An old key is filed down in the shape shown in Fig. 2 to fit
the two holes.
As the dial is convex it will need protection to prevent injury by
rough handling. A leather shield may be used for this purpose,
which is cut with two holes, one for the key and the other to
permit the operator to observe the numbers on the dial. The shield
answers a further purpose of preventing any bystander from noting
the numbers on the dial.
** AN ELECTRIC ILLUSION BOX [135]
The accompanying engravings show a most interesting form of
electrically operated illusion consisting of a box divided
diagonally and each division alternately lighted with an electric
lamp. By means of an automatic thermostat arranged in the lamp
circuit causing the lamps to light successively, an aquarium
apparently without fish one moment is in the next instant swarming
with live gold fish; an empty vase viewed through the opening in
the box suddenly is filled with flowers, or an empty cigar box is
seen and immediately is filled with cigars.
These electric magic boxes as shown are made of metal and oxidized
copper finished, but for ordinary use they can be made of wood in
the same shape and size.
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