of the
mound is exposed, it exhibits moraine-matter--detritus pulverised by
the ice, with boulders entangled in it. It stretched quite across the
valley, and at one time dammed the river up. But now the barrier is
cut through, the stream having about one-fourth of the moraine to its
right, and the remaining three-fourths to its left. Other moraines of
a more resisting character hold their ground as barriers to the
present day.

In the Val di Campo, for example, about three-quarters of an hour from
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 resisted 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 mould.

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 hollowing out of the rock by the
eddies of the water is here quite manifest. A few minutes' walk
upwards brings us to the end of the gorge; and behind it we have the
usual indications 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 became 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 unf