As a visible evidence of the interest of the Arabs in astronomical science, and of their skill in the construction of astronomical instruments, we have preserved to us, besides numerous astrolabes, no less than seven globes, known to have been constructed prior to the year 1600. The oldest one extant is now in the possession of the R. Istituto di Studi Superiori of Florence, Italy.[63] This fine example of the skill which was attained by the instrument makers of Valencia, Spain, at one time a flourishing center of Arabic culture, appears to date from the second half of the eleventh century. According to an inscription on the globe, we learn that it was made at Valencia by Ibrahim Ibn Said-as-Sahli, in the year 473 of the Hegira, a date equivalent to 1080 A. D. This date Professor Meucci finds confirmed by a careful study of the position of the stars represented on the globe. He notes, for example, that the star Regulus had been placed at a distance of 16 degrees 40 minutes from the sign of Leo. Ptolemy, in the year 140 A. D., gave this distance as 2 degrees 30 minutes. According to Albaregnius, this star advances about one degree every sixty-six years. Since 140 A.D. the star, therefore, would have moved 14 degrees 10 minutes, which fact would lead astronomers to place this star, about 1080, as it appears on the globe. The globe is of brass, 20 cm. in diameter, having engraved on its surface forty-seven constellations, as given by Ptolemy, omitting only the Cup, with 1042 stars, each with its respective magnitude indicated. A second Arabic celestial globe, which dates from the year 1225, has been described in detail in a monograph by Assemani, which he issued in the year 1790.[64] This remarkably interesting object belonged, at the time, to the extensive and celebrated collection of antiquities and curiosities of Cardinal Borgia, in Velletri, but may now be found in the Museo Nazionale of Naples. It is composed of two brass hemispheres, having both horizon and meridian circles, the whole resting upon four supporting feet. A Cufic inscription tells us that it was made by Caissar ben Abul Casem ben Mosafer Alabiaki Alhanefi, in the year of the Hegira 622. Caissar probably was an astronomer at the court of Cairo, and the Mohammedan date as given, translated into Christian reckoning, gives us the year 1225.