Section III., 1911. [69] Trans. R. S. C. 
On the Number of Ions Produced by the B Rays and by the + Rays from 
Radium C!. 
By A. 8. Eve, M.A., D.Sc., McGill University, Montreal, Que. 
In a previous paper,* an account has been given of the determina- 
tion of the co-efficient of absorption by air of the rays from radium C, 
and a mean value w= ‘004 em. — was obtained, suggesting an average 
path of the 8 rays of 2-5 metres in air at atmospheric pressure. This 
led to an estimate of the co-efficient of absorption of the y rays in air, 
pw’ =-000032 cm.+, somewhat lower than that given by the ratio wu’ 
/D=-034 of McClelland, whence w = -000044, and yet smaller than 
the value desired from p’/D=-04, found by Soddy and Russell. In 
the work that follows, the intermediate value pw’ — -000044 has been 
taken. The value for e, the electronic charge, has been taken as 
4-9 X 10- electrostatic units. 
In the present paper, experiments are described which lead to the 
evaluation of the total number of ions produced by 8 rays, and of those 
produced by the + rays, from one curie of radium C; that is, the amount 
of radium C in equilibrium with one gramme of radium. The heating 
effects of the g and + rays may thus be calculated, and also the average 
number of ions produced by one B particle, both in its average path, 
and for 1 em. of path. Corresponding values, necessarily speculative 
in their values, have been estimated for the 7 rays. 
Electroscope. 
The electroscope was formed of a light framework of knitting- 
needles, standing on wooden posts. The framework was covered with 
aluminium leaf -003 em. thick, offering a slight resistance to the B 
particle, not exceeding that of acm. of air. The internal measurements 
were 22 X 11-5 X 11-5 = 2990 cm.’. The central axis and aluminium 
leaf were insulated by amber beads, above and below, and the axis 
passed through the upper bead into the air for a distance of 7mm. 
and this exposed end was covered with an ordinary thimble, which 
could be removed temporarily for charging. The usual charging key 
* Phil. Mag., 1911. 
+ At short ranges with the active deposit of radium on aluminium foil, I have 
recently found # — -012 cm.-'. In this case RaB was also present. 
