Siphon

A device consisting of a pipe or tube bent so as to form two branches or legs of unequal length by which a liquid can be transferred to a lower level as from one vessel to another over an intermediate elevation by the action of the pressure of the atmosphere in forcing the liquid up the shorter branch of the pipe immersed in it while the continued excess of weight of the liquid in the longer branch when once filled causes a continuous flow The flow takes place only when the discharging extremity of the pipe ia lower than the higher liquid surface and when no part of the pipe is higher above the surface than the same liquid will rise by atmospheric pressure that is about 33 feet for water and 30 inches for mercury near the sea level