— 157 — will ensue, and the land will be sour and unsuitable for cropping. In a natural basin all these circumstances are beyond control and depend solely on the height and duration of the flood. By the construction, however, of suitable sluice-gates, canals and drains, an efficient system of flood irrigation can generally be evolved. As in the previous cases, the cultivator follows the receding water and generally dibbles in his seed with the " seluka " or the " melut." The favourite crops are wheat, barley, millet, maize, lupines and cowpea in the order named.

Flood Cultivation.—While successful basin irrigation is largely a question of engineering and flood control, certain disadvantages are common to all the above types of flood cultivation. The uncertainty of the flood-level, its incidence and duration, the rapid lowering of the water-table and a diminution in the water supply during the period of the crop's maximum demand, the short growing period afforded by this circumstance, and the prevalence of insect pests and plant diseases in all flooded areas discount the advantage of a practically gratuitous water supply. The value of preliminary and subsequent cultivation as a means of conserving moisture and limiting the damage normally sustained from such pests as the cutworm, has been clearly recognised by the authorities, and sustained development will be determined by the possibility of securing a general adoption of the practice by the cultivators themselves.

Artificial Irrigation.—" Sakia " lands generally lie well above the highest flood level, and their irrigation is entirely artificial. The indigenous means employed are the " shadoof" and the " sakia " or Persian Water Wheel.

Shadoofs are worked by manual labour, and are used where small quantities of water are required and the lift does not exceed from 2 to 3 metres. It consists of two posts with a cross piece on which a long lever is pivoted. On the short arm of this lever a weight is fixed, generally consisting of a large ball of mud wrapped in sacking or bound with fibre. This weight acts as a counterpoise to a rod and dipper hanging from the long arm. The dipper is usually a skin bag with wooden rim and a capacity of about 20 litres. With a lift of 2 to 2 metres a man working continuously for one hour can raise about 8-4 m of water.* In view of the exacting nature of the task a total lift of 50 m per diem could not probably be exceeded, for which a normal wage of 35 milliemes would be paid.

Such water would consequently cost the cultivator approximately 0'7 milliemes per m. In 1913, shadoofs to the number of 2,670 were working in the Sudan.

The sakia consists of an endless rope, generally made of palm-leaf fibre, carrying a series of earthenware pots (" qadus ") at intervals of from 2 to 3 feet.

This rope passes over a vertical wheel actuated by a second horizontal wheel by means of engaging wooden pegs or cogs. To the axle of the second wheel a pole * Lang Anderson : " Implements of Irrigation.''