The Christians of Syria used Greek for their sacred language, and accordingly when the Sultans of Bagdad desired to know something of the wisdom of the Greeks, they got Syriac-speaking Christians to translate some of the scientific works of the Greeks, first into Syriac, and thence into Arabic.

In this way they obtained a knowledge of the great works of Ptolemy, both in astronomy--which they regarded as the more important, and therefore the greatest, Almagest--and also in geography, though one can easily understand the great modifications which the strange names of Ptolemy must have undergone in being transcribed, first into Syriac and then into Arabic.

We shall see later on some of the results of the Arabic Ptolemy.
The conquests of the Arabs affected the knowledge of geography in a twofold way: by bringing about the Crusades, and by renewing the acquaintance of the west with the east of Asia.

The Arabs were acquainted with South-Eastern Africa as far south as Zanzibar and Sofala, though, following the views of Ptolemy as to the Great Unknown South Land, they imagined that these spread out into the Indian Ocean towards India.

They seem even to have had some vague knowledge of the sources of the Nile.