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FIG. 4.2.
Hydrostatic Organ |
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The water level in the cistern was higher than that in the dome, and therefore the water in the dome exerted a constant upward pressure on the air above it. In this way the intermittent inflow of air from the pump was converted into a steady flow up to the wind canals and pipes. (A valve prevented its return up the duct leading from the pump.) |
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The air pump was itself a revolutionary invention of Ctesibius', with practical applications that have been exploited ever since. It consisted of a piston in a cylindrical chamber at the side of the cistern, and it was operated by a long lever supported on a pivot. (In the later organ there were two pumps, one at each side.) The organist had a young assistant to work the lever up and down. The cistern was housed in a handsome cabinet, generally square or hexagonal in plan, up to a metre high, rather less in diameter but mounted on a broader platform for stability. In most cases the standing player |
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