Though the longest river in Africa, the Nile has little historic
interest above Khartum, where the White Nile and Blue Nile unite their
waters. Below Khartum navigation is rendered extremely dangerous by the
cataracts which obstruct the bed of the river, the sixth occurring not
far north of Khartum, the first near Assuan, in Egypt. The Nile enters
the Mediterranean by a delta which separates into two main channels,
the Rosetta and the Damietta, which are intersected with canals. The
valley of Upper Egypt is narrow, and the fringe of mountains on either
side are of no great height, so that the landscape varies but little and
might appear to be monotonous but for the rich and wondrous coloring of
all the scenery, the vivid green of the fields, the rich red-brown of
the river, the bright yellow of the rocks, with overhead a deep blue sky
and brilliant sunshine. The river flows into Egypt proper north of the
second cataract, a little south of Wadi-Halfa. The Blue Nile joins the
river at Khartum; this stream brings down an immense quantity of red
mud. The cataracts are six in number.