as filaments or particles
of dust, the effect will often be very ready, and the consequent attraction
immediate.

1568. The effect described is also probably influential in causing those
variations in spark discharge referred to in the last series (1386. 1390.
1391.): for if a particle of dust were drawn towards the axis of induction
between the balls, it would tend, whilst at some distance from that axis,
to commence discharge at itself, in the manner described (1566.), and that
commencement might so far facilitate the act (1417. 1420.) as to make the
complete discharge, as spark, pass through the particle, though it might
not be the shortest course from ball to ball. So also, with equal balls at
equal distances, as in the experiments of comparison already described
(1493. 1506.), a particle being between one pair of balls would cause
discharge there in preference; or even if a particle were between each,
difference of size or shape would give one for the time a predominance over
the other.

1569. The power of particles of dust to carry off electricity in cases of
high tension is well known, and I have already mentioned some instances of
the kind in the use of the inductive apparatus (1201.). The general
operation is very well shown by large light objects, as the toy called the
electrical spider; or, if smaller ones are wanted for philosophical
investigation, by the smoke of a glowing green wax taper, which, presenting
a successive stream of such particles, makes their course visible.

1570. On using oil of turpentine as the dielectric, the action and course
of small conducting carrying particles in it can be well observed. A few
short pieces of thread will supply the place of carriers, and their
progressive action is exceedingly interesting.

1571. A very striking effect was produced on oil of turpentine, which,
whether it was due to the carrying power of the particles in it, or to any
other action of them, is perhaps as yet doubtful. A portion of that fluid
in a glass vessel had a large uninsulated silver dish at the bottom, and an
electrified metal rod with a round termination dipping into it at the top.
The insulation was very good, and the attraction and other phenomena
striking. The rod end, with a drop of gum water attached to it, was then
electrified in the fluid; the gum water soon spun off in fine threads, and
was quickly dissipated through the oil of turpentine. By the time that four
drops had in this wa