We have seen that, as a result either of the poetic fancy or of the actual discovery of the ancients, various islands were traditionally located in the Atlantic. Most of them undoubtedly owed their existence to the natural tendency of man to people unknown seas with fabulous lands and beings, "Il est si naturel à l'homme de rêver quelque chose au-delà de l'horizon visible," observes Humboldt. For a full account of the history and location of these islands, "dont la position est encore plus variable que le nom," and the important part played by them in ancient and middle-age geography, see _Humboldt_, _Exam. Crit._, tom. ii. pp. 156-245, and _Kunstmann_, _Entdeckung Am._, pp. 6 et seq., and 35-37. In the fifteenth century, with the revival of maritime enterprise, came a renewal and multiplication of the old fables. Monastic scholars, by their continued study of the old writers, by their attempts to reconcile ancient geography with fabulous events in the lives of the saints, and by their inevitable tendency to exaggeration, had contributed largely to their preservation. Still, throughout the preceding period, the belief in the existence of such islands had been vague and hypothetical; but when the actual existence of numerous islands in the western ocean was proved, and the Canary, Madeira, Azore, and Cape Verde groups were discovered and explored, the old ideas were naturally revived and confirmed, and with them rose a desire to rediscover all that had been known to the ancient voyagers. The reported wonders of the fabulous isles, having on them great and rich cities, were confidently sought in each newly found land, and not appearing in any of them, the islands themselves were successively located farther and farther to the west, out in the mysterious sea, to be surely brought to light by future explorations. And of a truth, this wondrous western empire was subsequently brought to light; peoples and cities were found, but beyond the limits within which the wildest dreams of their discoverers had ever placed them. On this foundation not a few speculators build a theory that America was known to the ancients. The chief of the hypothetical isles were San Brandan, Antilia, and the Island of the Seven Cities; their existence was firmly believed in, and they were definitely located on maps of the period. San Brandan is said to have been visited by the saint whose name it bears in the sixth century. It was at first located far north and west of Ireland, but gradually moved southward until at the time of Columbus' first voyage it is found nearly in the latitude of Cape Verde. To the inflamed imagination mirage is solid earth, or sea, or a beautiful city; an island which was long supposed to be visible from Madeira and the Canaries had something to do with the location of this island of the saint, and of the others.