There are two kinds of wheels used, one in which the water lifted is contained in earthenware jars fastened to the side of the wheel near its outer edge, the arrangement of which is shown by the drawing, reproduced from Willcocks’ ‘Egyptian Irrigation’ ([Plate V.]) The other kind of wheel, called a tabût, has a hollow chambered tube of square cross-section forming its circumference, the holes to admit water into each chamber being made in such a position that the water, which enters the chamber when submerged, does not commence to flow out again, till the chamber approaches the highest point of its path. Below the point, at which the flow out commences, a trough is placed to catch the water.
It will be seen that in both these arrangements there is a loss of work in lifting the greater part of the water rather higher than the level at which it is utilised. The principle of the tabût will be understood from the drawing given on the same [plate No. V.,] as the other arrangement with pitchers. Either kind is known as a saqya hedêr.
Plate IV.
HIGH-LIFT WATER-WHEELS ON THE TAMÎYAH CANAL.
The pair of wheels shown on this Plate raise the water 4·50 metres, and are worked by a total fall of water of 0·55 metres.
As a means of estimating the heights and widths in the Plate, the widths of the arches are given.
Left-hand arch, 3 metres span; next arch on its right, 2½ metres span.
Plate V.
UNDERSHOT WHEEL FOR RAISING WATER.
Scale ¹⁄₅₀. From Willcocks’ ‘Egyptian Irrigation.’