Magnetic Field on the Discharge through a Gas. 257 



last experiment that the sum of the effects on the positive 

 column more than counterbalances the effect near the cathode. 

 It is well known that a strong local magnetic field deflects 

 both positive column and negative glow ; with the field here 

 used the negative glow was little distorted but contracted 

 strongly towards the cathode. A slight shortening of the 

 Crookes dark space was also noticed. This could be best 

 shown by so arranging the pressure that a dark space of two 

 or three mm. was seen, and moving the electrodes so that one 

 explorer was in the negative glow and the other just in the dark 

 space. The electric force in the latter being considerable, 

 a lar^e deflexion was obtained on the electrometer, but when 

 the field was set up, the dark space shortened, both explorers 

 were seen to be in the negative glow, and the electrometer 

 deflexion was considerably lessened. 



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i 



1 



KATHODE 



ANODE 



At pressures over 1 mm. fields of such strength as not to 

 striate the positive column were found to have very little 

 effect on the distribution of electric force except near the 



