the same
way that the particles of air were polarized; that is, the two kinds of
electricities in the aetherial atom are separated, the negative being on
that side nearest to the sun, and the positive on the side further away.
In this way the whole aetherial medium would be polarized, and any body
in the field would be electrified by induction, with the result that the
side nearest the sun would be negatively charged, and the opposite side
positively charged.

Thus let _S_ (Figs. 10 and 11) be the sun, and the circles represent
equipotential surfaces, then one half of every surface would be
negatively electrified and the other half positively electrified, that
is, assuming the sun to be a positively electrified body.

If _M_ represents Mercury, _V_ represents Venus, and _E_ represents the
Earth (Fig. 10), then it can readily be seen that all these would be
negatively electrified on the side facing the sun; and, as they rotate
on their axes, each part of the planet would be positively and
negatively electrified once each day.

We are assuming that the medium is at rest, but according to our
conception in Art. 44, all the aetherial atoms are in rotation on their
axes, in the same way that the earth rotates on its axis, so that each
of these aetherial atoms would present different parts of its surface to
the sun as it rotates on its axis; but, as that does not affect the
principle of induction, such a fact need not now be fully considered.

Let us now ask, What is the result of all the planets becoming
electrified bodies in the same way that the sun is an electrified body?
Arguing from experience, we come to the conclusion that each planet must
also possess its electric field, which also must have its lines of
force, its different potentials at different distances, and its
equipotential surfaces. So that Mercury, Venus, the Earth, Mars,
Jupiter, Saturn, Uranus, and Neptune all have their electric fields,
with their own lines of force, and with their equipotential surfaces.

If we carry the analogy further still, then it can also be proved that
the Earth, and those planets which have moons or satellites, also act
inductively on their satellites, with the result that they too become
electrified bodies, with their own smaller electric fields and lines of
force. This may seem at first sight a little confusing, but the
confusion will gradually disappear if we will look at it carefully for a
moment or two. Let us endeavour