ll. Fasten a metal strip, 3/4 in. x 1-1/4 in., to the apparatus
by means of a screw. The apparatus wire should be fastened under the
screw-head. A short length of spring may be pushed upon the upright part
of the strip, as shown. Into this you can quickly fasten the outside
wires.

APPARATUS 45.

_63. Binding-Post._ Fig. 30. This makes a very simple and practical
binding-post for home-made apparatus. It consists of a screw-eye,
preferably of brass. The circle or eye should be about 3/8 or 1/2 in. in
diameter. The thread on such a screw-eye will be about 1/2 in. long. Two
copper burs are used to pinch the wires.

APPARATUS 46.

_64. Binding-Post._ Fig. 31. This consists of a screw, screw-eye, bur
and a metal strip, 3/4 x 1-1/4 in. The apparatus wire should be fastened
under the screw-head. Any outside wires which are to be joined to the
apparatus should be clamped under the bur by turning the screw-eye. A
small hole should be made in the wood before putting in the screw-eye.
(See App. 25.) Do not turn the screw-eye too hard, or you will spoil the
thread made in the wood.

[Illustration: Fig. 30.]

[Illustration: Fig. 31.]

[Illustration: Fig. 32.]

APPARATUS 47.

_65. Binding-Post._ Fig. 32. The size of the bolt used in this form of
binding-post will depend somewhat upon the thickness of the base of the
apparatus. In general, a 3/4 or 7/8 in. base should be used where screws
or screw-eyes are necessary. With this kind (Fig. 32) a thin base can
be used. The head is shown counter-sunk into the bottom of the base.
This is not necessary, provided at least 3 heads are placed far enough
apart to form legs for the apparatus to stand on. Strips of wood may be
nailed upon the underside of the base to make room for the heads in case
they are not used as legs. The wires should be pinched between the nut
and the copper bur shown. If the bolt is too large for a bur, an iron
washer may be used. A washer may be made of tin, or two nuts may be
used.

APPARATUS 48.

_66. Binding-Post._ Fig. 33. This is a suggestion for a combination of
App. 44 and 47. It is useful in school apparatus. Wires may be
permanently fastened on the right, under the nut, and a spring, as in
App. 44, may be slipped on the metal strip at the left, which is held
under the head of the bolt.

[Illustration: Fig. 33.]

APPARATUS 49.

_67. Mercury Connector._ A cup of mercury may be used as a connector.
Make a small hole about 1/4 in. in