Under the name Blue Nile the united streams flow on in a single current in a northwesterly direction. During its course the stream receives two large rivers which run nearly parallel to each other.
We have seen that, at the town of Khartoom, the Blue and the White Nile unite to form a single stream. As this stream leaves Khartoom its course is a northerly one for about sixty miles until, passing the ruins of the ancient Meroë, it forms its first cataract. Here, turning to the northeast, it is joined by its last tributary, which bears a name signifying "Black River." It is doubtless so named from the quantities of black, slimy mud which it carries down in its course, eventually to fertilize Egypt.
The Nile, from the point where the last tributary joins it, flows through the thickly populated and fertile district of Berber, with its many villages.
When the stream leaves Berber it enters the desert. As it makes a turn to the west it forms the large island of Mograt. Turning sharply in a southwesterly direction, it describes what is known as "The Great Bend," in which there are two cataracts.
Entering Nubia the stream turns again to the northwest. Here, on either bank, is a narrow strip of fertile land, under cultivation.
Again a cataract is formed, when the stream bends around to the northeast to form later a fifth cataract.
As the river continues on its course, it gradually grows more and more narrow, till, later, at Assouan, it forms its last cataract, as it descends.
From Assouan to the Mediterranean Sea the Nile has an average fall of two inches to a mile. Its velocity is about three miles an hour as it flows on, watering and fertilizing the land of Egypt throughout its entire length.
The delta, or mouth, of the Nile has an expanse of about one hundred and fifty miles on the Mediterranean.
At the delta the Nile spreads out into numerous streams to enter the sea.