432 Dr. A. 8. Eve : A Comparison of the Ionization 



By simultaneous observations on the current at each zone 

 of the plate described above, it was possible to test whether 

 similar effects were present in air, but had not been pre- 

 viously detected owing to the absence of a glow at the plate. 

 Thus any contraction of the area of discharge (corresponding 

 to a contraction of the glow in the case of hydrogen) would 

 be shown by a sudden increase of the deflexions of the galvano- 

 meters connected to the inner zones and a sudden diminution 

 in deflexion of those connected to the outer zones when the 

 total current was maintained constant. No such effect in 

 air was observed. Also when fluctuations of the total current 

 occurred they were invariably accompanied by fluctuations 

 of the same sign at each zone simultaneously. 



Summary. 



A method of comparing the specific velocity of ions under 

 different physical conditions, from the distribution of current 

 over the plate in point-plate discharge, has been tested for the 

 ions in air. 



The observed ratio of velocities of these ions at atmospheric 

 pressure agrees with the accepted value. Owing, however, 

 to the breakdown of assumptions as to the nature or! the 

 discharge the method cannot be applied to lower pressures, 

 and for the same reason has probably only a restricted appli- 

 cation in general. 



In the light of these results the question of the presence 

 of a discharge from the plate is discussed, with the conclusion 

 that though certain facts strongly point to its presence, it is 

 not necessary to the explanation of the above work. Finally, 

 certain special cases of discharge from the plate met with in 

 earlier work have been further investigated. 



XXXVIII. A Comparison of tlie Ionization within closed 

 vessels due to Rontgen and Gamma Rays. By A. S. Eve, 

 D.Sc, McGill University, Montreal*. 



IF closed cylindrical vessels, made of various metals, equal 

 in height and diameter, and with walls about half a 

 millimetre thick, are exposed to the action of Rontgen rays 

 and of the y rays from radium C respectively, then the 

 results obtained give a comparison of the ionizing effects of 

 the two types of rays. 



The results are at first sight surprising. 



* Communicated bv the Author. 



