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Caledonian Canal, Corpach Sea Lock

Lock (Post Medieval)

Site Name Caledonian Canal, Corpach Sea Lock

Classification Lock (Post Medieval)

Alternative Name(s) Corpach, Western Lock; Corpach Entrance Loch; Loch Linnhe; Loch Eil

Canmore ID 105786

Site Number NN07NE 9.02

NGR NN 09589 76633

Datum OSGB36 - NGR


Ordnance Survey licence number 100057073. All rights reserved.
Canmore Disclaimer. © Copyright and database right 2019.

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Administrative Areas

  • Council Highland
  • Parish Kilmallie
  • Former Region Highland
  • Former District Lochaber
  • Former County Inverness-shire

Archaeology Notes

NN07NE 9.02 09589 76633

Lock [NAT]

OS (GIS) AIB, May 2006.

Location formerly entered as NN 0956 7663.

Not to be confused with Corpach Locks (centred NN 09870 76622), for which see NN07NE 9.04.

ARCHITECT: John Simpson.

(Undated) information in NMRS.

The original gates were made of Welsh oak, and the lock itself held 18 feet [5.5m depth] of water. However, between 1890 and 1906 the original gates were replaced by new ones constructed from oak and steel. By the mid 20th century the lock was mechanized and in 1964-5 the whole lock was adapted in order to accommodate vessels of 1000 tons.

J Lindsay 1968.

The sea lock has been enlarged to accommodate vessels serving the large wood-pulp mill (NN07NE 10.00) recently constructed beside Loch Eil.

H McKnight 1975.

Access to the canal is through this sea lock.

A Burton 1983.

This sea lock constitutes the southern or western terminal of the canal. Situated three miles to the NW of Fort William at Corpach it is at the point where Loch Linnhe and Loch Eil meet. Built to permit vessels in the basin (NN07NE 9.06) to load and unload, it was opened in 1819 and enlarged in the 1960s as an adjunct to the development of the Corpach pulp mill, now closed.

G Hutton 1992.

This lock is clearly visible on the 2nd edition of the OS 6-inch map (Inverness-shire 1904, sheet cl), on the current edition of the OS 1:10000 map (1975) and on the OS Basic Scale raster map (ND).

Information from RCAHMS (MD), 23 August 2001.


Publication Account (2007)

(Institute Civil Engineers Historic Engineering Works no. HEW 0084/08)

Corpach Sea-lock

The construction of this tide lock at Loch Linnhe from 1808–12 called for exceptional engineering skill and provides another classic foundation case study differing from that already described at Clachnaharry. This lock had to be founded on an underwater rock at a point where the lock sill would be covered by 21 ft of water at high water of neap tides. Water-tight mounds faced with rubble-stone were carried from the shore beyond the end of the lockpit, between which a wooden coffer-dam, with 14 ft thick

clay puddle wall, was constructed.

This difficult and unprecedented operation involved dowelling the framing piles into the rock through 8 ft of silt and gravel by means of a hooped cylinder and piling engine with an 1008 lb ram. Steam-powered pumping

was used to de-water the excavation, an early instance of such practice on a large scale.

The contractors were Simpson and Wilson, chiefly the latter. The resident Engineer was John Telford who died in 1807 and was succeeded by Alexander Easton.

From here on a clear day it is possible to see the site of Thomas Stevenson’s highest project, the observatory on Ben Nevis which he planned in 1874 as Secretary of the Scottish Meteorological Society. It was completed in 1883, flourished for two decades, and closed for lack of funding in 1904.

R Paxton and J Shipway, 2007.

Reproduced from 'Civil Engineering heritage: Scotland - Highlands and Islands' with kind permission from Thomas Telford Publishers.

Field Visit (16 October 2013 - 16 October 2013)

Corpach Sea Lock. NN07NE 9.02

A lock with two gates and the usual type of furniture – bollards, hooks and 3 capstans, one with the remains of a gearing device. To the west of the sea gate there are slots for a coffer dam and on the south wall of the canal roman numerals inscribed into the stonework, presumably marking the height of the sea. Within the lock there is evidence of the original position of the east gate; 15m west of the current east gate; there is a pivot in the stonework, a rebate 8m in length, cills for the hawsers to operate the gate and similar roman numerals to those on the outside of the west gate. On the south side of the lock a grassed area, with footpaths, picnic tables and a commemorative stone, occupies the site of the former Engine House, NN07NE 9.01. On the north side the beacon NN07NE 9.03 and several buildings – a store (previously unrecorded), a house called Askaig (previously unrecorded) part of the former toll-house (previously unrecorded) and old stables/storehouse NN07NE 15

Visited by Scottish Canals Recording Project (MM), 16 October 2013


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