John Rennie the Elder

John Rennie FRSE FRS (7 June 1761 – 4 October 1821) was a Scottish civil engineer who designed many bridges, canals, docks and warehouses, and a pioneer in the use of structural cast-iron.

He showed an interest in machinery from an early age, and came to the attention of Andrew Meikle, a millwright and the inventor of the threshing machine, who lived on the Phantassie estate.

[1][3] In 1784, after a short stay at the Soho works, he left for London, where he was put in charge of the machinery that Boulton & Watt were supplying to the Albion Mills.

He was supplying machinery for mills, breweries, and factories of all kinds both in Britain and abroad, working from workshops that he had built on part of the Albion site.

The Kennet and Avon Canal – including the Dundas Aqueduct, Caen Hill Locks and Crofton Pumping Station – occupied him between 1794 and 1810.

For many years he was engaged in extensive drainage operations in the Lincolnshire and Norfolk Fens (1802–1810), and in the improvement of the River Witham.

[6] He was also chief engineer for the canal and major, but abortive lazaret at Chetney Hill, on the River Medway estuary in Kent.

[7] Over the next few years Rennie also attained a deserved reputation as a builder of bridges, combining stone with new cast-iron techniques to create previously unheard-of low, wide, elliptical arches.

The main instigator of this scheme was mill owner Benjamin Gott, who had properties on both sides of the waterways and wanted an easier route between them.

Rennie's later efforts in this line also show that he was a skilful architect, endowed with a keen sense of beauty of design.

Rennie was also responsible for designing and building docks at Hull, Liverpool, Greenock, London (London, East India and West India docks), and Leith and improving the harbours and dockyards at Chatham, Devonport, Portsmouth, Holyhead, Ramsgate, Sheerness, Howth and Dunleary.

Dunleary harbour of 'Asylum' was a very difficult and important project, because it was critical to maintain an effective communication link between Ireland and London, the seat of government.

Rennie was responsible for the construction of Howth Harbour on the North side of Dublin bay a decade earlier.

One of John Rennie's last projects was the construction of the Custom House Docks in Dublin, along with its locks and warehouses, including the CHQ Building where he pioneered the use of cast-iron in the early 19th century.

Harry and John were the younger brothers of Sir George Scovell, the intelligence officer famed for cracking Bonaparte's secret codes during the Napoleonic Wars.

By March 1820, Rennie was seeking 33 tons of structural cast-iron, along with a large quantity of wrought iron, for the purpose of building a "Tobacco Warehouse, with the Spirit Stores under it.

George Newenham Wright, an Anglican clergyman, likewise noted: Now known as the CHQ Building, the tobacco store is home to various enterprises including EPIC – The Irish Emigration Museum and Dogpatch Laboratories.

Sir Hugh Montgomery built a large stone quay to accommodate vessels ferrying between Scotland and Ireland from 1616 onwards.

He, however, died within two months of work beginning, and was succeeded by his son, John, who had as his resident engineer a fellow Scot, the seasoned marine builder, David Logan, who had assisted Robert Stevenson at the Bell Rock Lighthouse (1807–1810).

When Stevenson died in 1850, the Commissioners put on record in their minutes that to him was 'due the honour of conceiving and executing the Bell Rock lighthouse'.

This colossal work was first proposed in a report by Rennie, dated 22 April 1806; an order in council authorising its commencement was issued on 22 June 1811, and the first stone was deposited on 12 August following.

He is generally credited with the invention of a form of steam-dredging machine with a chain of buckets, but in this he seems to have been anticipated by Sir Samuel Bentham.

He was certainly the first to use it on an extensive scale, which he did during the construction of the Humber Dock, Hull (1803–09), when he devised a steam dredger to overcome the difficulties of that particular work, and apparently without any knowledge of Bentham's invention.

He was devoted to his profession, and, though he was a man of strong frame and capable of great endurance, his incessant labours shortened his life.

[1] He died, after a short illness, at his house in Stamford Street, London, on 4 October 1821, and was buried in the crypt at St. Paul's Cathedral.