It appears that the conditions on the river between Lake No and Shambe are much more favourable to blocking by sudd than they used to be. In 1840 Mehemet Ali sent a scientific expedition under D’Arnaud to explore the White Nile. At that time the main stream through the sudd country was much bigger and stronger. No mention is made of the Bahr el Zeraf at all, which looks as though it was of much less importance, at any rate. They noticed, however, a number of openings in the banks between the river and the swamps, some natural, but some artificial, made by the natives for fishing purposes. It is plausibly argued by Sir W. Willcocks that these openings were later widened by the natives to enable them to escape in their canoes from the slave-dealers, and then by the slave-dealers themselves, escaping in their turn from Government patrol boats. All these spills would drain into the Bahr el Zeraf, which gradually became a navigable stream in its lower part. In 1863 Sir Samuel Baker ascended the Bahr el Gebel without any difficulty; but in that year there was a very high flood and a great deal of sudd. Returning in 1865, Baker found the river north of Lake No considerably blocked. In 1870 Baker was unable to ascend the Bahr el Gebel with his expedition to Equatoria, and went by the Bahr el Zeraf. He cut through the sudd in that stream with prodigious labour, and had finally to cut a ditch through 2,000 feet of solid clay. Even then the Bahr Zeraf level was so much below that of the Bahr el Gebel that he could not get his boats through until he had dammed the Zeraf behind them so as to lift them up. In 1873 he says he found the canals much improved by the force of the stream. All this naturally contributed to weaken the power of the main stream and render it very liable to sudding. In 1874, when the river was low, the sudd was cleared away by Ismail Pasha Ayoub, then Governor-General of the Soudan, and all through Gordon’s time in Equatoria there was free passage, but the channel had dwindled very much. The heavy flood of 1878 brought the sudd down again worse than ever, where it remained until cleared by Marno in 1880. It was in that year that Gessi, on his way back from his province, was caught and suffered such hardships in the sudd on the Bahr el Ghazal. He was only rescued by the appearance of Marno. Unfortunately, no record has been left of the methods which Marno employed in the work, but he spoke of it as quite an easy matter.