Hydraulic ORGAN, denotes a musical machine that plays by water instead of wind. Of these there are several in Italy, in the grottoes of vineyards. Ctefebes of Alexandria, who lived in the time of Ptolemy Euergetes, is said to have invented organs that played by compressing the air with water, as is still practised. Archi-
Orgasm medes and Vitruvius have left us descriptions of the hydraulic organ.
Oribasus In the cabinet of Queen Christina is a beautiful and large medallion of Valentinian, on the reverse whereof is seen one of these hydraulic organs; with two men, one on the right, the other on the left, seeming to pump the water which plays it, and to listen to its sound. It has only eight pipes, placed on a round pedestal. The inscription is PLACEA SPETRI, if it be not wrong copied, which we suspect to be the case.