59. A far greater astronomer than any of those mentioned in the preceding articles was the Arab prince called from his birthplace Al Battani, and better known by the Latinised name _Albategnius_, who carried on observations from 878 to 918 and died in 929. He tested many of Ptolemy’s results by fresh observations, and obtained more accurate values of the obliquity of the ecliptic (chapter I., § 11) and of precession. He wrote also a treatise on astronomy which contained improved tables of the sun and moon, and included his most notable discovery—namely, that the direction of the point in the sun’s orbit at which it is farthest from the earth (the apogee), or, in other words, the direction of the centre of the eccentric representing the sun’s motion (chapter II., § 39), was not the same as that given in the _Almagest_; from which change, too great to be attributed to mere errors of observation or calculation, it might fairly be inferred that the apogee was slowly moving, a result which, however, he did not explicitly state. Albategnius was also a good mathematician, and the author of some notable improvements in methods of calculation.[38] 60. The last of the Bagdad astronomers was _Abul Wafa_ (939 or 940-998), the author of a voluminous treatise on astronomy also known as the _Almagest_, which contained some new ideas and was written on a different plan from Ptolemy’s book, of which it has sometimes been supposed to be a translation. In discussing the theory of the moon Abul Wafa found that, after allowing for the equation of the centre and for the evection, there remained a further irregularity in the moon’s motion which was imperceptible at conjunction, opposition, and quadrature, but appreciable at the intermediate points. It is possible that Abul Wafa here detected an inequality rediscovered by Tycho Brahe (chapter _V._, § 111) and known as the =variation=, but it is equally likely that he was merely restating Ptolemy’s prosneusis (chapter II., § 48).[39] In either case Abul Wafa’s discovery appears to have been entirely ignored by his successors and to have borne no fruit. He also carried further some of the mathematical improvements of his predecessors. Another nearly contemporary astronomer, commonly known as _Ibn Yunos_ (?-1008), worked at Cairo under the patronage of the Mahometan rulers of Egypt. He published a set of astronomical and mathematical tables, the _Hakemite Tables_, which remained the standard ones for about two centuries, and he embodied in the same book a number of his own observations as well as an extensive series by earlier Arabian astronomers. 61. About this time astronomy, in common with other branches of knowledge, had made some progress in the Mahometan dominions in Spain and the opposite coast of Africa. A great library and an academy were founded at Cordova about 970, and centres of education and learning were established in rapid succession at Cordova, Toledo, Seville, and Morocco.