352 ELECTRICITY. 



MISCELLANEOUS EXPERIMENTS. 



The Dancing-Balls. 



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Fix a pointed wire on the prime conductor, with 

 the point outward; then take a glass tumbler 

 (Fig. 7«) grasp it with your hands, and present its 

 inside surface to the point of the wire on the 

 prime conductor, while the machine is in motion : 

 the glass in this manner will soon become charged; 

 for its inside surface acquires the electricity from 

 the point, and its outside loses its natural quantity 

 of electric fluid through the hands, which serve as a 

 coating. This done, put a few pith balls on the 

 table, and cover them with this charged glass tum- 

 bler. The balls will immediately begin to leap up 

 along the sides of the glass, and will continue their 

 motion for a considerable time. 



In this experiment, the pith balls are attracted 

 and repelled by the electric fluid, superinduced 

 upon the inside surface of the glass, which they 

 gradually conduct to the table, or other conducting 

 body upon which the glass is set, at the same time 

 that the outward surface of the glass acquires the 

 electric fluid from the contiguous air. This expe- 

 riment may be made more diverting, by having a 

 glass cylinder three inches long, and the same in 

 width, open at both ends, with a brass plate fixed 

 on its top; put any number of balls you please, 

 and electrify the brass cover, and the balls will 

 dance with a very rapid motion, which will con- 

 tinue as long as the operator turns the machine. 



Electrical attraction and repulsion are also ex- 

 hibited in a very pleasing manner, by means of a 



