142 Proceedings of Boy al Society of Edinburgh. [mar. 21, 
sea-water and analogous saline solutions in a condition to enable the 
question, whether the salt does or does not form part of the solid 
matter of the crystals, to be solved directly by chemical analysis. 
So far as chemical analysis is applicable, it is in favour of the 
salt belonging exclusively to the adhering brine. When sea-water 
is carefully frozen artificially, the ratio between the chlorine and the 
sulphuric acid is the same for the solid contents of the original 
water, the crystals, and the mother-liquor. It is exceedingly un- 
likely, if part of the salt went into the crystals, leaving the re- 
mainder in the brine, that there would be no selective separation of 
its constituents. 
It has been shown that snow or pure lake ice, which, when 
melting by itself or immersed in pure water at atmospheric pressure, 
melts at the constant temperature called 0° C. or 32° Fahr., changes 
its melting temperature when immersed in a saline solution. The 
altered melting temperature, however, is the same for solutions of 
the same composition (no doubt with some allowance for pressure) 
and different for solutions of different composition. 
The temperature at which pure ice melts in a solution is identical 
with that at which ice separates from the same solution on being 
sufficiently cooled. 
"When sea-water is frozen to the extent of 15 per cent, of its 
mass, and the crystals so formed are allowed to melt in the liquid 
in which they have been produced, they melt exactly as they have 
been formed. If snow or pure ice be immersed in the brine formed 
by partially freezing sea-water, it melts at the same temperature as 
the ice which had been formed by freezing the sea-water, so long as 
the chemical composition remains the same in each case. 
The heat removed in freezing sea-water to the extent of 15 per 
cent, of its mass accounted for the production of the same amount 
of ice as was given by calculation on the basis of the chlorine found 
in the mother-liquor. 
When some saline solutions are cooled for a sufficient length of 
time at a sufficiently low temperature, there arrives a certain con- 
centration at a certain temperature, when further removal of heat 
causes solidification of the brine as a whole (cryohydrate). 
The concentration necessary for the solidification of even the 
cryohydrate of highest melting temperature is such that in the 
