advantages which we shall have presently to consider. In the meantime, we return to the examination of the superior groups. [Illustration: FIG. 29.]