Consfructioti of Voltaic Batteries. 28 5 



of powei" according to the relative distances of the two metals. 

 It consisted of a cylindrical earthenware vessel, four inches in 

 diameter, in which was placed a cylinder of zinc, as close to 

 the inner surface as possible : the centre contained a copper 

 coil, of one inch diameter, inclosed in a membranous bag, and 

 there were four other copper coils, of greater and different di- 

 ameters, so constructed, however, that the largest did not 

 contain a greater surface of copper than the smallest. When 

 the coil of least diameter was used, the deflection of the volta- 

 meter only reached 60"; on introducing the next in size and 

 removing the first, the deflection increased to 155"^; the third 

 brought the needle to 71°; the fourth to 74°; and the fifth, 

 which was distant only a quarter of an inch from the zinc, to 

 87'^. I repeated the experiment in an oblong trough, with 

 square plates of zinc and copper, gradually advancing the zinc 

 to the copper, and with the same results ; thus demonstrating, 

 that in the construction of voltaic batteries, whether square or 

 cylindrical, the nearer the surfaces of the metal are brought, 

 the greater will be the power developed. 



It may be well here to state that in the course of these ex- 

 periments I found that, in each pair of plates, an increase of 

 zinc surface beyond a certain limit will not give an increase of 

 power, and consequently I am of opinion that a larger quantity 

 of zinc than is requisite is employed in all the batteries in ge- 

 neral use. 



Having thus experimentally ascertained the proper distances 

 of the metals, as well as the best conducting fluids, I con- 

 structed a single voltaic battery, in which I brought the prin- 

 ciples already stated to bear, as much as the interposed mem- 

 brane and other circumstances would permit, and of which I 

 will now give a brief description : in an earthenware pot, six 

 inches deep and four wide, I place a cylinder of amalgamated 

 zinc, standing on three legs, half an inch long, cut out of the 

 cylinder, the depth of which, including the legs, is only two 

 inches; within this cylinder, and at three eighths of an inch 

 distant, stands a copper vessel, having a rim a quarter of an 

 inch wide surrounding its outer edge, round which the bladder 

 is tied ; the bottom of the vessel rests on a circular piece of 

 baked box wood, which projects one fourth of an inch beyond 

 the cylinder; a thin oblong bladder, well cleaned and moist- 

 ened, is drawn over all and fastened round the upper rim by 

 a string, the wood at bottom preserving it from contact with 

 the copper, which would otherwise injure the membrane. This 

 cylinder, which is the depth of the pot, is pierced with six 

 holes equidistant from the top and bottom, which communi- 

 cate with an inner cylinder, separated from the outside one 



