SECTION III. 1911. [29] Trans. R. 8. C. 
On the Number of 0 Particles Expelled Concurrently with each « Particle 
Emitted by Polonium. 
By W. T. Kennepy, M.A., University of Toronto. 
Presented by Prof. J. C. McLennan. 
(Read May 16, 1911.) 
A problem which has been presented for solution for some time in 
connection with radio-active transmutations is the manner in which the 
active deposit particles in radium, thorium and actinium acquire their 
positive charge and in virtue of which they are attracted in an electric 
field to the electrode which is negatively charged. 
One inference which may be drawn from some observations on the 
active deposits from actinium which are recorded in a paper published 
recently by the writer! is that the active deposit particles at the instant 
of their production are uncharged and that their positive charge is ac- 
quired by contact with the surrounding ionized gas. 
This deduction may be made from the fact that when exposures are 
made to the emanation in a small chamber at the lowest. pressures at- 
tainable the amount of active deposit obtained on a charged electrode 
is practically the same, whether it be charged positively or negatively 
or whether it be uncharged. 
The active deposit particle, it is generally conceded, is produced 
by the expulsion of an & particle from the parent atom. 
As the a particle has been shewn to carry a positive charge of 
two elementary units it follows that if the active deposit particle is 
uncharged when it is created, the expulsion of the a particle, from the 
parent atom, must be accompanied by the emission of two delta par- 
ticles each bearing one elementary negative unit of electricity. 
As the expulsion of a particles from polonium is known to be ac- 
companied by the emission of delta particles it was thought that if the 
number of delta particles accompanying on the average the expulsion 
of one @ particle from polonium could be determined the result might 
possibly throw some light on the problem raised here in connection with 
the formation of active deposit particles from radioactive emanations. 
In the following paper an account is given of some experiments 
made in connection with such a determination. 
The manner in which the experiments were carried out is illustrated 
by the diagram shewn in Fig. I. A small copper plate N, coated with 
a thin deposit of polonium on its anterior face, was connected with a 
‘Kennedy. Phil. Mag. 1909, p. 744. 
