As regards the philosophical and exact sciences the Moslems naturally derived their ideas and material from Greek culture, which had established itself in Egypt, Syria, and Western Asia since the time of Alexander's conquests. When the Syrian school of Edessa was broken up by ecclesiastical dissensions towards the end of the fifth century of our era, the expelled savants took refuge in Persia at the Sásánian court, and Khusraw Anúshirwán, or Núshírwán (531-578 A.D.)--the same monarch who welcomed the Neo-platonist philosophers banished from Athens by Justinian--founded an Academy at Jundé-shápúr in Khúzistán, where Greek medicine and philosophy continued to be taught down to ‘Abbásid days. Another centre of Hellenism was the city of Ḥarrán in Mesopotamia. Its inhabitants, Syrian heathens who generally appear in Muḥammadan history under the name of 'Ṣábians,' spoke Arabic with facility and contributed in no small degree to the diffusion of Greek wisdom. The work of translation was done almost entirely by Syrians. In the monasteries of Syria and Mesopotamia the writings of Aristotle, Galen, Ptolemy, and other ancient masters were rendered with slavish fidelity, and these Syriac versions were afterwards retranslated into Arabic. A beginning was made under the Umayyads, who cared little for Islam but were by no means indifferent to the claims of literature, art, and science. An Umayyad prince, Khálid b. Yazíd, procured the translation of Greek and Coptic works on alchemy, and himself wrote three treatises on that subject. The accession of the ‘Abbásids gave a great impulse to such studies, which found an enlightened patron in the Caliph Manṣúr. Works on logic and medicine were translated from the Pehleví by Ibnu ’l-Muqaffa‘ († about 760 A.D.) and others. It is, however, the splendid reign of Ma’mún (813-833 A.D.) that marks the full vigour of this Oriental Renaissance. Ma’mún was no ordinary man. Like a true Persian, he threw himself heart and soul into theological speculations and used the authority of the Caliphate to enforce a liberal standard of orthodoxy. His interest in science was no less ardent. According to a story told in the _Fihrist_,[676] he dreamed that he saw the venerable figure of Aristotle seated on a throne, and in consequence of this vision he sent a deputation to the Roman Emperor (Leo the Armenian) to obtain scientific books for translation into Arabic. The Caliph's example was followed by private individuals. Three brothers, Muḥammad, Aḥmad, and Ḥasan, known collectively as the Banú Músá, "drew translators from distant countries by the offer of ample rewards[677] and thus made evident the marvels of science. Geometry, engineering, the movements of the heavenly bodies, music, and astronomy were the principal subjects to which they turned their attention; but these were only a small number of their acquirements."[678] Ma’mún installed them, with Yaḥyá b. Abí Manṣúr and other scientists, in