134 Messrs. Gee and Holden 



on 



on the temperature of the electrolyte. Finally, he makes use 

 of the assumption (3) that every monad ion carries the same 

 quantity of electricity ( = e). These assumptions are applied 

 finally to the case of unequal-sized electrodes, a plate of area 

 P and a point of area S, as follows. According to assump- 

 tion (2) the number of atoms which touch the plate in unit 

 time will be nP, and therefore by (3) the greatest quantity 

 of electricity which can leave the plate by ordinary convec- 

 tion in unit time is nPe, and similarly n$e is the greatest 

 quantity of electricity which can leave the point in unit time. 

 He then argues that, although n is a very large quantity, e is 

 a very small one, and that it may thus happen that nPe and n$e 

 are quantities of electricity small enough to be dealt with in 

 experiment. He then considers the effect of an E.M.F. (=E) 

 acting in the circuit for a very short time ( = t). Suppose 

 that the plate is the anode and let such an E.M.F. (=Ej) be 

 applied for a very short time ( = that the quantity of elec- 

 tricity which passes is equal to nPet. In this case, when the 

 E.M.F. applied is just sufficient to charge the nPt atoms which 

 appear at the plate anode during the time t of charge, Chris- 

 tian! says, from energy considerations, that the most favour- 

 able conditions for the passage of the electricity are attained, 

 or, in other words, the resistance of the cell is now a minimum. 

 If the E.M.F. applied be less than E p the resistance of the cell 

 increases because all the atoms which touch the anode are 

 not engaged in carrying the electricity; if, on the other hand, 

 an E.M.F. greater than E p is used, the resistance of the cell 

 again increases because a process analogous to spark-discharge 

 has to go on. Similarly, if the point is the anode, there will 

 be a certain E.M.F. ( =E*) for which the resistance of the cell, 



(F \ 

 = — ^ ]. Let 



the E.M.F. actually applied be E, there are then three cases 

 possible. Since E 5 <E, 



(1)E<E,<E„ (2) E,<E<E„ (3) E f <E J> <E. 



Now, according to Christiani, the resistance of the cell is 

 greater or less (i. e. an additional electrical transition resistance 

 is greater or less) according as the E.M.F. applied is more or 

 less different in value from that giving the minimum resist- 

 ance. Thus in case (1), where E is nearer to E,, the quantity 

 of electricity which passes will be greater if the point is the 

 anode. In case (2), where E is between E s and E p , there 

 will be one value of E which will give equal quantities of 

 electricity in either direction of E. In case (3), where E is 



