408 



Mr. J. A. Fleming on the new 



1 n series without introducing contact. But if, instead of using 

 a cell containing acid, we place next A a cell, B, containing sodic 

 Pentasulphide, and bend over the lead plate of A to dip into the 

 liquid in B, and place in B also a copper plate, we shall then 

 have two cells joined up in series without dissimilar contact and 

 w T ith similar metals for terminals; and yet the action of the 

 liquids on the metals is such that in A the lead is positive to the 

 copper Cu, and in B the copper Cu 7 is positive to the lead. 

 Hence there is a regular rise in potential in passing through 

 the two cells ; and on joining Cu Cu' by a copper wire a current 

 flows through both cells in the same direction, and the general 

 effect is to urge round a current in the direction shown by 

 the arrows. It is obvious that we need not limit ourselves to 

 two cells. By forming a pile of alternate cells filled with acid 

 and alkaline per sulphide, connected by bent copper and lead 

 plates alternately (fig. 2), we shall be able to accumulate differ- 



Fig. 2. 



. Cu Cu 



>v Fb 





Ca 









Ph 

































^ 





*~ 







<- 







■*r- 







N0 3 H SjNaa N0 3 H S 5 Na^ 



ence of potential to any extent; and if the number of acid and 

 alkaline cells be equal, we shall always end with a plate similar 

 to that with which we began. Such a battery will exhibit a 

 difference of potential between its two terminals when the circuit 

 is opened, and will give a current when it is closed. In it we 

 have nothing but chemical action to rely upon both for creating 

 electromotive force and for maintaining the current. We have no 

 dissimilar contacts ; and as the terminal plates are similar, we can 

 effect the junctions with the electroscope without introducing an 

 unbalanced dissimilar contact. I have constructed such a bat- 

 tery of 60 cells ; and by the kindness of Professor Guthrie, to 

 whom my thanks are due, I have been permitted to compare its 

 potential with that of a DanielPs cell, by means of a quadrant 

 electrometer belonging to his laboratory. By this means it is at 

 once seen that the difference of potential increases proportionally 

 to the number of cells, the electromotive force of four cells being 

 about equal to that of one Daniell. Joined up with a galvano- 

 meter it indicates a current, which, however, rapidly falls off in 

 strength, owing to the formation of an insoluble cupric sulphide 

 upon the copper plates. Joined up in opposition to a single 

 Daniell' s cell, with a galvanometer included in the circuit, I find 

 that it requires from four to five cells to balance the force of the 

 Daniell at first immersion ; but after leaving it to work on short 



