Stronsy—Of the Kinetic Theory of Gas. 361 
of an outer concentric sphere (see Bryan, Joc. cit.). Such a complex 
molecule may represent a diatomic molecule with only three of its 
degrees of freedom operated upon during collisions. Here the 
energy of the molecule is 
T= 3 [MH (wv +0 + uw’) + 40? + Bu? + Cw;"], 
whereas the part concerned in the theorem is only 
T=$U (wiv + wv’), 
since the external surface being a smooth rigid sphere round the 
centre of inertia, the collisions cannot set up rotations. 
In this case u,v, and w are A events; and, on the average, 
divide equally among themselves the share of energy coming to 
this molecule under the theorem. At the same time the rotations 
1, W2, w; are Be events, and may be going forward, subject only 
to the equations of the rotation of a rigid body round its centre of 
inertia, viz. :— 
| T’ =4(Aw,? + Bu? + Cw"), 
G = A’) + Bw? + C’w,’. 
Their energy 7” may, accordingly, be of any amount in each 
molecule separately. 
We have hitherto had only A, Ba, and Bec motions in our 
illustrative models. Be events are of little practical interest ; 
whereas the study of Bd events is of much use, since they are 
probably present in large amount in actual gases. It is easy to 
modify our mechanical illustration so as to introduce events of 
this class. It may be done in either of the models we have 
employed by imagining the surface to be roughened (either by a 
small amount of friction or in the sense of being covered with 
slight frictionless elevations and depressions) and by supposing 
electrons (the charges of electricity which are associated with 
chemical bonds, and which, so long as they are undisguised, are 
acted on by the disturbance perpetually going on in the surround- 
ing ether) to be carried about by the internal or B events of the 
molecule. To complete the picture we may suppose most of these 
electrons to be so connected with the internal economy of the 
molecule that they can only perform evolutions that are resolvable 
into partials that have definite periods. 
SCIEN. PROC. R.D.S. VOL. VIII., PART IV. 9 10) 
