PART II. 



LITERATURE RELATIVE TO ALPINB TORRENTS, AND REMEDIAL MEASURES 



PROPOSED FOR ADOPTION TO PREVENT THE DISASTROUS 



CONSEQUENCES EOLLOTING PROM THEM. 



The subject treated so exhaustively by Surell has commanded the attention 

 of many besides him. 



In 1797 was published an Essai sur la iheorie des torrents et des rivieres, 

 by M. Fabre, an engineer referred to by M. Surell, who had made these his 

 study. The following are translations of some of his propositions relative 

 to them, and to appropriate remedies for them. 



" 144. The destruction of the woods which cover our mountains is the 

 primary cause of the formation of torrents. 



" The reason is apparent. These woods, be they timber forests or be 

 they high coppice, intercept by their foliage and by their branches a 

 considerable portion of the water falling in- rains and in thunderstorms. 

 The remaining portion, which they could not retain, falls only drop by drop 

 at intervals sufficiently long to let them have time to filtrate into the 

 earth. On the other hand, the bed of vegetable earth, which goes on 

 increasing annually, imbibes a considerable quantity of these waters. In 

 fine, tufts of herbage and bush break and destroy at their origin the torrents 

 which might have been formed notwithstanding all these obstructions. 

 The woods being destroyed, the waters of a storm no longer meet with any- 

 thing in their fall to intercept them. They cannot, by reason of their 

 abundance, be absorbed by the ground as they fall. They flow over the 

 surface, and meeting no more tufts which might have broken and divided 

 their courses, they form torrents, as has been said. 



" 145. The clearings on the mountains are the second cause of the formation 

 of torrents. 



" We have shown that a torrent wiU- be formed with so much the more 

 facility in proportion as the matters which compose the mountain shall 

 have less tenacity. Now the clearings, in rendering the earth friable and 

 mobile, have diminished this tenacity ; and thus they have favoured the 

 formation of torrents. 



" One may see from this how ill-advised and inconsiderate was the law 

 given under the ancient regime, which authorised clearings, provided there ' 

 were constructed at intervals walls of support to keep the earth on the 

 slopes of mountains. It was not seen that in a great many countries the 

 people confined themselves to raising two or three crops on a clearing, and 

 that they then abandoned it. It was natural, this being the usage, that the 

 sustaining walls, coming to cost more than the crops would repay, would not 

 be constructed ; and this is just what has happened. But there has already 

 resulted from this, and there will result from it in the future, frightful 

 disasters, as we shall now see. 



