Potential at the Electrodes in Vacuum-tube Discharge, 499 1 



if not, as is probably the case in the negative glow, the 

 presence there o£ the walls o£ the tube will cause with the 



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same current a smaller degree of ionization, and hence through 

 the thereby increased velocity of the discharging ions a 

 greater cathode drop than either when the walls are brought 

 into the cathode dark space or lie beyond the negative glow. 



Effect of Tinfoil-coating on Tube surrounding the Cathode. 

 The cathode drop in the foregoing experiments was found 

 under certain conditions to be very greatly increased when a 

 sheet of tinfoil was wrapped around the tube opposite the 

 discharging-surface of the cathode. The effect is inappre- 

 ciable until the negative glow expands to, and is confined by 



