Let A B C (Fig. 62), be a bent syphon, or tube, of which the leg A B is plunged into a vessel D E containing water. If the surface of the water is in F G, the leg of the syphon, A B, will be filled with water as high as the surface, that is, up to H, the portion H B C remaining full of air. If, then we draw off the air by suction through the aperture C, the liquid also will follow. And if the aperture C be level with the surface of the water, the syphon, though full, will not discharge the water, but will remain full: so that, although it is contrary to nature for water to rise, it has risen so as to fill the tube A B C; and the water will remain in equilibrium, like the beams of a balance, the portion H B being raised on high, and the portion B C suspended. But if the outer mouth of the syphon be lower than the surface F G, as at K, the water flows out, for the liquid in K B, being heavier, overpowers and draws toward it the liquid B H. The discharge, however, continues only until the surface of the water is on a level with the mouth K, when, for the same reason as before, the efflux ceases. But if the outer mouth of the tube be lower than K, as at L, the discharge continues until the surface of the water reaches the mouth A. [Illustration: FIG. 62.] _The Syringe_ is an instrument of very high antiquity and was probably the first machine consisting of a cylinder and piston that was especially designed to force liquids. In the closed end a short conical pipe is attached whose dimensions are adapted to the particular purpose for which the instrument is to be used. The piston is solid and covered with a piece of soft leather, hemp, woolen listing, or any similar substance that readily imbibes moisture, in order to prevent air or water from passing between it and the sides of the cylinder. When the end of the pipe is placed in a liquid and the piston drawn back, the atmosphere drives the liquid into the cylinder; whence it is expelled through the same orifice by pushing the piston down: in the former case the syringe acts as a sucking pump: in the latter as a forcing one. They are formed of silver, brass, pewter, glass, and sometimes of wood. For some purposes the small pipe is dispensed with, the end of the cylinder being closed by a perforated plate, as in those instruments with which gardeners syringe their plants. WELLS. Long before pumping devices were conceived, wells existed as the invention of prehistoric man. Herewith is a sectional view of _Joseph’s Well_ to be seen at the present time at Cairo, Egypt. Scientists think it the production of the same people that built the pyramids and the unrivaled monuments of Thebes, Dendaroh and Ebsambone. The magnitude of the well and the skill displayed in its construction is perfectly unique. [Illustration: JOSEPH’S WELL.]