The Nile in 1904

42. Kharga oasis.

—Kharga, the easternmost of the two southern oases, is a north and south lying depression, mostly bounded by steep and lofty escarpments but open to the south and south-west. A great part of its floor, which is composed of the Nubian sandstone, is buried under sand accumulations. There are seven principal villages, besides numerous hamlets and smaller settlements, with a total population of under 8,000. Taxes are levied as in Dakhla and amount to slightly over £E. 1000. The adult palm trees in the oasis number about 60,000 and the cultivated lands have an area of some 4,500 acres, or half an acre and eight palm trees per inhabitant. The crops raised do not appear to be sufficient to support the population, as a certain amount of grain is imported from Dakhla. Dates are exported to the Nile valley, though in less quantities than from Dakhla and Baharia.

The general level of the floor of the oasis lies between 50 and 130 metres above sea level, though near Qasr Zaiyan a limited area appears to lie below sea level. Water is met with in most localities on digging to a moderate depth, but the best supplies are from deep wells; as in Dakhla the majority of the wells are of considerable antiquity, though some have been recently made with modern boring plant. With an increased water-supply cultivation could be very much extended, as there are large areas of unoccupied alluvium covered land within the oasis. The same difficulties exist in Kharga as in the other oases, though here perhaps aggravated by the encroachments and movements of blown sand, namely, the lack of control of the wells and water-supply and the apathy of the inhabitants generally.

43. Baharia oasis

, lying 180 kilometres west of Minia, is a large natural excavation 150 metres deep and entirely surrounded by escarpments. The cultivated lands bear a very small proportion to the total oasis-area; their general level is 110-115 metres above sea level, rising to 155 metres at Ain-el-Haiss in the southern part of the depression. There are four chief villages with a population, inclusive of outlying settlements, of just over 6,000. The standard of public health in this oasis is low, mainly owing to febrile disorders. The total area of cultivated land is about 2,500 acres (barely ¹⁄₂ an acre per inhabitant), largely made up of palmgroves; rice, wheat and barley are grown, but the area sown with cereals has of late years being decreasing in extent owing to a diminished output from the springs. Baharia is par excellence the date-producing oasis of Egypt and very large quantities are annually exported to the Nile valley; besides date-palms the gardens contain numbers of olive, apricot and other fruit trees. Taxation is on palm trees and land.

The water-supply is derived from the Cretaceous sandstones forming the floor of the depression, the water rising naturally to the surface of the lowest areas. In numerous cases long adits have been driven into the rock to obtain an increased supply; these tunnels communicate with the surface of the ground by a series of air shafts; they mostly date from early times. No deep wells appear to exist in the oasis and certainly no borings have been made in modern times. The fall of the water-level is probably due to the gradual choking of the passages; an unsatisfactory and laborious method of cleaning out wells is in vogue but little trouble is taken to prevent the deterioration of the water-supply generally. Practically all the available land in this oasis is under cultivation, although with the reduced output of the springs the supply is barely sufficient for efficient irrigation.

44. Farafra oasis

 occupies a large semicircular depression 300 kilometres west of Assiut. The floor is formed of the white chalk at the top of the Cretaceous, but at Ain-el-Wadi, a spring in the north part of the depression at 26 metres above sea level, the underlying beds are locally exposed. The solitary village of Qasr Farafra is situated on the western side at 76 metres above sea level, and contained 542 inhabitants at the last census. In the entire area there are some 20 springs, mostly grouped round the village, each irrigating a small patch of cultivated ground; the total area of the latter, including the few palmgroves, probably does not amount to 500 acres. Wheat, barley, durra, rice, onions and some fruit are grown, and small quantities of dates and olives are exported; formerly the olives of Farafra were celebrated for their quality, but of late years the trees have deteriorated.

The water rises as springs from the white chalk and does not necessitate the use of lifting appliances, though the output appears to be decreasing through natural causes. There are a few examples of horizontal conducting channels of ancient date and two or three of the springs appear to have deep vertical shafts as in the ancient wells of Dakhla. Sweet and brackish water-holes occur in several outlying localities within the depression, as well as in the neighbouring little known oasis of Iddaila to the west. Owing to the absence of waste pools and marshy land the climate of Farafra is more healthy than that of the other oases.

45. The Geology of Egypt

[8]. The north-east corner of Africa, lying between the Red Sea on the east and the sand merged portion of the Libyan Desert on the west, and stretching from the Mediterranean to the 22nd parallel of north latitude, both in its topographical and geological characters is distinctly tripartite, as follows:—

(1) A rugged broken undulating sandstone desert, forming the southern part of the country;

(2) Elevated plateaux, for the most part of limestone, stretching from lat. 25° N. (approximately) to the Mediterranean;

(3) The mountainous igneous range of the Red Sea Hills, with peaks over 1800 metres (6000 feet) in height.

As a whole one of the most waterless and desolate areas in the world, the country is traversed from south to north by a narrow highly cultivated and thickly populated strip of alluvial land, formed and watered by the Nile. In the southern sandstone country the river occupies only a shallow valley, but to the north flows over the floor of a deep gorge cut down from the surrounding limestone plateaux. On either side of the river are alluvial plains of varying extent, composed of the finest loam, a fertile soil for the most part formed by the disintegration of the volcanic rocks of the Abyssinian highlands, annually denuded by rains and brought down by the Atbara and Blue Nile floods and deposited in the lower courses of the river. Unlike most countries therefore, the soil of Egypt has no connection with the underlying rocks, being entirely of extraneous origin and owing its existence absolutely to the peculiar conditions of rainfall in Abyssinia and the direction of drainage from the watersheds of that country.

46. Igneous rocks.

 The most ancient rocks in Egypt are found in the central igneous ranges of the Red Sea Hills and in the crystalline floor underlying the sandstones in the southern part of the country.

In Nubia the crystalline rocks consist largely of granite and gneiss, with associated diorites and schists, traversed by basaltic and felsitic dykes. Cataracts have been formed at those points where the river crosses the hard igneous belts, which may be regarded as the summits of the higher ridges of an old eroded continental land surface.

In the Red Sea Hills the most ancient rocks are the gneisses, schists, and slates, constituting the metamorphic series of Jebel Meeteq. Next in succession is a volcanic group, consisting of dolerite and sheared diabases in the south and of dolerites, andesites, tuffs and agglomerates in the north. These volcanic rocks are underlaid and intruded by still younger quartz-diorites and grey granites, and like them are pierced by masses of red granite and dykes of quartz felsite and dolerite. The red granite is itself traversed by dykes of diabase, which are thus the youngest of all, except for the still more recent andesitic intrusions into the Eocene limestones (occasional occurrences of which are met with on the plateaux on both sides of the Nile valley), and the basaltic sheets which commonly mark the base of the Oligocene sandstones in the north of the country.

The whole of the Red Sea Hills igneous complex has been planed down by marine erosion, the oldest sedimentary deposits being laid on to the smoothed denuded surfaces.

47. Sedimentary rocks.

 Geologically the sedimentary deposits of Egypt are not of great age. Broadly they consist of a great development of Upper Cretaceous and Eocene strata, followed by more restricted deposits of Oligocene and Miocene age, the still younger formations being represented only by comparatively local though important, accumulations. As a general rule the different members of the Cretaceous and Tertiary succeed each other in regular order from south to north, the strata being undisturbed and dipping northwards at a very low angle.

48. Upper Cretaceous.

 The Cretaceous system in Egypt is divisible into three main groups, (1) a great thickness of freshwater arenaceous sediments known as the Nubian Sandstone, of Senonian age in the south (Dakhla, Nile valley, and southern part of Eastern Desert), and Cenomanian age in the north (Baharia, Abu Roash(?), and Wadi Araba); (2) 300 metres of argillaceous deposits with bone-beds near the base, of Senonian age; (3) a deep water foraminiferal white chalk (Danian) 60 to 100 metres thick, especially developed in the region of the oases to the west of the Nile.

The Nubian Sandstone, the oldest sedimentary deposit in Egypt, occupies a very large area, especially in the south; wherever its base is exposed and has been critically examined, the sandstone is found to be laid on to the denuded surface of the underlying crystalline rocks. Thinner argillaceous bands are almost everywhere associated with the sandstones and the latter vary much in colour, texture, and hardness. In its widest sense the term “Nubian Sandstone” includes deposits of much greater age than Upper Cretaceous, undoubted Carboniferous fossils having been detected in some localities. The formation must be regarded as representing the slow accumulation of sediment in immense inland lakes during a great lapse of time. Although temporary marine invasions left their mark at intervals, it was not until the Cenomanian that continued depression caused a steady recession of the shore line from north to south, so that in Senonian times practically the whole of the country was occupied by the Cretaceous sea.

North of Silsila in the Nile valley the sandstones gradually give way to a series of flaggy ripple-marked sandstones alternating with sandy shales and clays, at the top of which are beds rich in bones and coprolites of fish, associated with hard oyster-limestones, overlain in Wadi Hammama, E.-N.-E. of Qena, by a limestone containing abundant remains of cephalopoda; these beds are of Upper Senonian (Campanian) age. East of Sabaia, in the Nile valley, they are followed by a 200 metre series of finely laminated clays, separated by bands of marly limestone, the greater part of which is of Cretaceous age and homotaxial with the Exogyra clays and white chalk (of Campanian—Danian age) which in the southern oases follow on the rich bonebeds overlying the Nubian Sandstone.

Anterior to and during the deposition of these clayey beds in the south, thick accumulations of limestone were being formed in the more open sea to the north and are visible to-day in the Cretaceous area of Abu Roash near the pyramids of Giza, (and to a lesser extent in Jebel Shebrewet on the Gulf of Suez), where a great complex of limestones of Turonian and Senonian ages occurs. Finally a deep sea deposit of white chalk forms the summit of the Cretaceous throughout the Western Desert.

49. Eocene.

 Our knowledge of the junction of the Cretaceous and Eocene in several parts of the country leaves much to be desired. Where the Eocene is most fully developed its basal member consists of a group of green argillaceous deposits, known as the Esna shales, well seen at the base of the cliffs throughout the Esna-Qena reach of the valley. These beds everywhere pass conformably upwards into the Lower Eocene (Libyan) limestones above, but in the Nile Valley and the Eastern Desert the exact line of demarcation between them and the lithologically similar Cretaceous clays below is still somewhat obscure. In Kharga and Farafra they form a well-marked band between the White Chalk (and associated clays) at the top of the Cretaceous and the Libyan limestone of the Lower Eocene. The Esna shales may in fact be regarded as passage beds, and where they exist appear to bridge over the lapse of time which is represented by a decided unconformity between the Cretaceous and Eocene in the north of the country, as in Baharia Oasis and at Abu Roash.

The thick mass of limestone which forms the plateaux and cliffs on both sides of the valley from lat. 25° N. to Cairo is of Lower Eocene (Libyan stage) and Middle Eocene (Mokattam stage) age. These limestones, frequently nummulitic and typically marine calcareous accumulations, exceed 500 metres in thickness, and over a wide area are unrelieved by a single band of clay or sandstone. Towards the summit of the Middle Eocene, however, terrigenous deposits were laid down, the Upper Mokattam consisting of an alternating series of impure limestones, clays, and sandstones. In the Fayûm the Middle Eocene is followed by a great thickness of fluvio-marine deposits of Upper Eocene age, in which the remains of the animals that inhabited the land to the south and the adjoining seas at the time are abundantly preserved.

50. Oligocene and Miocene.

 Throughout Oligocene and Miocene times conditions similar to those which led to the deposition of the Upper Eocene formation in the Fayûm prevailed, accompanied by a continual retreat of the sea to the north. In the littoral area marine beds were intermingled with the sediments brought down by rivers from the land to the south; and throughout these deposits the remains of land animals and great quantities of large silicified trees are common. A considerable part of the deserts east and west of the valley north of lat. 29° 30´ is covered with deposits of this age, and shallow water Miocene beds, unconformably overlying the Eocene, form marked flanking plateaux to some of the igneous ranges of the Red Sea Hills.

51. Pliocene, Pleistocene and Recent.

 In Pliocene times the relative areas of land and sea approximated to those of to-day and powerful earth-movements initiated the formation of the lower part of the Nile Valley. The determining faults and the huge blocks of displaced rock are visible along the cliff walls in many parts of the valley, and at Gebelain isolated ridges of highly tilted limestone protrude above the floor of the trough, though as a rule, except near the cliffs, the faulted rocks are invisible, being buried under great thicknesses of lacustrine and fluviatile deposits. A few kilometres south of Jebel Silsila, however, Eocene and Cretaceous limestones are met with at river level in the centre of the valley and point to the Kom Ombo plain being let down by a fault of over 400 metres throw.

The Nile Valley trough or “grab” became a marine fiord in later Pliocene times, sea-beaches being formed up to 70 metres above present sea level. Extensive terraces of gravel, perched up on the surrounding slopes of the Fayûm, prove that the sea, or a great inland lake, stood at 180 metres in latest Pliocene or early Pleistocene times. From this time also dates the Red Sea (in its modern aspect), the highest Older Pleistocene coral reefs being now found at some 200 metres above sea-level; younger reefs associated with later Pleistocene gravels occur at a lower level. In later Pleistocene and early pre-human times, under the very moist climate which preceded the present desert conditions, the Nile Valley north of latitude 24° was occupied by a series of deep freshwater lakes, perhaps co-existent with that in which the Fayûm gravel terraces were accumulated. The denudation of the surrounding country was rapid, and tributary streams from the plateaux on either side brought down fine limestone detritus, which was deposited along the margins of the lakes in the form of compact beds of re-made limestone, interbedded with frequent layers of conglomerate and gravel, washed down by the larger streams and by torrential floods. In the quieter parts of these lakes clays and calcareous tufas were laid down and are visible to-day from Kom Ombo to Heluan. Subsequently, owing to the breaking down of the dividing barriers, or as the result of a general slight elevation, drainage became more pronounced and the river cut its way down through these lacustrine deposits. It was probably at this time that, following the partial removal of the gravel ridge between the Fayûm and the valley, part of the drainage obtained access to the Fayûm depression and a lake, the precursor of the historical Mœris, was formed. Subsequently, under climatic conditions similar to those of to-day, the accumulation of Nile alluvium commenced within the wide trough cut out in the older lake beds. Flood plains were formed on either side of the river, and by successive deposits, at the rate of about twelve centimetres a century, were built up to their present level.

52. Economic products.

 Limestones for building and other purposes are abundant in the Lower and Middle Eocene formations, though as a rule of only medium quality. The chief quarries are those of Jebel Mokattam, Tura, Heluan, Abu Foda, Harîdi, and el-Tarif. At Isawia, near Tahta, a fine tough freshwater tufaceous limestone of Pleistocene age occurs, and was largely used in the construction of the Assiut barrage. Clays of good quality are not widely extended, though certain bands of the Esna shales are very largely used near Qena in the manufacture of pottery. For bricks the Nile alluvium is used throughout the country.

Sandstone is quarried for local purposes at J. Ahmar near Cairo and in several localities in the south part of the country; it was formerly extensively quarried at J. Ahmar for the temples of the Delta, at J. Silsila for those of Upper Egypt, and at Girtassa, south of Assuân, for the Nubian monuments. Although a fairly hard and good weather-resisting stone when carefully selected, the frequent presence of soft uncemented and clayey laminae gives it an unreliable character, and a good deal of the decay of many of the ancient Egyptian monuments is attributable to this cause.

Numerous rocks in the Red Sea Hills and the Nile Valley were worked in Egyptian and Roman times for ornamental purposes; among them may be specially mentioned the purple imperial porphyry of J. Dokhan, the green breccia of Wadis Hammamat and Dib, the dolerite of Wadi Esh, and the hornblende granite of the first cataract. In modern times local granite was used throughout the Assuân dam and an Oligocene basalt is quarried at Abu Zabel and used for road-metal in the capital and other towns.

Old workings and mining camps are of common occurrence in many parts of the Eastern Desert and there is no doubt that considerable quantities of gold were extracted by convict labour. The quartz lodes traverse not only the metamorphic rocks but also some of the granites. Iron (hematite, limonite), copper (chrysocolla, copper pyrites) and lead (galena) bearing veins also occur, and turquoise, jasper and chrysolite are found in certain localities. Petroleum and sulphur occur sparsely near J. Zeit, and gypsum in large quantities in many parts of the country.

Phosphate deposits in the form of accumulations of bones, teeth and coprolites of fish in compact beds, have a wide distribution in the Eastern Desert, the Nile Valley and the southern oases, though these beds have not yet received the attention their importance deserves. Better known are the nitrate bearing clays which are so highly valued and largely used by the fellahin throughout the country. The chief horizons are the Esna shales and the underlying cretaceous clays, but disintegrated clays of every age are worked throughout the country, though their nitrate content may be very low and their salt content high; more prized still is the material from the middens marking the sites of ancient towns.

Natron (carbonate of soda) and salt are associated in considerable quantities in Wadi Natrun, and the latter is widely distributed in limited quantities throughout the country, the main supply being however obtained by evaporation from the shore lagoons along the coast of the delta. Rock salt of fine quality occurs in many localities, notably in the Eocene limestones three to four days east of Assiut.

APPENDICES

N.B.—In Appendix L, the gauges are recorded in two different methods. If the fall or rise of water surface is gradual throughout the year, the gauges are recorded in five daily intervals. If, on the other hand, the rise and fall is gradual for the first four and last three months of the year, but the changes are abrupt in the remaining five months, the gauges are recorded in five daily intervals for seven months and daily for five months.

Appendix A.

Table I.—Areas of Catchment Basins of the Nile.

Appendix B.

Table II.—Slope of the Nile in flood from the Ripon Falls to the Sea.

Appendix C.

Table III.—Velocity of the Nile in its different reaches.

Table IV.—Time water travels along the Nile.

Appendix D.
DISTANCE FROM THE SEA TO CAIRO, CAIRO TO ASSUAN, ASSUAN TO KHARTUM, KHARTUM TO GONDOKORO AND GONDOKORO TO THE RIPON FALLS, AND BACK.

Tables V and VI.—Distances in kilometres from the Barrage to the sea down the Damietta and Rosetta branches, and vice-versa, measured on the steamer track or Deep Channel in kilometres.

Table VII.—Distances in kilometres from Barrage to Assuan and back in kilometres measured on the steamer track or Deep Channel.—Upper-Egypt.

Table VIII.—Distances in kilometres from Assuân to Khartoum and back.

Table IX.—Distances in kilometres from Khartoum to Gondokoro and back.

Table X.—Distances in kilometres from Gondokoro to Ripon Falls and back.

Table XI.—Distances from Khartoum to Rosaires and back along the Blue Nile.

Appendix E

Table XII.—Details of observed discharges from Sir W. Garstin’s report on the Basin of the Upper Nile.