Olf.CilEMlCAl ArFINfTr* 1ML 



i-f>Tt^ itt^tfferent elrctric'ml stateii, are made to act «n !fc«t4i 

 «tlier. 



•S^idf. Ilf ». It 13 an established fact, that ftx>in the contact Fxperimentt* 

 Hid s*^fiaration of dissimiUr and iosulattd metals there *^^„^^*^J^ 

 i» pT<H^J rd such a change in the electrical state of each pnxiiiced hff 

 toetaJt that, after the teparatiou the cue is found to t)e po- <^«"i"t <" #»• 

 mtive^ the otiier negative in relutiou to fturronndui*^ nouies; 

 but it appeared to me, (not havinj;^ in mind tlie exf^erinients •"»'^ 



of W ilke and CEpious,) a matter of some doubt, whether the 

 alteration in electrical state is the effect of contact, or of 

 •eparation. To delerniine this point, in plac^ of the small 

 plate which usnully remains on my electrometer, I adapted a 

 copper plate about 5 inches in diameter. It is evident, tliut ' 



when this apparatus is placed on a common table, the coj)- 

 per plate will be connected with the wire and <;old leaves, 

 Lut wiJi in every other respect be perfectly insulated ; and, 

 jconseipiently, ihat, whenever ii state, different from that of 

 surrounding h>odies, is produced in the copper plate, it will 

 be indicated by a divergence of the gold leaves. 



The apparatus, above descril)ed, being so circumstancedj 

 that the tin foil of the electrometer was connected with th^ 

 Xilarth, while the copper plate, the wire, and the gold leave* 

 were insulated, ) brought^ by means of an insulating handle^ 

 a z\uc plate, also about ,5 inches in diameter, into .contact 

 with the copper plate on the electrometer ; but although, 

 they remaint'd some time in contact; there was no visible 

 divergence of the gold leaves. Un sp^)arating the metal*;, ,wl 



the gold leaves immediately diverged;; on again bringing 

 them .into contact, if the charge of the zinc plate !iad not 

 been removed, the leaves returned to their natural position; 

 on Jignin separating the plates the divergence took place b«, 

 before, and similar phenotnena ap|>eared, a^ often as the ex- 

 periment wab repeated. If the charge of the i^inc j)late had * , 

 been removed atter the separation, the succeeding contact 

 did not reduce the gpld leaves to their natural state; but 

 left^ slight divergence in them; and when the plates were 

 •gain separated they diverged in a greater degree, than after 

 the preceding separation. Ihus, by repeating the ejcperi- 

 ment, and discharging the zinp plflite afiiereach.6eparation» 

 the divergence wa« considerably increased; not however be- 



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