210 Description of an Elementary Galvanic Battery. [Sepr. 
wire of platina =.3;;* of an inch in diameter, even when the acid 
employed is very dilute. 
But for this purpose each surface of the zinc must have its coun- 
terpart of copper or other metal opposed to it ; for when copper is 
opposed only to one face, the action on the posterior surface of the 
zinc is wasted to little or no purpose. 
_ The smallest battery that I formed of this construction consisted 
of a thimble without its top, flattened till its opposite sides were 
about -2, of an inch asunder. The bottom part was then nearly one 
inch wide, and the top about .8,; and as its length did not exceed 
.”, of an inch, the plate of zinc to be inserted was less than 3 of a 
square inch in dimensions. 
Previously to insertion, a little apparatus of wires, through which 
the communication was to be made, was soldered to the zine plate, 
and its edges were then coated with sealing-wax, which not only 
prevented metallic contact at those parts, but also served to fix the 
zinc in its place by heating the thimble so as to melt the wax. 
A piece of strong wire, bended so that its two extremities could 
be soldered to the upper corners of the flattened thimble, served 
both as a handle to the battery, and asa medium to which the wires 
of communication from the zine could be soldered. 
The conducting apparatus consisted in the first place of two wires 
of platina about =4; of an inch in diameter and one inch long, 
cemented together by glass in two parts, so that one end of each 
wire was united to the middle of the other. These wires were then 
tinned, not only at their extremities for the purpose of being sol- 
dered to the zinc and to the handle, but also in the middle of the 
two adjacent parts for receiving the fine wire of communication. 
One inch of silver wire 1. of an inch in diameter, containing 
platina at its centre .. part of the silver in diameter, was then 
bended so that the middle of the platina could be freed of its coat- 
ing of silver by immersion in dilute nitrous acid. The portion of 
silver remaining on each extremity served to stretch the fine filament 
of platina across the conductors during the operation of soldering. 
A little sal-ammoniae being then placed on the points of contact, 
the soldering was effected without difficulty, and the two loose ends 
were readily removed by the silver attached to them. 
It should here be observed, that the two parallel conductors can- 
net be too near each other provided they do not touch, and that on 
this account it is expedient to pass a thin file between them (pre- 
viously to soldering on the wire) in order to remove the tin from the 
adjacent surfaces. The fine wire may thus be made as short as from 
=, to =); of an inch in length ; but it is impossible to measure with 
* For the method of drawing fine wires of platina, by coating them with a 
quantity of silver, I must refer to the description which i have formerly given of 
that contrivance. Phil, Trans, 1813, p. 114. See Annals of Philosophy, vol. ii. 
p. 233, 
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