ASTRONOMY IN ANCIENT NATIONS of Hipparchus, but varying considerably and irregularly. Ibn Jūnis, who quotes this. adds that he has himself found 5° 3' or 5° 8', while other observers are said to have found from 4 58' to 4° 45'.¹ Want of perseverance and of accurate instruments caused them to miss a remarkable discovery, that of the variation of the lunar inclination. 18 Abu 'I Wefa and his Almagest 3 But an even more remarkable discovery has been claimed for an Arabian astronomer. In 1836 the younger Sedillot announced that he had found the third inequality, the variation, distinctly announced in Abu '1 Wela's Almagest. A fierce controversy raged for a number of years as to the reality of this discovery, Sedillot alone defending his hero with desperate energy and refusing to listen to any arguments, while Biot, Libri and others as strenuously maintained that Abu '1 Wefa simply spoke of the second part of the evection, the prosneusis of Ptolemy. The fight had died out when, in 1892. Chasles suddenly took up the cudgels for Sedillot and pointed out what seemed to him to be some contradictions in Ptolemy's statement. Nobody answered this until Bertrand did so in 1871; he called attention to several inaccuracies in the text of Abu '1 Wefa as we possess it now, and also showed that Abu '1 Wefa did not add his "mohazat" to the prosneusis, the latter not being included in his "second anomaly." It is unnecessary to enter into a more detailed account of the controversy; but to show that any weapon was considered good enough with which to defend Abu '1 Wefa, it may be mentioned that Sedillot and Chasles tried to prove that Tycho Brahe must have copied his discovery from Abu '1 Wefa, because he calls it hypothesis redintegrata. Tycho used this same phrase in speaking of his own planetary system, which he most emphatically claimed as 1. Sedillot, Prolegomenes, p. xxxviii. Materiaux pour servir a l' hist. des scienc es chez les Grecs et les Orientaux, T. I. p. 283. The sons of Musa ben Sakir (about 850) seem to have been the first to find a value differing from that of the ancients. Abraham ben Chija, a Jewish writer who lived about A. D. 1100 says that Ptolemy found 50, but that according to the opinion of the Ishmaelites it is 41° (Sphaera mundi. Basle. 1546 p. 102). 2. Lettre a M. Sedillot sur la question de la variation lunaire, Paris, 1862, 15 pp. 4° and Comptes Rendus, vol. 54, p. 1002. 3. Comptes Rendus. vol. 73, pp. .581, 756, 889; Journal des Savants. 11 Oct. 1871.
