1st. Suppose a series of beds raised in the condition _a_, Fig. 13, the lowest soft, the uppermost compact; it is evident that the lower beds would rapidly crumble away, and the compact mass above break for want of support, until the rocks beneath had reached a slope at which they could securely sustain themselves, as well as the weight of wall above, thus bringing the hill into the outline _b_. [Illustration: FIG. 14.] 2. Slope above wall. 2d. If, on the other hand, the hill were originally raised as at _c_, the softest beds being at the top, these would crumble into their smooth slope without affecting the outline of the mass below, and the hill would assume the form _d_, large masses of debris being in either of these two cases accumulated at the foot of the slope, or of the cliff. These first ruins might, by subsequent changes, be variously engulfed, carried away, or covered over, so as to leave nothing visible, or at least nothing notable, but the great cliff with its slope above or below it. Without insisting on the evidences or probabilities of such construction, it is sufficient to state that mountains of the two types, _b_ and _d_, are exceedingly common in all parts of the world; and though of course confused with others, and themselves always more or less imperfectly developed, yet they are, on the whole, singularly definite as classes of hills, examples of which can hardly but remain clearly impressed on the mind of every traveller. Of the first, _b_, Salisbury Crags, near Edinburgh, is a nearly perfect instance, though on a diminutive scale. The cliffs of Lauterbrunnen, in the Oberland, are almost without exception formed on the type _d_. 3. Slope and wall alternately. 3d. When the elevated mass, instead of consisting merely of two great divisions, includes alternately hard and soft beds, as at _a_, Fig. 14, the vertical cliffs and inclined banks alternate with each other, and the mountain rises on a series of steps, with receding slopes of turf or debris on the ledge of each, as at _b_. At the head of the valley of Sixt, in Savoy, huge masses of mountain connected with the Buet are thus constructed: their slopes are quite smooth, and composed of good pasture land, and the cliffs in many places literally vertical. In the summer the peasants make hay on the inclined pastures; and the hay is "carried" by merely binding the haycocks tight and rolling them down the slope and over the cliff, when I have heard them fall to the bank below, a height of from five to eight hundred feet, with a sound like the distant report of a heavy piece of artillery. [Illustration: FIG. 15.]