on a lathe
or an improvised spindle provided with a handle of some kind. The wire
should be uncoiled and wound on some circular object, to ensure its paying
out regularly without kinking; which makes neat winding almost impossible.

Draw a foot of the wire through the hole in the reel, and drive in a tiny
peg--which must not protrude inwards--to prevent it slipping. Lay the
turns on carefully, forcing them into close contact, so that the next layer
may have a level bed. On reaching the end of the layer, be equally careful
to finish it neatly before starting back again. When the wire is all on,
bore a hole as near the edge of the finishing edge as possible, and draw
the spare wire through. Then cut a strip of tough paper of the width of the
coils, coat one side with paste, and wrap it tightly round the outside to
keep the wire in place.

Note.--Insulation will be improved if every layer of wire is painted over
with shellac dissolved in alcohol before the next layer is applied.

Flatten the reel slightly with a file at the points of contact with the
baseboard, to prevent rolling.

The plunger is a tube of thin iron, 1/16 inch less in diameter than the
hole in the reel, and 1/4 inch longer than the reel. If a ready-made tube
is not available, construct one by twisting a piece of tin round a metal
rod, and soldering the joint. As it is difficult to make a jointed tube
cylindrical, and a close fit is needed to give good results, it is worth
going to a little trouble to get a plunger of the right kind.

The ends of the plunger are plugged with wood and bored centrally for the
slide rod, which should not be cut to its final length until the parts are
assembled.

The crank shaft is 2-3/4 inches of a stout knitting needle mounted in a
sheet brass bearing. The crank, a fragment of oak or other tough wood, is
balanced, and has a throw of 5/8 inch. The crank-shaft hole should be a
trifle small, so that the crank shall get a tight hold of the shaft without
pinning. The collar, D, and wipe, W, are soldered to the shaft after this
has been passed through its bearings. The brush B1 should press firmly, but
not unnecessarily so, against the collar. For B2 one must use very springy
brass strip, a piece about 3 inches long and 1/4 inch wide being needed.
Bend it to the arc of a large circle, and screw one end down to the base by
the binding screw T2. The other end, which should not touch the base, is
confined by the heads of a couple