Boston Iron Footbridges
in Boston, Lincolnshire
John Rennie designed four cast iron bridges for Boston. The Town Bridge, built in 1803, carried the main street across the River Witham. The design was partly due to Thomas Wilson (1751-1820) who had played a major part in the construction of the Wearmouth Bridge at Sunderland, who ordered the ironwork from Walker's without gaining Rennie's approval. The resultant cracks in the ironwork led to arguments that continued for many years[1]. This bridge was demolished in 1913.
Three smaller cast iron footbridges crossed the Maud Foster Drain. Two have survived - Cowbridge bridge and Hospital Bridge Lane bridge - while the third, Vauxhall Bridge, (which may have been designed by William Jessop) was demolished in 1924 and replaced by a road bridge.[2]. The bridges are remarkably slender and elegant, and were cast by the Butterley Co in 1811. The arch ribs are curved in plan, being about half as wide at mid span as at the ends.
Cowbridge bridge, constructed in 1811, has a span of 61 ft with a rise of just 4 ft.
Geograph entry for Cowbridge footbridge here, and for Hospital Lane footbridge here.
See here for Heritage Gateway entry for Hospital Bridge Lane Footbridge, Boston. This states that the bridge is 67ft 9" long, 8ft wide at each end and narrows to 4ft 6" in the centre. The arch rises by a maximum of 2 ft 6" at mid span. The bridge is still in its original condition except for the footway resurfacing.
Aspects of construction: Each arch rib is assembled from two iron castings, joined at mid-span, where a transverse plate is sandwiched (see photo 5).
The outboard ends of the ribs are sprung from cast iron plates on the sloping masonry abutment.
The ribs have a flange at the top, which can just be made out in photo 4, and slightly more clearly in photo 5. Photo 4 also shows wrought iron diagonal bracing rods. The bottom of the ribs has a token flange on the outer face, but it is not clear whether the inner face is the same.
The wrought iron railings are embedded in a series of iron castings which are somehow fixed to the main ribs.