The successful conjurer has carefully studied beforehand every movement that is made--every word that is spoken--during a conjuring performance, and has seen that these all fit naturally into place, and help conceal the real workings of the trick. The right and left hands must be trained to operate independently, and without the need of looking at either. Many conjurers practice doing two separate things at the same time, one with either hand; and the ability to do this is essential. Above all, the performer must be full of conscious self-possession, and feel himself to be master of the situation, no less than to feel the ability to cope with any emergencies that may arise. Turning, now, to a consideration of the seance, we find that many of these psychological rules still hold good, and their operation enables the medium to perform many actions which would otherwise be impossible. A certain suggestion is given to the sitters, and imagination and inference do the rest. "Our conclusions as to what we see or hear are always founded on a combination of observation and inference; but in daily life it is seldom necessary to distinguish between the two elements, since, when the object and its mode of presentation are familiar, our inferences are generally correct. But it is different when, owing to circumstances, such as a bad light, we have to infer more in proportion to what we perceive than usual; or when some one, e. g., a conjurer or a ventriloquist, is trying to deceive us by presenting one object under the familiar aspect of another, and suggesting false inferences. It is not uncommon to find people at seances encouraging each other in the belief that they see, say, a living human figure, when all that they actually SEE is something moving which is about the size of a human being; the rest is inference." How true these last remarks are is demonstrated by the statement, made in The Revelations of a Spirit Medium, that an old wire mask frequently used at materializing seances had been recognized "by dozens of persons as fathers, mothers, sisters, brothers, cousins, sweethearts, wives, husbands, and various other relatives and friends. None but the medium knew that it was only a fifty-cent wire mask, hence none but the medium could enjoy the humor of the occasion."