‹‹‹ Vitr. 10.4.2 | Table of Contents | Vitr. 10.5.1 ›››
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.
3But when it has to be raised higher, the same principle will be modified as follows. A wheel on an axle is to be made, large enough to reach the necessary height. All round the circumference of the wheel there will be cubical boxes, made tight with pitch and wax. So, when the wheel is turned by treading, the boxes, carried up full and again returning to the bottom, will of themselves discharge into the reservoir what they have carried up.
But, if it has to be supplied to a place still more high, a double iron chain, which will reach the surface when let down, is passed round the axle of the same wheel, with bronze buckets attached to it, each holding about six pints. The turning of the wheel, winding the chain round the axle, will carry the buckets to the top, and as they pass above the axle they must tip over and deliver into the reservoir what they have carried up.