(which acted as the rocket's fuel). Decades before the West's age of exploration, the Chinese emperors of the Ming Dynasty also sent large fleets on maritime voyages, some reaching Africa. Hellenistic Mediterranean The Hellenistic period of Mediterranean history began in the 4th century BC with Alexander's conquests, which led to the emergence of a Hellenistic civilization representing a synthesis of Greek and Near-Eastern cultures in the Eastern Mediterranean region, including the Balkans, Levant and Egypt. With Ptolemaic Egypt as its intellectual center and Greek as the lingua franca, the Hellenistic civilization included Greek, Egyptian, Jewish, Persian and Phoenician scholars and engineers who wrote in Greek. Hellenistic engineers of the Eastern Mediterranean were responsible for a number of inventions and improvements to existing technology. The Hellenistic period saw a sharp increase in technological advancement, fostered by a climate of openness to new ideas, the blossoming of a mechanistic philosophy, and the establishment of the Library of Alexandria in Ptolemaic Egypt and its close association with the adjacent museion. In contrast to the typically anonymous inventors of earlier ages, ingenious minds such as Archimedes, Philo of Byzantium, Heron, Ctesibius, and Archytas remain known by name to posterity. Ancient agriculture, as in any period prior to the modern age the primary mode of production and subsistence, and its irrigation methods, were considerably advanced by the invention and widespread application of a number of previously unknown water-lifting devices, such as the vertical water-wheel, the compartmented wheel, the water turbine, Archimedes' screw, the bucket-chain and pot-garland, the force pump, the suction pump, the double-action piston pump and quite possibly the chain pump. In music, the water organ, invented by Ctesibius and subsequently improved, constituted the earliest instance of a keyboard instrument. In time-keeping, the introduction of the inflow clepsydra and its mechanization by the dial and pointer, the application of a feedback system and the escapement mechanism far superseded the earlier outflow clepsydra. Innovations in mechanical technology included the newly devised right-angled gear, which would become particularly important to the operation of mechanical devices. Hellenistic engineers also devised automata such as suspended ink pots, automatic washstands, and doors, primarily as toys, which however featured new useful mechanisms such as the cam and gimbals. The Antikythera mechanism, a kind of analogous computer working with a differential gear, and the astrolabe both show great refinement in astronomical science. In other fields, ancient Greek innovations include the catapult