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 LITERATURE OF THE ARABS. 91 



med ibn Musa, Abdallah ibn Salial, and Yahia ibn 

 Mansor were eminent writers on this science, and 

 their astronomical tables were admired for their 

 exactness. Albathani (or Albategni), one of the 

 most learned men that adorned the court of Mokta- 

 der, was justly renowned as the author of the Sabian 

 tables, drawn up from the astronomical observa- 

 tions which he made in the course of forty years 

 (A. D. 879-921), at Racca, on the Euphrates. His 

 laborious researches were of the highest importance 

 to the science. He gave a new and improved theory 

 of the sun, from which some valuable results were 

 derived ; and supplied the defects of the Ptolemsean 

 tables by his more accurate observations. His 

 work on " The Science of the Stars," which is still 

 extant, long held a very high place in the estima- 

 tion of philosophers. We owe to him a more cor- 

 rect calculation of the obliquity of the ecliptic than 

 had hitherto been made ; he also determined the 

 annual movement of the equinoxes, and found the 

 duration of the tropical year to be 365 days and a 

 decimal fraction. 



His contemporaiy, Ibn Korrah, likewise observed 

 the declination of the ecliptic — distinguished the 

 motion of the apogee of the sun and planets from 

 that of the stars in longitude ; and, Avhat is most im- 

 portant of all, ascertained that the solar revolution 

 was completed in 365 days, 6 hours, 9 minutes, and 

 12 seconds — a calculation not very different from 

 that now in use. Arzakel, the reputed author of the 

 Toledan tables, who flourished towards the end of 

 the eleventh century, was famous for his hypothesis 

 to account for the diminution of the sun's eccen- 

 tricity, which he conceived to have taken place 

 since the time of Ptolemy, and the motion of the 

 sun's apogee. His idea was adopted by Coperni- 

 cus ; and subsequently applied to the moon by Ho- 

 roccius, Newton, Flamstead, and Halley. 



Modern astronomy is indebted to the Saracens for 



