The American Cyclopædia (1879)/Al-Mamoun, Abu Abbas Abdallah
AL-MAMOUN, Abu Abbas Abdallah, an Abbasside caliph, son of Haroun-al-Rashid, reigned from 813 to 833. After the death of his father in 809 he contested the throne with his brother Al-Amin, who was killed. He converted his chief towns into seats of learning. Various works were translated from Greek and Sanskrit. Algebra and arithmetic were borrowed from the Hindoos, astronomy from the natives of the plains of Mesopotamia, and logic, natural history, and the Aristotelian system from the Greeks of the lower empire. In his wars Al-Mamoun was less successful, and the disintegration of the caliphate by the establishment of independent states in parts remote from the centre, which was begun in the preceding reigns, became more disastrous in his. He was succeeded by his brother Al-Motassem, under whose reign the Seljuks first became body guards of the caliphs, whose empire they were in time to usurp.