The rulers under whose auspices the first steps in the great Arab Renaissance were taken, belonged to what is known as the Abbaside Dynasty, the founder of which was Abbas (566–652 A. D.), the uncle of Mohammed. His descendants ruled as Caliphs of Bagdad, on the eastern bank of the Tigris, for many centuries (from 750 A. D. onward).[47] Almansur, the second Caliph of this dynasty, felt a very strong desire that his people, the Arabs, should acquire knowledge of all the useful branches of learning, and more especially of medicine and philosophy; and accordingly, as the Greeks were then universally admitted to be the only nation which possessed that knowledge, and as scarcely any scientific books written in the Arabic language existed at that early date, he directed all his efforts to the finding of Greek originals and of the men qualified to translate them into Arabic. Already as early as the sixth century A. D., Sergius, a Christian of Ras el Ain, had translated a considerable number of Greek treatises into the Syrian tongue, but his work was found to be of an inferior character, and for this reason could not be utilized to any great extent in the present undertaking. Honein (ninth century), one of the most eminent scholars of the Arabic Renaissance, revised a few of these translations and thus rendered them of some service; but by far the larger part of this gigantic task of creating Arabic versions of the classical works of Greek literature, was performed during the ninth century, a period during which the reign of the Arabs extended from the Ganges on the east to the Atlantic on the west. By the end of the eighth century the work of translating had advanced only to the point of producing a single treatise on medicine and a few relating to alchemy; but before the ninth was completed, the Arabs had in their possession, in the form of translations, nearly all the scientific literature of Greece, and, more than this, they could boast that not a few men belonging to their own nation had already become celebrated as scientists of the very first rank.