EARLY CATALOGUES. Ill 



that of Tycho Brahe (1600), and that of Hevelius (1660). 

 During the short intervals of repose which, amid tumultuous 

 revolutions and devastations of war, occurred between the 

 ninth and fifteenth centuries, practical astronomy, under 

 Arabs, Persians, and Moguls (from Al-Mamun, the son of the 

 great Haroun Al-Raschid, to the Timurite, Mohammed Tar- 

 aghi Ulugh Beg, the son of Shah Rokh), attained an emi- 

 nence till then unknown. The astronomical tables of Ebn- 

 Junis (1007), called the Hakemitic tables, in honor of the 

 Fatimite calif, Aziz Ben-Hakem Biamrilla, afford evidence, 

 as do also the Ilkhanic tables* of Nassir-Eddin Tusi (who 

 founded the great observatory at Meragha, near Tauris, 1259), 

 of the advanced knowledge of the planetary motions — the 

 improved condition of measuring instruments, and the mul- 

 tiplication of more accurate methods differing from those em- 

 ployed by Ptolemy. In addition to clepsydras,! pendulum- 

 oscillations:!: were already at this period employed in the 

 measurement of time. 



The Arabs had the great merit of showing how tables 

 might be gradually amended by a comparison with observa- 

 tions. Ulugh Beg's catalogue of the stars, originally written 

 in Persian, was entirely completed from original observations 

 made in the Gymnasium at Samarcand, with the exception 

 of a portion of the southern stars enumerated by Ptolemy, $ 



* Cosmos, vol. ii., p. 222, 223. The Paris Library contains a manu- 

 script of the Ilkhanic Tables by the hand of the son of Nassir-Eddin. 

 They derive their name from the title " Ilkhan," assumed by the Tar- 

 tar princes who held rule in Persia. — Reinaud, Introd. de la Giogr. 

 d' Aboulfida, 1848, p. cxxxix. 



t [For an account of clepsydras, see Beckmanrfs Inventions, vol. i., 

 341, et seq. (Bohn's edition).] — Ed. 



t Sedillot fils, ProUgomenes d^es Tables Astr. d'Oloug-Beg, 1847, p. 

 cxxxiv., note 2. Delambre, Hist, de V Astr. du Moyen Age, p. 8. 



§ In my investigations on the relative value of astronomical determ- 

 inations of position in Central Asia (Asie Centrale, t. hi., p. 581-596), I 

 have given the latitudes of Samarcand and Bokhara according to the 

 different Arabic and Persian MSS. contained in the Paris Library. I 

 have shown that the former is probably more than 39° 52', while most 

 of the best manuscripts of Ulugh Beg give 39° 37', and the Kitab al- 

 athual of Alfares, and the Kanum of Albyruni, give 40°. I would again 

 draw attention to the importance, in a geographical no less than an as- 

 tronomical point of view, of determining the longitude and latitude of 

 Samarcand by new and trustworthy observations. Burnes's Travels 

 have made us acquainted with the latitude of Bokhara, as obtained from 

 observations of culmination of stars, which gave 39° 43' 41". There is, 

 therefore, only an error of from 7 to 8 minutes in the two fine Persian 

 and Arabic MSS. (Nos. 164 and 2460) of the Paris Library. Major Ren- 

 nell, whose combinations are generally so successful, made an error of 



