, which is snatched swiftly away at the proper moment by
the assistant. Any article thrown into the cave and caught by the
black hand and concealed by a black cloth seems to disappear. Any
object not too large can be made to "levitate" by the same means.
A picture of anyone present may be made to change into a grinning
skeleton by suddenly screening it with a dropped curtain, while
another curtain is swiftly removed from over a pasteboard
skeleton, which can be made to dance either by strings, or by the
black veiled hand holding on to it from behind, and the skeleton
can change to a white cat.

But illusions suggest themselves. There is no end to the effects
which can be had from this simple apparatus, and if the operators
are sufficiently well drilled the result is truly remarkable to
the uninitiated. The illusion, as presented by Hermann, was
identical with this, only he, of course, had a big stage, and
people clothed in black to creep about and do his bidding, while
here the power behind the throne is but a black-veiled hand and
arm. It can be made even more complicated by having two
assistants, one on each side of the box, and this is the reason
why it was advised that two holes be cut. This enables an
absolutely instantaneous change as one uncovers the object at the
moment the second assistant covers and removes the other.

[Illustration: The Magic Cave]

It is important that the assistants remain invisible throughout,
and if portieres are impossible, a screen must be used. But any
boy ingenious enough to follow these simple instructions will not
need to be told that the whole success of the exhibition depends
upon the absolute failure of the audience to understand that there
is more than one concerned in bringing about the curious effects
which are seen. The exhibitor should be a boy who can talk; a good
"patter"--as the magicians call it--is often of more value than a
whole host of mechanical effects and helpers. It is essential that
the exhibitor and his confederate be well drilled, so that the
latter can produce the proper effects at the proper cue from the
former. Finally, never give an exhibition with the "cave" until
you have watched the illusions from the front yourself; so that
you can determine whether everything connected with the draping is
right, or whether some stray bit of light reveals what you wish to
conceal.

** Reversing-Switch for Electrical Experiments [92]

A homemade reversing-sw