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  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. ‘A Family of Engineers’ in  Works, Edinburgh, ed. 1896, xviii. 273–4; paper by  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 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.

[Smiles's Lives of the Engineers: Smeaton and Rennie. Sir John Rennie's Autobiography contains much information concerning his father's works, but no professional life of Rennie has ever been published, although his son intended to undertake such a work. Baron Dupin's Notice Nécrologique sur John Rennie, London, 1821; Baron Dupin's Public Works and National Improvements of the British Empire, London, 1830; European Mag. (with portrait) November 1821. A complete collection of his printed reports is in the library of the Institution of Civil Engineers.]

 RENNIE, JOHN (1794–1874), civil engineer, second son of John Rennie [q. v.], and brother of George Rennie (1791–1866) [q. v.], was born at 27 Stamford Street, Blackfriars Road, London, on 30 Aug. 1794. He was educated by Dr. Greenlaw at Isleworth, and afterwards by Dr. Charles Burney at Greenwich. He subsequently entered his father's manufactory in Holland Street, Blackfriars Road, where he acquired a practical knowledge of his profession, and in 1813 he was placed under Mr. Hollingsworth, resident engineer of Waterloo Bridge, the foundations of which he personally superintended. In 1815 he assisted his father in the erection of Southwark Bridge, and in 1819 he went abroad for the purpose of studying the great engineering works on the continent. On the death of his father in 1821 he remained in partnership with his brother George, the civil engineering portion of the business being carried on by him. The most important of his undertakings was the construction of London Bridge, the designs for which had been prepared by his father. The bridge was opened in 1831, when Rennie was knighted, being the first of the profession since Sir Hugh Myddleton to be thus distinguished. As engineer to the admiralty,