, it follows
that these vacuous spaces could not exist in such large continuous
fragments, presenting throughout the fragments the same trend, if there
had been no frost within the mass, affecting the whole of such a
fragment while it remained in the same position.
The most striking evidence, in my opinion, that at times the whole mass
of the glacier actually freezes, is drawn from the fact, already alluded
to, that, while the surface of the glacier loses annually from nine to
ten feet of its thickness by evaporation and melting, it swells, on the
other hand, in the spring, to the amount of about five feet. Such a
dilatation can hardly be the result of pressure and the packing of the
snow and ice, since the difference in the bulk of the ice brought down,
during one year, from a point above to that under observation, would not
account for the swelling. It is more readily explained by the freezing
of the water of infiltration during spring and early summer, when the
infiltration is most copious and the winter cold has been accumulating
for the longest time. This view of the case is sustained by Elie de
Beaumont, who states his opinion upon this point as follows:--
"Pendant l'hiver, la temperature de la surface du glacier s'abaisse a un
grand nombre de degres au-dessous de zero, et cette basse temperature
penetre, quoique avec un affaiblissement graduel, dans l'interieur de la
masse.
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