or Centrifugal Theory of Elasticity. 363 



Now h is the specific elasticity of the atomic atmosphere of the 



substance, , ^ is the mean specific gravity of that atmosphere 



when the body is in the theoretical state of perfect gas, and k 

 and T(j are the same for all substances in nature. Therefore, for 

 every substance in nature, the mean specific gravity of the atomic 

 atmosphere in the theoretical state of perfect gas is inversely pro- 

 portional to the specific elasticity of that atmosphere. 

 Real specific heat may also be thus expressed : — 



in which — corresponds to tttiT in my former papers, and -^ 



, 3HI "^"l , '^ ^ 



to -^ — or -^77 : so that 

 Ji/u. JN 



^i=^°=N«' P«A) 



The factor N appears to depend on the chemical constitution 

 of the substance*. 



(8.) Total Pressure of Substances in general, expressed in terms 

 of temperature. 



In equation (9) let — be put for 6 ; then 

 P=/>+/(V)=/(V)+-^G,^{g,-^ + ^-&c.} 



=yiv)+'^^{i-^>--^^-^-&c.}, . . (21) 



where 



— /cG' K^ 



A, = — q; ') •A-2=~ Q-2(^l^~^l )> 



A3=-^3(Gi''-3G/G/' + G/"); &c. 



This formula is identical with that which I employed in my 

 former paper, to represent the pressure of an imperfect gas, and 

 which 1 found to agree with ]\I. Regnault's experiments, when 

 the coefficients A and the function /(V) had been calculated em- 

 pirically f. 



[To be continued.] 



* The values of N for atmospheric air, oxygen, hydi-ogen, and carbonic 

 oxide, differ from 04 1 by quantities which are within the Umits of errors 

 of observation. (1853.) "See also Phil. Mag. June 1853, and Trans. Roy. 

 Soc. Edinb. vol. xx. p. 581). 



t l*or further applications of equation (21), see the paper of Messrs. 

 Joule and Thomson in the Phil. Trans, for 1864. (Sept. 1865.) 



2B2 



