, and then riveting them together so that their like
poles shall be together, and pull together. To make a small compound bar
magnet, magnetize several harness-needles, or even sewing-needles, and
then bind them into a little bundle with all the N poles at the same
end. Melted paraffine dropped in between them will hold them together.
Rubber bands may be used also, or, if but one end is to be experimented
with, the points may be stuck into a cork, and the heads used to do the
lifting.

APPARATUS 58.

_77. Small Horseshoe Magnets_ may be made from needles or from other
pieces of steel used for bar magnets. They should be annealed (App. 21)
at their centers at least, so that you can bend them into the desired
shape. In the case of bright needles, like harness-needles, the part
annealed will become blackened. If you heat the center only, and the
ends remain bright for about 1/2 inch, you will not need to harden the
needle again. It is an advantage to have the center of the magnet a
little soft, as it is not then liable to break. The ends alone may be
hardened by holding the bent portion away from the candle or gas flame,
while heating the ends. The bent steel should be magnetized by drawing
its ends across the poles of a horseshoe magnet.

APPARATUS 59.

_78. Flexible Horseshoe Magnets_ may be made of thin spring steel. The
distance between the poles can be regulated at will by bending the steel
more or less. The poles may be held at any desired distance apart by
thread or wire, which should be wound around the legs of the magnet a
little above the poles. This will keep the steel from straightening out.

APPARATUS 60.

_79. Horseshoe Magnet._ Fig. 36 and 37. Magnetize two harness-needles,
and stick them into a cork so that the poles shall be arranged as shown.
The distance between the poles can be regulated to suit. This forms a
very simple and efficient magnet, with the advantages of a real
horseshoe magnet.

[Illustration: Fig. 36.]

[Illustration: Fig. 37.]

APPARATUS 61.

_80. Armatures._ All home-made magnets should be provided with
armatures, or keepers. These are made of soft iron on the regular
magnets, and tend to keep the magnet strong. (See text-book.) For the
bar magnets described, a piece of sheet-tin, upon which to lay them, is
all that is needed for an armature. The lines of force will pass through
this. For the horseshoe magnets described, strips of tin, soft iron
wires, or even a wire