Confining our view now to the physical aspect of Africa, we perceive that the four great rivers are the Nile, the Zambesi, the Quango, or Congo, and the Niger. The Orange river of the south is of less magnitude, as is the Senegal of the west. Of these, the Nile is the greatest and most interesting, the most interesting river, perhaps, of the world. The Niger drains much of western and central Africa, and with its affluents forms a system of drainage for an immense empire. The Quango is the principal river of central South Africa, but between it and the Niger are the Gaboon and the Fernand Vas with their many affluents. The Zambesi is seen to drain a region many times larger than Great Britain. The Orange with its affluents is at least equal to the Ohio in the United States. All these rivers, with the exception of the Nile, force their way through mountains which reach in almost unbroken range around the continent from Abyssinia southwestward to Cape Colony, then northwestward to Senegambia, whence they shoot off in broken fragments over the Desert of Sahara. [Illustration: VIEW ON THE LUALALA.] [Illustration: VIEW ON THE ZAMBESI.] The northern half of Africa is chiefly Mohammedan, the southern half chiefly pagan. In the north we have sheikhs, khedives, sultans, harems, intrigues, treachery, vindictiveness, and tortures. In the south we have man-eating, superstitions, fetiches, degradation, but, unquestionably as I think, very much less of man’s inhumanity to man. North and south, except where the English have control, domestic slavery exists in its most cruel forms, but nowhere in the world has it ever existed, perhaps, in such monstrous shape of iniquity as in central Africa under the rule of Islamism. Dr. Barth accompanied the sheikh of Bornoo on a predatory (slave-catching) expedition into the Musgu country on one occasion. He thus relates the principal business of a single day: “The village we had just reached was named Kakala, and is one of the most considerable places in the Musgu country. A large number of slaves had been caught this day, and in the course of the evening, after some skirmishing, in which three Bornoo horsemen were killed, a great many more were brought in; altogether they were said to have taken one thousand, and there were certainly not less than five hundred. To our utmost horror, not less than one hundred and seventy full-grown men were mercilessly slaughtered in cold blood, the greater part of them being allowed to bleed to death, a leg having been severed from the body.” The number of “slaves” (that is, free persons captured) on this expedition was about 4,000, of whom nearly 1,000, being full-grown men, were disposed of in the horrible manner above described.