Sec. 8. For it is evident that, through all their ruin, some traces must still exist of the original contours. The directions in which the mass gives way must have been dictated by the disposition of its ancient sides; and the currents of the streams that wear its flanks must still, in great part, follow the course of the primal valleys. So that, in the actual form of any mountain peak, there must usually be traceable the shadow or skeleton of its former self; like the obscure indications of the first frame of a war-worn tower, preserved, in some places, under the heap of its ruins, in others to be restored in imagination from the thin remnants of its tottering shell; while here and there, in some sheltered spot, a few unfallen stones retain their Gothic sculpture, and a few touches of the chisel, or stains of color, inform us of the whole mind and perfect skill of the old designer. With this great difference, nevertheless, that in the human architecture the builder did not calculate upon ruin, nor appoint the course of impendent desolation; but that in the hand of the great Architect of the mountains, time and decay are as much the instruments of His purpose as the forces by which He first led forth the troops of hills in leaping flocks:--the lightning and the torrent, and the wasting and weariness of innumerable ages, all bear their part in the working out of one consistent plan; and the Builder of the temple for ever stands beside His work, appointing the stone that is to fall, and the pillar that is to be abased, and guiding all the seeming wildness of chance and change, into ordained splendors and foreseen harmonies. Sec. 9. Mountain masses, then, considered with respect to their first raising and first sculpture, may be conveniently divided into two great groups; namely, those made up of beds or layers, commonly called stratified; and those made of more or less united substance, called unstratified. The former are nearly always composed of coherent rocks, the latter of crystallines; and the former almost always occupy the outside, the latter the centre of mountain chains. It signifies, therefore, very little whether we distinguish the groups by calling one stratified and the other unstratified, or one "coherent" and the other "crystalline," or one "lateral" and the other "central." But as this last distinction in position seems to have more influence on their forms than either of the others, it is, perhaps, best, when we are examining them in connection with art, that this should be thoroughly kept in mind; and therefore we will consider the first group under the title of "lateral ranges," and the second under that of "central peaks." [Illustration: FIG. 8.]