BE-STOCKING DEKUDED WOODLANDS. 191 



their joint operation towards the final result. Although 

 man is unable to avert such events entirely, he can lessen 

 their ravages by timely taking up the battle against the 

 single, isolated forces, and thus prevent their dangerous 

 combination. This observation led human genius to 

 the discovery of means and ways to moderate the disas- 

 trous effects of violent storms upon the physical condi- 

 tion of mountains, after avarice or imprudence of man 

 had denuded their summits and steep slopes of the 

 forest vegetation, thereby allowing the formation of tor- 

 rents which carried away the earth, and rendered the 

 restoration of the mountain forests nearly impossible. 

 French engineers and experts in forestry matters have, 

 during the last one hundred years, devoted much time 

 in ascertaining the causes of the origin and dimension of 

 the torrents by which the washing-down of the mountain 

 soil into the valleys and the disastrous, nearly every 

 year, recurring imxndations in the mountainous parts of 

 South France were brought about. These investigations 

 led to the following theses, the correctness of which is 

 now fully established : 



1. If the mountains are covered with forests, the 

 formation of torrents is impossible. 



2. The deforestation of the mountains surrenders the 

 soil to the formation of torrents. 



3. By extending the forest area, we do away with tor- 

 rents, and promote an increased formation of natural 

 water reservoirs. 



4. The disappearance of a forest redoubles the vehe- 

 mence of torrents, and even may resuscitate extinct 

 ones. 



We will now consider the various phases in which the 

 accumulated mountain waters may be prevented from 

 doing harm to plant growth, and may even be turned 

 so as to promote forest vegetation. 



