258 



Dr. R. S. Willows on the Effect of a 



cathode. This is shown in the accompanying figure 6, in 

 which the ordinates are electric force. It is seen that the 

 sudden decrease in the electric force that occurs just in front 

 of the cathode, found by Graham * and Wilson f, is much 

 less marked, although still considerable. The pressure and 

 current were such that there was luminosity only on the 

 surfaces of the electrodes. 



In this, as in the other figure given after, the current 

 through the tube is less when the magnet is on than when it 

 is off', the resistance in the circuit was not altered so as to 

 bring them to the same value in the two cases. 



It is known that a continuous discharge if subjected to a 

 transverse magnetic field may become stratified. Obser- 

 vations on such a discharge showed that these artificially 

 produced striae present the same remarkable periodic vari- 

 ations in the electric force as those existing normally in the 

 tube. This is shown in fig. 7. 



Fig. 



7. 























. 















71 



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v -^ \-t * 



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/l^AG. CF,-. 





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: ± 



KA THODE 



ANODE 





It will be noticed that at this pressure, the effect of the 

 magnet is to decrease the electric force near the cathode, in 



* Wied. Annal. lxiv. p. 69 (1898). 

 f Phil. Mag., June 1900. 



