# Dictionary of National Biography, 1885-1900/Rennie, John (1761-1821)

1904 Errata appended.
​RENNIE, JOHN (1761–1821), civil engineer, youngest son of James Rennie, farmer, was born at Phantassie, Haddingtonshire, on 7 June 1761. George Rennie (1749–1828) [q. v.] was an elder brother. John showed a taste for mechanics at a very early age, and was allowed to spend much time in the workshop of Andrew Meikle, millwright, the inventor of the threshing machine, who lived at Houston Mill on the Phantassie estate [see Meikle, Andrew]. After receiving a rudimentary education at the parish school of Prestonkirk, he was sent to the burgh school at Dunbar, and in November 1780 he matriculated at Edinburgh University, where he remained until 1783. He seems to have employed his vacations in working as a millwright, and so to have established a business on his own account. At this early date the originality of his mind was exhibited by the introduction of cast-iron pinions instead of wooden trundles. In 1784 he took a journey south for the purpose of enlarging his knowledge, visiting James Watt at Soho, Staffordshire. Watt offered him an engagement, which he accepted, and after a short stay at Soho he left for London in 1784 to take charge of the works at the Albion Flour Mills, Blackfriars, for which Boulton & Watt were building a steam-engine. The machinery was all designed by Rennie, and was the most perfect of its kind, a distinguishing feature being the use of iron instead of wood for the shafting and framing. About 1791 he started in business as a mechanical engineer on his own account in Holland Street, Blackfriars, whence he and his successors long conducted engineering operations of vast importance.
On settling in London Rennie began to pay attention to the construction of canals. He carried out the works in connection with the Kennet and Avon Canal, which was his first civil-engineering undertaking in England. This was followed by the Rochdale Canal, which passes through a difficult country between Rochdale and Todmorden. He subsequently constructed the Lancaster Canal, and in 1802 he revised the plans for the Royal Canal of Ireland from Dublin to the Shannon near Longford. For many years he was engaged in extensive drainage operations in the Lincolnshire fens, and in the improvement of the River Witham. The Eau Brink Cut—a new channel for the river Ouse—was on the point of completion at the time of his death.
Among the docks and harbours constructed or improved by Rennie may be mentioned the London docks, East and West India docks, Holyhead harbour, Hull docks, Ramsgate harbour, and the dockyards at Sheerness and Chatham. He devoted much time to the preparation of plans for a government dockyard at Northfleet, but they were not carried out.
Rennie also attained a deserved reputation as a builder of bridges. In the earlier part of his career he built bridges at Kelso and at Musselburgh, the latter presenting a remarkable innovation in the flatness of the roadway. Most of the bridges of any length previously constructed had a considerable rise in the centre. His later efforts show that he was a skilful architect, with a keen sense of beauty of design. Waterloo Bridge, a copy of Kelso Bridge (1810–17), London Bridge, built from his design, though not completed until 1831 after his death, and Southwark Bridge (1815–19) best attest his skill.
The Bell Rock lighthouse, near the entrance to the Friths of Forth and Tay, was built during 1807 and 1810. Rennie is usually credited with the design and execution, but there seems little doubt that he was only nominally responsible for the great undertaking. Robert Stevenson [q. v.], surveyor to the commissioners of northern lights, drew the original plans, and at his suggestion the commissioners called Rennie into counsel when the works were begun, bestowing on him the honorary title of chief engineer. Stevenson did not accept the modifications proposed by Rennie, but the two men remained on friendly terms. Rennie visited the lighthouse while it was building. ​According to Robert Louis Stevenson [q. v.], Stevenson's grandson, the board of northern lights paid Stevenson alone when the lighthouse was completed. When Stevenson died in 1850 the board put on record in its minutes that to him was ‘due the honour of conceiving and executing the Bell Rock lighthouse.’ But Rennie and his friends always claimed that the general advice which Rennie gave Stevenson entitled him to rank the building among his own achievements (see art. Stevenson, Robert ‘A Family of Engineers’ in R. L. Stevenson's Works, Edinburgh, ed. 1896, xviii. 273–4; paper by David Stevenson in Civil Engineers' and Architects' Journal, 1862).
Of all Rennie's works, that which appeals most strongly to the imagination is perhaps the breakwater at Plymouth, consisting of a wall a mile in length across the Sound, in deep water, and containing 3,670,444 tons of rough stone, besides 22,149 cubic yards of masonry on the surface. 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 Aug. following. The work was completed by his son [see Rennie, Sir John].
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 the present form of steam-dredging machine with a chain of buckets, but in this he seems to have been anticipated by Sir Samuel Bentham (cf. Mechanics' Magazine, xliii. 114, li. 126). But he was certainly the first to use it on an extensive scale, which he did during the construction of the Hull docks (1803–9), 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.
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 F.R.S. on 29 March 1798. He died, after a short illness, at his house in Stamford Street, London, on 4 Oct. 1821, and was buried in St. Paul's Cathedral. He married early in life Martha, daughter of E. Mackintosh, who predeceased him; by her he left several children, two of whom, George (1791–1866) [q. v.] and Sir John [q. v.], are separately noticed.
A portrait of Rennie from a drawing by A. Skirving, engraved by Holl, is given in Smiles's ‘Life.’ A bust by Chantrey is in the National Portrait Gallery, London; an engraving of it was made by Reynolds. An oil painting by Raeburn belonged to Mr. W. H. Rennie. A portrait by Behnes, engraved by Thompson, was published in the ‘European Magazine’ in 1821.
R. B. P.
Dictionary of National Biography, Errata (1904), p.233 N.B.— f.e. stands for from end and l.l. for last line
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