(1.) Ptolemy's "Habitable Quarter" of the world, amounting to just half the longitude of the globe, was literally accepted by the Moslem world, as it accepted the Pentateuch from the moment when it began its study of science at the Court of Almamoun (813-833). But, as the conquests of the Caliphs disclosed districts in the east far beyond Ptolemy's limits, it was necessary, in case of keeping his data for the whole, to compress the part which alone was to be found fully described in his chart: "On the west, unhappily, there were no countries newly discovered to compensate for this abridgment." By Massoudy's time,—by the tenth century,—fact and theory were thus hopelessly at variance.
(2.) On the shape of Africa, the mass of Arabic opinion confirmed Ptolemy, but among the more enlightened there is traceable from Massoudy's time a tendency either to react towards Strabo's partly agnostic position, or to invent some new theory rather more in harmony with the known facts. That is, either their later map-makers cut off Africa at Cape Non or Bojador and Cape Guardafui, and gave away the rest to the "Green Sea of Darkness," or, like Massoudy, they sketched a great Southern Continent, divided from Africa by a narrow channel, which connected the Western Ocean with the Sea of Habasch—of Abyssinia or India. In either case Africa was left an island.
(3.) The words "Gog and Magog" from Jeremiah, describing the nomades of Central Asia, appear in the Koran as Yadjoudj and Madjoudj. The complete story, in the tenth century and in Edrisi's day, connects them with Alexander the Great, who is also found in the Koran as Doul-Carnain, and with the Wall of China. "When the Conqueror," said the Arabs, "reached the place near where the sun rose, he was implored to build a wall to shut off the marauders of Yadjoudj and Madjoudj from the rich countries of the South." So he built a rampart of iron across the pass by which alone Touran joined Iran, and henceforth Turks and Tartars were kept outside. Till the Arabs reached the Caucasus, they generally supposed this to answer to Alexander's wall; when facts dispelled this theory, the unknown Ural or Altai Mountains served instead; finally, as the Moslems became masters of Central Asia, the Wall of China, beyond the Gobi desert, alone satisfied the conditions of shadowy but historic grandeur, beyond all practical danger of verification.
(4.) In striking contrast with the steady advance of Arabic exploration and trade in the Eastern Sea is the Moslem horror of the Western Ocean beyond Europe and Africa, the "Green Sea of Darkness" or the Atlantic. And what we have to note is that they imparted much of this paralysing cowardice to the Christian nations. Only the Northmen of Scandinavia, living a life apart, and forced to make their way over the wild North Sea, were untouched by this southern superstition, and ventured across the ocean by the Färoes, Iceland, and Greenland, to the coast of Labrador.
The doctors of the Koran indeed thought that a man mad enough to embark for the unknown, even on a coasting voyage, should be deprived of civil rights. Ibn Said goes further, and says no one has ever done this: "whirlpools always destroy any adventurer." As late as the generation immediately before Henry the Navigator, about a.d. 1390, another light of Moslem science declared the Atlantic to be "boundless, so that ships dare not venture out of sight of land, for even if the sailors knew the direction of the winds, they would not know whither those winds would carry them, and as there is no inhabited country beyond, they would run a risk of being lost in mist, fog, and vapour. The limit of the West is the Atlantic Ocean."
This was the final judgment of the Arabic race and its subject allies upon the western limits of the world, and in two ways they helped to fix this belief, derived from the timid coasting-traders of the Roman Empire on Greek and Latin Christendom. First, the Spanish Caliphate cut off all access to the Western Sea beyond the Bay of Biscay, from the eighth to the twelfth centuries. Not till the capture of Lisbon in 1147, could Christian enterprise on this side gain any basis, or starting-point. Not till the conquest of the Algarve in the extreme south-west of the peninsula, at the end of the twelfth century, was this enterprise free to develop itself. Secondly, in the darkest ages of Christian depression, the seventh, the eighth, the ninth, the tenth centuries, when only the brief age of Charlemagne offered any chance of an independent and progressive Catholic Empire in the west, the Arabs became recognised along with the Byzantines as the main successors of Greek culture. The science, the metaphysic, the abstract ideas of these centuries came into Germany, France, and Italy from Cordova and from Bagdad, as much as from Byzantium. And on questions like the South Atlantic or Indian Ocean, or the shape of Africa,—where Islam had all the field to itself, and there was no positive and earlier discovery which might contradict a natural reluctance to test tradition by experiment—Christendom accepted the Arabic verdict with deference.
In the same way, on still more difficult points, such as the theory of a canal from the Caspian to the Black Sea, or from the Caspian to the Arctic circle, or from the Black Sea to the Baltic, Paris and Rome and Bologna and Oxford accepted the Arabic descriptions.
It has been necessary for us to attend to the defects of Arabic geography, in order to understand how in the long Saracen control of the world's trade routes and of geographical tradition, science and seamanship were so little advanced. Between Ptolemy and Henry of Portugal, between the second and the fifteenth centuries, the only great extension of men's knowledge of the world was: (1) in the extreme north, where the semi-Christian, semi-Pagan Vikings reached perhaps as far as the present site of New York and founded, on another side, the Mediæval Kingdom of Russia; (2) on the south-east coast of Africa, from Cape Guardafui to Madagascar, which was opened up by the trading interest of the Emosaid family (800-1300); (3) in the far east, in Central and Further Asia, by the discoveries of Marco Polo and the Friar preachers following on the tracks of the earlier Moslem travellers. The first of these was a Northern secret, soon forgotten, or an abortive development, cut short by the Tartars; the second was an Arabic secret, jealously guarded as a commercial right; the third alone added much direct new knowledge to the main part of the civilised world.
But throughout their period of commercial rule from the eighth to the twelfth centuries, the Arabs took a keen interest in land traffic, conquest, and exploration. They were of small account at sea; it took them some time to turn to their own purposes Hippalus' discovery (in the second century a.d.) of the monsoon in the Indian Ocean; but, on land, Moslem travellers and writers—generally following in the wake of their armies, but sometimes pressing on ahead of them—did not a little to enlarge the horizon of the Mohammedan world, though it was not till Marco Polo and the Franciscan missionaries of the thirteenth and fourteenth centuries, that Christian Europe shared in this gain.
As the early Caliphs conquered, they made surveys of their new dominions. Thus after Tarik and Mousa had overrun Spain, Walid at Damascus required from them an account of the land and its resources. The universal obligation of the Mecca pilgrimage compelled every Moslem to travel once in his life; and many an Arab, after the Caliphate was settled in power from the Oxus to the Pyrenees, journeyed to and fro with the joy of a master going over vast estates, shewing his dreaded turban to subjects of every nation.