no chemical process, no consumption of material, but merely a transfer
of energy, and which would, in all probability emit more light and
less heat than ordinary flames.

[Illustration: FIG. 8.--EFFECT PRODUCED BY CONCENTRATING STREAMS.]

The luminous intensity of the streams is, of course, considerably
increased when they are focused upon a small surface. This may be
shown by the following experiment:

I attach to one of the terminals of the coil a wire w (Fig. 8), bent
in a circle of about 30 centimetres in diameter, and to the other
terminal I fasten a small brass sphere s, the surface of the wire
being preferably equal to the surface of the sphere, and the centre of
the latter being in a line at right angles to the plane of the wire
circle and passing through its centre. When the discharge is
established under proper conditions, a luminous hollow cone is formed,
and in the dark one-half of the brass sphere is strongly illuminated,
as shown in the cut.

By some artifice or other, it is easy to concentrate the streams upon
small surfaces and to produce very strong light effects. Two thin
wires may thus be rendered intensely luminous.

In order to intensify the streams the wires should be very thin and
short; but as in this case their capacity would be generally too small
for the coil--at least, for such a one as the present--it is necessary
to augment the capacity to the required value, while, at the same
time, the surface of the wires remains very small. This may be done in
many ways.