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1. Notice respecting the relative Voltaic agency of Circuits of 

 Copper and Zinc, and Zinc and Iron. liy Martyn Ro- 

 berts, Esq. Conununicatcd by the Secretary. 



While conducting some galvanic experiments, the author acci- 

 dentally used an iron-wire as a positive electrode, and was sur- 

 prised to find it was not oxidated, but, on the contrary, retained its 

 original brightness, and gave out oxygen-gas from water placed 

 under its action, in the same quantity Jis a platinum electrode would 

 have done in the same situation. 



Struck by this fact, he followed it up by a course of experiments, 

 and arrived at the conclusion that iron is in a singularly anomalous 

 electric condition, being positive when compared with copper, and 

 yet far more highly negative than copper when compared in their 

 electric relation with zinc ; and that although copper and iron form 

 a galvanic combination in which the iron is positive to the copper, 

 yet, when iron is associated with zinc as a galvanic pair, it pro- 

 duces a more powerful current of electricity than a galvanic pair 

 of equal-size, consisting of copper and zinc. 



A brief notice of illustrative experiments was given. 



The first experiments were made on the 1st January of the pre- 

 sent year. A galvanic pair, iron and zinc, immersed in dilute 

 sulphuric acid, was connected with two cups of a diflFerential gal- 

 vanometer ; another pair, copper and zinc, immersed in acid of the 

 same strength as that in which the iron and zinc was plunged, was 

 connected with the opposite cups of the galvanometer, both pairs 

 being of precisely the same area. The power of the iron and zinc 

 pair to deflect the needle of the galvanometer, exceeded that of the 

 copper and zinc pair by aS''. 



The author then constructed two small experimental batteries, 

 each consisting of ten pairs, fitted upon Wollaston's plan, the zinc 

 plates in both of which were 2^ inches square. One of the bat- 

 teries was a combination of iron and zinc, the other a combination 

 of copper and zinc. With the battery of iron and zinc, a cubic 

 inch of the mixed gases was decomposed in seven minutes, and 

 with the copper and zinc battery the same quantity required thirty- 

 three minutes for its formation. With the former, four cubic inches 

 were produced in 104 minutes, when the action ceased from neu- 

 tralization of the exciting acid ; with the latter, one cubic inch and 

 a half were formed in 125 minutes, and the acid liquor became 

 neutral. 



