] 78 FRA OMENTS F SCIENCE. 



Pisciadello, there is a moraine composed of large boulders, 

 which interrupt the course of a river and compel the water 

 to fall over them in cascades. They have in great part re- 

 sisted its action since the retreat of the ancient glacier 

 which formed the moraine. Behind the moraine is a lake- 

 bed, now converted into a level meadow, which rests on a 

 deep layer of mold. 



At Pontresina a very fine and instructive gorge is to be 

 seen. The river from the Morteratsch glacier rushes 

 through a deep and narrow chasm which is spanned at one 

 place by a stone bridge. The rock is not of a character to 

 preserve smooth polishing; but the larger features of 

 water-action are perfectly evident from top to bottom. 

 Those features are in part visible from the bridge, but still 

 better from a point a little distance from the bridge in the 

 direction of the upper village of Pontresina. The hollow- 

 ing out of the rock by the eddies of the water is here quite 

 manifest. A few minutes' walk upward brings us to the 

 end of the gorge; and behind it we have the usual indica- 

 tions of an ancient lake, and terraces of distinct water 

 origin. From this position indeed the genesis of the 

 gorge is clearly revealed. After the retreat of the ancient 

 glacier, a transverse ridge of comparatively resisting 

 material crossed the valley at this place. Over the lowest 

 part of this ridge the river flowed, rushing steeply down to 

 join at the bottom of the slope the stream which issued 

 from the Rosegg glacier. On this incline the water be- 

 came a powerful eroding agent, and finally cut the channel 

 to its present depth. 



Geological writers of reputation assume at this place the 

 existence of a fissure, the " washing out" of which resulted 

 in the formation of the gorge. Now no examination of 

 the bed of the river ever proved the existence of this fissure; 

 and it is certain that water, particularly when charged 

 with solid matter in suspension, can cut a channel through 

 un fissured rock. Cases of deep cutting can be pointed 

 out where the clean bed of the stream is exposed, the rock 

 which forms the floor of the river not exhibiting a trace of 

 fissure. An example of this kind on a small scale occurs 

 near the Bernina Gasthaus, about two hours from Pont- 

 resina. A little way below the junction of the two 

 streams from the Bernina Pass and the Hen thai the river 

 flows through a channel cut by itself, and 20 or 30 feet in 



