ric force has travelled through it
to a certain distance, we can, by removing the coercitive (which is at the
same time the inductive) force, cause it to return upon its path and
reappear in its first place (1245. 1246.). Here induction appears to be a
necessary preliminary to conduction. It of itself brings the contiguous
particles of the dielectric into a certain condition, which, if retained by
them, constitutes _insulation_, but if lowered by the communication of
power from one particle to another, constitutes _conduction_.

1324. If _glass_ or _shell-lac_ be the substances under consideration, the
same capabilities of suffering either induction or conduction through them
appear (1233. 1239. 1247.), but not in the same degree. The conduction
almost disappears (1239. 1242.); the induction therefore is sustained, i.e.
the polarized state into which the inductive force has brought the
contiguous particles is retained, there being little discharge action
between them, and therefore the _insulation_ continues. But, what discharge
there is, appears to be consequent upon that condition of the particles
into which the induction throws them; and thus it is that ordinary
insulation and conduction are closely associated together or rather are
extreme cases of one common condition.

1325. In ice or water we have a better conductor than spermaceti, and the
phenomena of induction and insulation therefore rapidly disappear, because
conduction quickly follows upon the assumption of the inductive state. But
let a plate of cold ice have metallic coatings on its sides, and connect
one of these with a good electrical machine in work, and the other with the
ground, and it then becomes easy to observe the phenomena of induction
through the ice, by the electrical tension which can be obtained and
continued on both the coatings (419. 426.). For although that portion of
power which at one moment gave the inductive condition to the particles is
at the next lowered by the consequent discharge due to the conductive act,
it is succeeded by another portion of force from the machine to restore the
inductive state. If the ice be converted into water the same succession of
actions can be just as easily proved, provided the water be distilled, and
(if the machine be not powerful enough) a voltaic battery be employed.

1326. All these considerations impress my mind strongly with the
conviction, that insulation and ordinary conduction cannot be proper