150 THE ROYAL SOCIETY OF CANADA 



and if /zo is the refractive index for density po, and p is the actua^ 

 density, then 



PO ., PO NX 



^0 - 1 = (/x - 1) = • — 



p p I' 



Readings have been commenced with this apparatus, using 

 Thallium metal, and results are expected to follow shortly. The few 

 counts that have been made are consistent but no definite results 

 can be reported yet. 



In conclusion, the writer wishes to thank Professor J. C. McLen- 

 nan for suggesting this research and for helpful advice at all times. 

 He also wishes to thank the Honorary Advisory Council for Scientific 

 and Industrial Research for making it possible for him to undertake 

 this research. 



Physical Laboratory, 



University of Toronto. 

 May 15th, 1922. 



