Ibn Muqaffa` lived in the reign of al-Mansur and during that same period we are told (Masudi. viii. 291-2) that Arabic versions were made of several treatises of Aristotle, of the _Almagesta_ of Ptolemy, of the book of Euclid, and other material from the Greek. About 156 A.H. an Indian traveller brought to Baghdad a treatise on arithmetic and another on astronomy: the astronomical treatise was the _Siddhanta_ which came to be known to the Arabic writers as the _Sindhind_, it was translated by Ibrahim al-Fazari and opened up a new interest in astronomical studies: some little time afterwards Muhammad b. Musa al-Kharizmi combined the Greek and Indian systems of astronomy, and from this time forth the subject takes a prominent place in Arabic studies. The great Arabic astronomers belong to a later generation, such as Abu Ma`shar of Baghdad, the pupil of al-Kindi, who died in A.H. 272 (= A.D. 885), known to the Latin mediæval writers as “Abumazar,” and Muhammad b. Jabir b. Sinan al-Battani (d. 317 A.H. = A.D. 929) who was known as “Albategnius.” The Indian work on arithmetic was even more important as by its means the Indian numerals were introduced, to be passed on in due course as “Arabic” numerals, and this decimal system of numbering has made possible an extension of arithmetical processes and indeed of mathematics generally which would have been difficult with any of the older and more cumbersome systems. Al-Mansur, after founding Baghdad in A.H. 148 (= A.D. 765) summoned a Nestorian physician, George Boktishu`, from the school at Junde-Shapur and established him a court physician, and from this time there was a series of Nestorian physicians connected with the court and forming a medical school at Baghdad. George fell ill in Baghdad and was allowed to retire to Junde-Shapur, his place being taken by his pupil Issa b. Thakerbokht, who was the author of a book on therapeutics. Later came Bokhtishu` son of George who was physician to Harunu r-Rashid in 171 (= A.D. 787), and then Gabriel, another son of George, who was sent to attend Ja`far the Barmecide in 175 and stood high in Harun’s favour: he wrote an introduction to logic, a letter to al-Ma´mun on foods and drinks, a manual of medicine based on Dioscorus, Galen, and Paul of Aegina, medical pandects, a treatise on perfumes, and other works. In medicine, as will be remembered, the Indian system had been introduced at Junde-Shapur and combined with the Greek, but the latter clearly predominated. Another important settler in Baghdad was the Jewish Syrian physician John bar Maserjoye, who translated the _Syntagma_ of Aaron into Syriac and presided over the medical school gathered in the Muslim capital. For a long time the Arabic work in medicine was limited to translation of the great Greek authorities and practice on the lines learned in Alexandria. We have already referred to the unfortunate influence derived from the Egyptian school which diverted both medicine