Letter from Earl of Berkeley, Berkeley Castle, to AW Porter Decribing Berkeley's work on osmotic pressures with reference to Porter's paper, 'On the Osmotic Pressure of Compressible Solutions of any Degree of Concentration. Part II. Cases in Which Both Solvent and Solute are Volatile', 'Proceedings of the Royal Society of London. Series A', Vol. 80, No. 541, Jun. 10, 1908. 20 July 1931