The overflowings thereof wash away the dust of the earth.
Job xiv. 18.
The mighty fortresses of the earth, which seem so imperishable, so majestic in their strength, and have from time immemorial received their title of "the everlasting hills," are nevertheless undergoing constant change and decay. They cannot abide for ever. Those waste leagues around their feet are loaded with the wrecks of what once belonged to them; they are witnesses to the victory of the hostile forces that are for ever contending with them, and pledges of a final triumph. To those who will read their story, mountains stand like old dismantled castles, mere wrecks of ruined masonry, that have nearly crumbled away, telling us of a time when all their separate peaks and crags were one solid mass, perhaps an elevated smooth plateau untouched by the rude hand of time.
Let us now inquire how the work of destruction is accomplished. Referring back to our illustration of the cathedral, given in chap. v., pp. 143-147, the question we have now to consider is, how the mountains were carved out into all these wonderful features of crag and precipice, peak and pass, which are such a source of delight to all who care for scenery. This work we included in the one word "ornamentation." What, then, are the tools which Nature uses in this work of carving out the hills? What are her axes and hammers, her chisels and saws?
This question, like many others, must be answered by observing what takes place at the present day. It is scarcely necessary to say that mountains and mountain-ranges are not simply the result of upheaval, though they have been upheaved. If that were so, they would probably appear as long smooth, monotonous ridges, with no separate mountain masses, no peaks, no glens or valleys; in some cases they might appear as simply elevated and smooth plateaux. Such mountains, if we may so call them, would be almost as uninteresting as the roof of a gabled house down which the rain finds its way in one smooth continuous sheet.
Mountains, reaching as they do into the higher regions of the atmosphere, where the winds blow more fiercely than on the plains below, storms rage more violently, and the extremes of heat and cold are more severe,—in fact, where every process of change and decay seems quickened,—suffer continually at the hands of the elements.
"Death must be upon the hills, and the cruelty of the tempests smite them, and the thorn and the briar spring up upon them; but they so smite as to bring their rocks into the fairest forms, and so spring as to make the very desert blossom as the rose."[23]
Nature never leaves them alone, never gives them a brief armistice in the long war that she wages against them. She is a relentless enemy, ever on the move, and ever varying her methods of attack. Now she assails them openly with her storm-clouds, and pelts them furiously with driving rain; now we hear the thunder of her artillery, as she pierces their crests with strange electric darts of fire; now she secretly undermines their sides with her hidden sources of water, till whole villages are destroyed by some fearful fall of overhanging rocks (see chapter iii., pages [96]-[101]). Her winds and gentle breezes are for ever at work on their surfaces, causing them to crumble into dust much in the same way as iron turns to rust.
Again, she heats them by day and then chills them suddenly at night, under the cold starry sky, so that they crack under the strain of expanding and contracting. Now she splits them with her ice-wedges; now she furrows their sides with the dashing torrents and running streams; and yet again she wears them gently down with her glaciers, and carries away their débris—the token of her triumph—on those icy streams, as conquering armies carry the spoils in procession.
This is, briefly, her mode of warfare; these are some of her tools, wind, rain, frost, snow, heat and cold, streams, rivers, and glaciers. Lightning does occasionally break off portions of a cliff or a mountain-peak; but compared to the others, this agent is not very important.