The truth is, all of Britain’s canals are ‘industrial heritage’ in their own right, but they all have some unique pieces of engineering & architecture that stand out. The Union Canal, running between Falkirk and Edinburgh, is no exception. I took a narrowboat on a short trip along half of it to see its key features.

Three of them in particular are squeezed into the first few miles of its 31-mile route to Edinburgh – The Falkirk Wheel, The Falkirk Canal Tunnel and the Avon Aqueduct.

The Scottish Lowland Canals

The Forth & Clyde Canal and the Union Canal are linked together at Falkirk, and are themselves amazing pieces of engineering.

The Forth & Clyde Canal was built so that ships and cargoes could get from one side of Scotland to the other (Irish Sea to North Sea) without having to sail around the often dangerous north coast. Its route was surveyed by civil engineer, John Smeaton, in 1763 and five years later construction work began. It was completed in 1790.

The canal was built with 33 big locks (68ft x 20ft) so that it could take sea-going vessels. It runs northeast for 38 miles, from the river lock at Bowling near Clydebank on the north side of the Clyde, all the way up to the river lock onto the River Carron outside Grangemouth, where The Kelpies are located. The Carron flows into the Firth of Forth Estuary just 1.6m (2.6km) away. Four miles and 16 locks back, before the canal reaches the Carron, it passes the lock basin at the Falkirk Wheel, which is where boats can transfer up to the Union Canal to go to Edinburgh.

Work on the 30-mile Union Canal, which took narrowboat traffic from Falkirk to Edinburgh, began in 1818 and was completed in 1822, with a flight of 11 locks connecting the two canals just outside Falkirk. The Union Canal then runs high up along the southern bank of the Firth of Forth, following the 240 ft contour line together with the main line railway, so there was no need for any more locks.

Unfortunately, by the late 19th and early 20th centuries, the competing railway and road networks took more and more traffic from the canals, bringing about their inevitable decline. In 1933 the locks connecting the two canals were demolished and filled in. In 1963 the Forth & Clyde Canal was closed to traffic, and the Union Canal closed two years later.

The renaissance came in 1999 when work began on the £78m Millennium Link project to restore both canals to their former glory. The project was funded through contributions from the Millennium Commission, Scottish Enterprise, the European Union, canal side local authorities and British Waterways.

The centrepiece of the project was the Falkirk Wheel which was  opened by HM Queen Elizabeth II in 2002.

 

The Falkirk Wheel boat lift

The Falkirk Wheel is an astonishing and unique piece of engineering design on a grand scale. It is the only rotating boat lift of its kind in the world and its design genius is in its simplicity – a pair of opposing 18-metre (57ft) arms, each holding a 250,000-litre water-filled caisson (or “gondola”) that can carry boats, rotate through 180°.

The opposing gondolas themselves slowly rotate, driven by cogs from the main axle, to keep them level while the wheel is turning and are perfectly balanced with each other no matter what is in them. There could be four boats in one and none in the other, but since, as Archimedes explained, a boat weighs the same as the water it displaces, as long as the gondolas are filled to the same level, the weight is the same! This means it is also fabulously efficient. The power needed to lift (and lower) the gondolas would boil 8 electric kettles!

The engineering gets more complicated when it comes to the system for sealing off and separating the water in the gondolas from the aqueduct at the top and the basin at the bottom. Two doors rise to seal the water from the gondola side and the basin/aqueduct side, then the water is pumped out from the gap between them. It’s pretty ingenious stuff.

Most articles say that the complete half-rotation takes 15 mins. It doesn’t. Maybe in aviation terms the ‘block to block’* time from a boat’s entry into the gondola and exit, ends up at 15 minutes, but the rotation itself is five mins. Here it is in real time…

By the way, did you notice a stream of people walking up the hill in the distance? One of the important elements of the Millennium Link project was the creation of a continuous towpath for walkers, cyclists and runners. The day I filmed that video was the day of this year’s Glasgow to Edinburgh Ultra Marathon, which uses that towpath. Those people on the hill are exhausted marathon runners (and their supporters) half-way through their 59-mile race!

The reason the Falkirk Wheel draws so many visitors and is one of Scotland’s tourism icons, is not just for its engineering significance. It’s also a work of art. The arms didn’t need elegantly curved counterweights, but don’t they look good! It is said that Tony Kettle of RMJM Architects who designed the ‘look’ of the Wheel was inspired by propeller blades, double-headed Celtic axes, and/or whale ribs. Whether true or not, Kettle took the early ideas for the Wheel, which included a simple but rather uninspiring Ferris wheel and a giant egg-shaped vessel that tipped over, and turned them into something elegant. It was the builders, Ove Arup/ Butterley Engineering who turned it into reality.

Look at those supports for the aqueduct at the top of the Wheel. Any normal civil engineer would just build simple pillars for the aqueduct to rest on. They didn’t have to be elegant circles mirroring the circles supporting the gondolas! The whole thing just looks beautiful as well as functional.

The Union Canal is referred to as a “contour canal” with no locks. That didn’t count the original flight of eleven locks down to the Forth & Clyde Canal. The Falkirk Wheel Interchange also has locks. The first, the Golden Jubilee Lock, lifts boats a short height from the Forth & Clyde Canal up into the Falkirk Wheel basin. The Wheel then raises boats by 24 metres to the aqueduct, but the Union Canal is still 11 metres higher. After the aqueduct there is a short 334m (365 yards) tunnel, the Roughcastle Tunnel, which takes boats under Rough Castle, the site of a Roman Fort, and the Edinburgh-Glasgow mainline railway track. Then comes a flight of two locks that finally lift boats up to the Union Canal. Actually it is a 1.1km extension to the Union Canal, built specifically for the Falkirk Wheel Interchange, from the point where the original flight of 11 locks descended down to Port Downie on the Forth & Clyde (by Lock 16).

The Rough Castle fort marks the location of another piece of engineering – the Antonine Wall (“Vallum Antonini”, begun in AD 142, two decades after Hadrian’s Wall), which marked the Northernmost point of the Roman Empire. It was a turf wall built on a stone base and parts of it are still visible near the canal.

By the way, what do you think the Falkirk Wheel site was before they built the Wheel? A: The Roughcastle Tar Works, which had been there since the canal was first opened.

The Falkirk Wheel is not the only working boat lift in the United Kingdom, the other being the Anderton Boat Lift (1875) in Cheshire. (The Anderton Lift also which inspired the town of Arques in Pas-de-Calais, France to build their Fontinettes Boat Lift (1888), now a national monument but sadly no longer working.)

The Falkirk Canal Tunnel

Three kilometres (1.9 miles) east from the Falkirk Wheel locks comes the Falkirk Canal Tunnel. At 630 metres (around 0.4 miles) in length, it is the longest canal tunnel in Scotland.

When, in 1813, engineer Hugh Baird proposed the canal route to link Edinburgh and Falkirk, local landowner William Forbes was up in arms! He objected to the route being anywhere near his Callendar House estate. Forbes, a billionaire by today’s standards, had powerful friends in Parliament and he raised such a stink over the matter, Baird was forced to skirt around the estate and that meant blasting a tunnel under Prospect Hill. It’s noticeable that the railway also had to build a tunnel to get around the estate. Forbes didn’t get to enjoy his uninterrupted views for long. He died within a year of the canal’s completion!

The tunnel was a major piece of engineering requiring tons of explosives and hundreds of “navvies” (labourers) to dig through solid rock. It later turned out that two of those navvies were William Burke and William Hare, who moved to Edinburgh after work on the canal ended and became famous as grave robbers and murderers, supplying cadavers to the medical research industry.

Known as the “Dark Tunnel”, the tunnel was a wet and gloomy place, avoided by all but the stoutest hearted. Now, as part of the Millennium Link project it has a new towpath and is brightly lit with LED lighting, that can change colour at the press of a button on the operator’s phone while sitting at home! The new lighting has revealed previously unseen aspects of the tunnel’s construction such as candle holders and explosives stores. It also highlights two hundred years of stalactite growth.

When I went through, at a leisurely 3 knots, it took just over 12 minutes to emerge at the other end.

The Avon Aqueduct

The Union Canal has three aqueducts (not counting the Falkirk Wheel aqueduct), but the Avon Aqueduct, 13 kms from the Falkirk Wheel locks, is the largest in Scotland and the second largest in Britain.

All three aqueducts on the canal use the same construction of hollow stone piers and arches spanning 50ft (15.2m) with the canal channelled over in an iron trough. The result is, they look majestic, and at 247m (810ft) long, on 12 arches towering 25.9m (85ft) over the Avon River valley below, the Avon Aqueduct is the most impressive of all.

The other two aqueducts are pretty impressive too. The 500ft eight-arched Slateford Aqueduct on the edge of Edinburgh takes the canal over the Water of Leith. Lin’s Mill Aqueduct to the west of Ratho takes the canal over the River Almond in just five arches.

Muiravonside Breach

Not exactly a piece of industrial heritage on the Union Canal, but an interesting engineering event that I learned about accidently.

See that stretch of canal bank without any grass or reeds, just in front of our boat? I learned from an early morning walker that we had moored next to the ‘great breach’.

On the night of 11 Aug 2020 a massive storm hit central Scotland with rain falling at up to 40mm an hour. In the early hours of the morning, a large lake of floodwater that had formed on the hill above the canal, suddenly washed over the canal and swept away the embankment and towpath leaving a 30-metre wide breach. Combined with the draining waters of the canal, it inundated the farmland and mainline railway tracks below.

(It occurs to me that this might be a downside of lock-less canals! At least a canal with locks would only be drained in one section.)

Scottish Canals emergency crews were quickly on scene patching up the breach and rescuing over 11,000 displaced fish, but the canal wasn’t fully repaired and re-opened till April 2021.

Wester Hailes Section

One piece of engineering you might miss altogether is on the outskirts of Edinburgh (just near the National Trust for Scotland HQ building which overlooks the canal). After the canal closed in 1965 part of it was filled in during the development of the Wester Hailes housing scheme, and the Millennium Link project had to build a new stretch of canal to get around it.

How best to see the Union Canal and its industrial heritage

All of these things you can see independently. The Millennium Link towpath means you can walk or cycle to them, and there are boat operators who offer local day trips on the canal.

Visiting the Falkirk Wheel is easy, and there is a large visitors centre on site with plenty of information about the Wheel. There is also a short (50 min) guided cruise** which operates several times a day. It takes visitors from outside the visitors centre on a round trip up on the Wheel, through the Roughcastle tunnel to the Falkirk Wheel Locks and back.

For a really close look, there is a 2½ hour specialist ‘Behind the Wheel‘ guided tour, inside the workings of the Wheel. There are morning and afternoon tours for max 8 people, scheduled roughly once a month. It’s a chance to see the mechanics of the Wheel close-up, and be impressed. Two men, one standing on the shoulders of the other, can stand inside the main axle… apparently. (I was booked on a tour, but it was cancelled at the last minute, sadly.)

But, the best way to explore the industrial heritage of the Union Canal is to motor along it yourself, at your own pace, in a narrowboat. See A Guide to Narrowboating on the Union Canal.

Declaration: I was a guest of Black Prince Holidays, skippering one of their new Signature 6 class narrowboats on a short 3-night break on the Union Canal.

---

* The aviation industry measures “block-to-block” journey time – from the moment the chocks are removed from under the wheels, to the time they are placed at the destination airport.

** confusingly called the ‘Original Tour Boat Trip’ because there used to be another one that simply took visitors on a full rotation of the wheel.