The Ratio of the Electric Units of Charge. — By George 

 C. Laurence, B. Sc, MacGregor Fellow in Physics, Dal- 

 housie University, Halifax, N. S. 



(Presented 19 April, 1926) 



This work was undertaken to determine what accuracy 

 could be attained in the measurement of the ratio of the elec- 

 trical units of charge, using modern methods and apparatus 

 available in the average laboratory. The method used was 

 that of Rosa and Dorsay', that is, the capacity of a cylindrical 

 condenser, calculated in e. s. units from its dimensions, was 

 compared with its capacity in e. m. units measured in a Max- 

 well Bridge. A value of 2.9963 X 10 i .05% was obtained 

 which agrees better with Rosa and Dorsay's value 2.9971X10— 

 .01% — which is by far the best — than the values obtained by 

 earlier experimenters (except that of Fabry and Perot; 2.9978). 

 Accordingly it w as thought worth while to describe the simpli- 

 fications of the method which enabled it to be carried out in a 

 small laboratory. For a general treatment of the method the 



Fip: 1. 



reader is referred to Rosa and Dorsay's paper,nhe^wireing dia- 

 gram, however, is given in Fig. 1. The best values that have 

 been obtained for this ratio are: 



Himstead 



Rosa 



Thomson and Searle 



Abraham 



Pellat 



Hurmezesco 



Fabry and Perot 



3.0057X10 cm. /sec. 



3.0000 



2.9960 



2.9913 



3.0092 



3.0010 



2.9978 



Rosa and Dorsay (1907) 2.9971+ .01% 



^ Edward B. Rosa and N. E. Dorsay, Reprint No. 65, Bulletin ofjthe 

 Bureau of Standards, 1907. 



