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The Union Canal is one of two Lowland canals in Scotland. After four years' construction it opened in 1822 and was known as the Edinburgh and Glasgow Union Canal. The name reflected the role of the canal, linking Edinburgh with the Forth and Clyde Canal at Falkirk and so providing a through route between Scotland's two major cities.
The Union Canal as built was 31½ miles long and was Scotland's only contour canal. Known locally at the time as the "mathematical river", the canal followed the 240ft (73m) contour throughout its length, so making locks unnecessary. Together with the 62 fixed bridges this helped speed up the flow of traffic along the canal.
As well as providing Scotland's first inter-city link the canal was intended to ensure the easy transport of coal into Edinburgh from Scotland's coalfields, and lime to help the development of the capital.
The original estimates for building the canal had been a suspiciously precise £240,500. The final cost was nearly twice as much: £461,760. In part this reflected the need to build a 2,070ft tunnel and a deep cutting near Falkirk because the owner of Callendar House didn't want the canal on his land.
The increase in costs also reflected some of the necessary work in building a flat canal across land cut by river valleys. The outcome was three major aqueducts. The 500ft eight-arched Slateford Aqueduct on the edge of Edinburgh takes the canal over the Water of Leith. Possibly the most spectacular is the Lin's Mill Aqueduct over the River Almond west of Ratho, which takes the canal over the River Almond in just five arches, 75ft above the river. Interestingly enough the water level in the canal is maintained by a feeder system starting with a reservoir in the Pentland Hills to the south, but including a three mile channel from the River Almond at Mid Calder to the canal close to the Lin's Mill Aqueduct.
The largest of the Union Canal aqueducts is the one taking the canal over the River Avon west of Linlithgow. This is 810ft long and 86ft high, the second longest in Britain. This can be viewed from paths in the Muiravonside Country Park. The canal level of the Lin's Mill Aqueduct is also fairly accessible, from a car park off a very minor road near Clifton Hall. Getting to the River Almond 75ft below is less straightforward, requiring a little scrambling.
Although the canal was built without locks, a way needed to be found of linking the Union Canal with the Forth and Clyde Canal, a difference in height of 110ft where they met. The answer was a staircase of 11 locks over a half mile length of canal at Camelon near Falkirk. This emerged into the Forth and Clyde just to the east of the Union Inn.
The Union Canal was a wonderful feat of engineering, but it came too late. Just 20 years after it was finished the railways started to take away the passenger and freight traffic its viability depended on, and it went into a long period of decline. This culminated in 1965 with the formal closure of the canal by Act of Parliament.
Although parts of the canal remained navigable, especially around Ratho and Linlithgow, the chances of ever returning it to full use diminished steadily. Particular problems were caused when the M8 motorway cut the canal west of Ratho during its construction; while an entire stretch of canal was filled in during the development of the Wester Hailes housing scheme on the outskirts of Edinburgh. And at Camelon the 11 locks linking the two canals were also removed.
Despite this some visionaries refused to give up and the tide finally began to turn in the 1990s. Restoring the Union Canal and the Forth and Clyde Canals, a project jointly known as the Millennium Link, cost some £84.5m. This included funding from the EU and the Millennium Commission; but with a lot of the investment based on projections of higher land values likely to be caused by the restored canals themselves.
Many barriers had to be overcome. A new stretch of canal had to be dug at Wester Hailes. And where it was cut by the M8 motorway the Union Canal was diverted a little to the west through a new channel and a bridge was created, entailing the lifting of the whole roadway. Most significantly, a way had to be found of linking the canals together in the absence of the 11 locks that used to do the job. The answer was an extension to the Union Canal leading to the top of the magnificent Falkirk Wheel, which was opened by the Queen in May 2002, marking the completion of the Millennium Link.