256 THE ROYAL SOCIETY OF CANADA 



'in conclusion, the author wishes to express her sincere thanks 

 to Professor J. C. McLennan for suggesting the subject and directing 

 the progress of the research. Thanks are also due to Messrs. Oppen- 

 heimer, of London, for their kindness in lending the diamonds used 

 in this investigation. 



Physical Laboratory, 

 University of Toronto. 

 May 15th, 1922. 



