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THE ROYAL SOCIETY OF CANADA 

 Table IV. 



Zinc surface first scraped clean and then exposed to air at atmospheric pressure 

 for six days. 



From these it will be seen that the maximum current obtained 

 without any magnetic field was 82 x 10"^ e.s.u. but that with the mag- 

 netic field applied the current fell to 44 x 10"^ e.s.u. and this current 

 as was pointed out before, consisted of (1) the residual ionisation cur- 

 rent (2) the stream of alpha particles from P and (3) the stream of 

 recoil atoms from the same source. 



After the 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 

 windlass W until the plate X was directly over the furnace F and about 

 2 cms above it. When the pressure had been reduced to below 

 •001 mm of mercury a current of 10 amperes was passed through the 

 platinum wire of the furnace for 15 minutes. This sufficed to vapour- 

 ize the zinc in the furnace and to deposit a good coating on the surface 

 of the zinc plate X. 



