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Houdini’s Impossible Demonstration

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Notes on a Strange World

Massimo Polidoro

Skeptical Inquirer Volume 30.4, July / August 2006

For a few years, magician Harry Houdini and British writer Sir Arthur Conan Doyle, creator of the Sherlock Holmes stories, were friends. One was an arch-skeptic (Houdini), while the other was a true believer in Spiritualism (Doyle).

Possibly hoping to show Doyle how easy it is to be fooled by mediums, Houdini once gave his friend an extraordinary demonstration, in his own home, in the presence of Bernard M.L. Ernst, Houdini’s friend and lawyer. Ernst’s memoirs reveal what happened that night.

Mene, mene, tekel upharsin

Houdini produced what appeared to be an ordinary slate, some eighteen inches long by fifteen inches high. In two corners of this slate, holes had been bored, and through these holes wires had been passed. These wires were several feet in length, and hooks had been fastened to the other ends of the wires. The only other accessories were four small cork balls (about three-quarters of an inch in diameter), a large ink-well filled with white ink, and a table-spoon.

Houdini passed the slate to Sir Arthur for examination. He was then requested to suspend the slate in the middle of the room, by means of the wires and hooks, leaving it free to swing in space, several feet distant from anything. In order to eliminate the possibility of electrical connections of any kind, Sir Arthur was asked to fasten the hooks over anything in the room which would hold them. He hooked one over the edge of a picture-frame, and the other on a large book, on a shelf in Houdini’s library. The slate thus swung free in space, in the center of the room, being supported by the two wires passing through the holes in its upper corners. The slate was inspected and cleaned.

Houdini now invited Sir Arthur to examine the four cork balls in the saucer. He was told to select any one he liked, and, to show that they were free from preparation, to cut it in two with his knife, thus verifying the fact that they were merely solid cork balls. This was accordingly done. Another ball was then selected, and, by means of the spoon, was placed in the white ink, where it was thoroughly stirred round and round, until its surface was equally coated with the liquid. It was then left in the ink to soak up as much liquid as possible. The remaining balls Sir Arthur took away with him for examination, at Houdini’s request.

“Have you a piece of paper in your pocket upon which you can write something?” asked Houdini to Doyle. He had a pencil.

“Sir Arthur,” continued Houdini, “I want you to go out of the house, walk anywhere you like, as far as you like in any direction; then write a question or sentence on that piece of paper; put it back in your pocket and return to the house.”

Doyle obeyed, walking three blocks and turning a corner before he wrote upon the paper. When he returned Houdini invited him to take a spoon and remove the cork ball, which had been soaking in the white ink, then to touch the ball to the left side of the slate. The ball “stuck” there, seemingly of its own volition. Slowly, it began rolling across the surface of the slate, leaving a white track as it did so. As the ball rolled, it was seen to be spelling the words: “Mene, mene, tekel upharsin,” the very same words that Doyle had written. The guests were speechless.

Houdini turned to Doyle and said: “Sir Arthur, I have devoted a lot of time and thought to this illusion; I have been working at it, on and off, all winter. I won't tell you how it was done, but I can assure you it was pure trickery. I did it by perfectly normal means. I devised it to show you what can be done along these lines. Now, I beg of you, Sir Arthur, do not jump to the conclusion that certain things you see are necessarily 'supernatural,' or the work of 'spirits,' just because you cannot explain them. This is as marvelous a demonstration as you have ever witnessed, given you under test conditions, and I can assure you that it was accomplished by trickery and by nothing else. Do, therefore, be careful in future, in endorsing phenomena just because you cannot explain them. I have given you this test to impress upon you the necessity of caution, and I sincerely hope that you will profit by it.”

“Sir Arthur,” remembered Ernst, “came to the conclusion that Houdini really accomplished the feat by psychic aid, and could not be persuaded otherwise.” Doyle’s reaction, and the refusal to consider trickery even when admitted by the trickster, was so typical, noted Houdini, that “here is little wonder in his believing in Spiritualism so implicitly.”

Berol’s Secret

The secret of the trick remained a mystery for years until magician and historian Milbourne Christopher revealed it in his book Houdini, A Pictorial Life. “Neither Doyle nor Ernst,” wrote Christopher, “could fathom this mystery. They might have been less startled had they seen Houdini’s friend Max Berol perform in Vaudeville.” Berol had been performing for years, both in Europe and America, an act in which a ball dipped in ink would spell on an isolated board the words called out by members of the audience:

“Berol did this by switching a solid cork ball for one with an iron core. A magnet at the end of a rod, manipulated by an assistant concealed behind the board, caused the ball to adhere and move-apparently under its own power. After Berol retired, Houdini purchased the equipment. An assistant in the room adjacent to Houdini’s library had opened a small panel in the wall and extended the rod with a magnet through it. The ball on the slate had an iron center, of course.

“Ernst had not remembered that when Doyle returned to the room, after writing the words outdoors, Houdini had checked to make sure the slip of paper on which Doyle wrote was folded, then immediately returned it to his friend. Before doing so, the magician had switched slips. While Doyle was busy retrieving the ball from the inkwell and taking it to the board, Houdini read the words. His conversation cued his hidden assistant. Once the message had been written on the slate, Houdini asked Doyle for the folded slip to verify his words. He opened the blank paper, pretended to read from it, then switched it for the original as he returned the paper to his friend. Later, Houdini explained this switching process during his public lectures on fraudulent mediums.”

Massimo Polidoro

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Massimo Polidoro is an investigator of the paranormal, author, lecturer, and co-founder and head of CICAP, the Italian skeptics group. His website is at