3G2 Prof. J. J. Thomson : Experiments on 



a negatively electrified wire acquires the property of ionizing 

 the air around it ; this effect is, however, shown to a very 

 much greater extent by the gas when it is in the modified 

 state produced by bubbling it through water. 



To show this the tank A was filled with the modified con- 

 ducting gas, while the air in B was kept in its normal 

 condition, a clean wire electrode was taken and the saturation- 

 current through B with this wire as electrode measured ; the 

 wire was then placed in A and kept negatively electrified by 

 a Wimshurst machine for periods ranging from 30 minutes 

 to 7 hours ; the w T ire was then taken out of A and replaced 

 in B, and the current through B again measured with this 

 wire as electrode : the current was found to be considerably 

 greater than before the electrification of the wire. The 

 following numbers show the magnitude of this effect : — 



Current through B with a potential- 

 difference of 1000 volts before wire 



was electrified wire +24, wire — 17 



Current after wire had been negatively 



electrified in the vessel A for 7 hours wire 4- 54, wire — 51 

 The conductivity of the air in the tank A was about 10 times 

 normal. 



In another experiment when the conductivity in A was 

 about 12 times normal, the results w r ere : — 

 Current through B before wire was 



electrified wire + 22, wire — 17 



After 7 hours' negative electrification of 



the wire in A the current through B 



was v r ire + 74, wire — 67 



Larger effects were obtained with electrodes having larger 

 surfaces than that of the straight wire. Thus, when a 

 cvlinder of copper wire-gauze was used as the electrode, the 

 current through B before the gauze was electrified was : 

 gauze +22,-21. After 7 hours' electrification in A the 

 current through B was : gauze +400, —200. 



The amount of ionization produced by a wire after negative 

 electrification does not seem to depend to any great extent 

 on the material of which the wire is made. Wires of the 

 same diameter and length made of zinc, lead, iron, copper, 

 amalgamated copper, copper covered with a layer of water 

 and glycerine, copper wet with alcohol, which all gave when 

 used as electrodes equal currents through B before electrifi- 

 cation, gave approximately equal currents (much larger than 

 the previous ones) after negative electrification in A. To 

 ensure that the wires were exposed to similar influences in 



