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high, six and a half broad, and about an inch wide, for the 

 six-inch plates. I also ordered 300 cast-iron, water-tight cells, 

 each about four and one-eighth inches high, five inches broad, 

 and an inch wide, to hold the small porous cells; and 320 cast- 

 iron cells, each about six and one-eighth inches high, seven 

 and a quarter broad, and one and three-quarters wide, to con- 

 tain the large porous cells. The new battery then was to 

 consist of 620 voltaic circles, in which the entire zinc sur- 

 face would be 113 square feet, and the surface of cast iron 

 would exceed 226 square feet; but on account of several dis- 

 appointments I have been obliged to be content for the pre- 

 sent with 577 voltaic circles, containing ninety-six square feet 

 of zinc, and about 200 square feet of cast iron. In this battery, 

 which was exhibited in the College on the 7th of the last 

 month, there were 300 cast-iron, water-tight cells, each con- 

 taining a porous cell and zinc plate four inches square; 110 

 cast-iron cells, each holding a porous cell and zinc plate six 

 inches by four; and 177 cast-iron cells, each containing a 

 porous cell and a zinc plate six 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 two and a half 

 inches long, were soldered to each cast-iron cell, and to each of 

 the 320 six-inch zinc plates. The four-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 three feet high. The 

 battery was charged by pouring into each cast-iron cell a 

 mixture containing about twelve parts by measure of concen- 

 trated nitric acid, and eleven and a half parts of double recti- 

 fied sulphuric acid ; and by filling to the proper height each 

 porous cell with dilute nitro-sulphuric acid, consisting of about 

 five parts of sulphuric acid, two of nitric, and forty-five of 



