I 



JPfeODtCTIGN O*" ELECTRiCITY BY FRICTtOST* 307 



I repeat, that no excitement of the Voltaic plates take$ 



place except the extensive surface of one plate be separated, 



perpendicularly, from the corresponding surface of the 



other, so that all points of contact between the two plates 



be broken at the same instant. If one plate be made to slide 



over the other, or if, after their separation, they be connect* 



ed by the smallest points, no excitement is indicated by 



either. 



The result is> however, different, if the experiment be per* Excitement of 



formed with two electrics, or with an electric and a conduc- ^^^ common 



/. , , , • 1 • ■ 1 ■ n . , electrical ma- 



tor; for the charge, which is excited in one set of particles chine. 



of an electric, is retained by them, and is not shared with 

 the rest of the body, to which they belong; consequently, 

 when any body is drawn over the surface of an electric, it 

 leaves a permanent charge on all parts, with which it comes 

 into contact. As, therefore, the particles of the cylinder or 

 plate of a common electrical machine are separated from 

 the rubber, they acquire a charge, which, as often as they 

 pass near the prime conductor, is partly removed ; and from 

 the alternation of these operations, during the revolutions of 

 the electric, a charge is accumulated in the prime conduc* 

 tor, until the whole of this body, if it be insulated, has ac- 

 quired a degree of excitement, equal to that, which the 

 action of the rubber is capable of giving to each particle of 

 the electric. The prime conductor draws its charge, by de- 

 grees, from the excited particles of the plate, or cylinder, 

 as they successively pass near it ; but, from its conducting 

 ^nahty, gives it, at once, to any other conductor. It is evi- 

 dent, that no accumulation can take place in the prime con- 

 ductor, while it is connected with the Earth ; and it is 

 equally obvious, that a conducting body, placed near to 

 the prime conductor, will, by removing stnali charges, as 

 fast as they are produced, effectually prevent its acquiring 

 a high degree of excitement. We may also observe, that 

 the action of an electrical machine becomes more energetic, 

 the longer it is continued ; for a repetition of the operations, 

 we have explained, causes a considerable augmentation of 

 temperature, which is favourable to the electrical action of 

 bodies, and adapts the rubber perfectly to the electric, ia 

 Consequence of which a greater number of points are excited 



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