Popular Science Monthly/Volume 16/February 1880/Artesian Wells and the Great Sahara
|ARTESIAN WELLS AND THE GREAT SAHARA|
By LIEUTENANT SEATON SCHROEDER, U. S. N.
OF late years public attention has been somewhat drawn to the great North African Desert. Mainly instrumental in directing thither even the eyes and ears of idle curiosity have been the two plans for flooding portions of that region. Of these plans, the French and the English, the former has assumed the more definite shape, though both are the subject of scientific and practical inquiry.
It may be questioned if there is not another means of improvement, more gradual, perhaps, but more sure and in many ways superior to the creation of an inland sea—superior in point of economy, and more widely diffused as well as more lasting benefits. Although our knowledge of the geological and historical part of the Sahara, and of its constitution, hydrography, and climate, is scarcely extended enough to prophesy confidently as to its future, yet it may be advanced that, if the desert is extending and the population decreasing, it is greatly due to the bigotry, hostility, and laziness of the Saharan tribes. The one requisite is water, whence the projects of supplying that need from the ocean. Perhaps it may be obtained otherwise, in comparatively homœopathic doses it is true, but fresh, and in such manner as to bring about grander results.
That water is not wanting in the Sahara is proved by the wells dotted along the routes of caravans. These are very shallow, and the water they afford is generally brackish and muddy, showing that they only reached parasitic sources and not the main subterranean sheets; but they are only the hurried work of passing caravans, whose sole thought was to supply the needs of the moment and reach the oases where very old wells have been found having a depth of over two hundred and fifty feet. It is a curious fact, too, well attested, that the number of wells has been greatly reduced by the Saharans filling up many of them as a means of defense against dreaded invasion.
These wells date back to the time of the first relations between the blacks of Soodan and the various peoples of white race driven into the desert by successive invaders. Diodorus, a priest of Tarsus in the fourth century, speaking of the great oasis in the desert forty leagues from the Egyptian frontier, mentions it being irrigated, not by rivers nor by rains, but by springs that issue from the ground not spontaneously, nor in consequence of the rains sinking into the ground, but by great labor on the part of the inhabitants. Several wells alluded to by him have been cleared since 1849 by a French chemist, M, Ayme, who established alum-factories in two Egyptian oases. These old wells were fitted with a stone pear-shaped valve by which the issue could be regulated.
About the middle of the sixth century, Olympiodorus of Alexandria speaks of wells five hundred cubits deep. Arabian writers in the middle ages describe them in detail; their great historian, Ibn Khaldoun, speaking of the spouting wells of the Sahara, considers them "a miraculous fact."
The origin of these subterranean waters is now well known. The streams flowing down the southern slopes of the Atlas Mountains of Morocco, Algeria, and Tunis, and on all sides of the Tibesti, Hogar, and other Saharan mountains, quickly disappear through the sands. M. Vivien de Saint-Martin, in "Le Nord de l'Afrique dans l'antiquité," says that, "under the sandy crust through which the waters necessarily sink, layers of clay have been found everywhere at various depths underground, where sheets of water make actual rivers."
The natural question then arises as to what causes these streams; how the parched desert furnishes rivers? Rains are quite abundant on the summits of the mountains—so much so that, in winter especially, the streams attain considerable proportions. The Sahara experiences at times tremendous storms and torrents of rain that in a few moments cause violent freshets. Dr. Barth, in his "Reisen in Nord und Central Afrika," cites among others a deluge that he witnessed at Tintagoda in latitude 19°. In less than an hour after a heavy rainfall on the mountain a sheet of water was rushing by with such force as to carry away herds of cattle and uproot trees; it covered to a considerable depth the whole valley, over a mile broad. In "Les Touaregs du Nord," M. Duveyrier says: "I had occasion on the 30th of January, 1861, while at Oursel, at the foot of the Tasli Mountains, to observe the overflowing of one of the numerous torrents that descend from that mountain. The rapidity of the stream was a metre a second, and the water brought down such alluvia that afterward the Touaregs could sow cereals where before there had been no arable ground." Further on the same traveler says: "In the spring of 1862 a storm of rain falling on the southern slopes of the Ahaggar brought such quantities of water into the valleys of Idjeloudjal and Tarhit that a portion of the mountain was carried away. The action of the water was so rapid as to sweep away and destroy an entire tribe encamped at the opening of the valleys." Also: "Up to 1856, on the left bank of the Ouadi Titersin, there had been aline of downs called Arekka-n-Bodelka so high that camels had been unable to cross them. A freshet in the Ouadi came with such force as to sweep away the entire mass composing the downs."
As M. Duveyrier says, the alluvial deposits from the Saharan torrents are often extremely fertile. At Biskra, at the time of the French occupation of that place (1844), a layer two yards in thickness of a rich loam was found on an ancient pillar of Roman construction.
The existence of subterranean sheets of water being well demonstrated, and a rude example being set by the untaught natives, it only remained to follow that example on the grander scale made possible by the advancement of science, and determine what benefits could be derived from these bidden treasures. Dr. Maurin enunciated, "Dig an artesian well in the region of sands, and the sands will become fixed by vegetation, and a forest of palms will soon stand where there had been a moving plain." And his saying is well borne out by numerous facts. In 1872 an old marabout (Mussulman devotee or saint) dug a well, planted palm-trees, and established himself at a place now called Tendouf; in less than a year it had become an important commercial center!
The first attempt at boring an artesian well on Algerian soil was in the plain of Oran, on the 7th of December, 1844. It was fruitless, although carried to a depth of 322 feet. A second attempt was made on the 14th of May, 1845, at Arzeu, and was likewise given up at 580 feet. Some time after the occupation of Biskra, a boring was made there to 270 feet: no result. It seemed a hopeless task to find living water, although it was well known that many years before the Arabs had had artesian wells.
General Desvaux, however, commanding the subdivision of Batna, kept studying assiduously to find means of fertilizing the barren regions around him. The perusal of several works by Toumel, by Berbrugger, by Prax, as well as a memoir of M. Dubocq published in 1853, convinced him that boring was destined to play an important part in the solution of the problem that so occupied him. In 1854 he chanced to be on the summit of a sand-hill near his camp, and overlooking the entire oasis of Sidi Rached. He saw that luxuriant vegetation, and turning away was confronted by the sterile waste on the other side. More than ever struck by the contrast, he sent for the sheik and questioned him, and learned that all the northern wells had become filled in with sand, that the parasite waters prevented digging any more, and that the entire population, broken-hearted, were looking forward to leaving their homes. As soon as possible he communicated with Marshal Randon, Governor-General of Algeria, and was authorized by him to commence a systematic search for water in the Sahara.
His project was then twofold: 1. To dig new wells in the Oued Rhir, give new life to the oases then beginning to yield to the invading sterility, and so win the gratitude of their population: 2. To revive the sandy steppes between that river and Biskra, open the desert to commerce as far as Ouargla or possibly Touat, so that French troops or isolated travelers could enter that region without the fear of dying of thirst.
He experienced some delay, of course, but finally in 1856 the material arrived at Tamerna, and on the 1st of May of that year the first blow was struck by Ali-Bey, the Caid of Tuggurt. The work was pushed rapidly forward, and on the 9th of June water issued in volumes. Lieutenant Rose, of the French army, describes the scene as being most affecting, comparing it to the miracle of Moses drawing water from the rock by the touch of his rod; the oldprostrates himself, mothers bathe their children in it, and it is blessed and named the Fountain of Peace. The issue of water was 69,725 gallons a day, temperature of 70° Fahr.
The news spread like wildfire, and the commandant of the province of Constantine was besieged with petitions from other oases to do as well by them. In eight years, 1856 to 1864, the French Government established in that vicinity (between the Ziban oases and the river Rhir) seventy-two artesian wells, of which twenty-four had been previously abandoned in course of execution by the natives. They cost altogether 290,000 francs ($55,970), had an aggregate depth of boring of 11,106 feet and a total first issue of 17,600 gallons per minute. The deepest was at Chegga, 364 feet; the least depth at which water was found was twenty feet. The ordinary depth was between 160 and 225 feet, and the average temperature 76° Fahr. The largest issue of any was 1,267 gallons a minute from that of Sidi Amran, 255 feet deep. In 1878 there were in Algeria 22,360 metres of wells, yielding 22,000 litres of water a second; their total cost was 2,350,000 francs.
The ground of the Sahara is so impregnated with various salts that the water of these wells, pure at first, becomes temporarily brackish. Analyses made by MM. Ville, Vatonne, and De Marigny show that each litre contained one to three grammes of sulphate of soda, one to two grammes sulphate of lime, besides chloride of soda, various salts of magnesium, and carbonate of lime.
A peculiarity of the wells is that tiny little fish, resembling small whitebait, are brought up in the water. They were first noticed by General Zickel in the water spouting from the well of Aïn-Tala, which is 145 feet deep. The length of these little creatures does not exceed one and a quarter inch. Their eyes are well shaped, although they emerge from regions so dark. They are malacopterygians, of the species Cyprinodon cyanocaster. Similar specimens have been found in some of the ancient wells of Egypt that were cleared by M. Ayme; as these, in all probability came from the Nile, and as the sand excavated from those wells is much the same as that of the Algerian borings, it is supposed that in both cases the fish infiltrate through with the water to the subterranean sheets.
It must not be supposed that, once the wells are dug, all labor is at an end. M. Charles Grad, who visited the region in January, 1872, found that several had ceased flowing, and that the greater part had a less issue. A few, on the other hand, he found yielded a greater volume than at first. He studied the matter, as did also M, Ludovic Ville, Directeur des Mines d'Algérie. The causes of the lessening of the flow were found to be the crushing-in of the tubes, the accumulation of sand in them, and the increase in the number of the wells, which caused too great a drain on the reservoirs. The life of the wells there without repairs seems to be twenty-five years; some have been known to last eighty without being cleaned.
The lesson to be drawn from this is expressed by the old saying, "Waste not, want not." Wherever it is possible to dam up the running streams of winter and make a reservoir for the summer, it should be done, and artesian borings made where such streams are not available. Among other places, M. Grad maintained that the fertile basin of the Hodna, situated on the Algerian plateau, would be the scene of that kind of work. These dams have already been extensively built in the province of Oran.
In the Sahara, however, the absence of superficial streams renders artesian borings of paramount importance. They will be limited there not only by the underground supply, but in some places by the hostility of the nomadic tribes who oppose their immediate construction. To what extent they can be relied on to reclaim desert-land is still an open question, but at the very least they can be permanently distributed along the routes of caravans that penetrate into the southern solitude, and with palm-trees planted about them form shady resting places. Up to 1872 one hundred and fifty thousand palms had been planted in the vicinity of the many wells dug in Algeria; in their shade, after the salty ground had been well washed by the flow of water, vegetables and grain were found to thrive. M. Ville, who has made such a special study of the water of the Sahara, announces that, as a rule, a well will water six times as many palms as it gives out litres per minute.
Not a few minds dwelt many years ago upon the possibility of establishing routes across the desert, but that was generally considered chimerical when account was taken of its dangers, known and unknown, the hostility of the races that inhabit it, the length of the marches under a burning sun, over a burning sand, relying upon occasional wells for water, and liable to utter destruction if caught in the path of one of those terrific storms. Still, having a colony on the north coast of the continent and another on the west coast, it is not to be wondered at that the French, with their indisputable energy, should have thought of uniting them overland. More especially does it seem natural in the early days of steam navigation. Nowadays, when cargoes can be sent from Oran to Saint-Louis (Senegal) in eight to ten days for eight dollars or less a ton, there is no great reason for sending caravans there, whose best time in a straight line would be three months and a half. Among the enthusiasts on that question may be mentioned General Faidherbe, some time Governor of Senegal, who displayed a wonderful amount of energy in the matter. Others were not wanting, including several explorers; the efforts of the latter, however, were rather more in the interests of science than material benefits.
It was about the year 1850 that the attention of the Algerian Government began to be drawn to the project of facilitating communication across the desert. In 1854 the Geographical Society of Paris offered a special reward for any one who should go from one colony to the other via Timbuctoo. In 1858 the Algerian Historical Society made a special order of the day a study on the best route and method of reaching Soodan. Finally, in 1873, a company was formed in Algiers, with a capital of thirty thousand francs, and the rather vague name of "Company for the Encouragement of Commercial Explorations in the Sahara." The intention of this company seemed to be to form at Laghouat an entrepot for merchandise suitable to the southern tribes, and to try to draw to Algeria a part of the traffic of Morocco and Tripoli. The Algerian Historical Society had recommended somewhat similar measures in 1860, but they were not carried out—the cause of the failure being attributed to the lack of French agents outside the Algerian frontier. That indefatigible explorer M. Duveyrier, in 1862, proposed a route following the subterranean course of the Igharghar River southward, different from the four routes generally taken by caravans; the Azdjer chiefs, to whose interest it is to encourage traffic across the desert, offered to guarantee the security of the expedition, and the Algerian Government promised to render it practicable by wells. In 1867 an expedition was actually organized, but was abandoned for reasons not generally known.
Since then the project seems to have been dropped, only to be revived again under a different form. The question of a trans-Saharan railroad has been started, which should not astonish us in America who now think nothing of going from New York to San Francisco in less than a week. M. Paul de Soleillet was among the first to propose the construction of a railroad from Algiers to Timbuctoo, and thence to Saint-Louis; in 1872 he attempted to perform that journey to explore the route, but he got no farther than the oasis of Insalah, about six hundred miles south of Algiers, being stopped by the natives. It would seem that a more practicable route would be found farther east, clear of the Tademayt and Ahaggad plateaux, of which the latter attains an elevation of over four thousand feet. The journeys of Barth and Vogel discovered that, at a short distance south of Tripoli, a series of terraces lead gradually to the vast plains of the desert, where there are only moderate undulations with occasional ravines and isolated masses of rock to Soodan. The southern part of the route was over plains slightly inclined southward. The greatest height observed in that region was six hundred metres.
M. Dupouchel, Ingénieur en chef des Fonts et Chaussées, went in 1877 to examine the ground west of the Ahaggad, and study the practicability of opening a railway between Algeria and the valley of the Niger of Soodan. The results of his examinations have appeared in book form, accompanied with maps and drawings. The route that he recommends commences at Algiers, and passes by Afreville, Boghari, Laghouat, and the oases of Touat, finally striking the Niger at Bamba, a short distance east of Timbuctoo. An eastern branch would descend that river to longitude 2° east, and would run from there toward the Tchad Lake. A western branch would ascend the Niger as far as Kouma, and then run to Saint-Louis. The total length of the line from Algiers to the Niger, deducting the part already constructed to Afreville, would be about 1,700 miles, of which the total cost is estimated at 400,000,000 francs (about $77,000,000). This is $15,000 less per mile than the average of all the railroads built in the United States during the year 1874, and $60,000 less per mile than the cost of the Central Pacific. President Grévy has recently been written to, and urged to appoint a commission to examine a proposal to construct that railroad.
It will readily be seen what an important element in the construction of a railway will be the power to supply water from underground as the work progresses. But there are enthusiasts who maintain that the object now to be accomplished is not simply the establishing of communication across the desert, nor the submerging of one very small portion for the benefit of another small portion, but no more nor less than the reclaiming—the fertilization—of the whole Sahara. This, indeed, sounds rash, and yet no less an authority than Gerhard Rohlfs, who has explored greater areas of Sahara than any other European, and whose journey from Tripoli to Rhadames and Fezzan won him a gold medal from the Royal Geographical Society of London, sustains the idea by saying that Nature would soon begin to assist man in the herculean undertaking. According to this traveler, three distinct zones separate the center of the desert from the neighboring lands of the Tchad Lake in the south; in the third or northernmost of these are immense forests of mimosas, where the ground is characterized by the absence of the smallest stone, and which, according to the aborigines, extend from Egypt to Timbuctoo, covering the Kordofan, the Darfoor, the Kamen, and the country of the Touaregs. Professor Rohlfs advances the theory that these forests are encroaching on the desert, and that in time the Sahara will disappear under a vegetation of which the mimosas are the forerunner. "Thus," he adds, "while certain timorous spirits fear that the earth may some day be overpeopled, Nature is silently transforming the soil where man will in the future be able to pitch his tent. The Sahara will be covered with green trees, new lakes will be formed, and the rivers whose dry beds now fill the traveler with horror will be running streams of limpid water as abundant as that of the great streams of Europe."
Such a return to what seems pretty certain to have been the state of things ages ago would be most extraordinary without the help of man. The vast tract comprised between the sixteenth and thirtieth parallels of latitude, and extending from the Atlantic to the valley of the Nile, once fertile, became the arid waste of to-day mainly through neglect. A M. Largeau in 1874 visited the valley of the Igharghar, with the intention of branching off to Rhadames to study the commerce of that oasis and test the practicability of diverting to Algeria the caravans that come there by the central route from Soodan. He questioned the chambas on the causes of the drying of the great Saharan streams, and found that all agreed in saying that these dead rivers once ran full through a country more fertile than the Tell (the region north of the Atlas Mountain's crest), but could only explain it by legends more interesting than satisfactory.
M. Largeau gives the following explanation of the change: "It is known that pastoral people have always been great destroyers of forests, for they need large spaces of clear ground to feed the flocks that form their wealth and to promote security against the wild beasts that lurk in forests. Even now the Algerian Arabs are seen firing the woods to enlarge the narrow limits imposed upon them by colonization. So, although the great Saharan streams have not been explored to their sources, yet it is known that they commence on the bare plateaux that are but the skeletons of heights once wooded and fertile. All accounts of the inhabitants of these regions agree on that point. Consequent upon the destruction of the forests the periodical rains were replaced by rare and short though violent storms, the waters from which, instead of soaking in as in past ages, slip by on the rocky masses, carrying away the rich surface mold, and bring about the drying of the springs, and, as a direct consequence, of the rivers."
An admission of this theory leads the way easily and hopefully to the prophecy of Professor Rohlfs, and raises the question whether it would not be better on all accounts to let the salt waters of the Mediterranean circulate in their own proper bed and pursue the more economical work of conquering the desert by assistance from underground. Nearly all the fluvial network of the Algerian Sahara converges toward the Igharghar. Formed by the confluence of several small streams on the slopes of the Ahaggar, it flows northward, and soon sinks through the light sands and pursues its underground course to the western part of the basin that the French contemplate inundating, bearing in that part of its course the name of Oued Rihr, or river Rihr. Into this same depression flows another subterranean stream, the Oued Djeddi, which has its sources on the plateaux of Laghouat in the west. The two streams in all probability united in past ages, and possibly even connected with the Mediterranean. However that may be, there seems little doubt that water in considerable quantities may be found by boring in the dry beds of these two streams. M. Largeau saw several wells in that of the Igharghar, only twenty-five feet deep, giving very sweet water, of a temperature of 70° Fahr.
With this in consideration, and the example of the marabout of Tendouf still in mind, it would seem possible not only to fertilize large areas of Algerian soil, but to bore our way as it were up the slopes of the Ahaggar and gradually restore the rain-causing forests of M. Largeau, which in their turn might attack the desert from the center, as Professor Rohlf's mimosas do from the south.
The lowest estimate of the cost of inundating the depressions in the Algerian Sahara being $5,790,000, we see that that sum otherwise appropriated would pay for boring 7,400 wells averaging 154 feet in depth, assuming the cost per foot to be the same as south of the Ziban oases. Allowing the issue to be only one half that of the wells near Biskra, the total flow would be 1,100,000 gallons per minute, which, according to M. Ville, would suffice for the irrigation of about 24,600,000 palms. One tenth of this labor and expense would produce great results.
So far facts and discussion alike have been limited to the region bordering upon Algeria and Tunis, This is because explorations have naturally been carried on there somewhat to the exclusion of the Tripolitan neighborhood, and not because similar causes and effects may not be found farther east. There is every reason to believe that the desolate region bordering the south shore of the Mediterranean between the tenth and twenty-fifth meridians is destined to experience an equal improvement with the western Sahara. The writer of this article, who was one of a party of officers of the United States Navy engaged in surveying along that coast in 1878, had occasion to observe in several places, notably at Zouaga near Tripoli, and along the shores of the Gulf of Sidra (Syrtis Major), hottest of the hot and driest of the dry, that water was to be had by digging but a short distance. He noticed, also, not a few oases just on the sandy horizon, that bespoke the presence of the life-giving element. An examination of the map shows many more. While this would not be very convincing proof to a skeptical mind, in the absence of organized investigation, it may at least be considered encouraging. The day is not far distant, however, when certain knowledge will confirm or disprove hazardous opinions. The various geographical societies of the world have ceased to let the matter rest, and Professor Rohlfs is even now in charge of an expedition sent out by the German African Society. Last January he was two hundred and fifty miles south of Tripoli, at the foot of the Black Mountains; recent advices show him to be at Benghazi, on the eastern shore of the Gulf of Sidra. Accounts of the expedition have not yet come to hand.
In the event of an increase in the commercial importance of Northern Africa, whether by inland seas, artesian wells, or railroads, or all three, means of transportation to and along the seaboard and thence to foreign ports will not be lacking. As early as 1857 a railway system was decided upon for Algeria, which included a shore-line, with branches inland to various points. The construction of this network is practically completed. On the 1st of January, 1879, there were three hundred and thirty miles of railroad in that colony. A line has also been started to connect Constantine with the city of Tunis, the bondholders being guaranteed six per cent, interest by the French Government. This will probably be completed in a year. In Morocco the development of roads is not great: we can not expect very much anyhow from that, as present laws forbid the exportation of cereals, for fear of a recurrence of the famine. In the province of Tripoli but little is needed now; when the time comes it will be easy work to build a railroad in so flat a country.
In the matter of ports, Algeria points with pardonable pride to Algiers, Oran, Arzeu, Philippeville, Bona, and several minor harbors that have been made secure by artificial works. The first mentioned was begun in 1530 by Bab Aroudj (Anglicè Barbarossa) and his Christian slaves, and finished by Christians guiding the labor of that pirate's descendants. Tunis boasts of a magnificent lake at Bizerta, close to the sea; a little dredging in the short, narrow channel leading out would transform it into an unparalleled harbor for ironclads, of which both Germany and Italy are said to be particularly well aware. In Tunis Bay a single inexpensive breakwater, built in only six fathoms depth, would afford perfect shelter. Farther south and east, Sphax roadstead only wants ships to fill it, and Surkennis only the Bey's order to welcome foreign vessels to which it is now closed. In the province of Tripoli may be mentioned Tripoli Port, Menelaus Bay in the Gulf of Bombah, Marsa Euharit, Marsa Tebruk, all good natural harbors, or needing but insignificant works to render them secure. In Egypt it is unnecessary to mention the splendid port of Alexandria.
The French are the pioneers in the northern part of the African Continent, and it would seem desirable for them to extend their sway to the eastward of Cape Roux. That, however, would cause diplomatic complications: England, Germany, and Italy would surely protest against any projects of annexation. But there is still scope for them in the desert. The nomadic tribes will hardly stop the southward course of empire when French industry and capital fan the breeze of progress.