our heads, wherever we are,
there reigns, at a distance of two or three miles above us, an intense
and perpetual cold. This is true not only in cool and temperate
latitudes, but also in the most torrid regions of the globe. If we
were to ascend in a balloon at Borneo at midday, when the burning sun
of the tropics was directly over our heads, to an elevation of five
or six miles, we should find that although we had been moving nearer
to the sun all the time, its rays would have lost, gradually, all
their power. They would fall upon us as brightly as ever, but their
heat would be gone. They would feel like moonbeams, and we should be
surrounded with an atmosphere as frosty as that of the icebergs of the
frigid zone.

It is from this region of perpetual cold that hail-stones descend upon
us in the midst of summer, and snow is continually forming and falling
there; but the light and fleecy flakes melt before they reach the
earth, so that, while the hail has such solidity and momentum that it
forces its way through, the snow dissolves, and falls upon us as a
cool and refreshing rain. Rain cools the air around us and the ground,
because it comes from cooler regions of the air above.

Now it happens that not only the summits, but extensive portions of
the upper declivities of the Alps, rise into the region of perpetual
winter. Of course, ice congeals continually there, and the snow which
forms falls to the ground as snow, and accumulates in vast and
permanent stores. The summit of Mount Blanc is covered with a bed of
snow of enormous thickness, which is almost as much a permanent
geological stratum of the mountain as the granite which lies beneath
it.

Of course, during the winter months, the whole country of the Alps,
valley as well as hill, is covered with snow. In the spring the snow
melts in the valleys and plains, and higher up it becomes damp and
heavy with partial melting, and slides down the declivities in vast
avalanches, which sometimes are of such enormous magnitude, and
descend with such resistless force, as to bring down earth, rocks, and
even the trees of the forest in their train. On the higher
declivities, however, and over all the rounded summits, the snow still
clings to its place, yielding but very little to the feeble beams of
the sun, even in July.

There are vast ravines and valleys among the higher Alps where the
snow accumulates, being driven into them by winds and storms in the
winter, and slidin