Having conquered the Soudan easily, the rulers of Egypt experienced no difficulty in retaining it for sixty years; and if other forces, partly created by the moral pressure of England and civilized opinion generally, had not come into action, there is every reason to suppose that their authority would never have been assailed. Nor did the Egyptians stand still. By the year 1853 they had conquered Darfur on the one side, and pushed their outposts on the other 120 miles south of Khartoum. In the rear of the Egyptian garrison came the European trader, who took into his service bands of Arab mercenaries, so that he pushed his way beyond the Egyptian stations into the region of the Bahr Gazelle, where the writ of the Cairo ruler did not run. These traders came to deal in ivory, but they soon found that, profitable as it was, there was a greater profit in, and a far greater supply of, "black ivory." Thus an iniquitous trade in human beings sprang up, and the real originators of it were not black men and Mahommedans, but white men, and in many instances Englishmen. From slave buying they took to slave hunting, and in this way there is no exaggeration in declaring that villages and districts were depopulated. Such scandalous proceedings could not be carried on in the dark, and at last the Europeans involved felt compelled, by the weight of adverse opinion, or more probably from a sense of their own peril, to withdraw from the business. This touch of conscience or alarm did not improve the situation. They sold their stations to their Arab agents, who in turn purchased immunity from the Egyptian officers. The slave trade, by the pursuit and capture of any tribe rash enough to come within the spring of the Arab raiders, flourished as much as ever. The only change was that after 1860 Europeans were clear of the stigma that attached to any direct participation in it.