to account fur the Vhcenomena of Electricity. 343 



vacant particle : or if a negative body be presented to a body in 

 the natural stale, there sb.ould be no attraction, yet in both cases 

 the contrai-y is the fact in an eminent degree. 



On this principle also of the attraction of electricity to matter 

 has the repulsion of a negative body by another been explained. 

 It is laid down by Frar.klin, that in this case when tlie bodies 

 are partly deprived of their quantity, the vacant particles of 

 matter are attracted by the denser fluid of tlie atmosphere, thus 

 causing a divergence. But the surrounding air, like other mat- 

 ter, strongly attracts its quantity of electricity and the reacting 

 attraction of the latter is exactly equal. From this it becomes 

 prol)al)le, and it is allowed by Franklin in many parts of his 

 works, that when electricity 's present in the natural proportion 

 only, it exerts no properties. How then can his other principle 

 be reconciled, namely, that it is the natural portion of the sur- 

 rounding media that causes tlie divellent attraction, or in other 

 words the apparent repulsion. 



But the divergence of the bodies shows that the natural 

 quantity of the surrounding air has been abstracted, as other- 

 wise these bodies in order to receive electricity need not diverge. 

 This diminution of the natural proportion of tlie air constitutes 

 a negatively electrified atmosphere. A ball surrounded by such 

 an atmosphere may lie conceived to lie in the central point of a 

 circle. The attraction of the denser fluid in the air, beyond the 

 negative atmosphere, is exerted on the ball : but as the attrac- 

 tion is equal on all sides, the ball remains stationary. Consi- 

 dering the extreme difficulty with which air* and other electrics 

 part with their ])ortion, it follows that if any sudden impulse be 

 given to the l)ail which can impart the smallest eccentricity, the 

 ball being no longer equally attracted, ought to fly to the nearest 

 pcripiieral part of the negative atmosphere where the boundary 

 of the denser fluid begins. For the motion of the ball is in- 

 stantaneous, and the alteration of electricitj- in the air is very 

 slow. It is almost unnecessary to remark, that this inferred re- 

 sult does not correspond with experiment. 



If two pith balls sus]>ended by a conducting thread hang in 

 opposition, and if an excited stick of wax be brought over them 

 they instantly separate by receiving the state of the wax. The 

 first effect of the wax was to rarifv the fluid natural to the balls ; 

 an attraction then commenced, between the balls and the conti- 

 guous stratum of air, and some time should elapse before this 

 stratum would be deprived of its share. The succeeding strata 

 ^hould slowly part with their quantities, and the balls in diver- 

 ging should occupy times proportional to the slowness of the 



* l'r;inUiii, passim. 



V 4 alteration 



