JUDE 
SECONDARY RADIATION FROM COMPOUNDS. 
By J. A. McCLELLAND, M.A., 
Professor of Experimental Physics, University College, Dublin ; 
AND 
JB, JO), JEUA(OIKOOMMIN, INT Jo, 1B} ISG 
[Read, January 16; Received for Publication, Marc 13; Published, Aprin 12, 1906. | 
In previous papers* one of the present authors has studied, in considerable detail, 
the secondary radiation of 8 particles which is emitted by substances when they 
are exposed to the 6 (and y) rays of radium. The intensity of this secondary 
radiation was measured in the case of a large number of elementary substances, 
and, as shown in the papers referred to, it was found that the intensity of 
the radiation depended on the atomic weight of the element. ‘The secondary 
radiation is greater the greater the atomic weight, and increases with the atomic 
weight in such a way as to lead to an arrangement of the elements in divisions 
exactly corresponding to the division into periods employed in chemistry. In 
the previous papers the theory was advanced that the action producing the 
secondary radiation is entirely an atomic one. It was held that the electrical 
disturbance produced by the primary 8 particles penetrating the atoms of the 
substances exposed to them caused some of the atoms to break up, thus producing 
the emission of secondary £8 particles. The electric forces in the y-ray pulse 
will, obviously, act similarly to the electrical forces due to the penetration of 
the 6 particles, so that the y rays produce this secondary radiation as well as 
the 6 rays. If the emission of the secondary radiation is entirely an atomic 
property, it should be possible to calculate the intensity of the radiation given 
by a chemical compound, provided we know the radiating power of each of its 
constituents and the relative amounts of each present in the compound. 
* rans. Roy. Dublin Soc., vol. viii., part xiv, 1905; vol. ix., part i, 1905; and vol. ix., 
part u., 1906. 
TRANS, ROY. DUB. SOC., N.S., VOL, 1X., PART, ITI. I) 
