APPARATUS 29.

_45. Push-Button._ Fig. 14. This is made quickly, and may be easily
fastened to the window or door-casing. One wire is joined to A and the
other to C. B is a strip of tin or other metal, about 5/8 in. wide and 2
in. long. It is bent so that it will not touch A unless it is pressed
down. This may be placed anywhere, in an electric-bell circuit or other
open circuit, where it is desired to let the current pass for a moment
only at a time.

[Illustration: Fig. 14.]

APPARATUS 30.

_46. Push-Button._ Fig. 15 and Fig. 16. By placing App. 29 in a box, we
can make something that looks a little more like a real push-button.
Fig. 15 shows a plan with the box-cover removed, and Fig. 16 shows a
view of the inside of it, a part of the box being cut away. C, Fig. 15,
is a wooden pill-box 1 in. high and 1-3/4 in. in diameter. Make a 1/4
in. hole in the cover of C for the "button," G, which is a short piece
of 1/4 in. dowel. This rests upon a single thickness of tin, D, which is
cut into a strip 3/8 in. wide and about 1-1/4 in. long. In the bottom of
C are two holes just large enough to allow the screws E and F to pass
through. The wires, A and B, pass from the binding-posts, X and Y,
through small holes burned through the sides of the box, and are
fastened under the screw-heads. The whole box is screwed to the wooden
base, which is 3 x 4 x 7/8 in., by the screws, E and F. D should have
enough spring in it to raise itself and G when the pressure of the
finger is removed. The circuit will be closed only when you press the
button.

[Illustration: Fig. 15.]

[Illustration: Fig. 16.]

APPARATUS 31.

_47. Push-Button._ Figs. 17, 18, 19. Fig. 17 shows a top view or plan of
the apparatus. Fig. 18 is a sectional view; that is, we suppose that the
button has been cut into two parts along its length and through the
center line. Fig. 19 is an enlarged detail drawing of the underside of
the spool, C. The same part is marked by the same letter in all of the
figures.

[Illustration: Fig. 17.]

[Illustration: Fig. 18.]

[Illustration: Fig. 19.]

Saw an ordinary spool, C, into two parts. One-half of C will serve as
the outside case for the button. The part to be pressed with the finger
is a short length of 1/4 in. dowel. To keep this from falling out of the
hole in C, a short piece of wire nail, N, has been put through a small
hole in its lower end. A slot, F, has been burned or cut into the
underside of C, so