Gases under the Becqiterel Bays. 



127 



The kinds of radiation employed are there enumerated. They 

 include, 



(1.) The most penetrating kind of radiation, from radium — that 

 deflectable by the magnet. 



(2.) The easily absorbed kind of radiation from radium, which is 

 not so deflectable. 



(3.) and (4.) The radiation from two different samples of polonium. 



(5.) The radiation from uranium salt. 



The method of measurement is then described. It was in outline 

 as follows : — 



The layer of the radio-active body was placed at the bottom of a 

 shallow brass box containing the gas under investigation. In this box 

 and parallel to its flat top was a disc electrode, carried by a brass rod 

 passing, air-tight, through an insulating ebonite stopper. The outside 

 of the box was maintained at a high potential by a battery of small 

 storage cells, and the current through the gas measured by the rate at 

 which the potential of the insulated electrode rose, as indicated by a 

 quadrant electrometer connected with it. 



When it was desired to use only the penetrating rays from radium, a 

 thin copper sheet, - 007 cm. thick, intervened between the radio-active 

 material and the gas. In measuring the relative conductivities of 

 two gases, the rate of leak through one was observed at a known 

 pressure. The apparatus was then exhausted, and the other gas 

 admitted, and the rate of leak through it determined. This last rate 

 of leak was corrected, so as to obtain the value which it would have 

 had at the same pressure as that at which the first was examined. 

 The rates of leak through the two gases were then comparable. 



The mean results were as follows : — 



Oas or vapour. 



Density 

 (relative). 





Relative 



conductivity 





Radium. 



Polonium. 



Uranium. 



Pene- 

 trating. 



Easily 

 absorbed. 



I. 



II. 



1 



-0693 



0-157 



0-218 



0-226 



0-219 



0-213 





1-00 



1-00 



1-00 



1-00 



1-00 



1-00 



; Oxygen . . 



1 -11 



1-21 





1-16 









1-53 



1-57 





1-54 







I Cyanogen 



1-86 



1-86 





1-94 









2.19 



2 32 



1-92 



2-04 



2-03 



2-08 





4-32 



4-89 





4 -44 







j Methyl iodide 



5 -05 



5-18 



3 74 



3 51 



3 47 



3-55 



1 Carbon tetrachloride. . 



5 31 



5 83 





5-34 



1 





