1887.] Mr J. Y. Buchanan on Ice and Brines. 143 
primary freezing of the water of the sea no such body can he 
formed. It would follow from this consideration alone that the 
first ice formed on the sea in Arctic regions consists of pure ice, 
and it is also certain that it would retain a large quantity of the 
residual sea-water in its interstices. During the winter this in- 
closed liquor would solidify in the interstices of the crystals to ice 
and cryohydrates, in so far as the temperature and the nature of 
the salts in solution would permit. From my experiments with 
chloride of calcium, and the existence of hrines observed to remain 
liquid at - 30° C. at the winter quarters of the “ Vega,” it is unlikely 
that sea-water, as a whole, can ever he completely solidified in 
nature. The presence of unfreezable or difficultly freezable brine 
in freshly-formed sea-water ice, explains its eminently plastic char- 
acter even at very low temperatures. 
The fact that cryohydrates of different salts solidify and melt at 
different temperatures, sufficiently explains the various composition 
of different specimens of old sea ice. 
The apparent expansion, near the melting-point, of ice formed by 
freezing water which contains any salt at all is perfectly explained 
on the hypothesis that in the act of freezing the water rigidly 
excludes all saline matter from participation in its solidification. 
The residual and unfreezable brine which remains in consider- 
able quantity liquid when sea-water is frozen, must also remain in 
greater or less quantity when fresh water is frozen. All natural 
waters, including rain-water, contain some foreign and usually saline 
ingredients. If we take chloride of sodium as the type of such 
ingredients, and suppose a water to contain a quantity of this salt 
equivalent to one part by weight of chlorine in a million parts of 
water, then we should have a solution containing O'OOOl per cent, 
of chlorine, and it would begin to freeze and to deposit pure ice at 
a temperature of - 0 o, 0001 C.; and it would continue to do so 
until, say, 999,000 parts of water had been deposited as ice. There 
would then remain 1000 parts of residual water, which would 
retain the salt, and would contain, therefore, 0T per cent, of 
chlorine, and would not freeze until the temperature had fallen to 
- 0°T C. This water would then deposit ice at temperatures 
becoming progressively lower, until, when 900 more parts of ice 
had been deposited, we should have 100 parts residual water, or 
