A laboratory is an inhabited room, and in Northern Europe the temperature of such apartments lies generally between 12° and 20°C. Consequently we find that a large amount of specific gravity work has been done at 15°C. by Gerlach, at 19·5° C. by Kremers, and at 17·5° C. by others ; while the calorimetric work by Julius Thomsen, extending over the last half-century, was all done at the temperature 18° C.