5 Catalan map, 1375 58 6 Nicolay, 1560 62 7 Catalan map, about 1480 64 8 World map in portolan atlas, about 1508 (Egerton MS. 2803) 74 9 Desceliers, 1546 76 10 Ortelius, 1570 77 11 Ptolemy, 1513 82 12 Prunes, 1553 88 13 Coppo, 1528 97 14 Bishop Thorláksson, 1606 98 15 Map of the early Norse Western and Eastern Settlements of Greenland, 1:6,400,000 103 16 Clavus, 1427 104 17 Donnus Nicolaus Germanus, after 1466 105 18 Sigurdr Stefánsson, 1590 107 19 Zeno, 1558 126 20 Beccario, 1435 152 21 Pareto, 1455 158 22 Benincasa, 1482 160 23 Representation of Corvo on fourteenth- and fifteenth-century maps as compared with its present outline 172 24 Buss Island, probably 1673 176 25 Bianco, 1436 179 CHAPTER I INTRODUCTION We cannot tell at what early era the men of the eastern Mediterranean first ventured through the Strait of Gibraltar out on the open ocean, nor even when they first allowed their fancies free rein to follow the same path and picture islands in the great western mystery. Probably both events came about not long after these men developed enough proficiency in navigation to reach the western limit of the Mediterranean. We are equally in lack of positive knowledge as to what seafaring nation led the way.