As the Roman Empire broke up, geographical knowledge naturally suffered, and Africa shared in this loss. But a considerable recovery was effected through the work of the Arabs, to whom the Infant Henry owed much. Confining our attention to Continental exploration, we may remark among other particulars: (1) That the Arab migration[80] to the East coast beyond Guardafui in the eighth century began the extension of Moslem trade-colonies, which at last reached Sofala. (2) That the coast near Madagascar, as well as that island itself, seems to have been known to the great Arab traveller and geographer Masudi ("Massoudy") in the tenth century. (3) That the same writer considered the Atlantic or Western Ocean unnavigable, but that even he preserves a record of one Arab voyage thereon.[81] (4) That Edrisi, in the twelfth century, records another voyage which touched the African mainland a good distance beyond the Straits of Gibraltar.[82] (5) That Ibn Said, in the thirteenth century, relates a discovery of Cape Blanco.[83] (6) That overland communication between the Barbary States and the negroes of the Sudan was originated by the Arabs, as a regular line of commerce, probably from the eleventh century at least. [Footnote 80: This migration led to the foundation of Magadoxo, 909-951, and of Kilwa, 960-1000; later on of Malindi, Mombasa, and Sofala. See Krapf, _Travels and Missionary Labours_, etc., p. 522; G. P. Badger, _Imams ... of Oman_, p. xiii; El-Belâdzory, _Futûh-el-Buldân_ (Ed. Kosegarten), pp. 132-135. The immigrants came from the Red Sea and Syria, according to Dr. Krapf, from Oman and the Persian Gulf according to Badger (though Krapf admits a later Persian element as well). This was the migration of the "Emosaids" ('Ammu-Sa'îd, or People of Sa'îd?). They, in one tradition, claimed to be the clan of Said, grandson of Ali; "a mythical personage," according to Badger, who substitutes "Sa'îd, grandson of Julánda" the Azdite; the latter, in this 'Omâni migration, was accompanied by his brother Suleimân. The traditional date is A.D. 740, and onwards.] [Footnote 81: Masudi, ch. 12 of the _Meadows of Gold_. The adventurer was Khosh-Khash, the "young man of Cordova," who returned with great riches, from Guinea (?).] [Footnote 82: See the section of this Introduction upon the Atlantic Islands, pp. lxxv-lxxvii. Edrisi's Maghrurin or Wanderers probably sailed from and returned to Lisbon before 1147, the date of the final Christian capture of that city, and touched the African mainland at a point over against Madeira.]