J. P. Cooke, Jr.—Berthelot's Thermo-Chemistry. , 265 
As it seems to us the principle of molecular work should 
be supplemented by the principle of atomic work, and it is 
certain that neither clearness of conception nor definiteness of 
statement has been gained by the obvious attempt to avoid the 
recognition of the modern theory of chemistry. 
¢ readily accept Berthelot’s second fundamental principle 
of thermo-chemistry when enunciated as above, because it so 
eoeny falls under the general law of conservation of energ 
ange : é 
assu 
than Sal principle of the conservation of mass, prior to 
the experiments of Lavoisier, and as Lavoisier worked out this 
last great principle with the balance, so Berthelot and Thomsen 
ave demonstrated with the calorimeter the corresponding fun- 
a8 a generalization from the results of their work. oreover, 
although in cases of simple direct combination the principle 
under discussion is almost self-evident, and een lon 
remembered that very few processes of direct chemical combi- 
nation fulfill the conditions which an accurate measure of the 
