smaller irrigation-channels. While the invention of the
system of basin-irrigation was practically forced on Egypt,
the extraordinary fertility of Babylonia was won in the
teeth of nature by the system of perennial irrigation, or
irrigation all the year round. In Babylonia the water was
led into small fields of two or three acres, while the Nile
valley was irrigated in great basins each containing some
thirty to forty thousand acres. The Babylonian method gives
far more profitable results, and Sir William Willcocks
points out that Egypt to-day is gradually abandoning its own
system and adopting that of its ancient rival; see _The Near
East_, Sept. 29, 1916, p. 521.

(2) See Le Strange, _The Lands of the Eastern Caliphate_, p.
27.

The second great blow to the system followed the Mongol conquest, when
the Nahrwan Canal, to the east of the Tigris, had its head swept away
by flood and the area it had irrigated became desert. Then, in about
the fifteenth century, the Tigris returned to its old course; the Shatt
el-Hai shrank, and much of the Great Swamp dried up into the desert
it is to-day.(1) Things became worse during the centuries of Turkish
misrule. But the silting up of the Hillah, or main, branch of the
Euphrates about 1865, and the transference of a great part of its stream
into the Hindiyah Canal, caused even the Turks to take action. They
constructed the old Hindiyah Barrage in 1890, but it gave way in 1903
and the state of things was even worse than before; for the Hillah
branch then dried entirely.(2)

(1) This illustrates the damage the Tigris itself is capable
of inflicting on the country. It may be added that Sir
William Willcocks proposes to control the Tigris floods by
an escape into the Tharthar depression, a great salt pan at
the tail of Wadi Tharthar, which lies 14 ft. below sea level
and is 200 ft. lower than the flood-level of the Tigris some
thirty-two miles away. The escape would leave the Tigris to
the S. of Samarra, the proposed Beled Barrage being built
below it and up-stream of "Nimrod's Dam". The Tharthar
escape would drain into the Euphrates, and the latter's
Habbaniyah escape would receive any surplus water from the
Tigris, a second barrage being thrown across the Euphrates
up-stream of Fallujah, where there is an outcrop of
limestone near the head o