tive condition, gradually increasing in intensity for
some time, in the same manner as before. The first negative condition of
the surface opposite the positive charging ball is a natural consequence of
the state of things, the charging ball being in contact with the shell-lac
only in a few points. It does not interfere with the general result and
peculiar state now under consideration, except that it assists in
illustrating in a very marked manner the ultimate assumption by the
surfaces of the shell-lac of an electrified condition, similar to that of
the metallic surfaces opposed to or against them.

1239. _Glass_ was then examined with respect to its power of assuming this
peculiar state. I had a thick flint-glass hemispherical cup formed, which
would fit easily into the space _o_ of the lower hemisphere (1188. 1189.);
it had been heated and varnished with a solution of shell-lac in alcohol,
for the purpose of destroying the conducting power of the vitreous surface
(1254.). Being then well-warmed and experimented with, I found it could
also assume the _same state_, but not apparently to the same degree, the
return action amounting in different cases to quantities from 6 deg. to 18 deg..

1240. _Spermaceti_ experimented with in the same manner gave striking
results. When the original charge had been sustained for fifteen or twenty
minutes at about 500 deg., the return charge was equal to 95 deg. or 100 deg., and was
about fourteen minutes arriving at the maximum effect. A charge continued
for not more than two or three seconds was here succeeded by a return
charge of 50 deg. or 60 deg.. The observations formerly made (1234.) held good with
this substance. Spermaceti, though it will insulate a low charge for some
time, is a better conductor than shell-lac, glass, and sulphur; and this
conducting power is connected with the readiness with which it exhibits the
particular effect under consideration.

1241. _Sulphur._--I was anxious to obtain the amount of effect with this
substance, first, because it is an excellent insulator, and in that respect
would illustrate the relation of the effect to the degree of conducting
power possessed by the dielectric (1247.); and in the next place, that I
might obtain that body giving the smallest degree of the effect now under
consideration for the investigation of the question of specific inductive
capacity (1277.).

1242. With a good hemispherical cup of sulphur cast solid and sound,