442 Mr. S. Iiatner on the Distribution of the Active 



an induction-coil provided with a rectifying valve, and varied 

 in different experiments from 15,000 to 50,000 volts, as 

 roughly measured by an alternative spark-gap. At such 

 high potentials the results could not be affected by the 

 sharpness of the needle, and it was only necessary to ensure 

 that the needles were of the same length and surface area. 



Fig. 



f 



The experiments consisted in comparing the activities acquired 

 by the needle in the absence of an electric field and when 

 raised to a potential of =F800 volts or a high potential of 

 either sign. , In order to establish the role of the discharge, 

 experiments under exactly the same conditions were also 

 made with small plates 1*5 cm. in diameter fixed in place of 

 the needle, in which case the high potential applied does not 

 produce a discharge. 



Table III. gives the results of one series of these expe- 

 riments. As was to be expected, the discharge accompanied 

 by the electric wind prevents the electrode from receiving 

 any appreciable amount of activity. Attention must be 

 drawn to the tact that in the case of a high negative potential 

 the activity acquired by the needle is larger than when it is 

 exposed to the emanation in the absence of an electric field. 

 This shows that, in spite of the exceedingly large quantity of 

 negative ions streaming from the needle, a small fraction 

 of the recoil atoms escape recombination and reach the needle- 



