ON GALVANISM AND ELSCTRIClTTrf 175 



VIII. 



Letter from C. Wilkinson, Ejq. on Gakanifm and EUBricily* 



Dublin, Oa, 8, l&O*. 



To Mr. NICHOLSON. 

 SIR, 



HEN at Liverpool a few days (ince, at the Athenaeum Obfervatlons oa 

 I found a paper of Mr. Thicknefle of Wigan in your valuable galvanifm, &c. 

 Journal, and which has induced me to trouble you with the 

 following obfervation. Mr, T. ingenioufly conjectures that 

 the galvanic phenomena depend more upon the decompolition 

 of the water employed than as to any chemical change eflFeded 

 on the metals. Mr. T. obferves that two metals are requifite 

 to the production of galvanic phenomena : this is no ways the 

 cafe, it is well known that a fingle metal fuffices, or even brain 

 and mufcle, according to the experiment of La Grave, or 

 nerve and mufcle according to Aldini. Mr. T. further ob- 

 ferves that hydrogen mixed with copper always renders it brit- 

 tle. I fliould wifti to know this gentleman^s authority for fuch 

 an aflbrtion : he alfo fets out too hypothetically as to eleClricity 

 being a modification of caloric. It has always appeared to me 

 that the galvanic phenomena entirely depend upon the difen- 

 gagement of eleClricity from the metal undergoing a chemical 

 change, 



Galvani has afcertained that gold, filver, copper, iron, tin, 

 lead and zinc, conftitute the feries of metallic bodies; that 

 when two metals the moft remote in the feries are united, the 

 mod powerful galvanic combination is formed; thus gold and 

 zinc, filver and zinc, copper and zinc, &c. and laflly, lead 

 and zinc, form the weakeft galvanic combination. The difpo- 

 lition to oxidation is in the inverfe order, thus zinc will become 

 oxidated even by expofure to the air, whilft filver and gold 

 undergo this change with the greateft ditficulty. 



Hence a metal which is oxidated with the greateft difficulty 

 combined with a metal which oxidates with the greateft faci- 

 lity, form the moft powerful galvanic combination. The pro- 

 duction of galvanic phenomena is always proportionate to the 

 degree of oxidation, 



AU 



