40 THE ROYAL SOCIETY OF CANADA 



The values for certain elements in groups 3 to 7 are given in the 

 table for comparison, but our knowledge of ionizing potentials is as 

 yet too fragmentary to permit of any definite conclusions. 



The ultimate solution of this problem may involve calculations 

 of the character given by Sir J. Thomson in his recent paper in the 

 Philosophical Magazine (March, 1921, p. 526). 



I am indebted to Professor A. LI. Hughes for his assistance in 

 endeavouring to collect the most reliable values for the ionizing 

 potentials. 



McGill University. 

 June 6, 1921. 



See also " Nature " 28th July, 1921. 



