Drawbridge, Craigmarloch, Forth and Clyde Canal, North Lanarkshire

Ink on polyester film, 1981
Survey by RCAHMS

Black and white photograph, 1963
Survey by RCAHMS

RCAHMS has undertaken a number of surveys through the years to document the length of the Forth and Clyde Canal. From aerial photographs to detailed drawings, as here, we have illustrated the operation of the bridges and locks. 

The Forth and Clyde Canal was constructed to link the west and east coasts of Scotland so that ships could avoid the treacherous Pentland Firth. It was engineered by James Smeaton (1724-1778) and Robert Mackell (died 1779) and begins at Bowling harbour in the Firth of Clyde, and terminates at Grangemouth on the Firth of Forth. Begun in 1768 and finished in 1791, it had 43 aqueducts and 33 timber draw or bascule bridges to allow the canal to be crossed by passengers. 

A bascule bridge (also known as a draw bridge) is hinged at the bank allowing the arm crossing the canal to be raised to allow boats to pass.  Craigmarloch Bridge was a two-part manually-operated bascule bridge with counterweights in pits on either bank to enable the ‘arms’ to be lifted. When the bridge was lifted, only vessels of less than 21ft (6.4m) could pass through.

The canal was closed to navigation in 1963 but re-opened in May 2001 following extensive renovations.