After the confluence of the Atbara the Nile receives no other tributary of running water during the whole remainder of its course, though in former times of far greater rainfall it was joined by streams of considerable volume flowing northeast from Kordofan. The Nile at Ambukol seems to fall into another rift valley or series of faults, along which, and over deserts of sandstone, granite, and limestone, it pursues its way to the southeastern angle of the Mediterranean Sea. The great river divides in the extreme lower part of its course into two main branches, through which, and a number of other smaller streams and artificial canals, it pours into the sea the attenuated volume of water derived from the rainfall of Eastern Equatorial Africa, much having been already spent in useless swamps, or evaporated as it passed over a thousand miles of desert, or diverted by man to fertilise Lower Egypt. An interesting feature of the Nile basin, and one which was known more or less vaguely to the ancient Egyptians and to the Sabæan Arabs of two thousand years ago,[128] is the existence of snow-mountains at the head-waters of the two principal rivers of the Nile system,--the White and the Blue Niles. Ruwenzori[129] was probably known to the ancients as the Mountains of the Moon. It is a mass of mainly Archæan rock some eighty miles long, which runs from northeast to southwest between Lake Albert and Lake Albert Edward. This marvellous range of snow-peaks and glaciers--a glittering panorama nearly thirty miles in length--exhibits a greater display of snow and ice (and that exactly under the equator) than can be seen anywhere else in the African continent, and is of far more imposing appearance than the isolated snow-capped summits of Kenya and Kilimanjaro (extinct volcanoes). The entire drainage of the Ruwenzori snows falls into the Albertine Nile, that is to say, into Lake Edward, or the river Semliki, which connects that lake with Albert Nyanza. The other heights crowned with perpetual snow in the basin of the Nile are the high peaks of the Samien or Simen range in northern Abyssinia, and one at least,[130] of the south Ethiopian (Kaffa) highlands. Two of the Samien peaks rise to a little over fifteen thousand feet in altitude and one (Buahit) to sixteen thousand feet. They are part of a nearly circular rim of great heights which surround Lake Tsana. To the south of Lake Tsana the mountains rise to heights of eleven, twelve, and fourteen thousand feet, but have no permanent snow. On the limits of the Nile basin, near the northeast corner of the Victoria Nyanza, stands Mount Elgon, a mighty extinct volcano,--perhaps the largest extinct volcano in the world. The crater rim of Elgon rises in places to over fourteen thousand feet in altitude, but no snow remains there permanently. Elsewhere than the Nile basin it is probable that permanent snow and ice are only to be found on the adjacent