200 
HINTON. 
explanation—the laws of elasticity, which Maxwell assumes, 
are not those of ordinary matter. And, to take another in¬ 
stance : a magnetic pole in the neighborhood of a current 
tends to move. Maxwell has shown that the pressures on 
it are analogous to the velocities in a liquid which would 
exist if a vortex took the place of the electric current; but 
we cannot point out the definite mechanical explanation of 
these pressures. There must be some mode of motion of a 
bod}^ or of the medium in virtue of which a body is said to 
be electrified. 
Take the ions which convey charges of electricity 500 
times greater in proportion to their mass than are carried 
by the molecules of hydrogen in electrolysis. In respect of 
what motion can these ions be said to be electrified ? It 
can be shown that the energy they possess is not energy 
of rotation. Think of a short rod rotating. If it is turned 
over it is found to be rotating in the opposite direction. Now, 
if rotation in one direction corresponds to positive electricity, 
rotation in the opposite direction corresponds to negative elec¬ 
tricity, and the smallest electrified particles would have their 
charges reversed by being turned over—an absurd supposi¬ 
tion. 
If we fix on a mode of motion as a definition of elec¬ 
tricity, we must have two varieties of it, one for positive and 
one for negative ; and a body possessing the one kind must 
not become possessed of the other by any change in its po¬ 
sition. 
All three-dimensional motions are compounded of rota¬ 
tions and translations, and none of them satisfy this first 
condition for serving as a definition of electricity. 
But consider the double rotation of the A and B kinds. 
A body rotating with the A motion cannot have its motion 
transformed into the B kind by being turned over in any 
way. Suppose a body has the rotation x to y and z to w. 
Turning it about the x y plane, we reverse the direction of 
the motion x to y. But we also reverse the z to w motion, 
for the point at the extremity of the positive z axis is now at 
