Chemical Notions of an Early Ninth-Century Christian Encyclopedist

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HORTLY after, or somewhat contemporary with, the time of J?bir ibn Hayy?n (ca. latter half of the eighth century) lived Ayy?b al-Ruh?w?. Ruh? is the Arabic name for the one-time great Nestorian city of Edessa. This Job of Edessa (b. ca. 769, d. ca. 835), as he is known in English, was a Nestorian physician and trans lator from Greek into Syriac and perhaps into Arabic. He is men tioned briefly by al-Nadim1 (987) and Hunain ibn Ishaq2 (ninth century). The latter states that Job of Edessa translated thirty-six of Galen's works into Syriac; some of these were used by Hunain himself. Bar Hebraeus 3 and ibn abi Usaibica 4 also name him. Of the Syriac works known, the more interesting is his Book of Treasures? an encyclopedia of physical and natural sciences as taught in Baghdad about a. d. 817. It is this work which contains the chemical ideas of the time which give it an important place in the history of early Arabic chemistry. Job of Edessa begins with the origin of the simple and compound elements 6 according to Aristotle; the former are perceived mentally and the latter by the senses. Heat, cold, dryness, and moisture are the simple elements; earth, air, fire, and water are the compound ones. Earth, water, air, and fire are considered as being in layers with