To the Etruscans is also attributed by some the invention of the hydraulic organ. The Greeks possessed a somewhat similar contrivance which they called hydraulos, i.e. water-flute, and which probably was identical with the organum hydraulicum of the Romans. The instrument ought more properly to be regarded as a pneumatic organ, for the sound was produced by the current of air through the pipes; the water applied serving merely to give the necessary pressure to the bellows and to regulate their action. The pipes were probably caused to sound by means of stops, perhaps resembling those on our organ, which were drawn out or pushed in. The construction was evidently but a primitive contrivance, contained in a case which could be carried by one or two persons and which was placed on a table. The highest degree of perfection which the hydraulic organ obtained with the ancients is perhaps shown in a representation on a coin of the emperor Nero, in the British museum. Only ten pipes are given to it and there is no indication of any key board, which would probably have been shown had it existed. The man standing at the side and holding a laurel leaf in his hand is surmised to represent a victor in the exhibitions of the circus or the amphitheatre. The hydraulic organ probably was played on such occasions; and the medal containing an impression of it may have been bestowed upon the victor.