The Victoria Nyanza is in origin little but the widened course of the river Kagera, which flowed along a curved depression to the eastward of the Ruwenzori, Ankole, Mpororo, and Mfumbiro highlands. The Kagera, in fact, at the present day may be regarded as the extreme source of the Nile. It rises approximately under the fourth degree of south latitude, only a few miles from the mountainous shores of northeast Tanganyika. Many streams descending[123] from these Burundi mountains unite to form the Kagera, which, after a zigzag northerly course studded with not a few small lakes, turns, under the first degree of south latitude, abruptly to the east (with one dip to the south) and enters the Victoria Nyanza a little to the north of the first degree of south latitude. The original course of the stream evidently lay between the Sese Islands (the remains of high mountains) and the coasts of Buddu and Uganda, and then through the Rosebery Channel into the Napoleon Gulf, from which, over the Ripon Falls, it issues as the acknowledged Nile. Apart from the Kagera the great Victoria Nyanza receives few rivers of size or important volume. The only others worthy to be mentioned are the Nzoia on the northeast, the Nyando and its affluents, which form Kavirondo Bay, and four largish rivers which enter the east coast of the lake. If the bed of the Victoria Nyanza could be raised by some earth movement about two hundred and fifty feet, it would be traversed by a converging network of river channels uniting with the Kagera and the main stream of the Nile in what is at present called Napoleon Gulf; and the geographical appearance of this dried-up lake would be very similar to the present aspect on the map of the many branches and affluents of the Nile and its tributaries which converge (south of Fashoda) at the junction of the Sobat. The surface area of the Victoria Nyanza may at one time have been considerably greater than it is at the present day, and have covered a good deal of the country of Unyamwezi. Perhaps at one time it had no outlet. The highlands forming the eastern spine of the continent and stretching along the eastern cliffs of the rift valley from Abyssinia to North Nyasa prevented its overflowing towards the Indian Ocean; while the Nyasa-Tanganyika Plateau and the mountains bordering the Tanganyika rift valley opposed any western escapement. Therefore the great inland sea created by the drainage of Unyamwezi, of the Kagera, and the rivers from the Nandi plateau was forced up against the ridge of highish land (4,000 feet), forming the existing countries of Uganda, Busoga, and Kavirondo. Attacking this ridge at its narrowest diameter, the pent-up waters of the Victoria Nyanza slowly carved their way northwards down the gorge now occupied by the Nile at the Ripon Falls. Nearly all the drainage of the Uganda-Busoga Plateau runs northward, and does not fall into the Victoria Nyanza. The tilt of this plateau is highest