asten on the switch lever, as
at A and B, Fig. 2, so that it can rotate about these points.
Connect the wires as shown in Fig. 3. To reverse, throw

[Illustration: Simple Current-Reversing Switch]

the lever from one end of the block to the other.
--Contributed by R. L. Thomas, San Marcos, Tex.

** Novel Mousetrap [112]

A piece of an old bicycle tire and a glass fruit jar are the only
materials required for making this trap. Push one end of the tire
into the hole, making sure that there is a space left at the end
so that the mice can get in. Then

[Illustration: A Baitless Trap]

bend the other end down into a fruit jar or other glass jar. Bait
may be placed in the jar if desired, although this is not
necessary.
--Contributed by Geo. Go McVicker, North Bend, Neb.

** Polishing Nickel [112]

A brilliant polish may be given to tarnished nickel by immersing
in alcohol and 2 per cent of sulphuric acid from 5 to 15 seconds.
Take out, wash in running water, rinse in alcohol, and rub dry
with linen cloth.

** Homemade Arc Light [112]

By rewinding an electric-bell magnet with No. 16 wire and
connecting it in series with two electric-light carbons, as shown
in the sketch, a small arc will be formed between the carbon
points when the current is applied. In the sketch, A is the
electric-bell magnet; B, the armature; C C, carbon sockets; D,
carbons, and E E, binding posts. When connected with 10 or 12 dry
batteries this lamp gives a fairly good light.
--Contributed by Morris L. Levy, San Antonio, Tex.

[Illustration: Arc Light]

** Lighting an Incandescent Lamp with an Induction Coil [112]

An incandescent lamp of low candlepower may be illuminated by
connecting to an induction coil in the manner shown in the sketch.
One wire is connected to the metal cap of the lamp and the other
wire is fastened to the glass tip. If the apparatus is then placed
in the dark and the current turned on, a peculiar phosphorescent
glow will fill the whole interior of the lamp. The induction coil
used for this purpose should give a spark about 1/2 in. long or
more.
--Contributed by Joseph B. Bell, Brooklyn.

[Illustration: Geissler Tube]

How to Make a Jump-Spark Coil [113]

The induction coil is probably the most popular piece of apparatus
in the electrical laboratory, and particularly is it popular
because of its use in experimental wireless telegraphy. Ten years
ago wireless telegraphy was a dream of scienti