SEQUEL TO THE EPOCH OF HIPPARCHUS. 245 



Before quitting the subject, we may observe 

 that Astronomy brought back, from her sojourn 

 among the Arabs, a few terms which may still be 

 perceived in her phraseology. Such are the zenith, 

 and the opposite imaginary point, the nadir; 

 the circles of the sphere termed almacantars and 

 azimuth circles. The alidad of an instrument is 

 its index, which possesses an angular motion. Some 

 of the stars still retain their Arabic names ; Aide- 

 bar an, Rig el, Fomalhaut; many others were known 

 by such appellations a little while ago. Perhaps 

 the word almanac is the most familiar vestige of 

 the Arabian period of astronomy 43 . 



43 It is foreign to my purpose to note any efforts of the intel- 

 lectual faculties among other nations, which may have taken 

 place independently of the great system of progressive European 

 culture, from which all our existing science is derived. Other- 

 wise I might speak of the astronomy of some of the Orientals, 

 for example, the Chinese, who are said, by Montucla (i. 465) 

 to have discovered the first equation of the moon, and the proper 

 motion of the fixed stars (the Precession), in the third century of 

 our era. The Greeks had made these discoveries 500 years 

 earlier. 





