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Arabian Lefends Al-Farghani

Mention might be made of about forty mathematicians and astronomers who wrote books on these subjects. The best of them, such as Al-Farghani (Alfraganius) and others, lived at the court of Mamun, who built an astronomical observatory in Baghdad and another near Damascus, on Mount Kasiun. He caused also two degrees of the meridian to be measured on the plain of Sinjar, so as to ascertain the circumference of the earth with more precision.
In A.D. 824 there were held philosophical disputations in his presence. Al-Farghani was the author of an introduction to astronomy, which was printed by Golius at Amsterdam in 1669, with notes.