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and the value of this is 4m as soon as n>2. Indeed, the points on 
the circle, determined by the angles 2y, 2 (» 4 =) ‚2 (« + =), 
U U 
and so on, are the vertices of a regular polygon and therefore the 
resultant of the vectors drawn from the center towards these points 
is zero. Thus the moments of inertia A, B, C will not depend on 
w. Though they will be increased to a certain extent by the presence 
of circulating electrons, we may continue to represent them by A, By Us 
No ambiguity will arise from this. 
The second part 7, of the kinetic energy depends on yw. It is 
evident, that one electron gives 
| Fm rt? yw’, 
if m is its mass and + the radius of its path. As we suppose w, 
m and r to be the same for all the electrons, we may write 
27, = Dw’, 
where 
EM, 
the summation being extended to all the circulating electrons. 
The third part 7’, will depend on the products gw. It is the 
existence of this part, that Maxwerr. wanted to test experimentally. 
The calculation of 7, requires somewhat more consideration. A 
material point with mass m and two velocities 7, and v, (vectors) 
has the kinetic energy. 
kmo? + ¥ mv? + m(v,-v,) do 2. ee (4) 
We shall apply this to each circulating electron. It will possess 
firstly the velocity v, due to its motion in the circle and secondly 
the velocity v, due to the motion of the whole body. Now the first 
two parts of (4) are contained in 7, and 7. The velocity v, may 
be resolved into the velocities due to the rotations of the body about 
OX, OY, OZ, and each of these rotations may be replaced by a 
translation and a rotation about a parallel axis through the center 
M of the path of the electron. Let us call the velocities of the 
electron belonging to these rotations ¢0, 010; Vic. It is clear that the 
two latter components are perpendicular to v,, so that they do not 
contribute anything to the scalar product (wv, . ?,). The same may 
be said of the component of the translatory velocity perpendicular 
to the plane of that circle. As to the translatory velocity in this 
plane, it may contribute a term to (#,,7,) in the case of one elec- 
tron, but it is easily found that these contributions compensate each 
other, when » electrons are moving in the same circle, the reason 
