4I shall now explain the machines for raising water, and their various sorts. And first the tympanum, which, though it raise not the water to a great height, yet lifts a large quantity in a small period of time. An axis is prepared in the lathe, or at least made circular by hand, hooped with iron at the ends; round the middle whereof the tympanum, formed of planks fitted together, is adjusted. This axis rests on posts also cased with iron where the axis touches them. In the hollow part of the tympanum are distributed eight diagonal pieces, going from the axis to the circumference of the tympanum, which are equidistant.
2The horizontal face of the wheel or tympanum is close boarded, with apertures therein half a foot in size to admit the water. On the axis also channels are cut for each bay. This machine, when moored like a ship, is turned round by men walking in a wheel attached to it, and, by receiving the water in the apertures which are in front of the wheel, brings it up through the channels on the axle into a trough, whence it is conducted in abundance to water gardens, and dilute salt in pits.
3If it be necessary to raise the water to a higher level, it must be differently adjusted. The wheel, in that case, applied to the axis must be of such diameter that it shall correspond with the requisite height. Round the circumference of the wheel buckets, made tight with pitch and wax, are fixed; thus when the wheel is made to revolve by means of the persons treading in it, the buckets being carried to the top full of water, as they return downwards, discharge the water they bring up into a conduit. But if water is to be supplied to still higher places, a double chain of iron is made to revolve on the axis of the wheel, long enough to reach to the lower level; this is furnished with brazen buckets, each holding about a gallon. Then by turning the wheel, the chain also turns on the axis, and brings the buckets to the top thereof, on passing which they are inverted, and pour into the conduits the water they have raised.