We now come to the greatest of all ghost-shows, that of the Polytechnic Institute, London. In the year 1863 letters patent {93} were granted to Professor John Henry Pepper, professor of chemistry in the London Polytechnic Institute, and Henry Dircks, civil engineer, for a device “for projecting images of living persons in the air.” Here were no concave mirrors, no magic lanterns, simply a large sheet of unsilvered glass. The effect is founded on a well-known optical illusion. “In the evening carry a lighted candle to the window and you will see reflected in the pane, not only the image of the candle, but that of your hand and face as well. A sheet of glass, inclined at a certain angle, is placed on a stage between the actors and spectators. Beneath the stage and just in front of the glass, is a person robed in a white shroud, and illuminated by the brilliant rays of the electric or the oxy-hydrogen light. The image of the actor who plays the part of spectre, being reflected by the glass, becomes visible to the spectators, and stands, apparently, just as far behind the glass as its prototype is placed in front of it. This image is only visible to the audience. The actor who is on the stage sees nothing of it, and in order that he may not strike at random in his attacks on the spectre, it is necessary to mark beforehand on the boards the particular spot at which, to the eyes of the audience, the phantom will appear. Care must be taken to have the theatre darkened and the stage very dimly lighted.” At the Polytechnic Institute the ghost was admirably produced. The stage represented the room of a mediaeval student who was engaged in burning the midnight oil. Looking up from his black-letter tome he beheld the apparition of a skeleton. Resenting the intrusion he arose from his chair, seized a sword which was ready to his hand, and aimed a blow at the figure, which vanished, only to return again and again. The assistant who manipulated the spectre wore a cover of black velvet. He held the real skeleton in his arms, and made the fleshless bones assume the most grotesque attitudes. He had evidently studied Holbein’s “Dance of Death.” The lower part of the skeleton, from the pelvis downward, was dressed in white linen, presumably a shroud. To the audience the figure seemed to vanish and reappear through the floor. {94} This ghost-making apparatus has been used with splendid success in the dramatizations of Dickens’ _Christmas Carol_ and _Haunted Man_; Bulwer’s _Strange Story_; and Alexander Dumas’ _Corsican Brothers_.