G60 Dr. Sadler and Mr. Steven on an Apparent Softening 



off part of the radiation by sheets of different substances. 

 As the explanation o£ this softening was not manifest, it was 

 decided to make it the subject of further study. 



Fig. 1. 



The arrangement of the apparatus employed is shown in 

 fig. 1, drawn to scale. The bulb of the usual spherical form 

 had sealed into it three side-tubes all in one plane, two of 

 which were at opposite ends of a diameter, while the third was 

 along a radius perpendicular to the others. One of these 

 tubes had a fixed aluminium cathode C, curved so as to con- 

 centrate the cathode rays on the anticathode B placed at the 

 centre of the bulb. A thin sheet of aluminium ('00367 cm.) 

 was fixed between two similar brass disks. One of these was 

 soldered to a tube which slid on the glass tube facing the 

 anticathode. The radiation under examination was limited 

 to two beams, which passed through two holes ('4 cm. 

 diameter) in the brass disk situated symmetrically with 

 respect to the axis of the tube, the distance between their 

 centres being 1*5 cm. 



A lead screen prevented any stray radiation from the bulb 

 from entering the two electroscopes (of the usual Wilson 

 type), E l5 E 2 , which were used for testing the radiation. In 

 the lead screen were two holes (*5 cm. diameter) corre- 

 sponding exactly to the two holes in the brass plate. The 



