Kinetic Theory of Gas. 375 



Postponing for the present the observations which the 

 details of this table suggest, and taking a general survey of 

 it, it was difficult to see how the small number of degrees of 

 freedom suggested by the Boltzmann-Maxwell Theorem, as 

 shown in the last column of this table, could be reconciled 

 with the known great complexity of the molecules of which 

 real gases consist, until Professor FitzGerald pointed out 

 (Proceedings of the Royal Society for February 14, 1895, 

 p. 312) that the aether, acting on the electrons, which in turn 

 are intimately connected with the ponderable matter of the 

 molecule, must perform the function of a more or less perfect 

 linkage between molecules, compelling them, so far as some 

 of their motions are concerned, to move together in swarms. 

 This follows at once from the circumstance that the electro- 

 magnetic waves, in which radiant heat and light consist, are 

 hundreds of times longer than the average intervals between 

 molecules in gases at the pressures and temperatures at which 

 the gases in the table were when experimented on to deter- 

 mine the value of y. 



There may be a hundred degrees of freedom in a molecule. 

 Of these the three which are concerned in its power of 

 travelling about between its encounters are not affected by 

 what goes on in the aether, and are therefore inalienably 

 associated with that molecule ; but as regards the 97 others, 

 the linkage through the aether may be such that millions of 

 molecules are, as it w r ere, held in one grasp, either firmly or 

 more or less loosely. Accordingly, as regards any one mole- 

 cule, these 97 may make no appreciable increase, or may 

 make but a moderate increase to the three which in all cases 

 must attach to the molecule. These three are A events, and 

 along with them we should class the few Ba events which 

 have no electrons associated with them, of which there seem 

 to be two in several of the transparent diatomic gases. 



We here seem to be led to another conclusion. If the 

 aether were a mere linkage, and not at the same time an 

 agency which excites simultaneous motions within swarms of 

 molecules, it would appear from the Boltzmann-Maxwell 

 theorem that none such would in any appreciable degree be 

 brought into existence by the encounters between molecules. 

 If, for example, the expression for T contains two B terms in- 

 stead of 97, then only § of the energy which is taken account 

 of in the theorem would be available for distribution among 

 97 distinct kinds of motion, and therefore too little for any 

 but a very few of them to be able to exhibit an observable 

 effect. The rest, the B6 events, would all depend for their 

 activity upon energy reaching the molecules as radiant heat 



