136 MR. C. E. S. PHILLIPS ON THE ACTION OF MAGNETISED ELECTRODES 
The conditions most favourable to the formation of a luminous ring have been found 
to be — 
[a.) A sufficiently powerful electrical stimulation of the residual gas within the 
bulb to ensure ionisation. 
(6.) A magnetic field of at least 2000 lines j)er square centimetre between the 
oppositely magnetised pointed pole pieces (which may be electrically in¬ 
sulated). 
(c.) Exhaustion should be continued until the discharge while passing in the bulb 
is oscillatory. 
The brightness of the light emitted by the ring may be momentarily increased by— 
(o.) Connecting the outside of the bulb (preferably at its equator) to either of the 
magnetic electrodes, or by merely touching it with a finger. 
(/>.) Electi'ifying the exterior surface of the bulb positively. 
(c.) Electrifying the magnetic electrodes negatively. 
(c/.) Having oxygen gas in the l)ulb instead of air. 
(c.) Suddenly destroying the magnetic field while the ring is faintly visible. 
A ling which had once formed could be instantaneously extinguished by— 
[a.) Electrifying the exterior of the bulb negatively. 
(6.) Electrifying the electrodes positively. 
(c.) Magnetising the electrodes so that like poles faced each other. 
[cl.) Destroying the magnetic field. In no instance did the ring remain visible 
after the current was cut oft’ from the electro-magnets. 
Satisfactory results liave also been obtained when only one magnetic electrode was 
used, the arrangement being indicated in fig. 2. 
In such cases it was generally found convenient to fiicilitate the oscillatory nature 
of the discharge within the bulb by gumming a piece of tinfoil. T, on to the outside. 
