Within these limits, then, geographical knowledge was confined at the end of the fourth century; limits not sharply defined, but indefinite and wavering according to ages, to the directions of conquest, and to distances from Mediterranean centres. Beyond these limits was a realm of darkness peopled by strange beings, creatures of poetic fancy or crude conjecture. Just as the wonder-land of Homer to contemporaneous eastern Greeks, was Italy, with its strange waters inhabited by very strange beasts, and Sicily, and neighboring isles, where were the Satyrs, and the gigantic one-eyed Cyclops eating milk and mutton and men, so to later teachers were the strange seas beyond. On the north was an impenetrable region of eternal ice; on the south, an equatorial zone of burning heat; a barrier of frost on the one side and of fire on the other, both equally uninhabitable to the European man, and cutting off all communication with possible habitable lands elsewhere. The burning zone, however, seems to have been a popular idea, rather than a part of the system taught by Ptolemy, who, indeed, held that Africa extended south-east and north-east toward the eastern parts of Asia, making of the Indian Ocean an immense gulf not connected with the Atlantic on the west. Strabo and other geographers who preceded Ptolemy gave Africa approximately its correct shape; traditions of its circumnavigation even were kept alive, in spite of Ptolemy's theory, influencing geographic thought not a little during the fifteenth century. Irving is of opinion, _Columbus_, vol. iii. p. 440, that modern authors consider the knowledge of the ancients concerning Africa much less extensive than has been generally supposed; but Major, _Prince Henry_, p. 89 et seq., accepts a circumnavigation of Africa in the seventh century B. C., and also Hanno's voyage far down the African coast, placing the date of the latter 570 B. C. Among the philosophers of western Europe no definite hypotheses appear to have been advanced as to the extent of land beyond the known region; as to the ideas of the Arabs and Buddhist priests concerning the matter it is difficult to determine. See _Kohl's Hist. Discov._, p. 149; _Draper's Intellectual Development_, p. 451, New York, 1872. Beyond the Fortunate Isles to the west stretched a _Mare Tenebrosum_, or Sea of Darkness, as early writers express it, separating the known western coast from the far unknown east. In this dark sea tradition planted islands at various points, reiterating the fact of their existence so often that names and locations were finally given them on maps, though the islands themselves have never yet been found. Except these fabulous islands, there was little thought of land between the coasts of Europe and Asia. Compare maps in this volume; also _George Bancroft's History of the United States_, vol. i. p. 6, Boston, 1870; _D'Avesac_, in _Nouvelles Annales des Voyages_, 1845, tom. cv. p. 293; tom. cvi. p. 47.