esisting discharge; it is a measure, consequently, of
the conservative power of the dielectric, which in its turn may be
considered as becoming a measure, and therefore a representative of the
intensity of the electric forces in activity.

1363. Many philosophers have examined the circumstances of this limiting
action in air, but, as far as I know, none have come near Mr. Harris as to
the accuracy with, and the extent to, which he has carried on his
investigations[A]. Some of his results I must very briefly notice,
premising that they are all obtained with the use of air as the
_dielectric_ between the conducting surfaces.

[A] Philosophical Transactions, 1834, p. 225.

1364. First as to the _distance_ between the two balls used, or in other
words, the _thickness_ of the dielectric across which the induction was
sustained. The quantity of electricity, measured by a unit jar, or
otherwise on the same principle with the unit jar, in the charged or
inductive ball, necessary to produce spark discharge, was found to vary
exactly with the distance between the balls, or between the discharging
points, and that under very varied and exact forms of experiment[A].

[A] Philosophical Transactions, 1834, p. 225.

1365. Then with respect to variation in the _pressure_ or _density_ of the
air. The quantities of electricity required to produce discharge across a
_constant_ interval varied exactly with variations of the density; the
quantity of electricity and density of the air being in the same simple
ratio. Or, if the quantity was retained the same, whilst the interval and
density of the air were varied, then these were found in the inverse simple
ratio of each other, the same quantity passing across twice the distance
with air rarefied to one-half[A].

[A] Philosophical Transactions, 1834, p.229.

1366. It must be remembered that these effects take place without any
variation of the _inductive_ force by condensation or rarefaction of the
air. That force remains the same in air[A], and in all gases (1284. 1292.),
whatever their rarefaction may be.

[A] Philosophical Transactions, 1834, p. 237, 244.

1367. Variation of the _temperature_ of the air produced no variation of
the quantity of electricity required to cause discharge across a given
interval[A].

[A] Philosophical Transactions, 1834, p. 230

Such are the general results, which I have occasion for at present,
obtained by Mr. Harris, and they appear to me