Finally...

Finally, we shall turn to descriptions, most of them in a handful of treatises that have come down to us, of water clocks, fountains and various automate, some of which might seem trivial to modern eyes. Yet they exploit concepts, components and techniques that did not enter the armamentarium of European engineering until the time of the Renaissance. The most ancient water-raising machine is the shaduf, a counterweighted lever from which a bucket is suspended into a well or stream.

It appears in illustrations from as early as 2500 BC in Akkadian reliefs and is still in use today in parts of the Middle East. Other traditional water-raising machines, introduced between the third and first centuries B.C., include the screw, or water snail, whose invention is attributed to the great mathematician Archimedes.

It consists of a helical wooden blade rotating within a barrel-like wooden cylinder, a design that could not push water up inclines greater than about 30 degrees, although 20 degrees was more common. A higher lift was achieved by the Noria, a large wheel driven by the velocity of the current. On the outer rim, a series of compartments are fitted in between a series of paddles that dip into the water and provide the propulsive power.

The water is scooped up by the compartments, or pots, and is discharged into a head tank or an aqueduct at the top of the wheel. Norias could be made quite large. The well-known wheels at Hama on the river Orontes in Syria have a diameter of about 20 meters. The noria is self-acting, and its operation thus requires the presence of neither man nor beast. It is, however, expensive to build and maintain.

The “saqiya” is probably the most widespread and useful of all the water-raising machines that medieval Islam inherited and improved. It is a chain of pots driven by one or two animals by means of a pair of gears. The animals push a drawbar through a circle, turning an axle whose pinion meshes with a vertical gear. The gear carries a bearing for the chain of pots, or pot garland – two ropes between which earthenware pots are suspended.

The chain of pots is optimal for raising comparatively small amounts of water from comparatively deep wells. Other mechanisms, however, were required to raise large quantities of water at relatively small distances. The problem can be solved by using a spiral scoop wheel, which raises water to the ground level with a high degree of efficiency.