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long to enable a succession of small shocks, of no greater intensity than those of a modern earthquake, to have acted upon it. The whole strongly impresses us with the idea of a powerful exertion, forcing the limestone and associated beds outwards."—H. T. De La Beche's Theoret. Geology, pp. 113, 114.
In some instances they form a simple curve; in others a series of curves, like so many waves; in others still they are folded over like a half dozen of the letter S joined in a continuous line. The folding, in some localities, is on so great a scale, that the strata must either have been drawn from a distance, or else greatly expanded in length and breadth. In some parts of the Alleghanies the coal series within a half dozen square miles, would, if spread out on a level, cover two or three times that space.
"The most probable condition of contortion appears to be pressure of solid matter on yielding stratified substances, which, while they bend, also slideto a certain extent on the planes of stratification."—H. T. De La Beche's Theoretical Geology, p. 121.
No such softness and pliancy are retained by the stratified or crystallized rocks that now lie beneath the surface;. however far they may be below the line of the sea. Though permeated by moisture, and, when first raised to the atmosphere, far more easily sawn or wrought with the chisel than after the water with which they are charged has evaporated, they yet are not sufficiently flexible to be bent without fracture. As, then, they must have continued in a pliant state till their upheaval was completed and they were moulded into their- present form, it is manifest that their elevation must have taken place rapidly. It cannot have proceeded, as many geologists maintain, by such slow stages, as to have been prolonged through a series of ages. If protracted after emerging from the ocean through even a few years, the heat beneath of the molten mass of granite by which they were forced upwards, and the action of the sun and atmosphere, would have desiccated and hardened them to such a degree as to have rendered them incapable of being bent into curves and folds without breaking into fragments. We have the most decisive evidence, therefore, that their upheaval was accomplished in a brief period; and that the vast round of years which geologists have regarded as requisite to that process, is wholly imaginary.
Their upheaval and subjection in that pliant state to the powerful breakers, waves, and currents of the ocean, explain the denudations which they have undergone. Had they possessed their present hardness when rising through the ocean into the atmosphere, no such immense wearing away and such vast excavations as have been wrought in them would have been possible.
"Of the formations comprising the rocks of this portion of the State, n. and ni., are a limestone and slate stratum, which are at all times more destructible than sandstone; but especially so must they have been in their soft and pulpy state at the time of their elevation from the bed of the ocean in which they were deposited. Hence they have been more deeply excavated than the harder ponderous beds of sandstone, of which formation iv. consists. We accordingly find formations n. and m. always in the deep and nearly level valleys, and iv. in the high and steep mountain ridges. Of the other rocks, formation v. consists chiefly of soft slates and calcareous slates. Formation vi., of limestone, which, like it, was evidently of a very soft consistence when first uplifted, and formation vm. of a mass of slate and argillaceous rocks. This would all be liable to very extensive destruction whenever subterraneous uplifting forces should bring them within the reach of those tremendous currents, which those same uplifting actions set in motion." —H. D. Rodgers's Report on the Geology of Pennsylvania, 1838, p. 41.
The sea does not now wear the solid rocks that lie embosomed in it, or rise from its surface, except in a few positions where exposed to the most powerful breakers and currents; and there what it rends and wears away is scarcely appreciable, compared to the masses that meet the shock of its powerful enginery century after century without yielding. Myriads of ages would have contributed little towards grinding down strata of such hardness, scores, hundreds, and even thousands of feet in thickness, over wide areas, scooping out valleys, and ploughing the broad passages betwixt the hills, in the bottom of which rivers cut their channels. But that immense rending and denudation was the natural result of the rapid upheaval of the strata from a level beneath the sea, in a condition so pliant as to yield to the violent currents and waves which that process itself must have created, and the resistless sweep and dash of oceantempests and storms. Under the impulse of those powerful agents, the parts most elevated would at many points be instantly swept away, and where a whole continent, like that of South America, rose at the same time, so as to cause the ocean to recede with a resistless rush hundreds and thousands of miles, its currents would necessarily tear up and bear off the strata over extensive regions. Instead of vast ages and incalculable periods, a very brief time, therefore, would be ample for the accomplishment of all the great modifications of that class to which the strata have been subjected. The cuttings, accordingly, through hills, the excavations of valleys, and the removal of strata from large districts, and deposit of the detritus in others, are precisely such as would naturally result from the vehement commotion and violent currents of the ocean acting on such susceptible materials. On the prevalent theory, however,
they are wholly inexplicable. If the strata on the tops and sides of the mountains and hills, and on the plains and depressed surfaces, were as hard at their upheaval from the ocean as they now are, no solution could be given of the vast degradation that has taken place at many points in rocky ranges and plateaus, the abrasion of solid masses from wide plains, and the scooping out of deep channels and valleys between the hills, arranged in the same relations to each other, and exhibiting the same outlines as those that are now wrought in yielding soils by deluges and floods that sweep over them.
The soft condition of the strata at their upheaval into the atmosphere, indicates the reasons also of the excavations within a brief period by rivers of their deep channels for miles through rocky strata. Thus the Niagara must naturally have cut its passage back from Lake Ontario to near its present fall in the lapse of a few years; inasmuch as the strata over which it passed were at first so pliant as easily to yield to the powerful impulse of the current and cataract. That that was their state, is indisputable, not only from the fact that the strata generally were un- hardened at their upheaval, but that the same formations on the Helderberg and the Appalachians were actually subjected to curvatures and contortions, that show that under the surge and dash of such a mass of waters as the Niagara, they would have given way