36 DESCRIPTION OF GALVANIC BATTERIES. 



Various means have been devised for removing the sulphate of 

 zinc, and adding corresponding quantities of new acid water ; the 

 most simple and effective of which, according to our experience, is 

 to make the battery trough much deeper than is required for the 

 plates, which may be supported either by grooves in the side of the 

 trough, cut to the proper depth, or by a fillet of wood, or perforated 

 false bottom ; so that the zinc salt when formed may fall under the 

 plates, and thus a much longer time elapse before its presence pro- 

 duces any decidedly bad effect. 



There can be no doubt, we think, that some easy means will yet 

 be devised for carrying off the dense solution of sulphate of zinc, 

 before it rises to the plates, and for replacing it by acid water from 

 above, thus giving to the battery a uniformity and steadiness of ac- 

 tion it does not at present possess. 



Danieii's Battery. A few years ago, some of the disadvantages 

 now detailed were to a great extent overcome by a very ingenious 

 arrangement discovered by the late Professor DANIELL. The dis- 

 covery consists in the separation of the zinc from the copper by a 

 porous diaphragm, such as bladder, unglazed porcelain, &c., and 

 the use of the two distinct fluids. The portion of the battery 

 containing the zinc is charged with dilute acid as before, but the 

 portion containing the copper is filled with a solution of sulphate of 

 copper. The action in this battery is similar to that described in 

 the ordinary battery : the zinc is dissolved by the acid, but the 

 hydrogen, instead of being evolved at the copper plate, combines 

 with the acid of the sulphate of copper : metallic copper is thus set 

 at liberty upon, and combines with, the copper plate of the battery, 

 not only maintaining but improving its surface, during the evolution 

 of a constant current of electricity. From the 

 constancy of the current maintained the bat- 

 tery has been termed the Constant Battery. 

 The construction of a single pair is described 

 by Professor Daniel! in the following terms : 

 " A cell of this battery consists of a cylin- 

 der of copper 3J inches in diameter, which 

 experience has proved to afford the most ad- 

 vantages between the generating and conduct- 

 13 ing surfaces, but which may vary in height 



according to the power which it is wished to 

 obtain. A membranous tube, formed of the gullet of an ox, is hung 

 in the centre by a collar, and a circular copper plate, resting upon a 

 rim, is placed near the top of the cylinder, and in this is suspended, 

 by a wooden cross-bar, a cylindrical rod of amalgamated zinc, half 

 an inch in diameter ; the cell is charged with eight parts of water, 

 and one of oil of vitriol, which has been saturated with sulphate of 



