rfion of E Activity of JRadiun . 601 
dnction. I have some plates made a year ago which show 
the bands most beautifully, but I have not yet enlarged them, 
and they are on too small a scale to reproduce well. 
The present paper must not be regarded as a complete 
presentation of the subject. and I am publishing these results 
now in order that they may serve as a guide to those who 
are at work at the theory of the radiation of electron systems. 
from the theoretical side. 
LVI. The Distribution in Electric Fields or the Active 
- of Radium, Thorium, and Actinium. By 
Sidney Ru-s. Demonstrator of Physics, Victoria Uni- 
Ma u estt *. 
Introduction, 
THE distribution in an electric field of the excited activity 
produced by thorium and radium emanations has been 
studied by several observers. TTorking with thorium ema- 
nation. Rutherford t has shown that the amount of activity 
imparted to a rod charged negatively decreases as the pressure 
in the containing vessel is reduced after a certain pressure is 
reached : while experiments made by Makower | show that 
similar effects are obtained with the excited activity produced 
from radium emanation. Some further experiments by 
Rutherford § with the emanation from radium indicate that 
while at atmospheric pressure the greater part of the excited 
activity is directed to a cathode by moderate electric fields, 
yet a small fraction (about 5 per cent.) goes to an anode. 
Reasons are then | loc. cit. I given for supposing that some of 
the active deposit particles carry a negative charge, thus 
accounting for their transmission to the anode. 
It seemed of interest then to find out whether the quantity 
of active deposit that goes to an anode changes when the 
pressure is varied. 
A comparison has therefore been made over a range of 
pressure extruding from '001 cm. to 10 cms. between the 
amount of activity imparted to a rod charged positively and 
then negatively when exposed for the same interval of time 
qua! quantities of the radium emanation. 
It w-as found that whereas the activity of the cathode 
decreased as the pressure was diminished, the anode showed 
a corresponding increase in activity. 
* Communicated by the Physical Society: read March 13. 1906 
t Kutherford. Phil. Mag. Feb. 1900. 
: Makower. Phil. Ma*. N v. 
§ Rutherford. Phil. Ma<?. Jan. 19( 
