even
only a few inches off, the tension is still beneath that point. But suppose
the rod to be charged positively, a particle of air A, fig. 118, next it,
being polarized, and having of course its negative force directed towards
the rod and its positive force outwards; the instant that discharge takes
place between the positive force of the particle of the rod opposite the
air and the negative force of the particle of air towards the rod, the
whole particle of air becomes positively electrified; and when, the next
instant, the discharged part of the rod resumes its positive state by
conduction from the surface of metal behind, it not only acts on the
particles beyond A, by throwing A into a polarized state again, but A
itself, because of its charged state, exerts a distinct inductive act
towards these further particles, and the tension is consequently so much
exalted between A and B, that discharge takes place there also, as well as
again between the metal and A.

1435. In addition to this effect, it has been shown, that, the act of
discharge having once commenced, the whole operation, like a case of
unstable equilibrium, is hastened to a conclusion (1370. 1418.), the rest
of the act being facilitated in its occurrence, and other electricity than
that which caused the first necessary tension hurrying to the spot. When,
therefore, disruptive discharge has once commenced at the root of a brush,
the electric force which has been accumulating in the conductor attached to
the rod, finds a more ready discharge there than elsewhere, and will at
once follow the course marked out as it were for it, thus leaving the
conductor in a partially discharged state, and the air about the end of the
wire in a charged condition; and the time necessary for restoring the full
charge of the conductor, and the dispersion of the charged air in a greater
or smaller degree, by the joint forces of repulsion from the conductor and
attraction towards the walls of the room, to which its inductive action is
directed, is just that time which forms the interval between brush and
brush (1420. 1427. 1431. 1447.).

1436. The words of this description are long, but there is nothing in the
act or the forces on which it depends to prevent the discharge being
_instantaneous_, as far as we can estimate and measure it. The
consideration of _time_ is, however, important in several points of view
(1418.), and in reference to disruptive discharge, it seemed from th