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in the water of the warm Atlantic stream. We can therefore
safely imagine the following cycle to take place.
Suppose a quantity of ice, say 1 kgr, to melt at 45° Lat.
N. and the issuing water to be transported with the Atlantic
current up to the western coast of Spitzbergen, where it at
last solidifies by the influence of the winter cold and is
afterwards brought back again with the arctic current to 45° Lat.,.
there to melt once more in the heated water of the Gulf-streain.
If the latent heat absorbed by the melting of 1 kgr. of
ice, at 45° Lat., was identically equal to the amount of heat
set free by the freezing of the seawater, at 75° or 80° Lat., the
whole result of the imaginary process, chosen as example,
would be a transport of about 79.2 Calories from the 45"’
to the 80th parallel. In this case the transport of the heat
must be performed by some external force, due either to the
trade winds or to the abundant supply of river water to the
Mexican Gulf, which causes the niveau of the water there to
stand higher than in the arctic sea. 1
We know from the foregoing, that the ice, which arrives
so far to the south as to 45° Lat., is relatively pure and only
contains a very little amount of salt, consisting principally of
chlorides and sulphates. The latent heat absorbed at its
melting (= Q) therefore must be a trifle less than 79.25 Calories.
If the water of the ocean did not contain any salt, we might
expect an identically great amount of heat to be developed
by the freezing of 1 kgr. of water at 80° Lat., provided that
it was not over-cooled before J’reezing.
By the saltness of the ocean the character of the process
is essentially changed. The latent heat (=R) developed at
the freezing of salt water is, as will be seen from the second
table of this chapter, very inferior to that of fresh water.
Even if we do not take into account the diminution of the
latent heat caused by the dissolved salt (which is however
very considerable), we must admit, that:
R < Q,
because the maximum temperature [T = — 2° C or — 1°.9 C]
of freezing ocean-water is considerably tower 2 than the melting
1 The difference of level at the equator and at the pole ought to be
about 2 metres, according to Colding [Skand. Nat. Forskare-Sallsk. Mote
1863. Bilaga D] and Guldberg [Polyt. Tidskrift, 3, 1872],
2 As a thermometer immersed in a mixture of snow and sea-water*
which is constantly stirred, indicates —1°.8 C, we may regard this as the
upper limit of the freezing- and the nether limit of the melting-temperatures
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