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The numbers found in the experiments V & VI of table 2 of
this chapter can not be substituted for R, because these
determinations were executed at temperatures 6 or 7 degrees lower
than T and the latent heat is calculated for 1 kgr. of the salt
water examined, without deduction for that part, which must be
enclosed as unfrozen brine, in case the temperature at the
freezing was so high as T. Besides we have hitherto supposed
the whole process to be a regular cycle, where every alteration
represented by the fractions ^ , ii... 5 , £_ ..., is reversible.
i 11 J I i
From this there will in reality be found to be several
exceptions, since many phenomena connected with the freezing of
sea-water, the overcooling etc... are not of reversible nature,
and the evaporation, which constantly takes place from the
water and the ice, gives rise to a series of thermodynamic
processes, which doubtlessly are of influence upon the
movement of the ocean, but fall entirely beyond the reach of the
present discussion.
Nevertheless it seems probable from the general outlines
of the phenomenon, which I have endeavoured to sketch in
the foregoing, that the transport of the warm water across
the ocean to high latitudes need not to be attributed solely
to external forces, since the melting and freezing of sea-ice is
found to involve the possibility of a transformation of thermic energy
into mechanic force.
If we admit the possibility that by the peculiar conditions,
under which the melting and freezing of sea-water takes place,
a certain quantity of solar heat is made useful for mechanic
purposes, it can not be difficult to understand lioiv the melting
of ice in sea water can give rise to an ocean current. Professor
Ekman in his paper upon the origin of currents 1 has proved
that this must be the effect of the melting, as follows:
Suppose a bit of pure ice, which swims freely in salt water,
to melt and the liquefied ice to retain its former place, then
the level of the fresh water will stand higher than the
surrounding sea, on account of the greater spec, volume of the
fresh water. This makes it expand above the surface of the
salt water. Pure ice, melting in pure water, occasions no
current, because its spec, volume is equal to that of the
surrounding fluid. — — — If we pursue the subject further, we
find, that the sea-water in the moment of freezing must perform
a certain amount of tvorh, by raising a part of the ice above the
1 Ofvers. K. V. A. Forb. 1875. N:o 7.
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