ELECTRICAL APPARATUS. 



269 



force of this repulsion is sufficient to raise 15 grains, the 

 arm, g, rises, the slider moves forward, and the ball, h, at 

 the other end of the arm, coming rapidly in contact with the 

 ball, d, connected by the chain with the jar, discharges the 

 electricity accumulated. And as the force of the repulsion 

 depends upon the intensity of the charge, the weight it has 

 to overcome affords a measure of this intensity, and enables 

 the experimenter to regulate the amount. A quadrant 

 electrometer, K, is also usually attached to the top of the 

 instrument. Price, $8.00 to $10.00. 



Fig. 291. 



BEMJ.PIKE J R 294BBOA'DWAY.NV 



I - ^IBrihiiilii 



Electrical Battery, with four Jars. (Fig. 291.) When 

 great force is required from the electric fluid, a number of 

 jars of the above description are placed on a metal coating 

 which forms a communication between their outside coatings 

 and the earth, and the insides of the jars have conducting 

 wires which pass to the prime conductor. In this manner 

 any number of jars may be charged with the same facility 

 as a single one, and from the powerful effect of the electric 

 fluid when it is thus collected, it is called an electric battery. 

 One with four jars is represented in the above figure. 



Price, four gallon jars, $10.00. 



" half " $8.00. 



" quart " $6.50. 



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