
222 RADIO-ACTIVE EMANATIONS [CH. 
Source of the Radium Emanation. 
146. No intermediate stage—Radium X—-between radium 
and its emanation, corresponding to the Th X for thorium, has 
so far been observed. The emanation from radium is probably 
produced directly from that element. In this respect, the radium 
emanation holds the same position in regard to radium as Th X 
does to thorium, and its production from radium can be explained 
on exactly similar lines. 
Radiations from the Emanations. 
147. Special methods are necessary to examine the nature of 
the radiation from the emanations, for the radiations arise from 
the volume of the gas in which the emanations are distributed. 
Some experiments to examine the radiations from the thorium 
emanation were made by the writer in the following way. 
A highly emanating thorium compound wrapped in paper was 
placed inside a lead box B about 1 cm. deep, shown in Fig. 41. 
There was an opening cut in To sbilechromnren 
the top of the box, over which ts 
a very thin sheet of mica was 
waxed. The emanation rapidly Mica 

diffused through the paper ito Til‘ 
the vessel, and after ten minutes Se 
reached a state of radio-active 
equilibrium. The penetrating power of the radiation from the 
emanation which passed through the thin mica window was 
examined by the electrical method in the usual way by adding 
screens of thin aluminium foil. The results are expressed in the 
following table: 
Thickness of mica window 0015 cm. 
Thickness of aluminium foil -00034 cm. 
Layers of foil Current 
0 100 
1 59 
2 30 
3 10 
4 3°2 
