tefi HIGH At* a. - 259 



reprinting, from a report presented in 1869 to the Oonseit General des 

 Mantes Alpes, by M. Gentil, Ingenieur en chef des ponts et chaussees, the 

 following passage : — ' Torrents are one of the most disastrous plagues of 

 the High Alps ; the cones de dejection invade the valleys, bury under their 

 heaps the cultivated ground, end in annihilating every kind of cultivation, 

 and hunt the inhabitants away from the country ; and at the same time 

 the erosions occasioned by them destroy the sides of the mountains ; and 

 thus is destroyed at one and the same time all the value of the mountain 

 and the value of the plain. 



" ' The embankments attempted on the cones de dejection at the issue of 

 the gorges, by which come down the materials carried off by the waters 

 from the higher-lying lands, have always failed, or at best the effects pro- 

 duced by them have been but precarious. The dikes in a few years have 

 disappeared under the rubbish from the mountain, 



" ' But the Forest Administration has succeeded, by the consolidation of 

 the soil, in the creation of a robust vegetation on the flanks of the bassins 

 de reception. The results are assured : the case of the works at La Batie, 

 at Sainte-Marthe, at Eesail, has demonstrated most manifestly and most 

 indisputably, that it is quite possible not only to arrest dejections, but also 

 to re-establish vegetation on mountains the most ravaged by these torrents. 



'" It is not required of me here to show by what means the Forest Adminis- 

 tration has succeeded in extinguishing the torrents. I confine myself to 

 specifying the results of these operations. These results, in regard to the 

 valleys, to^the lands there, and to the roads by which they are traversed, 

 are remarkable in the extreme, and it is now required of me to point out 

 these to the Departmental Administration. 



" ' From the time that the soil in the bassin de reception is consolidated, 

 and by plantings and sowings and works of the Forest Administration the 

 soil is fixed, material is no longer torn away and thrown into the current 

 which transports it to the lower-lying parts. The waters assume in some 

 measure a regular regime, they come clear and free from mud upon the 

 cones de dejections, they dig out there a stable bed for themselves by carry- 

 ing away the less ponderous material ; at this stage embankment becomes 

 possible in the valley, and it is practicable at little expense to keep in one 

 unchanging direction the flow of waters which no longer carry away the 

 stones. Properties along the banks are then securely protected ; they 

 are no more exposed to a sudden disaster such as those of which we have 

 so many examples ; they recover with this security their money value ; and 

 the population reassured may count upon their harvests. 



" ' On the other hand^ the fixing of the bed of the current permits the 

 erection of bridges arid aqueducts on the roads and highways ; com- 

 munication is protected against the frequent interruptions to which it was 

 exposed when the torrent was in full activity ; and, in fine — nor is this the 

 least important result of the regeneration of the basin of reception — the 

 principal rivers no longer receive the masses of dejection which encumber 

 their beds and create confusion in times of flood. In illustration of these 

 results, which have been thus referred to in a general and summary way, 

 may be cited the following facts : — ^ 



" ' The torrent of Sainte-Marthe, near Embrun, was threatening to extend 

 its dejections, so as to cover the imperial road, No. 94. A proposal to construct 

 a dike on the left bank had been formally discussed ; the expense of this 

 was estimated at about 4:d;000 francs, and it was considered that it should 



