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It is well known that the Groves Battery is the best of any in use for most purposes, and also the most expensive ; it is very intense, but must be kept in first rate order or it is valueless. Several months since Mr. Farmer (of the Boston Fire Alarm) entered upon a series of experiments, in order to obtain a battery which should have all of the properties of a Groves, with less trouble in keeping it in action, and a saving of expense. We give an engraving of the battery with an accompanying description. The outer cell is of stone ware, holding a gallon or more ; it is filled with the sulphuric solution, S, one of acid to twelve or fifteen of water. Standing in this cell is another jar, N, holding about a quart. This cell is filled with the nitric acid solution, one of acid and about four of water. The cell is made of common biscuit ware or glass, and glszed inside and out, save at the point r. This is the porous part of the cell. The glazing prevents the filtering of the nitric acid through into the sulphuric solution, and it also offers a greater resistances to the passage of the current. It is by altering the porosity of the cell that the right pioportion between the solid and fluid resistance of the circuit is obtained, and thereby the greatest amount of magnetic force, according to the general law given by Ohm, that the solid and fluid resistances of a circuit should be equal. The cells may be made of glass and a porous piece inserted or blown in. The nitric cells are covered, and the platinum strip, P, goes through it, and is soldered to the gutta percha covered wire, W. By covering the cell, the nitrous fumes are almost imperceptible, and by soldering the wire and platinum upon the outside of the cover, one trouble which so often occurs in Groves is avoided—the unsoldering of platinums. On the left hand side ot the outside cell, and standing within it is a pocket, ? ; it is made of common biscuit ware, and resembles a comb-case. In the pocket is some mercury, M, and standing in the mercury is the zinc, Z, and by its side is the other pole wire ot the battery W, which is also covered with gutta percha, save near the end which is immersed in the mercury. This is one cell ; a series of them are arranged as in any other. The advantages to be derived from this form of battery are the following :— 1st. Its great duration—it has been in use several months upon the short lines of the City Fire Alarm,and needs replenishing about I once in four months. Upon long lines it will probably maintain its action much longer. A battery set up on the 8th of November is now (Feb. 25th) in good Order; it has been used by several daguerreotypists with complete success. Mr. Whipple, an artist ot Boston, well-known for his genius and perseverance in photography, had one in action four months, without renewal of acid or disturbance ot any kind. L. H Hale, another artist, had one setup the 2nd Nov., and is in good action at the present time. 2nd. Its constancy.—The magnetometer gives but a slight variation of magnetic force, remaining almost stationary during the whole time. All telegraphers know the trouble of a variable current, and for silvering purposes it has the constancy of Smees and the intensity of Groves . 3rd. The use of zinc in any form—In the Groves the zinc must be of a particular form, and the arms are frequently eaten off at the acid line, before the body is consumed, which : renders the whole useless except as old zinc. In this form of battery all scraps of zinc ot commerce may be used. 4th. The amalgamation of zinc—In Groves it is well known that unless the zinc is kept clean by an amalgam, that the action is variable. In this battery the zinc should be amalgamated when first put into the acid, and then by capillary attraction the mercury is drawn upon it, always keeping it bright and in a condition for the acid to act. 5th. No waste of mercury—This is no inconsiderable item of expense, in a Groves, but here it is not exhausted, remaining in the pocket when the zinc is dissolved, and ready to ict its part again. 6th. The prevention of nitrous fumes, which are so disagreeable—This is accomplished by the cover upon the nitric cell which also prevents evaporation—a great source of loss in the Groves. 7th. The diminished porosity which has been before illustrated. 8th. Its economy—From all the various sources of gain, it amounts, in the aggregate, to a great deal. From eight months trial it would seem to be about fifty per cent., which will be a great item in telegraphing in this country, where competition and low rates tell largely upon the balance sheet.
