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in the tenth century, seems to have discov-
ered the moon’s ”variation.” Meanwhile the
Moors were leaders of science in the west,
and Arzachel of Toledo improved the solar
tables very much. Ulugh Begh, grandson
of the great Tamerlane the Tartar, built a
fine observatory at Samarcand in the fif-
teenth century, and made a great catalogue
of stars, the first since the time of Hip-
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