﻿of Ions made by a, ft, y, and X Rays. 



293 



to earth. The distance of the metal electrode from the gauze 

 was 2'5 rams, 



A film of polonium was used as the source of ionization. 

 A bundle of tubes, each *5 cm. long, was placed on the disk 

 with the axes of the tubes vertical in order to obtain approxi- 

 mately parallel and vertical rays. 



The disk was placed on a large metal plate e, supported by 

 the table d, which could be raised or lowered by means of 

 the screw g, the distance of the polonium film from gauze 

 being indicated by a pointer on a scale. 



In one of the experiments another gauze li, insulated from 

 a and connected to earth, was placed at a distance of 3 rams. 

 from a, the object being to prevent a drift of ions into the 

 chamber. This arrangement was used to ascertain if the 

 variable field between e and a, in the absence of the gauze, 

 was strong enough to prevent a drift of ions into the chamber, 

 and did not otherwise affect the leak. 



This apparatus served also to determine the range of the 

 a particle from polonium in air at atmospheric pressure, and 

 the ionization along its course. 



Curves have been plotted from the observations showing 

 the relation between ionization and distance of polonium film 

 from gauze. 



