114 MR. J. r. JOULE ON HEAT, ETC. 



position with the experimental results of Delaroche and 

 Berard reduced to constant volume. 



Hydrogen, ... 



Oxygen, 



Nitrogen - _ . 



Carbonic oxide 



The experimental results of Delaroche and Berard are 

 invariably higher than those demanded by the hypothesis. 

 But it must be observed, that the experiments of Dela- 

 roche and Berard, though considered the best that have 

 hitherto been made, differ considerably from those of other 

 philosophers. I believe, however, that the investigation 

 undertaken by M. V. Regnault, for the French Govern- 

 ment, will embrace the important subject of the capacity 

 of bodies for heat, and that we may shortly expect a new 

 series of determinations of the specific heat of gases, cha- 

 racterized by all the accuracy for which that distinguished 

 philosopher is so justly famous. Till then, perhaps, it will 

 be better to delay any further modifications of the dynami- 

 cal theory, by which its deductions may be made to cor- 

 respond more closely with the results of experiment.* 



* If we assume that the particles of a gas are resisted uniformly until 

 their motion is stopped, and that then their motion is renewed in the 

 opposite direction, by the continued operation of the same cause, as in the 

 projection upwards and subsequent fall of a heavy body ; the maximum 

 velocity of the particles will be to the uniform velocity required by the 

 theory assumed in the text, as the square root of two is to one, and the 

 comparison of the theoretical with the experimental specific heat will be 

 as follows : — 



I have just learned that the experiments of Regnault on the specific 

 beat of elastic fluids are on the eve of publication, and doubt not that their 

 accuracy will enable us to arrive at a decisive conclusion as to the cor- 

 rectness of the above hypothesis. — June, 1851. J. P. J. 



