CRUSHING FORCE OF TORRENTS. 263 



But for the intervention of man and domestic animals, these 

 latter beneficent revolutions would occur more frequently, pro- 

 ceed 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 equihbrium. But these processes, under ordinary 

 circumstances, demand, not years, generations, but centuries;* 

 and man, who even now finds scarce breathing-room on this vast 

 globe, can not retire from the Old World to some yet xmdiscov- 

 ered continent, and wait for the slow action of such causes to re- 

 place, 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 forward, 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 crush- 

 ing 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, 

 into sand, and, lastly, into impalpable slime. 



There are few operations of nature where the effect seems more 

 disproportioned to the cause than in this crushing and comminu- 



tinue, this declivity, now fertile, wiU be ruined, like so many others." — Ibid., 

 p. 155. 



* 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, if protected from encroachment. In Provence, 

 "several communes determined, about ten years ago, to reserve the soUs 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. 315. 



