ELECTROMOTIVE FORCES IN THE VOLTAIC CELL. 



517 



function, for simplicity, until forced to try something more complex. It 

 is quite impossible that /(C) can be a linear function really, but it very 

 likely begins by being so, and only for big currents diverges notably. A 

 hyperbolic tangent function, at a guess, would seem most likely to repre- 

 sent the case properly. 



Electromotive force of a zinc-zinc, dilute sulphuric acid, cell; of resistance \ 

 ohm, through which the specified currents are driven by tioo or three Groves. 

 Each plate exposing 53 square centimetres on each face. 



The agreement between the observed and calculated columns is not 

 very bad, and the polarisation E.M.F. does not show decided signs of 

 breaking away from the law of simple proportion until a current strength 

 of 4 amperes is reached ; say an intensity of "04 amperes per sq. centi- 

 metre of total surface. 



Electromotive force of a zinc-copper, dilute sulphuric acid, cell ; of resistance 

 ^ ohm, through ivhich the specified currents are driven by two or three 

 Groves. Each plate exposing 53 square centimetres on each face. E.M.F. 

 reckoned positive ivhen it helps the current fonvard, negative when it 

 opposes it. 



