John Rennie the Younger: The Last of a Bygone Race
On 18 April 1968 an American oil entrepreneur named Robert McCulloch paid $2,460,000 for a bridge. Every granite facing block was numbered, shipped through the Panama Canal, trucked into the Arizona desert and reassembled over the Bridgewater Channel at Lake Havasu City, where it was rededicated in 1971 with London's Lord Mayor in attendance. The structure was John Rennie the Younger's London Bridge, opened in 1831. Not many engineers build something a foreign millionaire will later buy, dismantle and carry across an ocean rather than let be destroyed.
Born Into the Firm
He was born on 30 August 1794 at 27 Stamford Street, Blackfriars Road, London — the second son of John Rennie the Elder, one of the towering British engineers of the age, and brother to George Rennie. He was educated by Dr Greenlaw at Isleworth and Dr Charles Burney at Greenwich, and in 1809, at fifteen, entered his father's engineering firm.
There was no separation between education and apprenticeship. He learned the practical side at his father's Holland Street manufactory, then went onto the works themselves: in 1813 he was on the foundations of Waterloo Bridge under the resident engineer Hollingsworth, and from 1815 he assisted his father on Southwark Bridge. In 1819 he travelled abroad to study engineering works ancient and modern, developing his hydraulics and his architectural sense.
By his mid-twenties he had done what few engineers of any era manage: worked on three great Thames bridges before designing anything of his own.
Inheritance
His father died in 1821, and the sons divided the practice — George taking mechanical engineering, John the civil side. He also inherited the post of Engineer to the Admiralty.
The largest inheritance was London Bridge. The design was his father's; the construction, from 1824 to 1831, was his. This was not a simple matter of following drawings. The project generated political disputes serious enough to require five Cabinet ministers to sit on the parliamentary committees. When William IV opened the bridge in 1831, Rennie was knighted — the first man of his profession to be so honoured since Sir Hugh Myddleton.
Water
Rennie's real subject was water: how to hold it back, guide it out, and build in it.
At Plymouth he completed the Breakwater, one of the most demanding marine works then attempted anywhere, and later published an *Account of Plymouth Breakwater* in 1848. He built the Royal William Victualling Yard at Plymouth between 1823 and 1833 with Philip Richards, and the Cannon Workshops in 1824–25. As Admiralty engineer he completed Sheerness Dockyard and Ramsgate Harbour, built major docks at Woolwich, and modernised Chatham Dockyard, work running to 1862. He altered harbours at Kingstown, Portpatrick, Portrush, Donaghadee, Cardiff and Whitehaven, restored Boston harbour in 1827–28, improved the Welland, and designed a dry dock at Rushbrooke near Cork in the 1850s.
Then there was the drainage work, less glamorous and arguably more transformative. He completed the Eau Brink cut near King's Lynn in 1822, dropping the Ouse water level by seven feet. With Thomas Telford he worked the Nene outfall from 1826 to 1831, lowering levels by ten or eleven feet. He proposed reclamation schemes covering 150,000 to 200,000 acres, though political opposition kept most of them on paper. He built Horkstow Bridge in 1835–36, one of the earliest suspension bridges to survive, and carried out the River Ancholme drainage scheme.
Railways, and a Losing Argument
With his brother George he designed the Liverpool and Manchester Railway in 1825–26, and proposed a gauge of five feet six inches — a deliberate compromise between the broad and narrow options. George Stephenson instead adopted the colliery standard of four feet eight and a half inches, and that is the gauge most of the world runs on today.
Rennie kept working in railways: supplying locomotives to the London and Croydon Railway in 1838–39, laying out the Swedish railway system in 1852, and planning Portuguese railways and harbours in 1855, most of which were never built. The Swedish work brought him the Order of Gustavus Vasa; Portugal gave him the Order of the Tower and Sword; Italy the Order of St Maurice and Lazarus; and the Russian and Austrian sovereigns honoured him for his book on harbours.
The Profession
He was elected a member of the Institution of Civil Engineers on 25 June 1844 and its president on 21 January 1845, serving three years. His 1846 presidential address was a complete history of the rise and progress of the profession — an act of self-definition by a discipline that had barely existed when his father started.
He wrote a great deal: papers on Ancholme drainage and Newry River navigation, letters to *The Times* on water management and river regulation, and the substantial *Theory, Formation, and Construction of British and Foreign Harbours* of 1851–54. He left manuscripts on hydraulics, drainage and reclamation. He was a long-standing member of the Royal Society, a foreign member of the Royal Swedish Academy of Sciences, and with Sir Humphry Davy an early associate in founding the Zoological Society. He was fluent in several languages and well read in general literature.
Why John Is Called a Genius
The word sits uneasily on him, and it is more honest to say what the profession actually said. His obituarists judged that he stood alone, the last of a bygone race — the living connection between Brindley, Smeaton and Telford and the era of Stephenson and Brunel. That is a claim about position in a lineage, not about originality, and it is the accurate one.
The distinctive quality was mastery of a specific and brutal domain: building permanently in and against moving water. Anyone can design a structure for dry ground. Rennie's career was foundations sunk in tidal riverbeds, a breakwater assembled in the open sea at Plymouth, drainage cuts that dropped the water table across whole counties by measured feet, and dockyards that had to work for the Royal Navy. The knowledge required is unglamorous and unforgiving — hydraulics, sediment, tide, the behaviour of masonry under constant saturation — and it cannot be improvised. That he was decorated by the Swedish, Portuguese, Italian, Russian and Austrian states for it suggests the expertise was genuinely scarce.
The counter-case is strong and starts at the top. His most famous work, London Bridge, was his father's design; he was the builder and the political operator, not the author. He inherited a firm, a reputation and an Admiralty post rather than building them. His one major original contribution to railway practice — the five-foot-six-inch gauge — lost to Stephenson. Many of his boldest ideas, the vast reclamation schemes and the Portuguese railways, were never executed. He was a superb executor and consolidator working inside a family franchise; the era's real conceptual leaps belong to Stephenson and Brunel, and his own colleagues effectively said so when they called him the end of an older tradition rather than the beginning of a new one. He seems to have known it. He was described as bearing no envy or malice, and his memoirs contained kind notices of everyone he dealt with — including generous praise for Stephenson, the man who beat him.
Afterward
He retired around 1862 and died on 3 September 1874 at Bengeo near Hertford, days after his eightieth birthday, and was buried at Kensal Green.
His harbours and dockyards still do their work, mostly unnoticed, which is the fate of good marine engineering. His drained fenland is farmland. And his bridge, replaced in London by a concrete box girder in 1973, sits in the Arizona desert, sold whole, shipped abroad and re-erected as a monument to itself.
Achievements
- Fellow of the Royal Society
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