Concentration Cells in Ionized Gases, 



687 



The wires to the electrometer were carefully insulated and 

 shielded throughout by earthed metal tubes. A key, E, of 

 mercury cups on sulphur blocks, also in a lead box, allowed 

 rapid calibration of the electrometer by a potentiometer 

 arrangement. When the tube was started A and B were 

 shielded alternately by a suitable extra thickness of Al (Gr, 

 fig. 1), and time readings of the electrometer deflexions were 

 taken. In all cases a deflexion was gradually set up, which 

 ultimately reached a steady value, and reversed its sign when 

 the shielding Al was changed from one electrode to the other. 

 The unshielded electrode was always found to be positive to 

 the shielded one. Fig. 2 shows specimen curves. 



Fig. 2. 



eo 



I 



-eo 



-30 





/- 



^^1 





s 



-V 5 





/"** 



1 



a 



/ 



1 







\ 





l 



\ 



L 



1 



' 



V. 



\d 



I 





I 





**6 



f* 



-.. . f< 







r 



7 

 c 

















1 





















\ 























a 











\ 



\ 























• 





j 



























































-— J<: 



i 







-»» .!<• 



I 







E 



II. 27 mm. 



1 div. =-0014. r )ovolt. 



5 10 15 



77 m £ //v M/f\fS. 

 Thickness of shielding Al I. '] mm. 

 Sensitiveness of Electrometer 

 ab, cd, cf, B shielded. 



bc,de,fg, A 



gh, neither ,, 



A source of possible error in the interpretation of these 

 results may be here referred to. When a metal is acted upon 

 by X rays, secondary cathode rays, carrying a negative 



