During the first and second centuries of the Hijrah (A.D. 622-816), of all the physical sciences alchemy was studied most. The greatest scientific man of the first century was undoubtedly Khalid, a prince of the Omaiyide dynasty, and the son of Yazid I. His zeal for knowledge and science induced him to get Greek and Syriac works translated by Stephanus into Arabic, especially those which treated on chemistry, or rather alchemy. Khalid, having been once reproached for wasting all his time in researches in the art of alchemy, replied: 'I have occupied myself with these investigations to show my contemporaries and brothers that I have found in them a recompense and a reward for the Khalifate which I lost. I stand in need of no man to recognise me at court, and I need not recognise anyone who dances attendance at the portals of dominion either from fear, ambition, or covetousness.' He wrote a poem on alchemy, which bears the title of 'Paradise of Wisdom,' and of him Ibn Khallikan says: 'He was the most learned man of the tribe of Koraish in all the different branches of knowledge. He wrote a discourse on chemistry and on medicine, in which sciences he possessed great skill and solid information.' He died A.D. 704. Later on Jaber bin Hayam, with his pupils, became a model for later alchemists, and he has been called the father of Arabian chemistry. He compiled a work of two thousand pages, in which he inserted the problems of his master, Jaafar as Sadik, considered to be the father of all the occult sciences in Islam. Jaber was such a prolific writer that many of his five hundred works are said to bear his name only on account of his celebrity, but to have been written in reality by a variety of authors. His works on alchemy were published in Latin by Golius, under the title of 'Lapis Philosophorum,' and an English translation of them by Robert Russell appeared at Leyden in A.D. 1668. Jaber died A.D. 766, and is not to be confounded with Al-Jaber (Geber), the astronomer, who lived at Seville about A.D. 1190, and constructed there an astronomical observatory.