94 Mr. Richardson on the Positive Ionization produced 



After waiting 40 minutes the wire was heated with 'So ampere, 

 and charged to + 200 volts as before. The induced activity 

 was now found to be somewhat over 500 divisions in 

 40 seconds, and was therefore, within experimental errors, 

 equal to that found when the wire was tested immediately. 

 The activity induced by the discharge therefore falls off' very 

 slowly, if at all, by simply keeping the wire cold. 



In all the preceding experiments, the wire w^hich had been 

 made active was the negative electrode. Experiments were 

 now made to see if any activity was induced in this wire 

 when the discharge was passed in the opposite direction, and 

 if so what the relative magnitude of the induced activity 

 was in the tvro cases. 



The results show that the activity induced on the positive 

 electrode is only about one-fifth of that induced on the 

 negative, but that nevertheless it is quite marked and 

 definite. 



Electrode on which 

 Activity Induced. 



Induced Activitj^ 



+ 

 _ 



+ 



176 



1200 



260 



It is to be noted that the ratio of the effects in the two 

 directions is practically equal to that found for the corre- 

 sponding effects produced by the discharge from hot wires 

 and given on pp. 87 and ^^. It seems probable therefore 

 that the two phenomena are intimately connected. 



The fact that activity could be induced both by the positive 

 leak from hot metals and by the ordinary discharge led to 

 the view that it was due to positive ions which stuck to the 

 electrode and formed a double layer. In this case the same 

 effect ought to be produced whenever positive ions discharged 

 to the surface of the metal. 



With the view of testing this supposition careful experi- 

 ments were made to see if collecting positive X-ray ions on 

 a wire increased the leak from it at a given temperature at 

 atmospheric pressure ; but no effect was obtained. A similar 

 result was got at a low pressure. It w-as thought that these 

 negative results might be due to the X-rays themsehes 

 possibly having the power to destroy the induced activity. 

 This was the more probable, since X-rays are well-known to 

 have a very intense action on metallic surfaces, resulting in 



