XIII
233
EXPERIMENTS ON THE CATHODE DISCHARGE
discharge and a much lower potential, the potential of the
gold leaves would be able to follow these fluctuations, but the
potential of the metal case would not; the quantity of
electricity upon the latter would always be that corresponding
to the mean potential value, and the divergence of the gold
leaves would therefore be proportional to the square of the
difference between the potential and its mean value. That an
intermittent discharge does actually produce such divergence
was shown as follows. The resistance through which the
battery-current flowed was gradually increased more and more;
when it had attained a certain very high value the discharge
began to exhibit the criteria of discontinuity given by
Hittorf; and at the same time the gold leaves began to
diverge distinctly. The same result was attained by artificial
interruption of the battery-current. Here again the method
of testing used must fail as soon as the number of interrup-
tions per second reaches a certain value, but this value can be
approximately calculated. The partial discharges, if any such
were present, could only consist in discharges of the electricity
accumulated on the cathode and the gold leaves in metallic
connection with it. The capacity of this system was certainly
not greater than that of a sphere of 20 mm. radius. The
fluctuation of potential at each discharge could not exceed the
value of 90 Daniells, for it was found that such a difference of
potential between the gold leaves and the surrounding case
could be recognised by a perceptible divergence. Now a
thousand discharges per second of a sphere of 20 mm. radius,
charged each time to a potential of 90 Daniells, would just
correspond to the current produced by 1 Daniell through
about 5,000,000 S.U. But the currents used in the experi-
ments were about equal to that sent by a Daniell through
100 S.U. Hence if they consisted of partial discharges, the
frequency of the latter must have amounted to at least 50
millions per second.
6. The anode of the gas-tube used was connected by a
thick metallic wire with one plate of a Kohlrausch condenser,
and the cathode was connected with the other plate by a very
thin silver wire of 8 cm. length and about 0.8 S.U. resistance.
To the latter was attached an arrangement with mirror and scale,
by means of which an exceedingly small extension, and there-