STATEITENT BY MS UABSH. 233 



the Hinter Rhein and its mild tribataries, enormous quantities of 

 rock, in blocks and boulders. In fact, the masses hurled into it in a 

 single flood like those of 1868 would probably fill it up, at its narrow 

 points, to the level of the road 400 feet above its bottom, were not 

 the stones crushed and carried oflF by the force of the current. Yet 

 below the outlet at Thusis only small rounded boulders, pebbles, and 

 gravel, not rock, are found in the bed of the river. The Swiss 

 glaciers bring down thousands of cubic yards of hard rook every 

 season. Where the glacier ends in a plain or wide vaUey, the rocks 

 are accumulated in a terminal moraine, but in numerous instances 

 the water which pours firom the ice-river has force enough to carry 

 down to larger streams the masses delivered by the glacier, and there 

 they, with other stones washed out from the earth by the current, 

 are ground down, so that few of the affluents of the Swiss lakes 

 deliver into them anything but fine sand and slime. 



" Great rivers carry no boulders to the sea, and, in feet, receive 

 none firom their tributaries. Lombardini found, twenty years ago, 

 that the mineral matter brought down to the Po by its tributaries 

 was, in general, comminuted to about the same degree of fineness as 

 the sands of its bed at their points of discharge. In the case of the 

 Trebbia, which rises high in the Apennines and empties into the Po 

 at Placenza, it was otherwise, that river rolling pebbles and coarse 

 gravel into the channel of the principal stream. The banks of the 

 other affluents — exeeptii^ some of those which discharge their waters 

 into the great lakes — ^then either retained their woods, or had been so 

 long clear of them that the torrents had removed most of the disin- 

 tegrated and loose rock in their upper basins. The valley of the 

 Trebbia had been recently cleared, and aU the forces which tend to 

 the degradation and transportation of rock were in full activity." Of 

 the transporting power of water he writes : " The geographical effects 

 of the action of torrents are not confined to erosion of earth and com- 

 minution of rook ; for they and the rivers to which they contribute 

 transport the debris of the mountains to lower levels, and spread them 

 out over the dry land and the bed of the sea, thus forming aUuviad 

 deposits, sometimes of a beneficial, sometimes of an injurious, 

 character, and of vast extent. 



" A mountain rivulet swollen by rain or melted snow, when it 

 escapes from, its usual channel and floods the adjacent fields, naturally 

 deposits pebbles and gravel upon them ; but even at low water, if, of 

 course, it is long enough for its grinding action to have fuU scope, it 

 tnraaports the solid material with which it is charged to some larger 



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