Prepare a pasteboard circle, upon one side of which draw a figure of a
cage, and on the other side that of a rat. Near the outer edge of the
circle fasten two strings opposite each other. So that they may be held
between the fore finger and thumb in such manner that the circle may be
made to revolve rapidly. When it is set in motion the transition is so
quick, that it presents the appearance of a rat in the cage.
[Illustration]