Marco Polo told of great cities in China where men traded in the costly wares of the East, and where silk was abundant and cheap. He described from hearsay Japan as an island fifteen hundred miles from the mainland. Its people, he said, were white, civilized, and wondrously rich. The palace of the emperor of Japan was roofed with gold, its pavements and floors were of solid gold, laid in plates two fingers thick. REASONS FOR FINDING A SEA ROUTE TO THE EAST. Tales of such great wealth made Europeans more eager than ever to reach the East. Marco Polo had shown that it was possible to sail past India, through the islands, to the eastern coast of Asia. When printing was invented his account was printed, and the copy of that book which Columbus owned is still preserved. Upon its margins Columbus wrote his own opinions about geography. Other travelers besides the Polos returned with similar tales of the East. Soon, however, all chance to go there by way of the land was lost, because the Mongol emperors were driven out of China and the new rulers would not permit Europeans to enter the country. The ordinary caravan routes to the East were also closed not long afterwards. In 1453 the Turks captured Constantinople, drove away the Italian merchants, and prevented European sailors from reaching the Black Sea. Fifty years later the Turks seized Egypt and closed that route also. Fortunately before this happened a better route had been discovered. THE PORTUGUESE SAILORS. During the Middle Ages the Portuguese princes fought to recover Portugal from the Moors. When this was done they were eager to cross the straits and attack the Moors in Africa. Prince Henry of Portugal made an expedition to Africa and returned with the desire to know more about the coast south of the point beyond which European sailors dared not venture. Sailors were afraid of being lost in the Sea of Darkness or killed by the heat of the boiling tropics. [Illustration: DANGERS OF THE "SEA OF DARKNESS" From an old picture] From his love of exploring the seas Prince Henry has been called "The Navigator." He took up his residence on a lonely promontory in southern Portugal, and gathered about him learned men of all peoples, Arabian and Jewish mathematicians, and Italian mapmakers. Captains trained in this new school of seamanship were sent into the southern seas. Each was to sail farther down the western coast of Africa than other captains had gone. Before Prince Henry died in 1460 his captains had passed Cape Verde, and ten years later they crossed the equator without suffering the fate which men had once feared. But they were discouraged when they found that beyond the Gulf of Guinea the coast turned southward again, for they had hoped to sail eastward to Asia.