Take an earthen jar and a porous tube; fill the tube with ten parts of
water and one of sulphuric acid; put it into the jar, into which pour
as much of a solution of sulphate of copper (blue vitriol) as will
fill three parts of it; place in the tube a piece of zinc, to which a
copper wire is soldered and bent round, so that one end be immersed in
the sulphate of copper; and a deposit of the copper will be immediately
formed upon the wire. If there be plenty of acid and water, so as to
allow of the action enduring for a long time, this process will go on
till it has deposited all the copper. This is the principle upon which
electrotyping proceeds--a principle referable to electro-chemical
decomposition.