[Illustration: FIG. 25.--IMPROVED EXPERIMENTAL BULB.]

Again, in another of the early experiments, a bulb was used as
illustrated in Fig. 12. In this instance, by touching the bulb with
one or two fingers, one or two shadows of the stem inside were
projected against the glass, the touch of the finger producing the
same result as the application of an external negative electrode under
ordinary circumstances.

In all these experiments the action was intensified by augmenting the
capacity at the end of the lead connected to the terminal. As a rule,
it is not necessary to resort to such means, and would be quite
unnecessary with still higher frequencies; but when it _is_ desired,
the bulb, or tube, can be easily adapted to the purpose.

[Illustration: FIG. 26.--IMPROVED BULB WITH INTENSIFYING REFLECTOR.]

In Fig. 24, for example, an experimental bulb L is shown, which is
provided with a neck n on the top for the application of an external
tinfoil coating, which may be connected to a body of larger surface.
Such a lamp as illustrated in Fig. 25 may also be lighted by
connecting the tinfoil coating on the neck n to the terminal, and the
leading-in wire w to an insulated plate. If the bulb stands in a
socket upright, as shown in the cut, a shade of conducting material
may be slipped in the neck n, and the action thus magnified.

A more perfected arrangement used in some of these bulbs is
illustrated in Fig. 26. In this case the construction of the bulb is
as shown and described before, when reference was made to Fig. 19. A