When the Khedive Ismail invited Gordon to enter his service as governor of the new province not far from the sources of the Nile, Gordon accepted the post in the hope that he would be able to suppress slave-trading, or at least to check the hunting of black men and women. He left Cairo and travelled by the Red Sea to Suakin, rode to Berber on the Nile, and was received with much pomp and ceremony by the Governor-General at Khartum. Here he heard that the Nile was navigable for 900 miles southwards, and therefore he could continue his journey without delay. The Nile afforded an excellent passage for Gordon's small steamboat. But the Nile can also place an insurmountable obstacle in the traveller's way. After the rainy season the White Nile overflows its banks, forming an inextricable labyrinth of side branches, lakes, and marshes. The country lies under water for miles around. The waterway between impenetrable beds of reeds and papyrus is often as narrow as a lane. The roots of large plants are loosened from the mud at the bottom, and are compacted with stems and mud into large sheets which are driven northwards by the rushing water. They are caught fast in small openings and sudden bends, and other islets of vegetation are piled up against them. Thus the river course is blocked, and above these natural dams the water forms lakes. Such banks of drifting or arrested and decaying vegetation are called _sudd_, and the more it rains the greater are the quantities that come down. At length the _sudd_ becomes soft and yields to the pressure of the water, and then the Nile is navigable again. Gordon's small steamer glides gently up the river. He advances deeper and deeper into a world unknown to him, and around him seethes tropical Africa. On the banks papyrus stems wave their plumes above the reeds. It was from the pith of papyrus stems that the old Egyptians made a kind of paper on which they wrote their chronicles. Here and there swarthy natives are seen between the reed beds, and sometimes noisy troops of wandering monkeys gaze at the boat. The hippopotami look like floating islands, but show themselves only at night, wallowing in the shallow water. A little beyond the luxuriant vegetation of the banks extends the boundless grassland with its abundant animal life and thin scattered clumps of trees. After a journey of four days the steamer glided past an island. There dwelt in a grotto a dervish or mendicant monk named Mohamed Ahmed, who ten years later was to be Gordon's murderer.