discharge to them in a much greater decree than
the air particles themselves could do, were carried off by the same causes
which urged those in their course. A similar effect with melted sealing-wax
on a metal point forms an old and well-known experiment.

1589. A drop of gum water in the exhausted receiver of the air-pump was not
sensibly affected in its form when electrified. When air was let in, it
begun to show change of shape when the pressure was ten inches of mercury.
At the pressure of fourteen or fifteen inches the change was more sensible,
and as the air increased in density the effects increased, until they were
the same as those in the open atmosphere. The diminished effect in the rare
air I refer to the relative diminished energy of its current; that
diminution depending, in the first place, on the lower electric condition
of the electrified ball in the rarefied medium, and in the next, on the
attenuated condition of the dielectric, the cohesive force of water in
relation to rarefied air being something like that of mercury to dense air
(1581.), whilst that of water in dense air may be compared to that of
mercury in oil of turpentine (1597.).

1590. When a ball is covered with a thick conducting fluid, as treacle or
syrup, it is easy by inductive action to determine the wind from almost any
part of it (1577.); the experiment, which before was of rather difficult
performance, being rendered facile in consequence of the fluid enabling
that part, which at first was feeble in its action, to rise into an exalted
condition by assuming a pointed form.

1591. To produce the current, the electric intensity must rise and continue
at _one spot_, namely, at the origin of the current, higher than elsewhere,
and then, air having a uniform and ready access, the current is produced.
If no current be allowed (1574.), then discharge may take place by brush or
spark. But whether it be by brush or spark, or wind, it seems very probable
that the initial intensity or tension at which a particle of a given
gaseous dielectric charges, or commences discharge, is, under the
conditions before expressed, always the same (1410.).

1592. It is not supposed that all the air which enters into motion is
electrified; on the contrary, much that is not charged is carried on into
the stream. The part which is really charged may be but a small proportion
of that which is ultimately set in motion (1442.).

1593. When a drop of gum water (15