Applying ice or cold water to the nail heads
will reverse the current.
--Contributed by A. C. A., Chicago.
** How to Discharge a Toy Cannon by Electricity [59]
A device for discharging a toy cannon by electricity can be easily
made by using three or four dry batteries, a switch and a small
induction coil
[Illustration: Electrical Attachment for Discharging Toy Cannon]
capable of giving a 1/8-in. spark. Fasten a piece of wood, A, to
the cannon, by means of machine screws or, if there are no
trunnions on the cannon, the wood may be made in the shape of a
ring and slipped on over the muzzle. The fuse hole of the cannon
is counterbored as shown and a small hole is drilled at one side
to receive a small piece of copper wire, E. The wood screw, C,
nearly touches E and is connected to one binding post of the
induction coil. The other binding post is connected with the wood
screw, D, which conducts the current into the cannon, and also
holds the pieces of wood, A and B, in position.
When the cannon is loaded, a small quantity of powder is placed in
the counterbore, and the spark between C and E ignites this and
discharges the cannon.
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