Perkins — Rectification Effect in a Vacuum Tube. 485 



Art. L. — A Rectification Effect in a Vacuum Tube; by 

 Henry A. Perkins. 



The effect to be described in this article was accidentally 

 discovered by the writer during some experiments on the 

 electrodeless discharge. It was noticed, in the first place, 

 that a tube exhausted to about £ mm pressure showed ioniza- 

 tion when acted on by an alternating electrostatic field of low 

 frequency and comparatively low potential, 550 volts and 

 above. Moreover a direct current was sent through a galva- 

 nometer connected to two terminals sealed into the ends of 

 the tube. 



The alternating field was supplied from one end of a trans- 

 former capable of giving 2000 volts, and the other end was 



grounded. The free end was connected to a ring surround- 

 ing, but not touching, the tube, and was adjustable to various 

 positions along the tube. The tube itself was about 20 cm 

 long between the inside ends of the electrodes, and about 

 2 cm outside diameter. It was exhausted from a point near one 

 end, thus leaving the main body of the tube a smooth cylin- 

 der, and in order to secure as much symmetry as possible, a 

 dummy tube was blown in the other end as shown in the dia- 

 gram. The galvanometer used was a Thompson type of 

 instrument having a resistance of 5800 ohms, and, as adjusted, 

 l cm deflection on the scale was equivalent to 5xl0~ 8 amperes'. 

 The connections are shown in fig. 1. 



As soon as the main transformer circuit was closed, the 

 ionization became evident by a faint glow in the tube, and on 

 closing S, by a deflection of the galvanometer. This deflec- 



