THE DICAIOMETER.
This was constructed as follows: Let us suppose a vessel (see the [illustration]) whose neck is closed by a diaphragm. Near the bottom there is placed a small sphere, Τ, of a capacity equal to the quantity that it is desired to pour out. Through the diaphragm there passes a small tube, Δ Ε, which communicates with the small sphere. This tube contains a very small aperture, Δ, near and beneath the diaphragm. The sphere contains at its lower part a small aperture, Ζ, whence starts a tube, Ζ Η, that communicates with the hollow handle of the ewer. Alongside of this aperture the globe contains another one, Λ, through which it communicates with the interior of the ewer. The handle is provided with a vent, Θ. After closing the latter, the ewer is filled with liquid through an aperture that is afterwards stopped up. The tube, Δ Ε, may likewise be made use of, but in this case it is necessary to form a small aperture in the body of the ewer in order to allow the air to make its exit. The globe, Τ, fills at the same time that the ewer does. Now, if we turn the ewer over, leaving the vent Θ open, the liquid in the globe, Τ, and in the small tube, Δ Ε, will flow out. If we close the vent and bring the ewer to its former position, the globe and the tube will fill up anew, since the air that they contain will be expelled by the liquid that enters thereinto. The ewer being again turned over, an equal quantity of liquid will flow anew, save a difference due to the small tube, Δ Ε, since this latter will not always be full, and will empty in measure as the ewer does; but such difference is very insignificant.
MIRACULOUS VESSELS.
Ctesias, the Greek, who was physician to the Court of Persia at the beginning of the fourth century of our era, and who has written a history of that country, narrates the following fact: Xerxes, having caused the tomb of Belus to be opened, found the body of the Assyrian monarch in a glass coffin which was nearly full of oil. “Woe to him,” said an inscription at the side, “who, having violated this tomb, does not at once finish the filling of the coffin.”
Xerxes, therefore, at once gave orders to have oil poured into it; but whatever the quantity was that was put in, the coffin could not be filled. This miracle must have been effected by means of a siphon, analogous to the one found in the Tantalus cup, and which becomes primed as soon as the level rises in the vessel above the horizontal; that is, on a line with the upper part of the tube’s curve. In fact, proof has been found of the use of the siphon among the Egyptians as far back as the eighteenth dynasty, and Heron, in his “Pneumatics” (book xii., chap. iii.), describes a very large number of vessels that are founded upon its use.
The ancients, likewise, solved a problem contrary to that of the tomb of Belus, and that was one connected with the construction of a vessel that should always remain full, whatever was the quantity of water that was removed from it, or, at least, which should remain full even when a large quantity of water was taken from it.
The annexed engraving ([Fig. 1]) shows one of the arrangements employed.
