Several years passed, when Prince Enrique dispatched an experienced seaman, Captain Gilianez, charging him to pass the dreaded Cape of Bojador. Gilianez proceeded thirty leagues beyond it, but dreaded to go farther. He turned back, therefore, satisfied at having performed his commission. Next year he proceeded another twelve leagues to the south, to a part of the coast where a number of sea-wolves, or rather seals, were taken. Thus, year by year, expeditions were sent out, each gaining, step by step, a knowledge of the African coast, until in the reign of Dom Joao the Second, in 1486, Bartholomew Diaz sailed with three ships, resolved to proceed farther than any of his predecessors. Touching at several places on the coast, he at length reached an until then unknown cape, to which he gave the name of Il Cabo Tormentoso, or the Cape of Storms, on account of the furious gales and heavy seas he there encountered. The seamen, frightened by the weather, and believing that Nature had set a barrier against their further progress, insisted on returning, although Diaz was convinced that he had reached the southern end of the continent. On the arrival of Diaz at Lisbon, the King, delighted with his discovery, gave to the cape the name of Cabo de Boa Esperanza, or Cape of Good Hope. Dom Joao had in the meantime dispatched overland two envoys with directions to visit the kingdom of Prester John, and was preparing to send out an expedition by sea, when death put a stop to his projects. His successor, Dom Manoel, resolved, however, to carry them out, but before doing so he set to work to obtain all the information in his power. On consulting a Jewish astronomer, Zacato, he learned the cause of the ill success many of the expeditions had met with. He could not understand why some of his captains had in certain latitudes encountered storms, while others had passed through them in fine weather. The Jew suggested that as the ocean is very large, in some parts it is summer and in others winter, and that his ships following the same course, some might arrive in a region where winter prevails and meet with storms, and when the other reaches the same latitude it may be summer, and perfectly fine weather be enjoyed. Thus, he continued, when navigators have obtained more experience, they will know when to sail so as to obtain summer during the whole of the voyage, and will then be able to come from and go to the Cape of Good Hope without difficulty.