The Periodic Law of the Chemical Elements first foreshadowed by Newlands, and subsequently developed by Mendeleeff and Lothar Meyer, states:—(1) The Properties of the Elements are a Periodic Function of their Atomic Weights. (2) The Properties of the Compounds of the Elements are a Periodic Functiou of the Atomic Weights of their Constituent Elements. This law was explained and illustrated by several examples in the case of both chemical and physical properties, and attention specially directed to the division of the elements, as arranged in Mendeleeff's table (Ann. Chem. Pharm. ; Suppl. 1870-72, p. 151) into odd and even series, and to the somewhat peculiar character of the eighth group of that table. These points were further illustrated by a reference to Lothar Meyer's curve of the elements (Mod. Theor. der Chem.).