202 Mr. S. Batner on Polarization 



conditions the electric field betwen. the electrodes was more 

 than a hundred times as great as that required by positive 

 ions producing ionization by collision, and the free path of 

 the ions was small compared with the dimensions o£ the bulb, 

 so that independently of any electronic emission from the 

 cathode a sufficiently large current would be expected to 

 flow across the bulb. In fact, however, when polarization 

 was reached, the current through the bulb was as small as 

 10 ~ 8 amp., and; as mentioned above, was carried entirely by 

 the glass, since it did not appreciably diminish when the 

 bulb was thoroughly exhausted afterwards. These results 

 are very striking if we bear in mind that at the same 

 pressure under ordinary conditions a p.d. of less than a 

 thousand volts is sufficient to produce a large current 

 which, according to present theories, is carried entirely by 

 ions produced by collision. 



Discussion of Results . 



7. The experiments described in § 4 are sufficient evi- 

 dence that polarization phenomena originate solely with the 

 electrodes. JSTow, internal changes in the electrodes could 

 hardly be caused by the discharge, and it seems more likely 

 that the phenomenon is due to the destruction by elec- 

 tronic action of the gaseous layers in the surface of ,the 

 electrodes. These layers, whose existence is now well 

 established, play an important part in various phenomena. 

 It has long been well known- that gases occluded in the 

 electrodes greatly facilitate the passage of a discharge 

 through a vacuum tube, and it has been found recently that 

 metal surfaces carefully freed from gases do not exhibit any 

 appreciable photoelectric effect *. It seems therefore, as if 

 the process of electronic emission from cold metal surfaces 

 could lake place only through the intermediary of the surface- 

 layer of gaseous molecules. 



This theory may serve as a guide in interpreting the 

 phenomena described above. During the discharge the 

 gaseous layer on the surface of the cathode undergoes a 

 continuous disintegration, which, after a long run, begins 

 to affect the electronic emission from the cathode and 

 finally causes the discharge to stop altogether. After the 

 discharge is interrupted, a new layer of molecules on the 

 surface of the cathode is gradually built up, which brings 

 the polarized bulb back to its normal condition. The 

 larger the pressure in the bulb the quicker this new layer 



* Hallwachs, Phys. Zeits. Nov. 1920. 



