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Civil Engineering heritage: Scotland - Lowlands and Borders

The impressive entrance lock of 1806 to the East and West Docks is 145 ft long by 34 ft wide and 23 ft deep and similar to the entrance from the Thames to London Docks of about the same date, also engineered by Rennie. This fine example of his practice is located at the east end of the no longer existing East Dock, joining to the old inner harbour on the river course. The timber lock gates, slightly curved in plan, and now disused were operated by a chain and winch system. The east gates probably date from an improvement by James Leslie in ca.1846 and the west gates from 1922.

There have been two turn bridges at this location; the first of timber dating from 1806 and the second, the present iron structure, erected in ca.1850. This bridge is 15 ft wide in two halves giving a clear span of 35 ft 6 in. with a skew of approximately 858. The distance between the centres of 160 rotation is 56 ft and the overall length 87 ft 3 in. The deck is timber with wrought-iron handrails and iron cart-wheel channels. Structurally the bridge is a three pin arch with six cast-iron ribs. It is opened by raising pivoted sections of the arch members adjacent to the springings by means of winches built into the deck; this frees the two halves of the bridge to rotate in plan. The drive mechanism is operated through capstans turning pinions which engage with racks fixed to the swing sections below road level. The eastern pier extension of 1826–29 began on the east side of the river opposite and north of the old dock entrance.

R Paxton and J Shipway 2007

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