of the crystals, can be tested[A]: I
purpose that these and many other thoughts which arise respecting specific
inductive action and the polarity of the particles of dielectric matter,
shall be put to the proof as soon as I can find time.

[A] Refer for this investigation to 1680-1698.--_Dec. 1838._

1317. Hoping that this apparatus will form an instrument of considerable
use, I beg to propose for it (at the suggestion of a friend) the name of
_Differential Inductometer_.

_Royal Institution,
March 29, 1838._

TWELFTH SERIES.

S 18. _On Induction (continued)._ P vii. _Conduction, or conductive
discharge._ P viii. _Electrolytic discharge._ P ix. _Disruptive
discharge--Insulation--Spark--Brush--Difference of discharge at the
positive and negative surfaces of conductors._

Received January 11,--Read February 8, 1838.

1318. I Proceed now, according to my promise, to examine, by the great
facts of electrical science, that theory of induction which I have ventured
to put forth (1165. 1295. &c.). The principle of induction is so universal
that it pervades all electrical phenomena; but the general case which I
purpose at present to go into consists of insulation traced into and
terminating with discharge, with the accompanying effects. This case
includes the various _modes_ of discharge, and also the condition and
characters of a current; the elements of magnetic action being amongst the
latter. I shall necessarily have occasion to speak theoretically, and even
hypothetically; and though these papers profess to be experimental
researches, I hope that, considering the facts and investigations contained
in the last series in support of the particular view advanced, I shall not
be considered as taking too much liberty on the present occasion, or as
departing too far from the character which they ought to have, especially
as I shall use every opportunity which presents itself of returning to that
strong test of truth, experiment.

1319. Induction has as yet been considered in these papers only in cases of
insulation; opposed to insulation is _discharge_. The action or effect
which may be expressed by the general term _discharge_, may take place, as
far as we are aware at present, in several modes. Thus, that which is
called simply _conduction_ involves no chemical action, and apparently no
displacement of the particles concerned. A second mode may be called
_electrolytic discharge_; in it chemical action does o