In 1900-1901 four more blocks were removed. An experiment was made to break up one of the blocks by means of explosives, but it was found that the sudd, though very solid, was too elastic, and the only effect was to make large holes in it and no more. The old method had to be once more resorted to. By the end of 1901 only 23 miles of the channel remained uncleared, but this proved to be the most difficult of all. One block was actually 7 miles in length. Portions of the sudd had rotted, and, sinking to the bottom, completely filled up the channel, so that there was no stream at all, and it was impossible to tow pieces away and float them downstream by the usual process. To get up the river it is still necessary to go round by a series of lagoons, in which navigation is difficult, and operations have been suspended for the present. The sudd in the Bahr el Ghazal was much easier to remove, and great progress has been made, so that now the whole of that river is free, and boats can even ascend the Jur River to Wau. It is very difficult to ascertain the precise effect of the removal of the sudd on the water-level in Egypt. But it is certain that as each block was removed a quantity of water drained off the marshes and helped to diminish the fall of the river in summers of very small supply. Most of this water, spread out over a large surface, must otherwise have been evaporated and lost altogether. There can be no doubt that the improvement of the channel has been a permanent gain to Egypt of a very substantial kind, to say nothing of the advantage to the Soudan from the opening up of such an important line of communication. Those who laboured at the task deserve the highest praise. The river was so low that all communication with Khartoum was cut off for several months, and transport of supplies was always difficult. Besides this, the climate is always unhealthy, and the mosquitoes at night are almost beyond endurance. Under present conditions it will require constant care and watchfulness, especially in years of high flood, to prevent the sudd from frequently obstructing the river. But if the danger is to be permanently removed, the main channel must be so much improved by widening and deepening it that it will carry a greater volume. This will at the same time prevent the water from being dissipated in the marshes, and diminish the chances of any obstruction. The necessity for some work of this kind, if there is to be a reservoir at Lake Albert or Lake Victoria, has already been referred to. The clearing of the sudd is only the essential preliminary to the greater scheme.