means of an
india-rubber pipe, or otherwise, with a supply of water in a bottle, and
pinch the tubes with a screw-clip until two equal jets of water are
formed. So hold the nozzles that these meet in their smooth portions at
every small angle. They will then for a short time bounce away from one
another without mixing. If the air is very dusty, if the water is not
clean, or if air-bubbles are carried along in the pipes, the two jets
will at once join together. In the arrangement that I used in the
lantern, the two nozzles were nearly horizontal, one was about half an
inch above the other, and they were very slightly converging. They were
fastened in their position by melting upon them a little sealing-wax.
India-rubber pipes connected them with two bottles about six inches
above them, and screw-clips were used to regulate the supply. One of the
bottles was made to stand on three pieces of sealing-wax to electrically
insulate it, and the corresponding nozzle was only held by its
sealing-wax fastening. The water in the bottles had been filtered, and
one was coloured blue. If these precautions are taken, the jets will
remain distinct quite long enough, but are instantly caused to recombine
by a piece of electrified sealing-wax six or eight feet away. They may
be separated again by touching the water issuing near one nozzle with
the finger, which deflects it; on quietly removing the finger the jet
takes up its old position and bounces off the other as before. They can
thus be separated and made to combine ten or a dozen times in a minute.

_Fountain and Intermittent Light._

This can be successfully shown to a large number of people at once only
by using an electric arc, but there is no occasion to produce this light
if not more than one person at a time wishes to see the evolution of the
drops. It is then merely necessary to make the fountain play in front of
a bright background such as the sky, to break it up with a tuning-fork
or other musical sound as described, and then to look at it through a
card disc equally divided near the edge into spaces about two or three
inches wide, with a hole about one-eighth of an inch in diameter between
each pair of spaces. A disc of card five inches in diameter, with six
equidistant holes half an inch from the edge, answers well. The disc
must be made to spin by any means very regularly at such a speed that
the tuning-fork, or stretched string if this be used, when looked at
through