To judge from the literature on Roman engineering, there was a time when the history of bridge building was a prominent theme closely associated with a parallel and equally well-developed interest in Roman roads. Recently, as a result of a variety of new approaches to archaeological, technical and social themes, the emphasis has moved to aspects of hydraulic engineering and, in particular, problems of water power and water supply. Of course, fashions in engineering history, Roman or later, are bound to change from time to time. That is understandable and nothing new. On the other hand, any overall view of Roman civil engineering needs to integrate the various approaches, especially in so far as they affect one another. Bridge building, after all, is bridge building, whether the structures are for roads or aqueducts and, in this lecture, both functions will be considered.
However, before turning to engineering historical matters, it is important to notice, even briefly, a few points about method that are fundamental to comprehending the ancient past and especially its engineering. It is noticeable how frequently engineers who write history are disposed to imagine that any failure to comprehend early engineering is essentially a failure of modem intelligence. Too rarely is it realised that the real problem is a failure of the ancient evidence to reach the minimum level that comprehension and conclusions require. Nor, contrary to a number of recent exercises, is it a foregone conclusion that resort to modem analytical devices and computation is a means of making good gaps and faults in the evidence or illuminating problems of interpretation. What is more, and what is often worse, is that retrospective analysis of all manner of ancient technologies – machines, ships or metallurgical processes, never mind structures -can often become a debate about the validity of analytical methods p e r se and the historical issues are lost sight of. When it comes to trying to comprehend the Roman engineer's thoughts and ideas about design and construction, one must never forget that the evidence from the structures themselves is no substitute for the written word – and that commodity is always rare and frequently ambiguous.
The Structural Engineer, Volume 71 No 914 (1993)