Active Deposits of Radium, Thorium, and Actinium. 605 
Fig. 2. 
1000 
> 
o 
< 
500 
100 
} 
o 
) 
CaJAocLz 
/° 
'+ a ■*■ ■!■+-: 
CLnwde 
■1 Z -3 U S -6 / S f 1 H 11 
Pressure in mms 
The system was initially exhausted to about 1 mm. pressure,, 
the emanation then let in and the small vessel isolated from 
the cylinder, the pressure in which was then adjusted to 
whatever value was required. The activity obtained on the 
brass rod after one hour's exposure was measured in exactly 
the same way as before. Observations w r ere made for a range 
of pressure extending from 2 mms. to 10 cms. The numerical 
data are contained in Table II., and the results shown 
