THE ELECTRON THEORY. 



293 



represent the lines of force of a magnetic field between the two 

 large magnet poles. 



A photographic plate ~B 



electrically 

 charged 

 plate 4 



(positive) J 



^electrically 



charged 

 ^ plate 



/////////////////////\ 

 had block 



S/////////////////M 



lead block 



'//////////////////J 



material 



Fig. 213. 



The determination of the velocity of the a- and jS-particles 

 is somewhat analogous to the following method of determining 

 the velocity of a cannon ball. The curved line in Fig. 215 repre- 



A photographic plate & 



lead block x' 



S///// //// X // X 



/, lead block 



material 



Fig. 214. 



a- particles deflected towards the reader and 9-particles deflected away from the 



reader. 



