Publication Account

Date 1993

Event ID 589753

Category Descriptive Accounts

Type Publication Account

Permalink http://canmore.org.uk/event/589753

This bridge, made of cast iron and straddling the Braid Burn, was constructed, erected and painted in March 1831 by the Shotts Iron Company. It cost £133.10s.0d. There is considerable historical and technological interest in the cast iron beams as they furnish the earliest extant examples in the world of their particular type.

A survey undertaken on 5 and 6 September 1992 by the Scottish Industrial Heritage Society shows that the bridge possesses three major beams and a minor beam on the upstream side. It is probable that the central section of the existing arrangement is made from wooden sleepers belonging to the railway. As regards the outer sections, which are now part of the footpath/cycleway, these may be replacements for a former deck. It would seem from the way the abutments on the downstream side of the bridge are arranged that there was a double track line before 1847. As the lugs for the tie bolts are 'eccentric to each other', it is obvious that the rails have been shifted and re-aligned. The reason for this is probably the guage change and reduction to single track which occurred in 1847. There is only a single track shown crossing the bridge in the 25 inch OS map of 1893 (Edinburghshire sheet III.12).

Generally speaking there are uniform sized flanges on the main inverted T-section beams, with the top flange having a longitudinally convex shape. The equi-spaced braces taper from top to bottom, being noticeably wider at the top. It is difficult to measure the overall length of the upstream L-section beam as its ends are embedded in the abutments. However, the exposed section gives a clear picture of an upper edge which is also longitudinally convex, and 'formed by a three-centred arch.' The ends of this L-section beam are probably rounded, whereas the main beams have square ends.

G Douglas, A Jervis, M McDonald, N Niblock and W Barr 1993.