Mr Hart's Improvement on the Galvanic Battery. 21 



tained double the surface. The comparative energy of these 

 two forms of the apparatus was ascertained in the manner 

 first proposed by M.M. Gay Lussac and Thenard, namely, 

 by the amount of gas evolved from the decomposition of 

 water collected in a graduated glass tube ; a method which, 

 according to these celebrated chemists, is a more correct mode 

 of estimating the power of the battery, than the ignition of 

 different lengths of metallic wire. In this way, two of Dr 

 Wollaston's batteries, each containing ten triads in porcelain 

 troughs, evolved a certain volume of gas in seventeen mi- 

 nutes, while a battery of the new construction, with the same 

 number of triads, but presenting only one-half the surface 

 of the other, yielded the same volume of gas in fourteen mi- 

 nutes. 



Such a result can be attributed to nothing but the superior 

 means of insulation possessed by this battery. 



The cells are formed by cutting the copper in the form 

 represented by Fig. 1. Plate I. ; they are then folded up as 

 seen in Fig. 2, and the seams grooved, A drop of tin is run 

 into each lower corner to render the cells perfectly tight, and, 

 at the same time, to increase the positive state of the copper. 

 Fig 3 represents the zinc plate cast in the usual manner, and 

 having a piece of screwed brass wire cast into the top of it in 

 order to suspend it by. 



Fig. 4 is a section of the battery, showing how the copper 

 tail of the first cell is connected with the zinc plate of the 

 second, and so on. This connection is rendered perfect by 

 joining them with a drop of solder. The zinc plates are kept 

 firm in their place in the cells by three small pieces of wood, 

 in the same manner as in Dr Wollaston's battery ; the whole 

 are then fixed (by means of screw-nuts fitted on the brass 

 wires) to a bar of baked wood, previously well varnished* 

 Fig. 5 represents the battery in its complete state. 



When the battery is small, two may be suspended on one 

 frame. When used for shocks, they may be arranged with 

 the positive and negative poles together, and joined with 

 wire to complete the circuit ; but when employed for defla- 

 gration, the batteries ought to be placed alongside of each 



