



ELECTRICITY. 377 



Fig. 312. If three cylinders aro 



placed in a row, touching 



Y ^ ■ . one another, as in Fig. 312, 



V ^ k X ^ ^ and a positively electrified 



body, E, be brought in 

 proximity to one extremity, 

 E^i the electricities of the cyl- 



inders will be decomposed, 

 the negative being accumulated in N, and the positive repelled to P. If in 

 this condition the cyhnder P be first removed, and then the electrified body, 

 the separate electricities -will not be able to unite, as in the former experi- 

 ment, but N will remain negatively, and P positively electrified. 



Explain the ThesG experiments explain why an electrified 



lie^nZd^Bu^- surface attracts a neutral, or unelectrified body, 

 face attracts a g^^]^ ^g g^ pj<-]j jjall. It is not that elcctricitv 



neutral, or un- I •' 



electrified body, causcs attractious between excited and unex- 

 cited bodies, the same as between bodies oppositely, ex- 

 cited ; but that the pith ball is first rendered opposite by 

 induction, and attracted in consequence of this opposition. 

 A pith ball at a few inches distance from an electrified 

 surface, is charged with electricity by induction ; and the 

 kind being contrary to that of the surface, attraction en- 

 sues ; when the two touch, they become of the same kind 

 by conduction. 



A person may also receive an electric shock by induction. Thus, if a per- 

 son stand close to a large conductor strongly charged with electricity, ho 

 will be sensible of a shock when this conductor is suddenly discharged. 

 Tliis shock is produced by the sudden recomposition of the fluids in the 

 body of the person, decomposed by the previous inductive action of the 

 conductor. 



What is an "^^8. Au elcctrical machine is an apparatus, 

 cMnl?^ "*' ^y iiieans of which electricity is developed and 



accumulated, in a convenient manner for tho 

 purposes of experiment. 



ofwhatessen- -^.11 clcctrical machincs consist of three 

 an^ ''dectricai priuclpal parts, the rubber, the body on 

 machiM con- "whose surfacc the electric fluid is evolved, 



and one or more insulated conductors, to 

 which this electricity is transferred, and on which it is 

 accumulated. 



