alt=Portrait of male with white hair wearing a white cravat and blue jacket.|thumb|right|Portrait of John Rennie, 1810, by Sir [[Henry Raeburn]]

thumb|285px|John Rennie's signature

John Rennie (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.

Early years

thumb|Portrait on the John Rennie Memorial at [[Phantassie, East Linton]]

John Rennie was born near Phantassie in Haddingtonshire (present day East Lothian). He was the youngest son of James Rennie, a farmer and brewer. He attended the parish school at Prestonkirk. 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. At the age of twelve, Rennie started to work for Meikle, getting a grounding in practical mechanics. From 1775 to 1777, he attended high school in Dunbar. In 1779, with the support and approval of Meikle, he set up in business on his own account as a millwright. One of his first jobs was to construct a mill for his oldest brother, George Rennie. From 1780 to 1783, while still working as a millwright, he attended the University of Edinburgh.

In 1783 he undertook a journey through England, studying the canals, bridges, and machinery that he encountered on the way. In Birmingham, he visited James Watt, who employed him as a millwright at his Soho works. This was the start of an association between Watt and Rennie which would last until Watt's death in 1819.

In 1791, the Albion Mills were destroyed by fire. But by then Rennie's business was well established. 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. In 1810 these were extended into neighbouring Holland Street. He was also chief engineer for the canal and major, but abortive lazaret at Chetney Hill, on the River Medway estuary in Kent.

Bridges

thumb|upright=1.25|The opening of the first [[Waterloo Bridge on 18 June 1817]]

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 first Waterloo Bridge (then known as the Strand Bridge), over the River Thames in London (1811–1817), with its nine equal arches and perfectly flat roadway, is thought to have been influenced by Thomas Harrison's design of Skerton Bridge over the River Lune in Lancaster. In Leeds he was commissioned to build two stone bridges, one over the River Aire and a second smaller structure over the Leeds & Liverpool Canal, to the west side of the town centre and upstream from Leeds Bridge. 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. The larger bridge was described as 'a beautiful structure, consisting of an elliptical arch of one hundred feet span'. The bridge, initially known as Waterloo Bridge, was soon renamed Wellington Bridge. Rennie's later efforts in this line also show that he was a skilful architect, endowed with a keen sense of beauty of design. Waterloo Bridge was considered his masterpiece and was the most prestigious bridge project in England, 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 that 'it is worth going to England solely

to see Rennie's bridge.' After Rennie's death, London Bridge was built from his design by his sons John Rennie (junior) and George Rennie. It replaced the medieval bridge which was proving a serious impediment to the flow of the river. Rennie's bridge was eventually moved to Arizona. Southwark Bridge (1815–1819) was built as three cast-iron spans over the river. He also designed the Old Vauxhall Bridge.

Docks and harbours

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. He devoted much time to the preparation of plans for a government dockyard at Northfleet, but they were not carried out.

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. This was originally planned as the landing for the Holyhead packets, but it silted up to such an extent that it became unfit for purpose. An Act of Parliament of 1816 (56 Geo. 3. c. 62) authorised the building of Dunleary harbour. Originally it was intended that only one pier (the East Pier) would be built (3,500 feet long), but when John Rennie was appointed directing engineer for the work, he insisted that a single pier would result in sand drifting behind the pier and that a second West Pier (4,950 feet long) would prevent this from occurring. He was correct as the sand has built up behind the west pier. The harbour once built was renamed 'The Royal Harbour of Kingstown' in 1821 on the occasion of the visit of George IV. The material for the harbour is Dalkey Hill granite. The granite was provided by Richard Toucher (a long time campaigner for the new harbour) at no cost to the construction team. The foundations of the piers are 300'-0" wide and 24'-0" below low water level. Many options were considered for the width of the space between the two pier heads. Rennie wrote to the Harbour Commissioners that the opening should be 430'-0" wide with the pier heads turned into the harbour to control swells within the harbour. His demands were never met and the harbour opening was built at 1,066'-0". This was clearly too wide and was subsequently reduced to 760'-0".

Custom House Docks and the CHQ Building, Dublin

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. Rennie was first invited to work on the scheme in 1809 by John Foster, the Irish Chancellor of the Exchequer. The first stone of the docks was laid in May 1817; they were formerly opened at the end of August 1821 in front of 'a most select company of Noblemen, Bishops, Ladies, &c.' In 1824 the docks were placed on a long-term lease to Harry and John Scovell, and their nephew George. 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." The iron was supplied by the Butterley Iron Company from Derbyshire. However, an obituary of Shropshire-born engineer and iron founder William Hazeldine from 1841 claimed that Hazeldine also supplied 'the Iron Roofs for the Dublin Custom House and Store Houses.' In 1821, John James Macgregor noted: 'The tobacco stores have been finished on the south side at the expense of £70,000. They are 500 feet long by 160 feet wide. The roof is of cast iron, and the building finished in the most permanent manner.' In 1821, the Rev. George Newenham Wright, an Anglican clergyman, likewise noted:

:To the east of the new basin is the tobacco store (500 feet by 160, and capable of containing 3,000 hogsheads), the plan of which was given by John Rennie, Esq. In this store, which is now completed and in use, there is not one particle of wood or other combustible matter. There are nine vaults beneath, which altogether afford perfect and convenient storage for 4,500 pipes of wine, allowing a walk behind the heads of the pipes as well as between them; these vaults are lighted by means of thick lenses set in iron plates in the floor of the tobacco store; but this is not sufficient to supersede the necessity of candle light. The interior of the tobacco store is extremely curious and interesting: the roof is supported by metal frame-work of an ingenious construction, and, at intervals, long lanterns are inserted, the sashes of which are also metal; the entire frame-work is supported by three rows of cylindrical metal pillars, 26 in each row; these rest upon others of granite, which are continued through the stone floor into the vaults beneath. All the iron-work was manufactured at the Butterley foundry in Derbyshire. The only inconvenience at present felt in this store is the excessive heat, which, in all probability, can be remedied by a proper system of ventilation. Stevenson did not accept many of the modifications proposed by Rennie, but the two men remained on friendly terms. Rennie visited the lighthouse twice while it was being built. 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'. However, Rennie's son, Sir John Rennie, claimed in a long exchange of letters with Alan Stevenson in 1849 that the advice which Rennie gave Stevenson entitled him to rank the building as one which he "designed and constructed".

thumb|Holyhead Mail Pier Light

The Holyhead Mail Pier Light is a conical white house which was built by Rennie in 1821. The lighthouse is of national significance as one of Rennie's surviving works. Of particular importance, in a Welsh context, is the early date of the lighthouse lantern, which was originally lit by gas. Before the conversion to electricity a gas works was located on the island to power the lighthouse, the piers and even part of Holyhead itself. The works were constructed at a cost of £130,000, an astronomical sum at the time. The tower survives intact and has beautifully curving gallery railings, similar to those at Bardsey Lighthouse. It is no longer in use, although it is used as a navigation reference for sailors.

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

Plymouth breakwater

thumb|Plymouth breakwater, viewed from above Kingsand

Of all Rennie's works, that which appeals most strongly to the imagination is perhaps the breakwater at Plymouth Sound, consisting of a wall a mile in length across the Sound, in about of water, and containing 3,670,444 tons of rough stone, besides of masonry on the surface. It was constructed to provide safe passage for naval vessels entering the river Tamar (Hamoaze) at Devonport. 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. The work was completed by his son, Sir John Rennie, and by Joseph Whidbey.

Technical innovator

Rennie was a man of unbounded resource and originality. During the improvement of Ramsgate harbour he made use of the diving-bell, which he greatly improved. 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. Another expedient was the use of hollow walls, which was suggested by the necessity of providing an extensive bearing surface for the foundations of a wall in loose ground. Walls built upon this plan were largely used by Rennie.

Distinguishing characteristics

The distinguishing characteristics of Rennie's work were firmness and solidity, and it has stood the test of time. He was most conscientious in the preparation of his reports and estimates, and he never entered upon an undertaking without making himself fully acquainted with the local surroundings. 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. He was elected Fellow of the Royal Society of Edinburgh on 28 January 1788, Fellow of the Royal Society on 29 March 1798, and in 1815 he served as a Manager of the newly built London Institution.

Family and death

In 1790 he married Martha Ann Mackintosh (d.1806), daughter of E. Mackintosh, and by her had seven children, two of whom, George and John, became notable engineers. His daughter Anna married the architect Charles Cockerell.

Honours

  • In 1862 a small parcel of the land south of Blackfriars Bridge was designated as an open space to memorialise John Rennie by the City of London Corporation.
  • In 2014 he was inducted into the Scottish Engineering Hall of Fame.
  • The Ruislip Lido Railway, based at Ruislip Lido (one of the dams John Rennie built), named one of its locomotives after him. The Bo-Bo type diesel 'John Rennie' was built in 2004 and is one of the main engines of the line.
  • More recently, Lancaster Royal Grammar School Boat Club named one of their boats after him as he built the aqueduct over the river on which they row.

List of projects

  • Lune Aqueduct (1794–97)
  • Dundas Aqueduct (1797)
  • Kelso Bridge, of five arches (1800–1804)
  • Boston bridge, a cast iron arch (1800)
  • London Docks (1800–05)
  • East India Docks joint project with Ralph Walker (1803–06)
  • Humber Dock, Hull, 1803–9, cost £230,000
  • Greenock Docks (1806)
  • Musselburgh bridge (1806–1808)
  • West India Docks (consultant to William Jessop) extension to docks (1809–1821)
  • Liverpool Docks, two new docks including Prince's, estimated cost £929,878 (1809)
  • Waterloo Bridge (old), granite of nine arches each 120 feet wide (1810–17) cost £1,050,000
  • New Galloway Ken Bridge, of granite (1811–21) spans the River Ken.
  • Cree Bridge at Newton Stewart (1812–14)
  • 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 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 designed (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 (1824–31) 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)