274 
glass tube the emanation which left the first cylinder decayed 
completely before reaching the second cylinder. By this method 
of measurement the emanating power of AcX was directly com- 
pared with the standard emanating power of solid actinium. 
The experiments made in this manner showed: 
1) That the actinium immediately after removal of AcX gives 
practically no emanation. 
2) That the rate of increase of the emission of emanation of 
actinium after removal of AcX is the same as the rate of increase 
of its activity. 
3) That the emanating power of AcX decreases at the same 
rate as the activity of AcX. 
Since the emanation is only observed when actinium X is pre- 
send and is always proportional to the amount of actinium X, it 
must be a product of actinium X. 
The changes oceuring in actinium are shown in the following 
graphical representation !) together with the period required for 
transformation to half value. For comparison the ehanges taking 
place in thorium are also given. 
Table 2 
D ©; De Be & 
Ac AcX Ac Eman Ac A Ac B Ac C 
? 10:2 days 37 sek. 36 min. 1:5 min 
Th X Th Eman Th A Th B Th C 
3: ire yars 4 days 1 min 11 hours 55 min 
‘) See Rutherford Bakerian Lecture Loc. cit. pp. 180—190 and 204: also 
Miss Brookes Phil. Mag. Sept. pp. 382-384; (1904) also Bronson Amer. Journ. 
of Seience Vol. XIX, Feb. pp. 187. (1905). 
