52 



THE ROYAL SOCIETY OF CANADA 



conductivity measured when the same radiation was al^sorbed by 

 liquid air. The genei'al results of these measurements therefore agree 

 with those obtained by Cliernacher with the lirjuids which ho used in 



Figure 6 



as much as they shew (1) that it is very much more difficult to obtain 

 satuiation currents with ionisation in liquid air by alpha rays than when 

 the ionisation was produced by the same radiation in air at ordinary 

 pressure and (2) that the current^ obtainable with a given field under 

 ionisation by alpha rays are very much less with liquid air than with 

 air at ordinary pressures. 



VI. Mobilities of Ions Produced by Alpha Rays in Air at High Pressures. 

 In ordei to clear up if possible the question of the relative mobilities 

 of ions produced by alpha rays in air at high pressures, the apparatus, 

 shewn in Fig. 7 was used. 



7Ô u.lec^ro merer ''OOQoàùà-^ 



To E<x, 



To 3ar/ er 



y 



Figure 



AB was a Ijrass plate about 8 cm. long canying a boss of the same 

 metal, CD about 2 cm. in diameter. MN was a second brass plate 

 attached to AB by insulating su])ports. Tiiis plate was provided with 

 a circular opening as shewn in the diagram and acted as a guard plate 



