19. A Vessel Containing a Liquid of uniform height, although a
Stream flows from it.
If a goblet be placed upon a pedestal, whatever quantity may be drawn from it, it shall always continue full. The construction is as follows. Let A B be a vessel,the mouth of which is closed just at the neck, by the partition C D. Through C Dlet a tube, E F, be inserted, reaching nearly to the bottom; let another tube, G H, be passed through the bottom of the vessel, reaching nearly up to the partition C D; and in the bottom bore a hole, K, to admit the small tube K L. The vessel A B must N stand upon a pedestal, M N 0 X, through which passes the projection of the tube G H, and another tube S T communicating with the pedestal and the goblet P R. Now let wine be poured through E F into A B (the air will pass out through G H), and, if the tube K L be left open, it will pass through into the pedestal and the goblet P R: but, if K L be closed, the vessel A B will be filled. Let, then, the wine run into the pedestal M N 0 X and the goblet P R, so that M N 0 X may be filled as high as the mouth of the tube G H. When this is done, close E, and the wine in A B will no longer flow through K L, for no more air can enter through E to supply the vacuum created. When, therefore, any wine is taken from the goblet, the orifice E must be unclosed, and, the air having found an entrance, the wine will flow again into the pedestal and goblet, until it is full. And this may be done as often as we draw off wine from the goblet. It will be requisite that a small hole be pierced in the side of the pedestal at U, that an equivalent bulk of air may pass into the vessel A B through the orifice G and the hole U.