as a Source of small Constant Currents. 

 Table III. 



365 



Fall of terminal P.D. of Large Cell when short-circuited 

 through 10,000 I. ohms. 



Date. 



Temperature. 



A. 



1888. 

 November 



1 



2°1-6C. 



volt. 

 0-000675 



>> 



1 



21-6 0. 



0000585 



>> 



2 



21-7 C. 



0000765 



„ 



1 



34-2 C. 



0000630 



„ 



1 



339 C. 



0000630 



„ 



1 



33-0 C. 



0000630 



» 



1 



32-0 C. 



0000720 



Fall of terminal P.D. of Large Cell when short-circuited 

 through 1423 1. ohms. 



Date. 



Temperature. 



A. 



1888. 

 November 1 



1 



2 



3°0-9 C. 

 306 C. 

 21-7 C. 



volt. 

 0-002925 



0-002565 



0-003150 



The result to be noted is that the value of A may be said 

 to have changed in the practical case from 0*005 to 0*003 volt 

 between 15° and 30° C. — a very small variation considering 

 the complexity of the changes which might have taken place ; 

 consequently we need not fear that any ordinary change of 

 temperature will introduce any appreciable error except that 

 arising from the ordinary temperature-coefficient of the cell. 



This experiment gives incidentally the value of the tempera- 

 ture-coefficient for rapid heating over the range comprised 

 between 21°*7 and 30°*9 C. Assuming Lord Rayleigh's 

 temperature-coefficient for the range of temperature between 

 15° and 21 0, 7 C, i. e. for temperatures which had been acquired 

 so slowly as to allow the zinc-sulphate solution to reach its 

 proper concentration with complete certainty, we have the 

 following : — 



