emitted by Zinc bombarded by Alpha Rays. 499 



60Jvolts positive readings were taken with increasing mag- 

 netic fields up to 1245 gauss. These readings are given in 

 Table IV., and the curve representing them is shown in 

 PI. VJI. fig. 5. 



Table IV. 



Zinc surface first sera 



ped clean ai 



d then expo 



sed to air 



1 



at atmospheric pressure 



for six days 





Voltage on 

 ' Polonium. 



Current 



through 



coils. 



Magnetic 

 field. 

 Gauss. 



Deflexion 

 per min. 



Current 



xio 5 



e.s.u. 



Volts. 



amps. 





mm. 





zero 



zero 



zero 



- 8 



-25 



+ 2 



51 



ii 



5 



16 



6 



J> 



n 



22 



69 



10 







24*5 



77 



14 



n 



n 



25 



79 



20 



., 



M 



26 



82 



26 





tt 



26 



82 



'30 



)» 



i) 



20 



82 



40 







26 



82 



no 





tt 



26 



82 



80 



(| 





26 



82 



80 



•5 



240 



23 



72 



80 



•95 



405 



23 



72 



80 



13 



570 



225 



71 



80 



1-65 



680 



20 



63 



80 



2-3 



860 



17 



53 



80 



2-8 



995 



15 



47 



80 



;;-3 



1100 



145 



456 



80 



36 



1160 



14 



44 



80 



39 



1205 



14 



44 



80 



42 



1245 



14 



44 



I 



From these it will be seen that the maximum current 

 obtained without any magnetic field was 82 x 10" 8 e.s.u., 

 but that with the magnetic field applied the current fell to 

 44 x 10" 5 e.s.u., and this current, as was pointed out before, 

 consisted of (1) the residual ionization current, (2) the 

 stream of alpha particles from P, and (3) the stream of 

 recoil atoms from the same source. 



After this set of readings had been taken the liquid air 

 was taken from about the charcoal which was then allowed 

 to rise to room temperature. The heating-jacket was then 

 placed round it and its temperature gently raised so as to 

 drive off as much of the occluded air as possible. While 

 this was being done the Gaede pump was kept constantly in 

 action. Meanwhile the rod H was lowered with the wind- 

 lass W until the plate X was directly over the furnace F 



2 K 2 



