hij Metals under the Influence of Alpha Rays, 917 



was put on the case, the experimental arrangements were 

 altered. 



Flo-. 3. 



CENT i METERS 



The polonium-coated plug P (fig. 3) is placed within the 

 evacuated chamber ; it is surrounded by a brass cylinder C, 

 whose opening limits the cone of rays so that they fall within 

 the ring E which supports the aluminium-leaf electrode. 

 Two other rings F and F ! above and below the electrode at a 

 distance of 7 mm. are also covered with the aluminium leaf; 

 they are in metallic connexion with each other and with the 

 case. The brass disk D is divided into six equal sectors ; 

 one of these is left blank so that the rays may be stopped, 

 while the five others have holes through them 1*3 cm. in 

 diameter. These five holes are covered respectively with 2, 



Phil. Mag.S. 6. Vol. 22. No. 132. Dec. 1911. 3 P 



