Make a “dry pile” as follows:—Cut out of silver-paper used by fancy
boxmakers, leaf zinc and writing-paper discs, of the same size, with a
die or punch.
Dry the paper in a gentle heat, and arrange the whole in two well-dried
glass tubes, beginning with the zinc, next silver-paper, paper side
down, the writing-paper, the silver-paper as before, and so on. Cement
in brass caps at one end of the tube, with screws to compress the pile,
and fasten a second cap after the column is inserted. This secures the
perfect metallic current.
Connect the tops with a wire, from the centre of which hangs a brass
ball to a raw-silk thread, to come in contact with a bell on the base of
each column when reared upright upon a stand. One column has its
positive end opposed to the other’s negative one, which makes the two,
when connected above, one continuous column. Groove the stand, and cover
all with a glass shade oval or round.
The ball will swing to and fro between the bells, repelled and attracted
alternately.
To recover lost power, insulate the columns for a few days.