It is usual to bring the trick to a conclusion by apparently throwing the fluid over the audience as already described, but should the performer be provided with a number of small cups and a tray, that portion of the beverage not used may be handed round as refreshments.
The Hydrostatic Tube.—This is a trick of comparatively recent invention. It requires very careful handling, and the performer must be possessed of almost superhuman nerve to present it successfully to a critical audience. It produces, however, a most extraordinary effect, and on this account is to be recommended.
A piece of paper is placed at the bottom of a glass tube or chimney used for gas, which is then filled with water, while the top of the tube is covered with a second piece of paper. The right hand is then placed on the top paper and the position of the tube reversed. The papers are then, each in turn, removed, but the water does not fall from the cylinder; on the contrary, it remains suspended without visible means of support. The papers are now replaced, and the top one is pierced with a hatpin, when, on the pin being withdrawn, the water at once falls into a basin placed ready to receive it under the tube.
This surprising result is due entirely to a well-known natural law, viz., the pressure of the atmosphere, and is nothing more nor less than a modification of the old schoolboy trick of keeping a glass of water inverted by means of a sheet of paper. The new arrangement will, however, require special explanation.
Each end of the cylinder is fitted with a glass cap, grooved to fit into and over it at the same time; this is necessary to avoid slipping. The ends of the tube, also the edges of the caps, must be ground, so that the point of juncture shall be air-tight. One of the caps has a small hole drilled through the centre. (See Fig. 44.)
When about to present the trick the two glass caps are laid on the bottoms of two upturned tumblers, where they are quite invisible. The performer then draws attention to two square pieces of paper, which he dips into the water contained in the bowl, afterward laying them down on the glass tumblers, and over the glass discs. He next shows the tube, passing his wand through it to prove that it has not undergone any preparation. Then taking one of the papers, and at the same time secretly securing one of the discs (not the one with the hole in it), he places it at the bottom of the tube, which is forthwith stood on the palm of the left hand. The tube is then filled with water and covered with the remaining piece of paper and glass cap.
Fig. 44.—Hydrostatic
Tube
The position of the tube is then reversed, after which it is taken by the centre and both papers are removed. The water will not run out from the small hole in the bottom cap owing to the fact that no air can get in at the top. The glass caps being absolutely invisible, the water will now appear to be suspended in the tube without any natural means of support.
The papers are again placed on the ends of the tube, where, being wet, they readily adhere. The hands are now placed one on each end and the tube is reversed; this is necessary to bring the cap with the hole in it to the top. The top paper is then pierced with the hatpin, which, passing through the hole in the cap, gives the impression that there cannot be anything but the paper covering the ends of the tube. When the pin is withdrawn the air rushes into the tube, and, as a natural consequence, the paper and disc fall from the bottom, liberating the water. The bowl should be half full of water when the cap falls, to avoid fracture of the glass. The cap is then brought away from the top of the tube under cover of the piece of paper, and both are dropped into the bowl, when the tube can be once more given for examination.