produced from a Gas by High-Speed Cathode Rays. 209 



volts, V 2 = — 10 — v volts, where u is varied as before, a repe- 

 tition of the experiments yielded similar results. 



To see what potential difference is required to stop the 

 positive ions, the following experiments were carried out 

 with three gauzes. Keeping the potentials of V : and V 3 at 

 some constant values, the potential of V 2 was varied from 

 to + 30 volts, the idea being to stop the positive ions with 

 the potential difference between V T and V 2 . The results for 

 three cases, viz. (V 1 = 0, V 3 = 0), ( V! = 0, V 3 =-] volts) , 

 and (V 1 = 0, V 3 = — 30 volts), are given in fig. 3. 



Fiff. 3. 



1 



i 



! 







< ^—-^^" - 1 







1 i 



i 1 i 













1 









•H"" — r ~^~*' 



T i 1 



1 ! 1 





ifc— 



i 







i 











r 









O I 2 



5 10 



V? m Positive Volt 



20 



30 



40 





The curves show that nearly all the positive ions are stopped 

 by a potential difference of 1 volt. The current, however, 

 increases very slowly till V 2 = +8 volts, and then in the case 

 of curves II. and III. becomes constant, while it continues to 

 increase in curve I. 



Hence in order to stop the positive ions completely, we 

 should use a potential difference greater than 8 volts against 

 them. 



§5. Experiments on the Action of the Metallic Gauzes. 



Some of the secondary cathode corpuscles will hit the 

 wires of the gauzes. The effect of the hits is to diminish 

 the number of the secondary cathode rays which would 

 otherwise arrive at the electrode. The hits would probably 

 also cause the emission of tertiary cathode rays, and perhaps 



Phil. Mag. S. 6. Vol. 32. No. 188. Aug. 1916. P 



