§ 13. Now, that such a structure is the best and wisest possible, is, indeed, sufficient reason for its existence; and to many people it may seem useless to question farther respecting its origin. But I can hardly conceive any one standing face to face with one of these towers of central rock, and yet not also asking himself, Is this indeed the actual first work of the Divine Master on which I gaze? Was the great precipice shaped by His finger, as Adam was shaped out of the dust? Were its clefts and ledges carved upon it by its Creator, as the letters were on the Tables of the Law, and was it thus left to bear its eternal testimony to His beneficence among these clouds of heaven? Or is it the descendant of a long race of mountains, existing under appointed laws of birth and endurance, death and decrepitude?

§ 14. There can be no doubt as to the answer. The rock itself answers audibly by the murmur of some falling stone or rending pinnacle. It is not as it was once. Those waste leagues around its feet are loaded with the wrecks of what it was. On these, perhaps, of all mountains, the characters of decay are written most clearly; around these are spread most gloomily the memorials of their pride, and the signs of their humiliation.

"What then were they once?"

The only answer is yet again,—"Behold the cloud."

Their form, as far as human vision can trace it, is one of eternal decay. No retrospection can raise them out of their ruins, or withdraw them beyond the law of their perpetual fate. Existing science may be challenged to form, with the faintest color of probability, any conception of the original aspect of a crystalline mountain; it cannot be followed in its elevation, nor traced in its connection with its fellows. No eyes ever "saw its substance, yet being imperfect;" its history is a monotone of endurance and destruction: all that we can certainly know of it, is that it was once greater than it is now, and it only gathers vastness, and still gathers, as it fades into the abyss of the unknown.

§ 15. Yet this one piece of certain evidence ought not to be altogether unpursued; and while, with all humility, we shrink from endeavoring to theorize respecting processes which are concealed, we ought not to refuse to follow, as far as it will lead us, the course of thought which seems marked out by conspicuous and consistent phenomena. Exactly as the form of the lower mountains seems to have been produced by certain raisings and bendings of their formerly level beds, so the form of these higher mountains seems to have been produced by certain breakings away from their former elevated mass. If the process appears in either case doubtful, it is less so with respect to the higher hills. We may not easily believe that the steep limestone cliffs on one side of a valley, now apparently secure and steadfast, ever were united with the cliffs on the other side; but we cannot hesitate to admit that the peak which we see shedding its flakes of granite, on all sides of it, as a fading rose lets fall its leaves, was once larger than it is, and owes the present characters of its forms chiefly to the modes of its diminution.

§ 16. Holding fast this clue, we have next to take into consideration another fact of not less importance,—that over the whole of the rounded banks of lower mountain, wherever they have been in anywise protected from the injuries of time, there are yet visible the tracks of ancient glaciers. I will not here enter into detail respecting the mode in which traces of glaciers are distinguishable. It is enough to state that the footmark, so to speak, of a glacier is just as easily recognizable as the trail of any well-known animal; and that with as much confidence as we should feel in asserting that a horse had passed along a soft road which yet retained the prints of its shoes, it may be concluded that the glaciers of the Alps had once triple or quadruple the extent that they have now; so that not only the banks of inferior mountains were once covered with sheets of ice, but even the great valley of the Rhone itself was the bed of an enormous "Mer de Glace," which extended beyond the Lake of Geneva to the slopes of Jura.[55]

§ 17. From what has already been noted of glacier action, the reader cannot but be aware that its universal effect is to round and soften the contours of the mountains subjected to it; so that a glacier may be considered as a vast instrument of friction, a white sand-paper, applied slowly but irresistibly to all the roughnesses of the hill which it covers. And this effect is of course greatest when the ice flows fastest, and contains more embedded stones; that is to say, greater towards the lower part of a mountain than near its summit.

Fig. 24.

Suppose now a chain of mountains raised in any accidental form, only of course highest where the force was greatest,—that is to say, at the centre of the chain,—and presenting any profile such as a, [Fig. 24]; terminated, perhaps, by a broken secondary cliff, and the whole covered with a thick bed of glacier, indicated by the spotted space, and moving in the direction of the arrows. As it wears away the mountain, not at all at the top, but always more and more as it descends, it would in process of time reduce the contour of the flank of the hill to the form at b. But at this point the snow would begin to slide from the central peak, and to leave its rocks exposed to the action of the atmosphere. Supposing those rocks disposed to break into vertical sheets, the summit would soon cleave itself into such a form as that at x; and the flakes again subdividing and falling, we should have conditions such as at y. Meanwhile the glacier is still doing its work uninterruptedly on the lower bank, bringing the mountain successively into the outlines c and d, in which the forms x and y are substituted consecutively for the original summit. But the level of the whole flank of the mountain being now so much reduced, the glacier has brought itself by its own work into warmer climate, and has wrought out its own destruction. It would gradually be thinned away, and in many places at last vanish, leaving only the barren rounded mountains, and the tongues of ice still supplied from the peaks above.