742 
Mr. S. Russ on the Electrical Charge 
actinium is reached, after which a diminution occurs, pro- 
bably owing to the fact that the total quantity of active matter 
collected on the two plates is then very small. 
At 2 mms. pressure the active matter obtained on the 
negative plate shows an increase as the plate is removed from 
the actinium, while the quantity on the anode shows a steady 
decrease. 
Fiff. 4. 
foe 
as 
6C 
4fc 
SO 
^ 
to 
'sj 
£ 
30 
^ 
cc 
zo 
tc 
C I Z 3 tf S 
J) l3tcun.ee in. cms. 
Crosses refer to 76 cms. pressure. 
Circles refer to 2 rums, pressure. 
It will be seen from fig. 4 that at atmospheric pressure 
the negative plate is more than one hundred times as active 
as the positive for small distances from the actinium, a very 
large diminution in the ratio resulting as the distance is 
increased. The opposite effect holds at a pressure of 2 mms. 
It has been shown by Debierne* that the amount of 
emanation obtained from a uniform layer of actinium falls to 
half value on going *55 cm. from the layer. We should, 
therefore, expect a diminution in the activity of the plates 
as their distance from the actinium is increased ; but the 
Le Radium/ 1S07, p. 213; 
