4£ ELECTRICITY OF METALS. 



precipitate of metallic flakes as he defcribes; but, upon exami- 

 nation of thefe flakes, they yielded mercury by diftillation; and 

 the remainder con fitted of platina combined with a portion of 

 iron, but had not any properties which I could fuppofe owing 

 to the prefence of palladium. 

 Other fact- and Upon comparing the fpecific gravity of this fubftance, which 



JJj^JJSS. was (aid to be > at moft > l ] > 8 ' with that of mercur >' or of platiaa^ 

 di.im is a funplel was always ftrongly inclined to doubt the poffibility of its 

 metal# being compofed of thefe metals. I could recollect ho one 



inftance, in which the fpecific gravity of any compound is lefs 

 than that of its lighted ingredient, and could not, without care- 

 ful examination, admit (he fuppofition, that mercury could b® 

 rendered lighter by intimate union with platina. It now ap- 

 pears fully confirmed that this porfuafion, anting from uniform 

 experience, was well founded ; for, if we confider the diffi- 

 culty of producing even an imperfect imitation of palladium, 

 the failure of all attempts to refolve it into any known metals, 

 the facility of feparating it from any mixed folution of thofe 

 which it has been fuppofed to contain, as well as the number 

 and dittinclnefs of its chara&eriilic properties, I think we mute 

 clafs it with thofe bodies which we have mod reafon to confi- 

 der as fimple metals. 



XL 



Letter from Mr. Wm. Wilson, exhibiting the Electricity of 

 Metals, without the Help of any condenjing Injlrumtnt. 



To Mr. NICHOLSON. 

 SIR, 



London, Dec. 22, 1804. 



Whether the VV HEN I fet about making the compound electrical con- 

 meteKonc™ ^enfer defcribed in my la ft letter to you, I intended to repeat 

 the cflfcft of the the experiments of Cavallo relating to the ele&ricity obtained 

 contact or the by the contaft of metals related in the third volume of the 



r'nai'atioi)) 



fourth edition of his Treatife of Electricity ; but before the 

 infirument was finished, I was induced (by fome experiments 

 I had made relative to the cau'fe of excitation of electricity) to 

 fuppofe that it is not the contact of the meials that is the caufe 

 of the appearance of ele&rical figns, but the feparation of the 



metals 



