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THE 
LONDON, EDINBURGH, ann DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[SIXTH SERIES.] 
DECEMBER 1904. 
LXVIL. On the Secondary Radiation caused by the B and y 
Rays of Radium. By A.S. Evz, M.A., McGill University *. 
HE experiments described in this paper were suggested 
by an investigation made by Townsendt on the 
secondary Rontgen rays. A summary of his results is given 
by J.J. Thomson (pp. 261-268) in ‘Conduction of Electricity 
through Gases.’ It was hoped that analogous work with the 
penetrating rays of radium would throw further light on the 
relationship between Rontgen andy rays. It will be con- » 
venient to state Townsend’s method and results at the outset. 
/ | 
| oes 
Secondary Rays through | eee por | 
Radiation. | Air. 35 ai 
2 : 
Air aralelatatate tape iatalelsimraiaiers 2 { 1 0) 
Aluminium ...... 6 35 
CARB et pcan | rs, 3°0 
Wea 6 iat ek 24 6:0 
Paraffin (Solid)...! 30 15°5 
1 Be fk pane tea a ) 66 2°5 
Vitti, 2 Sate / 68 3:0 
| 2-5 
The figures denote scale-divisions of the electrometer in 
10 seconds. The bulb employed was placed in a lead box. 
The Réntgen rays passed through a hole in the lead and 
struck the radiator; the secondary radiation was measured 
by the ionization current between a charged cylinder of wire 
gauze and an axial electrode connected with a quadrant 
* Communicated by Prof. KE. Rutherford, F.R.S. 
+ J.S. Townsend, Proc. Camb. Phil. Soc. x. p. 217 (1899). 
Phil. Mag. 8S. 6. Vol. 8. No. 48. Dec. 1904. OAL 
