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three positions, one being "off," one for battery and the other for the mag- neto or second set of batteries. If but one set of batteries was used, or if the magneto was used without batteries, it will be necessary only to use a switch having two terminals, one "on" and one "off." The switch selected should be fastened to the dash or to the box containing the master coil, previously described.

The system is then ready for wiring. A good grade of primary wire should be used, and the connections should be made with regular brass or cop- per wire terminals soldered on. The switch originally used on the coil case should be placed in one of the positions formerly used for running and al- lowed to remain there permanently.

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��Wiring diagram showing connections for master vibrator

If the position selected is on the "mag- neto" side, the following connection will be made to the terminal which formerly ran to the magneto ; if on the "battery" side, to the connection which ran to the battery. This terminal, either battery or magneto, should now be con- nected to either terminal on the master coil.

If a switch having but two terminals was used, the remaining connection from the master coil should be con- nected to either switch terminal. If a switch having three terminals was used, this connection from the master

��coil will be made to the common ter- minal on the switch. This common terminal is the one that completes a circuit through either of the other switch terminals, depending on which way the switch is thrown.

If the switch having but two termin- als is in use, connect the unused ter- minal to the battery or magneto through the wire which formerly ran to the coil on the car. If the three- terminal switch is used, run a wire from the terminal that completes a circuit when in the "battery" position to the battery, and run another wire from the terminal that completes the circuit when in the "magneto" posi- tion to the magneto. This can be ac- complished by attaching the wires that formerly ran to the car-coil terminals to the new switch terminals.

Provided the connections have been made as directed and other wires have not been disturbed, the system is ready to operate when the master vibrator has been properly adjusted. This is done by turning the adjusting screw until the contacts are seen to sepa- rate. The screw is then turned in the opposite direction until the contacts just come together. Turn the starting crank or flywheel with the new switch in the "battery" position until the vi- brator is heard to buzz; then turn the switch of¥ without moving the fly- wheel out of this position. The vi- brator may be adjusted by removing a spark plug wire about Vx'' from the plug and again turning on the switch. Turn the adjusting screw one way or the other until a good strong spark is secured, replace the spark plug wire and start the engine as usual.

Cutting Brass

WITH a quill pin dipped in a strong solution of alcoholic corrosive sublimate, draw a line on the brass. Set it dry and then go over it with the pen dipped in nitric acid. The metal may then be broken like glass cut with a diamond. — John Schmelzeis.

��If you want further information about the subjects which are taken up in the Popular Science Monthly, write to our Readers' Service Department. We will gladly furnish free of charge names of manufacturers of devices described and illustrated.

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