The investigation of the volume retained by different elementary substances, when combined in the solid condition, has attracted the attention of many chemists. We have only to look at the laborious memoirs of Schröter, Kopp, Playfair and Joule, Boullay, Filhol, and others, to be convinced of the great amount of labour expended on the subject. Nor is it at all remarkable that so many workers should take to this field of research, when we remember the simplicity of the laws regulating the combining volumes of gaseous substances, and the probable extension of some such similar law to the solid condition of matter. Emboldened by analogy, the forementioned workers endeavoured to find some constant to which volumes of elements and compounds held the relation of some simple multiple, and thus extend the apparent simplicity of Prout's law of combining weights to combining volumes.