24 July 2018

"Samuel Brown and Union Chain Bridge" by Miller and Jones

Union Chain Bridge is the oldest suspension bridge in the world which still carries vehicular traffic. Opened in 1820 to a design by Captain Samuel Brown, it is remarkable that it has survived so long, especially considering that so many of Brown's other bridges failed early in their lives. The bridge will reach its bicentenary in two years time, and the publication of this book is therefore timely.

Samuel Brown and Union Chain Bridge (Friends of the Union Chain Bridge, 306pp, ISBN 978-1-5272-1616-7) is the end result of extensive research by architect Gordon Miller, commenced in the early 1970s. Most of the content has not seen print before, although Miller published a paper in the ICE Proceedings in 2006 which summarised some of the Union Bridge story. Sadly, Miller passed away in February this year after completing this book.

The first, and lengthiest, section of the book explores Captain Samuel Brown's career, first as a naval officer and then as a pioneering supplier of iron chains. Initially, he developed chains for use in the navy as anchor cables and rigging. In 1813, he built an experimental 100-foot long suspension bridge at his Millwall chain factory, which was visited by eminent engineers such as Rennie and Telford. This led directly to the use of chains to suspend the Union Bridge, and soon to many more structures, principally built in the period from 1820 to 1832, with Brown's last bridge built in 1834. 

Miller's book recounts far more detail on Brown's many bridges than has been published anywhere before, drawing in depth on the surviving archive papers. However, this lengthy section of the book is not well structured, with no subheadings to help identify individual structures, and a number of digressions. The material is also in some cases curiously incomplete - the best known previous survey of Brown's works was in Emory Kemp's 1977 paper, which although briefer than this new book included some details which Miller omits. A useful chronology of Brown's work can be found at Engineering Timelines.

Comparing Miller's account against other books and papers relating to Brown, I'm left with as many questions as answers. Some other accounts report that Brown won the Union Bridge contract in competition with North Shields chain-maker Robert Flinn; elsewhere this is said to relate to a proposal for Norham Bridge circa 1817-1818. Miller's book does nothing to clarify the matter, with Flinn barely mentioned at all and no reference to any competition.

There are also unfortunate errors, such as citing Brunel as the designer of the Menai Suspension Bridge. These are not errors of knowledge, but can be put down to the absence of any kind of editor or proof-reader. This also explains the poor and inconsistent structure to the book. There is no kind of referencing throughout, and coupled with the other flaws, I have to say that for any serious student of bridge engineering history, this makes the book very difficult to trust. It is a terrible missed opportunity.

The lack of referencing means that previous documentation on Brown and his works is largely ignored: Kemp's paper is barely acknowledged, Day's papers are ignored entirely, as is Paxton's paper, which is a shame as it includes a useful numerical appraisal of the strength of Brown's chain designs, putting his practice into the context of what his contemporaries were doing.

The core of the book is an account of the Union Chain Bridge itself, its design, construction and opening as a toll bridge. Much of this is drawn from the records of the bridge trust, and it is thorough and informative. As is the case throughout the book, a great deal of contemporary record material is reproduced directly, including correspondence, images of the original bridge drawings, and Brown's 1817 patent. It's thorough, but sometimes a mixed bag, with many pages given over to exact reproductions of primary sources.

There is also a great deal of information on the bridge's history post-construction. This section includes an excellent set of sketches and details which illustrate how the bridge deck was modified on numerous occasions. Many of these were drawn up at the time of the bridge's major refurbishment in 1974.

Correspondence between the bridge trust and their consulting engineer at various stages is included, reporting continuing doubts about the strength of the bridge which had never really gone away since its original construction. The bridge's south anchorage was strengthened at the time of construction, and the north anchorage in 1902. The saddle details were a perennial problem: at the outset, a roller arrangement was provided to address thermal expansion, but the chains were allowed to rub on the edge of their support, and the hidden nature of the saddles inevitably led to progression of unseen corrosion at various stages.

I think that anyone looking for an in-depth understanding of 19th century bridge engineering history in Britain, or anyone with a deep interest in the history of suspension bridges, will regard this book as an essential purchase. However, it is grievously let down by the lack of any intervention from an editor, and the lack of proper referencing. For any more casual reader, the article at Engineering Timelines is a good enough introduction to the subject, and I can't recommend this book to them.

Further reading:

1 comment:

GRB said...

It is very beautiful It's interesting that the deck is arched upwards in the center and somewhat mirrors the sag in the main cables. Do you happen to know what the load limit is of this bridge? It's quite remarkable that it has endured for such a long period of time.