Slade, Henry
An Encyclopaedia of Occultism (1920)
An American medium, principally known in connection with his slate-writing exploits. He came to Britain in July, 1876, and was cordially received by the leading spiritualists. Very many people were impressed and completely mystified by the phenomena they witnessed at his séances, and Lord Rayleigh, at a meeting of the British Association in September, 1876, stated that he had attended a séance of Slade's in the company of a professional conjurer, and that the latter had failed entirely to find an explanation of the facts. A few days after this emphatic testimony was given, however, Professor Ray Lankester published in a letter to the Times the result of a séance at which he and Dr. Donkin were present. He had, he said, snatched the slate prematurely from "Dr." Slade's hand, and had found a message written thereon, though the sound of writing had not then been heard. The spiritualists maintained that the exposure" was no exposure at all, since Slade declared that he had heard the spirits writing, and. Z had mentioned the fact, but that his voice had been lost in the confusion. However, the medium's career in Britain was at an end. At the instance of Professor Lankester he was tried in a court of law, and sentenced to three months imprisonment with hard labour. He appealed, and the conviction was quashed because of a slight omission in the charge. A fresh summons was issued on the following.day, but Slade had left the country, and did not thereafter return. In the years 1877-88 Professor Zöllner of Leipsic investigated the slate-writing and other phenomena occurring in the presence of Slade, mainly in the hope of establishing his theory of four-dimensional space. Knots were tied in endless cords, coins extracted from sealed boxes; but Professor Zöllner did not succeed in his attempt to have knots tied in a piece of bladder, or to have two rings of solid wood interlaced. In short, no really conclusive proof was obtained. In 1884 Slade's phenomena was investigated by a committee appointed by the University of Pennsylvania. The results of the latter investigation were, at the best, of a negative description. (See also Slate-writing .)
What Has Changed in the Last Century
The narrative in the 1920 Encyclopaedia of Occultism is still the standard one, but the question it leaves open — that "no really conclusive proof was obtained" — is now regarded as settled against Slade. The Seybert Commission at the University of Pennsylvania, whose "negative" findings are noted here, published its report in 1887 concluding the slate-writing was trickery, and stage magicians later set out the methods in detail, notably David P. Abbott in Behind the Scenes with the Mediums (1907) and Harry Houdini in A Magician Among the Spirits (1924); no modern historian treats slate-writing as anything but conjuring. Slade himself, who the entry says never returned to Britain, died in the United States in 1905. Zöllner's use of Slade to prove four-dimensional space is now a textbook example of how a competent physicist can be deceived rather than evidence of anything about geometry.
Written for this edition, 2026.