Sir Charles Blagden concludes a memoir in the Philosophical Transactions of London, vol. lxxviii., for the year 1788, “On the Effect of various substances in lowering the Point of Congelation in Water,” with the account of an experiment to determine the effect of salt upon the expansion of water by cold.

From that experiment, he imagined that he had reason to conclude, as far as one experiment goes, that the combination of a salt with water has no other effect upon its quality of expanding by cold, than to depress the point at which that quality begins to be sensible, just as much as it depresses the point of congelation.

The scientific world appear to have admitted this general deduction of Blagden, and, trusting to the result of a single experiment, extended it so far as to lay it down as a general law, that, as pure water has its maximum of density at 7½° above its freezing point, so every saline solution has a maximum of density at a temperature above its point of congelation, and that this temperature will be exactly 7½° distant from the freezing point of the solution.