376 WELLS'S NATURAL PHILOSOPHY. 



What is the ''^^^- ^^^ earth is considered as the great 

 of eieJtriciTl' general reservoir of electricity. 



When by means of a conducting substance a communi- 

 cation is established between a body containing an excess of electricity and 

 the earth, the body will immediately lose its surplus quantity, which passes 

 into the earth and is lost by diffusion. 



What is dec 747. When a body charged with electricity 

 tricai induction • ^f q^q j^jn^j jg brought into proximity with 



other bodies, it is able to induce or excite in them, with- 

 out coming in contact, an opposite electrical condition. 

 This phenomenon is called Electrical Induction. 



_ , . .. This effect arises from the peneral law of electrical attrac- 



Explain the . , , . . , , . . 



phenomena of tion and repulsion. A body m its natural condition contains 



induction. equal quantities of positive and negative electricities, and when 



this is the case, the two neutralize each other, and remain in a state of equili- 

 brium. But when a body charged with electricity is brought into proximity 

 with a neutral body, disturbance immediately ensues. The electrified body, 

 by its attractive and repulsive influence, separates the two electricities of the 

 neutral body, repelling the one of the same kind as itself, and attracting the 

 other, which is unlike, or opposite. Thus, if a body electrified positively be 

 brought near a neutral body, the positive electricity of the neutral body will 

 be repelled to the most remote part of its surface, but the negative electricity 

 will be attracted to the side which is nearest the disturbing body. Between 

 these two regions a neutral line will separate those points of the body over 

 which the two opposite fluids are respectively distributed. 



■p,- „, , Let CAD, Fig. 311, be a metallic 



X l\i, olX* T -I , 1 ... 



cylinder placed upon an insulating 

 support, with two pith balls sus- 

 pended at one end, as at D. If 

 now an electrified body, E, be 

 brought near to one end of the cyl- 

 inder, the balls at the other ex- 

 tremity will immediately diverge 

 from one another, showing the pres- 

 ence of free electricity. This does 

 not arise from a transfer of any of 

 llie electric fluid from E to C, for upon withdrawing the electrified body, 

 E, the balls will fall together, and appear unelectrified as before ; but the 

 electricity in E decomposes by its proximity the combination of the two 

 electricities in the cylinder, CAD, attracting the kind opposite to itself 

 toward the end nearest to it, and repelling the same kind to the further 

 end. The middle part of the cylinder. A, whidi intervenes between the 

 two extremities, will remain neutral, and exhibit .either positive nor negative 

 electricity. 



