A. Trevor Hodge
An aqueduct was the normal way of transporting water from its source to the point where it was needed, whether for irrigation or urban use. Our evidence for aqueducts comes mainly from two sources, archaeological and literary. The literary sources are, essentially, Vitruvius VIII and Frontinus De aquaeductu. Vitruvius is not always entirely reliable on technical matters, and his exposition is sometimes enigmatic, ambiguous, or obscure (especially on siphons): it seems likely that much of his material was derived from Hellenistic sources, and scholars have even wondered how good his understanding of Greek was. However, since his is the only ancient work on architecture and allied topics that has survived, it has often been treated, especially by architects in the Renaissance, with a respect that it does not always deserve; current scholarship, especially that which is based on engineering, views it with a rather more critical eye.1
Frontinus, speaking with the authority of one who was curator aquarum, head of the Rome waterworks, is our best and fullest evidence, but there are several lacunae in his treatment. First, he deals only with the aqueducts of metropolitan Rome, not with Roman hydraulic practice in general or in other parts of the Empire. Second, he is an administrator rather than an engineer, and as such was more concerned with what we, anachronistically, would call the paperwork than the practicalities of day-to-day operation. Thus he goes into endless detail about the size of the various pipes and the units of water (quinariae) carried, and how it was distributed, but hardly mentions the great bridges and arcades crossing the Campagna. For as long as they were working satisfactorily he had no occasion to pay much attention to them—indeed, one gets the impression that
1 The weakness in much modern scholarship has been the conviction that Vitruvius
knows best, and so if we cannot understand him it is our fault, not his. It has taken
the earthy realism of an engineer to deliver the ultimate insult: “if Vitruvius did
not know what he was talking about then it is hardly surprising that we cannot
find out” (Smith 1976, 58). Callebat 1973, xlix, gives an imposing list of Vitruvius'