1911 Encyclopædia Britannica/Nile - Wikisource, the free online library 1911 Encyclopædia Britannica/Nile 1617295 1911 Encyclopædia Britannica , Volume 19 — Nile NILE, the longest river of Africa , and second in length of all the rivers of the globe, draining a vast area in north-east Africa , from the East African lake plateau to the shores of the Mediterranean . Although falling short of the length of the Mississippi - Missouri ( 4194 m. according to the estimate of General Tillo [1] ), the Nile is at the head of all rivers as regards the length of its basin, which extends through 35 m. in a direct line, with a waterway of about 4000 m. The Nile proper, i.e. from the outlet at Victoria Nyanza to the sea , is 3473 m. long. The Name.—The early Egyptians called this river by a name which was probably pronounced Hap.

It seems to be connected with a root meaning “concealed,” “mysterious.” This survived as a religious designation down to the fall of paganism . The “great river” was also a frequent name for the main stream, and this became the usual name of the Nile in late times as Ier-‘o and continued in use amongst the Copts . In the Bible the Nile is regularly named Yeōr ( יאר , יאױ ), from the contemporary Egyptian Yor, “river.” The origin of the Greek and Roman name Νεῖλος, Nilus, is quite unknown. Αἴγυπτος in the Odyssey is the name of the Nile (masc.) as well as of the country (fem.) The Arabs preserved the classical name of the Nile in the proper name En-Nīl النيل‎, or Nil-Misr مصر‎ لنيل‎, the Nile of Misr (Egypt) . The same word signifies indigo .

[2] The modern Egyptians commonly call the river El-Bahr, “the sea,” a term also applied to the largest rivers, and the inundation “the Nile,” En-Nīl; and the modern Arabs call the river Bahr-en-Nīl, “the river Nile.” Basin of the River.—The Nile system is a simple one with three principal divisions: ( 1 ) the main stream running south to north, and fed by the great lakes of East Central Africa ; ( 2 ) the equatorial tributary rivers draining the country north-east of the Congo basin ; ( 3 ) the Abyssinian affluents . The extent of the basin of the Nile is clearly indicated on the map. Its area is estimated at 1,107,227 sq. m., which compares with the 1,425,000 sq. m. area of the Congo basin . The smaller basin of the longer river is due to its narrowness when passing through the Sahara .

Southward the basin includes the northern part of the plateau between the two “Rift” valleys which traverse that part of Africa , and also that portion of the Albertine (or western) “Rift” valley which lies north of the Mfumbiro mountains. That part of the plateau within the Nile basin is occupied by the Victoria Nyanza and its affluents . These affluents drain a comparatively small part of this plateau , which stretches south to Lake Nyasa . The most remote feeder of the Nile in this direction does not extend farther than 3 m. south of the equator ) and 29 ° 15 ′ E. , following the crest of the hills which dominate the north-eastern shores of Lake Tanganyika and the eastern shores of Lake Kivu . Turning north-westward from this point the Nile basin crosses the mountainous region of Mfumbiro and includes that of Ruwenzori . Its limit is marked by the western wall of the Albertine Rift valley, in which lie the Albert Edward and Albert Nyanzas .

For a considerable distance the water-parting between the Congo and the Nile is close to the Albert Nyanza and to the Nile as it flows from that lake, but not far north of Wadelai ( 2 ° 46 ′ N. ) the hills recede and the Nile basin expands westward, over the wide area drained by the Bahr-el-Ghazal and its tributaries. In this region there is no well marked watershed between the Congo and Nile systems, which interlace. Farther north the limit of the valley is marked by the hills of Darfur . Below that point the valley of the Nile extends but a mile or two into the desert . The south-eastern limits of the Nile basin extend nearly to the western escarpment of the eastern Rift valley—the dividing plateau being a narrow one. North of the equator a bend is made westward to Mt. Elgon , which on the north-east sends its water towards Lake Rudolf . From Mt. Elgon the Nile watershed is some distance to the west of that lake, while to its north a turn is made again, the watershed including a great part of the Abyssinian highlands . Beyond 15 ° N.

it follows a line generally parallel to the west shore of the Red Sea , except where diverted to the west by the basin of the Khor Baraka . Source of the Nile.—The question of the sources of the Nile opens up a time-honoured controversy (see under Story of Discovery below). Victoria Nyanza (q.v.) is the great reservoir whence issues the Nile on its long journey to the Mediterranean . But if the source of the river be considered to be the most remote headstream (measured by the windings of the stream), the distinction belongs to one of the upper branches of the Kagera . Among the feeders of Victoria Nyanza the Kagera is by far the most important, both for length of course and volume of water carried, draining the region of greatest rainfall round Lake Victoria . Three chief branches unite to form the Kagera , and of these the most important for the volume of water carried is said to be the Nyavarongo. The Nyavarongo is formed by the union of various mountain streams, the Rukarara and the Mhogo being the chief. The Rukarara rises in about 2 m.

Its volume is stated to vary between 21,000 and 54,000 cub. ft. per second. All the other feeders of Victoria Nyanza are small and often intermittent rivers, the largest being probably the Nzoia , which enters on the north-east from the plateaus south of Mount Elgon . (The rivers which enter Albert Edward and Albert Nyanzas and, with those lakes, form the western sources of the Nile, are dealt with under Albert Nyanza and Albert Edward Nyanza .) The Victoria or Somerset Nile.—The ridge of high land which forms the northern shore of Victoria Nyanza is broken at its narrowest part, where the pent-up waters of the lake—through which a drift from the Kagera inlet to the Nile outlet is just perceptible—have forced a passage at the northern end of a beautiful bay named Napoleon Gulf. At this spot, 30 m. north of the equator, at an altitude of 3704 ft., the Nile issues from the lake between cliffs 200 and more ft. high with a breadth of some 500 yds. The scene is one of much grandeur.

The escaping water precipitates itself over a rocky ledge with a clear fall of 16 ½ ft. The falls , some 300 yds. across, and divided into three channels by two small wooded islands, are named the Ripon Falls, after Earl de Grey and Ripon (afterwards st marquess of Ripon ), president of the Royal Geographical Society in 1859 . The Victoria or Somerset Nile, as this section is called, has at first the character of a mountain stream, racing swiftly through a rocky channel often walled in by cliffs (at times 180 ft. high) and broken by picturesque islands and countless rapids. It receives the waters of several streams, which, rising within a few miles of the Victoria Nyanza , flow north. For 133 m. its course is N.N.W., when, on being joined by the river Kafu (on which Fort Mruli stands), about 1 ′ E. , it takes the north-east direction of that channel, and it is not till 2 ° N. that the river again turns westward towards the Albert Nyanza .

Seventy miles below the Ripon Falls the Nile enters a marshy lake of irregular outline, running mainly east and west, and known as Kioga (or Choga) . The current of the Nile is clearly discernible along the western shore of this lake, which is 3514 ft. above the sea. Eastwards the lake breaks into several long arms, which receive the waters of other lakes lying on the plain west of Mount Elgon . One of these, named Lake Salisbury, lies in 1 ′ N. and 34 ° E. ; east of this lake and connected with it is Lake Gedge. Lake Kioga also receives the Mpologoma, a river which rises in the foothills of Elgon and flows east and north, attaining a width of 1 ½ m.; and from the south (west of the Nile) a broad lacustrine river, the Seziwa. The Kioga lake system , lying north of the ridge which separates it from Victoria Nyanza , owes its formation in part to the waters pouring down from the Nyanza , and is in the nature of a huge Nile backwater. The lake itself is rarely more than 20 ft.

deep; its greatest length is 85 m.; its greatest width 10 m. Below Mruli , the fall in the bed levels of the Nile, which up to this point has been comparatively gradual, increases considerably. At Karuma , where the western bend to the Albert Nyanza is made, the river falls over a wall-like ledge of rock, 5 ft. high, which extends across its bed. But the great feature of the Victoria Nile are the Murchison Falls (named by Sir Samuel Baker , their discoverer, after Sir Roderick Murchison , the geologist ), situated in 2 ft. into a spray-covered abyss. Downstream from these falls the river flows for some 14 m. between steep forest -covered hills, a wide and noble stream with a current so slow and steady that, at certain seasons, it is only from the scarcely perceptible drifting of the green water-plants called Pistia Stratiotes that it can be observed. About 24 m. below the Murchison Falls and 254 m. from the Victoria Nyanza the river enters, through a wide delta, and across a formidable bar, the N.E. end of Albert Nyanza .

In its passages from the one lake to the other the Nile falls altogether about 1400 ft. Taking its name from a fort which once existed there, the delta district is known as Magungo. From Albert Nyanza to the Plains.—Issuing from the north-west corner of Albert Nyanza some 5 m. from the spot where it entered that lake, the Nile, which is now known as the Bahr-el-Jebel, or Mountain river, flows in a generally northerly direction. As far as Dufile , 130 m. below Magungo , it has a gentle slope, a deep channel and a current generally slight. It forms a series of lake-like reaches often studded with reedy islands. Immediately below Dufile the Kuku mountains on the west and the Arju range on the east close in upon the river, which, from an average width of 700 yds., narrows to 230 yds. Here the hills cause the stream to make a sharp bend from the north-east to the north-west.

Four or five miles lower down the river widens to 400 yds., and a large island divides the stream, the eastern channel carrying the main volume of water. This island marks the beginning of the Fola Rapids. At its southern end the water falls some 20 ft., and then, like a gigantic mill-race, rushes through a gorge 330 ft. long and nowhere more than 52 ft. wide, to leap into a deep cavity not more than 40 ft. across. Escaping from this “cauldron” the waters thunder on in a succession of rapids, which extend beyond the northern end of the island. In all the Fola Rapids are nearly 2 m. long. For the next 80 m. the Nile, save for the great volume of water, resembles a mountain torrent, its course interrupted by continual rapids. The last of these occurs at Bedden , where the river breaks through a line of low hills running athwart its channel. One of these hills forms an island in midstream. Below Bedden various stations are established upon the river. Fort Berkeley, in 4 ° 40 ′ N.

(on the right bank), is the nearest to the rapids. Then follow Rejaf (left bank), Gondokoro (right bank) and Lado (left bank), all within 30 m. of one another. A striking feature of the scenery at Rejaf is a cone-shaped hill, about 370 ft. high, crowned by rocks which have the appearance of the ruins of an ancient castle . At Gondokoro the Nile is clear of the hill country, and enters a vast swamp-like expanse through which it flows with a very low slope and a very tortuous channel. Between Albert Nyanza and the swamp region the Bahr-el-Jebel is joined by many streams. The most important of these affluents is the Asua (nearly 200 m. long), which enters the main stream from the east in 3 ′ N. ( 19 m. N. of Dufile ), but has little water in the dry season. The Asua and its subsidiary streams rise on the western versant of the Karamojo plateau and among the mountain ranges which run off from that plateau to the north-west, the most remote head-stream running originally due south.

The Region of Swamps.—The wide valley which the Nile enters at Gondokoro slopes so gradually towards the north that the river falls only some 182 ft. in a stretch of 475 m. Through this valley the river winds in an extremely tortuous course. Its channel has no banks, and the overflow has caused extensive swamps which are covered by a mass of papyrus and tall reeds, and are traversed by numerous shallow lagoons or “mayyas.” The shape of these lagoons is constantly altering, as also is that of the channels connecting them with the river. About 8 m. below Bor, many of the eastern “spills” unite and form a stream of considerable breadth, with a strong current. This stream, which is known to the Dinkas as the Atem, follows a course generally parallel to the Jebel , being bounded eastward by forest land. Opposite Kanisa ( 6 ° 46 ′ N. ), on the main river, the Atem divides into two channels, marshy land extending at this point a great distance to the east.

The western branch, or Awai, rejoins the Jebel near Shambé 7 ° 6 ′ N. The eastern branch or Myding continues through the marshes , eventually joining the Bahr-el-Zeraf ( see below ) in its lower course. Except for the Atem divergence the Nile, despite the swamps through which it passes, maintains a fairly definite course, with a considerable depth of water as far as Shambé, where, to the west, is a large lagoon . Five miles lower down the river splits into two great channels. That to the left, the main stream, continues to be known as Bahr-el-Jebel , but is sometimes called by its Dinka name Kir. The right branch, or Bahr-el-Zeraf ( Giraffe river), has a more easterly direction, and does not rejoin the main river until 50 m. below its confluence with the Bahr-el-Ghazal (q.v.). From the point of bifurcation the Bahr-el-Jebel flows for 230 m. in a general northwesterly direction until it is joined by the Bahr-el-Ghazal coming from the south-west.

The whole region is a vast expanse of low land crossed by secondary channels, and flooded for many miles in the rainy season. At the junction of the Bahr-el-Ghazal and the Bahr-el-Jebel in 9 ° 29 ′ N. the permanently submerged area is usually named Lake No, but the Arabs call it Moghren-el-Bohur (meeting of the rivers). Lake No in the rains covers about 50 sq. m. In the Bahr-el-Jebel occur the great accumulations of “ sudd ” (q.v.), masses of floating vegetation which obstruct and, if not removed, prevent navigation. The aspect of the river throughout the sudd region is monotonous and depressing. On all sides stretch reaches of the reed known as um suf or mother of wool (Vassia procera) , ambach, Bus and papyrus . These grasses rise 15 to 20 ft. above the water, so as often to close the view like a thick hedge.

The level of the flat expanse is broken only at intervals by mounds of earth, erected by the white ants and covered with a clump of brushwood or trees; the moisture in the air is excessive; mosquitoes and other swamp flies swarm in myriads. And yet touches of beauty are not wanting. Water lilies (Nymphaea stellata and Nymphaea Lotus)—white, blue and crimson—often adorn the surface of the stream. Occasionally the rare and odd-looking whale-headed stork or Balaenireps rex is met with among the reeds, and at night the scene is lit up by innumerable fire-fiies . The White Nile.—From the confidence with the Bahr-el-Ghazal at Lake No , the main stream, which here takes the name of Bahr-el-Abiad, or White river, adopts the easterly course of the tributary stream. Forty miles below the point where the Bahr-el-Zeraf reunites with the main branch, the Nile receives its first great eastern affluent—the Sobat (q.v.), whose head-streams rise in the mountains of south-west Abyssinia and the region north of Lake Rudolf .

Just above the Sobat junction the Nile resumes its northern course. It passes through a great alluvial plain , stretching from the spurs of the Abyssinian highlands in the east, to the hilly districts of Kordofan in the west, and covered with high grass and scattered bush . The swamps still bound it on either bank, but the river again flows in a well-marked channel with defined banks. About 56 m. below the Sobat mouth, in 9 ′ N. ) for a distance of nearly 4 m. the river is extremely broad and shallow, being fordable at low water. Fifteen miles lower down, at Goz Abu Goma —which is the northern limit of the sudd vegetation—the river is divided into two channels by Abba Island, wooded, narrow and 28 m. long. On Abba Island lived, for some years before 1881 The Blue Nile.—Five hundred and twenty miles below the Sobat mouth and 1652 m. from Ripon Falls , in 15 ° 37 ′ N. , the White Nile is joined by its greatest eastern confluent the Bahr-el-Azrak or Blue Nile.

In the fork of the two rivers stands Khartum , [3] the capital of the Anglo-Egyptian Sudan , whilst on the western bank of the White Nile is Omdurman , the former Mahdist capital. The Blue Nile, or Abai as it is called in Abyssinia , rises in the Gojam highlands in 11 ° E. , and flowing northwards 70 m. enters Lake Tsana (q.v.) near its south-west corner, to issue again at the south-east end. The Abai and its tributaries drain a great part of the Abyssinian plateau . The complicated river system is best understood by a study of the map. The Abai itself on leaving Lake Tsana makes a great semicircular sweep S.E. to N.W., from the highlands of Ethiopia to the plains of Sennar . In this section of its course its swirling waters rush over a long series of cataracts and rapids, descending from a height of 5770 ft. at the outlet to about 1400 ° 10 ′ E.

), where it crosses the Abyssinian frontier, and flows through the plains of Sennar to its confluence with the White Nile at Khartum , 1300 ft. above sea-level. Of the tributaries of the Abai the majority join it on its left bank. The Bashilo , Jamma and Muger , which reach the Abai in the order named, drain the country east of the main stream between the basins of the Takazze and the Hawash . The Guder , with a south to north course, rises in the mountains which form the watershed between the Nile and the Lake Rudolf basin. Next comes the Didessa , a large stream rising near the head-waters of the Baro (the main upper branch of the Sobat ) and flowing N.W. to the Abai, the confluence being in about 10° N., 35° 40' E. It has an early rise and a long flood period, being by far the most important tributary of the Blue Nile. The Dabus or Yabus rises about 9 ° 30 ′ E.

, and flowing north joins the Abai near the spot where that river breaks through the Abyssinian hills . All these affluents are perennial, as is the Bolassa or Tesien , a right-hand tributary which reaches the Abai below the Yabus . Four miles below Famaka the river is joined on its left bank by the auriferous Tumat , an intermittent stream. In Sennar it receives on its right bank two considerable tributaries from the Abyssinian heights , the Dinder , a very long but not perennial stream, and the Rahad , waterless in the dry season, copious and richly charged with sediment during the rains from June to September. At this period the discharge of the Blue Nile rises from less than 200 to over 10,000 cub. metres per second, thus greatly exceeding that of the White Nile itself, which is only about 800 cub. metres during the floods above the confluence. The length of the Blue Nile is about 850 m. The country, El Gezira , enclosed in the triangle formed by the junction of the White and Blue Niles forms the most fertile portion of the Sudan .

It only requires irrigation to render it one of the finest grain -producing areas in the world. The Atbara .—Two hundred miles below Khartum —at Ed-Damer —the Nile is joined by the last of its tributary streams—the Atbara or Bahr-el-Aswad (Black river) . The Atbara , some 800 m. long, rises in the tableland north of Lake Tsana , being formed by the junction of the Angreb , Salaam , Aradeb , Goang and other mountain streams. Making its way towards the Nubian plains , the river flows in a north-westerly direction, joining, in 14 ′ N. , 36 ° E. , the Bahr Setit or Takazze (see Abyssinia ), a river coming from the east and having a volume of water as large as, if not larger than, the Atbara . The united stream preserves, however, the name of Atbara , and at its confluence with the Nile has a breadth in flood time of over 600 yds.

The Atbara and its tributaries, like many of those which feed the Blue Nile , rapidly dwindle after the rains into the smallest limits. In its lower course the Atbara runs completely dry, but higher up water may be found in deep pools, hollowed out of the sand bed of the stream by the river when in flood . These pools are full of fish, turtles , crocodiles and hippopotami , which remain imprisoned until the return of the flood . The country comprised between the Nile proper , the Atbara and the Blue Nile is identified with the island of Meroë of ancient history. The Cataracts.—Downstream of the Atbara junction the Nile continues its course to the Mediterranean , traversing a distance of over 1600 m. without receiving a single tributary on either bank. Below Khartum the river makes a great S-shaped bend, and leaving behind the cultivable land pierces the Nubian desert . In its progress the volume of water suffers continual diminution from evaporation , owing to the extreme dryness of the air. The valley of the river is here very narrow, and the desert land in places comes right to the water's edge.

Elsewhere high and barren cliffs shut in the valley. Between Khartum and Wadi Halfa (the northern end of the great bend), a distance of over 900 m., occurs a series of cataracts, known as the 2 nd cataract and Assuan are 214 m. of smooth water with a scarcely perceptible slope, 1/12500 . The average breadth of the river here is 1640 ft. It runs through a sandstone bed, and the current is guided in many places by spurs of masonry built by the ancient Egyptians . Lower River and Delta.—For some distance above Assuan the river is studded with islands, including those of Philae and Elephantine . The rapids south of the town used to form the 1st cataract, where in a length of 3 m., the river fell 16 ½ ft. Since the completion of the great dam and locks at the head of these rapids (Dec. 1902 ) they have to a certain extent disappeared, and a navigable channel has been formed.

The dam, pierced by 180 sluices, stretches across the river—a wall 2000 yds. long and 26 ft. wide at the top. Below the water rushes between rocks in many channels (this being the relics of the cataract). Upstream from the dam a lake some 100 m. in length has been formed. The Assuan Dam was opened on the 10 th of December 1902 (see under Irrigation ). A ladder of four locks on the western side of the dam permits navigation between the upper and lower reaches. At Assuan the banks of the river are bordered by high granite hills. From this point to the apex of the delta the length of the Nile is 605 m. with a slope ( 1/13000 ) slighter than that above Assuan. The valley is comparatively narrow, being an almost level depression in a limestone plateau —the area of fertility ends where the land ceases to be irrigated by the river. At Edfu , 68 m.

below Assuan , a barrage, known as the Esna barrage, regulates the flow of the water, and at Assiut , 274 m. below Edfu , is another barrage fulfilling the same purpose. Cairo , the capital of Egypt , is built on the eastern bank of the Nile 12 m. north of the apex of the delta. At the beginning of the delta the Nile separates into two channels, the Rosetta and the Damietta , which join the Mediterranean at its south-east angle. At the bifurcation is a double barrage, by means of which the water can be dammed to the height required for forcing the river into the canals which irrigate the delta. Of the two branches the Damietta is the more easterly. Both are about the same length— 146 m. [5] Behind the coast-line, which is low and sandy , are a number of salt marshes or lagoons . Whilst the Damietta branch is gradually silting up, the Rosetta branch is scouring out a wider channel. In time of full flood the depth of the water in either branch is about 23 ft.

Hydrography.—The fertility and prosperity of Egypt and the northern part of the Sudan being entirely dependent on the irrigation of the land by the waters of the Nile, the variation in the supply at different seasons of the year is of vital importance. (In Egypt the height of the flood has been recorded annually, as the chief event of the year, since at least 3600 b.c.) Above the Sobat confluence the Nile traverses a region of heavy rainfall and the water -supply is superabundant. It is from Victoria , Albert and Albert Edward Nyanzas and their feeders, and in a lesser degree from the Bahr-el-Ghazal , that this river obtains its constant supply of water throughout the year. The great lakes and the region of swamps , retaining a large proportion of the water they receive, act as natural reservoirs and prevent the lower Nile from ever running dry in summer. The Abyssinian affluents are the chief cause of the Nile flood . In the equatorial regions rainfall varies from 30 in. during the year with a mean of about 50 . It is heaviest in the months of January, February, March and April, and again in October and November.

The most rainy portions of the lake plateau (where alone occurs a rainfall of 60 in. and over) lie along the eastern edge of the Albertine Rift valley, and west and north of Victoria Nyanza . These rains feed Albert Edward and Albert Nyanzas , and, through the Kagera , supply a great part of the water of Victoria Nyanza . The water in the Victoria Nyanza begins to rise in January, the rise becomes marked in June, is at its height in July, the level of the water reaching its lowest at the end of November. The Bahr-el-Jebel is at its lowest in March and April and at its highest in September. The seasonal supply of the Bahr-el-Ghazal does not vary very greatly, the maximum levels occurring in November and December. The Ghazal has but a slight discharge. The Sobat , from December to March, is at its lowest, and is in flood from June to October, during which period the water (milky coloured) which it pours into the Nile equals in volume that of the main stream. It is the colour of the Sobat water which gives its name to the White Nile .

The Blue Nile , at its confluence at Khartum , begins to rise in June and is in flood from July to October; the Atbara is also in flood during the same months. The great difference in the supply of water from the equatorial regions and from Abyssinia arises from the fact that the first-named district is one of heavy rain practically all the year round; whereas in Abyssinia the season of heavy rain is usually limited to the months of June to September. Reduced to its simplest expression, the Nile system may be said to consist of a great steady flowing river fed by the rains of the tropics, controlled by the existence of a vast head reservoir and several areas of repose, and annually flooded by the accession of a great body of water with which its eastern tributaries are flushed. At Khartum the Nile is lowest in April and May and highest in August and September. Its minimum depth is 18 ft. and its maximum depth 25 ft. At Assuan the Nile is at its lowest at the end of May, then rises slowly until the middle of July, and rapidly throughout August, reaching its maximum at the beginning of September; it then falls slowly through October and November.

At Cairo the lowest level is reached about the middle of June, after which the rise is slow in July and fairly rapid in August, reaching the maximum at the beginning of October. By using the water stored by the Assuan dam in the months following high Nile, the river lower down has been, since 1902 , replenished at times of low water to meet the needs of cultivators (see Irrigation : Egypt ). At Assuan the average rise of the Nile is 26 ft., at Cairo it is 23 ft. only at Assuan is a “bad Nile”; on the other hand, a rise of 30 ft. causes a danger of flood , or rather it used to do so previous to the building of the dam. When the Nile below the swamps is at its lowest, the water acquires a green colour and a putrid taste and smell. This is caused by innumerable microscopic green algae , which are brought into the White Nile from the marshes of the Bahr-el-Jebel and Bahr-el-Ghazal , and descend the river when it is clear of all suspended matter.

This “green water” is seen at Cairo about the end of June or beginning of July, and passes away with the first rise in the later month, the algae being unable to live in turbid water. By August the river in lower Egypt is full of dark red-brown sediment brought down by the Blue Nile and the Atbara from the plateaus of Abyssinia . It is estimated to be then carrying 8 cub. yds. per second; by September this has been reduced to half the amount, and then diminishes rapidly. It has been calculated [6] that the time taken by the water to travel from Khartum to the delta barrage varies from 14 days in September to 43 in May. On the island of Elephantine at Assuan is the famous Nilometer, dating from ancient Egyptian times , altered and extended in Roman times and repaired in 1870 by the Khedive Ismail . It is a well built of hewn stones, marked with scales to record the level of the water, which rises and falls with that of the river.

The remains of other ancient Nilometers exist at Philae , Edfu and Esna , together with inscriptions recording about forty high Niles in the XXVth Dynasty, discovered on a quay wall of the temple of Karnak . The data furnished by these give about 4 ½ in. per century as the rate at which the Nile is silting up its bed north of the 1 st cataract. The level of high Nile at the Semna rapids, between the 2 ft. lower than that indicated, by the marks sculptured c. 2500 b.c. This fall is attributed to the erosive action of the water as it passes over the hard gneiss which at Semna forms a barrier across the stream. The vertical extent of such erosion is equal to about two millimetres a year. It is noteworthy that from the mouth of the Sobat to the Mediterranean the current of the Nile is generally deepest and strongest on its right (eastern) bank; the Nile in this respect resembling other great rivers of the northern hemisphere. The pressure of the water on the right bank is attributed to the prevailing N.W. winds.

[7] There are now gauges for registering the rise of the water at Cairo , Assuan , Berber and Khartum on the main river ; at Wad Medani , Sennar and Roseires on the Blue Nile ; El Duem and Taufikia on the White Nile ; Nasser on the Sobat ; Gondokoro on the Bahr-el-Jebel ; and Ugowe , Iinja and Entebbe on Victoria Nyanza . Navigation.— At high Nile there is uninterrupted water communication from the sea to Fort Berkeley in 4 ′ N. —a distance of 2900 m. Owing to the cataracts , navigation between Assuan and Khartum is impossible during low Nile, and from the 1 st of March to the 1 st of August the upper courses of the Damietta and Rosetta branches are closed to navigation; the water being utilized for summer irrigation in the delta .

As far as Mansura ( 60 m.) on the Damietta branch and Kafr-el-Zayat ( 70 m.) on the Rosetta branch, and between Khartum and Fort Berkeley ( 1090 m.) the river is navigable all the year round, though between the Sobat confluence and Bor , navigation is dependent on the channel being kept clear of sudd . Above Fort Berkeley navigation is interrupted by the rapids and cataracts which extend to Dufile , but from the last-named town to Fajao at the foot of the Murchison Falls (a distance of 150 m .) the river is navigable throughout the year. There is a further navigable stretch between Foweira (just above the Karuma rapids ) and the southern end of Lake Kioga . The Blue Nile is navigable for steamers during flood time from its confluence at Khartum to Roseires at the foot of the Abyssinian hills , a distance of 426 m. At low water small boats only can go up stream. The Atbara is never navigable, the current during flood time being too swift for boats.

Including the Sobat and the Bahr-el-Ghazal the navigable waters of the Nile and its affluents exceed 4000 m. Owing to the cataracts and the partial closing of the Damietta and Rosetta branches for irrigation purposes, the Nile below Khartum is subsidiary, as a means of communication , to the railways and highroads . [8] Above Khartum the river is the chief channel of trade and commerce . Steamers first ascended the Nile above the cataracts (to Korosko ) in 1820 that a steamboat was placed on the White Nile . ( W. E. G. ; F. R. C. ) Story of Discovery.—Few problems in geographical research exercised for so long a period so potent an influence over the imaginations of man as that of the origin of the Nile . The ancient Egyptians , as is apparent from the records on their monuments, were acquainted with the main stream as far south as the junction of the White and Blue Niles . They appear also to have known the Blue Nile up to its source and the White Nile as far south as the Bahr-el-Ghazal confluence.

Beyond that point the sudd probably barred progress. The knowledge acquired by the Egyptians passed to the Persians and Greeks . Herodotus (about 457 b.c.) ascended the Nile as far as the First Cataract . He was led to believe that the source of the river was far to the west in the region of Lake Chad . Eratosthenes , superintendent of the Alexandrian library , in a map made about 250 b.c., showed, with fair accuracy, tho course of the river as far as where Khartum now stands. He showed also the Atbara and Blue Nile . Eratosthenes was the first writer to hint at equatorial lakes as the sources of the river. Tuba II. , king of Mauretania (who died about a.d.

20 ), in his Libyca, quoted by Pliny , makes the Nile rise in western Mauretania , not far from the ocean , in a lake presenting characteristic Nile fauna, then pass underground for several days' journey to a similar lake in Mauretania Caesariensis, again continue underground for twenty days' journey to the source called Nigris on the borders of Africa and Ethiopia , and thence flow through Ethiopia as the Astapus. This remarkable story received considerable credence, and may be connected with the theory which made the Niger a branch of the Nile, (see below). Strabo (a contemporary of Juba ), who ascended the river as far as Syene , states that very early investigators had connected the inundation of the Lower Nile with summer rains on the far southern mountains, and that their theory had been confirmed by the observations of travellers under the Ptolemies . About the same time Dalion, a Greek , is believed to have ascended the White Nile .

Nero dispatched two centurions on an expedition for the express purpose of exploring the Nile, and Seneca states that they reached a marshy impassable region , which may be easily identified with the country of the White Nile above the mouth of the Sobat . To what they referred when they reported a great mass of water falling from between two rocks is not so readily determined. During this period more accurate knowledge concerning the Nile sources was obtained from the reports of Greek traders who visited the settlements on what is now called the Zanzibar coast. A merchant named Diogenes returning (about a.d. 50 ) from the east coast of Africa told a Syrian geographer , Marinus of Tyre, that journeying inland for twenty live days he reached the neighbourhood of two great lakes and a range of snow mountains whence the Nile drew its sources. Marinus published this report in his geographical works. This book is lost, but the information is incorporated in the writings of Ptolemy , who in his book and map sums up all that was known or surmised of the Nile in the middle of the 2 nd century of the Christian era .

Ptolemy writes that two streams issuing from two lakes [9] (one in 6 ° N. to make the Nile, which, in 12 ° N. , receives the Astapus, a river flowing from Lake Coloe (on the equator ). His two southern lakes, he conceived, were fed by the melting of snows on a range of mountains running east and west for upwards of 500 m.—the Mountains of the Moon , τὸ τῆς σελήνης ὄρος, Lunae Montes. It will be seen that, save for placing the sources too far to the south, Ptolemy 's statements were a near approximation to the facts. The two southern lakes may be identified with Victoria and Albert Nyanzas , and Lake Coloe with Lake Tsana. The snow-capped range of Ruwenzori occupies—at least in part—the position assigned to the Mountains of the Moon, with which chain Kilimanjaro and Kenya may also be plausibly identified. On all the subsequent history of the geography of the Nile Ptolemy 's theory had an enormous influence.

Medieval maps and descriptions, both European and Arabian , reproduce the Mountains of the Moon and the equatorial lakes with a variety of probable or impossible modifications. Even Speke (see below) congratulated himself on identifying the old Ptolemian range with the high lands to the north of Tanganyika , and connected the name with that of Unyamwezi , the “country of the moon.” In the fourteen centuries after Ptolemy virtually nothing was added to the knowledge of the geography of the Upper Nile. Arab writers of the 12 th and 13 th centuries make mention of the great lakes, and their reports served to revive the interest of Europe in the problem of the Nile. Idrisi made both the Nile and the Niger issue from a great lake, the Niger flowing west, the Nile north. Hence arose much confusion, the Senegal estuary being regarded by its discoverers ( 1445 ) as the mouth of a western branch of the Nile. Even until the early years of the 19 th century the belief persisted in a connexion between the Nile and the Niger (see further Niger ).

Portuguese explorers and missionaries , who in the 15 th and 16 th centuries visited the east coast of Africa and Abyssinia , gained some information about the equatorial lake region and the Nile, [10] the extent of the knowledge thus acquired being shown in the map of Africa of Filippo Pigafetta , Italian traveller and historian ( 1533–1603 . It was not, however, till the 17 th century that the sources of the Blue Nile were visited by Europeans . In 1615 Pedro Paez , a Portuguese priest , was shown them by the Abyssinians . Ten years later another Portuguese priest , Jeronimo Lobo , also visited the sources and left a vivid description of the rise of the river and its passage through Lake Tsana . An English version of the accounts of Paez and Lobo —written by Sir Peter Wyche —was published in 1669 by order of the Royal Society, of which Sir Peter was an original Fellow.

Between 1625 (the date of Lobo 's visit) and 1770 , some attempts were made by French and other travellers to explore the Blue Nile , but they ended in failure. In the last-named year James Bruce (q.v.) reached Abyssinia , and in November 1772 he arrived in Egypt , having visited the source of the Blue Nile and followed it, in the main, to its confluence with the White Nile . On returning to Europe Bruce was mortified to find that whilst he was still in Egypt the French geographer D'Anville had ( 1772 ) issued a new edition of his map of Africa in which by a careful study of the writings of Paez and Lobo he had anticipated Bruce 's discoveries, D'Anville 's map is singularly accurate, if we remember the scanty information at his disposal. To Bruce , nevertheless, belongs the honour of being the first white man to trace the Blue Nile to its confluence with the White Nile . He himself, considering that the Blue Nile was the main branch of the river, claimed to be the discoverer of the long-sought caput Nili.

[11] From the time of Bruce , interest in the Nile problem grew rapidly. The Englishman W. G. Browne (q.v.) when in Darfur ( 1794–1796 ) heard that the Abiad rose far south in the Mountains of the Moon, but he makes no mention of the great lakes, and in Major Rennell's map of 1802 there is no hint of equatorial lakes at the Abiad sources. During the French occupation of Egypt the river from the sea to Assuan was accurately surveyed, the results being embodied in Jacotin's Atlas de l'Egypte ( 1807 – 1814 J. L. Burckhardt , the Orientalist, went up the Nile to Korosko , travelled thence across the desert to Berber and Shendi , and crossing the Atbara made his way to the Red Sea . It was, however, due to the initiative of Mehemet Ali , Pasha of Egypt , that the While Nile was explored.

In 1820–22 a military expedition under Ismail Pasha , a son of Mehemet Ali , which was joined by the French scientist Frédéric Cailliaud (who had visited Meroë in 1819 ) ascended the river to the confluence of the White and Blue Niles , founded the city of Khartum , and ascended the Blue Nile to Fazokl . In 1827 Adolphe Linant , a Belgian in the service of the British African Association, ascended the White Nile 132 m. above Khartum , being the first white man to do so since the first century a.d. Then followed three Egyptian expeditions sent in 1839 ° 42 ′ N. —or the foot of the rapids above Gondokoro . A Turkish officer, Selim Bimbashi, commanded the expeditions, and among the members were the Frenchmen Thibaut (a convert to Islam and for nearly forty years French consular agent at Khartum ), D'Arnaud and Sabatier, and a German , Ferdinand Werne.

The last-named wrote a scientific account of the second expedition and drew a map of the Nile between Khartum and Gondokoro . An Austrian Roman Catholic mission was established in the Sudan , and in 1850 one of its members, Dr Ignatz Knoblecher, sent to Europe reports, gleaned from the natives, of the existence of great lakes to the south. About the same time two Protestant missionaries , Ludwig Krapf and John Rebmann, stationed on the Zanzibar coast, sent home reports of a vast inland sea in the direction where the Nile sources were believed to be. This sea was supposed to extend from 0 ° 30 ′ S. These reports revived interest in Ptolemy's Geography . The exploration of the Bahr-el-Ghazal by John Petherick , Miss Tinne and her companions, and others followed the opening up of the White Nile (see Bahr-el-Ghazal .). The general result of the work carried on from the north was that by 1858 the Nile system was known as far south as the rapids at Bedden . On the rd of August 1858 the English explorer J. H.

Speke (q.v.) discovered the large nyanza (lake), which he rightly conceived to be the head reservoir of the White Nile , and which in honour of the queen of England he named Victoria Nyanza . Captain (Sir Richard) Burton and Speke had gone inland from Zanzibar to investigate the reports concerning the vast lake which Rebmann and Krapf had called the Sea of Unyamwezi. These reports proved to be exaggerated accounts of three distinct lakes— Nyasa , Tanganyika and Victoria Nyanza . In 1860 Speke returned to Zanzibar accompanied by J. A. Grant (q.v.), bent on solving the problem of the Nile. In spite of great difficulties he made his way to Uganda , on the north-west of Victoria Nyanza , and (without exploring the lake) succeeded in reaching its outlet. On the 28 th of July 1862 Speke stood by the Ripon Falls —the birthplace of the Nile. In his journey he had discovered the Kagera river , now known to be the most remote head stream of the Nile, a fact of which Speke was uncertain.

though he recognized that it was the largest river entering the nyanza . Speke and Grant paddled down the Nile a short distance, but before reaching Lake Kioga they were stopped by hostile natives and compelled to go westward to Unyoro . There they heard of another great lake further west, but the king of Unyoro refused them permission to visit it. In the end they descended the Kafu river to its confluence with the Nile and then down the main stream to the Karuma Rapids . Here Speke and Grant left the river, and travelled overland east of the stream, which they did not strike again until just above the Ausa confluence . Thence they travelled down the Nile to Gondokoro , reached on the 15 1863 . This remarkable journey virtually solved the Nile problem so far as the source of the main stream was concerned, but there remained much to be done before the hydrography of the whole Nile basin was made known. At Gondokoro Speke and Grant met Mr (afterwards Sir Samuel) Baker [12] and his wife—a Hungarian lady—who had journeyed thither to afford the explorers help.

To Baker Speke communicated the news he had heard concerning the western lake, and this lake Baker determined to find. On the 26 th of March 1863 Baker and his wife left Gondokoro , and despite much opposition, especially from slave-dealers , followed, in the reverse direction, the route of Speke and Grant as far as Unyoro , whence they journeyed west. On the 14 th of March 1864 they struck the lake ( Albert Nyanza ) on its S.E. side. They paddled up the lake to the point where a large river coming from the east poured its waters into the lake. This stream, which they rightly conjectured to be Speke 's Nile, they followed up to the Murchison Falls . Thence they went overland to the Karuma Rapids , and so back to Gondokoro by their old tracks. It fell to the lot of General C. G. Gordon (when that officer administered the Egyptian Equatorial provinces ) and his assistants to fill up the gap left by Speke and Baker in the course of the main stream. In 1874 75 two English engineer officers—Lieut.

(afterwards Colonel Sir Charles M.) Watson and Lieut. H. Chippendall—followed the river between Gondokoro and Albert Nyanza ; in 1876 an Italian , Romolo Gessi Pasha , circumnavigated that lake, proving Baker 's estimate of its size to be vastly exaggerated; Gordon in the same year traced the river between Murchison Falls and Karuma Rapids , and an American , Colonel C. Chaillé-Long followed ( 1874 ) the Nile from the Ripon Falls to the Karuma Rapids , discovering in his journey Lake Kioga (which he named Ibrahim). In this manner the identity of the Victoria Nile with the river which issued from the Albert Nyanza was definitely established. In 1874 H. M. Stanley (q.v.) went to Africa with the object of completing the work left unfinished by David Livingstone , who believed, erroneously, that the ultimate sources of the Nile were far to the south (see Congo ).

Stanley , in 1875 , circumnavigated Victoria Nyanza , setting at rest the doubt thrown on Speke 's statement that it was a huge sheet of water, [13] but proving Speke mistaken in believing the nyanza to have more than one outlet. On the same journey Stanley encamped at the foot of the Ruwenzori range, not knowing that they were the &lduo;Mountains of the Moon,” whose streams are the chief feeders of Albert Nyanza . (At the time of his visit the snow-peaks and glaciers were hidden by heavy clouds .) In 1888 , however, Stanley saw the mountains in all their glory of snow and ice, discovered Albert Edward Nyanza , and traced the river (Semliki) which connects it with Albert Nyanza . The Semliki had been discovered, and its lower course followed in 1884 by Emin Pasha . Thus at length the riddle of the Nile was read, though much was still to do in the matter of scientific survey, and in the exploration of the valley of the Sobat (q.v.).

The Kagera had been partly explored by Stanley ( 1875 ), by whom it was called the Alexandra Nile, and between 1891 – 98 its various branches were traced by the German travellers Oscar Baumann, Richard Kandt and Captain H. Ramsay, and by Lionel Décle, a Frenchman . A British officer, Colonel C. Delmé-Radcliffe, made the first accurate survey ( 1900 – 1908 by Lieut. C. E. Fishbourne. A trigonometrical survey of the upper river was begun by Colonel M. G. Talbot, director of Sudan surveys, in 1900 , and other surveys were made by Captain H. G. Lyons, director-general of the Egyptian survey department. A fish-survey of the waters of the Nile was also undertaken. The Removal of Sudd.—As already stated, the sudd above the Sobat confluence seems to have stopped the Roman centurions sent by the emperor Nero to explore the Nile.

When the river above the Sobat was again reached by white men ( 1840 ) the stream was clear of sudd , and so continued until 1863 - 1864 , when both the Bahr-el-Jebel and the Bahr-el-Zeraf became blocked by floating masses of vegetation. When Baker proceeded to Gondokoro in 1870 he thus described the increase that neglect had caused in the obstruction: “The immense number of floating islands that were constantly passing down the stream of the While Nile had no exit; thus they were sucked under the original obstruction by the force of the stream, which passed through some mysterious channel, until the subterranean passage became choked with a wondrous accumulation of vegetable matter . The entire river became a marsh , through which, by the great pressure of water, the stream oozed through innumerable small channels. In fact, the White Nile had disappeared.” Baker , who had to cut through 50 m. of sudd in his passage to Gondokoro , urged to Khedive Ismail to reopen the Nile.

This work was efficiently done by Ismail Ayub Pasha, and the White Nile was clear for large vessels when Gordon reached Khartum in 1874 . The river did not long remain free, for in 1878 Emin Pasha was unable to ascend the Bahr-el-Jebel from the south on account of sudd . It was cleared in 1879–1880 by officials in the Egyptian service, but had again accumulated in 1884 . In consequence of the Mahdist movement nothing could then be done to clear the river, and the work was not taken in hand again until 1899 , when, by direction of Sir William Garstin, the Egyptian inspector-general of irrigation , an expedition under Major Malcom Peake, R.A., was sent to cut through the sudd , which then extended from the Bahr-el-Ghazal confluence almost to Gondokoro . During 1900 a channel was cut through the northern and heaviest portion of the sudd . The work was one of much difficulty, some of the blocks being 1 m. long and 20 ft. deep; the water beneath flowed with great velocity.

To remove the obstruction the surface was first burnt; then trenches were cut dividing the sudd into blocks 10 ft. square, and each of these was hauled out with wire hawsers and chains by gunboats working from below. For a distance of 172 m. N. of Shambe (i.e. about midway between the Ghazal confluence and Gondokoro ) the true bed of the river could not, in many places, be found, but Major Peake forced a passage to Gondokoro through a spill channel or series of shallow lakes lying west of the main stream. In 1901 Lieut. Drury, a British naval officer, removed many of the remaining blocks of sudd , opening to navigation a further 147 m. of the river. Beyond this point for a distance of 25 m. the Bahr-el-Jebel could not be traced, so completely was the channel choked by sudd . In 1902 , however, Major G. E.

Matthews discovered the true bed of the river, which by 1904 was completely freed from obstructions, and freedom of navigation between Khartum and Gondokoro was permanently secured. The effect of the sudd -cutting operations on the supply of water available for irrigation purposes in the lower river was slight. Nevertheless, Sir William Garstin reported that the removal of the sudd “undoubtedly checked the fall in the river levels which would otherwise have taken place.” Political Relations.—Explored in part by Egyptian government expeditions, the upper Nile as far south as Albert Nyanza became subject, between 1840 and 1882 , to Egypt . Possession of the greater part of the river above Wadi Halfa then fell to the followers of the Mahdi . In 1896–98 an Anglo-Egyptian army reconquered the country , and from Victoria Nyanza to the Mediterranean the main river came under British or Egyptian administration. The west bank of the Bahr-el-Jebel , as far north as 5 ′ N. , was in 1894 taken on lease from Great Britain by the Congo Free State during the sovereignty of Leopold II.

, the territory leased being known as the Lado enclave (q.v.). The Kagera , the main head stream, lies almost wholly in German East Africa . Authorities.—For the story of exploration see the works of Bruce , Speke , Grant , Baker and other travellers (whose books are mentioned in the biographical notices). Their achievements, and those of ancient and medieval explorers, are ably summarized in The Story of Africa, vols. ii. and iii., by Dr Robert Brown (London, 1893–1894 ), and The Nile Quest, by Sir Harry Johnston (London, 1903 ). See also J. Partsch, Des Aristotel's Buch: “Über das Steigen des Nil” (Leipzig, 1909 ). For the Kagera region consult Caput Nili, by Richard Kandt (Berlin, 1904 ). Latest additions to geographical knowledge are recorded in the Geographical Journal (London) and the Cairo Scientific Journal. For the hydrography , geology and climate see: The Physiography of the River Nile and its Basin, by Captain H. G.

Lyons, director-general, survey department, Egypt (Cairo, 1906 ), an authoritative work, and numerous other publications of the Survey and Public Works Departments; “Notes on the History of the Nile and its Valley,” by W. F. Hume, in Geog. Jnl. (Jan. 1906 ) and the Nile Reservoir Dam at Assuan and After (London, 1901 ), both by Sir William Willcocks; the Annual Reports ( 1899 and after) of the Egyptian Public Works Department, by Sir William Garstin and others, and those on Egypt and the Sudan by Lord Cromer and Sir Eldon Gorst (London; official publications). Of special value is the Blue Book Egypt No. 2 , 1904 , which is a report by Sir William Garstin on the basin of the upper Nile, dealing at length with the lake area, the Nile affluents and the main river as far south as Khartum, from the topographical as well as the hydrographical aspect. Sir W. Garstin anti Captain Lyons give full bibliographical notes.

The study of the zoology of the Nile valley was the special object of a Swedish scientific expedition in 1901 , under the direction of Prof. L. A. Jägerskiöld. The Results were published at Upsala, pt. iii. appearing in 1909 . For the botanical and other aspects of the Nile valley, see the works of Petherick, Heuglin, Schweinfurth, Junker and Emin. An orographical map of the Nile basin was published by the Survey Department, Cairo, in 1908 . It is in six sheets on a scale of 1:2,500,000

Question: The two main branches of the River Nile are known as what?
Answer: White and Blue