. To harden steel, heat as before, then suddenly plunge the red-hot
piece into cold water. This will make the steel very hard and brittle.

Small pieces may be held by pinching them between two pieces of wood.
Needles and wires may be stuck in a cork, which will serve as a handle.
(See text-book.)

APPARATUS 22.

[Illustration: Fig. 11.]

_37. Alcohol Lamp._ Fig. 11. An alcohol lamp is very useful in many
experiments, and it is better than a candle for annealing or hardening
steel needles when making small magnets (App. 21). You can make a good
lamp by using a small bottle with a wide opening. A vaseline bottle or
even an ink bottle will do. Make a hole about 1/4 in. in diameter
through the cork with a small round file, or burn it through with a hot
nail. Make a cylinder of tin about 1-1/2 in. long and just large enough
to push through the hole. The tin may be simply rolled up. If you have
glass tubing, use a short length of that instead of the tin. For the
wick, roll up some flannel cloth. This should not fit the inside of the
tin tube too tightly. The alcohol should be put into the lamp when you
want to use it, and that left should be put back into the supply-bottle
when you have finished, as alcohol evaporates very rapidly. The flame of
this lamp is light-blue in color, and very hot.

Caution. Do not have your supply-bottle of alcohol near the lamp when
you light the latter, or near any other flame. The vapor of alcohol is
explosive.

APPARATUS 23.

_38. Spool Holder for Wire._ Fig. 12. When winding magnets it is
necessary to have the spool of wire so arranged that it will take care
of itself and not interfere with the winding. If you have a brace and
bit, bore a hole in a base 7/8 in. thick for a 1/4 in. dowel. The dowel
should fit the hole tight. The spools of wire purchased can then be
placed upon the dowel, where they will unwind evenly. The base may be
nailed or clamped to a table.

[Illustration: Fig. 12.]

APPARATUS 24.

_39. Spool Holder for Wire._ If you have no brace and bit to make App.
23, nail a spool to a wooden base, place a short length of dowel in the
spool, and use this combination as a spool holder. Make the dowel fit
the spool by winding paper around it.

APPARATUS 25.

_40. To Make Holes in Wood._ If you have a brace and a set of bits, or
even a small hand-drill, it will be an easy matter to bore holes in
wood. An awl should be used to make holes for screws, such as those