While the performance of magical tricks is an art, the observation of them and also their description is a science, presupposing a quick and critical eye, of which very few people are possessed; and scientists by profession are sometimes the least fit persons to detect the place and mode of the deception. How differently different persons watch the same events becomes apparent when we compare Professor Zöllner’s reports of spiritualistic séances with those of other more critical witnesses. Professor Zöllner, for instance, writes (_Wissenschaftliche Abhandl._, Vol. III, p. 354) in his description of one of the experiments with the famous American medium, Dr. Slade, that Professor Fechner’s chair was lifted up about half a foot above the ground, while Dr. Slade touched the back of it lightly with his hand, and he emphasizes that his colleague, after hovering some time in the air, was suddenly dropped with great noise. The event as thus described is mystifying. However, when we carefully compare Professor Fechner’s account, we come to the conclusion that the whole proceeding is no longer miraculous, but could be repeated by prestidigitateurs. Fechner writes that at the request of Dr. Slade, he himself (Professor Fechner), who was slim and light, took the place of Professor Braune. Dr. Slade turned round to Professor Fechner and bore his chair upward in a way which is not at all inexplicable by the methods of legerdemain. Professor Fechner does not mention that he hovered for some time in the air, but it is obvious that Dr. Slade {xxv} made the two professors change seats because he would scarcely have had the strength to lift up the heavy Professor Braune. [Illustration: PROFESSOR ZÖLLNER AND DR. SLADE. (From Willmann.)] Similarly, the accounts of the famous painter, Gabriel Max, who also attended some of Slade’s séances with Zöllner, make the performances of the medium appear in a less wonderful light. {xxvi} Mr. Carl Willmann, a manufacturer of magical apparatus at Hamburg, and the author of several books on modern magic, publishes a circumstantial description of Professor Zöllner’s double slates used in séances with Dr. Slade, which are now in possession of Dr. Borcherdt of Hamburg, who bought them, with other objects of interest, from the estate of the deceased Professor Zöllner. The seals of these slates are by no means so intact as not to arouse the suspicion that they have been tampered with. To a superficial inspection they appear unbroken, but the sealing wax shows vestiges of finger marks, and Mr. Willmann has not the slightest doubt that the slates were opened underneath the seals with a thin heated wire, and that the seals were afterwards replaced. [Illustration: THE OPENING OF SLADE’S SLATE BY MEANS OF A HEATED WIRE. (After Willmann.)]