The Illuminated Vacuum

Take a tall receiver that is very dry, and fix through the top of it,
with cement, a blunt wire; then exhaust the receiver, and present the
knob of the wire to the conductor, and every spark will pass through
the vacuum in a broad stream of light, visible through the whole
length of the receiver, let it be as tall as it will. This generally
divides into a variety of beautiful rivulets, which are continually
changing their course, uniting and dividing again in the most pleasing
manner.

If a jar be discharged through this vacuum, it presents the appearance
of a very dense body of fire, darting directly through the centre of
the vacuum, without touching the sides; whereas, when a single spark
passes through, it generally goes more or less to the side, and a
finger placed on the outside of the glass will draw it wherever a
person pleases. If the vessel be grasped by both hands, every spark is
felt like the pulsation of a large artery; and all the fire makes
towards the hands. This pulsation is even felt at some distance from
the receiver, and a light is seen between the hand and the glass.

All this while, the pointed wire is supposed to be electrified
positively; if it be electrified negatively, the appearance is
astonishingly different; instead of streams of fire, nothing is seen
but one uniform luminous appearance, like a white cloud, or the milky
way in a clear star-light night. It seldom reaches the whole length
of the vessel, but generally appears only at the end of the wire, like
a lucid ball.

If a small phial be inserted in the neck of a small receiver, so that
the external surface of the glass be exposed to the vacuum, it will
produce a very beautiful appearance. The phial must be coated on the
inside; and while it is charging, at every spark taken from the
conductor into the inside, a flash of light is seen to dart at the
same time from every part of the external surface of the phial, so as
to quite fill the receiver. Upon making the discharge, the light is
seen to run in a much closer body, the whole coming out at once.

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