The Life and Works of John Rennie (7 June 1761 – 4 October 1821)

Boston Town Bridge

Summarised from a longer article by Ian Anderson

The first mention of a bridge at Boston was in a petition of 1305 granted to allow the levy of tolls on goods carried over and under a bridge across the River Witham.  Records of repairs are incomplete but a new pier and sluice were erected in around 1500 by Matthew Hake.

 

During the Tudor period, the condition of the bridge deteriorated and eventually it collapsed in March 1556.  A new bridge was begun in 1557 but by 1626 records show that, again, ‘the bridge was in great decay’ and repairs followed.  Eventually a new timber bridge was constructed from 1742, resting on the pier of Hake’s Sluice, which stood about two thirds the rivers’ breadth from the west side.  However, soon enough, the bridge was reported again to be in a dangerous state by 1771 and many repairs followed up to December 1799 when Boston Town Council decided to take the wooden bridge down and replace it with a new bridge of more durable materials, a little to the south of the wooden one, linking the High Street and Market Place. 

 

A committee was set up and in July 1800 John Rennie was asked for masonry and iron alternative designs.  In November he submitted outline schemes for a single arch of 76ft span ‘as flat as can conveniently be done’ to suit the site.  He estimated £6,310 for an iron bridge (£1,722 for the ironwork) and £7,206 for a masonry bridge.  The iron arch was to be one of Rowland Burdon and Thomas Wilson patent arches with a flat deck, a rise of only 5ft 6in and the ribs graduated in depth from 33 to 48ins.  The Council decided on the iron arch and applied to Parliament for an Act.

 

In Parliament on 18 March 1801 a petition was presented which explained that the bridge “is much too narrow, and , at present, in a very decayed and ruinous State and Condition … and therefore it is necessary to take down and re-build the said Bridge and also to widen, raise, and render more commodious [the approach roads] … and that the Situation of the present Bridge is very inconvenient and incommodious, and it will tend greatly to the Improvement of the Borough, if the intended Bridge was made and erected in a more proper and convenient Situation”. On 20 May John Rennie was examined to confirm the allegations of the petition. The Bill received Royal Assent on 22 June 1802. The cost of the new bridge would be £24,000 and the Act allowed the collection of tolls to continue.

 

On 9 August 1802, Rennie provided his specification for the foundations and masonry abutments, the ironwork details being left for later.  Local contractor John Watson was appointed to supervise the works under Rennie’s direction. A foundation stone laying ceremony was performed on 2 August 1804 by the Mayor, although the ironwork details for the crossing itself had still not been settled. 

 

In February 1803 Rennie was asked to increased the waterway from 72 to 80 feet, and in February 1805 he was asked to increase the span again.  Rennie was instructed to work with ‘Mr Wilson of Sunderland’, who sent his estimate “for a patent cast iron bridge over the Witham at Boston: span 85 feet and breadth 36 feet, consisting of eight ribs” to Rennie with a letter dated 15 August 1805.  Comprising 166 tons of cast iron arch blocks, stays, spandrels, pannels, balustrades, cover plates, dowels and diagonals/stays, plus 1 ton of wrought iron bolts, wedges and top-rail, the estimate was £2,980 including patent charges and erection. 

 

However, Rennie was not happy with some details, preferring an increased depth of arch ribs towards the springings.  He disliked circles in the spandrels preferring vertical struts, as well as preferring iron springing plates instead of setting the rib ends in the masonry abutments.  Rennie also wanted a flat deck, not arched, and full-depth transverse connecting frames.  Rennie did accept voussoirs of uniform depth with vertical spandrel struts, iron springing plates, bars linking upper and lower transverse connectors and a flat deck.  The last two items caused some disagreement between Wilson and Rennie. The arch blocks were 3ft 3in deep, 4in thick and 5 ½ ft long, the whole rib consisting of 17 blocks.  Although Rennie was not happy a compromise was reached on the cross frames. 

 

There was some disagreement about the abutment heights, Wilson wanting to increase them by three feet so that he could increase the rise of the arch, which had not been altered from Rennie’s 1800 design.  Rennie refused but grudgingly allowed 6 inch  additional rise.  Work began on the abutments in January 1806 and Walker’s of Rotherham cast and despatched in February the ironwork piecemeal over the next few months, with the bridge being almost complete by October. The paving of the road and footpaths occurred at the end of 1806, and it was agreed to paint the bridge an “iron colour” and open it to traffic. 

 

However, soon after, faults in the ironwork began to appear, and the opening was delayed while arguments about liability occurred.  Watson submitted his report on failings on 13 April 1807, saying that ‘there are 49 of the stays (radii) broke that connect the upper and lower circles of the ribs together, and those stays are principally broke in the second and third blocks from each abutment. There are 28 broken on the east side and 21 on the west side. The abutments are perfect.’

 

Rennie wrote on 20 April assuring the Council that the cracks were unimportant.  He stated that the radial bars connecting the upper and lower rings of the main ribs served no purpose other than to keep the rings in their proper position, and that the 49 broken ones would not affect the stability of the bridge.  “If the abutments stand good-of which I trust there is no doubt-I think there is little to fear”.  The Council accepted his advice and opened the bridge on 2nd May, but authorisation to remove the old wooden bridge was withheld until they received another reassuring letter in June.  The Committee delayed settling the Wilson’s and Walker’s accounts until Wilson had visited and made his report.  Although Rennie visited several times while he was in the area on his drainage schemes, Wilson did nor visit again until 1813.  Meanwhile the wrangle over responsibility for the problems dragged on. 

 

The Council sided with Rennie after a report from three gentlemen (5 July 1808), who agreed that the abutments had not moved.  Wilson maintained that he had been told that Rennie was in charge and he had not been allowed to make decisions on his own.  Rennie acknowledged that he had indeed made certain alterations, but that Wilson had ultimate responsibility and Walker had still not been paid in 1810. 

 

In 1811 the Council asked Rennie to consult another iron expert and on 21 September he visited with Samuel Aydon of the Shelf Ironworks, who recommended strengthening the broken radii with bolted-on cover plates and installing diagonal bracing on plan, but no action was taken. 

 

In 1813 Wilson served a writ on the Corporation to get his bill paid. In 1814 it was reported that new cracks were appearing.  Again, patching the ribs with cover plates was proposed, but no action was taken. 

 

In 1815 Rennie was asked to make one estimate for repairing the bridge and another for replacing it with a masonry arch.  On 24 April he recommended that immediate action be taken to put on cast-iron plates 1in thick by 18in wide on the circle of the arch by two bolts each end.  Pacey produced a sketch and a local founder William Howden made the plates, which were all in place by 1816.  Howden continued with occasional repairs over the next few years until 1819. 

 

Comprising a single arch span with spandrels and bindings, the bridge used 208 tons of cast iron and 3 tons 3cwt of wrought iron.  The span and width were nominally 85ft and 36ft respectively.  Telford described Rennie’s Boston troubles in his Edinburgh Encyclopedia article on bridges, estimating the main rib members as seven by four and a half inches, and the radii and spandrel struts as four by three inches.  Telford, Rennie and most engineers attributed the cracking to casting stresses in the non-uniform cross section of the rib members, although the localised cracking near the abutments shows that that this was but one of several factors. 

Despite its flaws the bridge lasted until 1913. In 1911, John J Webster, engineer of Victoria Street, London advices that a weight limit of 3 tons (2 ton axle limit) be imposed on the bridge. He was invited to design a new steel bridge, wider to include footways, to replace Rennie’s bridge. In April 1913, Rennie’s bridge was pulled down into the river by the paddle tug Privateer. During the demolition of the parapet, a coin dated 1806 was found with the inscription “T WILSON of Sunderland erected this bridge”.

 

The new Town Bridge was opened on 18 July 1913, on Rennie’s original supports.  It was Listed Grade II on 14 February 1975.   In 1964 a new bridge at The Haven, a quarter of a mile downstream, was opened as part of the Boston Inner Relief Road, turning the Town Bridge into a one-way bridge and halving its traffic. 

 

References

 

Boston Bridge Tontine-Adverts, Stamford Mercury 23 Dec 1803, p1 & 23 Mar 1804, plus

Norfolk Chronicle 24 Jul 1813 & 05 Mar 1814 

Boston Town Bridge Tontine-Death of Last Survivor, Boston Guardian, Sat 10 Dec 1904, p5

Boston Town Bridge, Condemned by Expert, New Steel Bridge Recommended, Boston Guardian, Sat 09 Dec 1911, p5

Spanning the Witham, Boston Town Bridge Closes to Traffic Tomorrow, Lincolnshire Standard, Sat 05 Apr 1913, p4

Boston Town Bridge Opening, The Bridge and its Builders: History of Boston Town Bridge, Lincolnshire Standard, Sat 19 July 1913, p6

New Inner Relief Road Planned, Work to start on new bridge, Boston Guardian, Fri 14 Aug 1964, p5

James, J G, Thomas Wilson’s Cast Iron Bridges 1800-1810, Trans. Newcomen Soc, vol 50, No.1, pp55-72 (1979)