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THE ROYAL SOCIETY OF CANADA 



rays. In the first experiment, a heating jacket was placed about the 

 tube containing the charcoal so as to drive the air out of the latter 

 and the apparatus was exhausted as highly as possible with a Gaede 

 rotary mercury pump. After this was done the heating jacket was 

 removed from B' and when the latter had dropped to room tempera- 

 ture it was surrounded with a Dewar flask and cooled with liquid air. 

 When this was done a McLeod gauge attached to the apparatus showed 

 that the pressure in the vessel had been reduced to considerably below 

 •001 mm of mercury. The zinc disc X, whose surface had been care- 

 fully scraped before it was inserted in the apparatus, was raised until 

 contact was made between S and C. The polonium plate P was then 

 charged to various positive potentials by means of the storage battery 

 and the corresponding currents between P and X were measured with 

 the Dolazaleck quadrant electrometer joined to C. The capacity of the 

 quadrants and the attached electrical system was found to be 140 e.s.u. 

 The values of the applied potentials and the currents they produced 

 are given in Table I, and a curve representing them is given in Fig. 2. 



ao 3o 4o 5o eo 7o eo 



voLTAGt on poLoniun (Po6> 



Fig. 2. 



