hade, the summit of Mont Blanc for instance is transfigured by the
light of the setting sun glowing on the snow. It seems almost like a
light from another world, and vanishes as suddenly and mysteriously as
it came.

As we look up from the valleys the mountain peaks seem like separate
pinnacles projecting far above the general level. This, however, is a
very erroneous impression, and when we examine the view from the top of
any of the higher mountains, or even from one of very moderate
elevation, if well placed, such say as the well-known Piz Languard, we
see that in many cases they must have once formed a dome, or even a
table land, out of which the valleys have been carved. Many mountain
chains were originally at least twice as high as they are now, and the
highest peaks are those which have suffered least from the wear and tear
of time.

We used to speak of the everlasting hills, and are only beginning to
realise the vast and many changes which our earth has undergone.

There rolls the deep where grew the tree.
O earth, what changes hast thou seen!
There where the long street roars, hath been
The stillness of the central sea.

The hills are shadows, and they flow
From form to form, and nothing stands;
They melt like mist, the solid lands,
Like clouds they shape themselves and go.[42]

THE ORIGIN OF MOUNTAINS

Geography moreover acquires a new interest when we once realise that
mountains are no mere accidents, but that for every mountain chain, for
every peak and valley, there is a cause and an explanation.

The origin of Mountains is a question of much interest. The building up
of Volcanoes is even now going on before our eyes. Some others, the
Dolomites for instance, have been regarded by Richthofen and other
geologists as ancient coral islands. The long lines of escarpment which
often stretch for miles across country, are now ascertained, mainly
through the researches of Whitaker, to be due to the differential action
of aerial causes. The general origin of mountain chains, however, was at
first naturally enough attributed to direct upward pressure from below.
To attribute them in any way to subsidence seems almost a paradox, and
yet it appears to be now well established that the general cause is
lateral compression, due to contraction of the underlying mass. The
earth, we know, has been gradually cooling, and as it contracted in
doing so, the strata of the