430 
ME. J. H. JEANS ON THE DISTRIBUTION OF MOLECULAR ENERGY. 
If a quantity (7Q of work be absorbed by a gas, 
dQ = NrfW — pdv 
= CNjnJT + (fi/; (T))} - . 
If the gas be made to pass through any succession of states so as to return to the 
same temperature and density, 
= CNS^, rfX. 
Thus the second law of thermodynamics will only hold in special cases for a gas which is 
emitting radiation of any kind. This part of the subject of luminosity has, however, 
been developed by Wiedemann,"^ so that it seems unnecessary to pursue it any 
further here. 
E. WiEDEMjiNN, “Mechanics of Luminosity,” ‘Phil. Mag.,’vol. 28, 1889, p. 152, or ‘ Wied. Annalen 
Tol. 37, p. 181. 
