of any practical
utility, and was merely an impediment to navigation. Between the
years 1885--90, however, during the British occupation, Sir Colon
Scott-Moncrieff successfully completed the barrage at a cost of
$2,500,000, and now the desired depth of eight feet of water on the
lower part of the Nile can always be maintained.

[Illustration: 241.jpg THE NILE BARRAGE]

It proved to be of the greatest advantage in saving labour worth
hundreds of thousands of dollars a year, and in the irrigation and
navigation facilities that had been contemplated as among the benefits
which would naturally accrue from its successful completion.

Compared with the advance of the land seaward at the estuary of the
Mississippi and the Ganges, the advance of the Nile seaward is very
slow. This is accounted for by the geological theory that the Delta
of the Nile is gradually sinking. If this is so, the tendency of the
periodical deposit to raise the level of the Delta will be counteracted
by the annual subsidence. These phenomena account for the gradual burial
of Egyptian monuments under the sand, although the actual level of the
sea above what it formerly was is quite unappreciable.

The periodical rise in the Nile, recurring as regularly as the
revolutions of the heavenly bodies, necessarily remained an unsolved
mystery to the ancients, for until the discovery of the tropical
regions, with their mountainous lakes and deluging rains, it was
impossible to learn the occasion of this increase. It is now known that
the Blue Nile, flowing out of the mountainous parts of Abyssinia, is the
sole cause of the periodic overflow of the Nile. Without the tropical
rains of the Ethiopian tablelands, there would be no great rise nor any
fertilising deposits. Without the White Nile, which runs steadily from
the perennial reservoirs of the great Central African lakes, the Lower
Nile would assume the character of an intermittent wady, such as the
neighbouring Khor Baraka, periodically flushed by the discharge of
the torrential downpours from Abyssinia. Though there is a periodical
increase in the flow of the upper waters of the White Nile, yet the
effect of this, lower down, is minimised by the dense quantities of
vegetable drift, which, combining with the forest of aquatic growth,
forms those vast barriers, known by the name of _sudd_, which not only
arrest navigation but are able to dam up large bodies of water.

The sudd, it is supposed, stopped the