64 future's 



So you see that metals are relative, not abso- 

 lute, in their character as positive and negative 

 elements. 



The galvanic battery has been almost en- 

 tirely superseded in this country for tele- 

 graphic purposes by the dynamo, a machine 

 developing electrical currents by mechanical 

 power. Another form of battery that is ex- 

 tensively used for some kinds of heavy current 

 work is called the storage-battery. The man 

 who did the most, perhaps, to bring the storage- 

 battery to its present state of perfection was 

 Plante, a Frenchman, who died only a short 

 time ago. Although very many types of bat- 

 tery hare been developed, it is found that, 

 after all, the lines on \\hirh he developed it 

 make the most efficient battery. There is a 

 common notion that electricity is stored in the 

 storage-battery. Energy is stored, that will 

 produce electricity when it is set free, just the 

 same as energy is stored in zinc. The storage- 

 battery, when ready for action, is one form of 

 acid or primary battery. It has been made by 

 passing a current of electricity through it un- 

 til the chemical relations of the two lead 

 plates have been changed so that the potential 

 of one is greater than that of the other. A 

 simple storage-battery element is made up of 

 two plates of lead held out of contact with 

 each .other by some insulating substance the 

 same as the elements of an ordinary battery. 



