272 Dr. C. It. A. Wright on the Determination of 



but the discrepancy was in no case so great as materially to 

 influence the general character of the curve representing the 

 variation in the value of the E.M.F. with varying currents, ob- 

 tained on plotting the results by making the currents abscissae 

 and the electromotive forces ordinates. The following table 

 (p, 273) exhibits, side by side, the values obtained in various 

 acses selected as specimens : in numerous other cases not quoted, 

 the curves obtained were considerably similar to those indicated 

 by the figures given in the table and represented in fig. 2. The 



Fisr. 2. 



3000 4000 5000 6000 7000 



Microamperes per square centimetre. 



resistance of the cell, It, is stated in ohms, and the electromo- 

 tive forces in volts: the "maximum E.M.F." indicates the 

 average value of the highest E.M.F. observed throughout the 

 various series of readings, this value being always observed 

 when either no current at all circulated, or a current of less 

 magnitude than about 8 microamperes* per square centimetre. 

 The copper plates were uniformly surrounded by nearly satu- 

 rated copper-sulphate solution (sp. gr. 1-175); the zinc plates 

 were sometimes surrounded by nearly saturated zinc-sulphate 

 solution (sp. gr. about 1*4), and were then lowest ; in other 

 cases they were highest, and were then surrounded either by 

 zinc-sulphate solution of sp. gr. 1*10, or by dilute sulphuric 

 acid of sp. gr. 1*045. 



* In accordance with the nomenclature adopted by the recent Interna- 

 tional Electrical Congress, the term amp&re is used throughout this paper 

 to indicate what in the former papers of this series was designated a weber 

 viz. O'l C.G.S. current-unit ; so that a microampere = -0000001 O.G.S.' 

 current -unit =10"^ ampere. 



