I go SCENERY OF SWITZERLAND. 
steep indeed as the nature of the material will per- 
mit, and the valley is in the shape of a V with little, 
if any, flat bottom. The water moreover continually 
eats back into the higher ground. The character of 
the valley depends greatly on that of the strata, 
being narrower where they are hard and tough, 
broader on the contrary where they are soft, so that 
they crumble more easily into the stream under the 
action of the weather. Fig. 46. 
In several cases indeed the Swiss rivers run 
through gorges of great depth, and yet very narrow, 
even in some places with overhanging walls. The 
Via Mala, which leads from the green meadows of 
Schams (Sexamniensis, from its six brooks) to Thusis, 
is about five miles in length with a depth of nearly 
500 metres, and very narrow, in one place not more 
than 9 to 15 metres in breadth. 
The gorges of the Aar, of the Gorner, of the 
Tamina at Pfaffers, of the Trient, have a similar 
character. These were formerly supposed to be 
fissures due to upheaval. They none of them how- 
ever present a trace of fracture, marks of water action 
can in places be seen from the base to the summit, 
and there can be no doubt that they have been cut 
through by the rivers. 
In certain cases indeed we have conclusive 
