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XIII
EXPERIMENTS ON THE CATHODE DISCHARGE
O
fore a very slight elevation of temperature produced in the
wire by a current traversing it, could be detected. A rise of
temperature of C. could be perceived; the current produc-
ing this rise was equal to To Daniell/S.U. The wire thus
formed a sort of dynamometer without any coil, and will in
future be referred to as such.¹ Now the battery-current, which
in these experiments was as strong as Daniell/S.U., could
be conducted to the cathode in either of two ways. Either it
flowed in between the condenser and the dynamometer, in
which case it flowed through the latter, and produced in it a
deflection of four to five scale-divisions; or else it flowed in
between the dynamometer and the gas-tube, in which case not
the slightest deflection of the dynamometer could be perceived,
certainly not a deflection of quarter of a scale-division.
Now if the current had been composed of partial discharges, a
continual charging and discharging of the condenser would
have taken place, and therefore an alternating current would
have flowed through the dynamometer. The deflection pro-
duced by this alternating current would certainly have
amounted to a half of that produced by the whole current.
Here again I caused intermittence by an artificial interruption
of the external circuit. The result was that the dynamometer
was deflected whether the current flowed in the one way or
the other; and the deflections were even larger (six to eight
scale-divisions) than when the current was not interrupted.
The explanation of this paradox is that the artificial interrup-
tion produces condenser-discharges which act more strongly upon
the dynamometer. The criterion here used only ceases to be
applicable when the separate partial discharges follow each
other so rapidly that the electric waves corresponding to
them are no longer able to traverse the silver wire of the
dynamometer in the interval. The requisite rapidity can be
estimated in various ways; even the lowest estimate gives
many thousand millions per second.
second. The following is perhaps
the simplest way. If the electric wave does not traverse the
dynamometer wire, then each partial discharge consists simply
of a discharge of the electricity stored upon the cathode. The
capacity of the cathode was less than that of a sphere of 2 cm.
radius. During a single discharge the variation of potential
¹ See description of the apparatus in XI. p. 211.