Since then, Richardson and J.J. Thomson have examined
analogous phenomena. This emission is a very general phenomenon which,
no doubt, plays a considerable part in cosmic physics. Professor
Arrhenius explains, for instance, the polar auroras by the action of
similar corpuscules emitted by the sun.
In other phenomena we seem indeed to be confronted by an emission, not
of negative electrons, but of positive ions. Thus, when a wire is
heated, not _in vacuo_, but in a gas, this wire begins to electrify
neighbouring bodies positively. J.J. Thomson has measured the mass of
these positive ions and finds it considerable, i.e. about 150 times
that of an atom of hydrogen. Some are even larger, and constitute
almost a real grain of dust. We here doubtless meet with the phenomena
of disaggregation undergone by metals at a red heat.
CHAPTER IX
CATHODE RAYS AND RADIOACTIVE BODIES
Sec. 1. THE CATHODE RAYS
A wire traversed by an electric current is, as has just been
explained, the seat of a movement of electrons. If we cut this wire, a
flood of electrons, like a current of water which, at the point where
a pipe bursts, flows out in abundance, will appear to spring out
between the two ends of the break.
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