Early in the geological history of the globe there appear to have been rock-foldings, wrinkles in the earth’s surface in the eastern half of Africa. Sometimes this puckering of the solid crust manifested itself simply in longitudinal strips of raised plateaux of which Abyssinia and the highlands east of the Victoria Nyanza, north and west of Nyasaland, are remains. A sharper wrinkle than others produced the remarkable snowy range of Ruwenzori, perhaps the greatest altitude of the African continent. These lofty plateaux and mountain ranges from Abyssinia on the north to Nyasaland on the south have no doubt in all times attracted an unusually heavy rainfall from the moisture-laden clouds which are blown inland off the Indian Ocean. The rainfall on the Livingstone Mountains and the Nyasa-Tanganyika Plateau drains south and east to the Indian Ocean and west to the basin of the Congo; or into Tanganyika, which is likewise connected with the Congo at the present day.119 North of the Tanganyika system, however,—that is to say, approximately north of the third degree of south latitude,—the rainfall flows either towards the Mediterranean down the valley of the Nile, or else in a north-northeasterly direction into a string of isolated lakes which apparently at one time communicated with the Gulf of Aden at the mouth of the Red Sea. Supervening on the original wrinkling of the true backbone of Africa (i.e. the elevated ridge which extends from the Nubian Alps to the Cape of Good Hope or at any rate to the Zambezi) came a series of profound volcanic disturbances, elevating, depressing, cracking, and rending the eastern side of this ancient continent. As a rule this volcanic action seems to have proceeded along nearly parallel curved lines, running from the latitudes of the Zambezi River in a north-northeasterly direction. The first and widest of these faults due to volcanic action was seemingly the sinking of the ground between Madagascar and East Africa. A nearly parallel but much narrower rift valley was also formed up the trough of Lake Nyasa, northwards120 to the celebrated rift valley which lies to the east of the Victoria Nyanza, and contains innumerable lakes, large and small, salt and fresh. This valley, with some interruptions, extends north and northeast till it reaches the shores of the Gulf of Aden.121 Westward again of this East African rift (which some geologists believe to have been continued with a northwesterly inflection up the Red Sea to the valley of the Jordan) is another less clearly-defined fault, which may have produced the valleys of the Kafue and of the Luapula, and was then continued northwards through Tanganyika to the Albert Nyanza and the valley of the Nile. Various upheavals and modifications broke up the continuity of this western rift valley. The drainage of the Kafue was deflected to the Indian Ocean; that of the Luapula and its lakes and of Tanganyika to the Congo basin. North of Lake Kivu,122 however, the drainage flowed northward into a vast fresh-water inland sea, which, for want of a better name, we may call the Lake of Fashoda. A parallel to this great circular, shallow sheet of water existed not very anciently in the northern basin of the Congo, and another is to be seen at the present day in the Victoria Nyanza. This last is the largest existing lake in Africa. So far as is known it is shallow compared to such deep troughs as Tanganyika and Nyasa, and is possibly not a very ancient sheet of water as geological age may be reckoned.

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 descending123 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 round the northern shores of the Victoria Nyanza (four to five thousand feet), and falls gradually till it reaches the somewhat low level (two thousand feet) of the Upper Nile valley. The escaping waters of the Victoria Nyanza formed another great lake (Kioga-Kwania) immediately to the north on the other side of the Uganda ridge. This lake again drained off eventually to the original (Albertine) Nile. The site of its former bed is covered at the present day with vast marshes and with the straggling, many-armed lake of Kioga-Kwania.

The Albertine Nile, which some geographers think was the original main stream of the river, rises under the name of Ruchuru on the northern slopes of that great volcanic mass called the Mfumbiro mountains. These mountains have arisen in recent times in the middle of a rift valley which, seemingly, included Lake Kivu. The same fault may also contain the basin of Tanganyika, but this lies at a much lower level than Kivu. From Kivu (which no doubt once drained towards the Nile before the volcanic dam arose on the north) there would have been a gentle slope downward and northward (only partially stemmed by the extraordinary peninsula of Ruwenzori) to the basin of the Albert Nyanza.

The Ruchuru enters Lake Albert Edward,—creates that lake, in fact,—and the Albert Edward Nyanza has a northern gulf or tributary lake known as Dweru, which receives much of the drainage of Ruwenzori, and transmits the melted snows of this Central African Caucasus to the basin of the Albert Edward. From the north end of Albert Edward the Albertine Nile issues again under the conventional name of the Semliki. The Semliki flows round the abrupt western slopes of Ruwenzori into Lake Albert Nyanza, from the northern end of which important basin (which lies at an altitude of 2,100 feet above the sea), the Mountain Nile, formed by the great twin lakes, whose existence was remotely known to the ancients, starts on its career.

The Victoria Nile enters the north end of Lake Albert, and its waters leave that lake almost uninfluenced by their volume; in fact, Lake Albert has almost become a river, the Albertine Nile, when the water coming from the Victoria Nyanza enters the river-like end of the Albert at Magungo and then abruptly turns with full stream to the north. The Mountain Nile,124 after leaving Lake Albert, maintains a broad, lake-like character until it enters the narrow rift valley north of Nimule in the Madi country. Along this winding gorge, which exhibits some of the finest scenery of Africa, the Nile flows over nearly a hundred miles of cataracts and descends in all about five hundred feet. At Lado (in about 5° north latitude), where it slackens and expands, the altitude of the White or Mountain Nile is about fifteen hundred feet above sea-level. At the beginning of this cataract region, north of Nimule, the Nile receives a lengthy affluent from the southeast. This is the river Asua, which drains the very mountainous but slightly arid country west of the Rudolf watershed, and north of Mount Elgon. The Asua attracted a great deal of attention in the early days of Nile exploration, owing to Speke having thought that it was an additional outlet of the Victoria Nyanza, flowing from (what is now called) Kavirondo Bay.

North of Lado the Nile enters an exceedingly marshy region, which is perhaps three hundred miles from north to south and two hundred miles from east to west. This area once certainly was the site of a lake at one time as large or larger than the Victoria Nyanza. This lake was mostly fed from the west by seven or eight important streams, which to-day, with their many tributaries, unite to form that broad western branch of the Nile known as the Bahr-al-Ghazal.125

The Bahr-al-Ghazal is little else than a great estuary which receives contributions from many big rivers. If, however, one of these is to be selected as the main stream on account of general consistency of direction, then the Bahr-al-Arab would be the upper waters of the Gazelle. The furthest perennial source of this river is in the country of Dar Fertit, on the verge of the northernmost limits of the Congo basin, and within a few days’ journey of the Upper Shari. Other very doubtful tributaries of the Bahr-al-Arab drain off what little water is not evaporated in the somewhat arid country of Darfur. The Bahr-al-Arab is fed by at least four important rivers, which flow northward from the Congo water-parting in the Nyam-nyam countries.

If volume of water is to be considered, then probably the main stream of the Bahr-al-Ghazal is the Jur or Dyur, which, in its upper waters, is known as the Sue or Swe. The Sue-Jur rises in about 4° north latitude, not many days’ journey to the east of Mbomu. (The Mbomu is an important tributary of the Welle-Ubangi, which again is one of the principal tributaries of the Congo.) There is nearly continuous steam navigation up the Welle-Ubangi and the Mbomu to within a few days’ journey of the Nile basin. It was up this stream (from the Congo) that Marchand and his intrepid companions travelled in 1897. From the waters of the Mbomu they carried their little steam-launch overland to the Upper Sue. They were then able to descend this river for hundreds of miles to the Bahr-al-Ghazal and the main Nile. Near Mashra-ar-Rak, at the commencement of what the Sudanese style the Bahr-al-Ghazal, the Jur is joined by another important stream called, in its lower course, the Tonj, which has many tributaries coming from the vicinity of the Welle. Nearly parallel with this river to the east are the Roa and the Rōl (or Yalo), both of which enter the Bahr-al-Ghazal not far from its confluence with the main Nile. There is also a river Yei or Ayi, the direction of which is not fully determined. This river, which flows nearly parallel with the main Nile, some sixty miles to the west of Lado, either enters the Rōl and thus the Bahr-al-Ghazal, or turns into the main Nile not far from the bifurcation of the Bahr-az-Ziraf.

The Bahr-az-Ziraf is an eastern branch of the main Nile, which leaves the parental river near Bor (about latitude 6° 40′ north) and flows very tortuously northwards, rejoining the White Nile about sixty miles east of Lake No (Bahr-al-Ghazal). The Ziraf or Giraffe River has other communicating channels with the main Nile, and also throws off sluggish contributions to the Khor Felus,—a western tributary of the Lower Sobat. The Giraffe River (so named by the Arabs for the many giraffes once sighted from its banks) receives from the south an important stream known (perhaps incorrectly) as the Oguelokur, which, through its component rivers the Tu and Kos, drains the northern slopes of the Lotuka Mountains.

The lower part of the Bahr-al-Ghazal is often lost in marshes or is widened into lake-like expanses such as Lake No, at the confluence of the White Nile. About a hundred miles to the east of this confluence with the Kir or main White Nile (also called, south of this point, the Bahr-al-Jabl or Mountain Nile), there enters a very important affluent from the east, the Sobat (Baro), which is formed by a number of streams flowing from the southwestern part of the Abyssinian Empire and the vicinity of the Lake Rudolf basin.126 After its confluence with the Sobat the White Nile flows without any important tributary for something like three hundred and fifty miles nearly due north through a country which passes from a tropical luxuriance of vegetation to the acacias and thin grass of the steppe region. The influence of the Sahara Desert, in fact, begins to make itself felt,—that desert which extends right across from the Atlantic to the Persian Gulf, interrupted only by the exceptional mountain regions of Tibesti, Darfur, Abyssinia, Yaman, and Jabl Akhdar.

At Khartum, in about 15° 40′ north latitude, the Nile receives its most important affluent, the Abai or Blue Nile (Bahr-al-Azrak). This river rises on Sagada Mountain in the Abyssinian province of Gojam, passes through the south end of Lake Tsana (a piece of water about the area of Gloucestershire) in the western part of Central Abyssinia, and, after curving to the east and south, turns west and north, and brings to the Nile (it is said) that great increase of volume in the summer time which causes the annual flooding of Lower Egypt.

Lengthy as is the course of the White Nile from the Victoria and Albert Nyanzas to Khartum, and infinitely greater though the mass of its waters should be than the volume of the Blue Nile, the stream of the White River has nevertheless been much attenuated before it reaches Khartum by the waste of its volume in the region of vast swamps lying between Fashoda on the north and Lado on the south, to say nothing also of a similar waste and evaporation of water from the deflection of the Victoria Nile into the backwaters and swamps of Kioga and Kwania. Another contribution—though a much feebler one in volume of water—comes from Abyssinia in the shape of the Atbara, which, in its upper waters, is known as the Takaze.127 This river, during the dry season, almost ceases to flow in its lower portion, though it is flooded during the summer months from the melting of the snows and the heavy tropical rains on the northern Abyssinian mountains. The Atbara is considered by Sir Samuel Baker to contribute the principal share of the black mud which fertilises Egypt.

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. Ruwenzori129 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 extinct volcanoes of Kenya and Kilimanjaro, and on the highest peaks of the Atlas range far away in the west of Morocco.131

The lower valley of the Nile, the country which we know as Egypt, has undergone fluctuations of level since the beginning of the Tertiary Epoch. In the secondary ages the last five hundred miles of the Nile valley lay for a period of immense duration under the waters of the ocean, where the limestone deposits were formed. In Eocene times this limestone bed was slowly raised to the altitude of a tableland above the Mediterranean, but always cut off from the direction of the Red Sea by the continuous range of mountains which we know as the Nubian Alps. It is possible that the drainage of the Central African rift valleys and lakes and snow-mountains may, by the uprising of this tableland, have been severed from its natural escape to the Mediterranean, and that the Nile ran to waste in what is now the Libyan Desert. No doubt the Nile formed lake after lake, and the overflow from these lakes slowly bored a passage through the limestone tableland. Then in Miocene times took place a further rise in the range of the Nubian Alps and the adjoining land, which caused fractures to occur in the limestone formation. Of this the Nile took advantage, though it filled up the rifts to some extent with its debris. The Nile cut at one time a very deep bed through the limestone; but then occurred fluctuations in level, a sinking of the Nile valley which once more brought the waters of the Mediterranean far inland, and covered the channel of the Nile with rubble washed in by the sea. Previous to this the cracks and folds which had occurred through the upheaval of the eastern highlands had evidently caused volcanic disturbances by the water of the Nile reaching through these cracks the heated strata below. The volcanic outbursts left behind beds of basalt through which the persistent Nile again cut a channel. In the later Tertiary ages Egypt was a country of abundant rainfall, the very reverse of the absolute desert of to-day. Heavy rains carved and scarped the surface of the country and nourished a luxuriant forest. At this period the lands lying to the west of Egypt, in what is now known as the Libyan Desert, were probably a bay of the Mediterranean.

After the Pliocene Epoch, when man first began to appear on the scene, there was another lowering of the level of the Nile valley in Egypt, and the Mediterranean extended its waters perhaps to the vicinity of Assiut. At this time the Mediterranean was almost certainly connected with the Red Sea across the Isthmus of Suez. The Nile stream was probably rapid in its descent towards the extended Mediterranean, and cut a deeper and deeper channel. Then another rise of the land took place, separating the Mediterranean from the Red Sea, and sending back the Mediterranean to something like its present limits; the upheaval indeed may have made what is now the Delta of the Nile higher than it is at the present day, while the river cut its way through a channel many feet deeper than the existing bed. Gradually, however, the Lower Nile became more sluggish as the land near the Mediterranean rose, and, losing its rapidity, it deposited more and more thickly the detritus brought down from Equatorial Africa, Abyssinia, and Nubia, and so raised its bed to a higher level. It has also enlarged its delta by the deposit of mud, though the fatuity of its work in this direction (in the presence of earth waves) is shown by the fluctuations which have occurred even within the last three thousand years. Not more than a thousand years ago Lake Menzaleh was a fertile and richly cultivated district.

Some time after man penetrated into Egypt (probably from the east) the countries to the west of the Lower Nile began to rise above the sea, for much of the Libyan Desert was under the Mediterranean in the Tertiary Epoch. This retreat of the sea coupled with other conditions not clearly known to us brought about a marked change in the climate of Africa north of the fifteenth degree of north latitude. The aridity of the Sahara Desert and of Arabia began to exercise a potent influence over the fate of northern Africa. Many of the lands, which as late as the human period were still covered with plentiful vegetation and were traversable by the apes, the elephants, and the antelopes of to-day, began to dry up into their present condition, an aridity which, from all we know, is increasing and extending. Only Egypt was kept alive by the beneficent stream which, so abundantly nurtured by the snow-mountains and equatorial rain-belt of eastern Africa, survived even its passage of a thousand miles through the blazing desert, and covered the narrow ribbon of Upper Egypt and the tassel of the Delta with an ever fruitful soil of finely triturated mud.

The Nile has a length of course of some four thousand miles measured along the windings of the channel of its main stream,—the Kagera-Victoria-Mountain-White Nile. It is still doubtful as to whether the Missouri-Mississippi in North America is longer than the Nile, and thus the longest river in length of course in the world. In any case the Nile has the pre-eminence for actual length of basin, which, in a straight line measured from the furthest source of the Kagera to Rosetta on the Mediterranean, is about 2,490 miles.

The area of the Nile basin is approximately 1,080,000 square miles.132 This falls short of the area of the Congo basin by some 400,000 square miles. The volume of water which the Nile pours into the Mediterranean is trivial compared with the Congo’s contribution to the ocean; but then the waters of the equatorial zone in East Africa are evaporated from the surface of lakes, squandered in swamps, sucked up by the desert winds, and finally are employed to irrigate Egypt; so that no comparison with the output of the Congo would give a fair idea of the catchment in the Nile basin. This, perhaps (including the annual contribution to the Nile lakes), reaches to two-thirds of the volume of water poured into the Atlantic by the Congo’s single mouth.

This geographical sketch is intended to place before the reader the main features in the geography of Nileland. It is the summing up of the results of exploration during four or five thousand years. The preceding chapters deal with the history of the way in which the Caucasian has laid bare the secrets of the Nile to the curiosity of the civilised. It is only the Caucasian race which has cared for geography in the past,—the Caucasian in all his types as Dravidian, Hamite, Semite, Iberian, and Aryan. The Mongol of Asia and America, the Negro of Papua and Africa has never cared to ascertain whence rivers flowed and whither, what lands lay beyond the ocean or the snow-peaks. Some early cross with a Caucasian race sent the Polynesian cruising about the Pacific and venturing over the Indian Ocean from Java to Madagascar; but the more purely Mongoloid brother in China and Japan did not care to trace the chain of Aleutian Islands to Alaska and America, or if he did so by accident, felt the question of no interest, sequence, or importance. Only the Caucasian, and mainly the White Caucasian, has worried about the Nile problem. He has attacked it first from the north (Hamite, Greek and Roman); then from the northeast and east (Hamite and Semite, Greek, Portuguese, and British); once more from the north (Arabs, Turks, French, British, Germans, Italians); resolutely from the southeast (British and Germans); latterly from the southwest (British, Belgians, and French); and, finally and completely, from the north and northeast.