“ In a third, “On some important points in the theory of heat” (1819) , they stated that the specific heats of thirteen solid elements which they had investigated were nearly proportional to their atomic weights—a fact otherwise expressed in the “law of Dulong and Petit” that the atoms of simple substances have equal capacities for heat. ”

“ The original intention was to push the experiments to a pressure equivalent to thirty atmospheres, but owing to the signs of failure exhibited by the boiler the limit actually reached was twenty-four atmospheres, at which pressure the thermometers indicated a temperature of about 224°C. In his last paper, published posthumously in 1838, Dulong gave an account of experiments made to determine the heat disengaged in the combination of various simple and compound bodies, together with a description of the calorimeter he employed. ”