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to the mouth of the Sobat river. Of this length, the first 200 kilometres 
up to Dufile have scarcely any slope, the next 150 kilometres are down 
a series of severe cataracts. From the foot of these cataracts to its tail 
the Albert Nile has a gentle slope and traverses the Sudd region where 
the bed of the stream is often barred by blocks of living vegetation. 
In this latter region the stream divides into two, of which the right 
hand one is known as the Bahr Zeraf. After a course of 270 kilometres 
the Bahr Zeraf joins the Albert Nile again. In the interval the Albert 
Nile receives as a left-hand feeder the Bahr Gazelle. The Sobat river 
has its sources in Gallaland and joins the Albert Nile at the termi- 
nation of the Sudd region. From the junction of the Albert Nile and 
the Sobat, the river is known as the White Nile, which, after a course 
of 840 kilometres, with an exceedingly gentle slope, joins the Blue Nile 
at Khartoum. 
The Blue Nile is the true parent of the land of Egypt. The 
deposits of its muddy waters have made Egypt. The Atbara has added 
its quota, but the Blue Nile is incomparably the chief contributor ; fed 
by the timely and plentiful rains of southern and south-eastern Abyssinia, 
it contributes 65 per cent of the waters which pass Assuan. The 
furthest sources are those of the Abai, which, after a course of 110 kilo- 
metres falls into Lake Tsana. This lake has an area of 3,000 square 
kilometres and lies about 1,760 metres above sea level. The Blue Nile 
leaves it at its south-eastern corner and hurries down to the Sudan, fed 
by numerous Abyssinian rivers. At Rosaires, after a course of 7 50 kilo- 
metres, it has fallen 1,260 metres; and below the Rosaires cataract enters 
the plain country south of Khartoum. For its remaining 615 kilometres 
on to Khartoum, where it meets the White Nile, it is navigable for the 
greater part of the year. North of Sennaar it is fed by the Dinder and 
Rahad rivers. 
Between Khartoum and El Darner, on a length of 320 kilometres, 
the Nile has its even passage broken by the 6th cataract at Shabluka. 
At El Darner the Nile receives the Atbara as a right hand tributary. 
The Atbara is a very muddy torrent fed by the rains of north-eastern 
Abyssinia. It runs for 4 months per annum and is dry for 8 months. 
Rising within a few kilometres of Lake Tsana, it falls 1500 metres 
in its first 300 kilometres, and is then joined by the Salaama, and, 
100 kilometres lower down, by the Settit river. After the junction 
with the Settit, the Atbara flows for 480 kilometres and joins the Nile 
at El Darner, contributing a fair quantity of water and a very con- 
siderable quantity of Nile mud to the river. 
