The first three pressure-columns of the following little table were constructed from the elaborate data given by Drs Ramsay and Young in their important paper “On Evaporation and Dissociation,” Part IV. (Phil. Mag., May 1887). They give, in metres of mercury, the pressures required to confine one gramme of oxide of ethyl to various specified numbers of cubic centimetres, at temperatures near to that of the critical point.