Stronry—Of the Kinetic Theory of Gas. 365 
In this Table, y is the ratio of the two Specific Heats, as 
given by observation; m is the number of degrees of freedom 
of each molecule; and m-—3 isthe number of degrees of freedom 
of its B, or internal, motions: according to the Boltzmann- 
Maxwell Theorem. : 
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, page 312) that the ether, 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 
determine 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 ether, and are therefore inalienably associated with that 
molecule; but as regards the 97 others, the linkage through the 
zether may be such that millions of molecules are, as it were, held 
in one grasp, either firmly or more or less loosely. Accordingly, 
as regards any one molecule, 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 ether 
were a mere linkage, and not at the same time an agency which 
‘excites simultaneous motions within swarms of molecules, it would 
