590 Research Staff of the G. E. C, London, on the 



The lamp contained the straight tungsten filament F, 

 capable of carrying in a vacuum a current of 14 amp. with 

 a voltage of 10 volts. The heating current was derived from 

 the battery B, regulated as usual by a rheostat and ammeter 



Fio-. 1. 



and voltmeter. The supports of the filament were of nickel 

 wire 0*6 mm. in diameter. A similar piece of wire served 

 as the anode. Any desired potential difference between 

 the filament and the anode could be established by means of 

 the 600-volt dynamo D acting through a potential divider R 

 with a fine adjustment. The potential between the anode 

 and the negative end of the filament (V) was measured by 

 the voltmeter V reading to O'l volt; the current (?) flowing 

 between the electrodes by the shunted microammeter A. 



Physical Characteristics of the Discharge. 



The Glow Potential. 



5. If the vessel is very highly evacuated, then, as is well- 

 known, i is independent within wide limits of the temperature 

 and thermionic emission of the filament, and, so long as V is 

 below a certain limit, varies simply as V^ : the current is 

 limited by the space-charge. If V is increased sufficiently, 



