1904—5.] Mr J. Fraser on Electricity based on Bubble Atom. 697 
under induction, owing to the negative body’s lack of electricity. 
The greater pressure on the other end squeezes the motion to 
that end where it has freer play, and if the far end be now 
momentarily connected to earth, its loss of motion will be 
supplied from the earth’s great reservoir, making that end neutral 
(or even positive, if it he very near the inducing body) ; and if, 
now, the electrified body he removed, the whole cylinder will 
be found to be positively charged, because, upon equalisation of 
pressure over the whole cylinder, the excess of motion at the 
end which had been under induction is now spread equally over 
the whole cylinder. If, now, the cylinder he connected to earth, 
the excess of motion escapes to the earth from whence it came. 
We will now suppose the electrified body to he positive. In 
that case the end of the cylinder under induction will he under 
greater pressure than the other, squeezing the greater part of 
the motion to the far end — the end under induction becoming 
negative and the far end positive. This will be analogous to 
the case of a person stepping on the end of a highly elastic tube 
full of air or water. The air, or the water, would be partly 
squeezed to the end of least pressure, which would become 
distended. If, now, the far end of the cylinder be momentarily 
connected to earth while the other is still under induction, its 
excess of motion will escape to the earth, leaving that end neutral 
(or negative, if close .to the inducing body) ; and on the removal 
of the inducing body the whole cylinder will be found to be 
negatively charged. Obviously, this is because the quantity of 
motion left at the neutral end is insufficient for the whole body, 
a part of whose motion has been driven to earth, by the excess 
of pressure on one of its ends, but if it now be connected to earth, 
it will be supplied with a quantity of motion equivalent to that 
lost. 
24. Why cannot a charge reside on the interior surface of a 
hollow conductor except an inducing body be insulated in the 
interior ? If the foregoing principles have been thoroughly grasped, 
the reason for the above will be easily seen. Suppose a positive 
charge to be given, then the atoms in the interior, as well as those 
on the exterior, would begin to expand, increasing the radiation of 
electricity there, which, with the tendency to expansion, would 
