he small ball rendered _positive_ inducteously giving a
spark nearly twice as long as that produced when it was charged positive
inductrically, and a corresponding difference, though not, under the
circumstances, to the same extent, was manifest, when it was rendered
_negative_[A].

[A] For similar experiments on different gases, see 1518.--_Dec. 1838._

1489. Other results are, that the small ball rendered positive gives a much
longer spark than when it is rendered negative, and that the small ball
rendered negative gives a brush more readily than when positive, in
relation to the effect produced by increasing the distance between the two
balls.

1490. When the interval was below 0.4 of an inch, so that the small ball
should give sparks, whether positive or negative, I could not observe that
there was any constant difference, either in their ready occurrence or the
number which passed in a given time. But when the interval was such that
the small ball when negative gave a brush, then the discharges from it, as
separate negative brushes, were far more numerous than the corresponding
discharges from it when rendered positive, whether those positive
discharges were as sparks or brushes.

1491. It is, therefore, evident that, when a ball is discharging
electricity in the form of brushes, the brushes are far more numerous, and
each contains or carries off far less electric force when the electricity
so discharged is negative, than when it is positive.

1492. In all such experiments as those described, the point of change from
spark to brush is very much governed by the working state of the electrical
machine and the size of the conductor connected with the discharging ball.
If the machine be in strong action and the conductor large, so that much
power is accumulated quickly for each discharge, then the interval is
greater at which the sparks are replaced by brushes; but the general effect
is the same[A].

[A] For similar experiments in different gases, see 1510-1517.--_Dec.
1838._

1493. These results, though indicative of very striking and peculiar
relations of the electric force or forces, do not show the relative degrees
of charge which the small ball acquires before discharge occurs, i.e. they
do not tell whether it acquires a higher condition in the negative, or in
the positive state, immediately preceding that discharge. To illustrate
this important point I arranged two places of discharge as represented,