that N can pass up and down in it when D is raised
and lowered. The rod, D, rests upon A, one of the contacts. This is a
straight piece of tin, cut as shown in Fig. 17, the narrow part being
1/4 in. wide and 1-1/4 in. long. The wide part is 3/4 in. wide and 1 in.
long. The other contact, B, is the same size as A. A deep groove, a
little over 1/4 in. wide, is cut into the base so that the narrow part
of B can be bent down below the end of A. The base shown is 4 x 2-1/2 x
7/8 in. The spool, C, is fastened to the base by 2 screws or wire nails
put up through the base, their positions being shown by the dots at E,
Fig. 17. X and Y, Fig. 18, are 2 screw binding-posts. It is evident that
the current cannot pass from X to Y, unless the button, D, be pressed
down so that the end of A will touch B.

APPARATUS 32.

_48. Sifter for Iron Filings._ Fig. 20. In making magnetic figures with
iron filings, it is an advantage to have the particles of iron fairly
small and uniform in size. A simple sifter may be made by pricking holes
in the bottom of a pasteboard pill-box with a pin. The sifter may be put
away with the filings in it, provided you turn it upside down.

[Illustration: Fig. 20.]

APPARATUS 33.

_49. Sifter for Iron Filings._ Fig. 21. Punch small holes in the cover
of a tin box with a small wire nail. If you have occasion to use sifters
for other purposes, the different sizes can be made by using larger and
smaller nails to punch the different tin covers. But one size of nail
should be used for one sifter.

[Illustration: Fig. 21.]

APPARATUS 34.

_50. Sifters_ may be made by pricking holes in an envelope. A sifter
with very small holes can be made of a piece of muslin cloth. This can
be used in the form of a little bag, or a piece of it can be pasted over
the open bottom of a pill-box.

APPARATUS 35.

_51. To Cut Wires, Nails, etc._ If you have no wire-cutters, or large
shears, you can cut large or small wires by hammering them against the
sharp edge of another hammer, an anvil, or a piece of iron. Do not let
the hammer itself hit upon the edge of the anvil. The above process will
make a V-shaped dent on one side of even large wires, or nails, when
they may be broken by bending back and forth.

CHAPTER IV.

SWITCHES AND CUT-OUTS.

_52. Switches, Cut-Outs._ Where apparatus is to be used frequently, such
as for telephone and telegraph lines, it pays to make your switches,
etc., carefully. Th