oasting voyages.]
If Columbus failed in his attempt to reach India by sailing to the west,
Vasco de Gama succeeded by sailing to the south. He doubled the Cape of
Good Hope, and retraced the track of the ships of Pharaoh Necho, which
had accomplished the same undertaking two thousand years previously. The
Portuguese had been for long engaged in an examination of the coast of
Africa under the bull of Martin V., which recognised the possibility of
reaching India by passing round that continent. It is an amusing
instance of making scientific discoveries by contract, that King
Alphonso made a bargain with Ferdinand Gomez, of Lisbon, for the
exploration of the African coast, the stipulation being that he should
discover not less than three hundred miles every year, and that the
starting-point should be Sierra Leone.

[Sidenote: Papal confines of Spain and Portugal.] We have seen that a
belief in the immobility of the line of no magnetic variation had led
Pope Alexander VI. to establish a perpetual boundary between the Spanish
and Portuguese possessions and fields of adventure. That line he
considered to be the natural boundary between the eastern and western
hemispheres. An accurate determination of longitude was therefore a
national as well as a nautical question. Columbus had relied on
astronomical methods; Gilbert at a subsequent period proposed to
determine it by magnetical observations. The variation itself could not
be accounted for on the doctrine vulgarly received, that magnetism is an
effluvium issuing forth from the root of the tail of the Little Bear,
but was scientifically, though erroneously, explained by Gilbert's
hypothesis that earthy substance is attractive--that a needle
approaching a continent will incline toward it; and hence that in the
midst of the Atlantic, being equally disturbed by Europe and America, it
will point evenly between both.

[Sidenote: News that Africa might be doubled.] Pedro de Covilho had sent
word to King John II., from Cairo, by two Jews, Rabbi Abraham and Rabbi
Joseph, that there was a south cape of Africa which could be doubled.
They brought with them an Arabic map of the African coast. This was
about the time that Bartholomew Diaz had reached the Cape in two little
pinnaces of fifty tons apiece. He sailed August, 1486, and returned
December, 1487, with an account of his discovery. Covilho had learned
from the Arabian mariners, who were perfectly familiar with the east
coast, tha