] 78 PR A GMENTS OF 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 Kosegg 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 
unfissured 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 
