"The sources of error," says Dr. Max Dessoir, in an article reproduced in the "Open Court," "through which such strange reports arise, may be arranged in four groups. First, the observer interpolates a fact which did not happen, but which he is led to believe has happened; thus, he imagines he has examined the slate when as a fact he never has. Second, he confuses two similar ideas; he thinks he has carefully examined the slate, when in reality he has only done so hastily, or in ignorance of the point at issue. Third, the witness changes the order of events a little in consequence of a very natural deception of memory; he believes he tested the slate later than he actually did. Fourth and last, he passes over certain details which were purposely described to him as insignificant; he does not notice that the 'medium' asks him to close a window, and that the trick is thus rendered possible." Similar experiments in slate-writing were conducted by the Seybert Commission with Mr. Harry Kellar, the conjurer, after sittings were had with Dr. Slade, and the magician outdid the medium. The Seybert Commission found none of Slade's tests genuine, and officially denied "the extraordinary stories of his performances with locked slates which constitute a large part of his fame." Dr. Slade began his Spiritualistic operations in London in the year 1876, and charged a fee of a guinea a head for séances lasting a few minutes. Crowds went to see him and he reaped a golden harvest from the credulous, until the grand fiasco came. Slade was caught in one of his juggling séances and exposed by Prof. Lancaster and Dr. Donkin. The result was a criminal prosecution and a sensational trial lasting three days at the Bow Street Police Court. Mr. Maskelyne, the conjurer, was summoned as an expert witness and performed a number of the medium's tricks in the witness box. The court sentenced Slade to three months' hard labor, but he took an appeal from the magistrate's decision. The appeal was sustained on the ground of a technical flaw in the indictment, and the medium fled to the Continent before new summons could be served. He visited Paris, Leipsic, Berlin, St. Petersburg and other cities, giving séances before Royalty and before distinguished members of scientific societies; and afterwards went to Australia. He made money fast and spent it fast, but it took all of his ingenuity to elude the clutches of the police. In 1892, we find him the inmate of a workhouse in one of our Western towns, penniless, friendless and a lunatic. Slade's séances with Prof. Zoellner, of Berlin, in 1878, attracted wide attention, and did more to advertise his fame as a medium than anything else in his career.