An Egyptian oasis

The Skill of the Ancients in Well-Boring — Present State of the Ancient Wells — Ancient Methods of Boring — Wooden Casing — Introduction of Machinery by Egyptian Government — Native Methods of Boring at the Present Day — Cleaning of Wells — Divers and their Work — Recent Boring Operations — American Steam-driven Boring Rigs.

Olympiodorus, writing more than 1,500 years ago, remarked that the inhabitants of the oases were celebrated for their skill in sinking wells. Although at the present day a large proportion of the very ancient wells are completely sanded up, or have suffered great deterioration in respect of their flows, there are still many examples to be met with where bores, certainly between 2,000 and 3,000 years old, are still producing strong discharges of water at the rate of hundreds of gallons a minute by day and by night.

Although scores of the old wells have been cleaned out and repaired in modern times, not a single instance has come under my notice of the finding of implements used by the well-borers of ancient times. We know, however, that the bores were in practically all cases lined to a considerable depth with wooden casing, manufactured from the wood of the doum-palm, date-palm, or acacia, which doubtless were then, as now, cultivated in large numbers in the oasis. The timber was carefully fashioned into the required lengths and fitted together by water-tight joints. During the cleaning operations to which many of the old wells have been subjected in modern times, portions of the ancient casing have frequently been extracted, and some of the examples which I have examined, especially those made of acacia, proved to be in an excellent state of preservation. The wood of this particular tree—‘sunt,’ as it is locally called—has remarkably enduring qualities both in and out of water, though not when subjected to alternations of wet and dry. Still, that it should in some cases have retained its original qualities since Roman times is noteworthy.

It is quite evident, from a comparison of the ancient timbering and casing with those manufactured and used by the inhabitants of the oases at the present day, that the methods of well-sinking in modern times are in many respects identical with those anciently employed. This is especially the case in sinking through the superficial strata—i.e., those overlying the actual beds in which the artesian water is held—though of the methods formerly practised for carrying the bore through the Artesian-water Sandstones nothing is known.

We have little, if any, information as to how the inhabitants kept up their water-supply after the withdrawal of the Romans. Probably there was a gradual diminution of the total output, as it is not at all certain that any new wells were subsequently sunk—at any rate, until after the introduction of modern hand-boring machinery some fifty or sixty years ago. On that occasion one Hassan Effendi, a servant of a French engineer of the name of Lefèvre, was sent out by the Egyptian Government to instruct the inhabitants in the use of the new machinery. Judging from their present proficiency in sinking wells through difficult strata with the most hopelessly worn and antiquated tackle, the natives did not take long to learn the new system. Unfortunately, when left to themselves without adequate supervision, they promiscuously sunk a great number of new bores, without regard to the probable effects on the older wells irrigating the existing palm-groves and cultivated lands, with the result that, more especially in the oasis of Dakhla, a great deal of harm was done. Whole districts suffered a general lowering of water-level, many of the wells ceasing to flow altogether. This was the direct outcome of the excessive number of new bores put down in certain districts where the inhabitants were sufficiently rich and influential to get and retain possession of the majority of the newly-imported boring-rigs.

About ten years ago I studied the method of well-sinking used in the oases, and found it to consist of a combination of ancient and modern boring practices. Owing to the difficulty and prohibitive cost of transporting heavy steel tubes across the desert, the use of locally-made wooden casing could not be dispensed with, and as casing of this description could not possibly be made of sufficient strength to stand ‘driving,’ the upper portion of the well had of necessity to take the form of an open shaft carried down as near as possible to the water-bearing beds, the actual boring by means of the drilling-plant being confined to the later stages.

The first operation consists in sinking a rectangular shaft, usually 2 metres square; this work is carried out by hand, the ordinary native ‘fass’ being almost the only implement used. As the shaft is cut out it is timbered with lengths of palm-wood strung one below the other, to prevent the walls from falling in. The excavation is carried as deep as possible, the limit generally depending on the amount of sub-surface water met with. In the oasis of Dakhla, where the superficial strata consist almost entirely of clays, it can usually be continued to a depth of about 30 metres; but in Kharga the depth varies considerably, owing to the more frequent intercalations of water-logged sandstones. The success of the prospective bore depends to a very great extent on the depth to which this preliminary work is carried, as the succeeding strata, lying between the base of the shaft and the true artesian beds, have to be pierced by a hole unprotected by casing, and if of any very considerable thickness, caving beds are likely to greatly interfere with, if not prevent, the progress of the work.

On completion of the timbered shaft the wooden casing is placed centrally in position, so as to form a vertical pipe from the base of the shaft to the surface of the ground. The pipe may be either square or round in section, and is usually made of acacia, though hollowed trunks of doum-palm are sometimes used. It consists of a number of different sections, joined together in such a way as to leave no projecting portions either within or without, the whole length of casing thus preserving a constant diameter from top to bottom. As a rule, the joints are so well formed that the pipe is, to all intents and purposes, water-tight after a short soaking. The square variety of casing usually has an inside width of 36 centimetres, the thickness of the wood being 4 or 5 centimetres; the circular, and perhaps more common, variety is made with an inside diameter of 35 centimetres, except when required for insertion within a previously fixed string of casing, when smaller sizes have to be used. The casing, of course, eventually forms the actual channel through which the artesian water flows to the surface.

The space intervening between the sides of the timbered shaft and the central pipe is then filled in with a mixture of sand and clay, firmly packed down, so as to hold the pipe securely in position, and prevent the escape of water should any of the joints become leaky.

Up to this point there is good reason to believe that the modern practice is similar to, if not identical with, that anciently used; but in the complete absence of evidence, documentary or otherwise, we cannot conjecture how the old well-sinkers proceeded in subsequent stages. We surmise, however, that, given sufficiency of time, they were possessed of the requisite patience and skill to overcome all ordinary obstacles—as has been the case for generations in China—and it is probable that the percentage of wells abandoned was not greater than it is at the present day in countries where well-boring has become an art, carried out by means of scientifically designed machinery.

The second part of the modern operations is conducted with an ordinary percussion hand-boring outfit of European manufacture. As the method of boring with this type of rig is essentially the same all over the world, we only propose to describe it in brief. The proceedings commence with the erection of a timber framework, or derrick, immediately over the mouth of the pipe; at the summit of the derrick is a pulley, over which passes the rope or chain which connects on one side with the drum of the winch, and from the end of which, on the other side, are suspended the actual tools with which drilling is continued. The boring-rod is made up to the required length by screwing together a number of 10-foot sections, the terminal length being a shorter rod fitted with a chisel, auger, or sand-pump, according to the work in hand.

The rate of progress depends to a great extent on the rapidity with which the blows of the chisel are delivered. This, of course, varies considerably, depending on the depth of the well and consequent weight of the rods in use. Where the weight is great and the formation sticky, the rods have to be lifted by means of the winch, and not more than two or three blows a minute can be struck. When the rods are light or working freely, as, for instance, when drilling in sandstones, the winch can be dispensed with, and the necessary motion conveyed by means of a lever actuated by a number of men. In this way progress can be very much accelerated, as many as twenty or twenty-five blows being delivered per minute. At the best, however, the method of drilling by percussion with a solid rod is necessarily slow, owing mainly to the fact that the terminal tool cannot be changed or withdrawn without the entire length of rod being taken to pieces. It is seldom, therefore, that a well of 120 to 150 metres is completed in less than five months, and the average time taken is more like nine months or a year.

It will readily be admitted that this method of sinking wells is in many respects well adapted to the local conditions obtaining in such isolated localities as the oases, where time is of little consequence to the inhabitants. The completed wells are frequently equal in almost every respect to those put down by means of the most up-to-date appliances; in fact, the only objections to the method are its slowness, the limited depth to which it is applicable, and the difficulty of fixing to the wooden casing satisfactory appliances for regulating the discharge.

The patience and industry of the inhabitants of the oases are well exemplified by their unceasing attempts to maintain undiminished the water-supply on which their very existence depends. The population must always have borne a direct ratio to the total discharge of the wells, as on the latter depends the amount of food-supplies which can be raised. At no period, as far as we can judge, has the output of the wells been greater than the requirements, and it is probable that there has always been a population somewhat in excess of that which could be supported by local products, the surplus portion being disposed of by emigration to the Nile Valley.

The methods of dealing with wells in which the flows have diminished or altogether ceased are of considerable interest, as they have given rise to a class of men called ‘ghattasin’ (divers), which one would never have expected to find in such remote and arid localities as the oases of the Libyan Desert.

It is seldom that the poorer inhabitants can command the use of a hand-rig for the cleaning of their wells, so that they usually have recourse to appliances of the most primitive description. Perhaps the simplest form consists of a short iron rod, a sort of crowbar or jumper, suspended from a palm-fibre rope, and with a tiny basket attached to the lower end. In some cases the end of the jumper is itself fashioned into the form of a cup, so that the basket of plaited grass or palm-leaf can be dispensed with. The rod is worked up and down in the bore, so as to stir up the sand and clay at the bottom, which settles in the basket or cup, and is periodically hoisted to the surface. The rope is worked over a wooden roller fixed alongside the mouth of the well, a contrivance which enables the up-and-down motion to be given with a minimum of energy and friction. The process is often continued for years, the material which can be removed in a day only amounting to a few handfuls.

The above method is only applicable to bores in which the wooden casing is more or less intact. Where the latter has rotted and allowed the sides of the well to collapse, a much more difficult and complicated procedure is necessary before the discharge can be re-established. In a case of this sort the original rectangular shaft has to be entirely cleared of material, and a new string of casing placed in the exact position occupied by the original pipe of the well. Moreover, the timber of the shaft itself has generally to be repaired or entirely renewed, as otherwise there would be very great danger of the sides collapsing when the material from within was removed. The process is rendered extremely difficult and laborious by reason of the entire work having to be carried on under water. Although a well may have stopped flowing, the passages are never so completely blocked as to altogether prevent the water from rising to within a few feet of the surface, and any excavation made will always be found to become speedily filled with water. The work can, therefore, only be carried out by men who have trained themselves to remain and work under water, and a limited number of these divers are found in most of the Egyptian oases.

I have frequently watched and chatted with the divers at work on old wells, both in Dakhla and Kharga. Unlike the usual custom of remunerating men employed on well-cleaning by shares of the resulting water, divers are generally paid in cash at the rate of about a shilling a day, each man receiving his food as well. The descent is always made feet first, hand over hand down a rope stretched from the top to the bottom. When the diver wishes to return to the surface he signals by a motion of the rope to those at the top, who promptly haul him up.

The rate of progress depends, of course, on the depth at which the work is proceeding. In a well I once visited near Hindaw, in the oasis of Dakhla, divers were working at a depth of 29 metres. Each man descended six or seven times a day, remaining on each occasion from two to two and a half minutes under water. Work had been in progress here for four years, and the excavation was still 16 or 17 metres from the bottom of the shaft.

The excavated material is placed in baskets, which, when full, are drawn up by hand. As soon as the shaft has been cleared to the bottom the new casing is inserted, the intervening space filled in, and the work carried on as in a new bore. Many extinct wells have thus been put into good working order, though in some cases the divers have been unable to overcome the difficulties encountered, and the wells have been finally abandoned after months, or even years, of labour.

In the reclamation operations conducted in the oasis of Kharga during the last two or three years, both hand and steam boring rigs have been employed, steel casing being used for all wells. The cost per foot drilled is somewhat in favour of the hand-rigs, but the rate of progress is far more rapid in the case of the steam-driven machines. The method used with the hand-machines is the same in principle as that employed by the natives and already described, with the exception that the preliminary excavation is dispensed with, the bore being drilled from the surface and lined with metal casing down to the Water-bearing Sandstones. The casing is driven by means of a heavy weight, or ‘monkey,’ attached to the boring-rod.

The steam-rigs used are of American manufacture, and of the design usually employed in the oil-fields of the United States. The method is a modern adaptation of a practice employed from very early times in China, free-falling tools attached to a flexible rope being used in place of a solid iron rod. The actual drilling tool, which is of great weight, is suspended from a cable, and worked by steam-power in such a way as to give a rapid succession of blows of such force as to cut out a circular hole through the hardest of rocks. The outfit consists essentially of a very high derrick, a large drum on which the cable is wound, and a specially-designed engine worked by steam, the boiler in which the latter is generated being usually placed on a separate carriage. A second and smaller drum is provided for a fine wire rope, which is used with various forms of sand-pump for cleaning out the loose sand or sludge formed by the drilling tool.

These steam-rigs necessitate the employment of skilled drillers, and are, moreover, with difficulty kept in proper repair in out-of-the-way localities. Their initial cost is high; they are extremely cumbersome to drag from one site to another over the soft surface of the desert, and they consume a large quantity of fuel. These drawbacks are, however, partly, if not entirely, counterbalanced by the rapidity with which the work can be carried out, the average rate of progress under the conditions met with in the oasis being 5 to 7 metres per ‘shift’ of eight or ten hours. In the water-sandstones I have known Mr. B. F. Whiting, who was recently my drilling superintendent in the oasis, carry a bore down as much as 20 or 25 metres in a single shift. Breakdowns are, of course, not infrequent with this system of boring, but the American drillers are remarkably proficient in the recovery of lost tools.

The Winds — Wind and Sand as Agents of Denudation — The Combat of the Inhabitants with Sand-laden Winds — The Dune-Belts — Origin of the Sand — Composition of Dune-Sand — The Forms of Dunes — Dimensions and Rate of Movement — Irresistibility of Blown Sand — Protection afforded by Topographical Features — Effect of Artificial Obstructions on the Formation of Dunes — Fixing of Dunes by Vegetation and Moisture — Storm-Walls and Fences — The Dunes of Gennâh — Wind-borne Sand beneficial in the South of the Oasis — Formation of Terraces of Wind-borne Materials — Encroachment of Dunes in the South of the Oasis.

No one who has sojourned in Kharga long enough to compare it with other parts of Egypt will feel inclined to dispute the statement that the depression is one of the most windy places in the country. Only one day in ten or eleven is calm, though if the wind has been blowing fairly steadily during the day it generally drops at night. Five times out of six its direction is from the north, and when unaccompanied by sand the wind acts as a welcome moderator of the temperature.

In a desert region, owing to the surface being unprotected by vegetation, there is nearly always an abundance of weathered material loosely exposed on the surface, the lighter portions of which are quickly swept up and carried along as soon as the wind attains even a moderate velocity. On the actual dunes even a light breeze is sufficient to set the surface-layers in motion, while on the open plain the wind becomes visibly charged with sand directly it attains the velocity of a moderate breeze. The frequency with which the wind blows has already been mentioned, and when we add that on one day in three it attains a velocity sufficient to enable it to easily carry sand in suspension, its power as a transporting agent can readily be conceived. Not only does the wind carry the sand along from one place to another, dumping it behind or in front of every obstacle it may meet, but the combination of sand and wind forms a denuding force of no mean power, capable of planing and grooving the exposed surfaces of the hardest of rocks.

Now, although opinions may differ as to the part played in the past by wind and sand in the shaping and formation of the oases-depressions of the Libyan Desert, there can be no question of the effects they are producing at the present day. Wind-borne sand is indeed the curse of the oasis, and although its evil effects may be mitigated or altogether staved off for a time, the longer this force of Nature is opposed by man the greater and more overwhelming is its final victory. If a full account of the human occupation of the oases could be written, it would be very largely the history of an incessant combat between man and Nature; and although man may for a time gain the upper hand, and even make the sand-laden winds to some extent serve his purposes, he is in the end generally forced to abandon those places in which he has been at such pains to establish himself.

In the Libyan Desert, both on the plateaux and in the depressions, blown sand has a marked tendency to collect into dunes occupying definite north and south belts of country, lying parallel to the direction of the prevailing winds. This peculiar and fortunate disposition depends on a number of circumstances, such as the mean direction of the wind, the points of greatest supply of the material, and on other causes which are not perhaps as yet thoroughly understood.

In Kharga Oasis the best marked and most important belt lies somewhat to the west of the central axis of the depression. At the north end, in the neighbourhood of Um el Dabâdib, it consists of a number of isolated but parallel lines of dunes, which southwards pass over and round the hill-massif of Jebel Tarif, eventually uniting and forming a more compact belt of sand, with an average width of 8 or 10 kilometres, which continues right through the depression into the desert to the south. This line of sand sets a limit to the extension of cultivation to the west. A second belt comes from the plateau to the north of Qasr Lebekha, passes immediately to the east of Jebel Têr and the village of Kharga, and continues southwards until it spreads out and is arrested, more or less by artificial means, in the vicinity of Gennâh. Other smaller and less defined belts exist to the south of Ain el Tawîl, to the east of Headquarters, and near the foot of, and parallel to, the eastern wall of the depression.

Although it has been stated by more than one writer that the great sand accumulations of the Libyan Desert originate in the denudation of the Nubian Sandstone which occupies large areas to the south of the oases, I have never myself met with any evidence in support of such a view. In my opinion the bulk of the sand must be regarded as originating in the arenaceous deposits of post-Middle Eocene age, which largely occupy and are exposed on the surface of the country between the Mediterranean Sea and latitude 29° N. We know from personal observation that some of the great sand-belts, which cross the intervening limestone plateau to the southern oases, commence in this region, and the supply of sand made available by the denudation of the beds in question is inexhaustible. During the passage of this sand across the great desert tableland the individual grains of silica doubtless become much rounded and reduced by attrition, though the total loss is probably more than counterbalanced by the very considerable additions received in the form of calcareous grains, derived from the limestones forming the surface of the high desert.

An examination of the dunes of Kharga Oasis at once shows that the sand is not by any means composed solely of siliceous grains, but that there is a considerable proportion of white granules of limestone. A number of samples collected at random from the dunes in the central part of the depression were all found to contain a visible proportion of calcareous grains, and one of these, collected from the big dune to the south-east of Headquarters, was qualitatively examined for me by Mr. Garsed, and shown to contain 7·7 per cent. of calcium carbonate. It would be difficult to account for the presence of these calcareous grains on the assumption that the sand is derived from the Nubian Sandstone, though the denudation of the latter in and to the south of the oases must give rise to a very large amount of siliceous sand, which goes to swell the bulk of the dunes which have invaded this country from beyond the limestone plateau to the north.

The dominant form of dune in the oasis is of crescentic or horse-shoe shape, a form specially typical of desert regions where there are prevailing winds in any one direction. These ‘barchans,’ as they are called, which are always disposed with the concave, steeply-inclined sides facing southwards, are found of every size, and exhibit many variations of the simple crescentic pattern. In many parts of the oasis the sand-belts are made up of a number of isolated and promiscuously disposed barchans; in others the dunes have joined together into a compact mass, in which the typical shape of the individual barchan is more or less obliterated.

Solitary barchans, being well-defined isolated masses, lend themselves to observation better than the large and continuous belts of sand. They occur of all sizes, from little baby crescents, a metre or two across, to enormous masses 30 or 40 metres high and 200 to 300 metres in breadth. In all cases, except when their steady march southwards has been temporarily interrupted by southerly winds, the southern face, flanked by the horns of the crescent, is a straight slope of from 30 to 33 degrees, its inclination is, in fact, the angle of rest of loose dry sand, and it is formed of the sand which is continually blown up the opposite slope and dropped over the crest.

In a moderate breeze the whole barchan progresses steadily in a southerly direction without loss or gain of sand; in stronger winds, while still continuing its course, the dune may at the same time be either losing or gaining in actual bulk. The rate at which the barchans travel varies with their size. The larger the dune the greater the amount of material to be moved, so that, as a general rule, small barchans progress much more rapidly than large ones. The actual rate may vary from 10 to 20 metres per annum, the average being about 17. For instance, the big isolated dune on the road between Headquarters and Kharga village moved 11 metres southwards between December 8, 1907, and December 8, 1908, while during the same period a small dune in the Bellaida district travelled 21 metres in the same direction. The dimensions of these two dunes is as follows:

These are merely instances from dunes which I have had under observation for a number of months, full details of which I hope shortly to publish.

Approached on a bright sunny day from the south side, the angle of slope within the crescent of a barchan is most deceptive. Nine out of ten persons will confidently state that the face of the dune cannot be less than 60 or 70 degrees from the horizontal, though, as a matter of fact, it never exceeds by more than two or three degrees a third of a right angle. Unless held together by vegetation or compacted by moisture, it cannot exceed the angle of rest of dry blown sand, which is about 32 degrees. In normal weather this face of a barchan is a straight, unrippled, even slope of loose sand from top to bottom; when a light or gentle breeze is blowing from the north, the dune can be seen ‘smoking’ at the top of the crest, the sand being blown up the much more gentle and markedly rippled northerly slope, and dropped over the crest on to the steep, smooth, southerly face. The bulk of this sand in a light breeze falls on the upper part of the slope, equilibrium being adjusted from time to time by a downward sliding of the superficial layers. A cross-section of the dune, from north to south, would indeed show it to be composed of well-stratified layers of sand, dipping steadily southwards at a little over 30 degrees.

In this district I have never observed southerly winds hold for a sufficient length of time to do more than slightly modify the general form of a barchan, though during their continuance the progress of the dune is arrested, the outline of the crest becomes considerably altered, ripple-marks appear on the steep southerly face, and an apron of sand of greater or lesser dimensions forms at its foot.

The irresistibility of drift sand is well seen where isolated hills lie in the path of the dunes. When such hills are narrow, and elongated in a north and south direction, they generally act as a wedge, divide the wind, and force any sand it may be carrying to pass on either side. When, however, a hill has northerly flanks of any considerable width, it will only form a temporary check to the southward passage of the sand. The progress of the latter may be arrested for a while, until hollows have been filled in and the general slopes reduced; but eventually the sand will pass up along the lines of least resistance to the summit. This is beautifully illustrated at Jebel Tarif, the great isolated, flat-topped, hill-massif lying between Um el Dabâdib and Kharga village, standing over 300 metres, or 1,000 feet, above the surrounding plain. Instead of being diverted by this obstacle, the sand, coming from the plateau to the north and north-west of Um el Dabâdib, surmounts the slopes, and continues in its normal direction across the flat-topped summit. The latter has been cut up into numberless parallel north- and south-disposed ridges, separated by deep troughs, which are now to a considerable extent filled with sand. Active erosion must, therefore, at the present day be confined to the upper portions of the slopes of the valleys and to the intervening ridges.

Naturally in such a region the inhabitants have been quick to take advantage of any protection afforded by topographical features, and it is not surprising to find that the most important of the ancient monuments, as well as the greatest area of modernly cultivated land, lie in a comparatively sheltered position to the south of Jebel Têr. Even there, however, trouble is constantly experienced on the east side, owing to the tendency of the belt of sand-dunes, which comes from the vicinity of Qasr Lebekha, to spread laterally. Along the east side of the village the dunes are close up against the outlying houses, and the sand continually surmounts and pours over the walls which from time to time are erected by the natives to act as barricades.

Sheltered places of the above description are rare, the majority of the smaller settlements being situated on the open plain, where the only precaution which can be taken is to select the sites for wells as far away as possible from the well-defined sand-belts. But in windy weather the sand-blast is not confined to the neighbourhood of the dunes; the wind rages across the open plains, carrying dense clouds of sand in suspension, and devastating the works of man wherever the latter offer the slightest obstacle to its progress.