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The Magic Bottle - Harper's


There are few persons who have not been puzzled, when witnessing the exhibitions of conjurers and performers of feats of legerdemain, by the magic bottle, out of the neck of which the exhibitor can pour any one of quite a number of liquids at his will. It may interest the reader to see an explanation of the means by which the apparently magical effect is produced, especially as it involves an explanation of a certain philosophical principle which it is very useful for all to understand.

The pressure of the atmosphere all around us is so great that no liquid can issue against it from a close vessel, unless air is at the same time admitted to balance the external pressure by an internal one of the same amount. In the case of pouring water from a bottle the mouth of which is tolerably large, the air passes in in large bubbles as the water comes out, producing the gurgling sound always heard in such a case.

Where the orifice is too small to allow of the admission of these bubbles of air, the liquid will only flow out as fast as the air is allowed to enter in some other way, as shown in the engraving, where the water will not issue from the lower end of the tube except when the finger is raised from the upper end so as to admit the air.

There are various ingenious contrivances by means of which curious effects are produced through the operation of this principle. One, called the magic tunnel, is made double, with a space inclosed between the walls. There is an orifice communicating with this chamber at the top of the handle, which orifice is so situated that it can be opened or closed at pleasure by the thumb of the person holding it without attracting the attention of the spectator. Now if the body of the tunnel is filled, or partly filled, with pure water, while the hidden chamber contains a liquid deeply colored—with cochineal, for example—the person holding it can cause pure water to flow from it by keeping the orifice in the handle closed by his thumb, or colored water by simply raising his thumb and allowing the liquid in the concealed chamber to flow out and mingle with the clear water as it issues from the tube below.

Fig. 1. Fig. 1.
Fig. 2. Fig. 2.

The magic bottle acts on the same principle, though presenting it in another form. The bottle is usually made of tin, though colored on the outer surface to represent glass. Within, it contains several different receptacles, as shown in Fig. 1, each communicating by a separate pipe with the mouth of the bottle. Each of these receptacles is also provided with another tube, by which air may be admitted so as to allow the liquid contained in it to flow. These air tubes open by orifices in the side of the bottle, as shown in Fig. 2, which are covered and concealed by the thumb and the ends of the fingers of the operator, and may be kept closed or may be slightly opened at pleasure. By this means any one of five different liquids may be poured from the mouth of the bottle.

Of course it requires some dexterity to manipulate such an apparatus skillfully, in order to keep all the holes concealed from the spectators, and to open the right one, just enough to admit the air, and at the right time. The point of interest, however, for the general reader in the whole subject is the philosophical principle which is involved, namely, that the pressure of the atmosphere in every direction all around us is such that no liquid can issue from any orifice against the force of it acting from without inward, unless by the admission of air or the providing by some other means of an equal force to act from within outward as a counterpoise.