1883.] the Electromotive Force and Resistance of Batteries. 49 



galvanic cell, and indicated the error due to changes of temperature, 

 but he remarked, " These affinities do not appear to be affected by any 

 changes of temperature between ranges of 50° and 212° F." 



Crova investigated the effects of heat on the electromotive force 

 alone, and he showed (1) that the electromotive force of a Darnell's 

 element decreases regularly with an increase of temperature ; (2) that 

 the electromotive force of a Grove's element increases with tempera- 

 ture ; (3) that the electromotive force of a single-fluid element of the 

 Smee type is independent of the variation of temperature. 



In 1862 Mr. James Dixon took advantage of the influence of heat 

 to take out a patent for hot batteries, and he suggested the employ- 

 ment of these batteries for the production of the electric light. 



In the same year (1862) Lindig* indicated a variation with 

 changes of temperature. 



In 1870 Bleekrodef made some further experiments in the same 

 direction. 



In 1872 Mr. Latimer Clark* showed that the electromotive force 

 of his standard cell varied inversely with temperature about '06 per 

 cent, for each degree Centigrade. 



In 1881 Herwig§ investigated the subject carefully, and showed 

 that polarisation diminishes with temperature. He found that 

 resistance decreased markedly with temperature, and that this was 

 more evident with small electromotive forces than with powerful 

 electromotive forces. 



In 1878 the author | [ in investigating the peculiar action of Byrne's 

 pneumatic battery, showed that its exceptional power was due to an 

 abnormal formation of heat in its interior, and that this acted, 

 principally, in reducing the internal resistance. 



As bearing indirectly also upon this question it should be noted that 

 Becquerel, Paalzow, and Kohlrausch and Nippoldt examined the 

 influence of heat upon the resistance of electrolytes, and showed that 

 it invariably diminished as the temperature rose. This was deter- 

 mined by them for various solutions. 



Now it is to be observed that in all these enquiries no one has 

 quantitatively separated the influence of temperature upon electro- 

 motive force from its influence upon internal resistance. It is quite 

 evident, from an examination of Ohm's law, that the variation in the 

 strength of current can be the result either of a variation in the 

 electromotive force alone or in a variation of the resistance alone, or 

 in an unequal variation of both together. The numerous discre- 



* " Phil. Mag.," 1865, I, p. 408. 

 f " Phil. Mag.," 1870, p. 310. 

 X " Phil. Trans.," 1873~ 



§ "Ann. Phys.," B. XI, H. 4, No. 12, p. 661. 

 || " Proc. Soc. Telegraph Engineers," 1878. 

 VOL. XXXV. E 



