=The Hydraulic Organ=.—The first attempts to secure regular or steady wind pressure were made by Ctesibus, who lived at Alexandria, about 180 B. C. To him is ascribed the invention of the so-called “=Hydraulic Organ=.” This term seems somewhat of a misnomer, since the water was used merely to give the necessary pressure to the bellows, and to regulate the wind supply. This method was never developed, since the device did not seem applicable to instruments of any considerable size. The trend was rather toward a wind supply from a bellows operated on the same principle as that of the blacksmith’s. In the Hydraulic Organ the water was thus applied: An inverted air receiver, into which the wind was forced by a bellows, was immersed in a tank of water, the pressure of the water around and above the receiver forcing the air through an aperture at the top into the pipes, the pressure being regulated by the volume of water in the tank. The hydraulic organ continued more or less in use up to the early part of the 14th century. =The Earliest Organs=.—The organ developed little as to size or mechanical improvements during the first ten centuries of the Christian Era, and it is difficult to trace the progressive stages in point of time, place or mechanical invention. The first organ known to the people of Western Europe was a present from the Byzantine emperor, Constantine, to Pepin the Short, Major-Domo of the Frankish Kingdom, in 742. It had brass pipes and the “keys” were struck by hands and feet. Eastern organs also came into France in the time of Charlemagne, son of Pepin. The first organ used in Germany was made in 812, modelled after the one just mentioned. In 880, the Pope ordered an organ and an organ builder from Germany, which seems to indicate that the art had found support there at an early date. Although not considered absolutely indispensable, the organ from that time on seems to have been generally adopted for use in churches. Its many imperfections gave ground for criticism, yet today it is considered, _par excellence_, the ecclesiastical instrument. =Increase in the Size of Organs=.—The organ builders of these early days were mostly monks, Pope Sylvester II (1003) being eminent, under the name of Gerbert, prior to his election to the papacy. They built small organs called “=Portative=,” and large organs called “=Positive=.” The old hydraulic organ, owing to its excessive weight, was called “Positive” to distinguish it from the “Portative” or portable organ, and these terms have been perpetuated to the present time. An organ built for the Cathedral at Winchester, England, had ten keys, four hundred pipes and twenty-six bellows, which were operated by seventy men, “in the sweat of their brows.” Since forty pipes were attached to a single key, it may be readily understood why its tone was compared to thunder. The keys were very large, having a deep fall, and required the whole force of the hand to press down a single one.