Radium , r l It 



onum. an 



d Actinium, in Electric Fields. 359 



The central portions, C and D, o£ the disks were removable, 

 and could be made air-tight by running soft wax into 

 channels formed by brass rings on either side of the 

 junction-line. The diameter of the portion of the disks 



Fig-. 1. 



Fijr. 2. 



B 



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exposed on the inside of the vessel was 10' 6 cm., and that 

 of the removable disks 5*6 cm. The plates were 2 cm. 

 apart, and their internal surfaces were cleaned with fine 

 emery paper. Radium emanation was introduced mixed 

 with the gas under observation, or was allowed to accumulate 

 over-night from a small quantity of radium placed inside 

 the vessel. A Wimshurst machine was used for high 

 potentials. The gases were dried and filtered. At the 

 end oE an exposure, which was always longer than three 

 hours, the alpha-ray activities of the central disks were 

 compared by means of a Dolezalek electrometer. Wellish * 



* Log. cit. 

 2 B 2 



