Pottery Model of the Water Organ
A pottery model of the water organ. The water organ or hydraulic organ (early types are sometimes called hydraulis, hydraulos, hydraulus or hydraula) is a type of automatic pipe organ blown by air, where the power source pushing the air is derived by water from a natural source (e.g. by a waterfall) or by a manual pump. Consequently, the water organ lacks a bellows, blower, or compressor. In addition to being the source of power to push air through the organ pipes, the water is also used as a source of power to drive a mechanism similar to that of the Barrel organ, which has a pinned barrel that contains a specific song to be played.
Encyclopaedia Britannica (11th ed., vol. 20) (New York, NY: The Encyclopaedia Britannica Company, 1910)