The Saracen Empire was dotted all over with colleges. They were established in Mongolia, Tartary, Persia, Mesopotamia, Syria, Egypt, North Africa, Morocco, Fez, Spain. At one extremity of this vast region, which far exceeded the Roman Empire in geographical extent, were the college and astronomical observatory of Samarcand, at the other the Giralda in Spain. Gibbon, referring to this patronage of learning, says: "The same royal prerogative was claimed by the independent emirs of the provinces, and their emulation diffused the taste and the rewards of science from Samarcand and Bokhara to Fez and Cordova. The vizier of a sultan consecrated a sum of two hundred thousand pieces of gold to the foundation of a college at Bagdad, which he endowed with an annual revenue of fifteen thousand dinars. The fruits of instruction were communicated, perhaps, at different times, to six thousand disciples of every degree, from the son of the noble to that of the mechanic; a sufficient allowance was provided for the indigent scholars, and the merit or industry of the professors was repaid with adequate stipends. In every city the productions of Arabic literature were copied and collected, by the curiosity of the studious and the vanity of the rich." The superintendence of these schools was committed with noble liberality sometimes to Nestorians, sometimes to Jews. It mattered not in what country a man was born, nor what were his religious opinions; his attainment in learning was the only thing to be considered. The great Khalif Al-Mamun had declared that "they are the elect of God, his best and most useful servants, whose lives are devoted to the improvement of their rational faculties; that the teachers of wisdom are the true luminaries and legislators of this world, which, without their aid, would again sink into ignorance and barbarism." After the example of the medical college of Cairo, other medical colleges required their students to pass a rigid examination. The candidate then received authority to enter on the practice of his profession. The first medical college established in Europe was that founded by the Saracens at Salerno, in Italy. The first astronomical observatory was that erected by them at Seville, in Spain.