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Transactions of the Canadian Institute. [vol, ix 



The distance between the polonium deposit and the surface of the electrode 

 B was 6 mm. The polonium and the surface of the electrode B were coaxial. 

 The brass cylinder which was made air-tight with wax was connected to 

 the McLeod gauge and the Gaede air-pump by a tube D. The polonium 

 coated electrode, A, was connected to a battery, and the brass electrode, 

 B, to a sensitive quadrant electrometer. The brass cylinder surrounding 

 the two electrodes v/as connected to earth. 



III. — Repetition of Logeman's Experiment. 



The experiment which Logeman made*^ was first repeated, and the 

 results obtained were similar to those obtained by him with identical 

 electrical fields. The experiment was conducted in the following man- 

 ner. By means of the Gaede pump the air was pumped out from the 

 apparatus to as low a vacuum as possible. The pressure of the air was 

 measured by means of the McLeod gauge, and when the pressure be- 

 came so low that the McLeod gauge could not measure it, which was less 

 than i/iooo of a millimetre of mercury the polonium was connected to 

 earth and the rate of charging of the brass electrode opposite was meas- 

 ured by means of the electrometer. Then the polonium was charged to 

 a series of different potentials by means of a storage battery, and the cor- 

 responding rates of charging of the brass electrode were ascertained. 

 Throughout the experiment the Gaede pump was kept going continu- 

 ously in order to withdraw any gas which might come from the walls of 

 the apparatus. 



The results which were obtained are given in Table I. 



Table I. 



In column I is given the voltage applied to the polonium, and in col- 

 umn II the charge gained per minute by the brass electrode opposite 



•' Proc. Roy. Soc. Vol. 78, Sept. 6, 1907. 



