emitted In/ an Electrical Discharge at Low Pressures. 417 



Somewhere between fio's. 4 and 5 the minimu 



m sparking 



potential for the particular tube occurs, the minimum potential 



Fis-. 4. 



Fier. 5 



120 



JSO 



• 52 mm/. 

 569 



being roughly estimated at 560 volts, and after passing this 

 point a very decided difference is apparent. In fig. 5 not 

 only have the two maxima become about equal but the light 

 from the centre of the tube has also become large, while with 



