[STEWART] ON EXCITED RADIOACTIVITY 101 
TABLE I. 


ate of loss of charge 
| of gold leaf, when 
Discs. | Time of Exposure. Potential of Disc. disc was inserted 
| 
in electroscope. 


No. 1 First hour 11,000 volts negative 54 
pen Second ‘“ ie 4 KE | 45 
os Third “ eek us = | 39 
tra Fourth ‘ SUR x | 33 
HA Fifth +3 + se $s | 27 

It was also found that after a series of experiments had been 
made in the room and the air had lost to a considerable extent its 
power of imparting radioactivity, the opening of a window and the 
consequent admission of fresh air was always accompanied by an 
immediate increase in the amount of radioactivity excited in the 
exposed body. 
Some measurements were also made on the radioactivity excited 
in discs exposed, when negatively charged, before an open window 
in the laboratory, and a few of the results obtained are recorded in 
Table II. Column I. of this table gives the day upon which the 
exposure was made; column II. the time of exposure in hours; column 
III. the potential in volts of the zinc plate during exposure; column 
IV. the observed rate of leak in the electroscope with the unexposed 
zinc plate inserted, and column V. the rate of leak when the zinc 
plate was replaced in the electroscope after exposure. 
TABLE II. For NEGATIVE EXPOSURES. 






: ‘ Loss of charge in | Loss of charge in 
Date | exposure | exposed plate |,,"glts per hour, | volts per hour 
5 j ionization alone. exposed plate. 
Oct. 30, 1901 1 12000 negative 1:9 19°2 
Le 1 at oH F9 sy 
COUPE | PRE 4 Bs LRT) 10°8 
“ig a : à = 167 177 
Nov. 6,2” 7 ES + 3°2 36°0 
CEST ir 10°5 © 2°9 36°0 
tha a RE 14°5 $ “s 2°8 34°5 
Jan. 10, 1902 18°0 28000 oh 2-4 26°7 
eer 57 ii 21°5 25000 HY 2°5 14°4 

