THE NILE IN HARNESS fitted to carrying the enormous volume of its waters down to Khartum. Another scheme contemplates the erection of a dam at Lake Tsana, on the highlands of Abyssinia, which will make that lake a reservoir for the Blue Nile and enable it to water the fertile plain which lies between the Blue and White Niles, ending at Khartum.

The great trouble now is that a large part of the waters of the Nile go to waste, particularly in the swamps of the Sudd region. These mighty swamps lie on the northern slope of the Congo watershed and are fed by the branches of the White Nile known as the Bahr el Jebel, the Bahr el Ghazal, and the Bahr el Zaraf. They begin where the River Sobat flows into the Nile and form an irregular triangle, the base running from that point two hundred miles westward, with the southern apex at Bor, which is two or three hundred miles farther south. They lie on the bed of what in prehistoric times was a great lake, and are composed of masses of reeds, papyrus, and other swamp grasses, so interlaced that they soak up the water like a huge sponge. Imagine a sponge as big as the State of Indiana, from two to six feet in thickness, and so situated that it is always filled by the waters of the Nile and you will have some idea of this region. This sponge is near the Equator where the tropical sun beats down upon it, so that steam is always rising. It sucks up the waters of the Nile and gives them out into the air. The evaporation in the Sudd and along the courses of the Nile is so great that an amount equal to half the capacity of the Aswan reservoir is lost every day. In the summer fully fifty per cent, of the water supplied by the Great Lakes never gets into the main stream of the Nile. The water of this swamp is nowhere much above a man's head, and in most 137