5. This was the high-water mark of knowledge concerning the sources of the White Nile for something like eighteen hundred years. Information on the subject in the interval began to grow less rather than more. The stories of the Nile lakes were, however, revived after the Arab invasions of northeast Africa in the twelfth and thirteenth centuries, and were communicated to the European world of the Renaissance through the intermediary of the Saracen writers of Sicily, the theologians of Rome, and the merchants of Venice. CHAPTER VI PORTUGAL AND ABYSSINIA Portugal was created by the crusading spirit. The King of Castile, who had become the leading prince in the northern half of Spain, despatched a young Burgundian adventurer, Count Henry, to advance on the Douro from Galicia (in the northwest corner of the Spanish peninsula) and to drive the Moors into the sea,--either the Atlantic Ocean or the Straits of Gibraltar. Count Henry drove them at any rate half-way down that western coastland of the Spanish peninsula which we now call Portugal.[14] Lisbon was only eventually conquered from the Moors by the help of a large party of English volunteers who stopped to aid in this struggle with the Moslem while on their way to a Crusade in the Holy Land. Steadily, bit by bit, Count Henry and his successors, the kings of Portugal, drove the Moors southward into and out of the little province of Algarve, and then, flushed with continuous success, crossed the Straits, attacked them in Morocco, and added a large part of the present Empire of Morocco to the possessions of the Portuguese Crown.[15] These brilliant successes awoke a great spirit of discovery in Portugal,--a spirit fomented and encouraged by that noble and far-sighted man, Prince Henry the Navigator, who had himself shared in the Morocco wars. Rapidly the limits of the Portuguese explorations extended. First they rounded Cape Bojador on the northwest coast of Africa. Then they reached Sierra Leone, the gold coast, Benin (where they powerfully affected native art and industry), the Niger Delta, the Cameroons, the Congo, Angola, and the Cape of Good Hope. Once having passed this promontory, whence they had once retired baffled, their great navigator, Vasco da Gama, carried on the exploration of the coasts of Africa eastward and northward to Mombasa and thence to India. Succeeding vessels explored the Red Sea, and the expeditions they conveyed attempted to get into touch with Abyssinia, where, according to the rumours brought home by crusaders and Italian merchants from Egypt, there lay a Christian country ruled by a pious monarch, John the Priest.[16] But before ever Vasco da Gama had rounded the Cape of Good Hope, the Portuguese, by contact with the Moors, had heard of Arab settlements on the East Coast of Africa, and of the insular character of the great continent. Their government, therefore, in 1486 despatched on a journey to Egypt, India, and eastern Africa Pero de Covilhaõ to