Fig. 272. Fig. 273.
Fig. 274.
The handles further serve, as already mentioned, to move the cylinders backwards and forwards as may be required. It should, however, be noted that no backward or forward movement can take place so long as either of the pistons stops the opening b; but as soon as the piston is, by turning the proper handle, depressed ever so little below the level of the surface-plate, it no longer forms any obstacle to the movement. The trap is fixed in the table in such manner that the handles g h shall be just within the opening at the back of the table (see [Fig. 274]), and thus be within easy reach of the performer’s hands when standing behind it. We will suppose, for the sake of illustration, that the performer desires to change an empty tumbler (of small size) to a full one. The trap is beforehand prepared by bringing the foremost cylinder c under the opening b. The full glass is then placed on the top of the piston, which is then lowered gently downwards by means of the proper handle, the glass sinking into the cylinder. The cylinders are now pushed forward, so that d in turn comes under b, the piston being then moved up into its proper place, and so closing the opening. This is, of course, arranged before the curtain rises.
When the performer desires to perform the trick, he places the empty glass upon b, and conceals it with a cover of any kind. Standing carelessly behind the table, and keeping the attention of the audience occupied by any observations he may deem most appropriate for that purpose, he takes hold with his right hand of the handle h, and turns it outward, thereby lowering the empty glass into d. As soon as he feels that it will sink no further, he shifts his hand to the handle a, and therewith draws the cylinders back so as to bring c under b, and then, by turning g, gently raises the full glass of water up through b to the surface of the table. The reader will now perceive the reason why, as already mentioned, the piston in d is made a little tight, so as to require the assistance of the handle to raise it into its position. It is necessary that this piston, when once depressed with the object to be changed, shall remain down while the hand is shifted from handle h to handle g. If it were not made to work somewhat stiffly, the moment the handle h was released the piston would instantly fly up again with the object upon it, thus neutralizing what had been already done. The cylinder c, which is to produce the substitute object, is not brought under b until the hand of the performer is already on the handle belonging to it, and can thereby check its upward ascent as may be necessary.
It is obvious that the changing trap will be equally available to produce an object under an empty cover. The object to be produced will be placed in c as above, the piston in d going down empty, and that in c rising with the object upon it.
Fig. 275.
