But there is this difference between the action of the earth, [§ 4. Mountains come out from underneath the plains, and are their support.]and that of a living creature, that while the exerted limb marks its bones and tendons through the flesh, the excited earth casts off the flesh altogether, and its bones come out from beneath. Mountains are the bones of the earth, their highest peaks are invariably those parts of its anatomy which in the plains lie buried under five and twenty thousand feet of solid thickness of superincumbent soil, and which spring up in the mountain ranges in vast pyramids or wedges, flinging their garment of earth away from them on each side. The masses of the lower hills are laid over and against their sides, like the masses of lateral masonry against the skeleton arch of an unfinished bridge, except that they slope up to and lean against the central ridge: and, finally, upon the slopes of these lower hills are strewed the level beds of sprinkled gravel, sand, and clay, which form the extent of the champaign. Here then is another grand principle of the truth of earth, that the mountains must come from under all, and be the support of all; and that everything else must be laid in their arms, heap above heap, the plains being the uppermost. Opposed to this truth is every appearance of the hills being laid upon the plains, or built upon them. Nor is this a truth only of the earth on a large scale, for every minor rock (in position) comes out from the soil about it as an island out of the sea, lifting the earth near it like waves beating on its sides.
Such being the structure of the framework of the earth, it is next to be remembered that all soil whatsoever, wherever it is [§ 5. Structure of the plains themselves. Their perfect level, when deposited by quiet water.]accumulated in greater quantity than is sufficient to nourish the moss of the wallflower, has been so, either by the direct transporting agency of water, or under the guiding influence and power of water. All plains capable of cultivation are deposits from some kind of water—some from swift and tremendous currents, leaving their soil in sweeping banks and furrowed ridges—others, and this is in mountain districts almost invariably the case, by slow deposit from a quiet lake in the mountain hollow, which has been gradually filled by the soil carried into it by streams, which soil is of course finally left spread at the exact level of the surface of the former lake, as level as the quiet water itself. Hence we constantly meet with plains in hill districts, which fill the hollows of the hills with as perfect and faultless a level as water, and out of which the steep rocks rise at the edge with as little previous disturbance, or indication of their forms beneath, as they do from the margin of a quiet lake. Every delta—and there is one at the head of every lake in every hill-district—supplies an instance of this. The rocks at Altorf plunge beneath the plain, which the lake has left, at as sharp an angle as they do into the lake itself beside the chapel of Tell. The plain of the Arve, at Sallenche, is terminated so sharply by the hills to the south-east, that I have seen a man sleeping with his back supported against the mountain, and his legs stretched on the plain; the slope which supported his back rising 5000 feet above him, and the couch of his legs stretched for five miles before him. In distant effect these champaigns lie like deep, blue, undisturbed water, while the mighty hills around them burst out from beneath, raging and tossing like a tumultuous sea. The valleys of Meyringen, Interlachen, Altorf, Sallenche, St. Jean de Maurienne; the great plain of Lombardy itself, as seen from Milan or Padua, under the Alps, the Euganeans, and the Apennines; and the Campo Felice under Vesuvius, are a few, out of the thousand instances, which must occur at once to the mind of every traveller.
Let the reader now open Rogers's Italy, at the seventeenth page, and look at the vignette which heads it of the battle of Marengo. It needs no comment. It cannot but carry with it, [§ 6. Illustrated by Turner's Marengo.]after what has been said, the instant conviction that Turner is as much of a geologist as he is of a painter. It is a summary of all we have been saying, and a summary so distinct and clear, that without any such explanation it must have forced upon the mind the impression of such facts—of the plunging of the hills underneath the plain—of the perfect level and repose of this latter laid in their arms, and of the tumultuous action of the emergent summits.
We find, according to this its internal structure, which, I believe, with the assistance of Turner, can scarcely now be misunderstood, that the earth may be considered as divided into three [§ 7. General divisions of formation resulting from this arrangement. Plan of investigation.]great classes of formation, which geology has already named for us. Primary—the rocks, which, though in position lower than all others, rise to form the central peaks, or interior nuclei of all mountain ranges. Secondary—the rocks which are laid in beds above these, and which form the greater proportion of all hill scenery. Tertiary—the light beds of sand, gravel, and clay, which are strewed upon the surface of all, forming plains and habitable territory for man. We shall find it convenient, in examining the truth of art, to adopt, with a little modification, the geological arrangement, considering first, the formation and character of the highest or central peaks; then the general structure of the lower mountains, including in this division those composed of the various slates which a geologist would call primary; and, lastly, the minutiæ and most delicate characters of the beds of these hills, when they are so near as to become foreground objects, and the structure of the common soil which usually forms the greater space of an artist's foreground. Hence our task will arrange itself into three divisions—the investigation of the central mountains, of the interior mountains, and of the foreground.
CHAPTER II.
OF THE CENTRAL MOUNTAINS.
It does not always follow, because a mountain is the highest of its group, that it is in reality one of the central range. The [§ 1. Similar character of the central peaks in all parts of the world.]Jungfrau is only surpassed in elevation, in the chain of which it is a member, by the Schreckhorn and Finster-Aarhorn; but it is entirely a secondary mountain. But the central peaks are usually the highest, and may be considered as the chief components of all mountain scenery in the snowy regions. Being composed of the same rocks in all countries, their external character is the same everywhere. Its chief essential points are the following.
Their summits are almost invariably either pyramids or wedges. Domes may be formed by superincumbent snow, or [§ 2. Their arrangements in pyramids or wedges, divided by vertical fissures.]appear to be formed by the continuous outline of a sharp ridge seen transversely, with its precipice to the spectator; but wherever a rock appears, the uppermost termination of that rock will be a steep edgy ridge, or a sharp point, very rarely presenting even a gentle slope on any of its sides, but usually inaccessible unless encumbered with snow.