Ebn-Junis in Cairo have become extremely important with 

 reference to the perturbations and secular changes of the orbits 

 of the two largest planets, Jupiter and Saturn.* The meas- 

 urement of a degree, which the Calif Al-Mamun caused to be 

 made in the great plain of Sindschar, between Tadmor and 

 Rakka, by observers whose names have been transmitted to 

 us by Ebn-Junis, has proved less iknportant in its results than 

 by the evidence which it affords of the scientific culture of the 

 -Arabian race. 



We must regard among the results yielded by the reflection 

 of this culture, in the West, the astronomical congress held 

 at Toledo, in Christian Spain, under Alfonso of Castile, in 

 which the Rabbin Isaac Ebn Sid Hazan played an import- 

 ant part ; and in the far East, the obser^'^atory founded by 

 Ilschan Holagu, the grandson of the great conqueror Genghis 

 Khan, on a hill near Meraghar, and supplied with many in- 

 struments. It was here that Nassir Eddin, of Tus, in Kho- 

 rassan, made his observations. These individual facts deserve 

 to be noticed in a history of the contemplation of the universe, 

 since they tend vividly to remind us of how much the Arabs 

 have effected in difiusing knowledge over vast tracts of terri- 

 tory, and in accumulating those numerical data which contrib- 

 uted, in a great degree, during the important period of Kepler 

 and Tycho, to lay the foundation of theoretical astronomy, 

 and of correct views of the movements of the heavenly bodies. 

 The spark kindled in those parts of Asia which were peopled 

 by Tartars spread, in the fifteenth century, westward to Sa- 

 marcand, where Ulugh Beig, of the race of Timour, establish- 

 ed, besides an observatory, a gymnasium after the manner of 

 the Alexandrian Museum, and caused a catalogue of stars to 

 be drawn up, which was based on wholly ncAV and independent 

 observations.! 



Besides making laudatory mention of that which we owe 

 to the natural science of the Arabs in both the terrestrial and 

 celestial spheres, we must likewise allude to their contribu- 

 tions in separate paths of intellectual development to the gen- 



des Savant, 1843, p. 513-532, 609-626, 719-737 ; 1845, p. 146-166 ; and 

 Comptes Rendus, t. xx., 1845, p. 1319-1323.) 



* Laplace, Expos, du Systeme du Monde, note 5, p. 407. 



t On the observatoty of Meragba, see Delambre, Histoire de V Astro- 

 nomie du Moyen Age, p. 198-203 : and Am. Sedillot, M^m. sur les In- 

 strumens Arabes, 1841, p. 201-205, where the gnomon is described with 

 a circular opening. On the peculiarities of the star catalogue of Ulugh 

 Beisr, see J. J. Sedillot, Traiti des Instrumeiis Astronomiques des Arabea, 

 18Ji4, p. 4 



