Scotsman John Rennie (senior) dominated the civil engineering profession of his time, with his pioneering ideas and unerring ability to translate them into finished projects. His diverse range of work included bridges, canals, fen drainage, river navigations, docks and harbours. Noted for his thoroughness, he was frequently called upon to adjudicate on the design work of his contemporaries.

As a boy Rennie was fascinated by machinery, and at the age of 12 he began working for millwright Andrew Meikle (1719-1811). Six years later, Rennie established his own millwrighting business and went on to combine a growing workload with academic studies at Edinburgh University.

In 1783, he met James Watt (1736-1819), who later offered him a contract for the installation of Boulton & Watt steam engines, including those at Albion Mills in London, designed by Samuel Wyatt (1737-1807). This project established Rennie's reputation. Wherever motive power was needed, he had an idea for using steam — in mills of all kinds, smithies, ships and even in London's Royal Mint.

Rennie's focus moved to civil engineering when he began working on canals, with the backing of an endorsement from inspirational engineer John Smeaton (1724-92). The bridge-building for which he is best remembered started with masonry structures over these canals. Towards the end of his career, he designed the granite London Bridge (1831) that was later famously purchased by American businessmen and re-erected in the Arizona desert.

He also designed iron bridges — then a developing technology. In fact, Britain's longest cast iron span was part of Rennie's Southwark Bridge (1819), of which he said, "On the whole nothing in which I have ever been concerned has proved more satisfactory than this bridge".

Rennie's habitual attention to detail and heavy workload drove him to work 12-15 hours a day. He built things to last, which sometimes led to criticism of his work on grounds of size or cost. However, his expertise was recognised by promoters, who knew his name would lend authority to any scheme with which he was associated.

He was invited by Smeaton to join the Society of Civil Engineers (founded 1771, later renamed the Smeatonian Society) and he became a Fellow of the Royal Society, though he declined the knighthood offered for his work on the original Waterloo Bridge. Among his nine children are engineers George Rennie (1791–1866) and Sir John Rennie (1794–1874), both of whom would hold office as presidents of the Smeatonian Society.

Rennie, a lifelong Presbyterian, is described as charming and determined — a man who maintained friendships despite a somewhat short temper. He was one of the greatest civil engineers of his era, and it is a shame how few of his structures remain to remind us of his genius.

1761	Born 7th June, ninth and youngest child (three brothers, five sisters) of farmer and brewery owner James Rennie (c.1715-66) and Jean Rennie (1729-90)
1773	Works for millwright Andrew Meikle (1719-1811), learning the practicalities of mechanics
1775-7	Attends Dunbar secondary school
1779	Sets up his own millwright business
1780-3	Studies natural philosophy and practical sciences at University of Edinburgh, where he meets Joseph Black (1728-1799) and John Robison (1739-1805)
1783	Study tour of England, meets James Watt (1736-1819), who later (1784) offers him a contract for installing Boulton & Watt steam engines
1790	Marries Martha Ann Mackintosh (1771-1806), 6th November at Christchurch, Blackfriars Road, Southwark (nine children)
1790	Appointed Surveyor to the Kennet & Avon Canal (built 1794-1810)
1791	Appointed Surveyor/Engineer to the Rochdale Canal (built 1794-1804)
1798	Elected Fellow of the Royal Society
1817	Declines a knighthood
1821	Dies of liver disease, 4th October, at his residence in Stamford Street (London), interred in the crypt of St Paul's Cathedral

Lancaster Canal, Lancashire, UK .... begun 1792
Lune Aqueduct, Lancashire, UK .... 1794-1796
Great Bedwyn Skew Bridge, Wiltshire, UK .... 1794-1816
Leith Docks, Leith, Edinburgh, UK .... begun 1800
Kelso Bridge, Borders, Scotland, UK .... 1801-1804
Devizes Locks, Kennet & Avon Canal, Wiltshire, UK .... opened 1810
Plymouth Breakwater, Devon, UK .... begun 1812
Old Waterloo Bridge, London, UK .... 1811-1817
Sheerness Dockyard, Isle of Sheppey, Kent, UK .... 1813-1821
Old Southwark Bridge, London, UK .... 1815-1819
Kingstown Harbour, County Dublin, Ireland .... 1817-1821, completed 1836
London Bridge (1831), London, UK .... designed 1821, built 1824-1831

Rennie, John (1761-1821), Dictionary of National Biography,
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Andrew Saint, Rennie, John (1761-1821), Oxford Dictionary of National Biography, Oxford University Press, 2004, online edn May 2009

Alec Skempton ed., Rennie, John, FRS, FRSE (1761-1821), A Biographical Dictionary of Civil Engineers in Great Britain and Ireland, Volume 1: 1500-1830, Thomas Telford Publishing Limited, Institution of Civil Engineers, London, pp.554–569

GB 237 Coll-168, archive of letters written by John Rennie held at Edinburgh University Library, Edinburgh, Scotland, UK

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Roland Paxton ed., John Rennie (1761-1821), FRSE, FRS, civil engineer: Contemporary biographical notices reprinted on the 250th Anniversary of his birth, Heriot Watt University, Edinburgh, 2011

Ted Ruddock, John Rennie and Waterloo Bridge, London, UK, Proceedings of the ICE: Engineering History and Heritage, Vol.164, 1st Aug 2011, pp.155-162

Samuel Smiles, Lives of the Engineers, Volume 2, John Murray, London, 1862

Tom Swailes, Southwark iron bridge, London, UK, Proceedings of the ICE: Engineering History and Heritage, Vol.164, 1st Aug 2011, pp.163-173

www.1902encyclopedia.com

www.icevirtuallibrary.com

www.nce.co.uk