932 Mr. D. C. II. Florence on 



tbe quantity of radiation produced by different radiators the 

 apparatus was sot up afresh. A new electroscope was made 

 of similar dimensions to the original one, but the thickness 

 of the sides was 6 mm. A lead screen was also made for 

 the small glass windows and a lead cap for the ebonite 

 support of the leaf system. The electroscope was supported 

 on an iron pipe so that it could be turned round an arc of a 

 circle The radium (20 mgrs.) was surrounded by 2*08 mm. 

 of lead. The radiators were supported by string from a 

 beam overhead, so that secondary radiation from surrounding 

 bodies was reduced to a minimum. The arrangement is the 

 same as shown in fig. 1. 



The direel radiation was firsi measured through the various 

 radiators. The results were [dotted with the ionizations in 

 Ihe electrosco] as ordinates and the weight per unit area 

 as abscissae. These curves (fig, 2) have already been 

 referred to. 



To examine the secondary radiation two definite positions 

 were taken and the results plotted in figs. 5 and 6. 



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5 



51 





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Th/ckhess x D£/vs/rr 

 Electroscope turned through angle 25°. Comparison of amount of 

 secondary radiation for different thicknesses of different materials. 



