‹‹‹ Vitr. 8.6.8 | Table of Contents | Vitr. 8.6.10 ›››
9Thus adjusting the direction of the tubes, both in the descents and acclivities, the work will never be dislodged. For a great rush of air is generated in an aqueduct, strong enough to break even stones, unless the water is softly and sparingly let down from the head, and unless in elbows or bending joints it be restrained by means of ligatures, or a weight of ballast. In other respects it is similar to one with leaden pipes. When the water is first let down from the head, ashes are put in which will stop those joints not sufficiently coated. Earthen pipes have these advantages, first as to the work; next, that if damaged any one can repair it.
9The level of the pipes being thus adjusted, they will not be sprung out of place by the force generated at the descent and at the rising. For a strong current of air is generated in an aqueduct which bursts its way even through stones unless the water is let in slowly and sparingly from the source at first, and checked at the elbows or turns by bands, or by the weight of sand ballast. All the other arrangements should be made as in the case of lead pipes. And ashes are to be put in beforehand when the water is let in from the source for the first time, so that if any of the joints have not been sufficiently coated, they may be coated with ashes.