# Africa by Élisée Reclus/Volume 1/Chapter 2

Contents
CHAPTER II.
THE NILE BASIN.
The River.
ESCENDING from the south to the north, and in its lower course traversing broad open plains, the Nile gives, as it were, a general inclination to the whole of North-East Africa towards the Mediterranean basin. Notwithstanding a difference of outline, its delta corresponds to another opening at once maritime and fluvial, that of the Dardanelles and Bosphorus, through which the regions watered by the streams of East Europe also slope towards the Mediterranean. Thus like an inner within an outer circle, there is developed in the centre of the Old World a zone of riverain lands, forming, so to say, a little world apart, and comprising such famous historical cities as Memphis, Alexandria, Jerusalem, Tyre, Antioch, Ephesus, Miletus, Smyrna, Athens, and Constantinople.
In the length of its course the Nile is one of the great rivers of the world, and by many of the tribes along its banks the earth is supposed to be divided into two parts by this mysterious stream, coiled like a snake round the globe and grasping its tail in its mouth. It certainly exceeds all the other rivers of the eastern hemisphere, not excepting the Yangtze-Kiang or the three great Siberian arteries. In this respect it even surpasses the Amazon itself, and probably yields to the Missouri-Mississippi alone. Yet the chief river falling into the Victoria Nyanza, and thus forming the true upper course of the Nile, has not yet been determined with absolute certainty. It may even be larger than has been supposed, so that calculating from its farthest source south of the equator, the African river may possibly be superior in length to its North American rival. But taking it from the Nyanza alone, it is at least 3,750 miles long, and in a straight line along the meridian from lake to sea the distance is thirty-one and a half degrees of latitude, or about 2,100 miles. But to reach the farthest headstreams of the Nile basin we ​should perhaps descend over five degrees to the south of the equator and two to the east of the emissary from the great lake. The winding of its bed lengthens its whole course by over three-fourths.
In superficial area the Nile basin is inferior both to the Amazon and the Mississippi, and apparently about equal to the Congo. Except in its middle course, between the Makrara territory and Abyssinia, the lateral river valleys are of slight extent, and owing to the arid character of most of its basin, it cannot compare in volume to any of the other great rivers of the world. According to recent estimates, the Atrato, which falls into the Carribean Sea near the Isthmus of Panama, has a greater discharge, although its basin is nearly a hundred times smaller than that of the Nile.
The general tilt of the land from the central plateaux to the shores of the Mediterranean coincides with the Nile Valley. Nevertheless to its main fluvial arteries the whole of this region is exclusively indebted for its geographical unity. The lacustrine uplands of the interior, the marshy tracts where its chief affluents join the White Nile from the south-west, the isolated Abyssinian highlands, the Kordofan uplands encircled by solitudes, the Nubian deserts, the narrow winding valley of Upper Egypt, lastly the smiling plains through which the main stream ramifies as it approaches the Mediterranean, are all so many distinct geographical domains, which must have had a purely local development but for the unity imparted to them by the hydrographic system of the Nile. Thanks to the facilities for communication afforded by this great water highway, its lower reaches were peopled by Nubian colonies from remote times; the old Egyptian culture advanced up to Meroe, and even farther south; frequent wars were waged between the Ethiopians and the lowlanders for the command of the stream; and for centuries Egyptian viceroys have made incessant efforts to extend their possessions to the whole of the Upper Nile basin as far as the equatorial lakes and the "Great Divide." Along this main highway of North-East Africa the natural divisions between the riverain populations are marked by the obstructing cataracts and the confluences of the great affluents. Hence the study of the stream to which the surrounding lands owe their historic evolution claims our first attention.
The ancients asserted that the Nile had its source in the "Mountains of the Moon," and it is noteworthy that the southernmost affluents of the lacustrine system whence it escapes were met by Speke in the "Land of the Moon." But amongst these affluents is there one copious and large enough to be regarded as the main upper stream? This "head of the Nile" is still being sought, and as in the time of Lucan, no one can yet boast of having seen the farthest source of the Nile. According to the map? prepared from the itineraries of Stanley, Smith, Pearson, and the French missionaries, the Mwaru (Liwumba, Luwambé), which rises beyond the fifth degree of southern latitude, and flows north and north-west towards the ​ Nyanza, would appear to be the true "Nile of the Moon," at least in the length of its course. But if the barometric altitudes taken by Pearson can be trusted, this stream cannot possibly reach the lacustrine basin, for it flows at a lower level. On the other hand, it cannot trend westwards in the direction of Lake Tanganyka, from which it is sopanited by ridges some 500 feet high. Hence it probably runs out in some landlocked basin.
Speke was informed by the natives that this region, comprised between the great lake and the lofty coast ranges, is studded with lakes and salines, like those heard of by Denhardt, Erhard, and Wakefield as lying further north. Till recently copious streams might still be supposed to flow from the western slope of Eilima-Njaro, the giant of African mountains, whose two snowy peaks rise some 240 miles to the east of Nyanza. But the waters escaping from the gorges of this volcano flow mainly east and south to the Indian Ocean, while the rivulets descending from its west side lose themselves in the depressions of the plateau. None of the watercourses observed by Stanley and other travellers on the east side of Nyanza are of considerable size, and all of them rise at some distance from Kilima-Njaro.
The water-parting between the Indian Ocean and the Nile is lower than the eastern ranges, and has rather the appearance of an elevated cliff terminating abruptly eastwards, and sloping gently towards the west. Above it at intervals rise volcanic cones, and the statement of the Arabs, that several of them still show signs of activity, has been recently confirmed by the evidence of the traveller Fischer. Erruptions are even said to occur, and two of the cones take the name of Dunye-M'buro, or "Smoky Mountain." Another is known as the Dunye-Ngai, or "Heavenly Mountain," and copious thermal streams flow from the fissures. The foot of the eastern escarpments, some 4,320 feet high, is skirted by a thermal lake, which is continued by swampy tracts where soda is deposited. In this district the chain of volcanoes is separated by a deep depression from Kilima-Njaro, and the lake itself is little over 2,000 feet above sea-level.
​ The Kagera is evidently a very copious stream, which during the rainy season overflows its banks for several miles, in a way that reminded Grant of the Hugli between Calcutta and Chandernagor. When Speke crossed it in January, 1862, that is, at low water, it was only 250 feet wide; but here it resembled a canal cut through dense masses of reeds, and was too deep for the boatmen to employ their poles. Its current is very rapid, running at least 3½ miles an hour and at its mouth forming a large estuary over 430 feet wide, and varying in depth from 80 to 130 feet. For several miles from the shore its dark grey stream continues to flow in a separate channel without intermingling with the blue waters of the lake.
The natives have a great veneration for their river, and one of the titles they give it seems to justify the hypothesis that it is really the main headstream of the Nile. According to Stanley they call it the "mother" of the " Stony Current," that is, of the emissary of Lake Nyanza in Uganda. At its north-west angle the lake is joined by the Kalonga, another copious river rising in the west in the neighbourhood of Lake Mwutan-Nzige. Although it has a course of over 120 miles, its volume is certainly inferior to that of the Kagera.
Lake Victoria Nyanza.
The Nyanza, that is " lake " in a pre-eminent sense, known also as the Ukerewe, and now as the Victoria Nyanza, is the largest lacustrine basin in Africa. According to Stanley's provisional map, which will soon be superseded by the more matured work of Mackay, it is exceeded in superficial area only by one other lake—Superior, in North America. Both Michigan and Huron are smaller by several thousand square miles; and Aral itself, although generally designated by the name of "Sea," appears to yield in extent to Nyanza.
In the depth of its waters also this vast basin rivals the great lacustrine cavities of the world. In the immediate neighbourhood of the east coast, and close to some islands and islets, the sounding line recorded a depth of 590 feet, which may probably be exceeded in the middle of the lake. Should this prove to be the case, Nyanza will take the first place amongst fresh- water basins for the volume of its liquid contents. Its altitude above the sea has been variously estimated by different observers, but 4,000 feet has been provisionally adopted as not far from the truth.
By Speke, who discovered it in 1858, this great inland sea has been named the Victoria Nyanza, in honour of the Queen of England. But every tribe along its shores gives it a different name, while the Swaheli of Zanzibar know it as the Bahari-ya-Pila, or "Second Sea." Many other names also occur in history which evidently have reference to this sheet of water. The title of Kerewe is taken from Ukerewe, the largest island on the south coast, which is separated from the mainland by the narrow strait of Rugeshi, a mere ditch almost completely choked by ​the papyrus and other aquatic plants. But according to Wilson the most general appelation is simply Nyanza, that is, the "lake" in a superlative sense.
South of Ukerewe a large bay penetrating fur inland has by Stanley been named after Speke, his precursor in the exploration of equatorial Africa, The stagnant pools and lagoons fringing this inlet are infested by crocodiles of enormous size. Others, which frequent the reedy banks of the Tanguré, are by the natives regarded as demi-gods, personifying the tutelar deity of the stream. Some of the islands are in the undisputed possession of fierce hippopotami, grouped in regular tribes and families, which tolerate the presence of no other large animals in their respective
territories. For the capture of these monsters the natives have constructed boats of a peculiar build; but such hunting expeditions are always attended with great risk.
The coastlands, which apart from a thousand small indentations have a circumference of over 720 miles, present an endless variety of landscape. Along the rocky shores the prevailing formations are everywhere gneiss, granite, or basalts. But in some places the riverain tracts spread out in level, treeless plains, while elsewhere the margin of the lake is skirted by high hills and even mountains diversified with patches of verdure and enlivened by groups of villages. Between ​ the Kalonga and Tanguré rivers the coast is generally low, and here the shallow water nowhere exceeds a few feet in depth for two or three miles from the land. But farther south the shore is fringed by bare clifPs, varied with strips of red or orange lichens, giving them the appearance of blocks of iron, and several have in fact been found to consist of ferruginous ores.
The most charming prospects are displayed towards the north-west in the territory of U-Ganda. Here the inlets along the coast appear to be divided by the intervening wooded headlands into lakelets of unequal size. Limpid streams are everywhere seen sparkling amid the dense masses of verdure ; down every dell flows a silvery rivulet fringed with tall grasses or shrubs, above which are interlaced the branches of forest trees. Probably no other region in Central Africa enjoys a more equable climate or a richer soil than this land of U-Ganda. The plants of the temperate zone recently introduced by Europeans thrive well.
Off the coast of U-Ganda an archipelago of four hundred islands, of which the largest group bears the name of Sesse, stretches in a continuous chain between the high sea and the creeks along the shore. The scenery of this insular world is even more diversified and its vegetation more exuberant than on the opposite mainland. Here magnificent timber clothes the slopes of the hills down to the beach, which is everywhere bordered by masses of papyrus. Towards the west the basalt island of Bukerebe, Stanley's Alice Island, raises its blackish walls over 300 feet above the lake. But of all the insular masses lining the shores of Nyanza, the most remarkable is that to which Stanley has given the name of "Bridge Island." This rock, which lies not far from the north-east corner of the lake, consists of two basaltic columns connected by an irregular elliptical arch with a spring of about twenty-four and a depth of twelve feet. Trees have struck their roots deep into the interstices of the rocks, which, overgrown with brushwood and tall grass, leave nothing visible except two columnar masses of verdure hanging in graceful festoons down to the water. Through this archway of tropical vegetation a glimpse is afforded of the hazy coast-range bounding the horizon on the opposite mainland.
The beauty of the Nyanza scenery is enhanced by the native craft which en- liven its waters, and which are at times grouped in large fleets. Some of the surrounding communities have sailing-boats; the traders have launched vessels of considerable size, resembling the dhows of the Zanzibari Arabs, and the European missionaries have constructed sloops on the English model. But most of the skiffs are still of a primitive type, mere barges with round stems sunk deep in the water, and sharp prows projecting clean above the surface and adorned with two antelope horns and a bunch of feathers. From a distance they present the appearance of an animal raising its neck above the water in search of prey. These boats, manned by crews of from ten to forty-eight hands, carry neither mast nor sail, and are propelled only by the paddle. Rudely constructed of trunks of trees lashed together with flexible branches, and caulked with a mixture of bark and mud, they offer but a slight resistance to the waves; hence accidents are frequent, although they seldom venture far from the shore.
Before the arrival of the Europeans the fleets of the king of U-Ganda seldom ​
dared to approach the island of U-Vuma. The islanders, armed with nothing but a knife, would swim towards the boats, dive under the keels, and sever the connecting wooden ropes. Presently the frail craft were swamped and their crews struggling in the water. Those and other dangers of the navigation insure for the divinities of the lake the respect of all the surrounding populations. The water-gods, who dwell on the islands, condescend to communicate with mortals only through their envoys, who dare not be approached by empty-handed votaries. But the steam launches must ere long deprive these local deities of their prestige and reduce them to the level of ordinary mortals. When the American Chaillé-Long wanted to embark on the lake, the king of U-Ganda struck off the heads of seven wizards who had hitherto been both worshipped and hated as the evil genii of Nyanza. By this summary process he hoped to ensure the safety of his guest. Storms and waterspouts are frequent on the lake. "Wilson has also determined the existence of a current, which sets steadily from Speke Bay parallel with the coast westwards. It is caused by the south-east trade winds, which prevail throughout the greater part of the year.
The superfluous waters of the inland sea flow gently through a broad opening on the north coast over against the island of U-Vuma. This emissary, forming the head of the Nile properly so called, gradually narrows its banks to the proportions of a river, when its liquid contents are precipitated over a tremendous cascade, to which Speke has given the name of the Ripon Falls. A group of boulders, on which a few trees have taken root, stands nearly in the centre of the stream, which is here about 1,300 feet broad. Other less elevated blocks divide the current right and left, which lower down is studded with other reefs and rocks scarcely rising above the surface of the seething waters. Hence the expression Jinja, or "Stones," applied by the natives to these falls. Although they have a vertical height of 13 feet, hundreds of fishes crowding the lower reach are able to leap the rapids and pass to the upper stream, which a short distance higher up is gentle enough to be crossed by a ferry. Here the view of the lake is to a great extent concealed by a wooded headland, while the line of separation between the gulf and the course of the river is marked by a low peninsula crowned with a clump of palms. The hills of the mainland merge farther on in the verdant isles of the lake.
The Somerset Nile.
According to Stanley, the Kivira, as the Nile is here called, is about a third larger than the Tangur^, the chief affluent of Nyanza. It flows with a mean breadth of 550 yards, at first towards the north-west, and after passing a few smaller rapids, spreads out right and left in vast reedy lagoons. But even here its normal depth is maintained, and some 60 miles below the fulls it enters the Gita-Nzigé, another lake, to which the name of Ibrahim has been given by Chaillé-Long, who discovered it in 1875. Compared with the other equatorial basins, it is of small extent, having an area of probably not more than 200 square miles. In this region the Nile receives a number of tributaries, including the Luajerri, which ​ rises in the U-Ganda hills near the shores of Nyanza, and which was supposed by Speke to flow from the lake itself. On his map he sketched a third emissary, the Kafu, which after a course of about 120 miles joined the Nile lower down. But such a phenomenon as three rivers flowing from the same lake and meeting again after traversing a hilly region would indeed be remarkable. In point of fact the Kafu, like the Luajerri, rises not in, but near the lake, with which it has no communication.
Soon after leaving Lake Ibrahim the Nile is described by Chaillé-Long as again expanding into a vast morass covered with vegetation, and with a mean depth of scarcely more than 10 or 12 feet. This is the Kioja or Kapeki lagoon, which was discovered by the Italian explorer Piaggia, and a short distance below which the Nile is joined by the navigable river Kafu. Farther on it describes a bend towards the east and north, after which it trends abruptly westwards to its confluence with the great lake Mwútan-Nzigé, or Albert Nyanza. Throughout this section of its course the Nile is usually designated on English maps by the name of Somerset.
The river, which has here a mean breadth of over 1,300 feet, would be perfectly navigable but for its precipitous incline. According to the approximate measurements taken by travellers, the total fall in this distance of about 90 miles appears to be 2,310 feet, or about 1 in 205 feet. The Kuruma, the first fall occurring in this part of the Nile, is rather a rapid, where the water, confined between walls of syenite, escapes in sheets of foam down a total incline of about 10 feet. But this is followed by the Tada, Nakoni, Assaka, Kadia, Wade, and Ketutu Falls, forming the chief barriers to the Nile on its descent from the high plateaux. In a space of 18 miles it passes from gorge to gorge, rushing over rocky boulders, filling the atmosphere with vapours, which are precipitated as rain on the trees lining its banks. The action of the stream has, so to say, sawn through its stony walls, while gradually lowering its level. On the south bank the cliffs rise to a vertical height of from 140 to 160 feet above the boiling waters.
Lake Albert Nyanza.
The lake discovered by Buker, and by him named the Albert Nyanza, is known to the people on its east bank as the Mwutan-Nzigé, or "Grasshopper Sea." Others cull it the "Great Water," although far inferior in extent to the Victoria Nyanza. It stretches south-west and north-east for a distance of about 90 miles, with a mean breadth of over 18 miles. According to Mason's rough survey it has a superficial area of 1,850 square miles, and stands at an altitude of 2,300 feet. From the Victoria to this lower basin the Nile has consequently descended nearly half of the entire elevation of the continent between the plateaux and the Mediterranean. Like the Dead Sea, the Mwutan-Nzigé seems to fill a fissure in the earth's crust. It is enclosed right and left by steep mountains, whereas at its northern and southern extremities it terminates in gently shoaling bays and low-lying beaches. The high cliffs on the east side, consisting of granite, gneiss, and red porphyry, form a first stage in the ascent towards the U-Nyoro and U-Ganda plateaux. The streams flowing from the swamps on these uplands have not yet completed their work of erosion by furrowing regular channels across the outer scarps of the plateau. Hence, like the Nile at Murchison Falls, they have all still to make their way through cataracts, where the volume of water is less but the fall much greater, being approximately estimated for most of them at about 320 feet.
Livingstone and other explorers of Central Africa supposed that Lake Tanganyka belonged to the Nile basin, sending its overflow north-eastwards to the Albert Nyanza. But subsequent investigation has shown that the two lakes have no communication with each other. During their trips round the latter, both Gessi and Mason ascertained that from the south it receives no affluent except a shallow, sluggish stream, almost choked with vegetation. In this marshy district it is covered with a floating or half-submerged forest of ambach (arabaj), a leguminous plant (heminiera elophroxylou), 18 or 20 feet high, with star-shaped leaves and golden yellow flowers like those of the broom. Its wood, which resembles cork in appearance, is the lightest known to botanists, so light that a raft strong enough to support eight persons forms the load of a single porter. It grows so densely that the native boats are unable to penetrate the tangled masses of vegetation springing from the muddy bottom of the lake. Beyond this aquatic forest Gessi beheld a vast prairie rolling away between two steep mountains, which formed a southern continuation of the coast ranges.
Lake Albert, continually renewed by contributions from the Nile, is everywhere sweet and pure, except in the southern shallows, where the water is turbid and brackish, and in some places on the east side, where it mingles with saline springs, utilised by the people of U-Nyoro. Although no distinct undercurrents have been observed, the navigation is rendered very dangerous by the sudden squalls sweeping round the headlands and down the mountain gorges. When embarking on their frail craft the natives never fail to cast some valued object into the lake as a propitiatory offering to the water-gods. A chief, one of Baker's friends. ​ obtained from him a quantity of glass trinkets for the purpose of insuring the stranger's safety by employing them in this way. But since those first visits Lake Albert, already temporarily annexed to the Khedive's possessions, has been navigated in every direction by two steamers, which to pass the Nile cataracts had to be taken to pieces and put together again above the last portages. The transport of the Khedive required no less than 4,800 hands, of which 600 were needed to haul the boiler across the swamps, through the woods, and over the hills. The escarpments along the east coast are far more elevated than those on the opposite side.
It is sometimes asserted that the Nile traverses Lake Albert without mingling with the surrounding waters. But recent inquiry has shown that such is not the case. According to the varying temperatures, the warmer fluvial current spreads in a thin layer over the surface of the lake, gradually blending with it under the influence of the winds. But when the stream is colder it descends to the lower depths of the lacustrine cavity, where it replaces the lighter fluid. Hence, although the inflow is distant scarcely 12 miles from the outflow, the Somerset Nile becomes lost in the great lake, whose superfluous waters must be regarded as the main feeder of the emissary.
The White Nile.
This emissary, variously known as the Kir, the Meri, the Bahr-el-Jebel, or "Mountain River," and by other names according to the dialects of the riverain populations, flows normally north and north-east in a tranquil stream winding at a width of from 2,000 to 6,000 feet between its verdant banks. In the middle of the channel the depth varies from 16 to 40 feet, so that throughout the year it is accessible to large vessels for 120 miles below the lake. The shores are fringed with wooded islands and islets, while large masses of tangled vegetation drift with the current, especially at the beginning of the floods. These floating islands consist of a substratum of decomposed foliage and reeds strong enough to support an upper layer of living vegetation, by whose roots and tendrils the whole mass becomes solidly matted together. Daring the course of five or six years the flora becomes renewed, the surface growth decomposing in its turn, and causing the aquatic garden to break up and float away in smaller sections with the stream. But it often happens that the vegetable refuse accumulates in sufficiently large quantities to enable these floating islands to strike root here and there in the bed of the stream, and in the Nile basin whole rivers have sometimes been covered with such buoyant masses, firm enough to bear even the weight of caravans. Owing to the rapid development of this rank vegetation, the Nile has frequently been choked in its upper reaches and compelled to cut new channels in the surrounding alluvia. On the plains stretching west of the present Nile traces are seen in many places of these old beds, or "false rivers," as they are called. The low chain of hills skirting this plain on the west, and forming the water-parting between the Nile and Congo basins, might not inaptly be named the "Explorers' Range." The crests following ​ from south to north bear the names of Schweinfurth, Junker, Chippendall, Speke, Emin, Baker, Gordon, and Qessi.
The great bend described by the Nile below the Dufli station, at an elevation of about 2,100 feet above the sea, marks a very important point in the hydrography of its basin. Here it is joined by several copious affluents, including the Asua or Asha, supposed by some geographers to flow from Lake Mburingo (Baringo, Bahr Ingo), which Speke at one time identified with a north-east inlet of Victoria Nyanza, and whose very existence has since been questioned. But the question has been practically settled by Thomson, who visited the district in 1884, and who determined the existence of Baringo and another large lake farther south.
The Asua, however, rises not in a Like, but in a hilly region east of the Somerset Nile, while the Mbaringo is a landlocked basin without any outflow. At their junction both the Nile and the Asua, skirted right and left by hills, are obstructed by reefs, and even above the confluence the navigation of the main stream is completely obstructed by the Fola Rapids, which Wilson has named the "Eighth" Cataract. Here all vessels on the Upper Nile have to stop and tranship their cargoes, an inconvenience which has caused the Nile route to be almost abandoned above the rapids. After leaving the bend at Dufli, caravans for Victoria Nyanza strike south-eastwards, rejoining the Somerset Nile at Foweira, above the Karuma Kapids. This route, which has also been taken by the recent military expeditions from Egypt, is twice as short as that by the winding valley of the river.
Below the Asua confluence the Nile is still obstructed here and there by rocky ledges, as at Yerbora, where it rushes between huge boulders, at Makedo, where it develops two falls over six feet high, and at Tcrenio-Garbo and Jenkoli-Gafbo, where other rapids occur. But all of these impediments may be passed during the floods. Steamers freely ascend for nine months in the year as far as Ragat or Rejaf, and to the winding at Bedden below the falls forming the " Seventh " Cataract. But during low water they are unable to get beyond the famous station of Gondokoro, or Ismailiya, which was long the capital of Upper Egyptian Sudan. The head of the navigation for large vessels is indicated by the sandstone eminence of Rejaf, a perfectly regular cone of volcanic appearance terminating in a tower- shaped rock, which rises over 330 feet above the surrounding plain.
At this point the Nile, according to the estimates of Dovyak and Peney, has a normal discharge of about 20,000 cubic feet, oscillating between 10,000 at low and 30,000 at high water. During the floods it presents an imjiosing appearance at Gondokoro and Lado (Lardo), the new capital of the province of the equator. But flowing through an almost level plain, it soon ramifies into numerous lateral channels, while other secondary streams, intermingled with marshes and lagoons, wind right and left of the Bahr-el-Jebel, or Kir, as this section of the Nile is called by the Dinkas. The main stream itself branches off completely, the Nile proper continuing its north-westerly course, while the Bahr-ez-Zaraf, or "Giraffe River," winds for 180 miles through swamps and prairies northwards to a point where the two branches again unite. The Zaraf is described by Mamo not as a ​river in the proper sense, but merely a khor or watercourse, which is becoming yearly less navigable, and already inaccessible to boats except for a short time during the floods. The whole low-lying region at present intersected by the Bahr-el-Jebel, the Zaruf and all their countless affluents, channels, and branches was evidently at one time a vast lake, that has been gradually filled up by the Fig. 11. — From Dufilé to Lado alluvia of these rivers. Its northern margin is indicated by the abrupt change in the course of the Nile at the confluence of the Buhr-el-Ghazal, or "Gazelle River." At this point the whole system of waters is collected in a single channel, which is deflected eastwards along the escarpment of the upland Kordofan plains. A cavity of the old depression is still flooded by a remnant of the lake called the No, Nu, or Birket-el-Ghazal, which, however, under the action of the currents and periodical floods, is continually overflowing its marshy banks, shifting its place and modifying its outlines. Nowhere else is the Nile more obstructed by vegetable refuse as along this section of its course. The floating islands drifting with the current being arrested by the abrupt winding of the stream are collected together, and stretch at some points right across the channel, which thus becomes displaced. But the new channel is soon blocked by fresh masses of sedd, as it is called, which in many places covers a space of twelve miles. This sedd often acquires great consistency, supporting a dense growth of papyrus, and even of arborescent vegetation, beneath which the main stream continues its sluggish course. Numerous families of the Nuer tribe pitch their tents on the verdant surface, living exclusively on fish caught by piercing the foundations of their dwellings, and on the grain of various species of nymphæaceæ. In certain places along the banks of the river and surrounding swamps are seen myriads of earth-mounds, all raised above the highest level of the inundations by their architects, the termites, who ascend and descend from story to story with the flowing and ebbing stream. One of the most ​remarkable inhabitants of this watery region is the balæniceps rex, a curious long-legged aquatic bird with grey plumage, which when perched on a termite’s hillock looks from a distance like a Nuer fisherman.
From the time when the envoys of Nero failed to penetrate the sea of floating vegetation, explorers of the Nile Fig. 12. — Region of the "Sud." have been frequently arrested by this obstacle. During the latter half of the present century most of them have had to force their way through the tangled masses, and one of the channels thus formed by Miss Tinne’s steamer still bears the name of Maya Signora. During the seven years from 1870 to 1877 the river was completely blocked, obliging all travellers to continue their journey by the Bahr-ez-Zaraf. Many were detained for weeks and months on these pestiferous waters, over which hover dense clouds of mosquitoes. Here Gessi was arrested in 1880 with five hundred soldiers and a large number of liberated slaves, and three months elapsed before an Egyptian flotilla, under Marno, was able to rescue them by opening a passage from below. Devoured by the insects, wasted by fever, and reduced to live on wild herbs and the dead bodies of their unfortunate comrades, most of the captives found a grave in the surrounding swamps, and nearly all the survivors perished of exhaustion soon after. Gessi himself outlived the disaster only a few months. To the lagoon of No must be attributed those “ green waters” noticed at Cairo during the early days of June, when the stream, charged with vegetable ​cellules, acquires a marshy taste and becomes unwholesome. But all this refuse is swept away or destroyed by the first floods from the Abyssinian rivers, which thus restore to the Nile water its excellent properties.
The "Gazelle," which joins the main stream in the No basin, is a "bahr," that is, a considerable river, flowing from the west, and during the floods bringing sufficient water to sweep away the temporary obstructions. In its channel are collected a hundred other rivers, whose numbers and copiousness form a striking contrast to the poverty or total absence of running waters characteristic of the Nile basin farther north. Altogether the affluents of the great river are distributed
But then follows a sudden and remarkable contrast, due to the changed climatic conditions. All the triangular region comprised between the Bahr-el-Jebel, the Nile, and Congo water-parting, and the Dar-For uplands, is intersected by numerous perennial streams nearly converging in the direction of the old lacustrine basin now filled with alluvia and vegetable refuse. With their minor headstreams and affluents they form a vast and intricate hydrographic system, extremely difficult accurately to survey, especially owing to the varied and shifting nomenclature. Like the Nile itself, every secondary branch bears as many names as there are tribes in its valley or neighbourhood. The most important appear to be the Yei, which is lost in the swamps bordering the left bank of the Nile; the Rol, flowing to the Bahr-el-Ghazal; the Roa and Tonj, whose united waters form the Apabu; the Diur, which reaches the Bahr-el-Ghazal near Meshra-er-Rek, and which is the most copious of its many affluents; the Pango, a branch of the Diur; lastly the Famikam, better known as the Bahr-el-Arab, which forms the northern limit of the whole region, and which, after its junction with the Ghazal, deflects the Nile eastwards.
Most of these streams have a very gentle incline, the most rapid being those that take their rise in the mountains near lake Albert Nyanza. Some have their source altogether in the plains, offering an almost imperceptible transition to the basin of the Congo. In their lower course the Rol, Diur, and some others have too slight a fall to scour their beds of the vegetation constantly accumulating. The consequence is that, like the Nile, they overflow their banks, during the floods converting the whole country for some thousands of square miles into an impassable morass. A large portion of the rainfall in this part of the Nile basin evaporates before reaching the main stream. Here the annual rains represent a volume greater than the whole discharge of the Nile at Cairo.
At the point where it resumes its normal northerly course beyond the region of sedd, the Nile is joined on its east bank by the Sobat, which is also known by a great variety of names. The Sobat, which drains a very large area, and which ​Russegger mistook for the Nile itself, is the first affluent that receives any contributions from the Ethiopian highlands. It frequently sends down a greater volume than the main stream, whose waters during the floods are stemmed and driven back by its current. To judge from its whitish fluid contents, in which the blackish Nile water disappears, the Sobat has the best claim to the title of Bahrel-Abiad, or "White River." Some of its affluents rise on the low-lying plains stretching east of the Nile; but the most important has its source much farther east, in the upland valleys of the Ghesha range, which forms the water-parting between the Indian Ocean and Mediterranean basins. The Baro, which is one of the dozen different names of this affluent, on entering the plain traverses the
marshy Lake Behair of the Arabs, or "Sea of Haarlem," as it has been renamed by the Dutch explorer Schuver. During the rainy season the Sobat sends down a vast quantity of water, on June 15, 1862, estimated by Pruyssenaere, 70 miles above the confluence, at 42,000 cubic feet per second. Hence during the floods the whole of its lower course is easily navigated; but if large craft linger too long on its treacherous flood they run the risk of being landed high and dry on some shifting sandbank, as happened to the trader Andrea Debono, who was recently detained in the river for eleven months.
It is below the Sobat that the Nile takes currently the Arab name of Bahr-el-Abiad, or "White River," by which it is generally known to Europeans above ​ Khartum, where it is joined by the other Nile, called the Bahr-el-Azraq, or "Blue River." The contrast is certainly striking between the two currents, the former being charged with organic remains, turbid, and muddy, while the latter, flowing from a rocky region, is generally much more limpid. But a greater contrast is presented by the variations in their respective volumes according to the seasons. The western branch, which is by far the longest, the distance from Khartum to its still undeterminetl source being even greater than from that place to the Mediterranean, has also the most uniform discharge. Regulated by the great equatorial lakes, and again by the swampy depressions about Lake No, its contents present comparatively less discrepancies from season to season. But the impetuous Bahr-el-Azraq partakes rather of the nature of a torrent. As soon as the tropical downpours begin to fall on the Abyssinian plateaux, the effect is felt in its rocky channel. Then its discharge exceeds that of its rival, and it was on this ground that Bruce and many subsequent explorers claimed the first rank for the Abyssinian branch. But since the discoveries of Speko, Grant and Baker, it can be regarded only as an important tributary of the Bahr-el-Abiad. Its mean volume is less considerable, nor is it navigable at low water.
The Blue Nile.
On the other hand, if it is the White Nile that maintains the perennial stream, to the Blue Nile is due its fertilising properties. "Without the first there would be no Egypt; but for the second the soil of this region would lack its inexhaustible fertility. Not only do the Abyssinians send down their quickening waters to the Nile delta, but they also supply it with the sedimentary matter by which the land is incessantly renewed, and the never-failing return of bountiful harvests insured. In the Ethiopian highlands is solved the mystery of the Egyptian stream, yearly overflowing its banks without apparent cause, and then retiring to its bed after accomplishing its beneficent work. It is to be regretted that the discharge of both rivers has not been accurately determined, the Nilometer at Khartum serving to estimate that of the Blue Nile alone.
At the confluence we at once enter regions known to the ancients. The Bahr- el-Azraq is the Astapus of Ptolemy, whose source was possibly known to the Romans. At least they make it rise in a lake, the Coloe Palus, although placing this lake some twelve degrees south of its actual position. Lake Tana (Tsana) is regarded as the reservoir giving rise to the Abai, which is usually taken as the upper course of the Blue Nile. But if length of course alone be taken into consideration, this honour should rather be awarded to the Beshto, which has its origin some 150 miles farther east. The Tana emissary, however, has the advantage of being much more constant in its discharge, thanks to the controlling action of the ​ lake, which rises slowly during the floods, and falls imperceptibly during the dry season. The yearly discrepancy between the levels of the lake scarcely exceeds forty inches.
The Abai, its largest affluent, rises at Gish Abai, near the north-east foot of Mount Denguiya, some 60 miles from the lake. The Portuguese colony settled in this region towards the end of the sixteenth century certainly visited the sources of the Abai; but they were first described by the Jesuit Paez, who tells us that the water, oozing from a marshy field, is collected in a limpid lake, supposed by the natives to be "unfathomable" because they cannot reach the bottom with their spears. Thence trickles a rivulet, whose course can be traced only by a surface growth of waving grasses, but which over a mile lower down emerges in the open. This is the brook to which both the Portuguese and Bruce gave the name of the Nile. The fiery exhalations often seen flitting about its source, doubtless will-o'-the-wisps, have earned for the Abai the veneration of the natives, who still sacrifice animals to the local river genius. The stream has a width of over 30 feet where it reaches the south-west inlet of the lake, and where its turbid waters have developed an alluvial delta of considerable size. But the outlet, which retains the name of Abai, is a limpid blue current fully entitled to its Arabic designation of Bahr-el-Azraq. Like most other rivers which are at once affluents and emissaries of lacustrine basins, the Abai is constantly said to traverse lake Tsana without mingling with its water. But although such a phenomenon is well-nigh impossible, a perceptible current certainly appears to set steadily from the mouth of the affluent to that of the outflow.
Tsana cannot be compared for size to the great equatorial lakes. According to Stecker's survey, it has a superficial area of scarcely 1,200 square miles, or less than the twentieth part of Victoria Nyanza. But it must have formerly been more extensive than at present, as is evident from some alluvial plains found especially on the north side. It has the general form of a crater, except towards the south, where it develops into a gulf in the direction of its outlet. Hence the hypothesis advanced by several authors that it may have originally been a vast volcanic cone, and certainly some of the rounded islets in the neighbouring waters look like extinct craters, while the surrounding shores are diversified with bold basaltic headlands. The central part of the basin is probably very deep, for even in the southern inlet Stecker recorded a depth of 240 feet. The water is extremely pure, and as pleasant to the taste as that of the Nile. Towards the south-west the shore is fringed with dense masses of a long light reed (arundo donax), with which the natives construct their tankuas, frail skiffs or rafts propelled by two or four oars, and provided with raised benches to keep the cargo dry. But very little traffic is carried on from coast to coast. Through the foliage which encircles this lovely sheet of water, little is visible except the distant hills and the conic islets rising above the sparkling surface. Herds of hippopotami are often seen on the shores, but there are no crocodiles in the lake, although the Abai below the cataract is infested by these reptiles. Nor has any European traveller seen the aila, a small species of manatee said by the natives to inhabit its waters; which, however, abound ​ in fish, chiefly cyprides of a different species from those of the Nile. A kind of bivalve also occurs, resembling the oyster in appearance and flavour.
Issuing from the lake at an altitude of 6,200 feet, the Abai flows at first towards the south-east, forming a first fall near Woreb, 5 miles below the outlet. Expanding lower down to a width of about 650 feet, it winds along through shady fields to the Tis-Esat, or Alata Falls, where it is suddenly precipitated from a height of over HO feet into a yawning chasm shrouded in vapour. In the centre of the cascade stands a pyramidal rock surmounted by a solitary tree constantly agitated by the breeze. Immediately below this spot the Abai plunges into a winding gorge, at one point scarcely 8 or 10 feet wide, crossed by a bridge of Portuguese construction. Some 30 miles farther on it is crossed by another bridge, the central arch of which has given way, its broken fragments forming a reef amid the tumultuous waters underneath. The whole distance between these two bridges is little more than a succession of falls and rapids, with a total descent of at least 2,000 feet. Alpine masses tower to the right and left above the gorge, which seems to have no outlet. But after describing a complete semicircle round the Abyssinian plateau, the Abai emerges on the plain in a north-westerly direction. The fall in this vast circuit is altogether over 4,000 feet, while throughout its lower course, terminating at the Khartum confluence, the incline is scarcely perceptible. Here it winds in gentle meanders between its alluvial banks, which are constantly yielding to the erosive action of the stream.
During the dry season the Bahr-el-Azraq diminishes in volume downwards, and in many places may be easily forded. For more than half the year the Yabus and Tumat, its chief tributaries from the south, are apparently merely dried-up wadies, although the water still percolates beneath the sands. The Rahad, or Abu-Atraz, also one of its large eastern affluents, which rises on the west slope of the Abyssinian border range, is completely exhausted for a long way above the confluence before the wet season. But from June to the middle of September, when the rain falls in torrents on the mountain slopes, its vast bed overflows its banks, supplying abundant water to the cultivated riverain tracts. The Dender, however, another river rising in Abyssinia, appears to be perennial. Nowhere else would it be more useful or more easy to construct reservoirs and control the discharge than in this hydrographic basin, which at the confluence of the two great arteries at Khartum stands at an altitude variously estimated at from l,250 to 1,400 feet above sea-level.
The northern as well as the southern section of the Abyssinian plateau is also comprised in the Nile basin. But here the affluents of the great river rise, not on the western slope, but in the very heart of the highlands, close to the range forming the water-parting between the Mediterranean and the Red Sea. The Takkaze, main headstream of the whole Atbara hydrographic system, has its source at an elevation of nearly 7,000 feet, and flows at first westwards, as if to fall into Lake Tsana. But the gorge through which it descends between its crystalline schist walls rapidly attains a level fur lower than that of the Ethiopian uplands. At the point where the river trends northwards it has already fallen to an altitude of con​ siderably less than 4,000 feet, and here its banks begin to be fringed by a tropical vegetation. On descending from the surrounding mountains, which are swept by cold winds, the sensation is like that felt on entering a hothouse.
The Atbara.
After its escape from the region of the plateaux, the Takkazé resumes its westerly course, and at last reaches the plain through a series of rugged gorges. Here it takes the name of the Setit, and is joined by the Atbara, which is much less in volume and hardly half its length; but the mean direction of its valley, beginning immediately west of Lake Tsana, is the same as that of the united streams. The Atbara, like the Mississippi on joining the yellow and turbid waters of the powerful Missouri, gives its name to the hydrographic system; the Goang, one of the tributaries of the Takkaze, rises in the north in the depression of Lake Tsana, from which it is separated only by a ridge 165 feet high. Below the confluence the Atbara, which retains the ancient name given it by Ptolemy under the form of Astaboras, gradually diminishes in volume, as does also its former affluent, the Mareb, which in its upper course describes one of those large semi-circular curves so characteristic of the Abyssinian rivers. In fact, the Mareb, or the "River of the West," as it is called by the Abyssinians from the direction of its course, may be said to have ceased to be an affluent of the Atbara. Called the "Sona" in its middle and "Gash" in its lower course, where it is only an intermittent stream, it flows northwards parallel with the Atbara, and runs out in the alluvial lands before reaching its former outl(;t, called by the Hadendoa nomads "Gash-da," i.e. "Mouth of the Gash." On visiting the country in 1864, Munzinger found that its bed had not been once flooded for twenty years. This change in the local hydrography doubtless arises from the irrigation works constructed on the left bank of the Gash. Embanked on this side, the river flows to the right, eating away its eastern and highest cliffs. Its course, formerly at right angles, now becomes parallel to the Atbara; but as it flows northwards it finally runs dry in the sands. In 1840, Ahmed Pasha, the Egyptian conqueror, tried again to divert the Gash westwards into the Atbara, but his embankment was undermined by the riverain population of the lower plain. Till recently the river Barka, or Baraka, flowing into the swamps on the Red Sea coast not far from Suakin, was also supposed to belong to the Nile basin through a branch of the Mareb. This tradition differs little from that related by Strabo, according to which a branch of the Astaboras flowed to the Red Sea. The hypothesis may perhaps be partly due to a confusion of names, for the plain stretching east of the Mareb towards the Atbara is called Barka, or Baraka, a term also applied to the channel flowing eastwards. However this be, the Axumite Ethiopians, and after them the Abyssinians, who long identified the true Nile with their Takkaze, fancied for centuries that it would be easy to divert their river into the sea and thus deprive Egypt of the water required for its crops. This illusion, however, was also entertained by foreigners, and is referred to by Ariosto in his "Orlando Furioso." Repeating the threat of ​Albuquerque, who asked the King of Portugal to send him workmen from Madeira to assist him in making a new bed for the Nile to the Red Sea, Theodore, "king of
kings," boasted that he would divert the Mareb into the Barka, in order to create a famine in Egypt and compel the Khedive to capitulate.
During the dry season, the Atbara, unlike the Blue Nile, fails to reach the main stream. Its bed, 440 yards broad, is completely dry; "a desert within a desert," it is merely a waste of shimmering sands, to which the distant mirage gives the ​ appearance of sparkling water. But in the lower bed of the Atbara a few pools are scattered here and there. They owe their existence partly to the hollows that the eddies have excavated many yards below the normal bed, and partly to the trees that line the bank preventing the water from evaporating. In these pools, some more than half a mile in length, others reduced to an extent of a few square yards, are crowded together, in a space much too small for their mutual ease and safety, all the river fauna—fishes, turtles, crocodiles, and even the hippopotamus; the wild animals resort likewise to these pools teeming with life, and every palm and every thicket along the bank has its colony of birds. In most of the rivers on the plain the water brought back with the rainy season returns gently into its channel. Preceded by a current of air, which causes the foliage along its banks to thrill with life, it advances with a sound like the rustling of silk. The first sheet of water is a mere mass of yellowish foam mixed with debris of all sorts; following this mixture of mud and water comes a second wave, the true fluvial stream; then appears the normal current, towards which the animals rush to quench their thirst. But the powerful volume of the Atbara rushes on like an avalanche; when it again fills its bed, it is not by a slight and gradual advance, but by a sudden rush of water sweeping everything before it. The traveller sleeping on its sandy bed is suddenly awakened by the trembling of the earth, and by an approaching roar like that of thimder. "El Bahr! el Bahr!" shout the Arabs, and there is scarcely time to rush to the bank to escape the advancing flood, driving before it a mass of mud, and bearing on its first waves reeds, bamboos, and a thousand other spoils torn from its banks. Presently the river bed is completely flooded, a quarter of a mile broad, and from 18 to 40 feet deep, flowing on as calmly as if its current had never been ruffled. Like the Blue Nile, the Atbara, called also by the Arabs the Bahr-el-Oswad, or " Black River," flows into the Nile, and running with it from cataract to cataract, sends down to the lower reaches that muddy sediment by which the fertility of the soil is ever renewed.
The Nubian Nile.
Below the junction of the two Niles, north of Khartum, the river has no more visible affluents during the dry season, the lower bed of the Atbara itself being quite exhausted. But it probably receives hidden streams, for through evaporation, lateral filtrations, and the loss sustained in irrigating the riverain plains, the stream is diminished only by a seventh according to Lombardini, and by a fifth according to Gothberg, in the entire section of 1,620 miles between Khartum and Cairo. In the great bend that it describes in its course through Nubia it is diminished very slowly; but to the eyes of the traveller its volume does not appear to be modified during this long course over a considerable portion of the earth's circumference. As the Nile discharges a quantity of water equal to four times that of the Loire, or seven times that of the Seine, merchant vessels might penetrate through this highway to the centre of the continent, were it not obstructed at intervals by numerous rocky barriers. The Nubian Nile is thus divided by six natural barriers ​into seven navigable reaches; nor can vessels pass from one to the other except at high water, or without the aid of hundreds of hands to haul them over the rapids or check their downward course., Were the waters of the Nile not retained by these obstructions, and were the stream allowed to flow freely during the dry season, the question may be asked whether there would be sufficient water for the whole year; would a delta have ever been developed or an Egypt created?
Preceded, between Tamaniat and the Jebel Melekhat, by two steep rapids and
a gorge commanded by two basaltic columns, the sixth and most southern cataract between Khartum and the mouth of the Atbara would hardly be thought worthy of the name on such rivers as those of Canada and Scandinavia, where the still-undeveloped valleys have preserved their abrupt declivities notwithstanding the constant erosive action of the running waters. This cataract of Garri is rather a rapid caused by the presence of granite reefs at this point; still it suffices to interrupt the navigation for the greater part of the year. When the railway, ​destined to become the commercial outlet of the whole Upper Nile basin, shall connect the Red Sea coast with the Atbara and Nile confluence, this line will have to be extended up stream as far as the cataract of Garri to allow of uninterrupted traffic. The fifth cataract, which is followed by the rapids of Gerasheb, Mograt, and others between Berber and Abu-Hamed, obstructs the navigation only at low water; but farther down occur more serious natural impediments. Most travellers crossing Nubia between Sudan and Egypt follow the land route from Abu-Hamed to Korosko, not merely because of the vast semicircle described westwards by the Nile in this part of its course, but also because its bed is here obstructed by three
series of cataracts. One of these groups of rapids, known as the "fourth cataract," is of considerable length, and is divided into many stages like a series of sluices. First comes Dulga Island, a high rock crowned by a ruined fortress; then follow other granite boulders visible above the water, but without interrupting the navigation. This first barrier is succeeded by islands and sandbanks, followed by more rocks, dividing the river into steep channels, and the gorge ends near Gerendid, in a sort of gateway formed by two rocks covered with the ruins of fortresses. Here are no trees like those on the fifth or the third cataract situated below New Dongola, not a patch of verdure on the bank to soften the wild grandeur ​ of the scenery. Nothing meets the gaze except water, rock, sand, and sky, until it is arrested farther down by the bold headland of Mount Burkal.
The "third" cataract, like the others, comprises several partial falls, below an ancient island-studded lake, where the river expands to a width of some seven miles between its two banks. At the first granite reef, that of Hannek, so called from a Nubian castle on its left bank, the stream, divided into a thousand foaming channels, presents a more decided fall. Here blackish rocks of hornblende and feldspar project from twenty-four to twenty-six feet above low water. The river-craft do not venture amid the openings of this irregular barrier; but under the right bank runs a channel broad enough to allow two boats to pass abreast. At the entrance of the cataract a few trees festooned with creepers overhang, in dense arches, reefs which are carefully avoided on account of the venomous snakes which infest them. Lower down more islands are scattered in mid- stream, their verdure contrasting vividly with the black rocks. The Hannek rapids have a total length of 4 miles, and the difference of level between the two extreme points varies from 18 feet at low water to 10 feet during the floods. It is thus evident that the fall is here comparatively slight, as is the case in most of the other cataracts.
Below Hannek the Nile trends sharply east and north towards the Kaibar or Kajbar bank, which during the dry season seems to completely obstruct the stream. It has the appearance of an artificial dyke, which by a peculiar optical illusion, due to the contrast between the dark rock and the greyish water, seems to rise to a considerable height. The rock must be approached quite closely to find the tortuous outlets through which the foaming channels of the Nile escape. During the Hoods the Kaibar barrier is entirely concealed, leaving free passage to the stream between its banks. The "Wadi-Halfa, or "second cataract," is the point where most European and American travellers making the "tour of the Nile" bring their journey to a close. The rock of Abu-Sir, which commands its tumultuous waters and affords a magnificent uninterrupted view of the southern horizon, is scrawled all over with the names of adventurous tourists, proud of having penetrated so far up the mysterious river. Although this cataract stretches over a space of more than fifteen miles, it forms merely the lower portion of the series of rapids known as the Batn-el-Hagar, which have a total length of about eighty miles. The river presents everywhere the same aspect throughout the whole of this section. Its broad bed is strewn with boulders, most of them rounded off like stones polished by glacial action; whilst others are disposed vertically like basalt columns, or else cut up into jagged crests, bristling with sharp and needle-like spines. Between these reefs rush the winding channels, each forming a separate cascade; elsewhere occur landlocked basins, in which the whirling waters seem completely arrested. To these succeed other rapids, falls, and eddies, the cataract thus breaking up into a thousand partial falls. But at low water these minute thread-like streams are scarcely visible, being lost in the vast maze of shoals and channels. Excluding the reefs, the archipelago consists of three hundred and fifty-three islands and islets, each with its Nubian name, more than fifty of them being inhabited and ​ cultivated. Farther north the right bank is skirted by a chaos of extinct volcanoes forming a continuation to the rocks of the cataract. Cones, craters, rugged crags, mounds of indurated ashes, hillocks of lava, stand out with their thousand varied forms against the horizon of the Libyan desert.
The "first" cataract, that of Asuan, is neither so long nor so uniform as that of Wadi-Halfa, nor does it present the same desolate appearance, but it none the less deserves the name bequeathed to us by the ancients. It also consists of a series of rapids endlessly ramifying amid the granite rocks of divers forms and colours, mostly destitute of vegetation, but offering here and there grand or charming pictures with their piled up rocks amid the foaming waters, and their picturesque groups of palms, tamarinds, or thickets festooned with lianas. The approaches of the cataract are guarded above by the island of Philae, at once a temple and a garden; and below by Elephantine, the "Island of Flowers," whose beauties are mirrored in the waters of the stream. Their historical memories and associations also contribute to render the sight of these rapids one of those spectacles that challenge the attention of the observer in the highest degree, and that leave an indelible impression on the memory. Here is the "gate" of Egypt; here, since the commencement of recorded history, we trace, as it were, a visible boundary between two worlds. By a remarkable coincidence this boundary is almost indicated by the Tropic of Cancer, for it was close to Asuan that for the first time astronomers saw, at the summer solstice, the sundials deprived of their shadow and the wells pierced to the bottom by the solar rays. Another world began for them beyond this ideal line; it seemed to them as if in the torrid everything must contrast with the phenomena of the temperate zone. Even at the present day we are easily led to exaggerate all the local differences between the regions stretching on either side of the cataract and the populations inhabiting them.
At high water the navigation is not arrested along this so-called cataract. Boatmen pass with safety up and down; but at low water the passage either way on the thousand arms of "Neptune's vast staircase" is only to be accomplished by the aid of the "chellala," or "men of the cataract," who tow or check the boats by means of hawsers. About fifty large dhahahiyé, engaged by the tourists, yearly brave the dangers of the falls, and thanks to the experienced pilots employed, accidents are rare. The skill of the boatmen in descending the cataracts displays itself in keeping the boat on the central crest formed by the stream, at times rising six or even more feet above the main body of water skirting the rocks; from the top of this moving hill the pilot commands the foaming rapids. The moment the boat swerves right or left from the crest of the wave the danger begins; if the sailors are unable to redirect it into the current by oar or rudder, it is inevitably dragged into the eddies at the sides and exposed to the rocks, compared by the Arabs to monsters who "bite" it to pieces as it is borne along.
At the sight of these rapids it may be asked, while allowing for the poetical
over a lofty granite ledge. The desert east of the rapids is intersected by an old branch of the river running at several yards above the present high-water level. Even the most superficial observer of natural phenomena cannot fail to perceive that he is travelling in a now abandoned watercourse. Ho still perceives the windings of the stream between rocks covered with hieroglyphic inscriptions; he observes its old cliffs and banks, and here and there the alluvia are still revealed under the billows of sand drifting before the winds from the desert. The records deciphered by archaeologists describe the march of armies along this old river bod, from the times of Thotmes and Rameses down to the present day. According to the observations made by Lepsius at Semne above the second cataract, it is probable that, from the beginning of Egyptian history, this dried-up channel was once flooded by a branch of the Nile. During the reign of Amenemha III., some 4,700 years ago, the watermarks engraved on the rocks at this place show that the flood level exceeded by many yards that of the present time: the highest watermark exceeds by 25 feet, the lowest by 13 feet, the corresponding levels of modem days. On the right bank of the Hannek cataract also M. de Gottberg has found alluvial deposits 10 feet above the level of the highest modem floods. May not the waters have been thus arrested by the cataracts, and forced to flow into the now dried-up valley which serves as a highway between Egypt and Nubia? Above the Batn-el-Hagur rapids are to be seen many tracts formerly cultivated but now quite sterile, since the waters of the floods no longer reach them. Like all river valleys whose beds are regulated by the action of running waters, that of the Nile establishes its equilibrium by falling in Nubia and again rising in Lower Egypt. M. de Gottberg accoimts for the lowering of the water- level in Nubia through the disappearance of cataracts formerly existing between "Wadi-Halfa and Asuan, traces of which are still visible. The rocks forming these cataracts consist of schists, which, unlike the crystalline reefs, yielded to the destructive force of the stream. The granite rocks themselves also yield to the same action, but much more gradually.
The Lower Nile.
Below the granite ledge washed by the waters of the first cataract, the cliffs lining the river bank are composed of layers of sandstone, succeeded farther on by limestone rocks. Historic Egypt begins at the foot of this rocky barrier, which is covered on either side by tertiary deposits. North of Asuan the banks of the river are at first separated only by a space of from two to three miles. The fields and plants hemmed in between the escarpments and the stream present on either side nothing but a narrow strip of verdure winding along the foot of the grey or yellow rocks, which glitter like burnished gold in the sun. The cultivated zone lies chiefly to the west, along the so-called "Libyan" bank, which is most exposed to the solar rays. Like most other rivers of the northern hemisphere, the Nile bears chiefly towards its right bank, the current skirting the foot of the rocks, which at some points rise sheer above the stream. The towns stand mostly on the left bank. ​although several left high and dry by the retreating waters have frequently had to shift their sites in order to maintain their communication with the river.
At the defile of Silsile, or the "Chain," where the valley, 4,000 feet across, appears to have formerly been barred by an iron chain, the landing-stages adjoin the old quarries which supplied blocks of stone and statues for the palaces of the Pharaohs. A sphinx's head is still to be seen here not yet detached from the rock. From this point the mountains begin to diverge on both sides, the river winding in a plain about 9 miles broad, the first below the cataract that affords sufficient space for the site of a large town. Tere formerly stood Thebes of the hundred gates. Farther on the valley becomes wider, the distance from mountain to mountain varying from
12 to 15 miles; but in this part of its course, as well as above Thebes, the river bears chiefly towards its right bank, eroding the base of the cliffs of the Arabian range. On the left side the hills are mere sandy dunes shifting and modifying their form with every gust of wind. The cultivated tracts are here invaded by the Libyan desert, an extensive view of whose dreary wastes may be obtained from the crests of the western range.
Near Keneh, 36 miles below Thebes, the Nile describes that great curve which brings it nearest to the Red Sea. At this point it is distant from the coast, in a straight line, not more than 60 miles. Precisely in this direction the eastern range is broken by one of the deepest transverse ravines occurring throughout its whole course, and it may be asked whether, in some remote geological epoch, the Nile ​may not have flowed through this breach towards the Red Sea. Beaches of rolled pebbles, which could only have been deposited by running waters, are found in this gorge both on the slope of the Nile and on that of the sea. It is probably these traces of a former channel that have suggested to the vivid imagination of the
Arabs the idea that it would be easy to divert the Nile into its former bed, always supposing that this ravine did once receive the waters of the river. But if the course of the Nile cannot be deflected into this lateral gully, it would at least be easy to construct a railway through it, which would make the port of Koseïr the ​ chief commercial outlet of all Upper Egypt. Over fifty years ago the English already sank wells at intervals along this gorge, with the view of utilising it for the overland route to India.
After flowing westwards below the great bend of Keneh, the Nile trends northwest and north; but in this part of its course it bifurcates, one arm branching off and flowing parallel with it on the west side at a mean distance of seven miles. This is the Bahr-Yusef, or " River of Joseph," so called in memory of Pharaoh's minister mentioned in the Jewish traditions, or rather of a certain Joseph, minister of the Fatimites in the twelfth century. But it does not appear to have been excavated by the hand of man, although it has been frequently embanked, deflected, and directed into lateral channels, like all the running waters of the valley. Recently the point of derivation has been displaced, and the canal named Ibrahimieh has been raised to the level of the high banks in order more easily to regulate the discharge of the flood waters. In the part where it has not been canalised the Bahr-Yusef, skirted along its left bank by the dunes drifting before the desert wind, is a winding stream like the Nile, having, like it, its islands, sand- banks, eroded cliffs, and network of watercourses and false rivers. Its mean breadth is about 330 feet, but through it very little of the Nile waters are distributed. Feeders from the main stream, in traversing the intermediate plain, replenish the River of Joseph at intervals, thus making good the losses caused by evaporation. This phenomenon, of two parallel streams in one and the same valley, one the main stream discharging nearly the whole liquid mass, the other a small current winding through an ancient river bed, recurs in nearly all those valleys whose hydrographic system has not yet been completely changed by canalisation and drainage works. Several rivers skirted by embankments have also their Bahr-Yusef, like the Nile. Such in France is the Loire, skirted by the Cisse, by the waters derived from the Cher, the Indre, and the Vienne ; lastly by the river Authion, with its numerous ramifications.
The Fayum Depression.
About 300 miles from the point of bifurcation, the Bahr-Yusef penetrates into a lateral valley, where it ramifies in its turn. The eastern branch, which continues the river properly so-called, penetrates north-eastwards through a breach in the Libyan range, beyond which it rejoins the Nile above its delta. But the western branch trends abruptly north-westwards to a rocky gorge, at the entrance of which its course is regulated by a three-arched bridge built in the thirteenth century, and furnished with flood-gates allowing the stream to pass, or diverting it to the surrounding plains. Beyond the barrage the canal winds through a ravine about 6 miles long in the Libyan range, at the outlet of which it suddenly debouches in a valley of amphitheatral form, and nearly 110 miles in circumference. This is the Fayum depression, which is watered by an intricate system of canals, rills, and rivulets, ramifying like the veins and arteries in a living organism. At its lowest point this hill-encircled basin is estimated at from 86 to 116 feet ​below the level of the Mediterranean. Although apparently quite flat, it has a sufficient incline for the waters of the canal derived from the Bahr-Yusef to circulate throughout the whole area, imparting to the Fuyum a fertility rivalling that of the Nile delta itself. The superfluous water is collected towards the south in the small Lake Gara'a, or the "Hollow," whence it formerly penetrated far into the Wady Reyan. Towards the west the system of canalisation converges in a large lake about 30 miles long from south-west to north-east. This reservoir,
known as the Birket-el-Kerun, is but slightly brackish, and quite drinkable by animals when it floods the whole western depression of the valley. But when reduced by evaporation it becomes saline, and the margin is then covered with crystalline efflorescences resembling snow at a distance. In some places the muddy ground, clothed like the Algerian sebkhas with a slight incrustation of salt, forms treacherous quagmires, dangerous to man and beast.
Till recently the superfluous waters were supposed to escape through a rocky gorge in the hills north of the Fayum Valley, to the depression known as the ​Bahr-belâ-mâ, or "Waterless Sea." But this hypothesis has not been confirmed by the latest surveys, which have failed to discover any alluvial deposits indicating the presence of the stream at this point. The planks and masts of Nile boats spoken of by the Arabs are the stems of petrified trees, such as occur in various parts of the desert.
The Fayum, the Arsinoïtidis of the ancients, has been the scene of some of the most remarkable hydraulic operations of the old Egyptian engineers. Before the
interference of man the whole depression, which received all the waters of the Bahr-Yusef, formed an extensive inland sea. On this point tradition is unanimous, and in any case the continuous inflow must have flooded the cavity to a level sufficiently high to establish an equilibrium between the discharge and the loss by evaporation. The very name of Fayum (Piom, Phaïom), is said to mean "flooded land" in the old Egyptian language, although the Arabic word fayyum itself gives the appropriate sense of "corn-bearer." But after the Bahr-Yusef ​ was dummed at its entrance into the gorge, the "sea" became gradually reduced to a semicircular morass, and would dry up altogether but for the sluices which admit the water required for irrigation purposes. It was no slight matter to have thus reclaimed an extensive district, where as many as one hundred and fifty villages are said to have flourished. But according to the most probable supposition, supported by a careful survey of the whole region, the more elevated portion of the reclaimed land was converted into the famous Lake Mœris, which was one of the wonders of the old world, and which, centuries after its disappearance, must still be ranked amongst the most astounding works of man. The remains of embankments in some places 200 feet broad at their base, and 60 feet high, appear to represent on the east side the outer enclosures of the vast basin which during the floods received the discharge of the Bahr-Yusef, estimated at about the twenty-sixth part of the whole Nile. At the angles of the embankment are still visible the remains of pyramids recording the fame of Amenemha III., by whom this stupendous reservoir was created some forty-seven centuries before the opening of the Suez Canal, Herodotus, who may perhaps have seen though he did not measure it, gives it an enormous circumference, far greater in fact than that of the whole Fayum. According to Linant, it occupied an area of 120 square miles in the eastern portion of the Fayum, and at the end of the floods its volume must have exceeded 100,000,000 cubic feet, A small portion of this prodigious storage may have served to irrigate the western Fayum; but nearly all the overflow taken from the Nile during high water was distributed over the plains during the dry season, and sufficed to irrigate 450,000 acres of land. None of the great modern reservoirs can be compared with this great work, either for size or skilful design. Most of them are merely artificial lakes, which receive the whole fluvial discharge, and distribute the excess to the lower river basin. But the stream itself is continually sapping the foundations, and too often bursting the banks of its reservoir. It would, however, be difficult now to restore Lake Mœris, whose bed has been so greatly raised by alluvial deposits that the retaining walls and embankments would have to be carried several yards higher than formerly.
The Bahr-Yusef is continued under diverse names to the delta, but in its lower course the discharge is very slight. Nearly all its feeders, as well as the other channels and watercourses, are gathered up by the main stream at the head of the delta, whence they again ramify in a thousand branches over the plains of Lower Egypt. Hence at this point the Nile presents much the same appearance as in Nubia, or still higher up at the Khartum confluence. It glides in a slow and regular current between its banks, reflecting in its stream the trees, gray mud villages, and here and there a few white buildings. Nothing sudden or abrupt in this vast and sleeping landscape, whose monotony is broken only by a few dhahabiyé, or Nile boats, and above which is suspended an everlasting azure firmament. On either side the narrow plains, the cliffs, the ravines, and terraces succeed each other in endless uniformity. In this land of simple outlines, little surprise is caused even by the regular forms of the pyramids skirting the western ​edge of the plateau, at dawn pink and hazy cones, like flames of fire dimly seen in the brighter sunshine, at sunset gloomy triangular masses standing out against a brazen sky.
The Nile Delta
Below Cairo the two ranges of hills, confining the Nile as in a ditch, gradually retire as they merge in the plains, leaving the river to ramify and flow through divergent branches into the Mediterranean. The triangular disposition of this alluvial plain has caused the term delta to be applied to the whole region, and by
analogy to all districts of similar formation, however irregular their contours. Spite of all the changes that have taken place in the local geography since it was first described by Herodotus two thousand five hundred years ago, the Egyptian delta has remained a model of elegance in the harmony of its divergent branches and the indentations of its contours.
At the dawn of history the head of the delta lay more to the south, the bifurcation being situated some four miles below the present suburb of Bulak at Cairo. But the intermediate apex being unprotected by a system of embankments ​it yielded from your to year, from century to century, to the incessant action of the stream. The whole delta thus becomes displaced from south to north, according as the river beds are raised and the mouths extended seawards by the accumulation of alluvial deposits. At present the Batn-el-Bagara fork is over 12 miles from Cairo, following the windings of the island-studded stream, and has consequently been displaced at the annual rate of about 24 feet. Analogous changes have taken place throughout the whole of the delta, where the current has eaten its banks now to the right, now to the left, where simple channels have become broad watercourses, while copious streams have disappeared or shifted their beds.
Under the influence of the mystic ideas prevalent regarding the value of numbers, the old writers unanimously agreed to reckon seven chief branches in the delta, all the others being regarded as "false mouths." At the same time the normal direction of the streams required for irrigation purposes was carefully maintained during peaceful epochs by incessant dredging, embankments, and works of canalisation. It is now, however, no longer possible to trace the course of the seven ancient branches, which, left to themselves, resumed their erratic tendencies, shifting their beds with every fresh inundation. But there is a general agreement regarding their main direction, and many doubtful points of the hydrology of the Nile as described by Herodotus and Strabo have been cleared up by the naturalists of the French expedition to Egypt at the close of the last century.
At present two main branches only are enumerated, and these are indicated on the convex curve of the seaboard by two points formed by the tongues of alluvial land advancing continually seawards. They are the Rashid or Rosetta branch, identified with the Bolbitinis of the ancients, and that of Damietta, which formerly bore the names of Phatnetica and Bucolica. The Rosetta branch, some 14 miles the shorter of the two, but flowing in a bed from 30 to 50 inches lower, carries o£E the largest quantity of water, leaving not more than four-ninths to that of Damietta and the intermediate Menufieh channel, Nevertheless the Damietta River, thanks to its greater elevation, is much more available for irrigation purposes. The two branches, diverging like the radii of a circle, flow respectively north-west and north-east, advancing at their mouths some 5 miles beyond the normal coast-line. But, like all rivers falling into the Mediterranean, both are half closed by mud and sandbanks, barring the passage to large vessels. The western or Rosetta River has two channels from 7 to 8 feet deep, while that of Damietta, being less open, has a depth of scarcely 65 inches at its entrance. At high water, when there is a discharge of 470,000 cubic feet per second, the bar is reduced not more than 4 or 5 inches, its elevation depending more on the action ​of the marine currents than on the inland floods. But if its height is little modified, its position is often shifted several miles. During the inundations the current of the Nile is felt 3 miles seawards, and at times is strong enough to perceptibly reduce the violence of the waves, thus offering a temporary refuge to storm-tossed vessels.
The face of the delta is gradually encroaching on the sea, but at a much slower rate than might be expected from the quantity of sedimentary matter brought
down by the Nile. Even the estimate of 13 or 14 feet annually, as calculated by Elie de Beaumont on a study of the old and mediæval documents bearing on this point, seems to be excessive, slight though it be when compared with the growth of even smaller deltas, such as those of the Rhine and Po. The charts prepared by the French expedition at the end of the last century, and by M. Larousse in 1860, after the completion of the preliminary works for the Suez Canal, give a yearly increase of 130 feet for the Rosetta and 40 for the Damietta mouth. But these are merely local changes, and with the displacement of the channels the ​ accumulated alluvia are soon swept away and distributed along the coast by the marine currents. In many places these encroachments of the sea have been clearly determined. A distinctly perceptible coast stream sets steadily from Alexandria eastwards to Port Said, here and there developing slight local counter currents, such as the ebb and flow between the Rosetta mouth and Abukir Point. The effect of this stream is to erode the headlands and fill in the intervening inlets, thus restoring the original parabolic curve of the coast. Wherever an obstacle is met, it becomes attached to the mainland by a semicircular strip of sand. Shoals have thus been accumulated at the western pier of Port Said, although not in sufficient quantity to endanger the basins of the new port, especially as they may be easily reduced or removed by dredging. Altogether the annual growth of the delta cannot be estimated at more than 8 or 9 feet, so that since the time of Herodotus the mainland has encroached on the sea probably not much more than 3½ miles.
There may even be a complete equilibrium between the fluvial deposits and the erosions of the marine currents. At least the geological aspect of the coast is that of an ancient seaboard forming a continuation of the small limestone ridge at Alexandria, which at present terminates at Abukir Point. In the shallow waters the waves take advantage of every rocky projection, islet, or headland to deposit sandbanks, and thus gradually transform the irregular marine inlets into landlocked lagoons. Before advancing beyond the mainland the Nile had to fill up these lagoons, separated by strips of sand from the Mediterranean, and this work is not yet accomplished. It would appear to have even been delayed by a general subsidence of the land, such as has been recorded in Holland, on the coast of North Germany, at the mouth of the Po, in the Amazon estuary, and in so many other alluvial districts. Thus the artificial caves formerly excavated near Alexandria at a certain elevation above sea-level are now submerged. These are the tombs known by the name of "Cleopatra's Baths." To the same phenomenon should perhaps be attributed the restoratioa of certain depressions, which after having long remained dry have again been partly flooded.
But however this be, the lacustrine basins of the delta are now so shallow that they might easily be filled up. The eastern extremity of Lake Menzaleh, which is separated from the Nile basin by the embankments of the Suez Canal, has already become dry land, while the old bed of the Pelusium branch has disappeared. Since Andreossy's survey at the end of the last century, Menzaloh itself has been much reduced, and has now a mean depth of scarcely 40 inches, although covering a superficial area of about 500 square miles during the floods, when it communicates by temporary channels both with the Nile and the sea. At low water it is so beset with shoals and islets that most of the navigation is suspended.
Lake Burios, which lies east of the Rosetta branch in the northern part of the delta, is scarcely less extensive than Menzaleh, and like it rises and falls with the periodical floods. A sweet-water basin when fed by the Nile, it becomes brackish at other times, and communicates through a single permanent opening with the ​sea. Lake Mariut, close to Alexandria, has a circumference of at least 60 miles, and the steep cliffs towards the south and west give it the aspect of a true lake. Yet it was completely dry in 1799, when the English cut the embankment separating it from the sea. Since then it is once more diminishing, the breach having again been repaired. Whether the ancient Egyptians had also drained it by cutting off its seaward communications, or whether the mainland was then
more elevated than at present, Mareotis was certainly either altogether or partly dry at some remote epoch, for in its bed remains are found of old temples and statues.
begun their great works of canalisation. Doubtless most of the monuments erected near the river, such as the slabs of stone paving the great avenue of sphinxes at Kurnuk, the colossal statues of Memnon, and even a block bearing a comparatively recent Greek inscription, are now found buried to some depth below the surface. But this is due not so much to change of level as to subsidence, such huge masses naturally sinking gradually in the alluvial soil of the riverain plains. In the same way the erratic boulders in Switzerland and the colonnades of the Roman temples have sunk more and more below the surrounding surface. The Nilometer discovered by Girard in Elephantine Island is perhaps one of those monuments whose foundations have thus given way. Hence although the present high-water mark may exceed the old measurement by 8 or 9 feet, it does not follow that the bed of the river and its banks have been raised to that extent. Such a phenomenon could not be reconciled with the drying up of the old bed east of Asuan, which has now been abandoned by the stream.
Volume and Periodical Rising op the Nile.
The yearly overflow of the Nile, which renews all nature, and which was celebrated by the Egyptians as the resurrection of a god, is of such regular occurrence that it was formerly compared with the revolutions of the heavenly orbs. How could the riverain populations refrain from worshipping this stream, "Creator of wheat and giver of barley," a stream but for which " the gods would fall prostrate and all men perish"? "Hail, Nile!" sang the priests of old, "Hail, thou that comest to give life to Egypt!" According to its periodical return all things were and still are regulated—field operations, town work, civil and religious feasts. But at present it is easier to prepare for the rising waters, which are announced from Khartum thirty or forty days beforehand. They begin to appear nearly always on June 10th, at first "green" with vegetable refuse from the great lagoons of the upper basin. But the rise is very slight till about the middle of July, when the stream becomes suddenly swollen by the "red" waters from the Abyssinian highlands. Towards the end of August the Nile is nearly full, but continues to increase slightly till October 7th, when it usually reaches its culminating point. After this date the subsidence sets in and continues very gradually till the return of the floods the following June.
During the three months of high water the Nile sends seawards a liquid mass equal to about three-fourths of the whole annual discharge, or 3,150 billions cubic feet out of a total of 4,200 billions. High-water mark naturally diminishes down stream, falling from about 56 feet at Asuan to 24 or 25 at Cairo. Relying on some of the old texts, especially a much-disputed passage in Herodotus, some writers suppose that the level of the floods has been considerably modified since the first centuries of Egyptian history, although sufficient data are lacking to determine the point with certainty. In any case the mean elevation has undergone no change since the end of the eighteenth century of the new era. The careful measurements taken at that time have since been maintained, and they are ​found to coincide with those published by the naturalists of the French expedition, and with the uninterrupted series of modern observations. At the same time the floods oscillate within certain extreme limits. Sometimes there is insufficient water to supply all the canals, while in other years the overflow is excessive, and on these occasions the land does not dry soon enough to insure good harvests.
The rate of the land-tax generally varies according to the height and volume of the river. Hence the public crier appointed to proclaim the state of the
inundations has often been compelled by the Government to make false reports on this point. The day when the Nile reaches the proper level for cutting the dykes separating it from the irrigation canals is a day of rejoicing for all the riverain populations. Formerly a young maiden was on this occasion borne with great pomp to the river and cast into the seething waters, in order to obtain abundant crops from the local divinity. Now her place is taken by a dressed-up doll, which is still offered by the public executioner, a curious reminiscence of former an
sacrifices, . mm ​ The two zones of alluvial land skirting the Nile are intersected by numerous irrigation canals, which distribute the fecundating waters far and wide. Like those of other streams flowing through alluvial plains, the banks of the river are higher than the surrounding country. A cutting running transversely to the direction of the valley would show that from cliff to cliff the plain presents the form of a convex curve, so that at high water the stream occupies the most elevated level between the ranges of hills bordering both sides of its valley. From this central elevation the surface of the current inclines right and left, and the slope is continued in both directions across the riverain plains. This disposition of the ground is due to the greater quantity of sedimentary matter deposited along the banks of the stream. The waters have thus a double incline, that is, according to the general direction of the river valley, and according to the lateral slope of its banks. If they met with no obstacle in the irrigating canals, they would flow at once to the lowest level on either side, and convert the whole depression into a vast lake. Hence they have to be retained at the higher elevation by means of a transverse dyke, which is opened only when the upper levels have been sufficiently submerged. The overflow is then arrested in a second section also confined by embankment works, and in this way the water is distributed to every part of the surrounding plains by a system of canals disposed at successive levels.
Nevertheless the normal incline of the land has in many places been modified by the local alluvial deposits, and by the action of opposing currents in the lateral channels. The shifting sands brought by the winds from the neighbouring escarpments have also here and there raised the low-lying plains to a level with, and even higher than, the banks of the Nile, thus obliging the cultivators to change the whole plan of their irrigation works. Formerly, when the Nile was inhabited by five different species of the crocodile, the rising flood was preceded and heralded by the suk, a small and harmless variety, which was accordingly welcomed with much ceremony by the villagers, and even honoured with divine worship in many towns far removed from the Nile. Temples were dedicated to them, where they were kept alive, decked with armlets and pendants, and fed on the flesh of victims. But none of these saurians are now seen in the Egyptian Nile, even as high up as Thebes, although the canals intersecting Cairo were still infested by them at the beginning of the present century. None appear to be met below Omboe, south of Asuan, and this region of the cataracts is also inhabited by electric fish. But the hippopotamus has retreated still higher up to the neighbourhood of the Atbara confluence.
When the flood begins to subside, the water in the higher canals would at once flow back to the main stream were it not retained by sluices, and thus stored to meet the requirements of the following spring and summer. During the subsidence the level of the overflow is still maintained in the plains some 18 or 20 feet above the bed of the main stream. The peasantry also utilise the waters which filtrate laterally into the ground to a distance of some miles, but so slowly that the effect of the inundations is not felt for weeks and even months after the normal period of the rising. Even within 300 or 400 feet of the Nile the water in ​the wells does not begin to rise for eight or ten days, while at the distance of half a mile it is delayed till the floods are actually subsiding. Hence the curious phenomenon that, when the Nile is at its lowest ebb, the water in wells at a distance from the stream rises some 10 or 12 feet higher than the river itself. The cultivators are thus enabled to continue the work of irrigation, which would otherwise be impossible.
The canals and transverse ditches utilised as a means of communication between the villages cut up all the cultivated lands into a vast "chessboard," whose parting lines are, so to say, alternately raised and sunk below the surface. The vivifying fluid circulates everywhere, like blood in the animal arterial system. But the maintenance of this intricate organism involves enormous care, the least disorder in these almost level plains often sufficing to cause crevasses and obstructions, and converting the flowing streams into stagnant waters. Worn out by ceaseless toil,
vastly larger population.
The brown or blackish mud of the Nile is the only manure required for the crops. In the sun it becomes solid and may be cut into bricks or vessels; under the foot it is hard as stone, and in shrinking develops deep fissures in the ground. The old sandy or calcareous deposits, mingled at the foot of the hills with the rolled shingle washed down by floods anterior to the present geological epoch, are covered with a layer from 35 to 40 feet thick, forming an extremely rich arable soil which, if removed elsewhere, might suffice to fertilise a region a hundred times more extensive.
In its chemical composition this Nile mud, from which Egypt has been created, differs from that of all European rivers. Its analysis yields the most varied results according to its age, locality, and distance from the river. But it always contains a considerable proportion of carbonates of lime and magnesia, of oxide of iron and carbon, derived from decomposed organic substances. Palatable as it is, the Nile water nevertheless contains the refuse of all the provinces in its vast basin — the slime of the Atbara, animal remains from the Bahr-el-Azraq lagoons, sedge and other vegetable débris from the Kir and Gazelle rivers. Between the sands, argillaceous clays, and rugged crags of both deserts there thus intervenes a narrow belt of verdure created by the miscellaneous sedimentary matter in the course of ages washed down from half the continent.
* ↑ Length of the Misssouri-Mississippi 4,230 miles. "" Nile, with the Nyanza headstream 4,200 " "" Amazon, with the Apurimie 3,600 " "" Irtish-Ob 3,410 " "" Selenga-Angara-Yenisei 3,300 " "" Vitim-Lena 3,280 " "" Yangtse-Kiang 2,790 "
* ↑ Approximate area of the 'great river basins: — Amazon 2,800,000 square miles. Mississippi 1,390,000 „„ Nile 1,340,000 „„ Congo 1,280,000 „„
* ↑ E. O. Ravenstein, "Map of Eastern Equatorial Africa,"
* ↑ Area of the chief lakesof the world:—Superior,33,500 sqnare mfles ; Nyanza, 26,600; Aral, 26,300; Huron, 24,500 ; Michigan, 23.600; Eiie, 11,300.
* ↑ Nomenclature of the Upper Nile and its affluents: — Nile: Kivira, Somemet (between lakes Victoria and Albert): Men (in the Madi country); Karré (by the Ban people); Kir (by the Denkus); Yer (by the Nuer); Baihr-el-Jebel(by the Arabs between Lakes Albert and No); Bahr-el'-Abiad, or "White River" (by the Arabs below the Sobat). Yei: Ayi, Doghurguru, Jemid, Rodi, Bahr-Lau. Rol: Nam-Pol, Ferial, Welli, Yabo, Nam-Gel. Roa: Meriddi, Bahr-jau. Tenj: Tondy, Lessi, Doggoru, Kuan. Diur: Heré, Nyenam, Bahr-Wau, Ugul. Relaba. Pango: Ji, Dishi, Ugakser, Bahr-el-Homr. Famikam: Bahr-el-Arab, Linlui, Lol, Lollo, Komkom. Sobat: Bahr-el-Mogaté. Waik, Telfiu, Wah, or Tah (by the Shiluks), Pinyin, or Tilfi (by the Nuet), Biel, Kieti, Kidi, or Kiradid (by the Dinkas).
* ↑ Approximate estimate of the discharge of the two Niles at Khartum per second : — Bahr-el-Abiad. Babr-el-Azraq. High water 175,000 cubic feet. High water 213,000 cubic feet. Low water 10,000 „„ Low water 5,500 „„
* ↑ That is, the name of the triangular Greek letter Δ = D.
* ↑ • Discharge of the Nile at low water in 1875, according to Ali Pasha Mubarek :— Cubic feet. Rosetta branch 6,370 Damietta 3,550 Menufieh channel 670 Total 15,600 Mean 165,000
* ↑ Sir Ch. Lyell, "Antiquity of Man."
* ↑ Analysis of the Nile mud in Egypt, by Regnault, "Description of Egypt," vol. xx. Water 11 per cent. Carbonate of Magnesia 4 per cent. Carbon 9„„ Carbonate of Lime 18„„ Oxides 6„„ Alumina 48„„ Silica 4„„