Synthesis") 1860; and "Leçons sur les méthodes générales de synthèse en chimie organique" ("Lessons on the General Methods of Synthesis in Organic Chemistry"), a course of lectures in the Collége de France, 1864.
M. Berthelot has also pursued elaborate researches in specific heat, and in the relations between the heat developed in composition and decomposition, and the force of affinity. On the subject of the relations of specific heat with the composition of bodies he said, in 1873, in a discussion in the French Academy with M. Dumas: "The study of the specific heats established by the most recent researches tends to prove that there is a positive characteristic which, it seems to me, distinguishes the elements of modern chemistry from its compounds, and shows that no known compound body ought to be considered as of the same order as an actually simple one. The importance of such a characteristic can not be doubted, and it becomes greater on account of the mechanical meaning which modern theories attach to specific heat. . . . Nevertheless, exaggerated conclusions must not be drawn from such an opposition between the mechanical and physical characteristics of our simple and compound bodies. If our elements have not as yet been decomposed, and appear not to be decomposable by the forces which are at present at the command of the chemist, nothing compels us to assert that they are not decomposable in another way than our compounds are; as, for instance, as Mr. Lockyer asserts, by means of the forces acting in cosmical space. Nor does anything prevent that such a discovery as that of voltaic electricity would enable the chemists of the future to overpass the limits which are imposed upon us. The possible fundamental identity of the matter constituting our elements, and the possibility of transmuting into one another the so-called elements, can, moreover, be admitted into the category of more or less plausible hypotheses without it necessarily resulting that there is a single really existing matter of which our actual elements represent unequal states of condensation. In fact, nothing compels us to conceive the existence of a final decomposition which shall tend necessarily to reduce our elements either to more simple bodies, from the addition of which they arise, or to multiples of a single elementary ponderable unit."
M. Berthelot's views of the relations between chemical affinity and the intensity of chemical action were presented in his "Essai de mécanique chimique fondée sur la thermo-chimie" ("Essay on Chemical Dynamics based on Thermo-Chemistry"), 1880, of which Mr. M. M. Pattison Muir said, in "Nature," that its publication "marks an important point in the advance of modern chemistry." Among the more recent investigations which M. Berthelot has pursued in the light of his thermo-cbemical theories are those into the properties of explosives and the laws of the propagation of explosions.
