John Rennie, mechanic, millwright, civil engineer, architect, and builder of aqueducts, bridges, canals, docks and harbours, died on the 4th of October, 1821.
In the late 18th and early 19th Centuries, if there was any civil engineering job worth doing in Britain, it’s likely that John Rennie had a hand in building it. Along with Thomas Telford and John Stevenson, Rennie was surely one of the greatest civil engineers of his era. The list of his achievements and pioneering use of materials is long and distinguished and evidence of his great works can be seen from Leith and Musselburgh in Lothian all he way down and across through England and across the Irish Sea to Dublin. Like many of his ilk, he grew up to achieve widespread fame and recognition despite having emerged from unremarkable circumstances. He rubbed shoulders with other great Scots; men like Andrew Meikle, the inventor of the thrashing machine, and James Watt, the man who improved the steam engine out of sight. From those men, he gained invaluable experience and undoubted respect and recommendation and set about carving out his own reputation as an engineer, probably without peer at the time. The quality and diversity of his endeavours was incredible and the extraordinary genius of his legacy lingers to this day around the waterways and shores of Britain. No greater accolade can be paid him than the comments of a farmer making the crossing of the new bridge at Musselburgh, which had replaced its decidedly shaky predecessor. “Brig,” answered the man in response to the query of a Magistrate in the company of Rennie, “it’s nae brig ava; ye neither ken whan ye’re on’t, nor whan ye’re aff’t.”
John Rennie was born on the 7th of June, 1761, on the Phantassie Estate near the village of East Linton in East Lothian. His father died when Rennie was five, but he was looked after by relatives and ‘gained a rudimentary education’ at the Parish School of Prestonkirk. Rennie showed a taste for mechanics at a very early age and there are stories that he played truant from school in order to spend time in the workshop of Andrew Meikle, the millwright and celebrated inventor. By the age of ten, Rennie had built working models of a windmill, a steam engine and a pile engine, and from the age of twelve, he spent less time at school and more working for Meikle at Houston Mill. He then attended the Burgh School at Dunbar and, when just sixteen, he was recommended as successor to the Schoolmaster. However, the academic life was not to John Rennie’s liking and instead, he went back to working for Meikle. He erected two or three corn mills for Rennie and by the time he was eighteen, had undertaken his first solo project; the rebuilding of the flour mills at Invergowrie. In the autumn of 1780, he began studying at Edinburgh University and between then and 1783, spent the summers working for Meikle and the rest of the year at the University. He attended the Chemistry lectures of Dr Black and the Natural Philosophy lectures of Professor Robison.
In 1783, Rennie went south with a recommendation from Robinson to James Watt, of Boulton & Watt fame, at the Soho Foundry in Smethwick. Watt gave Rennie a job and it wasn’t long before his extraordinary talents became obvious. Within a year, Rennie was in London, to take charge of the construction of two steam engines and twenty pairs of millstones at the Albion Flour Mills in Blackfriars. The work, which really established Rennie’s fame was finished in 1789, by which time he had designed many improvements to the machinery. He introduced cast iron instead of wooden wheels and also used iron for the shafting and framing. Not content with that, he increased the produce of the mills by clever use of water power, rather than simply using the impetus of the current, and was the inventor of significant advances such as the rigid bride-tree. The hitherto common practice of placing the vertical axis of the running mill stone in the middle of the bridge-tree meant that it yielded according to the quantity of grain admitted. Rennie’s invention freed the machinery from such irregular play and avoided the kind of movement that sooner or later proves fatal to any mechanism.
In about 1791, Rennie took advantage of his newly enhanced reputation and started his own mechanical and civil engineering business in Holland Street, Blackfriars. His first projects were the construction of canals and his list of achievements in the category of ‘canals’ includes: the Kennet and Avon, the Crinan Canal, the Rochdale Canal, the Lancaster Canal, the Chelmer and Blackwater Navigation, the Royal Military Canal, the Aberdeen, the Great Western, the Portsmouth, the Birmingham, and the Worcester. In 1802, he provided revised plans for the Royal Canal of Ireland and in an associated category of ‘drainage’, he came up with schemes for improving the drainage of the Lincolnshire and Norfolk fens. Rennie also gained an exemplary reputation in the category of ‘bridges’ as he was responsible for some wonderful structures. He built the Lune Aqueduct and bridges at Kelso, Leeds and at Musselburgh, the latter of which presented a remarkable innovation in the flatness of its roadway, instead of the usual rise in the centre. He proved to be a skilful architect as a look at the cast iron Southwark Bridge will testify and he was noted for building bridges with flat and wide arches and unprecedented flat roadways. Two bridges deserve special mention; London Bridge was built from his design, although it wasn’t completed until after his death, and Waterloo Bridge. The magnificent public work at Waterloo, which was completed in 1817 at a cost of over £1M, has been described as “…one of the noblest structures of the kind in the world, whether we regard the …impression of indestructibility, …or its adaptation to the useful purpose for which it was intended.”
Amongst Rennie’s other amazing achievement are his work in the category of ‘docks and harbours’ in which can be listed the docks of Leith, Queensferry, Greenock, Liverpool, Hull, Grimsby, Blackwall, and the East and West India docks, and the harbours of Holyhead, Ramsgate, Berwick, Dunleary, Howth, and Newhaven, and the naval dockyards at Sheerness, Portsmouth, Chatham and Devonport. The naval arsenal at Pembroke was also constructed from his designs, but his greatest naval work was the celebrated breakwater at Plymouth. It consisted of a wall a mile in length across the Sound, in deep water, and containing 3,670,444 tons of rough stone and 22,149 cubic yards of masonry. His inventiveness new no bounds and we can list the diving bell, which he used at Ramsgate, and the bucket-chain steam powered dredging machine, which he developed at Hull, quite independent of Sir Samuel Bentham, amongst his achievements.
John Rennie died, of inflammation in the liver, at his house in Stamford Street, London, on the 4th of October, 1821. He was buried with great funeral honours in St Paul's Cathedral. At the time of his death London Bridge was still unfinished, but the work was taken up by one of his sons, who became Sir John Rennie and President of the Institution of Civil Engineers.