46 



Tin-: ROYAL SOCIETY OF CANADA 



(b). In a second set of measurements the apparatus shewn m 

 Fig. 3 was used. This consisted of a plate GH separated from a 

 second plate EF by two small blocks of clean ebonite. The plate EF 

 was provided with an opening shewn in the figure somewhat over 1 sq. 

 cm. in area. A third plate CABD was attached to EF by ebonite 

 supports and was bent so that he portion AB occupied nearly all the 

 space provided by the opening in FE. 



To a • IT» .• 



Figure 



A polonium coated copper plate about 1 sq. cm. in area was attached 

 in this case to AB, that portion of the plate CABD which lay within 

 the opening in FE with its active face towards GH and with its surface 

 in the plane of EF. With this arrangement CABD acted as an electrode 

 and EF as a guard plate for it. The supports to these plates were 

 heavy copper wires about 60 cms in length. One of tliem, KC, was 

 surrounded with a tube of clear fused quartz, and the others LF and 

 MG with tubes of glass. In making the measurements the wire L was 

 kept connected to earth, the wire M joined to a battery of storage cells 

 and the terminal K to the free quadrants of the electrometer. The 

 distance between AB and GH was about 5 mm. The capacity of the 

 system including the electrode AB, the free quadrants and the leading 

 wires, was in this case about 200 e.s.u. 



A number of sets of readings was taken with this apparatus of the 

 conductivity impressed on the liquid air by the rays from polonium 

 and these readings all gave curves similar to those shewn in Fig. 2. 



