Dr. Wollaston made a simple apparatus out of a silver thimble, with its
top cut off. It was then partially flattened, and a small plate of zinc
being introduced into it, the apparatus was immersed in a weak solution
of sulphuric acid. With this minute battery, Dr. Wollaston was able to
fuse a wire of platinum 1/3000th of an inch in diameter--a degree of
tenuity to which no one had ever succeeded in drawing it.
Upon the same principle (that of introducing a plate of zinc between
two plates of other metals) Mr. Children constructed his immense
battery, the zinc plates of which measured six feet by two feet eight
inches; each plate of zinc being placed between two of copper, and each
triad of plates being enclosed in a separate cell. With this powerful
apparatus a wire of platinum, 1/10th of an inch in diameter and upwards
of five feet long, was raised to a red heat, visible even in the broad
glare of daylight.
The great battery at the Royal Institution, with which Sir Humphry Davy
discovered the composition of the fixed alkalies, was of immense power.
It consisted of 200 separate parts, each composed of ten double plates,
and each plate containing thirty-two square inches; the number of
double plates being 2000, and the whole surface 128,000 square inches.
Mr. Highton, C.E., has made a battery which exposes a surface of only
1/100th part of an inch: it consists of but one cell; it is less than
1/10000th part of a cubic inch, and yet it produces electricity more
than enough to overcome all the resistance in the inventor’s brother’s
patent Gold-leaf Telegraph, and works the same powerfully. It is, in
short, a battery which, although _it will go through the eye of a
needle_, will yet work a telegraph well. Mr. Highton had previously
constructed a battery in size less than 1/40th of a cubic inch: this
battery, he found, would for a month together ring a telegraph-bell ten
miles off.