[ALLAN] EXCITED RADIOACTIVITY FROM ATMOSPHERIC AIR ois) 
charged for a fixed time and voltage. The experiments extended 
over a good many days and under various sorts of weather. Some of 
the results are shown in the following table: 
A copper wire charged for 30 mins. at a P. D. of —22,000 volts. 


RATE OF LEAK 



DATE hn) Sen eee CONDITION OF THE WEATHER. 
Jan. 17th 23°0 Clear and cold, moderate wind. 
‘* 20th 12°3 Clear and fairly cold, light wind. 
23rd 46°5 Clear and fairly cold, very high wind. 
“24th 36°5 Clear and cold, high wind. 
28h 28°0 Clear and very cold, high wind. 
29th 22°5 Clear and cold, moderate wind. 
‘* 30th 23°5 Clear and cold, light wind. 
‘ S3lst 5:3 Clear and cold, no wind. 
Feb. 4th 12°0 Clear and cold, light wind. 
‘ 6th 1765 Clear and moderately cold, light wind. 
a NTbE 15 Dull and fairly warm, no wind. 
‘* &th 115 Dull, snowing, and high wind. 

As can be seen by this table, the amount of radioactivity varied 
greatly on different days, on some being hardly observable, and on 
others enough could be collected in a few minutes to necessitate the 
use of a condenser in parallel to cut down the rate of leak. 
A clear, windy, dry day seemed to give the best results, whilst 
a dull, quiet day the least. Experiments made since, during the 
spring weather, seem to show that on no day could there be obtained 
as much as in winter. The amount that could be obtained from 
the air inside never seemed to change very much. Two wires were 
charged for the same time and at the same potential, one outside the 
building and the other inside. Whilst that outside varied from time 
to time, that inside kept fairly constant. 
VARIOUS EXPERIMENTS. 
Experiments were made on the effect of length of charge. It 
was found that the amount of radioactivity increased directly with 
time for the first two hours and then more slowly. The amount 
of radioactivity was found to vary directly as the length of exposed 
wire and to be not effected by the diameter of wire nor the material 
of the wire. 
