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Civil Engineering heritage: Scotland - Lowlands and Borders

Date 2007

Event ID 590600

Category Descriptive Accounts

Type Publication Account

Permalink http://canmore.org.uk/event/590600

This was a building development-led project, in this case to facilitate the extension of the New Town across the Water of Leith. This led to the creation of the last major bridge to be completed by Telford before his death. Constructed from 1829–32, it is perhaps the most majestic of all his masonry bridges, standing 106 ft above the river bed. He originally intended it as a three-span Gothic style design but, perhaps fortunately for modern taste, foundation conditions and financial constraints resulted in the plain lines of the present bridge of four spans. The bridge is 447 ft long and has four main segmental arches of 90 ft span and 30 ft rise carrying the carriageway. Alongside them, carrying the footpaths, are ascititious or external arches of 96 ft span and 10 ft rise springing from pilasters only 5 ft wide, the formation of which was a particularly delicate and unprecedented operation. As can be seen from the view, this feature gives the elevation an appearance of slenderness which seems almost incredible for a masonry bridge.

The carriageway is 23 ft wide and the footways 8 ft. The bridge is of hollow spandrel construction with tie-stones between the longitudinal walls. In 1972, under the writer’s 153direction, the 5 ft depth of fill above the main arch was investigated and it was found that a layer of broken freestone had been substituted, probably at the outset, for Telford’s traditional hand-pitched stone pavement, overlain with a 4 in. clay layer and 6 in. of weak lime concrete to prevent water penetration. Above this was mainly whinstone Macadam.

The contractor was John Gibb of Aberdeen and the cost was £18 556 exclusive of the approach roads. He is reputed to have finished the bridge ahead of time, but declined to hand it over to his building speculator client John Learmonth and the Cramond District Road Trust. Instead he is said to have opened the bridge and charged a toll until the completion date! Since then the bridge has required minimal maintenance and it now carries several million vehicles each year without any weight restriction.

R Paxton and J Shipway 2007

Reproduced from 'Civil Engineering heritage: Scotland - Lowlands and Borders' with kind permission of Thomas Telford Publishers.

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