29, Frontispiece). In
Greenland and in Norway there are enormous ice-rivers or glaciers,
and even in Switzerland some of them are very large. The Aletsch
glacier, in the Alps, is fifteen miles long, and some are even
longer than this. They move very slowly - on an average about 20
to 27 inches in the centre, and 13 to 19 inches at the sides every
twenty-four hours, in the summer and autumn. How they move, we
cannot stop to discuss now; but if you will take a slab of thin
ice and rest it upon its two ends only, you can prove to yourself
that ice does bend, for in a few hours you will find that its own
weight has drawn it down in the centre, so as to form a curve.
This will help you to picture to yourselves how glaciers can adapt
themselves to the windings of the valley, creeping slowly onwards
until they come down to a point where the air is warm enough to
melt them, and then the ice flows away in a stream of water. It is
very curious to see the number of little rills running down the
great masses of ice at the glacier's mouth, bringing down with
them gravel, and every now and then a large stone, which falls
splashing into the stream below.
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