If it is desired to place the box
lower down, other angles for the image and glass may be found
necessary, but the proper tilt can be found readily by experiment.
The electric connections are so simple that they are not shown in
the drawings. All that is necessary is a two-point switch, by
which either L or M can be placed in circuit with the battery, and
a press button in circuit with the bell and its cell.
If a gradual transformation is desired, a double-pointed rheostat
could be used, so that as one light dims the other increases in
brilliancy, by the insertion and removal of resistance coils.
With a clear glass and a dark room this model has proved to be
fully as bewildering as its prototype.
** Experiment with Colored Electric Lamps [53]
To many the following experiment may be much more easily performed
than explained: Place the hand or other object in the light coming
from two incandescent lamps, one red and
[Illustration: Two-Colored Hand]
one white, placed about a foot apart, and allow the shadow to fall
on a white screen such as a table-cloth. Portions of the shadow
will then appear to be a bright green.
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