interference by performing the
whole process of comparison as quickly as possible, and taking the force of
app. ii. immediately after the division, before any sensible diminution of
the tension arising from the assumption of the peculiar state could be
produced; and I have assumed that as about three minutes pass between the
first charge of app. i. and the division, and three minutes between the
division and discharge, when the force of the non-transferable electricity
is measured, the contrary tendencies for those periods would keep that
apparatus in a moderately steady and uniform condition for the latter
portion of time.

1251. The particular action described occurs in the shell-lac of the stems,
as well as in the _dielectric_ used within the apparatus. It therefore
constitutes a cause by which the outside of the stems may in some
operations become charged with electricity, independent of the action of
dust or carrying particles (1203.).

P v. _On specific induction, or specific inductive capacity._

1252. I now proceed to examine the great question of specific inductive
capacity, i.e. whether different dielectric bodies actually do possess any
influence over the degree of induction which takes place through them. If
any such difference should exist, it appeared to me not only of high
importance in the further comprehension of the laws and results of
induction, but an additional and very powerful argument for the theory I
have ventured to put forth, that the whole depends upon a molecular action,
in contradistinction to one at sensible distances.

The question may be stated thus: suppose A an electrified plate of metal
suspended in the air, and B and C two exactly similar plates, placed
parallel to and on each side of A at equal distances and uninsulated; A
will then induce equally towards B and C. If in this position of the plates
some other dielectric than air, as shell-lac, be introduced between A and
C, will the induction between them remain the same? Will the relation of C
and B to A be unaltered, notwithstanding the difference of the dielectrics
interposed between them?[A]

[A] Refer for the practical illustration of this statement to the
supplementary note commencing 1307, &c.--_Dec. 1838._

1253. As far as I recollect, it is assumed that no change will occur under
such variation of circumstances, and that the relations of B find C to A
depend entirely upon their distance. I only remember one experi