On these northern and eastern flanks of Guinea where the Mohammedans operated and where the most vigorous of the African peoples dwelt, the natives lent ready assistance in catching and buying slaves in the interior and driving them in coffles to within reach of the Moorish and Arab traders.

Their activities, reaching at length the very center of the continent, constituted without doubt the most cruel of all branches of the slave-trade.

The routes across the burning Sahara sands in particular came to be strewn with negro skeletons.[5] [Footnote 5: Jerome Dowd, "The African Slave Trade," in the _Journal of Negro History_, II (1917), 1-20.] This overland trade was as costly as it was tedious.

Dealers in Timbuctoo and other centers of supply must be paid their price; camels must be procured, many of which died on the journey; guards must be hired to prevent escapes in the early marches and to repel predatory Bedouins in the later ones; food supplies must be bought; and allowance must be made for heavy mortality among the slaves on their terrible trudge over the burning sands and the chilling mountains.

But wherever Mohammedanism prevailed, which gave particular sanction to slavery as well as to polygamy, the virtues of the negroes as laborers and as eunuch harem guards were so highly esteemed that the trade was maintained on a heavy scale almost if not quite to the present day.