"Well, that is unpleasant," muttered Frank; "but a fellow can't expect everything to come his way."
When he had finished dressing, he went up onto the stage to pack away the apparatus with which the "Educated Fly" trick had been performed.
The fly was placidly resting against the face of the mirror in the blank corner. Frank took it up and put it into the fake cage.
The fly was a perfect imitation of a real fly, but it was made of cork, and it had an iron core, which rested flat against the glass when everything was ready for the exhibition to begin.
In addition to a wooden back, the mirror had a cloth back, which was firmly fastened into the frame. The wooden back was hinged to the frame at the bottom, and was very strong.
When the frame was placed on the easel and the mirror rested on the floor, the space behind the easel from the floor up was entirely hidden. This was done when Merry took the mirror apart to exhibit it.
At that moment M. Mazarin came up through a trap-door in the floor and let down the wooden back of the frame, which formed a shelf, and on that shelf he could rest with ease. When the mirror was returned to the frame, the audience could look through beneath it, and no one could suspect that a human being was concealed back of it.
The black cloth was divided off into squares to correspond with those afterward marked on the mirror with the soap. The squares were numbered and lettered precisely the same, so that the assistant knew where every character was located on the face of the mirror.
The assistant behind the mirror was provided with a strong electro-magnet, attached to a wire running down one leg of the easel to a powerful battery under the stage.
When the assistant heard the numbers called, he placed his magnet opposite the corner where the fly was resting, and then moved it along the back of the mirror to the required square. In that manner he was able to add, subtract, multiply and divide.