2:^8 ACTION OP FORESTS Oi\ THE FLOW 01'' RIVEKtJ. 



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 Nantzen Thai, which serve as the beds of the water 

 courses into which the torrent has divided itself. All this portion of 

 the hillock is subject to inundation after long and heavy rain, and as 

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

 seemed covered with an unbroken sheet of rushing water. 



" The semi-conical deposit of detritus at the mouth of the Litzner- 

 thal, a lateral branch of the valley of the Adige, at the point where 

 the torrent pours out of the gorge, is a thous.md feet high and, 

 measuring along the 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 insignificant 

 torrent and its tributaries — including 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 possessed 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 earth, strewed along the 

 surface of the great declivities of the central ridge, and accumulated 

 thickly between the solid buttresses. But it is on this crust that 

 the mountaineer dwells. Here are his forests, here his pastures, and 

 the ravages of the torrent both destroy ms world, and convert it into 

 a source of overwhelming desolation to the plains below. 



"I do not mean to itssert that all the rocky valleys of the Alps 

 have been produced by the action of torrents resulting from the 

 destruction of the forests. The greater, and many of the smaller 

 channels by which that chain is drained owe their origin to higher 

 causes. There are primitive fissures, ascribable to disruption in up- 

 heaval or other geological convulsion, widened and scarped, and 

 often even polished, so to speak, by the action of glaciers during the 

 ice period, and but little changed in form by running water in 

 later eras. 



" It has been contended that all rivers which take their rise in 

 these mountains originated in torrents. These, it is said, have 

 lowered the summits by gradual erosion, and with the material thus 



