OP THE COSMOS. NUMBER OF THE FIXED STARS. 93 



for their epoch complete, star-catalogues : that of Ulugh 

 Beig (1437), of Tycho Brahe (1600), and of Hevelius 

 (1660). In the short intervals of repose which inter- 

 vened between the devastations of war and wild intestine 

 revolutions, practical astronomy flourished among the 

 Arabians, Persians, and Moguls, from the middle of the 

 9th to that of the ] 5th centuries, from Al-Mamun, son 

 of the great Harun Al-Raschid, to the Timuride, Mohammed 

 Teraghi Ulugh Beig, son of the Shah Eokh, in a degree 

 never before witnessed. The astronomical tables of Ebn- 

 Junis (1007), called the Hakemite Tables in honour of the 

 Patimite Caliph Aziz Ben-Hakem Biamrilla, testify, as do 

 also the Ilkhanic Tables O? 8 ) of Nassir-Eddin Tusi, the 

 builder of the great observatory of Meragha, not far from 

 Tauris (1259), to the more advanced knowledge of the 

 planetary movements, the improvement of measuring instru- 

 ments, and the multiplication of methods differing from 

 those of Ptolemy, and superior to them in exactness. In 

 addition to Clepsydras, Pendulum oscillations ( 179 ) now 

 began to be used as a measure of time. 



The Arabians have the great merit of having shewn how 

 by the intercomparison of observations and tables the latter 

 might be greatly improved. The star-catalogue of Ulugh 

 Beig (originally written in Persian), with the exception of 

 a part of the southern stars of Ptolemy not visible ( 18 ) in 

 the latitude of 39 52' (?), was prepared in the Gymnasium at 

 Samarcand from original observations. It contained at first 

 only 1019 positions of stars, which are reduced to the year 

 1437. A later commentary furnishes 300 additional stars 

 observed by Abu-Bekri Altizini in 1533. Thus we 

 come, through Arabians, Persians, and Moguls, down to 



