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water beneath the ice was for the most part cooled below its
normal freezing point [— l°.s to — Io.7 C]. From the increasing
thickness of the ice-floes we must infer, that the sea-wrater
below was constantly giving up ice. Consequently we ought
to expect, that its temperature would remain precisely at the
normal freezing-point during the whole time. Although I am
acquainted with many similar observations fróm previous
deep-soundings in arctic seas, I can find no plausible
explanation for the strange fact, that water, which is in contact with
ice, can be over-cooled at the same time. From a physical
point of view such temperatures as f. ex. —2°.s C or —3°.o C
in water, which does not contain more than 2.72 p. c. of salt
and has a spec, weight of not more than I.0217 —1.0227 or
thereabouts must be considered as abnormal.
The lowest temperatures hitherto observed in the ocean
are those found in Baffin Bay [t =— 2°.s C; depth = 1478
metres (Parry), and t = — 3°.7 C; depth = 1243 metres (Ross
& Sabine) and west of Spitzbergen, 1873, by the Swedish
expedition [t = — 3°.2 C; depth = 142 metres] and (in the same
year) by Mr. Leigh Smith [t = — 5°.i C; depth = 1005 metres].
The numbers in the above tables, taken from the observations*
in the winter 1878—79 at Pitlekaj, do not range among the
lowest submarine temperatures ever observed, but are, however,
still more remarkable by the circumstance, that the cold layer
was found only a few metres below the surface. The low
temperatures observed in the sea east and west of Greenland
belonged to a stratum of water 140 to 1000 metres beneath
the surface, which was exposed to an enormous pressure.
The rate, at which the freezing point of salt water decreases
under the influence of pressure, is at present totally unknown
to us. It might therefore be possible that the water of —5° C
1 We ought by no means a priori to apply the formula found by J.
Thomson (Transact. R. S. E. T. XVI) for the depression of the
freezing-point of pure water also to sea-water. The mistakes, which have arisen
from confounding the properties of sea-water and fresh water, or sea-ice with
fresh-water-ice, are too numerous and flagrant not to impress the necessity
of experimental investigation. In the same way, as the majority of
hydro-grapliers 30 or 40 years ago took for granted, that the maximum density of
sea-water was at -f- 4° C, like that of fresh water, and that the sea from a
thousand metres from the surface to the bottom had a constant
temperature etc., science has hitherto tacitly supposed, that the dilatation, the
chemical composition and the latent heat of sea-ice was equal or almost equal
to that of fresh-water-ice. In the preceding paper I have tried to show up
the fallacy of these assumptions.
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