Electric Deviation of Rays from Radiu m. 181 



Rate of Discharge of 

 Electroscope in 

 volts per minute. 



(1) Without magnetic field 8'33 



(2) With magnetic field 1'72 



(3) Kadium covered with thin layer I a,q» 



of mica to absorb all a rays ... \ 



(4) Radium covered with mica and } ^ ^ 



magnetic field applied ) 



The mica plate, '01cm. thick, was of sufficient thickness to 

 completely absorb all the a rays, but allowed the /3 and y rays 

 to pass through without appreciable absorption. The differ- 

 ence between (1) and (3), 7'40 volts per minute, gives the 

 rate of discharge due to the a rays alone ; the difference 

 between (2) and (3), 0*79 volt per minute, that due to the 

 a rays not deviated by the magnetic field employed. 



The amount of a. rays not deviated by the field is thus 

 about 11 per cent, of the total. The small difference between 

 (2) and (4j includes the small ionization due to the /3 rays, 

 lor they would have been completely deviated by the magnetic 

 field. It is probable that the ionization due to the J3 rays 

 without a magnetic field was actually stronger than this ; 

 but the residual magnetic field, when the current was broken, 

 was large enough to deviate them completely before reaching 

 the testing vessel. (4) comprises the effect of the 7 rays 

 together with the natural leak of the electroscope in hydrogen. 



In this experiment there was a good deal of stray magnetic 

 field acting on the rays before reaching the pole-pieces. The 

 distribution of this field at different portions of the apparatus 

 is shown graphically in fig. 2. 



Fiff. 2. 



hi 





f~* 



\ 







J \L 







<T}80 







3SOO 







— - ;!♦**> 



The following table shows the rate of discharge due to th<> 

 a rays for different strengths of the magnetic field. The 



