260 ACTION OF TOKRENTS. 



deposits at their points of emergence, and the centre of the accn- 

 mnlation in the case of very small torrents is not unfrequentlj a 

 hundred feet high, and sometimes very mnch more. 



The deposits of the torrent which has scooped out the Xant- 

 zen Thai, a couple of miles below Brieg in the Yalais, have 

 built up a semicircular hillock, which most travellers by the Sim- 

 plon route pass over without notice, though it is httle inferior in 

 dimensions to the great cones of dejection described by Blanqui. 

 The principal course of the torrent having been — I know not 

 whether spontaneously or artificially — diverted towards the west, 

 the eastern part of the hill has been gradually brought under cul- 

 tivation, and there are many trees, fields and houses upon it ; 

 but the larger western part is furrowed with channels diverging 

 from the summit of the deposit at the outlet of the Xantzen 

 Thai, which serve as the beds of the watercourses into which the 

 torrent has divided itseK. All this portion of the hillock is sub- 

 ject to inundation after long and heavy rain, and when I saw it 

 in the great flood of October, 1866, almost its whole surface 

 Beemed covered with an unbroken sheet of rushing water. 



The semi-conical deposit of detritus at the mouth of the Litz- 

 nerthal, a lateral branch of the valley of the Adige, at the point 

 where the torrent pours out of the gorge, is a thousand feet high, 

 and, measuring along tlie axis of the principal current, two and a 

 half miles long.* The solid material of this hillock — which it is 

 hardly an exaggeration to call a mountain, the work of a single 

 insiomificant torrent and its tributaries — ^includino; what the river 

 which washes its base has carried off in a comparatively few years, 

 probably surpasses the mass of the stupendous pyramid of the 

 Matterhom. 



In valleys of ancient geological formation, which extend into 

 the very heart of the mountains, the streams, though rapid, have 

 often lost the true torrential character, if indeed they ever pos- 

 sessed it. Their beds have become approximately constant, and 

 their walls no longer crumble and fall into the waters that wash 

 their bases. The torrent-worn ravines, of which I have spoken, 

 are of later date, and belong more properly to what may be called 

 the crust of the Alps, consisting of loose rocks, of gravel, and of 



* SoNKLAK, Die OeUthaler Oebirgsgruppe, 1861, p. 231. 



