338 Literary and Philosophical Society. 



'The experimental results of Delaroche and Berard 

 are invariably higher than those demanded by the hypo- 

 thesis. But it must be observed that the experiments of 

 Delaroche and Berard, though considered the best that 

 have hitherto been made, differ considerably from those 

 of other philosophers. I believe, however, that the in- 

 vestigation undertaken by M. V. Regnault, for the French 

 Government, 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, 

 characterised by all the accuracy for which that distin- 

 guished philosopher is so justly famous. Till then, perhaps, 

 it will be better to delay any further modifications of the 

 dynamical theory, by which its deductions may be made 

 to correspond more closely with the results of experiment.' L 



We have thus got to the motion of atoms, but the 

 result of this motion was also taken up by Joule, and we 

 give him without difficulty the honour of showing its 

 relations first in one very important direction, namely 



1 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 2 is to I, and the comparison of the theoretical 

 with the experimental specific heat will be as follows : 



Experimental Theoretical 



specific heat. specific heat. 

 Hydrogen ...... 2-352 3-012 



Oxygen 0-168 0-188 



Nitrogen ..... 0-195 0-214 



Carbonic oxide . . . .0-158 0-136 



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

 above hypothesis. June 1851, J. P. J. 



