4^4 Obfervalions on the Theory of EleBric AUraElion. 



If thefe atmofphcres be conceived to be formed by the repulfive nature of the fluid, 

 fome allowance (hould be made for the mutual repulfion of the two redundant portions 

 belonging to bodies j)ofitively ele£lrified. This however feems to be neglefted for the 

 purpofe of explaining the repulfion of bodies negatively eleftrified. But the difHculty 

 feems to be only changed. If the negative atmofphere adjacent to a body pofitively elec- 

 trified be caufed by the repulfion of the redundant fluid of the body, it will be neceflary 

 to fliew that this repulfion is overpowered by the attraftion fubfifling between that redun- 

 dant fluid and the portion of air thus deprived of a part of its eleftric fluid. 



But the reality of thefe atmofpheres of contrary ele£lricity may well be queftioned. It 

 feems to require, that we fliould conceive a portion of air contiguous to each body to be 

 permanently, during the mutual repulfion of the bodies in a ftate of eleftricity oppofite to 

 that of the bodies. But * it is afcertained experimentally, that the air furrounding any 

 electrified body acquires the fame ele£lriclty which had been poflefl*ed by the body, and re- 

 tains it even after the removal of the body. This muft be fuppofed, agreeably to the 

 known laws of eie£tricity, to be communicated by the alternate attraction and repulfion of 

 the adjacent particles of air. Each particle muft be firft attracted towards the body, and, 

 when by contaCl it has acquired the eleCtricity of the body, repelled from it. Inftead 

 therefore of a permanent ftate of contrary electricity conftituting thefe fuppofed atmof- 

 pheres, each adjacent fpace muft be occupied by particles, fome of which are attraCted and 

 others repelled. The time requifite for thus reducing the eleCtricity of the body to an 

 equilibrium with that of the furrounding air, is fufficient for explaining the continuance 

 of the electricity of the bodies, without the aid of the fecond propofition ; and the firft 

 propofition is deduced only from a confideration of bodies in a folid ftate. 



Poflibly a more diftinCt application of a principle, already in fome degree adopted both 

 by DoClor Prieftley and Mr. Cavallo, may remove all the difficulties of this inquiry. At 

 leaft I will hope, that it may lead to fuch a confideration of the queftion, as may fubjeCt 

 the merits of the theory itfelf to a fair and decifive difcuflion. This principle is faturation. 

 fDoCtor Prieftley has explained the communication of the redundant fluid of a body pofi- 

 tively eleCtrified to another, a part of whofe fluid had been prcviouQy expelled, by fuppofing 

 that it was more ftrongly attracted by the other body, than by its own which had more 

 than its natural ftiare -, and % Mr. Cavallo has in the fame manner accounted for the mu- 

 tual attraQion of bodies in different ftates of eleCtricity. 



In applying this principle to the folution of eleCtric phsenomena three forces muft be 

 confidered : ift. the attraction fubfifting between each body and its own portion of the 

 eleCtric fluid ; 2dly, the attraction which may fubfift between each body and the portion of 

 fluid belonging to the other ; and 3dly, the repulfion fubfifting between the two portions 

 of the eleClric fluid. 



• Cavallo's Complete Treatife on Eleilrieity, Vol. I. p. 316. 

 + Hiftory of EleJtricity, p. 253. t Vol, I. p. 109. 



That 



