102 ROYAL SOCIETY OF CANADA 
From the numbers given in column IV. of this table it will be 
seen that the conductivity of the air arising from spontaneous ioniza- 
tion is not constant, but varies considerably from day to day. An 
extended series of measurements which were made during the past 
winter upon the spontaneous ionization of atmospheric air confirmed 
these earlier results, and the numbers given above represent fairly 
the extent of the variations found in the conductivity of atmospheric 
air under normal conditions. 
It was also found that there was considerable variation in the 
amount of radioactivity acquired by the exposed conductors when 
the conditions of exposure apart from the state of the air remained 
unchanged. Daily variations occurred in the amount of radioactivity 
excited, and it often happened that exposures made at different times 
in the same day gave quite irregular results. Examples of this type 
of irregularity are shown in the numbers recorded for Oct. 30th and 
31st. With the wind blowing toward the window where the discs were 
exposed, excited radioactivity was especially strong. 
(IV.) Raproactiviry Excirep IN POSITIVELY CHARGED CONDUCTORS. 
Concurrently with the experiments described above, a series of 
exposures was made before the open window with zinc discs positively 
electrified. The discs were charged, as in the previous experiments, 
with the Toepler Holtz machine, but in this case the negative terminal 
of the machine was joined to earth, while the positive was connected 
to the exposed plate. The polarity of the machine was examined 
from time to time in each experiment, and in none of the tests was 
there any indication of a reversal of polarity during the exposure. 
The results of the experiments are given in Table III. 






TABLE III. 
PRE A Con I PREY Oe A] Loss of charge of | Loss of charge of 
Time of Potential of | gold leaf in volts | gold leaf in volts 
Date En ny rs discs in volts. per hour with per hour with 
in hours. unexposed plate. | exposed plate. 
Oct. 30, 1901 1'0 12000 positive 1'9 3:7 
RT LTC 1:0 cic SE 1'9 2°6 
Nov. 4, 1901 40 oe i 3°0 3°0 
cae 10°0 ‘ 5; 2-2 76 
NN 4°0 ve ae 2°2 Al 
« 6, «e 10:0 “cc “ec 3°29 5:2 
‘cc Tk “cc 7:0 “cc ““ 2°9 5-1 
“se 14, [22 145 ce “ 3:3 | 3°3 
Jan. 15, 1902 17:0 28000 ‘i 3°3 35, 


