io accoiinlfor ihe VhcBiiomena of Electricity . 341 



contains its natural proportion. And as this natural proportion 

 is really an affirmative and alostractible quantity, why does not 

 another affinnative quantity produce repulsion and not attrac- 

 tion ? For an expermient to prove that, according to the hypo- 

 thesis, a repulsion between natural and affirmative quantities 

 does exist, vre need oulv refer to Dr. Franklin himself. " Hang 

 a silk tassel on the prime conductor, and bring an excited tube 

 under the tassel, and the threads will diverge. Because part of 

 their natural quantity is thereby driven out of them, and they 

 become negatively electrified, and therefore repel each other*." 

 From this he deduces the following principle ; " an electric 

 atmosphere not only repels another electric atmosphere, but will 

 also repel the electric matter contained in the substance of a 

 body approaching it; and, without joining or mixing with it, 

 force it to other parts of the body that contained itf." How 

 these conclusions can be reconciled to the fact, that a body in 

 the natural state is attracted by an excited electric, is difficult 

 to determine. 



This experiment of the tassel leads the Franklinians into an- 

 other difficulty. They have apphed the attraction of electricity 

 for matter to account for ;vhy bodies when repelled move with 

 their atmospheres. " If two bodies be both of them overcharged, 

 the electric atmospheres repel each other, and both the bodies 

 recede from one another to places where tlie fluid is less dense. 

 For as there is supposed to be a mutual attraction between all 

 bodies and the electric fluid, electrified bodies go along with their 

 atmospheres J." There mw^^ be an attraction between matter 

 and iti, natural quantity, but Dr. Franklin's experiment with the 

 tassel professes to show that there is a repulsion between an 

 affirmative atmosphere and the natural quantity. Hence tlie 

 surrounding media containing their natural portion should not 

 permit tlie recedence of the balls. 



In the present state of knowledge we suppose that an elastic 

 fluid is an assemiilage of material particles surrounded by atmo- 

 6j)heres of repulsion. The co-existence of such particles must 

 produce a state of uniform density which is called an equili- 

 brium. In the idea of an equilibrium repulsion alone is sup- 

 posed to operate, attraction must entirely be excluded. Hence 

 if by any means a number of j^articles li'ow great soever of the 

 fluid can be accumulated in any body, that body must repel an- 

 other wiiich may contain a number however few. This exactly 

 agrees with Franklin's conception of the case : he maintains 

 that quantities of fluid with any difference whatever of density 

 repel each other §. This principle is productive of a train of 



• Franklin, 100. f Il.i.l. 155. J Priebtlcj's Hist. 5Q. 



§ Franklin, 407. 



Y y tontra- 



