Page:Africa by Élisée Reclus, Volume 1.djvu/99

 accumulated alluvia are soon swept away and distributed along the coast by the marine currents. In many places these encroachments of the sea have been clearly determined. A distinctly perceptible coast stream sets steadily from Alexandria eastwards to Port Said, here and there developing slight local counter currents, such as the ebb and flow between the Rosetta mouth and Abukir Point. The effect of this stream is to erode the headlands and fill in the intervening inlets, thus restoring the original parabolic curve of the coast. Wherever an obstacle is met, it becomes attached to the mainland by a semicircular strip of sand. Shoals have thus been accumulated at the western pier of Port Said, although not in sufficient quantity to endanger the basins of the new port, especially as they may be easily reduced or removed by dredging. Altogether the annual growth of the delta cannot be estimated at more than 8 or 9 feet, so that since the time of Herodotus the mainland has encroached on the sea probably not much more than 3½ miles.

There may even be a complete equilibrium between the fluvial deposits and the erosions of the marine currents. At least the geological aspect of the coast is that of an ancient seaboard forming a continuation of the small limestone ridge at Alexandria, which at present terminates at Abukir Point. In the shallow waters the waves take advantage of every rocky projection, islet, or headland to deposit sandbanks, and thus gradually transform the irregular marine inlets into landlocked lagoons. Before advancing beyond the mainland the Nile had to fill up these lagoons, separated by strips of sand from the Mediterranean, and this work is not yet accomplished. It would appear to have even been delayed by a general subsidence of the land, such as has been recorded in Holland, on the coast of North Germany, at the mouth of the Po, in the Amazon estuary, and in so many other alluvial districts. Thus the artificial caves formerly excavated near Alexandria at a certain elevation above sea-level are now submerged. These are the tombs known by the name of "Cleopatra's Baths." To the same phenomenon should perhaps be attributed the restoratioa of certain depressions, which after having long remained dry have again been partly flooded.

But however this be, the lacustrine basins of the delta are now so shallow that they might easily be filled up. The eastern extremity of Lake Menzaleh, which is separated from the Nile basin by the embankments of the Suez Canal, has already become dry land, while the old bed of the Pelusium branch has disappeared. Since Andreossy's survey at the end of the last century, Menzaloh itself has been much reduced, and has now a mean depth of scarcely 40 inches, although covering a superficial area of about 500 square miles during the floods, when it communicates by temporary channels both with the Nile and the sea. At low water it is so beset with shoals and islets that most of the navigation is suspended.

Lake Burios, which lies east of the Rosetta branch in the northern part of the delta, is scarcely less extensive than Menzaleh, and like it rises and falls with the periodical floods. A sweet-water basin when fed by the Nile, it becomes brackish at other times, and communicates through a single permanent opening with the