236 W/tedock — Nature of Ionization Produced hy a Rays. 



carried over to the plate A. The polonium, or other radio- 

 active sul)stance used, was placed on a carrier, R, which could 

 be moved up and down by means of the screw Ct, the position 

 of whicli was o;iven by the scale S. 



The apparatus used for testing the effect of a field perpen- 

 dicular to the path of the a particle (fig. 2) consisted of a brass 



Fig. 1. 



Fig. 2. 



plate, C (8-5™ by 2-5'='"), connected by B to a battery, a narrow 

 brass strip, E (7-2™ by 0-4:^"), connected to one pair of quad- 

 rants of the electrometer, and a brass plate, D, surroundmg E 

 and separated from it by an air space of 0-5"'"'. The plate D 

 was grounded tlirough the top of the containing vessel and 

 served as a guard ring. 



