An Egyptian oasis

by H. J. L. Beadnell

The term ‘oasis,’ an ancient Egyptian word signifying a resting-place, in its strict sense means a fertile spot in a desert, but in Egypt has usually been applied to a depression as a whole, each individual cultivated area being known by the name of the well from which its water is derived. The chief groups of oases in the Libyan Desert are the Siwan on the north, that of Kufra on the west, and the Egyptian, including the four large oases of Baharia, Farafra, Dakhla, and Kharga, on the east. The present volume deals more especially with the last of these.

The Libyan Desert is primarily divisible into two entirely different parts, distinguished by the presence or absence of surface accumulations of blown sand. Extensive dunes are confined to the western portion, where areas of hundreds of square miles are literally buried under deep seas of sand, blown into more or less parallel dunes of great height, lying N.N.W. and S.S.E., in the direction of the prevailing winds. In this country it is almost impossible to travel in a latitudinal direction, so that the sand-covered area forms an effective barrier between the Egyptian oases and Kufra, one of the strongholds and, at any rate until recently, the headquarters of the powerful Senussi sect. It is probable that, within the last century, the area of this sand has extended considerably to the south, as an old caravan road trending westwards, and believed to have originally connected the oases of Dakhla and Kufra, is now lost in the dunes. As long ago as 1874 some of the members of the Rohlfs expedition made an attempt to penetrate westwards from Dakhla, but on reaching the edge of the great sand-region, about 170 kilometres W.S.W. of Qasr Dakhl, were compelled to turn northwards and travel in a direction parallel to the lines of dunes, from which they emerged, after a long and wearisome journey of 400 kilometres, in the neighbourhood of the oasis of Siwa. Outlying portions of this sand invade the Egyptian oases; for instance, the depression of El Daila, lying to the west of Farafra, is to a great extent filled with blown sand, while an extensive area in the south of Farafra itself is buried under dunes.

On the eastern portion the sand is for the most part confined to isolated lines of dunes, the most remarkable being that known as the Abu Mohariq. This commences in latitude 29° 45′ north, at Arûs el Buqar, some 50 kilometres south-west of the Mogara swamp, in the low country to the south of the great east and west Miocene escarpment. From Arûs el Buqar the Abu Mohariq sand-belt runs in an almost straight and unbroken line across the Libyan plateau to the oasis of Kharga, through which it continues into the desert to the south. The average breadth of this line of dunes is only some 6 or 7 kilometres, whereas its length cannot be less than 650. Less extensive accumulations of blown sand are found in the oases themselves, in the depressions of Gharaq and Muailla to the south of the Fayûm, and encroaching on the cultivated lands of the Nile Valley between Bahnessa and Mellawi.

The eastern part of the Libyan Desert, in which are situated the Egyptian oases, is itself divisible into three areas having essentially different characters, the northern being an undulating rolling country of sandstones, grits, and gravels; the central consisting of bare elevated limestone plateaux; the southern a lower-lying expanse of rugged sandstone, broken only occasionally by ridges and bosses of granite and other crystalline rocks.

The Egyptian oases are deep and broad hollows or depressions in the Libyan Desert plateau. In position they appear to coincide with areas where rocks of comparative softness became exposed at the surface during the gradual lowering of the country by denudation. At such points the general rate of weathering must have become greatly accelerated, with the result that those vast depressions, which form such conspicuous features in the configuration of the country at the present day, were eventually cut out.

Underlying the greater part of the Libyan Desert are porous sandstones, and these, when pierced by deep borings put down from the lower-lying parts of the floors of the depressions, yield abundant supplies of water of remarkable purity. As these sandstones, as well as the shales with which they are associated, have a general dip or inclination from south to north, we are led to infer that they outcrop or come to the surface to the south, so that in all probability the water with which they are so highly charged has its origin in that direction. Whether the water obtains access to the sandstones by direct infiltration of the rains of Abyssinia or the Sudan, from the swamps of the sudd region of the Upper Nile, or from the Nile itself in the Nubian reaches, has not yet been decided with certainty. Recent observations, however, show that far more water is lost in some reaches of the Nile than can be accounted for by irrigation and evaporation, and it seems probable, therefore, that the excess disappears by infiltration into these sandstones.

Little is known of the early history of the oases, though the remains of ancient towns and cemeteries are abundant, and only await systematic excavation by Egyptologists to bring our knowledge of this part of Egypt into line with that of the Nile Valley. That the oases were inhabited in prehistoric times is evident from the occurrence of flint implements of Palæolithic types, both on the margins of the surrounding plateaux and within the depressions, though there is not at present sufficient evidence to enable us to affirm that the makers and users of these flints were contemporaneous with Palæolithic man in Europe. Implements of Neolithic type, often of finished workmanship, are, moreover, common in places on the floors of the depressions, but it is probable that these were in use well into the historic period.

In historic times the oases, according to Sayce, were governed by Egyptian Kings in the eighteenth dynasty (1545-1350 B.C.), and the oldest monuments as yet found in the oases-depressions date from this period. The most important of the earlier remains belong, however, to the Persian epoch, notably the temple of Hibis near the modern village of Kharga, which was built by Darius. Ptolemaic remains are also known in Kharga, but the greater number of the historical monuments date from the time of Roman occupation, when the oases appear to have attained a considerable degree of prosperity, which continued to Coptic times. Since the Mohammedan conquest of Egypt they have fallen into a state of neglect, and with the consequent diminution of the water-supply the population has decreased, and large areas of formerly fertile country have been absorbed by the surrounding desert.

It is interesting to speculate on the conditions which obtained in Kharga before the first borings were made, as at the present day we cannot point, so far as I am aware, to a single natural efflux of water on the floor of the depression. Surface-water, of quite a different character from the deep-seated water, is met with at comparatively shallow depths in various localities, and may either represent drainage water from the flowing wells and cultivated tracts, or be water which has escaped from the underground sandstones and found its way to the surface through fissures. Probably it is derived from both sources. In prehistoric times natural springs fed through fissures may have existed here and there within the depressions; and in any case it is probable that prehistoric man obtained sufficient supplies by sinking wells into the upper sandstones, which in some parts of the oasis occur at or near the surface, and contain large quantities of sub-surface or sub-artesian water. Nothing is known as to when flowing wells were first obtained, or by whom the original deep borings were made, and no traces of the implements used have been discovered. Many of these ancient wells, frequently over 120 metres in depth, continue to flow at the present day, although in most cases with a greatly diminished output; a few, however, are still running day and night at the rate of several hundred gallons a minute.

In some parts of the oases water-bearing sandstones occur at or near the surface, and from these beds the Romans obtained additional supplies by the excavation of underground collecting tunnels. Subterranean works of this description are found in all the oases, the most remarkable being in Baharia and at Um el Dabâdib and Jebel Lebekha in Kharga. They are frequently of great length, cut throughout in solid rock, and connected with the surface above by numerous vertical air-shafts. Many of the latter measure from 30 to 50 metres in depth, so that the construction of these and the horizontal carrying channels must have involved an immense amount of labour.