d not come under his
notice. These tables were considered in Egypt to be of equal value to
those of the astronomer Yabya bin Ali Mansur, who had in A.D. 830, by
order of the Khalif Mamun, undertaken astronomical observations both
at Baghdad and Damascus. Ibn Yunis spent his life in the preparation
of astronomical tables and in casting horoscopes, for it must be
remembered that with the Muslims astronomy and astrology were
synonymous, and their most learned astronomers were also their most
skilful astrologers. His character for honesty was highly esteemed,
and he was also well versed in other sciences, and displayed an
eminent talent for poetry. He died A.D. 1009, and is not to be
confounded with his father, Ibn Yunis, the historian, who died A.D.
958.

Yet another name must be mentioned, viz., the Spanish-Arab astronomer
Ibn Abd-ar-Rahman Es-Zerkel, Europeanized as Arzachal. He first
resided at Toledo, at the court of its sovereign, Mamun, for whom he
made an astrolabe, which he called in his honour the Mamunian. He then
went to Seville, where he wrote for Motamid bin Abbad (A.D. 1069-1091)
a treatise on the use of certain instruments. During his residence at
Toledo he constructed two clepsydras, the waters of which decreased
and increased according to the waning and growing of the moon, and
these two basins were destroyed only in A.D. 1133 by Alphonse VI.,
when he took Toledo. Arzachal left a work on eclipses, and on the
revolution of years, as well as the tables of the sky, to which the
name of Toledan tables have been given. His writings, but especially
the last, which must have been consulted by the editors of the
Alphonsine tables, were never translated, and exist only in manuscript
in libraries where but few scholars can consult them. Arzachal made
many observations in connection with the sun, and was also the
inventor of the astronomical instrument called after his name,
Zerkalla. He died A.D. 1080.

Before leaving this subject it may be mentioned that Makkari, in his
great encyclopaedia of Spain, enumerates fifteen astronomers of
Andalusia, all more or less known in their time. Also that
Bedei-ul-Astrolabi and Ibn Abdul-Rayman distinguished themselves as
makers of astronomical instruments, and inventors of new ones. While
Arzachal was the greatest representative of Arab astronomy in the West,
Umar Khayam, the astronomer, mathematician, freethinker, and poet, was
its greatest representative in the East, in Per