"American Bridge Patents: The First Century (1790-1890)" by Emory L Kemp

The nineteenth century saw bridge design worldwide develop at a furious pace. While there was pioneering technical work taking place throughout the world, much of the development in the United States would leave a particularly lasting legacy for future bridge designers. This is because of the invention of a proliferating range of truss forms, some of which are still in use today.

The names of the inventors (Squire Whipple, Theodore Burr, Wendel Bollman, Albert Fink, William Howe) were immortalised by their truss designs. Activity certainly wasn't confined to the USA, with Alfred Henry Neville, Arthur Vierendeel and James Warren amongst the creators elsewhere. Warren's truss remains one of the most popular workhorse designs today, while others receive continued use only through radical reconfiguration (e.g. the use of Fink's truss in inverted form at Royal Victoria Dock Bridge and Forthside Footbridge).

A book covering the history of these designs should therefore make for a very interesting read. "American Bridge Patents: The First Century (1790-1890)" (ISBN 1-933202-06-8, West Virginia University Press, 2005) [Amazon UK] focuses mainly on designs which were recorded by the US patent office, and its main target is the American engineering history community.

Not all the important bridge designs were patented, and exclusion of overseas designs is quite understandable (while the US patent office makes copies of all old patents freely available online, its UK counterpart offers no equivalent access, for example).

The book is in four main sections. The first offers a potted history of American bridge development from 1790 to 1890, focussing on designs which were patented, including catalogue bridges. New bridge types are very rarely (if ever) patented today, but the introduction of new materials during the 19th century saw an explosion of new structural forms which exploited the properties of iron, steel and reinforced concrete. It remains to be seen whether more modern materials (such as fibre-reinforced plastic) hold the same potential to revolutionise not just buildability or durability but also the possibilities of form.

The history covers all the main American designers of the period, and includes copies of some patents, and many patent drawings. Before buying the book, I had expected more of an encyclopaedia of the patents themselves, but I guess this could be somewhat pointless - most of them were unsuccessful, and several heavily flawed. It certainly leaves scope for a far more thorough tome on the subject for an author so inclined.

The second part of the book covers the history of the patent office itself, which wasn't of great interest to me. The third gives a personal view on the joys of bridge patent research, and is accompanied by various reproductions of original watercolour patent drawings. These are rather gorgeous in a way that 21st century CAD renderings rarely are, but printed quite small and it would have been nice to see them at a larger scale.

The final section explains how to find the patents online, with an extensive list of over 600 relevant patents, which is tedious but essential since the patents database can only be searched if you already know the patent number. The list is structured both chronologically and by patent-holder.

There are several topics the book doesn't address, and as a result it's really only a taster for this vast subject. Despite the focus on patent records, it doesn't consider how the patent process affected development of new bridge technologies - whether it facilitated greater commercial competition, or held back the wider adoption of monopolised innovations. There's also little if any explanation in pure structural engineering terms - the reader familiar with bridge design is left to work out for themselves how each structure actually works.

There's nothing here on the fallout from this period: which designs are still used, and why, or which still offer untapped potential for the modern engineer. Essentially, this is a book aimed at the historian, and it doesn't really consider the engineering audience as such.

There's also no index, which is pretty much criminal in a history book!

Overall, I found "American Bridge Patents" a little disappointing, mainly for its lack of depth. The authors acknowledge that its main aim is to document the bridge patent research completed so far, and offer a starting point for future research. Nonetheless, the book's best feature is the large number of original patent illustrations included, featuring many well known bridge designs as well as several which are far more obscure. I'm glad I bought it.

For anyone interested in alternative views, ther are other reviews of the book at the IStructE by Tom Swailes and at the Journal of the Society of Industrial Archaeology by David A Simmons.