428 Prof. Richardson and Dr. Bazzoni : Experiments 



for a series of different filament temperatures by the curves 

 in fig. 2. These refer to discharges in mercury vapour at 

 pressures comparable with O'Ol mm. At a low filament 

 temperature (l'O amp. heating current) the current increases 



Fig. 2. 



3170 at 30V 



40 50 



«— Vails C-D 



more rapidly with the voltage than the first power at low 

 voltages. At higher voltages the rate of increase falls off 

 until finally saturation ensues (curve E, fig. 2). The current 

 only behaves in this way when the temperature of the filament 

 is low. Thtt behaviour at higher temperatures is indicated by 

 curves A, B, 0, and D in fig. 2. These curves are all very 

 much alike, and the behaviour below about 20 volts is veri- 

 similar to that of curve E. With higher voltaees it is,. 

 however, quite different from that shown by E. Thus with 



