Historical introductions -- On the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms, by W. Prout. (From Annals of philosophy, v. 6, 1815, p. 321-330) -- Correction of a mistake in the essay on the relation between the specific gravities of bodies in their gaseous state and the weights of their atoms, by W. Prout. (From the Annals of philosophy, v. 7, 1816, p. 111-113) -- Extracts from Researches on the mutal relations of atomic weights, by J.S. Stas. (Translated from Bulletin de l'Académie royale de Belgique, ser. 2, v. 10, 1860, p. 208-213, 336) -- Commentary on the foregoing paper, by C. Marignae. (Translated from Bibliothèque universelle (Archives) v. 9, 1860, p. 97-107)