d tend to
return to their normal or natural condition.

1672. That being as wholes conductors, they can readily be charged, either
_bodily_ or _polarly_.

1673. That particles which being contiguous[A] are also in the line of
inductive action can communicate or transfer their polar forces one to
another _more_ or _less_ readily.

[A] See note to 1164.--_Dec. 1838._

1674. That those doing so less readily require the polar forces to be
raised to a higher degree before this transference or communication takes
place.

1675. That the _ready_ communication of forces between contiguous particles
constitutes _conduction_, and the _difficult_ communication _insulation_;
conductors and insulators being bodies whose particles naturally possess
the property of communicating their respective forces easily or with
difficulty; having these differences just as they have differences of any
other natural property.

1676. That ordinary induction is the effect resulting from the action of
matter charged with excited or free electricity upon insulating matter,
tending to produce in it an equal amount of the contrary state.

1677. That it can do this only by polarizing the particles contiguous to
it, which perform the same office to the next, and these again to those
beyond; and that thus the action is propagated from the excited body to the
next conducting mass, and there renders the contrary force evident in
consequence of the effect of communication which supervenes in the
conducting mass upon the polarization of the particles of that body
(1675.).

1678. That therefore induction can only take place through or across
insulators; that induction is insulation, it being the necessary
consequence of the state of the particles and the mode in which the
influence of electrical forces is transferred or transmitted through or
across such insulating media.

1679. The particles of an insulating dielectric whilst under induction may
be compared to a series of small magnetic needles, or more correctly still
to a series of small insulated conductors. If the space round a charged
globe were filled with a mixture of an insulating dielectric, as oil of
turpentine or air, and small globular conductors, as shot, the latter being
at a little distance from each other so as to be insulated, then these
would in their condition and action exactly resemble what I consider to be
the condition and action of the particles of the insulating dielectric