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Mr. V. E. Pound on the Secondary Rays 



it has been found by Duane * that the a rays lose their power 

 to produce secondary rays at the same time that they lose 

 their charge and their power to ionize a gas. 



The present paper describes some experiments on these 

 secondary rays produced by the a. rays of polonium. The 

 apparatus employed at first was somewhat similar to that 

 used by Logeman when he established the existence of this 

 secondary radiation from metals bombarded by a rays. In 

 the experiments to be described exhaustions were made with 

 a Gaede pump, and the pressures were measured with a 

 McLeod gauge. 



2. Description of Apparatus. 



The apparatus used in the initial experiments is shown in 

 1. It consisted of a brass cylinder about 4 



fig 



cm. in 



Fijr. 1. 



to bettery 



to pump 



earth 



to electrometer 



diameter and 9 cm. in length, which had an ebonite plug 

 fitting into each end. Through one of these plugs was led 

 a brass rod which carried a round brass electrode B, about 

 15 mm. in diameter. The electrode B was surrounded by a 

 circular guard-ring 0. 



Through the other plug was led another brass rod, and it 



* Duane, Comptes Rendus, May 



