A gazelle whose body was covered all over with pearls and the most precious stones; the stomach was white and composed of a series of pearls of the purest water. A sardonyx table, with conical feet of the same substance; it was large enough for several people to eat there at the same time. A garden, the soil made of chased and gilt silver and yellow earth. There were silver trees, with fruits made of precious materials. A golden palm-tree enriched with superb pearls. It was in a golden chest and its fruit was made of precious stones representing dates in every stage of ripeness. This tree was of inestimable value.[105] About the time the monk Gerbert was accused of sorcery because he understood the elements of geometry, the Caliph Aziz-Billah founded the university of Cairo, the greatest Mohammedan institution of learning. This was two hundred years before the organization of the university of Paris, and the lectures at the mosque of El-Azhar are said to have been attended by twelve thousand students. Munk was of opinion that Arabic philosophy reached its apogee with Averrhoës, who was born about 1120.[106] Certainly he was the last of a famous line which began at Bagdad three centuries earlier; and Hauréau, in describing the great period of Saint Thomas at Paris, dwelt upon the debt Western learning owed to the Saracens. The splendour of Haroun-al-Raschid is still proverbial. The tales of his gold and silver, his silks and gems, almost surpass belief, and even in his reign the mechanical arts were so advanced that he sent a clock to Charlemagne. Humboldt considered the Arabs as the founders of modern experimental science, and they were relatively skilful chemists, for they understood the composition of sulphuric and nitric acid, and of aqua regia, beside the preparation of mercury and of various oxides of metals. As physicians they were far in advance of Europe. While the Church healed by miracles, and put experimental methods under her ban, the famous Rhazes conducted the hospitals of Bagdad, and in the tenth century wrote a work in ten books, which was printed at Venice as late as 15 10. Practitioners of all nations have used his treatise on small-pox and measles; he introduced mild purgatives, invented the seton, and was a remarkable anatomist. He died in 932. William of Tyre stated that the Frankish nobles of Syria preferred the native or Jewish doctors; and though Saladin sent his physician to Richard, Richard never thought of sending an Englishman to Saladin when afterwards attacked by illness.