The compressibility of sea-water is not yet fully investigated.
This determination involves a knowledge of the density and of the compressibility of the solution; the latter property is difficult to measure accurately.
It is often impossible to observe the pressure-coefficient dp/de directly, but it may be deduced from the isothermal compressibility by means of the geometrically obvious relation, BE = (BEÃ†C) XEC. The ratio BEÃ†C of the diminution of pressure to the increase of volume at constant temperature, or - dp/dv, is readily observed.
From the known coefficients of compressibility and thermal expansion we find that V may be represented by the linear equation V=1.000+0.0008 A, where A is the lowering of the freezing point below o°.
From 1879 to 1888 he was engaged on difficult experimental investigations, which began with an inquiry into the corrections required, owing to the great pressures to which the instruments had been subjected, in the readings of the thermometers employed by the "Challenger" expedition for observing deep-sea temperatures, and which were extended to include the compressibility of water, glass and mercury.