Conductors of Electricity) and during Electrolysis. 277 

 Mr. Grove's. 



Prof. Daniell's. -I 



{Platinum 

 Nitric acid 



Copper 

 Sulphate 

 of oxide 

 of copper 



Amalgam, zinc \ 1 

 Dilute sulp. acid J ~o^ 



Amalgam, zinc 

 Dilute sulphuric 

 acid 



«, cv , flron. Amalgamated zinc 



Mr. Sturgeon s. | Dilute su]p fi urk acid 



Mr. Smee's. 



{Platinized silver. Amalg. zinc 

 Dilute sulphuric acid 



{Copper. Amalgamated zinc 

 Dilute sulphuric acid 



75. Without entering particularly into the respective merits 

 of these arrangements, I may observe that each of the first 

 four may be used advantageously, according to the circum- 

 stances in which the experimenter is placed, or the particular 

 experiments which he wishes to execute. The zinc-iron bat- 

 tery is somewhat inconvenient on account of local action on 

 the iron; but then it presents great mechanical facilities in its 

 construction. Mr. Smee's and Mr. Grove's are also very 

 good arrangements ; but the battery of Daniell is the best in- 

 strument for general use, and is, moreover, unquestionably 

 the most ceconomical. 



Broom Hill, Pendlebury near Manchester, 

 March 25, 1841. 



P.S. In the above table of galvanic intensities, thatrof zinc- 

 iron immersed in dilute sulphuric acid is somewhat overstated. 

 Recent experiments convince me that when the iron is in its 

 best condition it possesses the same powers as the platinized 

 silver. I attributed the iron battery to Mr. Sturgeon, who con- 

 structed one of these excellent instruments early in 1839*. It 

 consisted of twelve cast-iron tubes, furnished with strips of amal- 

 gamated zinc. But I find that the experiments of this gen- 

 tleman were not published as early as those of Mr. Roberts. 

 Prof. Daniell (Phil. Trans. 1836, p. 114) observed that iron 

 is sometimes more efficient than platinum in voltaic associa- 

 tion with amalgamated zinc. 



August 11, 1841. J.P.J. 



[* A paper by Dr. A. Fyfe, on the employment of iron in the construc- 

 tion of voltaic batteries, appeared in Phil. Mag. for August 1837: S. 3, 

 vol. xi. p. 145.— Edit.] 



