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

Early years

John Rennie was born near Phantassie in Haddingtonshire, which is now known as East Lothian. He was the youngest child of James Rennie, a farmer and brewer. He studied at the parish school in Prestonkirk. He showed an early interest in machines and caught the attention of Andrew Meikle, a millwright and inventor of the threshing machine, who lived on the Phantassie estate. At twelve years old, Rennie began working for Meikle, receiving basic training in practical mechanics. From 1775 to 1777, he attended high school in Dunbar. In 1779, with Meikle’s support, Rennie started his own business as a millwright. One of his first projects was building a mill for his oldest brother, George Rennie. From 1780 to 1783, while continuing his work as a millwright, he studied at the University of Edinburgh.

In 1783, Rennie traveled through England, studying canals, bridges, and machinery along the way. In Birmingham, he met James Watt, who hired him as a millwright at Watt’s Soho works. This began a long working relationship between Watt and Rennie that lasted until Watt’s death in 1819.

In 1784, after a short time at Soho works, Rennie moved to London, where he managed the machinery that Boulton & Watt were supplying to the Albion Mills. A notable feature of the machinery was that the wheels and shafts were made of iron instead of wood. Rennie’s position allowed him to take on work for other clients, leading to commissions for flour mills, breweries, distilleries, and later, sugar mills.

In 1791, the Albion Mills were destroyed by fire. However, by this time, Rennie’s business was already well established. He provided machinery for mills, breweries, and factories in Britain and abroad, working from workshops he built on part of the Albion site. In 1810, these workshops were expanded into neighboring Holland Street.

Canals and waterways

Rennie's business grew into civil engineering, focusing on building canals and other structures. He worked on several projects early in his career, including the Stowmarket Navigation (River Gipping) in 1791, the Lancaster Canal (started in 1792), the Chelmer and Blackwater Navigation in 1793, the Crinan Canal (1794–1801), Rudyard Lake in 1797, and the Rochdale Canal, which runs through challenging terrain between Rochdale and Todmorden (1799). He also worked on the Kennet and Avon Canal, which includes the Dundas Aqueduct, Caen Hill Locks, and Crofton Pumping Station, from 1794 to 1810.

In 1802, he revised the plans for the Royal Canal of Ireland, which connects Dublin to the Shannon near Longford. He also advised the Dublin Corporation's Pipe Water Committee and was honored with the Freedom of the City of Dublin in 1804.

For many years, he focused on large-scale drainage projects in the Lincolnshire and Norfolk Fens (1802–1810) and improved the River Witham. The Eau Brink Cut, a new channel for the River Ouse, was completed shortly before his death. He also served as chief engineer for the canal and a major but unsuccessful lazaret at Chetney Hill, located on the River Medway estuary in Kent.

Bridges

Over the next few years, Rennie gained a well-deserved reputation as a builder of bridges, using stone and new cast-iron methods to create low, wide, oval-shaped arches that had never been built before. The first Waterloo Bridge (then called the Strand Bridge), which crosses the River Thames in London (1811–1817), had nine equal arches and a flat roadway. This bridge is believed to have been influenced by Thomas Harrison’s design of Skerton Bridge over the River Lune in Lancaster. In Leeds, Rennie was asked to build two stone bridges: one over the River Aire and another smaller bridge over the Leeds & Liverpool Canal, located on the west side of the town center and upstream from Leeds Bridge. The main person behind this project was Benjamin Gott, a mill owner who owned land on both sides of the waterways and wanted a better path between them. The larger bridge was described as "a beautiful structure, consisting of an elliptical arch with a span of one hundred feet." This bridge was first called Waterloo Bridge but was later renamed Wellington Bridge. Rennie’s later work shows he was a skilled architect with a strong sense of design. Waterloo Bridge was considered his greatest achievement and the most important bridge project in England at the time. It was described as "perhaps the finest large masonry bridge ever built in this or any other country." The Italian sculptor Canova called it "the noblest bridge in the world" and said, "it is worth going to England solely to see Rennie’s bridge." After Rennie’s death, London Bridge was built using his design by his sons, John Rennie (junior) and George Rennie. This new bridge replaced the old medieval bridge, which had become a major problem for the river’s flow. Rennie’s bridge was later moved to Arizona. Southwark Bridge (1815–1819) was built with three cast-iron sections over the river. He also designed the Old Vauxhall Bridge.

Docks and harbours

John Rennie was also responsible for designing and building docks in Hull, Liverpool, Greenock, London (including London, East India, and West India docks), and Leith. He also improved the harbors and dockyards at Chatham, Devonport, Portsmouth, Holyhead, Ramsgate, Sheerness, Howth, and Dunleary. He spent a lot of time preparing plans for a government dockyard at Northfleet, but the plans were not completed.

Dunleary Harbour, also known as "Asylum," was a very important and difficult project because it was essential to keep communication between Ireland and London, where the government was located. Rennie had previously built Howth Harbour on the north side of Dublin Bay a decade earlier. Howth Harbour was originally planned as the landing point for ships carrying mail between Holyhead and London, but it filled with sand and became unusable. An Act of Parliament in 1816 (56 Geo. 3. c. 62) approved the construction of Dunleary Harbour. Initially, only one pier (the East Pier, 3,500 feet long) was planned. However, when Rennie became the chief engineer, he argued that a single pier would cause sand to build up behind it. He insisted on building a second pier (the West Pier, 4,950 feet long) to stop this from happening. His prediction was correct, as sand did accumulate behind the West Pier. After completion, the harbor was renamed "The Royal Harbour of Kingstown" in 1821 during the visit of King George IV. The harbor was built using Dalkey Hill granite, donated by Richard Toucher, who had long supported the project. The piers’ foundations are 300 feet wide and 24 feet below the low water level. Rennie suggested the space between the two piers should be 430 feet wide, with the piers angled inward to control waves inside the harbor. However, the opening was built at 1,066 feet wide, which was later reduced to 760 feet.

One of Rennie’s final projects was the construction of the Custom House Docks in Dublin, including its locks, warehouses, and the CHQ Building, where he first used cast-iron in the early 1800s. He was first invited to work on the project in 1809 by John Foster, the Irish Chancellor of the Exchequer. The first stone of the docks was laid in May 1817, and the docks officially opened in late August 1821 in front of a group of noblemen, bishops, and other important people. In 1824, the docks were leased to Harry and John Scovell and their nephew George. Harry and John were the younger brothers of Sir George Scovell, an intelligence officer known for breaking French secret codes during the Napoleonic Wars.

By March 1820, Rennie requested 33 tons of structural cast-iron and a large amount of wrought iron to build a "Tobacco Warehouse, with the Spirit Stores under it." The iron was supplied by the Butterley Iron Company from Derbyshire. However, an obituary from 1841 mentioned that William Hazeldine, an engineer from Shropshire, also provided the iron roofs for the Dublin Custom House and warehouses. In 1821, John James Macgregor noted that the tobacco stores on the south side cost £70,000 to build. They are 500 feet long and 160 feet wide, with a cast-iron roof and a strong, long-lasting structure. In 1821, the Rev. George Newenham Wright, an Anglican clergyman, also wrote about the completed tobacco store.

Now known as the CHQ Building, the former tobacco store is now home to businesses such as EPIC – The Irish Emigration Museum and Dogpatch Laboratories.

Donaghadee is best known for its lighthouse and harbor. For centuries, the harbor has been a safe place for ships, and it has existed since at least the 17th century.

Sir Hugh Montgomery built a large stone quay to help ships travel between Scotland and Ireland starting in 1616. Viscount Montgomery’s harbor, completed in 1626 and improved in 1640, replaced a smaller jetty. The Royal Warrant of 1616 limited travel between the Ards and the Rhins of Galloway to this port and another at Portpatrick, both owned by Montgomery. In 1744, Harris described the quay as "a curving quay about 400 feet long and 22 feet wide, built of uncemented stones." It ran from the shore at the north end of the Parade in a wide arc toward the southern end of the present north pier. By the late 18th century, the quay was in poor condition and was rebuilt between 1775 and 1785 by the landlord, Daniel Delacherois, likely with help from John Smeaton, a respected civil engineer who had previously planned improvements to the harbor and rebuilt Portpatrick Harbor. The old quay remained until the new harbor was completed, after which it was removed in 1833 for use in local construction projects.

The foundation stone of the new harbor was laid by the Marquess of Downshire on August 1, 1821. John Rennie made the initial plans and surveys for the project, but he died two months after work began. His son, John Rennie, took over and worked with David Logan, a Scottish engineer who had previously assisted Robert

Bell Rock Lighthouse and Holyhead Mail Pier Lighthouse

The Bell Rock Lighthouse, located near the entrance to the Firths of Forth and Tay, was constructed between 1807 and 1810. Some people credited Rennie with designing and overseeing the project, but it is likely he was not fully responsible. Robert Stevenson, a surveyor for the Commissioners of Northern Lights, created the original plans. At his suggestion, the commissioners asked Rennie to help gain approval for the project, giving him the title of chief engineer. However, Rennie was only paid £400 for this role. Stevenson did not adopt many of Rennie’s proposed changes, but the two men remained on good terms. Rennie visited the lighthouse twice during its construction. After Stevenson died in 1850, the commissioners officially acknowledged that he was responsible for conceiving and building the Bell Rock Lighthouse. However, Rennie’s son, Sir John Rennie, later claimed in letters with Alan Stevenson in 1849 that Rennie’s advice gave him the right to be considered the designer and constructor of the lighthouse.

The Holyhead Mail Pier Light is a white, cone-shaped structure built by Rennie in 1821. It is a nationally significant example of Rennie’s surviving work. In Wales, the lighthouse is notable for its early use of gas lighting in the lantern. Before switching to electricity, a gas works on the island powered the lighthouse, nearby piers, and part of Holyhead itself. The gas works cost £130,000 to build, a very large amount of money at the time. The tower remains intact and features curved gallery railings similar to those at Bardsey Lighthouse. The lighthouse is no longer active but is still used as a reference point for sailors.

The Howth Harbour Lighthouse is a matching tower in Howth, Ireland, designed by Rennie for the other terminal of the Irish packet steamer.

Plymouth breakwater

Of all Rennie's works, the breakwater at Plymouth Sound is the most imaginative. It is a wall that is one mile long, built across the Sound in about 20 meters (66 feet) of water. The wall contains 3,670,444 tons of rough stone, as well as 22,149 cubic yards (16,934 cubic meters) of masonry on the surface. This structure was built to help naval vessels safely enter the river Tamar (Hamoaze) at Devonport. The idea for this large project was first suggested in a report by Rennie dated April 22, 1806. An official order to begin the work was given on June 22, 1811, and the first stone was placed on August 12, 1812. The project was finished by Rennie's son, Sir John Rennie, and by Joseph Whidbey.

Technical innovator

Rennie was a man with great creativity and problem-solving skills. While working on improving Ramsgate Harbour, he used and improved a tool called a diving-bell. He is often credited with creating a type of steam-powered dredging machine that used a chain of buckets. However, evidence suggests that Sir Samuel Bentham had already invented a similar machine. Rennie was the first to use this type of machine on a large scale during the construction of the Humber Dock in Hull from 1803 to 1809. He designed a steam dredger to solve challenges during this project, apparently without knowing about Bentham's earlier work. Another method he used was hollow walls, which were needed to provide a wide base for walls built on soft ground. Rennie frequently used walls built with this design.

Distinguishing characteristics

Rennie's work was known for being strong and solid, and it has lasted a long time. He was very careful when preparing his reports and estimates, and he always learned everything about the local area before starting a project. He was dedicated to his job, and even though he had a strong body and could work hard for a long time, his constant work made him die earlier than expected. He was chosen as a Fellow of the Royal Society of Edinburgh on January 28, 1788, and as a Fellow of the Royal Society on March 29, 1798. In 1815, he worked as a Manager of the newly built London Institution.

Family and death

In 1790, he married Martha Ann Mackintosh (died in 1806), the daughter of E. Mackintosh. They had seven children, two of whom, George and John, became well-known engineers. His daughter, Anna, married the architect Charles Cockerell.

He died after a short illness at his home on Stamford Street in London on October 4, 1821. He was buried in the crypt of St. Paul's Cathedral.

Honours

• In 1862, a small area of land south of Blackfriars Bridge was set aside as an open space by the City of London Corporation to honor John Rennie.
• In 2014, John Rennie was added to the Scottish Engineering Hall of Fame.
• The Ruislip Lido Railway, which is located at Ruislip Lido (one of the dams John Rennie built), named one of its locomotives after him. The Bo-Bo type diesel locomotive called "John Rennie" was built in 2004 and is one of the main engines used on the railway line.
• More recently, Lancaster Royal Grammar School Boat Club named one of their boats after John Rennie because he constructed the aqueduct over the river where they row.

List of projects

• Lune Aqueduct (1794–1797)
• Dundas Aqueduct (1797)
• Kelso Bridge, with five arches (1800–1804)
• Boston Bridge, a cast iron arch (1800)
• London Docks (1800–1805)
• East India Docks, a joint project with Ralph Walker (1803–1806)
• Humber Dock, Hull (1803–1809), cost £230,000
• Greenock Docks (1806)
• Musselburgh Bridge (1806–1808)
• West India Docks, extension to docks (consultant to William Jessop) (1809–1821)
• Liverpool Docks, two new docks including Prince’s, estimated cost £929,878 (1809)
• Waterloo Bridge (old), granite with nine arches, each 120 feet wide (1810–1817), cost £1,050,000
• New Galloway Ken Bridge, of granite (1811–1821), spans the River Ken
• Cree Bridge at Newton Stewart (1812–1814)
• Old Wye Bridge, Chepstow, cast iron bridge (design 1812), redesigned and built in 1816 by John Urpeth Rastrick
• Plymouth Breakwater (1812–1841), completed by his son
• Southwark Bridge (old), of three cast iron arches (1814), replaced in 1920
• Dunleary Asylum Harbour – later Kingstown Harbour – later Dún Laoghaire Harbour (1816–1842), completed by his son, cost £690,717 against the original estimate of £801,059
• Donaghadee & Portpatrick Harbours (1819), estimated cost £145,000
• Leeds Bridge, cast iron design (1820), built after his death by the resident engineer G. Leather
• Dublin Docks, 'Stack A' bonded warehouse; introduces lightning conductors, gas works, and gas lighting (1820)
• London Bridge (old), designed 1820, built after his death by his son (1824–1831), moved to Lake Havasu City in the USA
• Royal Observatory, Cape of Good Hope Main Building, completed posthumously in 1828
• Blackwall Dock
• Ruislip Reservoir, Grand Union Canal
• Deeping Fen Drainage and pumping engines at Pode Hole (incomplete at his death)
• Caen Hill Locks, a flight of locks on the Kennet and Avon Canal, between Rowde and Devizes in Wiltshire, England, comprising 29 locks.