410 THE ADDRESSES, LECTURES, ETC., OF 



most perfect manner the conception of storage, only that the 

 power obtained from it was exceedingly slight. In working upon 

 Sir William Grove's idea, twenty-five years ago I constructed a 

 battery of considerable power in substituting porous carbon for 

 platinum, impregnating the same with a precipitate of lead per- 

 oxidized by a charging current, At that time little practical 

 importance attached however to the subject, and even when 

 Plante, in 1860, produced his secondary battery, composed of lead 

 plates peroxidized by a charging current, little more than scientific 

 curiosity was excited. It is only since the dynamo-machine has 

 become an accomplished fact, that the importance of this mode of 

 storing energy has become of practical importance, and great 

 credit is due to Faure, to Sellon, and to Volckmar, for putting 

 this valuable addition to practical science into available forms. 

 A question of great interest in connection with the secondary 

 battery has reference to its permanence. A fear has been expressed' 

 by many that local action would soon destroy the fabric of which 

 it was composed, and that the active surfaces would become coated 

 with sulphate of lead preventing further action. It has, however, 

 lately been proved in a paper read by Dr. Franklin before the 

 Royal Society, corroborated by simultaneous investigations by 

 Dr. Gladstone and Mr. Tribe, that the action of the secondary 

 battery depends^ essentially upon the alternative composition and 

 decomposition of sulphate of lead, which is therefore not an enemy 

 of, but the best friend to, its continued action. The action of the 

 battery depends simply upon the decomposition of the coating of 

 sulphate of lead, so that, commencing with sulphate of lead on 

 both surfaces, this is on the one hand changed into metallic lead, 

 and on the other hand into peroxide ; by the action of the battery 

 in producing power it is changed back into its original condition ; 

 and there is no d priori reason why such a battery should not be 

 available for use for a very long time. Of course you cannot 

 expect to get quite as much of effect out of it as you put in. I 

 am not prepared to say precisely what the loss is, but certainly it 

 is not of such serious import as to prevent the practical use of 

 these secondary batteries. As regards their application to tram- 

 ways, their usefulness will extend to lines in the interior of towns, 

 and to crossing parts of towns where it would be difficult to esta- 

 blish separate insulated conductors ; in such applications the 



