176 THE ROYAL SOCIETY OF CANADA 



Summary 



The effects of ageing on some Standard Weston Cells of a modified 

 type have been examined and it has been found that the constancy 

 and accuracy of these cells, which may be constructed in any labor- 

 atory, compare favourably with those made according to elaborate 

 and more costly specifications. The assurance with which an absolute 

 mean value of voltage may be determined from a batch of old cells is 

 discussed. Also some objectionable characteristics of old cells are 

 noted, and a simple treatment for their partial elimination is outlined. 



The Macdonald Physics Building, 

 McGill University. 



