T,etfer from Vrofejfor PiBet ofGdneva. 149 



filtering paper, and preferve it for ufe in a clean glafs bottle. 

 To give this lac-varnilh a high gold colour, yellow wwd is 

 preferable to evcrv other fubftance. If the varnifh is intended 

 to !»c pale, and not to change the colour of the brafs, the 

 yellow wood may be omitted ; but if a ftronger colour be re- 

 quired, a half more of the yellow wood may be added. 



XXIV. Letter from Profefor ViCTiiT, F.R.S. Profefor of 

 Nulural Philofophj! at Geneva. 



D 



To Mr. TiUoch. 

 SIR, Paris, Oftober jj, iSoi, 



URfNG my ftay here, on my return from Enaland, 

 I have had the fatisfaclion of meeting often the celebrated 

 Italian profeiTor Volta, who, in company with his fri-end 

 Brugnatclli, profefTor of chemlftry at Pavia, has undertakea 

 a philofophical journey to this metropolis to give and to col- 

 left information. I have been repeatedly a witnefs to a moft 

 ingenious and interefiing ferics of experiments, bv which pro- 

 feflbr Volta dcmonfl rates the evident identity between what 

 has been called the gcd-vaji'icfu'id and common eleftricity. A 

 (hort cxpolition of the leading faels will not, perhaps, be un- 

 acceptable to your phllofophical readers. 



He begins bv fliowing, with the help of his conductor 

 and a common electrometer made with two hanging hits of 

 ftraw, a new and fundamental fact in eleftrics, viz. that dif- 

 ferent metals (and even other fubftances) mutually impart 

 to one another, by a viere dry cordacl, a certain quantity of 

 cle£tricity : after this exchange, made rather by a kind of 

 impulfe than bv affinity, they are found to poffefs oppofitc 

 ftalcs of eleclricitv, caiily demonftrable by the common tell 

 uith fealing-wax. 



He (hows afterwards, that if a fyftem of two diflcrcnt metals 

 be difpufcd in the following order — copper, zinc, copper — 

 without any intermediate condu6liiig liquid, no change of 

 the electric Itate takes place in that cafe; becaufe the influ- 

 ence of the copper on zinc on one fide, is balanced by a 

 fimilar and contrary inriuencc on the other. But if a piece 

 of wet paper be nut between, then the eleftrical equilibrium 

 is imnjedialely ueftroyed by the contact, and the phenomena 

 appear. 



The better the condnfting liquid happens to be, the greater 

 is the effett. Thus brlae or acidulated water a6l more ftrongly 



K 3 thau 



