The author refers to the customary view that black phosphorus is merely a mixture of the ordinary phosphorus with traces of a metallic phosphide, and contends that this explanation is not in all cases admissible. A specimen of black or rather dark gray phosphorus, which the author submitted to the Academy, became white if melted and remained white if suddenly cooled, but if allowed to enter into a state of superfusion it became again black on contact with either white or black phosphorus. A portion of the black specimen being dissolved in carbon disulphide there remained undissolved merely a trace of a very pale yellow matter which seemed to be amorphous phosphorus.--Comptes Rendus.