The trick consisted of several parts. A trap-door was in the stage through which Joe could disappear. This trap, directly under the chair and paper, was operated by a theatre employee, who of course would not tell, at least beforehand, how the trick was done. After Joe had gone down through the trap, into the room that exists under all theatrical stages, it was an easy matter for him to slip out through the stage door, run around an alley, and enter the front of the theatre, to walk calmly down the aisle.
But how could he disappear through the seat of the chair, and through the sheet of paper, without making a break, at least in the paper?
There was a trick about the paper, although it seemed to be perfectly ordinary. It was a sheet from the local paper, but it had been prepared in advance by the professor. On the back was pasted a square of cardboard, a quarter of an inch smaller each way than the trap-door in the stage. This paper trap, for such it was, was divided in the middle, the two flaps being hinged to the sheet of newspaper. The reason the cardboard did not show when held up to the audience was that the whole sheet of newspaper was double, one half being folded over the cardboard trap.
When Professor Rosello laid the paper down in the stage he was guided by certain small marks, so that it went exactly over the trap in the floor. This trap was hinged at the back, opening downward, but kept in place when not in use by a strong iron bar underneath. Next he placed the chair over the piece of paper, the legs going into exact positions previously marked on the paper, but the marks were too small to be seen by the audience.
The object in placing the paper on the stage was to get the audience to believe that there was no hole in the wooden floor through which Joe could disappear, it being the natural inference that such was the method used. But when the crowd saw what they thought was the unbroken sheet of paper, they would not suppose Joe had gone down through that, as he really had.
The chair was also a trick one. The seat of it was on hidden hinges so it could be lifted up and folded back. There were also secret springs on it which, when released, shot out and extended certain thin steel projections, which distended the black sheet into such shape that they made the rough outline of a person sitting on the chair.
When Joe took his seat on the chair, under cover of the black cloth, he pressed the secret springs, and a ring appeared above his head to support the black cloth, exactly as if it were supported by his head. Other projections appeared at his knees, and as the bottom of the cloth was arranged by the professor some distance away from the legs of the chair, Joe was as if he were under a sort of tent, held out and away from him, so he could move about a little without being seen.
As soon as he was covered, and had worked the secret springs, he lifted up the false seat of the chair, supporting himself by his hands on the framework, into which the seat fitted.
This seat Joe carefully folded back, taking care to make no noise and not to disturb the black cloth all around him. Meanwhile the professor had with his foot given a rap on the floor of the stage. This was a signal to the man below to open the trap in the floor.
Joe, hidden under the black cloth, felt for the opening in the floor with his feet. A stepladder was hurriedly put into place by the stage-hand, and Joe lowered himself down through the chair, the prepared hole in the paper and the hole cut in the stage, to the ladder.