The promptings which urged forward this navigator to the execution of his great enterprise may be stated as follows: The success of the Portuguese in long voyages down the African coast suggested to his mind, soon after 1470, that if they could sail so far south, another might sail west with the same facility and perhaps profit. Says his son: "Estando en Portugal, empeçó à congeturar, que del mismo modo que los Portugueses navegaron tan lejos al Mediodia, podria navegarse la buelta de Occidente, i hallar tierra en aquel viage." _Colon_, _Hist. del Almirante_, in _Barcia_, tom. i. p. 4; edition of Venetia, 1709, pp. 22-3; _Humboldt_, _Exam. Crit._, tom. i. p. 12; _Navarrete_, _Col. de Viages_, tom. i. p. lxxix; _Herrera_, _Hist. Gen._, dec. i. lib. i. cap. 1-7. His ardent imagination once seized with this idea, every nook and corner of geographical knowledge was searched for evidence to support his theory. By intercourse with other navigators he learned that at different times and places along the western coasts of Europe and Africa, objects apparently from unknown western lands had been washed ashore, suppositionally by the wind, really by the Gulf Stream or other oceanic currents. _Humboldt_, _Exam. Crit._, tom. ii. p. 249. Though well aware of existing rumors of islands seen at different times in the western ocean, it was not upon these, if any such there were, that he built his greatest anticipations of success. In the writings of the ancients he found another stimulant. Filled with fervent piety and superstitious credulity, he pored over every cosmographical work upon which he could lay his hands, as well the compilations of antiquated notions, such as the _Imago Mundi_ of Pierre D'Ailly, or the more modern travels of Marco Polo and Sir John Mandeville. _Colon_, _Hist. del Almirante_, in _Barcia_, tom. i. p. 4 et seq.; _Major's Prince Henry_, pp. 349, 352; _Humboldt_, _Exam. Crit._, tom. i. pp. 46, 60; _Kunstmann_, _Entdeckung Am._, pp. 74-6. [Sidenote: EVOLUTION OF THE GRAND CONCEPTION.]