Persian Gulf to Socotra and Madagascar proves, implicitly, that as yet
there was no use of the compass.

Massoudy cut down the girth of the world even more than Ptolemy. The
latter had left an ocean to the west of Africa: the former made the
Canaries or Fortunate Islands, the limit of the known Western world,
abut upon India, the limit of the Eastern.

The first age of Arabic geography ends with Massoudy, its greatest name,
in the middle of the tenth century. The second age is summed up in the
work of the Eastern sage Albyrouny and of Edrisi, the Arabic Ptolemy
(A.D. 1099-1154), who found a home at the Christian Court of Roger of
Sicily. In the far East and West alike, in Spain and Morocco, in
Khorassan and India, Moslem science was now driven to take refuge among
strangers on the decay of the Caliphates of Bagdad and Cordova. The
Ghaznevides Mahmoud and Massoud in the first half of the eleventh
century, attracted to their Court not only Firdusi and Avicenna, but
Albyrouny, whose "Canon" became a text-book of Mohammedan science, and
who, for the range of his knowledge and the trained subtlety of his
mind, stands without a rival for his time.[14] The Spanish school, as
resulting directly in Edrisi, half Moslem, half Christian, like his
teachers, is of still more interest. One of its first traces may be
found in the Latin translation of the Arab _Almanack_ made by Bishop
Harib of Cordova in 961. It was dedicated and presented to Caliph
Hakem--one of our clearest proofs of the conscious interworking of
Catholic and Mahometan philosophy in the age of Pope Sylvester II. and
of our own St. Dunstan. A century later, on the recapture of Toledo by
Alfonso VI. (1084), an observatory was built, served by Jews and
Moslems, who had been steadily producing, through the whole of the
eleventh century, astronomical and geographical tables and dictionaries.