Portuguese participation in the slave trade 121sentence for adultery, felonies or magical reasons. It was also a more refined
way of getting rid of hot-heads and undesirables than by putting them to
death. The traders were therefore to find the same ease of exchange all round
the coast of Africa.
The Portuguese, moreover, were also reaping the benefit of the much more
long-standing internal trade which had been set up by the Arabs. Trans-Saharan
trade started from the Sudan, which furnished gold and slaves taken by the
Islamized Sahel peoples in forays on the area to the south. One route was via
the staging-post of Hoden in the Sahara, where the captives were split up : some
were bound for Barco, on the coast of Cyrenaica, whence they were sent on to
Tunis and Sicily, while others were taken to Arguin to be sold to the Portuguese
in exchange for horses, wheat and textiles.
This trading system led the Portuguese crown in 1455 to build a fortress
at Arguin. As Jaime Cortesäo has shown, the foundation of Arguin marked a
turning-point in the organization of Portuguese trade. Conquest and its corol-
lary, the kidnapping and forcible taking of slaves, were replaced by peaceful
trade accompanied by a show of force in the shape of the building of a fortress
—which could in case of need serve as a refuge. The establishment of Arguin
was also to set the pattern for buildings subsequently erected all along the coast
of Africa, not only by the Portuguese but also by their European rivals. Arguin
likewise served as a port of call for ships sent to reconnoitre the south ; and
the trade soon began to thrive. Cá da Mosto in 1455 reckoned the number of
slaves brought to Portugal annually at 700-800. A special administration, the
Casa dos Escravos, was set up in Lisbon, and the customs house in the capital
recorded the entry of 3,589 slaves from 1486 to 1493, not including arrivals
from Lagos. C. R. Boxer puts the number of slaves captured by the Portuguese
in Africa between 1450 and 1500 at 150,000.
Then, as territories suitable for colonization were discovered, sugar-cane
cultivation was introduced into them, entailing a need for manpower which had
to be brought from the coast of Africa. This was why, after the discovery of
the Cape Verde archipelago, the king of Portugal in 1466 granted the first
settlers a monopoly of the slave trade on the African coast opposite the archi-
pelago, both to provide labour for the plantations and also to help populate
these uninhabited territories. They were, however, forbidden to sell the slaves
outside.
As the trade increased, the crown wished to control it—without, however,
being able to take it in hand directly. It therefore sought to derive profit from
the trade while keeping its own risk to a minimum; accordingly it set up a
farming-out system, the contratos. In 1469 Afonso V granted Fernäo Gomes
the first contract, giving him the exclusive right to the Guinea trade for five
years (subsequently extended for a further three) in return for an annual
lump-sum payment to the crown and an obligation to discover a hundred leagues