I9II.] STEVEXSOX— FORMATION OF COAL BEDS 521 



renders the mass almost jelly-like. A winter of heavy snows, fol- 

 lowed by an unusually warm spring, leads to abrupt swelling of the 

 water and the soft mass is swept out over the surface of the cone, 

 flowing like a flood of lava. Such were the conditions here. A 

 village, la Chapelle, had been built: in 1752, the torrent washed out 

 a vast mass of rock and debris, which covered everything to a depth 

 of 15 to 20 feet, completely burying the hamlet. 



In a broad valley, the effects of the torrent's work are confined 

 to the cone, but conditions are dift'erent where the valley is narrow. 

 A few years prior to the disaster at la Chapelle, another cone was 

 formed in the Arc valley between Saint-Andre and Saint-Michel. 

 The river was dammed and a lake was the result. The inhabitants 

 of a drowned hamlet endeavored to make a canal through the dam, 

 but the great fragments foiled them and the river was left to make 

 its own canal. Dc Luc visited the locality several times. When he 

 last saw it, the river had filled the lake with debris, through which it 

 flowed gently, while above and below it foamed amid masses of 

 rock. De Luc notes with some interest that on the other side of the 

 valley, opposite la Chapelle, a torrent was still at work, building its 

 cone. Each spring saw the surface covered by a flood, bringing 

 down new material. Yet the trees, which had gained place and had 

 sent their roots down amid the rock- fragments, maintained them- 

 selves against the rushing waters, laden with rocks and debris, and 

 inhabitants of the region gathered fagots there. 



Similar phenomena are familiar to all students of mountainous 

 areas. Dejection cones, some of them enormous, are numerous 

 along the Rhone from A'iege to Alartigny. The flood additions are 

 distinct, several of the cones being deposited by streams with fall 

 of more than 250 feet per mile. Except where new channels had 

 been cut, the trees growing on the surface of the cones are appar- 

 ently uninjured, though in some cases they have been bent by blocks 

 of rock, whose advance they had checked. The valley of the Adige 

 between Botzen and Rovereto presents many illustrations of similar 

 type ; in the mountain areas of the western L'nited States such con- 

 ditions are merely commonplace. 



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