The world's first coast to coast ship canal, the 57km long Forth & Clyde, was completed by John Smeaton in 1790 allowing cargoes ranging from Highland whisky to Baltic timber direct access between the Atlantic and the North Sea.
Sailing ships negotiated 32 opening or swing bridges, 40 locks and 25 aqueducts journeying between ports at Bowling, Glasgow and Grangemouth.
By contrast the unusual 51km 'contour' Union Canal, which opened 32 years later, boasted 62 masonry arch bridges and 24 aqueducts, but no locks at all. Its engineer Hugh Baird followed - to an accuracy of 25mm - the now 73.14m contour level providing a route for coal barges from central collieries direct to Edinburgh. The two canals were later linked at Falkirk, where an 11 lock staircase overcame the 35m height difference.
Both waterways were unceremonially closed in the early 1960s when road engineers first opted to save a few thousand pounds by routing the A80 at low level over the Forth & Clyde and, a few years later, cut just £16,000 of their construction bill by severing the Union Canal with the M8 motorway.