XII A PHENOMENON ACCOMPANYING THE ELECTRIC DISCHARGE 223
opposite the cathode, and forms a vortex (Fig. 27, c), and this
vortex maintains itself for some time in the air between the
electrodes (Fig. 27, d) after the rest of the appearance has died
away, but the whole only lasts about second.
I have not found any mention of the above phenomena in
the literature of the subject. Dr. Goldstein has often noticed
analogous appearances in his numerous experiments on the
discharge in rarefied gases, and he was also the first to bring
to my notice the favourable effect which a careful drying of
the air has on the brightness of the yellow light.