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Rh proof that disinterested fraud of this kind may be practised by persons on whom the ordinary motives of pecuniary gain or notoriety can hardly be supposed to operate has been found of considerable value in interpreting some of the most puzzling problems of Spiritualism.

On the other hand, a series of careful investigations by some members of the Society has thrown valuable light on the nature of the psychological processes which facilitate deception at a spiritualistic séance. Accurate observation of the phenomena occurring at the ordinary séance is, indeed, rarely possible, because the sitting generally takes place in a subdued light; and, further, because many of the more striking phenomena occur impromptu, when the experimenter, not knowing what to expect, is not fully prepared for observation. But there was one particular manifestation which seemed to offer every facility for investigation,—the performance of writing on slates, as exhibited in England by the American medium, Slade, in 1876, and later by William Eglinton. The performance took place in daylight; it was fairly constant in its appearance, instances of completely unsuccessful séances being relatively rare; and from the nature of the exhibition the conditions presented, or seemed to present, the fullest opportunity for examination. A prominent Spiritualist wrote in 1886 of an exhibition by Eglinton: "The facts are of so simple a nature that they could as well be observed by any ordinary