Abstract
THIS interesting phenomenon, which so largely con tributes to produce changes in the bed of the Nile and to accumulate river formations of great geological importance, has been recently investigated by M. Ernest Marno, who has just published an elaborate paper on the subject, in the last number of Petermann's Mittheilungen. It is accompanied by a map, on the scale of 1 to 500,000, of the Bahr-el-Gebel and of the Bahr-el-Abiad, from Geseir Abbas to Sohat, and of the Bahr-el-Serat from its mouth to 7° 30′ N. lat. After having made its way among the hilly region, through several great lakes, formerly forming a series of terraces and connected to gether by short rivers, the Nile, or the Bahr-el-Gebel—the River of the Mountains—enters an extensive flat land, which it crosses over six degrees of latitude to the next rocky barrier, which it cuts through at Khartum. Over this stretch it runs with numerous windings, first north to its confluence with the Bahr-el-Ghazal, and then to the east, under the name of Bahr-el-Abiad, and, although the direct distance between its issue from the hilly tract to Khartum is only 600 miles, the total length of the river with its windings is no less than 100 miles. The whole of this region is a wide marsh, and the river has no proper banks, its water being mixed with that of marshes which cover the whole of this tract. It is even a rare occurrence to see dry banks, as the country is more like an extensive marsh, through the midst of which a somewhat deeper channel has been dug by the current of the river. Numerous smaller rivers connected together and with the main channel and its numerous rami fications circulate amidst these marshes, and during the rainy season the maije, or lateral ponds and lakes, increase yet more, covering wide tracts of land, whilst during the dry season some stretches of banks re-appear, and the lakes which were navigated by steamers some months before become simple marshes. Vegetation plays an important part in the modifications which are going on in this region. The country is covered with rich grasses, mostly consisting of such species (Saccharum spontaneum, S. irschmum, Vossia) as grow perfectly well even in water; this grass can be lifted with its roots by water, and grow floating on the surface, so as to render it most difficult to draw a line of demarcation between land and water. Thick and high papyrus palms grow sometimes on the very banks of the main channels of circulation of the water, and strengthen these by their complicated roots, but they do not cover all the banks, and the outlines of the river are mostly indefinite. Some few tree-like Herminiera elaphrosylon grow as isolated individuals on the banks of the rivers, and of the maije, whilst the smaller marshy and aquatic flora (Pistiæ, Nympheæ, Vallisneriæ) nearly disappears in comparison with the rich vegetation of the above-named species. The fauna of this region closely depends upon the season. Mammals and birds leave it during the rainy period and wander to the hilly tracts, but during the dry season the banks of the maije and of the rivers are peopled with elephants, buffaloes, giraffes, antelopes, and by many kinds of birds. Besides this region has also its special forms, namely the Balæniceps Rex, the Protopterus æthiopicus, and the ganoid fish, Polypterus, all being remains from earlier geological periods. The people who inhabit this region, the Dinka, the Shilluk, and the Nuehr, all belong to a very low level of civilisation, living mostly on their herds of cattle; they change their abodes in accordance with the season, but they cannot be considered as true nomades, as the land occupied by each tribe is strictly limited by other tribes, and every encroachment on another's land is punished by war.
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The Grass Barriers of the Nile . Nature 25, 130–131 (1881). https://doi.org/10.1038/025130a0
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DOI: https://doi.org/10.1038/025130a0