68 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Before the above cells were measured, cells of the following types 

 were studied : — 



Zn - ZnCl, - AgCl in ZnCIo - Ag, 

 Zn — ZnBi'a — AgBr in ZuBro - Ag. 



The observed values corresponded roughly with those calculated, but 

 the readings were not constant enough to be worthy of detailed men- 

 tion. In the hope of securing greater constancy silver was substituted 

 for zinc, and two different strengths of argentic halide dissolved in 

 zincic halide were used around the electrodes, as in the experiments 

 with the nitrates. These also were not constant, and some interesting 

 2)henomena concerning their inconstancy are worthy of further investiga- 

 tion. After the partial failure of these two attempts, the nitrates were 

 resorted to with the satisfactory and interesting results described above. 



These measurements were carried on in the Laboratory of Physical 

 Chemistry in Boylston Hall, Harvard University. I wish to thank 

 Professor Theodore W. Richards for his kindly interest and aid in the 

 investigation, and especially for his many helpful suggestions when ex- 

 perimental difficulties were encountered. 



