We have many books which address one or two aspects of engineering history, but fewer volumes effectively covering the "sweep" of technological improvements. Among the most respected of comprehensive treatments are two volumes, titled "American Building Art. 19th Century", and "American Building Art, 20th Century", by author Carl. W. Condit, published by the Oxford University Press, New York, in 1960 and 1961, respectively.

A fine aspect of Condit's work is that these books are more "readable" than are many works on the history of engineering and technology. Condit manages to give a clear picture with sufficient detail without getting so bogged down in minutiae. He displays an excellent sense of balance in the main text which will satisfy a professional while not overwhelming readers with loads of statistics.

The topics in the first volume are Wood Framing, Iron Framing, the Wooden Bridge Truss, the Iron Bridge Truss, the Suspension Bridge, the Iron Arch Bridge, the Railway Trainshed, and Concrete Construction. The final chapter is An Architectural Appraisal, an aspect missing from too many other books on engineering structures. There are interesting illustrations, and, here again, Condit has a talent for selections which handsomely support his text.

Engineers who must work on Nineteenth Century structures for structural appraisals, remodeling, and rehabilitation will benefit through better understanding of the knowledge and tools available to the original designers. Condit's main theme is the development of the technology used for the important structures of that time period. As might be expected, the first subject is the Colonial background of wood frame construction, which was state-of-the-art for lower cost buildings. Iron framing takes us into the beginnings of the next generation of larger structures. A similar textual progression tells about the changes in bridge design, which faced major new challenges with the advent of heavier, moving loads imposed by railroad trains; dynamic factors had not previously required much designer attention. Of course, there was a high degree of "trial and error" in finally arriving at designs which could be built with a strong sense of being able to rely on safety and durability. A modern reader may be surprised at the coverage of railroad trainsheds, but those were among the largest and design-wise, the most challenging, structures of their day.

Chapters in the second volume are Steel Frames, Structural Complex, the Metropolitan Railway Terminal, Steel Truss and Girder Bridges, Steel Arch Bridges, Suspension Bridges, Concrete Building Construction, Concrete Bridges, Concrete Dams and Waterway Control, The Metropolitan Parkway, and An Architectural Appraisal. Again, there are attractive illustrations accompanying the text.

This volume describes how much, and how rapidly, newly conceived technological approaches were applied to public and private infrastructure up to about 1950. Shells and prestressing were at mid- century the latest techniques for concrete construction. Of course, other improvements since that time have been at least equally dramatic, including the availability of faster and more capable analysis and calculation resources. The railway terminal discussion was inspired in part by the complex facilities constructed in New York. Not only were the structures large, but innovations in tunneling were required to support them. The Parkway discussion addresses not only roads but also important park and open space planning.

The Architectural Appraisal chapters bring together social changes, architectural philosophies, and other factors which affected not only the work of engineers in supporting other esthetic design aspects, but also put into perspective the role of the engineer, how engineers worked within the overall design team, and responded to changes beyond just engineering technology. These chapters provide a fine summary of design and engineers, and give the reader a strong sense of the contemporary factors which influenced construction programs. Both volumes have strong supporting chapter notes at the end (giving more of the statistics and other details) and helpful bibliographies for those wishing to explore further. These books have been long out of print, but most major libraries, both public and academic, should have them. They can be read by engineers with considerable pleasure and will form an important tool when they need historical background to support current work.