But there was an important interlude in the south-west of Europe, which must engage our attention as a symptom of a world-historic change in the condition of civilisation. During the course of the seventh and eighth centuries (roughly, between 622 and 750) the inhabitants of the Arabian peninsula burst the seclusion which they had held since the beginning, almost, of history, and, inspired by the zeal of the newly-founded religion of Islam, spread their influence from India to Spain, along the southern littoral of the Mediterranean. When they had once settled down, they began to recover the remnants of Græco-Roman science that had been lost on the north shores of the Mediterranean. 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. They were also acquainted with Ceylon, Java, and Sumatra, and they were the first people to learn the various uses to which the cocoa-nut can be put. Their merchants, too, visited China as early as the ninth century, and we have from their accounts some of the earliest descriptions of the Chinese, who were described by them as a handsome people, superior in beauty to the Indians, with fine dark hair, regular features, and very like the Arabs. We shall see later on how comparatively easy it was for a Mohammedan to travel from one end of the known world to the other, owing to the community of religion throughout such a vast area.