of a new form of Galvanic Battery. 51 



300 cast-iron, water-tight cells, each containing a porous cell 

 and zinc plate 4 inches square ; 110 cast-iron cells, each hold- 

 ing a porous cell and zinc plate 6 inches by 4; and 177 cast- 

 iron cells, each containing a porous cell and a zinc plate 6 

 inches square. The zinc plate of each circle was placed in a 

 porous cell, and the latter in a cast-iron cell. The inside of 

 each cast-iron cell was about a quarter of an inch wider than 

 the exterior of its porous cell. Slips of sheet copper about an 

 inch broad and 2^ inches long, were soldered to each cast- 

 iron cell, and to each of the 320 6-inch zinc plates. The 4-inch 

 plates were already furnished with screws and nuts. Each 

 iron cell was connected by a binding-screw with the next zinc 

 plate. The iron cells were kept in an upright position in nine 

 wooden frames, which were placed on wooden supports nearly 

 3 feet high. The battery was charged by pouring into each 

 cast-iron cell a mixture containing about twelve parts by mea- 

 sure of concentrated nitric acid, and eleven and a half parts 

 of double rectified sulphuric acid ; and by filling to the proper 

 height each porous cell with dilute nitro-sulphuric acid, con- 

 sisting of about five parts of sulphuric acid, two of nitric, and 

 forty-five of water. In charging the entire battery we used 

 about fourteen gallons of nitric and sixteen of sulphuric acid. 

 I abstained from using the solution of nitre through an appre- 

 hension that it would cause the exciting mixture in the cast- 

 iron cells to boil over. I know not whether this apprehension 

 is well-founded ; but I know that when ten ©r more cells are 

 employed, the exciting fluid in the cast-iron cells will soon 

 boil over, and produce nitrous fumes, if it does not contain 

 one quarter of its bulk of nitric acid. 



I have found by experiment that a cast-iron battery is about 

 fifteen times as powerful as a Wollaston battery of the same 

 size, and nearly as powerful and a half as Grove's. Hence 

 our new cast-iron battery, in which there are 96 square feet 

 of zinc, is equal in power to a Wollaston battery containing 

 more than 1400 square feet of zinc, or more than 13,000 four- 

 inch plates, and to a Grove's containing 140 square feet of 

 platina. Now the battery made by order of Napoleon for the 

 Polytechnic School, which was the largest zinc and copper 

 battery ever constructed, contained only about 600 square 

 feet of zinc; and the most powerful Grove's of which I have 

 seen an account did not contain 20 square feet of platina. 

 Hence the cast-iron battery belonging to the College is more 

 than twice as powerful as the largest Wollaston, and seven 

 times as powerful as the largest Grove's ever constructed. 



1 shall now describe a few of the experiments which were 

 made with our large cast-iron battery on the 7th of the last 



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