If a bowl stands upon a pedestal and has an open water-spout, the discharge shall suddenly cease, though there be no slide or tap attached to shut the spout. Let A B (fig. 51), be the bowl on the pedestal C: through the bottom of the bowl and the pedestal insert a tube, D E F, terminating in a spout; and at the handle of the vessel fix a bar, G H, against which another bar, K L, may move about the pin H: at the extremity K place a vertical bar, K M, moving about the pin K: to this bar let a box, N X, be attached at M, having weight, and large enough to inclose the tube D E F. When the bowl is full, if we depress the extremity L of the bar, the box N X will ascend, and, when this is raised, the water in the bowl will be carried out through the tube D E F: but if the extremity L be set free, the box will descend and encompass the tube D E F, and the air it contains, having no way of escape, will disconnect the liquid round the tube D E F, and prevent it from being further carried out through the mouth D. When we again depress the extremity L the spout will run as before. 52. _A Drinking-Horn in which a peculiarly formed Siphon is fixed._ [Illustration: Diagram of apparatus as described in text] The construction of a drinking-horn such that, if a cover of glass be placed upon it, while a discharge is going on from the vessel, the liquid shall ascend into the glass cover and be thrown back. A B C (fig. 52), is a drinking-horn, closed by the covering D E; and from D E extend two tubes, F G, H K, one of them, H K, leading into the interior of the vessel, the other, F G, leading outside. A glass cover, M N, incloses this; and in the top, D E, outside the glass vessel, is an aperture, X, through which water may be poured. When the horn is filled through this aperture, the tube H K will be filled at the same time, and as the water is poured in it will ascend into the glass vessel so as to be carried outside through the tube F G. Thus we shall have the arrangement of a bent siphon, of which H K is the smaller leg and F G the greater, so that it will attract the liquid in the horn as it ascends into the cover; it will also attract the air contained in the cover, which is lighter than the liquid, and the water will appear to be thrown back into the void space left by the air and to descend by its own weight; for this upward motion is contrary to its nature. 53. _A Vessel in which Water and Air ascend and descend alternately._ [Illustration: Diagram of apparatus as described in text]