MAGELLANIC CLOUDS. 337 



which he composed at the Court of the Sultans of the dynasty 

 of the Buyides, he says that " below the feet of the Suhel (by 

 which he expressly means the Suhel of Ptolemy, Canopus, 

 although the Arabian astronomers named many other large 

 stars of Argo, el-sefina, Suhel,) there is a ' white spot,' which 

 is invisible both in Irak (in the district of Bagdad and in 

 Nedsch, 'Nedjcd,') and in the more northern and mountainous 

 part of Arabia; but may be seen in the Southern Tehama, 

 between Mecca and the extremity of Yemen, along the coast 

 of the Red Sea." 88 The relative position of the White Ox to 

 Canopus, is here indicated with sufficient accuracy for the 

 naked eye; for the Right Ascension of Canopus is 6h. 20m., 

 and the eastern margin of the larger Magellanic Clouds lies 

 in Right Ascension 6h. The visibility of the Nubecula major 

 in northern latitudes cannot have been appreciably affected by 

 the precession of the equinoxes since the tenth century, 

 for the maximum distance from the north was attained during 

 the succeeding ten centuries If we follow the recent de- 

 termination of position for the larger cloud by Sir John 

 Herschel, we shall find that it was perfectly visible as far 

 north as 17 in the time of Abdurrahman Sufi ; at the present 

 time it is seen in about 18 north latitude. The southern 

 clouds must therefore have been visible throughout the whole 

 of south-western Arabia, in Hadhramaut (noted for its frank- 

 incense) as well as in Yemen, the ancient seat of civilization 



82 Ideler, Untersuchungcn uber den Ursprung und die Bedeu- 

 tung der Sternnamen, 1809, p. xlix. 262. The name Ab- 

 durrahman Sufi was contracted by Ulugh Beg from Abdur- 

 rahman Ebn-Omar Ebn-Mohammed Ebn-Sahl Abul-Hassan 

 el-Sufi el-Razi. Ulugh Beg, who like Nassir-eddin, amended 

 the Ptolemaic star-positions from his own observations (1437), 

 admits that he borrowed from Abdurrahman Sufi's work, the 

 positions of 27 southern stars, not visible at Sainarcand. 



