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MR. J. H. JEANS ON THE DISTRIBUTION OF MOLECULAR ENERGY. 
account of density will be unnoticeable in comparison with variations on account of 
temperature. 
It is, however, clear that in considering radiations from gases of great density, such 
as for example occur in tlie sun, the factor p would be of considerable importance. 
Generalised Theory of Temperature. 
§ 30. The state of a gas may be regarded as depending upon a principal 
temperature T, and also on a number of subsidiary temperatures r^, To, . . . , each 
of these temperatures corresponding to one (or possibly more) of the degrees of 
freedom of tlie molecule. The principal temperature is to correspond to the three 
degrees of freedom implied by the possibility of translation through the ether, 
and to any other degrees of freedom which are such that their mean energy is at all 
temperatures equal to a third of the mean energy of translation. 
The principal temperature is to be proportional to the mean energy of translation 
of a molecule and each subsidiary temperature proportional to the mean energy of 
each of the modes to which it corresponds. Thus two modes can only have the same 
subsidiary temperature when their mean energies are, under all circumstances, 
equal, as, for example, when they are tlie kinetic and potential energies of the same 
vibration. When the energy is equally distributed between all the degrees of freedom 
all these temperatures are to become equal. 
We have found that at temperatures below the temperature of incandescence there 
is an approximately steady state in which 
^i = d/i(T), To = p/;(T), &c., 
where /((T), fif), &c., are functions of T, which at these temperatures are very 
small in comparison with T. 
At higher temperatures we have not investigated the forms of t^, To, . . . , but at 
infinite temperatures, 
Ti =: To = . . . . = T. 
§ 31. The steady state sjiecified above was arrived at on the assumption that 
external agencies could only influence the energy of translation, and that the other 
energies were only influenced indirectly through changes in the energy of translation. 
Thus the above equations will not hold in the presence of agencies which exert a 
direct influence on the subsidiary temperatures. Such influences may be looked for 
in the forces of chemical action, disturbances in the ether, and possibly in the cathode 
rays, if we supjoose these rays to be streams of charged ions which are so small as to 
penetrate inside a molecule rather than act on the molecule as a whole. 
When such agencies are present, the above equations must give place to others. 
The subsidiary temperatures which are most directly concerned may attain to 
