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Caledonian Canal
Corpach to Clachnaharry, Great Glen, Highland, Scotland, UK
Caledonian Canal
associated engineer
Thomas Telford
William Jessop
date  April 1804 - 1847, opened 23rd October 1822
UK era  Georgian  |  category  Canal/Navigation works  |  reference  NN295976
ICE reference number  HEW 84
photo  © and licensed for reuse under this
The Caledonian Canal bisects Scotland, linking the Irish Sea to the North Sea via the Great Glen. Its design and construction was state-of-the-art for the time, and advanced 19th century engineering methods considerably. Its now one of Scotland’s most outstanding tourist attractions and is open year round in daylight hours.
James Watt (1736-1819) had prepared a survey for a canal in the Great Glen in 1773 but no action was taken at that time. In 1801 Thomas Telford (1757-1834) also surveyed the glen, and in 1802 he reported on the feasibility of a canal. This led to the creation of the Caledonian Canal Commission under an Act of Parliament that received royal assent on 27th July 1803. The main purposes were to provide a quicker and safer east-west route than the hazardous Pentland Firth for naval and commercial shipping, to create employment for Highlanders and to develop the Highlands generally.
Telford was appointed principal engineer to the commission, with William Jessop (1745-1814) as consulting engineer. Work began in about April 1804, and a further Act of Parliament was passed on 29th June that year. Jessop estimated the cost of the canal at £474,500 (excluding land purchases) and the construction time at seven years. In the event, the canal opened in October 1822 after expenditure of £1.2m.
The Calendonian Canal is 97km long. However, 60km of it is routed through four natural lochs — Dochfour, Ness, Oich and Lochy — leaving 37km of constructed channel. This involved the building of 28 locks, later increased to 29. These are all of a similar size and were then the world’s largest locks, at mainly 55m long, 12.2m wide and some 6m deep (7.6m from the centre of the inverted arch of the lock floor to the top of the wall coping).
The canal channel was designed to be 33.5m wide at the surface, 6.1m deep and 15.2m wide at the bottom. Its summit at Laggan is 32.3m above sea level. However, the 6.1m depth wasn't attained by 1822 because of difficult ground conditions. Shortly after opening, the canal had a minimum depth throughout of 3.7m, and steam-powered dredging continued.
The significant structures along the canal are Clachnaharry Sea Lock (1808-12) at its north eastern end, four locks at Muirtown (1808-13), five locks at Fort Augustus (1816-20), Loy and Shangan Aqueducts (1806-8), Moy Swing Bridge (1820), Mucomer Cut and Bridge (1813), eight locks at Neptune’s Staircase in Banavie (1808-11) and Corpach Sea Lock (1807-12) at its south western end.
There were delays and difficulties in building the sea and Fort Augustus (pictured) locks. Other challenges included the raising of the level of Loch Lochy by 3.7m, the excavation of the 12.2m deep, 3.2km long Laggan Cutting (NN293974), and the diversion of Loch Lochy in order to use the old river bed.
By April 1805, the western end of the site had 404 workers supervised by resident engineer John Telford (c1771-1807, no relation of Thomas) until his death. Alexander Easton (1787-1854) took over this section until 1823. In the east, Matthew Davidson (1755-1819) had charge of about 500 men, until his death. His youngest son James Davidson (1798-1877) was given the post, and became resident engineer for the whole canal in 1823. The scheme employed a total workforce of more than 3,000 men.
Constructing a canal in the early 19th century was an immense undertaking and this one was difficult, not least for its remoteness, the aggressive ground conditions, the harsh climate and the largely unskilled itinerant labour force. However, canal engineering design and construction was significantly advanced with the Caledonian Canal through use of such technologies as horse-traction plateways and special wagons, and steam-powered pumping and dredging.
The steam dredger used was among the earliest in Scotland, and was purpose-built in 1814. Overall it was 24.4m long by 7m wide, with 25 buckets on a 12.8m long frame. It was powered by a condensing steam engine of 4.5kW (6hp) that consumed about 760kg of coal daily. At its best, the dredger could yield some 91 tonnes of material per hour, discharging 17 buckets per minute.
Though the canal was open for through traffic from 1822, there was still work to be done to complete the project to Telford’s plans. As part of the ongoing work, a third Act of Parliament received royal assent on 31st March 1825.
Work during 1843-7 was carried out under the direction of Telford’s successors James Walker (1781-1862) and Alfred Burges (1796-1886). The canal was repaired, improved and deepened to 5.2m and could then accommodate vessels with drafts of up to 4.9m. After this, the canal attracted larger vessels engaged in the Baltic trade, but ship sizes were increasing generally, making the canal less necessary for safe east-west passage — many took the coastal route. The canal was also too small for some of the new vessels.
However, the canal continued to make a significant contribution to Highland development and its economy, through fishing and tourism, and it was much used in World War I (1914-8). For the year ended 30th April 1919, there were 5,439 through passages.
The lock gates were mechanised in 1959-68. Repairs and improvements in recent years by British Waterways have brought the canal up to a high standard of maintenance, allowing vessels of drafts up to 4.1m to enter. Today, the Caledonian Canal is essentially as-created by Telford and Jessop. Its authentic conservation is encouraging increasing leisure use, and it is still a good shortcut for smaller commercial vessels.
Resident engineer (1804-7): John Telford
Resident engineer (1804-19): Matthew Davidson
Resident engineer (1807-23): Alexander Easton
Resident engineer (1819-29, 1867-77): James Davidson
Resident engineer (1829-67): George May
Contractors: John Simpson and John Cargill, John Simpson and John Wilson, and Thomas Rhodes
Iron castings: Butterly Ironworks
Ironwork: William Hazeldine, Plas Kynaston
Research: ECPK
"Historical Account of the Navigable Rivers, Canals, and Railways, of Great Britain" by Joseph Priestley
Longman, Rees, Orme, Brown & Green, London, April 1831
"The Caledonian Canal” by Thomas Telford, in Life of Telford, Vol.1, pp.49-67, ICE virtual library, London, January 1838
"Description of a Steam Dredging Engine used upon the Caledonian Canal"
by Walter Elliot, in Minutes of ICE Proceedings, Vol.2, pp.149-150,
London, January 1842
"Skipper’s Guide: Caledonian Canal" by Scottish Canals
British Waterways Scotland, Glasgow, 2008
reference sources   CEH SHIBDCE1

Caledonian Canal