This indifference continued until the close of the fifteenth century.
Even then there was no scientific inducement. The inciting motives were
altogether of a different kind. They originated in commercial rivalries,
and the question of the shape of the earth was finally settled by three
sailors, Columbus, De Gama, and, above all, by Ferdinand Magellan.

The trade of Eastern Asia has always been a source of immense wealth to
the Western nations who in succession have obtained it. In the middle
ages it had centred in Upper Italy. It was conducted along two lines--a
northern, by way of the Black and Caspian Seas, and camel-caravans
beyond--the headquarters of this were at Genoa; and a southern, through
the Syrian and Egyptian ports, and by the Arabian Sea, the headquarters
of this being at Venice. The merchants engaged in the latter traffic had
also made great gains in the transport service of the Crusade-wars.

The Venetians had managed to maintain amicable relations with the
Mohammedan powers of Syria and Egypt; they were permitted to have
consulates at Alexandria and Damascus, and, notwithstanding the military
commotions of which those countries had been the scene, the trade was
still maintained in a comparatively flourishing condition. But the
northern or Genoese line had been completely broken up by the
irruptions of the Tartars and the Turks, and the military and political
disturbances of the countries through which it passed. The Eastern trade
of Genoa was not merely in a precarious condition--it was on the brink
of destruction.

The circular visible horizon and its dip at sea, the gradual appearance
and disappearance of ships in the offing, cannot fail to incline
intelligent sailors to a belief in the globular figure of the earth.
The writings of the Mohammedan astronomers and philosophers had given
currency to that doctrine throughout Western Europe, but, as might be
expected, it was received with disfavor by theologians. When Genoa was
thus on the very brink of ruin, it occurred to some of her mariners
that, if this view were correct, her affairs might be re-established.
A ship sailing through the straits of Gibraltar westward, across the
Atlantic, would not fail to reach the East Indies. There were apparently
other great advantages. Heavy cargoes might be transported without
tedious and expensive land-carriage, and without breaking bulk.

Among the Genoese sailors who entertained these views was Christopher
Co