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XIII
EXPERIMENTS ON THE CATHODE DISCHARGE
neighbourhood of the cathode, was not due to the direct action
of the current, but to the action of the cathode rays. For
without any sudden change it could be gradually transformed
into a quite similar luminescence, situated at a great distance
from the cathode and in a space where the current was zero.
And if we admit that in this special case the cathode light is
not directly produced by the current, we can scarcely assume
that in the general case it is so produced. According to
Goldstein's researches, the cathode light has so many analogies
with the separate positive striæ that it can be regarded as a
degenerated form of such a stria. It is therefore very
improbable that the luminescence of the gas in the positive
striæ is due to any causes other than those which produce
the luminescence in the cathode light. We are thus led to
the assumption, which at first seemed hazardous, that the
luminescence of the gas in the glow discharge is not a direct
effect of the current, but arises indirectly through an absorption
of the cathode rays¹ which are produced by the current.
we could prevent the production of the cathode rays, the gas
would everywhere be as dark as it is in the dark intervals
between the striæ (although the current flows through these
intervening spaces). Conversely, if we could produce the
cathode rays in some other way than by the discharge, we
could get luminescence of the gas without any current. For
the present such a separation can only be carried out ideally.
If
4. A number of phenomena, which otherwise can only be
explained with difficulty, are seen to follow almost as a matter
of course when we regard the cathode rays as a disturbance
which is quite independent of the actual discharge, and no
more connected with it than the light which radiates from
the discharge. I shall only mention the penetration of the
striæ, the reflection of cathode rays from the anode, and the
way in which these rays pass out through anodes consisting
of close metal gratings completely surrounding the cathode.
With respect to the latter, I may say that I have seen fully
developed cathode rays pass through wire-gauze containing not
less than thirty-six meshes to the square millimetre.
1 i.e. of rays which in their nature are identical with the cathode rays. The
name obviously becomes unsuitable if it has also to include the rays of the
positive striæ.