equal proportion. So does
evolution by chemical action, notwithstanding the great diversity of bodies
which may be employed, and the enormous quantity of electricity which can
in this manner be evolved (371. 376. 861. 868. 961.). The more promising
cases of change of state, whether by evaporation, fusion, or the reverse
processes, still give both forms of the power in _equal_ proportion; and
the cases of splitting of mica and other crystals, the breaking of sulphur,
&c., are subject to the same law of limitation.

1177. As far as experiment has proceeded, it appears, therefore, impossible
either to evolve or make disappear one electric force without equal and
corresponding change in the other. It is also equally impossible
experimentally to charge a portion of matter with one electric force
independently of the other. Charge always implies _induction_, for it can
in no instance be effected without; and also the presence of the _two_
forms of power, equally at the moment of the development and afterwards.
There is no _absolute_ charge of matter with one fluid; no latency of a
single electricity. This though a negative result is an exceedingly
important one, being probably the consequence of a natural impossibility,
which will become clear to us when we understand the true condition and
theory of the electric power.

1178. The preceding considerations already point to the following
conclusions: bodies cannot be charged absolutely, but only relatively, and
by a principle which is the same with that of _induction_. All _charge_ is
sustained by induction. All phenomena of _intensity_ include the principle
of induction. All _excitation_ is dependent on or directly related to
induction. All _currents_ involve previous intensity and therefore previous
induction. INDUCTION appears to be the essential function both the first
development and the consequent phenomena of electricity.

P iii. _Electrometer and inductive apparatus employed._

1179. Leaving for a time the further consideration of the preceding facts
until they can be collated with other results bearing directly on the great
question of the nature of induction, I will now describe the apparatus I
have had occasion to use; and in proportion to the importance of the
principles sought to be established is the necessity of doing this so
clearly, as to leave no doubt of the results behind.

1180. _Electrometer._--The measuring instrument I have employed has been
the t