M. Regnault's Researches upon the 



with a prize by the Academy in 1813, is at the present time the 

 most complete one upon this subject, and that in which the 

 results differ least from the truth. This superiority is owing not 

 only to the extreme care with which these skilful experimenters 

 carried out their investigation, but likewise to the direct method 

 which they adopted ; while the greater number of other physi- 

 cists have had recourse to indirect methods, in which the ele- 

 ment sought frequently exercised but a very slight influence. 



The general results at which Delaroche and Berard arrived 

 are the following : — 



1. All gases do not possess the same specific heat in regard 

 either to volume or weight. The specific heat of equal weights 

 or equal volumes of the several gases has the following values for 

 these two modes of comparison : — 



Specific heat of Eaual volumes. Equal weights. Spec. grav. 



Air ....... ' 1-0000 10000 1-0000 



Hydrogen 0-9033 123401 00732 



Carbonic acid .... 1-2583 08280 1-5196 



Oxygen 0-9765 08848 1-1036 



Nitrogen 1-0000 10318 09691 



Protoxide of nitrogen . 1-3503 0-8878 1-5209 



Olefiantgas .... 1-5530 1-5763 09885 



Carbonic oxide . . . 1-0340 1-0805 09569 



2. The capacity for heat of the same gases in relation to water 

 is expressed by the following numbers : — 



Specific heat of water 1-0000 



atmospheric air . . . 0-2669 



hydrogen 3-2936 



carbonic acid . . . 0-2210 



oxygen 0-2361 



nitrogen 0-2754 



protoxide of nitrogen . 0-2369 



olefiant gas ... . 0-4207 



carbonic oxide . . . 0*2884 



• aqueous vapour . . . 0*8470 



3. The specific heat of atmospheric air with constant volume 

 increases with its density, but in less rapid progression. The 



relation of the pressures being ^ qkqq j that of the specific heats 



1 l-oOoo 



^ 1*2396' 



4. Delaroche and Berard assumed, for theoretical reasons 

 founded upon the direct experiments of Gay-Lussac, that the 

 specific heat of a gas increased rapidly with the temperature. 



Such are the most accurate views which we possess at the 



••• 



... 

 ••• 



