In the middle of the thirteenth and the beginning of the fourteenth centuries, the Venetian Marco Polo[25] and the Englishman Mandeville[26] awakened the curiosity of Europe with respect to the remote parts of the earth. Wise and discerning men selected the more valuable portions of their observations; ideas were enlarged, and a desire for more perfect information excited a thirst for discovery. While this spirit was gaining strength in Europe, the wonderful powers of the magnet were revealed to the Western World.[27] The invention of the mariner's compass aided and extended navigation more than all the experience and adventure of preceding ages: the light of the stars, the guidance of the sea-coast, were no longer necessary; trusting to the mysterious powers of his new friend, the sailor steered out fearlessly into the ocean, through the bewildering mists or the darkness of night. The Spaniards were the first to profit by the bolder spirit and improved science of navigation. About the beginning of the fourteenth century, they were led to the accidental discovery of the Canary Islands,[28] and made repeated voyages thither, plundering the wretched inhabitants, and carrying them off as slaves.[29] Pope Clement VI. conferred these countries as a kingdom upon Louis de la Cerda, of the royal race of Castile; he, however, was powerless to avail himself of the gift, and it passed to the stronger hand of John de Bethancourt, a Norman baron.[30] The countrymen of this bold adventurer explored the seas far to the south of the Canary Islands, and acquired some knowledge of the coast of Africa. The glory of leading the career of systematic exploration belongs to the Portuguese:[31] their attempts were not only attended with considerable success, but gave encouragement and energy to those efforts that were crowned by the discovery of a world: among them the great Genoese was trained, and their steps in advance matured the idea, and aided the execution of his design. The nations of Europe had now begun to cast aside the errors and prejudices of their ancestors. The works of the ancient Greeks and Romans were eagerly searched for information, and former discoveries brought to light.[32] The science of the Arabians was introduced and cultivated by the Moors and Jews, and geometry, astronomy, and geography were studied as essential to the art of navigation.