On the return of Sir Donkin it was arranged that he and Sir Lankester should attend a seance together and that Sir Donkin was to watch for the “suspicious move” and when he saw it signal Sir Lankester. Everything worked as planned. On receiving the agreed signal from Donkin, Lankester seized the slate containing the finished message proving that a skillful exchange of slates had been made by Slade and this was the real evidence which caused the downfall of Henry Slade in England.

Blocked in Paris from working his tricks because of the publication of an account of his exposure in England Slade seems to have gone to Germany for it was during the next year, 1877, that he so successfully deluded Professor Zollner. “Zollner” is one of the names on which Spiritualistic enthusiasts bank most heavily for proof of their claims. Even Sir Arthur Conan Doyle to this day quotes Zollner as indisputable authority. Nevertheless Zollner is discredited by Mr. George S. Fullerton, Secretary of the Seybert Commission. While in Germany Mr. Fullerton made a special business of investigating the value of this Zollner endorsement, and at the time all of the men who participated in the Slade investigation were alive with the exception of Zollner himself. Mr. Fullerton in the summary of his report to the Commission said:

“Thus it would appear that of the four eminent men whose names have made famous the investigation, there is reason to believe one, Zollner, was of unsound mind at the time, and anxious for experimental verification of an already accepted hypothesis; another, Fechner, was partially blind and believed because of Zollner’s observation; a third, Scheibner, was also afflicted with defective vision and not entirely satisfied in his own mind with the phenomena; and a fourth, Weber, was advanced in age, and did not even recognize the disabilities of his associates. None of the men named had any previous experience or knowledge of the possibilities of deception.”

The Seybert Commission, in 1884, seems to have made the first systematic, organized effort to fathom the so-called phenomena of Spiritualism, and this Commission sent for Slade, who was then operating in New York, and had him give a number of seances under their observation, but in spite of the fact that Slade gave the Commission a personal letter thanking them for their courtesies and expressing his willingness to sit with them again, the Commission considered his work fraudulent throughout.

At a very early stage of the sittings, the Commission noticed two kinds of communications. Those in answer to questions were slovenly written, often illegible, while those which came as voluntary contributions from the Spirits, were more carefully written, even to punctuation. It was very evident that this writing on the slates had been prepared previous to the sitting, while that written under the restraint of observation was the crude scrawl, abrupt in composition, and often almost or quite illegible. It was evident that where the nicely written communications were used an exchange of slates had been effected, whereas the other writing was the result of such skill as could be brought to bear without detection under the unfavorable conditions. It was also noticed that all of the long messages most suspiciously resembled the handwriting of the medium. Every test to which Slade submitted proved to be transparent to the Commission and some of his efforts to mystify it were referred to as:

“Several little tricks which he imputed to Spiritual agency, but which were almost puerile in the simplicity of their legerdemain, and which have been repeated with perfect success by one of our number.”

After all the slate-writing mediums who came in answer to an advertisement broadcasted by the Seybert Commission had been examined by it, the acting Chairman of the Commission, Mr. Horace Howard Furness, invited the late Harry Kellar to exhibit his slate-writing skill before it, not with any claim to supernatural phenomena but as a magician openly admitting his purpose to baffle by purely natural means. Mr. Kellar submitted to a series of tests far more complicated and difficult of execution than any produced by Slade or any other medium; nevertheless the Commission was unable to detect his methods and admitted itself completely baffled.

Mr. Kellar told me that when Mr. Furness, and Coleman Sellers, another member of the Commission who was himself an amateur entertainer, applied to him for an exhibition of his skill as a slate-writer they expected him to do the stock tricks of Slade. But someone tipped Kellar off that Sellers had told the members of the Commission what Kellar was to do and his probable method of doing it and for them to watch out for his modus operandi. So, not to be “caught napping,” Kellar, like the skillful mystifier that he was, determined to out-do Slade and beat Sellers. As he told me about it he laughed heartily, saying:

“If you could have seen Mr. Sellers’ face at the time of the unfolding of the mystery, it would have done your heart good.”

When Kellar arrived for the demonstration he insisted that the Commission furnish its own slates, so a boy was sent out who brought back about a dozen of various kinds. Then all sat down around the table with hands resting, palm down, on its top. The Commission opened the sitting by writing questions on the slates. Kellar held them under the table with the thumb on top and when he withdrew them in a few moments they had answers to the questions written in a clear round hand. The questions gradually became longer and longer, but the replies kept pace with them, sometimes covering a whole side of the slate. Although the slates were all different and could not possibly be mistaken for one another, the Commission began to put identifying marks on them. Once no pencil was put on the top of the slate but the reply came just the same. This fact was commented upon and Kellar replied: