capable
of being thus dissolved will expose a smooth surface after the water
has quitted it; and in the case of the Via Mala it is the polish of
the surfaces and the curved hollows scooped in the sides of the gorge,
which assure us that the chasm has been the work of the river.

About four miles from Tusis, and not far from the little village of
Zillis, the Via Mala opens into a plain bounded by high terraces. It
occurred to me the moment I saw it that the plain had been the bed of
an ancient lake; and a farmer, who was my temporary companion,
immediately informed me that such was the tradition of the
neighbourhood. This man conversed with intelligence, and as I drew
his attention to the rolled stones, which rest not only above the
river, but above the road, and inferred that the river must once have
been there to have rolled those stones, he saw the force of the
evidence perfectly. In fact, in former times, and subsequent to the
retreat of the great glaciers, a rocky barrier crossed the valley at
this place, damming the river which came from the mountains higher up.
A lake was thus formed which poured its waters over the barrier. Two
actions were here at work, both tending to obliterate the lake--the
raising of its bed by the deposition of detritus, and the cutting of
its dam by the river. In process of time the cut deepened into the
Via Mala; the lake was drained, and the river now flows in a definite
channel through the plain which its waters once totally covered.

From Tusis I crossed to Tiefenkasten by the Schien Pass, and thence
over the Julier Pass to Pontresina. There are three or four ancient
lake-beds between Tiefenkasten and the summit of the Julier. They are
all of the same type--a more or less broad and level valley-bottom,
with a barrier in front through which the river has cut a passage, the
drainage of the lake being the consequence. These lakes were
sometimes dammed by barriers of rock, sometimes by the moraines of
ancient glaciers.

An example of this latter kind occurs in the Rosegg valley, about
twenty minutes below the end of the Rosegg glacier, and about an hour
from Pontresina. The valley here is crossed by a pine-covered moraine
of the noblest dimensions; in the neighbourhood of London it might be
called a mountain. That it is a moraine, the inspection of it from a
point on the Surlei slopes above it will convince any person
possessing an educated eye. Where, moreover, the interior