504 COSMOS. 



medical knowledge of the Indians, was translated by learned 

 men belonging to the court of the Caliph Harun Al-Raschid, 

 a proof of the early introduction of Sanscrit literature. The 

 Arabian mathematician Albiruni even went to India for the 

 purpose of studying astronomy. His writings, which have 

 only recently been made accessible to us, prove how intimately 

 he had made himself acquainted with the country, traditions, 

 and comprehensive knowledge of the Indians.* 



However much the Arabian astronomers may have owed to 

 the earlier civilized nations, and especially to the Indian and 

 Alexandrian schools, they have, nevertheless, considerably 

 extended the domain of astronomy by their own practical 

 endowments of mind ; by the number and direction of their ob- 

 servations; the improvement of their instruments for angular 

 measurement; and their zealous efforts to rectify the older 

 tables by a comparison with the heavens. In the seventh 

 book of the Almagest of Abul Wefa, Sedillot found a notice 

 of the important inequality in the moon's longitude, which 

 disappears at the syzygies and quadratures, attains its maxi- 

 mum at the octants, and has long been regarded, under the 

 name of variation, as the discovery of Tycho Brahe.f The 

 observations of Ebn-Junis in Cairo, have become extremely 

 important with reference to the perturbations and secular 

 changes of the orbits of the two largest planets, Jupiter and 

 Saturn. J The measurement of a degree, which the Caliph 

 Al-Mamun caused to be made in the great plain of Sindschar, 



* Keinaud, Fragments Arabes relatifs a I'fnde, pp. xii.-xvii. 96-126, 

 and especially 135-160. Albiruni's proper name was Abul-Ryhan. 

 He was a native of By run in the valley of the Indus, and a friend 

 of Avicenna, with whom he lived at the Arabian academy which had 

 been formed in Charezm. His stay in India, and the composition of his 

 history of that country (Tarikhi-Hind), of which Reinaud has made 

 known the most remarkable fragments, belong to the years 1030-1032. 



41 Sedillot, Materiatixpour servir a VHistoire comparee des Sciences 

 Mathematiques cli&z les Grecs et les Orientaux, t. i. pp. 50-89; also 

 in the Comptes rendus de VAcad. des Sciences, t. ii. 1836, p. 202, 

 t. xvii. 1843, pp. 163-173, t. xx. 1845, p. 1308. In opposition to this 

 opinion Biot maintains that the fine discovery of Tycho Brahe by no 

 means belongs to Abul- Wefa, and that the latter was acquainted, no/ 

 with the "variation," but only with the second part of the "evection. 

 Journal des Savans, 1843, pp. 513-532, 609-626, 719-737; 1845 

 pp. 146-166; and Comptes rendus, t. xx. 1845, pp. 1319-1323.) 



Laplace, Expos du Systewe du Monde, note 5, p. 407. 



