ANODE RAYS.

The positively charged particles, which we have hitherto
considered, originate in the neighbourhood of the cathode.
Gehrcke and Reichenheiml have discovered rays of positively
charged particles which start from the anode. Their attention
was called to these rays by noticing that a pencil of yellow
light streamed from a point on the anode of a tube \vith which
they were working. It was found that there had been a speck
of sodium chloride at the points on the anode from which the
pencil started. They got these rays developed to a much
greater extent when they used for the anode a piece of platinum
foil with a little pocket in which various salts could be placed.
The foil was in circuit with a battery insulated from the one
used to send the current through the discharge tube; this
battery was for the purpose of raising the anode to a red heat,
as these rays are not developed unless this electrode is at a
high temperature. The current through the tube was pro-
duced by a battery giving a potential difference of about 300
volts which, as a Wehnelt cathode was used, was sufficient to send
a very considerable current through the tube: the pressure in the
tube was very low. The rays were well developed in this tube
when NaCl, LiCl, KCL and the chlorides of Cu, Sr, Ba, In, were
placed in the pocket. The colour of the rays corresponded with
the colour given to flames by the salt They did not get any
effects when the oxides of calcium or barium were put in the
pocket; these oxides are known when hot to give out large

lc* Verk D. Phys. Gesell," 8, p. 559; 9, pp. 76, 200, 376; 10, p. 217.

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