SCIENTIFIC TRANSACTIONS 
OF THE 
ROW AIG IDWISIGIOIN SOM Tay, 
VOLUME IX. 
Ie 
ON SECONDARY RADIATION (PART II.), AND ATOMIC STRUCTURE. 
By J. A. McCLELLAND, M.A., 
Professor of Experimental Physics, University College, Dublin. 
(Read, Frsruary 21; Received for Publication, Marcu 24; Published, May 17, 1905. | 
Tuis paper is a continuation of one on Secondary Radiation recently published.* 
In that paper it was shown that when the 6 and y rays of radium are allowed 
to penetrate a substance, it emits a secondary radiation of negatively-charged 
particles. The penetrating power of this secondary radiation was measured, and 
its deflexion in a magnetic field was compared with that of the primary f rays, 
and the result showed that the primary and secondary 6 rays were similar in 
character. 
The relative intensity of this secondary 8 radiation given by a few different 
substances was compared; and, in the case of elementary substances, the atomic 
weight appeared to be the chief factor in determining the intensity. This point 
has been fully tested in the present paper, the secondary radiation from a large 
number of elements being measured under similar conditions, and the result 
indicated in the previous paper has been fully confirmed, the secondary radiation 
being always greater, the greater the atomic weight of the radiating substance. 
* Trans. Roy. Dublin Soc., Vol. VIII., Part XIV., 1905, p. 169, and Phil. Mag., Vol. IX. ‘Ser. VI.), 
1905, p. 230. 
TRANS, ROY. DUB. SOC., N.S., VOL. IX., PART I, B 
