Emanation and Active Deposit produced by it. 379 



to see that the condensation was carried on for periods 

 sufficiently lono- to eliminate differences in the rate of dif- 

 fusion of the emanation from the first chamber to the second. 

 Measurements made on the amount of emanation obtained 

 in the second chamber would then give information directly 

 about q, the rate at which the emanation from radium left 

 the salt at different pressures. 



To obtain information about the factor a it would suffice 

 to make repeated exposures of a negatively charged electrode 

 of small surface to equal quantities of radium emanation, at 

 a number of different pressures. The experimental arrange- 

 ments outlined in the preceding paragraph would probably 

 suffice to enable one to repeatedly obtain in the second 

 chamber a definite amount of emanation. These repeated 

 condensations could be made at a very low air-pressure and 

 then, if the second or condensation chamber were cut off 

 from the first and air afterwards admitted into it to any 

 selected pressure, it could be used as the exposure chamber 

 as well. This would enable one to find how the number of 

 positively charged active deposit particles from a given amount 

 of radium emanation varied with the pressure of the air in 

 which the emanation w r as diffusing. 



If a. and q were found separately in this way with Ihe 

 emanation from radium, one could see whether or not their 

 product varied in accordance with such a law as that repre* 

 sented by (5), and from the resulting agreement or lack of 

 it one could come to some definite conclusion regarding the 

 validity of the explanation offered in the present communi- 

 cation of the results obtained by Kennedy. 



If the law enunciated in (5) were confirmed by the ex- 

 periments just described the result would go to show that 

 active deposit particles at the instant of their creation are 

 uncharged, and that the positive charge usually found on 

 them when diffusing in gases at ordinary pressures is 

 acquired from the surrounding ionized gas at a stage later 

 than that of their creation. 



The experiments begun by Kennedy are being conducted 

 in the direction indicated above, and it is expected that 

 results will be obtained shortly which may enable one to 

 settle definitely the origin of the charges acquired by the 

 active deposit particles. 



Physical Laboratory, 

 University of Toronto, 

 May 1/1912. 



