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Updated: May 14, 2025
These materials, driven along by the stream, become eroding tools of very considerable energy. As will be seen when we shortly come to describe waterfalls, the potholes formed at those points afford excellent evidence as to the capacity of stream-impelled bits of stone to cut away the firmest bed rocks.
Reestablished contact with the world brightened and humanized him, acting with an eroding effect on a surface hardened by years of lawless roving. In his voluntary exile he had not looked for or wanted the company of his fellows. Now he began to soften under it, shift his viewpoint from that of the all-sufficing individual to that of the bonded mass from which he had so long been an alien.
Before he had gone the first two miles of his hour's journey, the twilight caught the rocky hills and twisted them into those monstrous revelations of physiognomies they barely take the trouble to conceal even in the daytime. And, while he well understood the eroding agencies that have produced them, there yet rose in his mind a deeper interpretation lurking just behind their literal meanings.
In the Metamorphoses his views regarding the interchange of land and sea, the effects of running water in eroding valleys, the growth of deltas, the effect of earthquakes in burying cities and diverting streams from their sources, are remarkable anticipations of doctrines now generally held.
Here, in Carboniferous times, grew the gigantic fern-like trees, the Sigillaria and Lepidodendron, whose petrified trunks, for aeons buried beneath the deposit of the Permian seas, and then, during other aeons, slowly uncovered by the gentle action of the eroding rains, we saw scattered on the ground.
The physical possibilities were arrayed against the project, so steep was the comblike summit on either side, so heavy and tortuous the outcropping rock that served as the bony structure of the great mountain mass. True, the river pierced it, the denudation of solid sandstone cliffs, a thousand feet in height, betokening the untiring energy of the eroding currents of centuries agone.
An instance that fell under my own observation, in 1857, will serve to show something of the eroding and transporting power of streams which, in these respects, fall incalculably below the torrents of the Alps.
The general conformation of the basin, as well as the moraines laid along the top of the walls, and the grooves and scratches on the bottom and sides, indicate in the most unmistakable manner the direction pursued by this mighty ice-river, its great depth, and the tremendous energy it exerted in thrusting itself into and out of the basin; bearing down with superior pressure upon this portion of its channel, because of the greater declivity, consequently eroding it deeper than the other portions about it, and producing the lake-bowl as the necessary result.
They are but a short distance apart, and are in the same box canyon. This ruin is perched on the top of a talus which has fallen from the cliff above, and is visible for some distance above the trees, as one penetrates the canyon. It is built to the side of a perpendicular wall of rock which, high above its tallest walls, arches over it, sheltering the walls from rain or eroding influences.
Constantly the river is destroying and rebuilding its alluvial deposits, here cutting and there depositing along its banks, here eroding and there building a bar, here excavating its bed and there filling it up, and at all times carrying the material picked up at one point some distance on downstream before depositing it at another.
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