'cH Ardmal Eledricifjr. ^of 



Wnnderable degree when the two metals mutuallv touch each 

 other. There arifes by the mutual contaft, for example, of 

 filver and tin, an a6lion or power by which the former com- 

 municates the electric fluid, and the latter receives it ; or the 

 filver fuffers it to efcape, and the tin attrafts it. This pro-^ 

 duces, when the circle is rendered complete by moift 

 conduftors, a ftream, or continual circulation of the fluid. 

 When the circle is complete, there is an accumulation in the 

 tin at the expence of the filver; which indeed is very fmall, 

 and far under the point neceflary to enable it to announce 

 itfelf by the moft delicate eleftromfeter. I have however 

 been able, by the afliftance of my condenfer, conftru6led on 

 a new plan, and fl:ill better byNicholfon's Doublcr, to rcndei" 

 it very perceptible : I (hall here communicate the refult ob- 

 tained by my experiments, which I made fome time ago with 

 great fatisfaftion. 



ExpER. I. The three plates of the doubler are of brafs. 

 I took two fl:rong wireSj one of filver and the other of tin, 

 and brought the former into contaft wiih the moveable 

 plate, and the other with one of the fixed plates; while they- 

 both rcfted on the table, or, what is better, on moift pafte- 

 board, or any other moift conductor, fo as to be in commu- 

 nication by the intervention of one or more conductors of 

 the fccond clafs. I fuff"ered the apparatus to remain -fome 

 hours in this ftate, then removed the two wires, and put the 

 machine in motion. After 30, 30, or 40 revolutions, (or 

 tnore when the atmofphere was not dry, or the infulalion 

 Imperfeft,) I brought one of my ftraw elcdlrometers into 

 contacl wltii the moveable plate, and obferved indications of 

 pofitive eleilricity ( + E) which arofc to 4, 6^10 degrees, and 

 more. If I fuftered it to touch the fixed plates, I had the 

 torrcfpondiiig indications of the oppofite kind of ele£lricity 

 (-E). 

 The filver, therefore, poured the elaftic fiuid into the brafs 

 :j plate wiien it had been fume lime in contuft with it; and 

 Ihe tin altravlled ii from the other plate, which A'as ajfo of 

 X 3 brafs, 



