The result of these studies was a complete acquaintance with the geographical knowledge of the day, with the greater part of what I have thus far epitomized, the doings of the Northmen excepted. From all this he knew of the earth's sphericity; he believed that the larger part of the world's surface was dry land; that the land known to Ptolemy extended over at least 180 degrees, or half the circumference of the globe, that is, from the Canaries to the Ganges; he knew that by later travels the eastern limit of geographical knowledge had been moved much farther east, even to Cathay; he believed that far out in the ocean lay the island of Zipangu; he knew that some eight or ten degrees had been added on the west by the discovery of the Azores; he believed that at most only one third of the circumference remained to be navigated; that this space might naturally contain some islands available as way stations in the voyage; that the explorations in the East were very indefinite, and consequently Asia might, and probably did, extend farther east than was supposed; that Ptolemy's figures were not undisputed—Marino making the distance from the Canaries to the Ganges 225 degrees instead of 180, while another geographer, Alfragano, by actual measurement, made each degree about one sixth smaller than Ptolemy, thus reducing the size of the earth, and with it the remaining distance to India; that several ancient writers—see quotations from Aristotle, Strabo, Seneca, et al., in _Humboldt_, _Exam. Crit._, tom. i. pp. 38, 61, 98 et seq.—had pronounced the distance to India very short, and had affirmed that it might be navigated in a few days; and finally that other scholars, as Toscanelli, had arrived at the same conclusions as himself, possibly before himself. _Cartas de Pablo Toscanelli, Físico Florentin, á Cristobal Colon y al Canónigo Portugues Fernando Martinez, sobre el descubrimiento de las Indias_, in _Navarrete_, tom. ii. pp. 1-4; _Muñoz_, _Hist. Nuevo Mundo_, pp. 48-9. See also, on Columbus' motives, _Irving's Columbus_, vol. i. pp. 42-51, and vol. ii. p. 148; _Muñoz_, _Hist. Nuevo Mundo_, pp. 45-7; _Humboldt_, _Exam. Crit._, tom. ii. pp. 324-9; _Stevens' Notes_, p. 28; _Major's Prince Henry_, pp. 347-52; _Kunstmann_, _Entdeckung Am._, p. 74. Many of these conclusions were erroneous, being founded on an incorrect idea of longitude; but this reduction of the earth's size was an error most fortunate for discovery, inasmuch as with a correct idea of the distance to be traversed, and with no suspicion of an intervening continent, such an expedition as that of the Genoese would not have been undertaken at the time. Such were the ideas and aspirations of Columbus before his undertakings; later in life a theologic mysticism took possession of his mind, and his success was simply a fulfillment of divine prophecy in which cosmographical realities went for nothing. See _Cartas de Don Cristobal Colon_, in _Navarrete_, tom. i. p. 330.