_The Electric Sparks._

When the prime conductor is situated in its proper place, and
electrified by whirling the cylinder, if a metallic wire, with a ball
at its extremity, or the knuckle or a finger be presented to the prime
conductor, a spark will be seen to issue between them, which will be
more vivid, and will be attended with a greater or less explosion,
according as the ball is larger. The strongest and most vivid sparks
are drawn from that end or side of the prime conductor which is
farthest from the cylinder. The sparks have the same appearance
whether they be taken from the positive or negative conductor; they
sometimes appear like a long line of fire reaching from the prime
conductor to the opposed body, and often (particularly when the spark
is long, and different conducting substances in the line of its
direction) it will have the appearance of being bent to sharp angles
in different places, exactly resembling a flash of lightning.

The figure of a spark varies with the superficial dimensions of the
part from which it is taken. If it be drawn from a ball of two or
three inches in diameter, it will have the appearance of a straight
line; but if the ball from which it is drawn be much smaller, as half
an inch in diameter, it will assume the zig-zag appearance above
mentioned.

_Dancing Balls._

Take a common tumbler or glass jar, and having placed a brass ball in
one of the holes of the prime conductor, set the machine in motion,
and let the balls touch the inside of the tumbler; while the ball
touches only one point, no more of the surface of the glass will be
electrified, but by moving the tumblers about, so as to make the ball
touch many points successively, all the points will be electrified, as
will appear by turning down the tumbler over a number of pith or cork
balls placed on a table. These balls will immediately begin to fly
about.

_The Leyden Phial._

When a nail or piece of thick brass wire, &c., is put into a small
apothecary's phial, and electrified, remarkable effects follow; but
the phial must be very dry or warm. Rub it once beforehand with your
finger, on which put some pounded chalk. If a little mercury, or a few
drops of spirit of wine, be put into it, the experiment succeeds the
better. As soon as this phial and nail are removed from the
electrifying glass, or the prime conductor, to which it has been
exposed, is taken away, it throws out a stream of flame so long, that