a small independent population of mixed breed, with very slight European
infusion but styling themselves Portuguese and using a "bastard language"
known locally as Creole. Many of these last were busy in the slave trade.
The Royal African headquarters, with a garrison of thirty men, were on an
island in the river some thirty miles from its mouth, while its trading
stations dotted the shores for many leagues upstream, for no native king
was content without a factory near his "palace." The slaves bought were
partly of local origin but were mostly brought from long distances inland.
These came generally in strings or coffles of thirty or forty, tied with
leather thongs about their necks and laden with burdens of ivory and corn
on their heads. Mungo Park when exploring the hinterland of this coast
in 1795-1797, traveling incidentally with a slave coffle on part of
his journey, estimated that in the Niger Valley generally the slaves
outnumbered the free by three to one.[9] But as Moore observed, the
domestic slaves were rarely sold in the trade, mainly for fear it would
cause their fellows to run away. When captured by their master's enemies
however, they were likely to be sent to the coast, for they were seldom
ransomed.

[Footnote 8: Francis Moore, _Travels in Africa_ (London, 1738).]

[Footnote 9: Mungo Park, _Travels in the Interior Districts of Africa_ (4th
ed., London, 1800), pp. 287, 428.]

The diverse goods bartered for slaves were rated by units of value which
varied in the several trade centers. On the Gold Coast it was a certain
length of cowrie shells on a string; at Loango it was a "piece" which had
the value of a common gun or of twenty pounds of iron; at Kakongo it was
twelve- or fifteen-yard lengths of cotton cloth called "goods";[10] while
on the Gambia it was a bar of iron, apparently about forty pounds in