Gases by the Motion of Negatively charged Ions. 205 



practically, of the electromotive force ; and that the negative 

 ions produce others by collisions with the molecules of the 

 gas when the electric force is increased, the new negative 

 ions thus produced having the same property as the negative 

 ions produced initially by the rays. 



Fiff. 5. — Pressure -332 mm. 



280 



260 



240 

 220 











































































200 





















18n 





















160 





















140 





(> 

















120 





















ion 





















80 





f 





i 













60 









y 













40 



( 



/ 



ft 















20 



/ 















— '£ 

























160 



240 320 400 



Volts per centimetre. 



560 



720 



If both positive and negative ions produced others by 

 collisions with the molecules, it is evident that the current 



