TOERBNTB OF THE HIGH ALPS. 43 



Bosoodon, of the Ruisseauioux (Lauterat), &o., &c. And he goes on to say, 

 — " There are whole villages built in hassins de receptions which are threat- 

 ened to be engulfed in this manner by the torrents. Every year the torrent 

 acquires more of the ground, and the village abandons to it several cottages. 

 These facts demonstrate the encroaching march of these water-courses. 

 Little threatening at first, they increase in size, they extend themselves, 

 and soon they reach the habitations built without mistrust at a great 

 distance from their banks. There was, before the thirteenth century, on 

 the borders of the Ralioux, near to Ch^teaureux, a monastery inhabited by 

 the Benedictines. At a later period the monks deserted it through fear of 

 its being engulfed, and now one sees the ruins suspended in the middle of the 

 river's bank. 



" There are threatened with a similar fate the village of Lacluse, by the 

 Lab6oux (D6voluy) ; that of the Hiferes, by the Mauriand ; that of the 

 Arvieux, by the Moiilettes j the hamlet of the Marches, and the hamlet of 

 the Maisonnasses, by the torrent Rousensasse, on the right bank of the 

 Drac (Champsam)." 



Having specified these as villages or hamlets exposed to a fate similar to 

 that of the Benedictine Monastery, whose history is given, he goes on to say, 



" Most frequently the undermining of the soil is done gradually, and this 



action is the more slow and the more regular in proportion to the extent ot 

 the region. The great mass of ground deadens the movements, and 

 impresses them with a kind of continuity. But at other times also the soil 

 detaches itself suddenly, as if through the effects of a blow. It is thus that 

 in the valleys of the D6voluy, some years ago, a fragment of the mountain 

 Auroux, covered with cultivated fields, precipitated itself, in one block, into 

 the gorge of the torrent Lab6oux. The commotion occasioned by this 

 frightful fall was felt at a considerable distance in the village Lacluse, and 

 the inhabitants attributed it to an earthquake. The cause was no other 

 than erosion by the torrent, which had sapped the base of the ground. 

 " This may demand some explanation. 



"Many lands are formed of parallel banks, disposed in flat layers and 

 raised up on gi-eat inclinations. Often an interposed bed, more soluble or 

 less tenacious, is decomposed or disintegrated by infiltration. If it happens 

 at the same time that the under banks be attacked by the current at the 

 foot, an enormous weight of ground finds itself suspended over an abyss ; 

 the force of adhesion being weakened, it no longer suffices to keep together 

 this mass and to attach it to the body of the mountain ; it is then detached 

 in a mass, and it slides over the surface of the decomposed bed as on an 

 inclined plain. One may indeed see similar land-slips frequently occurring 

 in the limestones of the lias formation, which decompose with the greatest 

 facility, and which often present a schistose stratification; this kind of 

 ground extensively prevails here. In other cases the grounds have been 

 formed of the debris of the upper parts of the mountains ; they compose a 

 rough mass without stratification, and most frequently without consistency, 

 covering the stratified nucleus of the mountain, and forming on its surface 

 beds of great thickness. It rarely happens that a bassin, de reception does 

 not contain within its circuit a large strip of this quite recent formation, for 

 it is into the scooped out parts that the debris have had to roll and rest. 

 And one may easily see that the erosions which take place in such grounds, 

 when they attack the foundation of veiy high banks, must force the soil to 

 detach itself in great masses ; and the fractures will take the form of 



