-5 ] SURFACE Anglo - Egyptian Sudan .

a Egyptian Sea range (6,000–8,000 ft.). From about the 12th parallel northwards, these hill-systems retreat further and further from the river, leaving a vast plain which increases in width from south to north, finally becoming continuous with the Sahara. Through this flow the Nile and its great tributaries, draining a total area of nearly three-quarters of a million square miles. a The country is best considered as falling into three divisions : the desert , the intermediate zone, and the tropical swamps and forests .

( 1) The desert extends south from the Egyptian frontier to about the 18th parallel eastward of the Nile and the 16th westward of it. It is really an eastward extension of the Sahara, but is divided by the shallow valley of the Nile into the Libyan Desert to the west and the Nubian Desert to the east. The Libyan Desert, still imperfectly known, is a sandy uninhabitable waste, waterless except for the Nile and a few oases.

The Nubian Desert is a more rugged and rocky dis trict with an average elevation of 1,500 to 3,000ft. above sea -level, stretching from the Nile to the Red Sea mountains and bounded to the south by the Atbara Port Sudan railway. East of the Halfa -Khartum railway, the desert is known as the Atbai. It is bounded to the east by the Red Sea range, a spur of the Abyssinian highlands averaging 6,000 to 7,000 ft . in height, which separates it from the coastal plain . From its centre a number of deeply -cut khors ( see p . 100 ) , often fertile and luxuriously wooded, and divided by ridges of rock and shale, run both to the Nile and to the Red Sea .

(2) South of the desert, a region consisting of Kordofan and Darfur on the west and the district between the Atbara -Port Sudan railway and the 12th parallel on the east forms a well -marked transitional Northern and central Kordofan consist chiefly of undulating and badly -watered plains, sandy and arid in the north , moister and more fertile in the south . Northern and north -eastern Darfur are similar in character to southern Kordofan . In central Darfur zone ,