produced from a Gas by High-Speed Cathode Rays. 211 



difference between Y± and Y 2 stopped all the positive ions, and 

 the second potential difference between Y a and Y 3 measured 

 the number of the secondary cathode rays, this field being 

 the main one. The third potential difference between V 3 

 and E served to prevent the reflexion of the corpuscles from 

 the electrode E. This potential difference was already shown 

 to be necessary by the experiments of v. Baeyer * and after- 

 wards of Oompton f and others. 



Before describing the results with this arrangement, it 

 might be interesting to give some results obtained by an- 

 other arrangement, in which Y 1 = 0, V 3 =-fl0 volts, and 

 Y 2 was varied from to —500 volts. The results are shown 

 in curve I., fig. 4. The curve cuts the V 2 -axis at about 



Fiar. 4. 



— 120 volts, and then ths positive current increases gradually 

 with Y 2 . With this arrangement, positive ions were not 

 stopped in the region Y x Y 2 , but in the region Y 2 Y 3 . They 

 were therefore accelerated in the first region, and acquired 

 velocities large enough to ionize the residual gas. The 

 positive currents for large values of Y 2 are partly due to 

 this ionization. Moreover, the positive potential of Y 3 with 



* Y. Baeyer, he. cit. 



P2 



f Compton, he. cit. 



