Al-AbbÄs ibn Said al-JawharÄ«
Al - Abbas ibn Said al - Dschauhari (Arabic العباس بن سعيد الجوهري, DMG al - ʿ Abbās b Sa ʿ īd al - Ǧawharī; . English transliteration al - Jawhari ) was an astronomer, astrologer and mathematician in the court of the caliph al - Ma ʾ mun (reigned 813-833 ) in the 9th century. He was in the House of Wisdom in Baghdad.
Al - Dschauhari may be of Persian origin. About him little is known. He was court astronomer and astrologer, and was entrusted with the construction of astronomical instruments from the Caliph. He was involved in astronomical observations 829/830 in Baghdad and 832/833 in Damascus. In his house in Baghdad, he met with other scientists to discuss the works of Euclid and Claudius Ptolemy.
From him came an astronomical manual ( Zij ), which is not obtained, however, and something about its content is only indirectly known.
He is known primarily for its Euclid Commentary, parts of which are preserved in manuscript. They contain additions to the fifth book of Euclid's Elements. In a manuscript of Nasir ad-Din at- Tusi also fragments of his additions to the first book of Euclid's elements are obtained in which he attempts to prove the parallel postulate of Euclid. It is inspired by the proof attempt of Simplicius, but is independent of it. Nasir at- Tusi already recognized the error in al - Jawharis proof, which is the first known proof of the parallel postulate attempt in the Arab world.
He is also a - have translated book about poisons from Persian into Arabic - possibly originally Indian.
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