62 THE ROYAL SOCIETY OF CANADA 
creased in strength until the ? radiation was eliminated. After measur- 
ing the ionization due to the / rays, the electromagnet was run back, 
the zine cylinder removed, and the joint y and / ionizations determined. 
42 
22 
1-8 
metres / F3 4. 
It is difficult toremove the fradiation by screens alone, or by a 
powerful magnetic field alone, but a combination of screens and field 
is very effective. 
