A peculiar form of low potential discharge in the highest vacua

Abstract

Mr. C. E. S. Phillips has described a curious electrical effect. Iron electordes E 1 , E 2 , fig. 1, were fixed in a glass bulb as shown. The bulb was exhausted very highly; a discharge was passed for a moment, and turned off. The iron electrodes were then magnetised by exciting the electromagnets M 1 , M 2 . On magnetisation, a luminous ring was observed in the equatorial plane of the magnet, which lasted for a few seconds, and then died out. The effect excited considerable interest at the time, and careful experiments were made by the discoverer to elucidate its causes. The following may be quoted from the concluding section of the paper as representing his views. “The preceding experiments show that the principal effect of the magnets is to produce a concentration of negative ions at the strongest portion of the magnetic field, and centrally within the bulb • • • • I consider that this concentration of negative ions is due to two main causes. In the first place it is partly produced by the action of the magnetic field on ions already in motion within the bulb • • • • • And secondly owing to the reaction resulting from the sudden excitation of the magnets, the comparatively dense cloud of ions situated at the ends of the bulb would, in rapidly turning about the magnetic axis, tend to move towards the pointed end of the electrodes, and so concentrate as observed.”