John Rennie: Enlightenment Engineer

June 2004 -- London Bridge—the London Bridge of nursery-rhyme fame—was completed in 1209 and began falling down a mere 60 years later. That was because Eleanor of Provence, who was queen consort to Henry III and was also the "fair lady" of the nursery rhyme, had been given the bridge tolls as a gift from her husband and was spending the revenue on herself rather than on bridge repairs. Fast-forward 600 years, and London Bridge was again falling down. The city of London, which now had control of the structure, decided it had to undertake major repairs. To find out what needed to be done, the city hired John Rennie.

Rennie was one of the Industrial Revolution's leading engineers, along with John Smeaton and Thomas Telford. Today, sadly, these men who created so much of Great Britain's infrastructure during the Industrial Revolution are far less well known than the era's inventors, such as Richard Arkwright and James Watt.

Rennie as Millwright

Born on June 7, 1761, the son of a Scottish farmer, Rennie apprenticed to a millwright and then attended Edinburgh University for three years, where he studied with John Robison and Joseph Black (who had been Watt's teacher and patron at the University of Glasgow). During the summers, Rennie took work constructing and repairing mills in order to earn enough money for his schooling. During the school year, he picked up a fair knowledge of mathematics and the physical sciences, but also learned French and German and mastered the violin and flute. (He also learned to play the bagpipes, which, said an early English biographer, "does not say much for his musical taste.")

Rennie began his professional career by building the Albion Flour Mill for James Watt and Matthew Boulton. (For more on Boulton and Watt, see "The Industrial Revolution's Indispensable Entrepreneur," Navigator, September 2003.) Doubtless William Blake and the Romantic Age that followed the Enlightenment would have considered Rennie's factory to be a "dark Satanic mill" and the name "Albion" to be a desecration. But to men of the Enlightenment, Rennie's mill was reckoned a marvel for its innovative use of iron and steam.

Rennie as Civil Engineer

Despite his background and success as a millwright, Rennie soon turned away from mechanical engineering and devoted the majority of his career to civil engineering projects: canals, docks, harbors, and bridges. Indeed, after the retirement of the great John Smeaton in 1791, Rennie was so frequently consulted about civil engineering projects that it is hard to see how he was able to handle them all. Biographers mention his involvement with at least twenty canal constructions and more than 50 other major undertakings, notably bridges.

One early canal project entrusted to him personally as a designer and engineer was a canal that would connect Reading and Bath: the Kennet and Avon Canal, begun in 1794 and completed in 1810. A second Rennie project was the Rochdale Canal (also begun in 1794 but completed in 1804), which linked the manufacturing districts of West Yorkshire and South Lancashire.

Another branch of Rennie's career would shock modern sensibilities: draining wetlands. The largest of these projects involved the fens of Lincolnshire, which covered some 75 thousand acres. As it happened, one of the houses of Joseph Banks, president of the Royal Society, overlooked these fens, and he had spent many years trying to organize a local effort to have them drained. Finally, during the Napoleonic Wars, when food was scarce and arable land in great demand, Banks persuaded a group of adjoining proprietors to authorize Rennie to undertake the project. The plan, obvious enough in retrospect but innovative in its time, had two aspects: diverting incoming water and cutting channels sufficiently deep to remove low-lying water. The second part was the more difficult because no nearby river was low enough, with respect to the lowest parts of the fens, to serve as an outlet. Therefore, Rennie had to cut a drain eighteen miles long and 40 feet wide, dropping four inches per miles until it reached the sea.

But the high point of Rennie's career was undoubtedly his bridges, and, in particular, his bridges over the Thames. The first of these was Waterloo Bridge. Begun in 1810 and completed in 1817, it was made of worked granite stones and had nine arches with a span of 120 feet each. At its opening, the prince regent offered to confer a knighthood on Rennie but, thoroughly a man of the Enlightenment, he declined and wrote to a friend: "I had a hard business to escape knighthood at the opening." Rennie's second Thames bridge was Southwark Bridge, which was made of cast iron and had just three record-breaking spans of 240 feet each.

New London Bridge was to be Rennie's third Thames span, and his design called for five masonry arches totaling 690 feet. Naturally, the plan had opponents who argued that the old bridge could be patched. But Rennie's testimony carried the day. Unfortunately, he never had a chance to build his bridge. Shortly after Parliament approved the project, Rennie took ill and died. To replace him, the city selected his son, who completed the bridge in 1831.

Of all the many works created by the civil engineers of the Industrial Revolution, New London Bridge seems especially symbolic of the age's truly revolutionary nature. Look at it this way: The London Bridge that Rennie's replaced was built in 1097 by order of William II, son of the Conqueror. In that sense, the old bridge typified the many ways in which ancient England still persisted prior to 1750. The country was still agrarian; it was still based on muscle-power and water-power; and it was still ruled to a significant degree by a monarch. The Industrial Revolution—and its intellectual framework, the Enlightenment—changed all that, and the replacement of Old London Bridge by New London Bridge was a symbol of that change.

Interestingly enough, Americans now have relatively easy access to that revolutionary symbol. For when Rennie's New London Bridge was replaced in the 1960s, it was dismantled and rebuilt in Lake Havasu City, Arizona. It is, surely, one of the few major memorials to the British Industrial Revolution that can be seen in the United States.

This article was originally published in the June 2004 issue of Navigator magazine, The Atlas Society precursor to The New Individualist.

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