For the purpose of determining these constants, hydrometric observations were made on solutions of the three salts the concentrations of which ranged from 1/2 to 1/1024 gram-molecule per thousand grams of water, the experiments being made with the closed hydrometers Nos. 3 and 17. Experiments were also made on strong solutions of calcium chloride and magnesium chloride, using the open hydrometers A and B ; the concentrations of these solutions varied from 1 gram-molecule per thousand grams of water to the highest attainable degree of supersaturation. It was when the experiments on a supersaturated solution of calcium chloride were in progress that the observations were made which revealed the remarkable state of unrest in that solution which preceded its partition into crystals and mother-liquor with liberation of heat.