ACCUMULATORS. 79 





C 



the positive on the inner coatings varying in the same 



ratio. The same variation must also occur in the 

 resistance of the connectors, and produce a similar 

 effect, in a limited degree ; the resistance of a conductor 

 being directly as its length. 



If the charge given to the inner coating of A be 

 negative, the electric movement is reversed; all the 

 inner coatings becoming negative, and the outer pos- 

 itive ; electricity being attracted from the earth to the 

 outer coating of D. 



The insulations and connections should receive care- 

 ful attention, so as to prevent loss by leakage ; which 

 will inevitably occur if the insulation is imperfect, or 

 if the connectors have points, sharp edges, or projecting 

 corners. 



After the charge is given, the jars should be sep- 

 arated, placed in connection with the earth, and each 

 discharged separately. A single jar, charged to the 

 same amount, should then be discharged, and the 

 results -compared. 



This method will indicate, roughly, the amount of 

 charge of each jar ; but the electrometer, to be de- 

 scribed hereafter, will give more accurate results. 



THE LEYDEN BATTERY. When a number of jars 

 have their inner coatings joined by conductors, and 

 also their outer coatings in like manner, the combi- 

 nation is called a Leyden battery. 



A convenient form of such a battery is represented 

 by Fig. 22, in which connectors between the inner 

 coating radiate from a central jar. The outer coatings 

 are made of sheet brass, nickel-plated, and screwed to a 

 wooden base, their connections being made with copper 

 wires attached to the points of the screws underneath. 



