Indeed, if all the spaces in the mass of the glacier, not occupied
by continuous ice, could be graphically represented, I believe it would
be seen that cold air surrounds the glacier-ice itself in every
direction, so that probably no masses of a greater thickness than that
already known to be permeable to cold at the surface would escape this
contact with the external temperature. If this be the case, it is
evident that water may freeze in any part of the glacier.
To substantiate this position, which, if sustained, would prove that the
dilatation of the mass of the glacier is an essential element of its
motion, I may allude to several other well-known facts. The loose snow
of the upper regions is gradually transformed into compact ice. The
experiments of Dr. Tyndall prove that this may be the result of
pressure; but in the region of the _neve_ it is evidently owing to the
transformation of the snow-flakes into ice by repeated melting and
freezing, for it takes place in the uppermost layers of the snow, where
pressure can have no such effect, as well as in its deeper beds. I take
it for granted, also, that no one, familiar with the presence of the
numerous ice-seams parallel to the layers of snow in these upper regions
of the glacier, can doubt that they, as well as the _neve_, are the
result of frost.
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