1840.] The Galvanic Battery, 1151 



superseded by an arrangement due to Professor Daniel, in which the re- 

 moval of the defects of former constructions has been accompanied by 

 some most important and peculiar advantages. Of this alone, there- 

 forC; will the details be given, and as zinc is procurable in this country, 

 both in the massive and laminar states, a simple modification of the 

 constant Battery adapted for the use of each, will be described. 



In the original form of the constant Battery in which the zinc is 

 [Fig. I. a.] used in solid rods, the copper element consists of a cylinder of 

 that metaf in its thinest obtainable state. The cylinder is formed, as 

 shewn in Fig. T, with a small collar, and to one side of it a small copper 

 cup to contain mercury, or a clamp-screw socket for facilitating 

 metallic connections throughout the Battery, is attached. 



The zinc element is a rod of that metal, varying in diameter and 

 [Fig. Lb.] length, according to the strength required for the Battery, 

 perforated at one extremity by a thin piece of wood, which, on the zinc 

 being inserted within the cylinder, rests on the collar, and prevents 

 any direct contact of the two metals. The rod is usually amalgamated 

 M'ith mercury, as will subsequently be described, and its exterior end is 

 made to terminate in a small mercurial connecting cup, or clamp-screw. 



The principal objection to the earlier forms of the Battery arose 

 from the rapidity with which the energy of their action was found to 

 decline. On this being traced to the deposition of particles of reduced 

 oxide of zinc on the copper plate, in consequence of certain chemical 

 actions within the cell, its recurrence was prevented in the constant 

 [Fig. I. C.J Battery by the interposition of a membranous partition be- 

 teen the two metals. This membrane is usually made of ox gullets, 

 and is so constructed, as readily to fit on to the collar of the copper 

 cylinder. Thus, then, the Battery when complete, with the exception 

 of the solutions, consists, (1) of the copper cylinder; (2) of the mem- 

 brane within this ; and (3) of the zinc rod separated from the copper 

 by the membrane. The dimensions vary according to the strength 

 required for the Battery ; that employed by Col. Pasley in his experi- 

 ments in February 1839, consisted of 10 cylinders, 21 inches high, by 

 3^ ditto in diameter, with zinc rods one inch in diameter. 



The modification of the constant Battery necessary for the employ- 

 ment of sheet zinc, consists simply in malting the copper cells rect- 

 angular instead of cylindrical, and the adoption of this form is much 



