396 Precedes for accumulating Elenricity. 



chanifm, two inftrumcnts by Mr. Cavallo, and the indrument defcribed at p. 17 of t!ii» 

 Juurnnl. 



After the difcovcry of the method of inful.ition by Stephen Gray, the firft form in which 

 compcnfated cleiflricity was obferved appears to have been in the combination called the 

 elcftric jar ; in the explanation of which fo many of the earlier eleftricians have (he\vr> 

 their ingenuity. The next iiillance confilled in the application of conduilors to each other; 

 by which it was fliewn, that electricity is not equally diffufed over the fuiface of a condudt- 

 ing body, while any part of the electrified mafs which difl'ers in intenfity is fepnrated from 

 the rcll by tlieinrcrpofition of air or other tvon-conduclors. The cann and chain of Franklin, 

 and the eleftricil well of Beccaria, exhibited the principle of conipenfation in another light j 

 and the fubjeft was rendered (lill more difficult when the ftrong oppofitc electricities of 

 ribbands and filk (lockings, placed in contad>, expofed to fridion in that fituation, and 

 then feparated, were fliewn in the experiments of Cigna and Symmer. The vindicating 

 cleftricity of Becciria appeared to be ftill more remote fram the fimple general laws which 

 had been applied to explain the eflefl of the jar ; and the eleftropliore of Wilcke prefented 

 difficulties fcarcely lefs confiderable. 



The firft procefs for accumulating ele<flrlcity, which dilTers from that of mere friftion, 

 appears to have been invented by ProfelTor Lichtemberg *, and alfo by Dr. Klincock \, of 

 Prague. It was performed by means of two refinous plates like thofc of the common 

 eleftrophore, and one metallic plate with an infulating handle. When one of the refinous 

 plates had been (lightly rubbed, it was ufed to produce the oppoCte eledricity in the me- 

 tallic plate. This plate was then conveyed to the other refinous plate, and made to de- 

 pofit its electricity by applying its edge, or otherwife, to the noncondufting furface. The 

 laft-mentioned furface could then be ufed in the ordinary manner to give an eleftricity 

 to the metallic plate of the fame kind as that of the original refinous furface, to which it 

 ■was again applied by the edge. The eleiftricity of the firft refinous plate became thus in- 

 creafed, and, by the firfl-mentioned procefs, the metallic plate was returned to the other refi- 

 nous furface in a higher ftate of eleclrization. By a repetition of thefe manoeuvres, the two 

 plates were fpeedily put into as high a ftate of ele£tricity as they were capable of retaining. 



An accidental circumftance diredled the attention of Profe(ror Volta to the advantages 

 which might be derived from the increafed eleftrical capacity of the metallic plate of the 

 eleflrophore, when placed not upon the refinous plate, but on an imperfe<it)y conducting 

 fubftancej. If the laft-mentioned fubftance were a good conduftor, it would at fome part 

 of its furface be fo far in contaft with the upper plate as to carry o(F nny electricity com- 

 municated to this laft; and if it were a non-condu£tor, it might, and in moft cafes probably 

 would, pofTefs an eleftric ftate of its own which would influence that of the upper plate. 

 But the imperfedl condu<ftor will not readily produce the firft efFedt, and is incapable of 

 the latter. It therefore ferves only to afTume the contrary ftate of the upper plate when- 

 ever electricity is communicated to this laft, and renders it fufceptible of abforbing a much 

 greater quantity than it elfe could have done ; the nature and intenfity of which becomes per- 



• Journal dc Rozier, January 1780, p. 20. 



+ Philofophicil Trsnfaitions, LXVIII. p. 1OJ9. 



J Journal dc Phyfi^ue for May and Auguft 1783, and alfo the Philofophicsl Tranfiiflloos, Vol. LXXII. 



5 ceptible 



