The passing of the electrical fire from the upper to the lower
part[31] of the bottle, to restore the equilibrium, is rendered
strongly visible by the following pretty experiment. Take a book
whose covering is filletted with gold; bend a wire of eight or ten
inches long, in the form of (_m_) Fig. 5; slip it on the end of
the cover of the book, over the gold line, so as that the shoulder
of it may press upon one end of the gold line, the ring up, but
leaning towards the other end of the book. Lay the book on a glass
or wax[32], and on the other end of the gold lines set the bottle
electrised; then bend the springing wire, by pressing it with a
stick of wax till its ring approaches the ring of the bottle wire,
instantly there is a strong spark and stroke, and the whole line
of gold, which completes the communication, between the top and
bottom of the bottle, will appear a vivid flame, like the sharpest
lightning. The closer the contact between the shoulder of the wire,
and the gold at one end of the line, and between the bottom of the
bottle and the gold at the other end, the better the experiment
succeeds. The room should be darkened. If you would have the whole
filletting round the cover appear in fire at once, let the bottle and
wire touch the gold in the diagonally opposite corners.