Of course any number of "fake" explanations are given by the showman who always manages to keep up with the times and exploit the latest mystery. At one time it was psychic force, then Roentgen or X-rays; lately it has been attributed to the mysterious effects of radium!
This illustration is more properly a delusion; there is no illusion about it.
CURIOUS ARITHMETICAL PROBLEMS
THE CHESS-BOARD PROBLEM
n Arabian author, Al Sephadi, relates the following curious anecdote: