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THE ROYAL SOCIETY OF CANADA 



battery of small storage cells. When air at atmospheric pressure, 

 carefully filtered liquid ah-, and xylene were in turn used as the di- 

 electric, and the potential difference mentioned applied to the condenser, 

 the charge obtained in each case was ascertained by discharging the 

 condenser through a sensitive ballistic galvanometer with a specially 

 constructed key supported upon a paraffin block. 



The deflections obtained in a series of measurements with the three 

 dielectrics are given in Table I. 



TABLE I. 



These numbers it will be seen, if we take the dielectric constant of 

 air at atmostpheric pressure to be unity, give 1*95 and 1'42 as the di- 

 electric constants for xylene and liquid air respectively. The value 

 obtained for liquid air is therefore about 5% lower than that given by 

 Fleming and Dewar. 



III. Electrical Conductivity Imparted to Liquid Air by Alpha Rays. 



(a). After we were satisfied from these preliminary experiments 

 that the liquid air as used was quite free from any contamination which 

 might impart a conductivity to it, a set of measurements was made 

 with the apparatus shewn in Fig .1. In this apparatus two copper 

 plates A and B were supported by two thick copper wires 

 EA and FB. The former was surrounded with a glass tube and 

 the latter with a tube of clear fused quartz. Both were supported by 

 pieces of ebonite carried by two metal rods G and H attached to an 

 earthed metal case which was large enough to contain all the apparatus. 



