UPON ELECTRICAL DISCHARGE PHENOMENA IN RAREFIED GASES. 
147 
the new position of the cylinder had not disturbed the action of the magnetic field 
upon the electrified gas within the tube consisted in charging the cylinder itself 
positively and then suddenly magnetising the electrodes. When that Avas done tlie 
cylinder completely lost its charge in a very satisfactoiy manner. 
Varying Magnetic Fields. 
It has long been thought that an electrified body would tend to move, through the 
action upon it of a rapidly varying magnetic field. The ])ath of the body should lie 
along a direction at right angles to that in Avhich the magnetic lines are moving, and 
also at light angles to the direction in which they spread. The conditions accom¬ 
panying the ap])earance of the luminous rings, and also the diselectrification already 
described, apjieared suitablo for the detection of the action which a variation in 
strength of the magnetic field might be expected to have upon the practically 
weightless and very minute electrified gaseous particles freely floating about within 
the bulb. 
It has already been pointed out that a luminous ring having become dim and 
almost invisible could be momentarily brightened by suddenly destroying the 
magnetic field. But with the apparatus shown in fig. 6 tlie following striking results 
were obtained :—The aluminium band A Avas positively electrified to a |)otential of 
6000 volts. When the current supplied to the electro-magnets Avas very slowly 
increased, as much as 11 amperes Avas necessary to produce diselectrification of A, 
Avdiile on the other hand, if the current Avere very rapidly increased in value A lost 
its charge Avheu oidy 6 amperes tloAved through the coils. 
Further than this, it AA'as alAAmys noticed that diselectrification occurred Avhen the 
magnetic field Avas suddenly destroyed rather than Avhen it Avas created. A partimdar 
rarefaction Avas found for each bulb, sucli that the band A could be electrified, and, 
irrespective of the fact that the electrodes Avere magnetised, retain its charge. In all 
such cases the ejfect of I'ayidly destroying the magnetic field tvas to produce diselectri¬ 
fication, luhei'eas tvhen the current supplied to the magnet coils was broken under water, 
and in consecjuence the magnetic field eausedy to gradtiedly diminish in strength, no trace 
of diselectrification iias observed. It Avas therefore clear that variations in the 
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