The Caledonian Canal connects the Scottish east coast at Inverness with the west coast at Corpach near Fort William in Scotland. The canal was constructed in the early nineteenth century by Scottish engineer Thomas Telford.
Route The canal runs some from northeast to southwest and reaches above sea level. Only one third of the entire length is man-made, the rest being formed by Loch Dochfour, Loch Ness, Loch Oich, and Loch Lochy. These lochs are located in the Great Glen, on a geological fault in the Earth's crust. There are 29 locks (including eight at Neptune's Staircase, Banavie), four aqueducts and 10 bridges in the course of the canal.
Northern section The canal starts at its north-eastern end at Clachnaharry Sea Lock, built at the end of a man-made peninsula to ensure that boats could always reach the deep water of the Beauly Firth. Because the peninsula is built with mud foundations, it has required regular maintenance ever since. Next to the lock is the former lock-keeper's house, a two-storey building with a single-storey bothy at its western end and an enclosed garden. At an unknown date, the house was divided into two, and in 2005 the eastern half became offices for Scottish Canals. The building is a category C listed structure. At the opposite end of the peninsula to the sea lock, a swing bridge carries the Far North railway line across the canal. The first bridge at the site was designed by Joseph Mitchell for the Inverness and Ross-shire Railway, and was constructed of wrought iron in 1862. This was replaced by a similar structure in 1909, made of steel, which is long. The bridge, together with the adjacent signal box, designed by Mackenzie and Holland for the Highland Railway in 1890, is a category B listed structure.
Clachnaharry lock is next to the swing bridge, and is bordered by a smiddy and workshops, dating from the canal's construction in 1810, and extended in 1840–50. The smiddy still contains two hearths for forging metal. Muirtown Basin provides moorings at the eastern end of the canal, which takes a right-angled turn at the far end to pass under a swing bridge carrying the A862 road to reach the flight of four Muirtown Locks. From the top of the flight, the canal continues southwards to Tomnahurich swing bridge, which carries the A82 road over the canal. The original timber bridge was replaced by a steel structure in 1938, designed by Crouch and Hogg, which included a control box, as levels of traffic on the road and canal were increasing. Nearby is the former bridge keeper's cottage, built in the 1820s. It was no longer needed to house a bridge keeper after 1965, and after being empty for some years, was converted into self-catering accommodation. A short distance to the south a second swing bridge was opened in June 2021, as part of the Inverness West Link project. A new control building was built between the two bridges, so that both could be controlled from a single location. The concept behind the second bridge was that traffic could be diverted to use one of the bridges while the other was open for canal traffic.
The canal from Muirtown Locks to Dochgarroch Lock is a scheduled monument, as is Dochgarroch Lock, which was designed to protect the canal from flooding caused by fluctuating levels in the River Ness, which flows over a weir to the south of the lock. A two-storey lock keeper's cottage and barn dating from the 1850s overlooks the lock. The final section of canal to Loch Dochfour is also scheduled, and the designated area includes the weir for the River Ness, and the west bank of Loch Dochfour as far as Loch Ness. At its southern end is Bona Lighthouse, built as a house by Thomas Telford in 1815, and altered around 1848 to act as a lighthouse. The building is octagonal, with two storeys, and is a rare example of an inland light. There was once a ferry across the Bona channel at this point. In 1844, the channel was made deeper and wider when barges pulled by horses were replaced by steam tugs, and there is evidence that the building once included four stables. The canal section from Clachnaharry Sea Lock to Bona is long, and from there it is over along Loch Ness to the next canal section at Fort Augustus.
Middle section At the foot of Loch Ness, the Caledonian Canal leaves the west bank of the loch, with the River Oich to the north and the River Tarff to the south. The A82 road crosses the canal on a swing bridge, at the foot of the five locks that rise through the centre of the village of Fort Augustus. In 1975 only the locks were included in the scheduled monument designation, but that was subsequently extended to include all of the canal between them and Loch Ness, including the lighthouse at the entrance to this section of canal. At the top of the locks, a road beside the canal is spanned by a railway bridge, which was constructed to carry an intended line from Fort Augustus to Inverness. The bridge was in use from 1903 to 1906, when the railway project was abandoned. As well as the bridge, some piers built to carry the line over the River Oich can also be seen, although these are in a poor state of repair. The canal to Kyltra Lock and the lock itself are both scheduled monuments. The canal continues to Cullochy Lock, where to the north of the structure there is a single storey lock keeper's cottage on the west bank which dates from the building of the canal, and a pair of two-storey houses for the lock keepers, dating from around 1830, on the east bank. On the east side of the lock is a single-storey storehouse dating from 1815 to 1820, which has three bays and internally is divided into a store and an office for the lock keeper.
The final part of the canal on this section runs from the lock to Loch Oich, and includes the abutments of a small swing bridge which formerly provided an accommodation crossing over the canal. The more modern Aberchalder swing bridge carries the A82 over the canal. A single-storey three bay cottage designed by Telford once provided housing for the bridge keeper. Nearby is the old bridge that carried the road over the River Oich, which was probably designed by James Dredge in the 1850s. It is a chain suspension bridge, and a long dry stone causeway provides access from the east. The A82 crosses the river on a three-arched concrete bridge designed by Mears and Carus-Wilson and constructed in 1932. Loch Oich is the summit of the canal, at above sea level, and despite its relatively small size compared to Loch Ness and Loch Lochy, it provides most of the of water that is required each day to keep the canal operating.
The short section of canal between Loch Oich and Loch Lochy is crossed by a plate girder swing bridge carrying the A82 road at its northern end, and ends at a pair of locks at its southern end. Two jetties project out into Loch Lochy, and much of the structure is built on reclaimed land. A single-storey store with basement stands to the east of the locks, which was probably used to store materials and to provide stabling for horses while the canal was being constructed. On the west bank is Glenjade Cottage, dating from 1840 to 1860, which was once a pair of cottages but was converted into a single dwelling in the late 20th century. Ivy Cottage was also built for lock keepers, but was completed for the opening of the canal, and so is older than Glenjade cottages.
Southern section Loch Lochy is about long, and the next canal section starts at its southern end. Its entrance is marked by a small lighthouse, while to the east of the canal is the Mucomir Cut, which delivers water from the loch to Mucomir hydroelectric station and the River Lochy. There are two locks at Gairlochy, the upper one being the only lock which was not built for the opening of the canal. It was added in 1844, and was constructed by Jackson and Bean. Between the locks is Telford House, a large lock keeper's house built in 1811–13, and much larger than most of the other houses built along the canal. The B8084 road crosses the canal on a swing bridge at the upstream end of Gairlochy lower lock, but it is unclear whether it is part of the scheduled monument, since it is not specifically mentioned in the listing, whereas most bridges are either included or excluded. About further downstream is Moy Swing Bridge, an original accommodation bridge. It consists of two halves, and the lock keeper from Gairlochy opens the eastern half by operating a capstan, and then crosses the canal by punt to perform a similar action on the western half. A three-bay single-storey cottage, dating from around 1820, survives on the eastern bank of the canal next to the bridge.
The section below Moy Bridge includes four aqueducts which carry the canal over local rivers. These are the Loy aqueduct, the Muirshearlich aqueduct, the Sheangain aqueduct and the Mount Alexander aqueduct. The Loy aqueduct consists of three parallel arches, long, with the River Loy passing through the centre arch, and the side arches used for pedestrians and animals, although they sometimes carry flood flow from the river. Torcastle aqueduct is similar but slightly shorter at , and carries the Allt Sheangain in two of the arches, with the third used as a roadway. Mount Alexander aqueduct only has two arches, one used by the Allt Mor, and the other a footpath.
Soon the canal arrives at the top of Neptune's Staircase, a flight of eight locks that drop the level of the canal by in the space of . Halfway down the flight to the west is another house similar to that at Gairlochy, but split to provide accommodation for two lock keepers. On the eastern bank is a smithy and sawpits, dating from the 1820s, and a workshop dating from 1880 to 1890. Neptune's Staircase was originally fitted with 36 capstans each of which had to be rotated 20 times to operate the lock gates and sluices, but progress through the structure was sped up in the 20th century when the flight was mechanised. At the foot of the locks, a swing bridge carries the A830 road over the canal, and a steel bow truss swing bridge, built in 1901 by Simpson and Wilson, carries the West Highland Line from to . The canal turns to the west to reach a pair of staircase locks at Corpach, which is followed by a small basin and the final sea lock to allow boats to access Loch Linnhe.
Names The canal has several names in Scottish Gaelic including Amar-Uisge/Seòlaid a' Ghlinne Mhòir ("Waterway of the Great Glen"), Sligh'-Uisge na h-Alba ("Waterway of Scotland") and a literal translation (An) Canàl Cailleannach.
History In 1620, a Highland prophet called the Brahan Seer predicted that full-rigged ships would one day be sailing round the back of Tomnahurich, near Inverness, at a time when the only navigable route near the location was the River Ness, on the other side of Tomnahurich.
Engineers started to look at the feasibility of a canal to connect Loch Linnhe near Fort William to the Moray Firth near Inverness in the 18th century, with Captain Edward Burt rejecting the idea in 1726, as he thought the mountains would channel the wind and make navigation too precarious.
The Commissioners of Forfeited Estates had originally been set up to handle the seizure and sale of land previously owned by those who had been convicted of treason following the Jacobite rising of 1715. By 1773, they had turned their attention to helping the fishing industry, and commissioned the inventor and mechanical engineer James Watt to make a survey of the route. He published a report in 1774, which suggested that a deep canal from Fort William to Inverness, passing through Loch Lochy, Loch Oich, Loch Ness and Loch Dochfour, would require 32 locks, and could be built for £164,032. He emphasised the benefits to the fishing industry, of a shorter and safer route from the east to the west coast of Scotland, and the potential for supplying the population with cheaper corn, but again, thought that winds on the lochs might be a problem.