The most distinguished of the _alumni_ of Harran was Thabit b. Qurra (d. 289 A.H.), a scholar familiar with Greek, Syriac, and Arabic, who produced many works on logic, mathematics, astrology, and medicine, as well as on the ritual and beliefs of the paganism to which he remained faithful. Following in his footsteps were his son Abu Sa`id Sinan, his grandsons Ibrahim and Abu l-Hasan Thabit, and his great grandsons Ishaq and Abu l-Faraj. All these specialized in mathematics and astronomy. It seems that we ought to associate with Harran _Jabir b. Hayyan_ a perfectly historical character but of somewhat uncertain date, but believed to have been a pupil of the `Umayyad prince Khalid, who distinguished himself by his researches in chemistry. Many chemical treatises bear the name of Jabir and a great proportion of these are probably quite authentic. M. Berthelot in the 3rd volume of his _La chimie au moyen age_ (Paris, 1893) has made a careful analysis of the Arabic chemists and regards the whole material capable of division into two classes, the one a reproduction of the investigations of the Greek chemists of Alexandria, the other as representing original investigations, though based upon the Alexandrian studies in the first place, and all this original material he regards as due to the initiative of Jabir who thus becomes in chemistry very much what Aristotle was in logic. Berthelot publishes in this book six treatises claiming to be by Jabir, and these he regards as representative of all Arabic chemical material, the later investigators continuing in the lines laid down by this first investigator. For a long time the main object in view was the transmutation of metals, but at a later period chemistry enters into closer connection with medical work though never losing the metallurgical character which we imply when we speak of “alchemy.” The object in view of the Arabic students of alchemy does not appeal to the modern scientist, although the possibility of transmuting elements is no longer regarded as the impossible dream which it appeared to the chemists of the nineteenth century: and, at the same time, it is perfectly clear that with admitted limitations, the Arabic chemists were bona fide investigators, though not understanding correctly the results of the experiments they made.