462: Cattier, _op. cit._ pp. 134-135.]

A natural outcome of such a line of policy was the gradual elimination
of non-Belgian officials. In July 1886 Sir Francis de Winton, Stanley's
successor in the administration of the Congo area, gave place to a
Belgian "Governor-General," M. Janssen; and similar changes were made in
all grades of the service.

Meanwhile other events were occurring which enabled the officials of the
Congo State greatly to modify the provisions laid down at the Berlin
Conference. These events were as follows. For many years the Arab
slave-traders had been extending their raids in easterly and
south-easterly directions, until they began to desolate the parts of the
Congo State nearest to the great lakes and the Bahr-el-Ghazal.

Their activity may be ascribed to the following causes. The slave-trade
has for generations been pursued in Africa. The negro tribes themselves
have long practised it; and the Arabs, in their gradual conquest of
many districts of Central Africa, found it to be by far the most
profitable of all pursuits. The market was almost boundless; for since
the Congress of Vienna (1815) and the Congress of Verona (1822) the
Christian Powers had forbidden their subjects any longer to pursue that
nefarious calling. It is true that kidnapping of negroes went on
secretly, despite all the efforts of British cruisers to capture the
slavers. It is said that the last seizure of a Portuguese schooner
illicitly trading in human flesh was made off the Congo coast as late as
the year 1868[463]. But the cessation of the trans-Atlantic slave-trade
only served to stimulate the Arab man-hunters of Eastern Africa to
greater efforts; and the rise of Mahdism quickened the demand for slaves
in an unprecedented manner. Thus, the hateful trade went on apace,
threatening to devastate the Continent which explorers, missionaries,
and traders were opening up.

[Footnote 463: A.J. Wauters, _L'Etat independent du Congo_, p. 52.]

The civilising and the devastating processes were certain soon to clash;
and, as Stanley had foreseen, the conflict broke out on the Upper Congo.
There the slave-raiders, subsidised or led by Arabs of Zanzibar, were
specially active. Working from Ujiji and other bases, they attacked some
of the expeditions sent by the Congo Free State. Chief among the raiders
was a half-caste Arab negro nick-named Tipu Tib ("The gatherer of
wealth"), who by his energy and cunning had become practically t