34 



REPORT — 1844. 



and furnished with glass sight-holes (or composed of glass). Into this vessel the gases 

 are to be forced under a somewhat greater pressure than that sustained by the vessel 

 (ignited previously, or by an electric spark). 



On. Specific Heat. By J. P. Joule. 



After examining the law of Dulong and Petit, that the specific heat of simple bodies 

 is inversely proportional to their atomic weights, the author proceeded to detail the 

 attempts made by Haycraft, Ue la Rive, and Marcet, to discover the specific lieats of 

 gases and liquids. The observations of Neumann and Regnault on the specific heats 

 of simple and compound bodies were next examined. Mr. Joule then exhibited to the 

 Section a table, in wliich the theoretical specific heats of a variety of bodies impartially 

 selected were calculated on the hypothesis that the capacity for heat of a simple 

 atom remains the same into whatever chemical combination it enters. On the whole, 

 the coincidence between the theoretical and experimental results was such as would 

 induce a belief that the law of Dulong and Petit, with regard to simple atoms, is ca- 

 pable of a greater degree of generalization than chemists have hitherto been inclined 

 to admit. 



TABLE. 



