COMPARATIVE COST OF DIFFERENT BATTERIES. 69 



as is often the case, if, while the operations are going on, the work- 

 men are employed in other necessary labour, a cheaper apparatus 

 will answer: but the student or manufacturer will, by the above 

 general results, be enabled to choose the process most suitable for 

 his purposes. It must be borne in mind that an 'allowance has to 

 be made on the first, second, and third, for wear and tear of porous 

 vessels, not included in the above estimate. Although the results of 

 these experiments give, exclusive of time, the cost of one pound of 

 electrotyped copper thus 



s. d. 

 Grove's battery ... 2 8 



Single cell 2 4-J 



Daniell's 34 



Smee's 24 



WoUaston's 23 



still we know from long experience in the use of single cell, Smee's, 

 and Wollaston's batteries, for manufacturing purposes, that the 

 price of the pound of copper deposited may be more correctly 

 stated at 2s. 6d. there being always loss in making the purest 

 article (the copper) from impure materials, as the sulphate of 

 copper. 



Mr. Smee, in his "Advice" to capitalists who propose entering 

 upon the business of electro-metallurgy, gives a table of expenses 

 incurred by the use of different batteries. But his rules are based 

 too exclusively upon theoretical considerations, and without that 

 regard for practical conditions which are so important to the 

 manufacturer. Mr. Smee recommends for use what he calls " an 

 odds-and-ends battery," composed of odd scraps of zinc put into 

 acid, having in the same vessel a piece of copper or platinized 

 silver, and a wire placed in contact with them, which forms the 

 electrode. This battery may be convenient for the amateur 

 electrotypist, as it enables him to use up all his waste zinc. 

 Eaw zinc, or spelter, Mr. Smee says, may also be used in this way, 

 constituting the cheapest of all batteries for manufacturing pur- 

 poses. The data of his calculations are as follows : The copper 

 sheet forming the positive electrode is quoted at Is. per lb.; wrought 

 zinc, 7d. per lb. ; raw zinc at little more than half the price of 

 wrought zinc, which we will call 4d. per lb., although he rates it 

 at 5d. Iron is given at from Id. to 2d. per lb. The equivalent 

 weight of copper is given at 32, of zinc at 32, and of iron at 28 ; 

 that is to say, 32 parts (say ounces) of zinc dissolved in the bat- 

 tery will, or should, deposit 32 ounces of copper ; and if iron be 

 used, 28 ounces of iron should deposit 32 ounces of copper. Thence, 

 in the plain language of a manufacturer, we should say that with 



