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point of the ice .sink 0°.io C below zero, while the presence of
a minimal quantity of impurity [the influence of which can
not be ignored in that part of the glacier, which is in contact
with the rocky ground and the debris separated from it by
erosion] is sufficient, to lower the melting point considerably
and make the ice soften and shrink in volume long before.
It must, in short, be taken into consideration, that every kind
of ice in nature becomes plastic and tough in the vicinity of its
melting point. 1
I next proceeded to the determination of the volumes of
the liquid .water [sample I]. These numbers [see table I, B] are
graphically represented by the red line in plate 23. The curve
is traced under the assumption of
q = 0.00017905
g = 0,00002754.
It will give the reader an opportunity of comparing the
performance of the new dilatometer with the results obtained
formerly by means of other methods.
CHAPTER 4.
On ice and water of little saltness.
From the reasons given in chapter 1, pages 250—253, I have
ventured to draw the conclusion, that the ice of the Siberian
sea is formed to a great part by the freezing of the brackish
1 With this restriction I think we may safely adopt the glacier theory
of Rendu or Forbes. Some important observations made on glaciers will
thereby be explained in the most natural manner, viz. the relatively rapid
progress of the ice masses in summertime and the birth of the glacier
remnants, which, according to eye-witnesses, takes place most frequently in hot
weather. Fetzholdt in the work already alluded to in this chapter cites
some observations concerning this subject by Hugi, Agassiz, Vogt a. O.
In every case the breaking up of a rift in the glacier was observed on some
very hot summer day. The rift was at first only a few inches deep, but
gradually increased, and the bursting of the ice was accompanied by a sharp
crack, like a peleton fire. From the behavior of the ice represented on plate
23 we might just expect such effects to take place. The upper layer of the ice
at first expands very regularly under the influence of the summer heat, but,
as its temperature approaches the melting point, suddenly begins to contract
its volume enormously. This causes a hard strain upon its surface, which
ends with the breaking up of fissures and remnants.
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