330 NOETH-EAST AFEICA. 



Bahr-Yusef lias been gradually deflected eastwards by the ranges of dunes skirting 

 the left bank. But the progress of the sands is extremely slow, and may perhaps 

 be compensated by the erosions caused by the action of the current along the 

 right bank of the Nile. Moreover the sands themselves may be cultivated like 

 other lands, wherever they can be brought within the reach of the irrigating waters, 

 brinffins: down the rich alluvia of the stream. 



West of the oases, the Libyan desert has not yet been traversed by any explorers 

 in the direction of the Kuf ra oasis and of Fezzan. An inhospitable region at least 

 400,000 square miles in extent, inaccessible even to travellers provided with all the 

 resources of modern industry, occupies this part of the continent, completely separa- 

 ting Egypt and Cyrenaica from the lands comprised within the Tsad basin. The 

 natives of the Egyptian oases are unable to give strangers any information regard- 

 ing these mysterious and terrible regions bounding their horizon, and into which 

 they are careful not to penetrate. A few confused legends destitute of all historic 

 value are, however, kept alive amongst them regarding strange events supposed to 

 have occurred in these frightful solitudes. 



In the year 1874, Bohlfs, Zittel, and some other German explorers, vainly 

 attempted to make their way in a straight line across this region to Fezzan. In 

 anticipation of a long journey they organised a whole caravan of camels, carrying 

 water in iron chests lined inside with tin. But after a six days' march from Dakhel, 

 they became convinced that it would be impossible for the camels to traverse the 

 endless ranges of dunes barring the route in the direction of Fezzan. Hence they 

 turned northwards to seek a refuge in the Siwah oasis. This point was reached 

 twenty-two days after leaving the last watering-place, and throughout the whole of 

 this expedition nothing was met except sand and rocks, and the " devil's water " 

 shown by the mirage. 



The part of the Libyan desert lying nearest to the Egyptian oases resembles 

 that skirting the Nile Valley. Here the surface is still varied by a few limestone 

 hills, interspersed with ranges of dunes and stunted scrub. But when the 

 traveller reaches the region of quartzose sandstones all vestiges of vegetation 

 disappear. Nothing now meets the eye except sand and stratified rocks, alternating 

 with deposits of a very rich iron ore. The land rises gradually in the direction 

 of the west, and towards the parting-line between the limestones and sandstones 

 the plateau attains an elevation of 1,460 feet. Here begins the ocean of sand, 

 which stretches for unknown distances in the direction of Fezzan. In the north 

 it extends for no less than 240 miles towards the Siwah oasis. 



The vast dunes of this region, produced by the weathering of the sandstone 

 rocks, have a mean altitude of over 300 feet, hence exceed in elevation the largest 

 sand-hills of Europe. Some are even said to attain a height of 500 feet. Disposed 

 in the direction from south to north, or from south-south-east to north-north-west, 

 perpendicularly to the polar winds, the ranges follow each other like the ocean 

 waves under the regular action of the trade- winds. Secondary systems of dunes, 

 which may be compared with the false cones occurring on the flanks of Etna, are 

 developed by the irregular atmospheric currents, and these are usually disposed 



