30 0N GALVANISM. 



alkali, It immediately combined with the alkali, and, with 

 water, gave a yellow folution, fimilar to that from which 

 it was procured. Acids expel from this folution the oxide 

 of ofmium, which has the ufual fmell, and the power of 

 giving to infufion of galls the blue colour before mentioned. 



VIII. 



Remarks upon certain Obfervatiom of Mr. Wilkinson, 

 refpeding Gukanifm. By Ra. Thick nesse, Efq. 



To Mr. NICHOLSON. 

 SIR, Wigan, Dec. 17, 180-k 



FeftiiT'T ^ HE remarks of Mr ' Wilkinfon (which I have not had an 

 Tanifm, &c earlier opportunity of attending to) on my letter of the 20th 

 September, on galvanifm, are in general founded only on mif- 

 conception; the confequence, probably, of a hafty perufal 

 in a public room. He attributes to me an aflertion, " that 

 two metals are requifite to the production of galvanic pheno- 

 mena ;" but my words are, and particularly marked by italics, 

 " two metals, or other fubfiances ;" and were intended to 

 fignify two metals, or two other fubftances ; or one metal 

 and one other fubftance ; and to include even that which may 

 be diffolved in the water. The experiment, therefore, of 

 La Grave, with brain and mufcle, which Mr. W. adduces, 

 is not an exception ; and " that a fingle metal fuffices" per- 

 fectly with pure water only, he did not, I fancy, with to be 

 underftood. 



That copper and the other negative metals are, as I ex- 

 prefled, " acted upon by the hidrogen," I mud refer to Mr. 

 W. for authority, to pages 177 and 178 of your Journal ; and 

 that particularly filver (my words are copper, or filver) is 

 rendered more brittle, to page 85 : but there cannot, furely, 

 be flronger evidence that copper has an affinity for hidrogen, 

 and confequently an influence in the decompofition of the 

 water, than is afforded by the experiments in which hidrogen 

 gas is obtained from the copper of the pile, and oxigen gas 

 from the oxidated zinc ; part of the hidrogen, and of the ox- 

 igen, being prevented from uniting with, and borne away 

 from the metals by the electricity. 



Mr. 



