Popular Science Monthly/Volume 8/April 1876/The Proposed Inland Sea in Algeria
AMONG the most revolutionary of the geographical schemes of the day are the projects of flooding portions of the African Sahara, and thus restoring to the sea what was once an integral part of it. In the Pliocene period, according to Sir Charles Lyell, the great desert was under water between latitudes 20° and 30° N., so that the southeastern part of the Mediterranean communicated with that portion of the Atlantic now bounded by the west coast of Africa. This is indicated not only by the presence of marine shells and other remains throughout the Sahara, but also by the radical difference between the fauna and flora north and south of it. What was formerly separated by a barrier of water is now separated by a barrier of sand.
There are two principal depressions in the Sahara, the basin called El-Juf, in the Sahel, north of the Middle Niger, which covers an area of about 126,000 square miles, and that of the shotts in the Algerian Sahara.
Mr. Donald Mackenzie, a British engineer, who has investigated the former depression, affirms that a long valley extends from its northwest corner to the Atlantic coast opposite the Canary Islands. It is only necessary, he argues, to cut through the accumulated sands at its mouth, which is laid down on the maps as the river Belta, to let in the waters and flood the entire basin. This scheme, advocated by Mr, J. A. Skertchly, General Sir Arthur Cotton, and others, will probably result in a thorough exploration of that part of the Sahara and its alleged outlet. The other project is in a more advanced state.
The depression of the shotts lies at the foot of the Aures Mountains, spurs of the main chain of the Atlas, partly in the province of Constantine in Algeria, and partly in Tunis. Its western extremity is in latitude 34° 30' N, longitude 5° 65' E., and it extends thence eastward two hundred and thirty-five miles to within about thirteen miles of the foot of the Gulf of Cabes, or Gabes, in the Mediterranean, anciently the Lesser Syrtis, from which it is now separated by an isthmus of sand. The breadth of the depression is about thirty-seven miles. Within these limits lie several connected lake-beds, called by the Arabs shotts or sebkas, shott signifying properly the bottom of a lake left dry by evaporation, and sebka a saline marsh. The largest of these are Shotts Melrir, or Melgig, whose eastern extremity is called Es-Selam, El-Rharsa, or Gharsa, and El-Jerid, or Fejej. About one-half is in French territory, the Tunisian boundary line cutting the western bank of Shott El-Rharsa.
This great depression is supposed to mark the site of the lake of Triton, or Tritonis, mentioned by Herodotus, Scylax, Pomponius Mela, Ptolemy, and other ancient writers, and around which were localized the Greek divinities Poseidon and Athena, and the Argonautic myth. Into it was driven the good ship Argo, when blown from her course around the Malean promontory by an adverse wind. Jason, lost among the shallows, propitiated the local divinity, Triton, son of Poseidon, by presenting him with the brazen tripod, whereupon the god, filled with prophetic heat, foretold that a hundred Grecian cities would spring up around Tritonis whenever a descendant of the Argo's crew should seize and bear away the precious gift. Through the foresight of the subtle Libyans, who hid the tripod, the prophesy was unfulfilled, but many noble cities were afterward built north and east of Tritonis, and along the coast of Syrtis Minor. Indeed, so numerous were they, and so flourishing as trade-centres, that the country was named Emporia. All the ancient writers agree in praising it for its wonderful riches and fertility. Says Scylax: "This region, which is occupied by Libyans, is most magnificent and fertile; it abounds in fine cattle, and its inhabitants are most beautiful and wealthy." It was within the dominion of Carthage, and here were the storehouses and granaries from which Rome's great rival supplied her troops.
But now all is changed. The drying up of the ancient sea has deprived the land of its moisture, and the once fertile plain between the mountains and the north bank of the shotts is, with the exception of a few oases, a sterile waste. Nothing remains to tell of former greatness but ruins, which are said to be scattered over the country far up into the mountains.
Herodotus, the most ancient writer by whom Tritonis is mentioned, says that it was fed by the great river Triton; but modern research has failed to identify it, there being now but a few rivulets which enter it from the mountains on the north, or lose themselves in the desert. If there ever was a great river flowing into it, its bed has been obliterated by the shifting sands.
At a later date Tritonis appears as three connected lakes, called, respectively, Libyca, Pallas, and Tritonis, which some recognize in the Shotts Melrir, El-Rharsa, and El-Jerid, It is probable that the mouth became gradually blocked up with sand, and the lake, no longer receiving sufficient water from the Mediterranean to supply the waste from evaporation, separated into several smaller seas, which, by continued desiccation, became transformed at last into their present condition. When this took place can only be conjectured, but it was probably in the early centuries of the Christian era. The Arabs preserve the tradition that Shott Es-Selam was a lake at the time of the Mussulman conquest. They also aver that the lake bed has not been covered with water during the past hundred years.
Although it has long been known that this desert basin was lower than the Mediterranean, nothing was positively settled in regard to it until 1873, when Captain Roudaire, a staff officer of the French army in Algeria, ascertained the altitude of Biskra, and by a series of levelings from that point proved that the western extremity of Shott Melrir was twenty-seven metres, or nearly eighty-nine feet, below the level of the sea. The publication of his investigations and an exhaustive discussion of the probabilities of success in reopening the ancient lake, in the Revue des Deux Mondes (May, 1874), aroused interest in the project in hope not only of reclaiming the country, but also of opening a commercial avenue to Southern Algeria. The French have long sought to deflect the caravan trade of Middle Africa, which is now mostly monopolized by Morocco and Tripoli, to Algiers, but in vain, the increase in prices to be obtained in Algiers not being sufficient to compensate for the increase in distance. But with an inland sea the circumstances would be changed. The country around it would resume its ancient character of a littoral province, and the caravan routes of the Sahara would converge toward a port established on its southern border, whence the gold dust, ivory, gums, and ostrich feathers of Soodan would be shipped directly to Europe to the detriment of the Mohammedan markets. Tougourt, too, the French military post in southern Algeria, now distant nearly two hundred and fifty miles from the port where its provisions are landed, would then be only about forty miles from the sea.
Captain Roudaire discusses also the probable climatic changes which would ensue from reopening the Bay of Triton. He argues that the northwest winds, which prevail in summer, would be less violent than now, and the southwest winds, which blow during the remainder of the season, would be charged with vapor and cause a greater fall of rain in Algeria, Sicily, and South Italy, without materially modifying the climate. This increased rainfall would restore the land to its ancient fertility, and the region of the shotts would again become the home of a thriving population and the granary of North Africa.
To flood the shotts would require only the piercing of the isthmus between El-Jerid and the Gulf of Cabes. This is about thirteen miles wide; but Captain Roudaire thinks that the curve of altitude would reach zero at about eleven miles from the Mediterranean, which would materially reduce the amount of excavation. As the evaporation would be much greater than in the Mediterranean, a large and constant flow of water from the latter would be necessary to keep it at its proper level. This would require a canal at least one hundred yards wide, which could be constructed, it is calculated, at a cost of twenty million francs. To this amount would have to be added a sufficient sum to compensate for the destruction of property in the Tunisian part of the depression, which would ensue from its submersion. Besides the towns of Nefta and Tozer, there are many douars, or villages, in the oases, surrounded by cultivated lands and date plantations. These are generally in the lowest part of the depression, for there only can potable water be found, the higher land being without springs.
The superior council of Algeria, comprehending the immense advantages which would accrue to the colony from the consummation of this scheme, voted in 1873 a sum sufficient to continue the survey, and a well-appointed expedition, under command of Captain Roudaire, made a thorough examination of the bed of the Algerian portion of the shotts in the following year. The French Geographical Society, taking a national as well as a scientific interest in the question, also contributed money in furtherance of the object, and deputed M. Duverrier, one of its members, to accompany the party. The expedition entered the depression on the northwest side of Shott Melrir. The soil there is sand and marl, charged with salt. The many streams which traverse the country have, with a few exceptions, no running water, excepting in winter and spring, the season of rains and of the melting of snow in the mountains. These rivers usually divide, before reaching the shotts, into several branches, which again subdivide and form innumerable ramifications. Where these begin to disappear, the soil, which is charged with salt and almost bare, swells and cracks, and the water sinks, when the crust reforms. Farther east are naked plains of marl, level and smooth, and covered with a white incrustation which produces frequent mirages. On the extreme west the river beds enter Shott Melrir with separating. On the south side are sand hills and moving sands.
All the shotts are alike in general features. All have flat bottoms with an inclination too slight to be perceptible to the eye, and all form basins which receive water-courses. The soil of all contains a great quantity of salt, which whitens their bed in dry places. But each has its peculiarities. The west end of Melrir has a bottom of sandy earth, strewed along the borders with small round and polished quartz pebbles. Near the banks is a meagre salsuginous vegetation. In the interior its bed is clay, filled with crevices, but moist; farther on the crevices close and the saturated marl and clay form quagmires in which horse and rider might be swallowed up.
The eastern end of Shott Melrir, which is called Shott Es-Selam, presents other general characteristics. Near the banks the bed is sandy, but toward the middle it forms a hard crust of salt and sand. Elsewhere the soil is a hard surface of clay, which shines in the sun. Mirage is very frequent in this shott.
Between the Shotts Es-Selam and El-Rharsa the expedition first began to encounter obstacles which may seriously interfere with the projected inland sea. In the intervening country are numerous smaller shotts, of which that called Mouia-el-Tadjer is the largest. This shott has a long extension stretching southward, called El-Hadjila, connected with which on the east is Shott Mouia-el-Tofla. Measurements in the highest part of the bed of the latter showed it to be more than eleven feet above the level of the sea. A low ridge separates it from Shott El-Asloudg, the western border of which is only between six and seven feet below the sea, and the eastern about twelve feet. Between this and Shott Bou Dhouil, which is little more than eight feet above the sea, is an extended ridge of sand. Bou Dhouil is but a short distance from the Tunisian frontier and the great Shott El-Rharsa. At this point the expedition ceased its labors and returned to Biskra, convinced that a secondary canal connecting El-Rharsa and Melrir, or some of the shotts belonging to its system, would be necessary before the proposed inland sea could be extended far enough west to benefit Algeria. This would entail a considerable additional expense, but whether large enough to seriously affect the realization of the scheme cannot be known until the publication of the official reports.
This expedition made no investigation of the Tunisian portion of the depression, being evidently under the impression that no insurmountable obstacle existed in that part. Whether this belief was founded on the accounts of the ancient geographers or on an actual knowledge of the country is not apparent, but it is said that levels were taken from Shott El-Jerid to the Mediterranean several years ago by Captain Pricot de Sainte Marie, of the staff of the French army in Algeria. His report, which is deposited in the archives of the Ministry of War in Paris, must have been favorable, else the survey of the Algerian shotts would scarcely have been undertaken.
It is reported, however, on the contrary, that a survey was made of the same isthmus in 1874 by M. Fuchs, a French geologist employed by the government of Tunis to investigate the mineral resources of the country, who discovered that physical obstacles exist of a nature to render a canal impossible; that a range of sandstone hills lies between El-Jerid and the sea, and that the bed of El-Jerid itself is considerably above the sea. If this be true, not only is the proposed inland sea an impossibility, but we must also relegate to the domain of fable the accounts of the great lake of Tritonis, or assign it to another locality.