O^ COMPOUND ELECTRICAL INSTRUMfiNT. 



On the fpon- trometer diverged with pofitive eledricity with twelve motions 



tanews dec- ^f ^i^^ j^^ g^j (-^ j|. jj^j ^f^^J, j^ j^^^j ^^^^ untouched for fix 



trjcity of this 



inftrumcnt, days. 



The probability of the foregoing fuppofition concerning the 

 property of the plates acquiring a charge of one eleflricity in 

 preference to the other, was more ftrengthened by the follow- 

 ing experiment, which has been repeated feveral times. The 

 inftrument was charged with negative eleftricity, and then left 

 without difcharglng for twenty-four hours, when fixteen mo- 

 tions of the lever made the electrometer diverge with pofitive 

 eleftricity. 



I make no doubt if the plates were of different metals this 

 efted would be more ftriking, and that in fome cafes we 

 Ihould have the contrary ele6lricity. I intend to conftruft one 

 of thefe inftruments in fuch a way that plates of any metal 

 may be put on, and their effect tried. I think this a fubjeft 

 well worth purfuing as it may throw fome light on fome of the 

 phenomena of electricity, which have their caufes at prefent 

 buried in obfcurity. 



Note reJpeSiing the Sufpenfion of Zinc in Hidrogen, and the con" 

 feqwnt Ignition and Fujion of Plaiina Wire. By Amicus. 



To Mr. NICHOLSON. 

 Dear Sir, 



Ignition and 1 EMPLOY a gajbmeter of a much more fimple conftru6lIon 

 fufionof platlna ^^^ much lefs expence than Lavoifier's, which that fKilful and 

 eazomete? °" ^ intelligent artift, Cuthhcrtfon, invented at ray entreaty, about 

 ten years ago. It is defcribed in your valuable Journal (quarto 

 feries, vol. II. p. 235.) The brafs rod or the thick wire, which 

 conveys the electric fire through the upper receiver, has about 

 half an inch of platina wire appended, to hang juft over the 

 aperture through which the hydrogen gas rifes at the bottom 

 in the brafs work. Zinc of any other fort of metal would 

 either be melted or readily oxided. But the other day, I was 

 much furprized to fee the platina wire, on becoming as ufual 

 . nd hot from the flame of the hydrogen gas, melt into globules 



as 



