42 RfisuM:^ OP surell's study of 



not the first to advocate its application. Until the natural history of these 

 torrents was studied and made known special applications were in use, but 

 a remedial cure seems not to have been attempted. What was tried was to 

 prevent inundations, and the washing away of lands, and the deposit of 

 detritus on fertile land. What is now being done is to extirpate the 

 occasion of these. 



In the low-lying plains, at some distance from the mountains, it was the 

 destructive effects of inundations which commanded attention ; in the Alps 

 it was the ravages of torrents on the land which did this. 



" The torrent which dashes a great body of water over very steep slopes 

 (says Surell) undermines and eats away with fury the base 6f the banks. 

 These fall in, and little by little pull down towards the bed the adjoining 

 property, which is finally engulfed by the waters. As the banks are 

 generally very deep their fall brings in its train effects the results of which 

 extend far from the spot. All the surrounding land is disturbed. Some 

 portions undermined subside, others slip, others break away, leaving deep 

 crevices. Along the two banks of the torrent may be seen large chinks or 

 rents running parallel to the bed. These subsidences, these rents, and this 

 disturbance spread from place to place, repeat themselves to incredible 

 distances, and end by including the whole sides of the mountain within the 

 range of the effects. There are many quarters which can be named which 

 the erosion of torrents have made so unstable that it has become impossible 

 to build upon them. On the left bank of the torrent Les Moulettes there 

 may be seen houses belonging to the village of Les Andrieux, which have 

 been rent at a distance of more than 800 mfetres from the bed. On the 

 highway. No. 91, opposite Les ArdoisiSres, we have an example of a consi- 

 derable revers of a mountain eaten away by the Romanohe and tormented 

 by continual movements of the soil. The instability of the soil has com- 

 pelled many families to abandon cottages situated at a great distance from 

 the river. One could scarcely comprehend that that could be the cause of 

 movements so remote, if the analogy of facts and other evidences had not 

 proved it to be so in a manner the most irresistible." 



Numerous cases are referred to in a note followed up with the remark, — 

 " I have thought it right to multiply citations, because the cause of these 

 movements has been often misapprehended, and notably so in the case last 

 mentioned. The inhabitants attribute it to some particular character of the 

 ground. Having under their eyes only the case of their own locality, they 

 are not aware that it is a phenomenon quite general and common to all 

 torrents." 



He specifies movements of the soil in the mountain of Saint Sauveur, 

 over against Embrun, brought about by the torrent of Vach^res, and by a 

 great many other torrents of the third class, similar movements in the 

 district of Vabries, mined by the torrent Crevoux on the left bank, and in 

 the district of Villard Saint Andr6, by the same torrent on its right bank ; 

 it is stated that this ground had become more mobile subsequently to the 

 formation of a canal for irrigation ; accounts are given of simiiai movements 

 attributable to the torrent of Sainte-Marthe, near Caley^res, in connection 

 with which it is stated that there was there a mill apparently on the point 

 of being engulfed, and of movements attributable to the torrent Merdanel, 

 above Chadenas j and it is stated that very violent movements have been 

 observed in the portions of the Diveset, of Labdoux, of the Rabioux, of 



