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LXXIV. An Accoiint of some Experiments ivlth a large Vol- 

 taic Battery. By i.G. Children, Esq. F.R.S.* 



In ISOf) I presented to the Society a short account of some ex- 

 periments performed with a Voltaic battery of unusually large 

 plates, which has been honoured by publication in the Philoso- 

 phical Transactions for that year. Since that period I have 

 constructed another of still larger dimensions, the effects of which 

 form the sul)ject of the present communication. The copper 

 and zinc plates of this apparatus are coimected together, in the 

 usual order, by leaden straps ; they are six feet long, by two feci 

 eight inches broad, each plate presenting 32 square feet of sm- 

 face. All the plates are attached to a strong wooden frame 

 suspended by ropes and pulleys, which being balanced by coun- 

 terpoises, is easily lowered and elevated, so as to immerse the 

 plates in the acid, or raise them out of it, at pleasure. The 

 first trials of the power of this instrument were made in Julv 

 IS13, in the presence of several philosophical friends ; but tht? 

 effects then fell very short of my expectations, arising, as I after- 

 wards found, from a defect in the construction, \Ahich has been 

 since remedied, and another copper plate added to each mem- 

 ber of the series, so that every cell now contains one zinc and 

 two copper plates, and each surface of zinc is opposed to a sur- 

 face of copper. This was done at the suggestion of Dr. Wol- 

 laston, and has very considerably increased the power of the 

 battery. From some comparative exjierimcuts, which I made 

 with a small apparatus, the increase in quantity of electricity, 

 thus effected, is at least: one half. The cells of the battery are 

 21 in number, and their united capacities amount to 945 gal- 

 lons. To each polo of the battery a leaden pipe, about 3-4ths 

 of an inch in diameter, is attached by solder, and tiie opposite 

 end of each pipe immersed in a basin of mercury, (a separate 

 basin for each pipe.) by means of which the circuit is completed, 

 and a perfect contact ensured. The first experiments I shall 

 mention were made on the comparative facility with which 

 different metals are ignited when placed in the electrical circuit. 

 For this purpose, in each experiment, two v.'ires of dissimilar 

 metals were taken, of equal diameter and lengtli ; cue end of 

 each was in coitact with one of the basins of mercurv commu- 

 nicating with the poles of the battery, and the other end bent 

 to an angle, and the wires connected continuously l)V hooking 

 them together. The length of each wire was eigiit inclies, and 

 the diameter j^tli «f '-'^ ineh. The battery was uiodcratelv 

 excited by a charge of one part acid diluted with 40 parts of 

 water. 



* From the Philosophical Transactions for 1815, part \u 



Exp. 



