79. Albategnius, at Aracte 23 deg. 35' 00

" 987. Aboul Wefa, at Bagdad 23 deg. 35' 00

" 995. Aboul Rihau, with a quadrant
of 25 feet radius 23 deg. 35' 00

" 1080. Arzachael 23 deg. 34' 00

Almaimon had also ascertained the size of the earth from the measurement
of a degree on the shore of the Red Sea--an operation implying true
ideas of its form, and in singular contrast with the doctrine of
Constantinople and Rome. While the latter was asserting, in all its
absurdity, the flatness of the earth, the Spanish Moors were teaching
geography in their common schools from globes. In Africa, there was
still preserved, with almost religious reverence, in the library at
Cairo, one of brass, reputed to have belonged to the great astronomer
Ptolemy. Al Idrisi made one of silver for Roger II., of Sicily; and
Gerbert used one which he had brought from Cordova in the school he
established at Rheims. It cost a struggle of several centuries,
illustrated by some martyrdoms, before the dictum of Lactantius and
Augustine could be overthrown. Among problems of interest that were
solved may be mentioned the determination of the length of the year by
Albategnius and Thebit Ben Corrah; and increased accuracy was given to
the correction of astronomical observations by Alhazen's great discovery
of atmospheric refraction. Among the astronomers, some composed tables;
some wrote on the measure of time; some on the improvement of clocks,
for which purpose they were the first to apply the pendulum; some on
instruments, as the astrolabe. The introduction of astronomy into
Christian Europe has been attributed to the translation of the works of
Mohammed Fargani. In Europe, also, the Arabs were the first to build
observatories; the Giralda, or tower of Seville, was erected under the
superintendence of Geber, the mathematician, A.D. 1196, for that
purpose. Its fate was not a little characteristic. After the expulsion
of the Moors it was turned into a belfry, the Spaniards not knowing what
else to do with it.

[Sidenote: Europe tries to hide its obligations to them.] I have to
deplore the systematic manner in which the literature of Europe has
contrived to put out of sight our scientific obligations to the
Mohammedans. Surely they cannot be much longer hidden. Injustice founded
on religious rancour and national conceit cannot be perpetuated for
ev