SKETCH DIAGRAM OF TABÛT.
Drawn with side as if transparent, to show water in compartment, and principle.
The saqya mawâshi (saqya worked by cattle) and the shadûf are also employed to a small extent, as elsewhere in Egypt, but only for small areas.
There are 205 saqya hedêrs in the province. To obtain a license to erect one, the applicant has to pay L.E. 1 to get his application accepted, and L.E. 5 more, if the license is granted.
Water-mills.—The fall of the water is also used to turn mills for grinding corn, of which there are 243 in the province, which paid as tax in 1891 a total of 810l. (L.E. 791).
[Plate VI.] is from a photograph of one of the falls, below which are first a pair of tabût wheels, one behind the other, for lifting water to high-level lands, and, below these in the same mill-race, an undershot wheel working a mill for grinding corn.
The mills are worked either by turbines (panchakkis) of a pattern introduced from India thirty years ago, according to Mr. Willcocks, or by undershot wheels. The latter method is used, where the fall available to work the mill is small, but not less than 60 centimetres. The former system requires a fall of at least 1·60 metres.
Falls and Regulators.—For purposes of irrigation the fall of the country surface is excessive, and works have to be built at intervals along a canal, after the point where it begins to irrigate, to hold up the water-surface to a sufficient height to flow over the fields. These works are generally placed where the canal splits up into branches, and they take the form of a collection of small weirs. Where the maximum water-levels below all the weirs of such a group never rise above the level of their weir-sills we have a “free fall” in the case of each weir, and the discharge over each sill is directly proportional at all seasons to the length of the sill, which in each weir is made proportional to the area irrigated from the canal below the weir. Thus the collection of weirs not only holds up the water for the irrigation from the canal above it, but acts automatically as a just distributor of water to the canals below it. Such a group of weirs is called a nasbah, an Arabic word signifying “proportion.” The arrangement is thoroughly understood and appreciated by the Fayûm cultivators, and is useful in rendering unnecessary the employment of a numerous establishment of low-paid agents—a great end to gain in a country where the inferior employés are so easily corrupted.
There are, besides the nasbahs, a large number of small masonry works, as head regulators, sluice heads to branch canals, syphons, aqueducts, and pipe heads scattered all over the province, but there is nothing peculiar in them as irrigation works.