70 



Discharge of Electricity through a Vacuum- Tube. 



coils was altered. A typical set of observations is given 

 below : — 



Pressure. 



Magnetizing 

 current. 



0-11 mm. 



63 amp. 



Oil „ 



o-3 „ 



o-ii „ 



4-5 „ 



on „ 



4-05 „ . 



on „ 



2-8 „ 



Change in Voltmeter Reading 

 by putting Magnet ' on.' 



caused 



From 225 to 350 = 125 volts 



Rise. 



„ 225 „ 300= 75 „ 



„ 



„ 225 „ 280 =55 „ 



„ 



„ 225 „ 275 = 50 „ 



„ 



, ; 230 250= 20 „ 



" i 



The relation between the rise in the voltmeter-reading and 

 the magnetizing current is shown graphically in fig. 1. 



Fio; 1. 



J 20 



§90 



560 



30 



1 



j 



1 



1 







/ 



/ 



/ 





1 





/ 







b / 







i 









MflcHETis/NG Current //v Amperes 



The connexion between the magnitude of the effect and the 

 pressure of the gas was not investigated. 



I desire to thank Dr. Willows for suggesting this experi- 

 ment, and for assistance during its performance. 



The Sir John Cass Technical Institute, 

 Jewry Street. E.C. 



