Colin O'Connor, Roman Bridges. Cambridge: Cambridge University Press, 1994. Pp. xvii + 275. $100.00. ISBN 0-521-39326-4.
Reviewed by Harry B. Evans, Fordham University.
O'Connor, a professor emeritus of civil engineering and expert in bridge construction, sets out to assess the Romans' achievement as "the world's first major bridge builders" (p. 1). The result is a highly informative book, not inexpensive, but very attractively produced by Cambridge, and amply illustrated by photographs and sketches, most of them the author's own. Although O'Connor's book does not replace Piero Gazzola's definitive study of Roman bridges (Ponti Romani, Florence, 1963), on which it relies heavily, it does make important contributions of its own to our understanding of how Roman bridges were built and why they stayed up (or failed to do so) when completed.
O'Connor organizes his study geographically (in contrast to the chronological organization followed by Gazzola) and therefore begins with an overview of the Roman road system, which determined the location of the bridges themselves: "Bridges and roads go together, for it is the roads which require the bridges, and the bridges make possible the roads" (p. 4). His survey of the Roman road system is in good part derivative, based on the work of Chevallier and Sitwell, but this opening chapter provides a convenient geographical framework for the bridges to be discussed later and makes this book much easier to consult on particular bridges than Gazzola's. In addition, his plates and diagrams are much larger and more readable than those in Gazzola.
Chapters on Roman builders, technology, and building materials introduce the heart of the book, a survey of masonry bridges throughout the Roman world. O'Connor's presentation of individual bridges is based in large part on that of Gazzola, but he has obviously visited and studied a good many of the monuments he describes, and several times he is able to correct figures and statistics given in Gazzola's study (pp. 81, 100, 101, 109, 117).
The most interesting section of the book treats a subject not fully addressed by Gazzola, the Romans' use of timber bridges. These structures, O'Connor argues, were especially common in Roman Britain but were built extensively throughout the Roman world, frequently preceding later masonry constructions: "stone bridges were likely to be second- or third-generation structures, built to replace earlier crossings, constructed in a stable environment, with access to adequate and known resources and a developed infrastructure (p. 132)." Using Caesar's famous account of his bridge across the Rhine (BG 4.17), he presents a plausible reconstruction of the bridge and the engineering problems Caesar faced in completing the span in ten days. Even more fascinating is his detailed discussion of Trajan's bridge across the Danube, designed by Apollodorus of Damascus and depicted on well known reliefs of Trajan's column; O'Connor argues that Apollodorus used twenty-one segmented timber arches to span the river and create longest bridge ever built by the Romans.
The only disappointing chapter is O'Connor's discussion of Roman aqueduct bridges. He acknowledges that he was not able to consult Trevor Hodge's Roman Aqueducts and Water Supply (London, 1992) while he was writing his book and therefore describes his listing of aqueduct bridges as "fortuitous and incomplete" (p. 150); unfortunately we must agree. O'Connor's discussion of Rome's aqueduct bridges, based largely on Ashby and Van Deman, omits completely the Aqua Appia, Anio Vetus, and Aqua Traiana. The Traiana, of course, has large sections above ground, some of which were later reworked by Paul V for his papal aqueduct in the sixteenth century. The Appia and Anio Vetus were largely underground conduits, but both are certainly worth a mention in any survey of Roman bridges. The Appia, according to Frontinus (Aq. 5.5) crossed the valley of the Porta Capena on an arcade of 60 passus). If this were a masonry bridge from the time of the line's introduction (312 B.C.), it might well have been the oldest continuous arcade in Roman architecture; if A. W. Van Deman [RE 8A (1955) 468] is correct, however, the arcuatura cited by Frontinus may have been part of a second-century restoration of the Appia, replacing an earlier fourth-century timber structure. In any case, the Aqua Appia bridge at the Porta Capena merits discussion. Even more surprising is O'Connor's omission of the Hadrianic "Ponte della Mola" of the Aqua Anio Vetus, one of the most interesting examples of imperial upgrading of the republic lines and a fascinating bridge in itself, as well as Nero's Arcus Caelimontani and the Domitianic bridge in the Valle S. Gregorio which carried this branch line of the Aqua Claudia to the Palatine Hill, the reconstruction of which remains controversial. O'Connor's discussion of aqueduct bridges in Spain and Gaul is better, since he had access to the studies of Casado (Madrid, 1972) and Grenier (Paris, 1935), but this one adds very little that is new and might well have been omitted altogether.
Much better are his two final chapters on the design and construction of Roman arches and modern analysis of Roman arch design. Both treat highly technical subjects, which will no doubt be of more interest to engineers than to classicists, but O'Connor's discussion of loads, reactions, pier thicknesses, and falsework construction is highly illuminating, indeed the place to which I will send all future students who are interested in such problems. Both chapters include very clear diagrams and graphs. The book also contains a glossary of technical terms and appendices listing 330 masonry bridges, all organized geographically, 34 timber bridges, and 94 aqueduct lines, as well as a list of works cited.
O'Connor is a civil engineer, not an ancient historian or classicist. His background therefore contributes directly to the strengths of this book: we have here a thoughtful examination of Roman bridge building by a professional who is well aware of the problems of engineering and construction techniques. The best parts of the book are therefore those directly focussed on such topics as the statics of arch design, why the Narni bridge collapsed, or Apollodorus' bridge over the Danube. There are, however, many errors of historical detail in O'Connor's text which the readers for Cambridge should have caught: to give some examples, the third king of Rome was Ancus Marcius, not Martius (pp. 2, 7, 142), the First Triumvirate is not to be dated to 59 B.C. (p. 16), the heir to Julius Caesar was Octavian, not Octavius (p.36), and Clemens Herschel did not discover a manuscript of Frontinus in 1897 (p. 37).
In addition, there are some startling omissions in the extensive bibliography. O'Connor briefly discusses the religious significance of bridges (pp. 2-3) but curiously does not cite Louise Adams Holland, Janus and the Bridge (Rome, 1961), a source which should have also appeared in his treatment of the Pons Sublicius (pp. 141-42). His presentation of Marcus Agrippa as a bridge builder appears to be entirely based on F. A. Wright's biography of more than fifty years ago (Marcus Agrippa: Organizer of Victory, London, 1937) and ignores J.-M. Roddaz's much more recent and comprehensive study (BEFAR 253, Rome, 1984). The chapter on aqueduct bridges relies much too heavily on outdated sources like F. W. Robins, The Story of Water Supply (Oxford, 1946), and one surprising omission in his discussion of timber bridges is Russell Meiggs, Trees and Timber in the Ancient Mediterranean World (Oxford, 1982).
These disappointments aside, O'Connor has given classicists a fresh look from an engineer's perspective at the Roman achievement in bridge building. As his concluding chapter states, Roman bridges are impressive not only for the number of them documented or the extent to which they were built throughout the Roman world, but also for the technology involved: arched bridges required skills in site location and layout, choice of construction materials, employment of lifting devices, the fastening of falsework and other supports, and use of proper tools and equipment. His book ably demonstrates how the Romans combined all these skills to produce "one of the most successful, extensive and lasting of all human, material achievements" (p. 188). This volume will not replace Gazzola's monumental Ponti Romani, but it does present to its readers a comprehensive and much more usable account of bridges and bridge building in the Roman world. Order it for the library, because you and your students will be consulting it sooner or later, and more than once.