We may compare cannibalism to the stone age, and the times of slavery to the iron and bronze epochs--slavery is as natural a step in human development as from bronze to iron.
Whilst speaking of the stone age I may add that in Africa I have never been fortunate enough to find one flint arrowhead or any other flint implement, though I had my eyes about me as diligently as any of my neighbours.

No roads are made; no lands levelled; no drains digged; no quarries worked, nor any of the changes made on the earth's surface that might reveal fragments of the primitive manufacture of stone.

Yet but little could be inferred from the negative evidence, were it not accompanied by the fact that flint does not exist in any part south of the equator.

Quartz might have been used, but no remains exist, except the half-worn millstones, and stones about the size of oranges, used for chipping and making rough the nether millstone.

Glazed pipes and earthenware used in smelting iron, show that iron was smelted in the remotest ages in Africa.