John Rennie (1761–1821)
John Rennie was a leading millwright and one of the most prolific British engineers of docks and waterways in the Industrial Revolution. As either designer or consulting engineer he reported on over 200 projects.
Rennie grew up east of Edinburgh, where his father was a farmer and brewer. He was educated at the local elementary school but became a protégé of the millwright and inventor Andrew Meikle (1719-1811) and aged 12 went to work as Meikle’s assistant. Later, he attended high school and then, at the age of 18, set up his own practice as a millwright while studying at Edinburgh University. After graduating he went on a study tour of England, during which he visited the Boulton and Watt factory in Birmingham. James Watt spotted his exceptional talent and offered him a job. Rennie installed the Boulton and Watt steam engines for the innovative Albion Flour Mills in London, built rolling mills for the Royal Mint and devised machinery for flour mills, textile factories, breweries and other steam-powered industries. In 1810 he built a new factory at Southwark, London, for his mechanical projects. He began supplying customers in Spain, France and Portugal. Among his innovations he pioneered the use of ball-bearings and the gantry crane.
Nevertheless, it was as a civil engineer that Rennie became famous. This strand of his career began in 1790 when he was appointed surveyor to the proposed Kennet and Avon Canal, which was to link London with Bristol by a new waterway some 90 km long. Numerous canal projects followed, including the Rochdale and Lancaster canals in north-west England, the Aberdeen and Crinan canals in Scotland and the Royal Canal of Ireland. His maritime projects included commercial docks and harbours in London, Dublin, Liverpool, Hull and Glasgow and the Royal Navy dockyard at Woolwich. He also designed the stone breakwater at Plymouth, which extended for 1.6-km in waters up to 20 m deep, and devised with Robert Stevenson the Bell Rock lighthouse on the east of Scotland, built in 1807-10. He pioneered steam-powered dredging and pile-driving and the use of diving bells.
Rennie’s projects most visible to the public were his multi-span road bridges, including three over the Thames in central London. Waterloo Bridge of 1811-17 was considered one of the masterpieces of masonry bridge construction. Southwark Bridge of 1814-19 had the widest cast-iron span ever built in Britain; Rennie sent an even larger one in sections to be erected at Lucknow, India. He was made a Fellow of the Royal Society but turned down a knighthood. His sons George and John continued the practice after his death.