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Rh (Johannes de Sacrobosco) for use in the University of Paris. While lecturing at Vienna, Purbach's attention was drawn to a young disciple of great promise, Johann Müller, from Königsberg, a small village in Franconia, where he had been born in 1436. He is generally known by the name of Regiomontanus, though he does not seem to have used this name himself, but always that of Johannes de Monteregio. He entered heart and soul into his teacher's studies of the great work of Ptolemy, which embodied all the results of Greek astronomy, and the talented pupil soon became an invaluable co-operator to Purbach. They did not confine themselves to theoretical studies, but, with such crude instruments as they could construct, they convinced themselves of the fact that the places of the planets computed from the astronomical tables of King Alphonso X. of Castile differed very considerably from the actual positions of the planets in the sky. In the midst of these occupations the two astronomers had the good luck to become acquainted with a man who was well qualified to help them to carry out their greatest wishes. This man was Cardinal Bessarion, a Greek by birth, who, as Bishop of Nicæa, had accompanied the Byzantine Emperor on his journey to the Council of Ferrara in 1438, where he tried to bring about a reconciliation between the Greek and Roman Churches. Bessarion remained in Italy and joined the Roman Church, but he never forgot his old country, and contributed very much to make the classical Greek literature known in the West. The translation of the original Almagest (as Ptolemy's work was generally called, from a corruption of the Arabic Al megist, in its