ss,
3/4 in. wide and 16 in. long, bent into an oblong shape and the
ends soldered or bolted together. If the ends are to be soldered,
before doing so drill four 1/4-in. holes 1 in. from the ends and
insert the ends of the axles. The other two pieces are 1/2-in.
wide and of the dimensions shown in the sketch. These pieces are
riveted in the middle of the oblong frame, each in its proper
place. The motor is now bolted, bottom side up, to the top of the
piece fastened to the frame lengthwise. A trolley, Fig. 3, is made
from a piece of clock spring, bent as shown, and a small piece of
tin soldered to the top end for a brush connection. A groove is
made in the tin to keep the trolley wire in place.

The trolley wire is fastened to supports made of wood and of the
dimensions given in Fig. 4. The trolley should be well insulated
from the frame. The parts, put together complete, are shown in
Fig. 5. Run a belt from the pulley on the motor to the grooved
wheel on the axle, as shown in Fig. 6, and the locomotive is ready
for running.

In making the connections the travel of the locomotive may be made
more complicated by placing a rheostat and controlling switches in
the line, so that the engine can be started and stopped at will
from a distance and the speed regulated. Automatic switches can be
attached at the ends of the line to break the circuit when the
locomotive passes a certain point.

One connection from the batteries is made to the trolley wire and
the other to a rail. The connection for the motor runs from one
binding post to the trolley and this connection must be well
insulated to avoid a short-circuit. The other binding-post is
connected to the frame.

The cost of making the wheels and purchasing the track will not be
over $1.50. The track can be made from strips of tin put in a saw
cut made in pieces of wood used for ties. This will save buying a
track.
--Contributed by Maurice E. Fuller, San Antonio, Texas.

** Demagnetizing a Watch [166]

A test can be made to know if your watch is magnetized by placing
a small compass on the side of the watch nearest the escapement
wheel if the compass pointer moves with the escapement wheel the
watch is magnetized. A magnetized watch must be placed in a

[Illustration: Watch Demagnetizer]

coil that has an alternating current of electricity flowing
through it to remove the magnetism. A demagnetizer can be made as
shown in the illustration. Two end pieces for the