SECTION III, 1916 [151] TRANS. R.S.C. 
On the Initial Charged Condition of the Active Deposits of Radium, 
Thorium and Actinium. 
By G. H. HENDERSON, M.A., 
Instructor in Physics, Dalhousie University, Halifax, N.S. 
Presented by H. L. Bronson, Ph.D., F.R.S.C. 
(Read May Meeting, 1916). 
In spite of the fact that the transformations of the emanations 
of radium, thorium and actinium are accompanied by the expulsion 
of positively charged « particles, it is a well known fact that a large 
percentage of the active deposits of all three can be collected on a nega- 
tive electrode. This phenomenon has been the subject of a consider- 
able number of investigations. In the present investigation the writer 
is continuing work previously done on this subject, and it is hoped 
that many doubtful points and apparent discrepancies, which have 
arisen in previous investigations, have been cleared up and that a 
rational explanation has been found for the behaviour of the active 
deposits in an electric field. 
RESUME OF PREVIOUS WORK. 
In early experiments made by Rutherford,! the amount of the active 
deposit of thorium collected on a wire rod inside a cylindrical can 
was about 200 times as great when the rod was cathode as when it 
was anode. This showed that a large proportion of the active 
deposit particles (rest-atoms) were positively charged. However, if 
account be taken of the activity on the case, the percentage of the 
total activity on the cathode was less than 99-5%. In a similar 
way Rutherford? found that about 95% of the active deposit of 
radium was collected on the cathode. 
Working with radium emanation in air at pressures less than 
atmospheric, Russ* found that the amount of active deposit collected 
on a wire rod as cathode, decreased as the pressure was decreased, 
while that collected on the rod as anode increased with the decrease 
of pressure. This was probably due to the increased length of the 


1 Rutherford, Phil. Mag., Feb., 1900. 
2 Rutherford, Phil. Mag., Jan., 1903. 
3 Russ, Phil. Mag., May, 1908. 
Sec. III, Sig. 2 
