It seems probable that 25,000 Negroes a year arrived in America between 1698 and 1707. After the Asiento of 1713 this number rose to 30,000 annually, and before the Revolutionary War it had reached at least 40,000 and perhaps 100,000 slaves a year. The total number of slaves imported is not known. Dunbar estimates that nearly 900,000 came to America in the sixteenth century, 2,750,000 in the seventeenth, 7,000,000 in the eighteenth, and over 4,000,000 in the nineteenth, perhaps 15,000,000 in all. Certainly it seems that at least 10,000,000 Negroes were expatriated. Probably every slave imported represented on the average five corpses in Africa or on the high seas. The American slave trade, therefore, meant the elimination of at least 60,000,000 Negroes from their fatherland. The Mohammedan slave trade meant the expatriation or forcible migration in Africa of nearly as many more. It would be conservative, then, to say that the slave trade cost Negro Africa 100,000,000 souls. And yet people ask to-day the cause of the stagnation of culture in that land since 1600! Such a large number of slaves could be supplied only by organized slave raiding in every corner of Africa. The African continent gradually became revolutionized. Whole regions were depopulated, whole tribes disappeared; villages were built in caves and on hills or in forest fastnesses; the character of peoples like those of Benin developed their worst excesses of cruelty instead of the already flourishing arts of peace. The dark, irresistible grasp of fetish took firmer hold on men's minds. Further advances toward civilization became impossible. Not only was there the immense demand for slaves which had its outlet on the west coast, but the slave caravans were streaming up through the desert to the Mediterranean coast and down the valley of the Nile to the centers of Mohammedanism. It was a rape of a continent to an extent never paralleled in ancient or modern times. In the American trade there was not only the horrors of the slave raid, which lined the winding paths of the African jungles with bleached bones, but there was also the horrors of what was called the "middle passage," that is, the voyage across the Atlantic. As Sir William Dolben said, "The Negroes were chained to each other hand and foot, and stowed so close that they were not allowed above a foot and a half for each in breadth. Thus crammed together like herrings in a barrel, they contracted putrid and fatal disorders; so that they who came to inspect them in a morning had occasionally to pick dead slaves out of their rows, and to unchain their carcases from the bodies of their wretched fellow-sufferers to whom they had been fastened[75]."