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214 CANTON OF VALLAIS.
The mountains on each side of this
valley are the highest of any on the Old
Continent, except the Hemmeleh in Asia,
for on one side are the loftiest summits in
the southern range of the Alps, and on the
other, the loftiest summits of the northern
range. They form two walls of rock, much
shattered and intersected, and varying in
height, from nine to twelve thousand feet
above the valley. The central mass on
each side is granitic, divided into beds
which are nearly vertical, and their general
range is N. E. and S. W. or nearly in the
direction of the valley. The bottom of
these mountains in the valley are generally
covered with secondary strata, except near
its upper part, and also for a short space
in its lower part near Martigny, where a
deep section is made through the secondary
strata, and has laid bare tlie granitic rocks.
From each of the ranges on tiie right and
left, numerous deep ravines, besides the
lateral valleys, open into the great valley,
and bring their tributary streams to the
Rhone. The valley of the Upper Rhone
may be regarded as a trough, one hundred
miles in length, a mile and a half in depth,
and two miles wide at the bottom. The
sides of this trough are deeply furrowed,
and split into irregular forms, rising higher
and higher behind each other, from the
Rhone to the summit of the range on each
side. This trough forms the whole canton
of the Valíais : its upper p a rtis nearly surrounded
by snow and glaciers, and a considerable
portion of the intermediate space
is covered by barren rocks, forests, and
eboulements ; added to this, the broader
part of the bottom of the valley is, in
many places, a marsh. Vast eboulements
are every year falling from the enormous
precipices that overhang the lower ground ;
many of these are recorded which have
destroyed entire villages. Avalanches have
also sometimes fallen of such vast size as
to occasion dreadful inundations of the
R h ô n e; and on the 18th of February,
1720, the village of Obergestelen, with
eighty-eight of its inhabitants, were overwhelmed
by an avalanche. Accidents of
a similar kind, but less extensive, are of
common occurrence. Lakes of water which
have been dammed in by the extension of
the glaciers across the mountain-valleys, are
sometimes suddenly poured into the lower
valleys, by the breaking up of the ice. The
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