XIII
229
EXPERIMENTS ON THE CATHODE DISCHARGE
symptoms of intermittence. They were in no way affected by
the approach of a conductor; a telephone introduced into the
circuit did not sound; the tubes themselves gave out no
sound, nor could the image of the discharge be decomposed by
a rotating mirror into separate images.
1. The above-mentioned experiments of Warren de la Rue¹
were first repeated. The battery-current, in addition to pass-
ing through the gas-tube, was sent through the primary or
secondary coil of various small induction-coils, the free coil
being closed through a dynamometer or galvanometer. In
no case did I obtain a deflection of these instruments, such as
would indicate a surging induction current due to inter-
mittence of the battery current. However, this does not
prove much.
Consider first the dynamometric effect of the
induced currents. At first this certainly increases with the
number of interruptions of the inducing current; but if this
number becomes very large, the dynamometric effect does not
become infinite. Since the separate induction impulses are
impeded by self-induction, the dynamometric effect approaches
a fixed limit; but even this maximum effect could scarcely be
perceived with the dynamometer which I used. And as far
as the effect on the galvanometer is concerned, the accepted
theory of induction does not indicate that any effect should be
expected, even if the current at each separate discharge sinks
more rapidly than it rises. I was only induced to perform
these experiments by the fact that results to the contrary had
been obtained by Warren de la Rue and Müller. Unfor-
tunately I did not succeed in reproducing the phenomenon
observed by them. When the galvanometer had been removed
from the direct magnetic action of the coil through which the
current flowed, no permanent deflection could be perceived
after the battery current was closed, although the induction
impulse on opening and closing the current drove the needle
beyond the visible scale.2
2. In addition to the tube and a large liquid resistance,
1 Ann. de Chim. et de Phys., series 5, 24, p. 461, 1881; and Phil. Trans.
169, p. 225, 1878.
It is certain that any deflection of the needle produced cannot be regarded
as due to any normal galvanometric action. More probably it was of the nature
of "doppelsinnige Ablenkung," in which case the galvanometer would be acting
as a very delicate dynamometer.