But for the intervention of man and domestic animals, these latter beneficent revolutions would occur more frequently, proceed more rapidly. The new scarped mountains, the hillocks of debris, the plains elevated by sand and gravel spread over them, the shores freshly formed by fluviatile deposits, would clothe themselves with shrubs and trees, the intensity of the causes of degradation would be diminished, and nature would thus regain her ancient equilibrium. But these processes, under ordinary circumstances, demand, not years, generations, but centuries; [Footnote: Where a torrent has not been long in operation, and earth still remains mixed with the rocks and gravel it heaps up at its point of eruption, vegetation soon starts up and prospers, it protected from encroachment. In Provence, "several communes determined, about ten years ago, to reserve the soils thus wasted, that is, to abandon them for a certain time, to spontaneous vegetation, which was not slow in making its appearance."-Becquerel, Des Climats, p. 815.] and man, who even now finds scarce breathing-room on this vast globe, cannot retire from the Old World to some yet undiscovered continent, and wait for the slow action of such causes to replace, by a new creation, the Eden he has wasted. Crushing Force of Torrents. I must here notice a mechanical effect of the rapid flow of the torrent, which is of much importance in relation to the desolating action it exercises by covering large tracts of cultivated ground with infertile material. The torrent, as we have seen, shoots or rolls forwards, with great velocity, masses and fragments of rock, and sometimes rounded pebbles from more ancient formations. Every inch of this violent movement is accompanied with crushing concussion, or, at least, with great abrasion of the mineral material, and, as you follow it along the course of the waters which transport it, you find the stones gradually rounding off in form, and diminishing in size, until they pass successively into gravel, and, in the beds of the rivers to which the torrents convey it, sand, and lastly impalpable slime.