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RAYS OF RADIUM 



141 



was closed by aluminium l-60th mm. thick, and behind this was placed 

 a plate of carbon 1 cm. thick and a lead plate 2 mm. thick. The electro- 

 scope and radiators were supported by as little material as possible, 

 and all supports were covered by lead to reduce the effect of any second- 

 ary radiation from them. In the position Aj, R, the angle of scattering 

 was about 50°. Three radiators were used, viz., 



A carbon radiator 12-5 cms. high, 7-5 cms. broad and 5 «84 cms. 

 deep, mass, 923 grammes. 



An iron radiator 12-9 cms. high, 8 cms. broad and 1'28 cms. deep, 

 mass, 1,020 grammes. 



A lead radiator 11 cms. high, 7*6 cms. broad and 0-88 cms. deep, 

 mass, 840 grammes. 



In the position Aj, Rj the angle of scattering was about 110°, 

 and the following radiators were used : 



A carbon radiator 15 cms. high, 15 cms. broad and 6 «4 cms. deep. 



An iron radiator 15 cms. high, 15 cms. broad and 1-7 cms. deep. 



A lead radiator 15 cms. high, 15 cms. broad and 0'3 cms. deep. 



Readings were taken with and without the radiator, the difference 

 being due to the scattered radiatoin. The intensity of the primary 

 rays was measured directly. The readings are given in tables 1 and 2, 

 in divisions per minute. 



TABLE 1. 

 Angle of scattering 50° 

 (a) Intensity of primary rays 100, Lead Lj 0-0 mms. 



(b) Intensity of primary rays 42-4, Lead Lj, 1-29 cms. 



