ich had long been known. The merit which belongs to
Columbus is, not for the first observance of the existence of the
declination, which is given, for example, upon the map of Andrew Bianca,
in 1436, but for the remark which he made on the 13th of September,
1492, that about two degrees and a half to the east of the Island of
Corvo the magnetic variation changed, and that it passed over from
northeast to northwest. This discovery of a magnetic line without any
variation indicates a remarkable epoch in nautical astronomy. It was
celebrated with just praise by Oviedo, Casas, and Herrera. If with Livio
Sanuto we ascribe it to the renowned mariner Sebastian Cabot, we forget
that his first voyage, which was undertaken at the expense of some
merchants of Bristol, and which was crowned with success by his touching
the main-land of America, falls five years later than the first
expedition of Columbus.--Humboldt's _Cosmos_, vol. ii., p. 318; Las
Casas, _Hist. Ind._, lib. i., cap. 6.]

[Footnote 45: "In sailing toward the West India Islands birds are often
seen at the distance of two hundred leagues from the nearest
coast."--Sloane's _Nat. Hist. of Jamaica_, vol. i., p. 30.

Captain Cook says, "No one yet knows to what distance any of the Oceanic
birds go to sea; for my own part, I do not believe that there is any one
of the whole tribe that can be relied on in pointing out the vicinity of
land."--_Voyage toward the South Pole_, vol. i., p. 275.

The Portuguese, however, only keeping along the African coast and
watching the flight of birds with attention, concluded that they did not
venture to fly far from land. Columbus adopted this erroneous opinion
from his early instructors in navigation.]

[Footnote 46: "Puesto que el amirante a los diez de la noche vio lumbre
... y era como una candelilla de cera que se alzaba y levantaba, lo cual
a pocos pareciera ser indicio de tierra. Pero el amirante tuvo por
cierto estar junto a la tierra. Por lo qual quando dijeron la 'Salve'
que acostumbran decir y cantar a su manera todos los marineros, y de
hallan todos, vogo y amonestolos el amirante que hiciesen buena guarda
al castillo de proa, y mirasen bien por la tierra."--_Diar. de Colon.
Prem. Viag. 11 de Oct._]

[Footnote 47: "Let those who are disposed to faint under difficulties,
in the prosecution of any great and worthy undertaking, remember that
eighteen years elapsed after the time that Columbus conceived his
enterprise before h