Civil Engineering heritage: Scotland - Highlands and Islands
Date 2007
Event ID 963050
Category Descriptive Accounts
Type Publication Account
Permalink http://canmore.org.uk/event/963050
Mousa Broch, Shetland
(Institute Civil Engineers Historic Engineering Works no. HEW 2398)
This prehistoric round stone tower is located on the small uninhabited island of Mousa off the mainland about 12 miles south of Lerwick. The remains of about 500 brochs have been identified in Scotland, most of which are in Caithness, Orkney, Shetland and the Western Isles, but Mousa Broch is the only one to have survived virtually complete.
Although not strictly civil engineering, a term not known to have been used before 1754, this remarkable structure, which has stood the test of some 2000 years, certainly comes within the definition of harnessing the forces of nature for the use and convenience of man. Other good examples can be seen at Carloway, Isle of Lewis (5-51) and Clickhimin, near Lerwick, Shetland.
The broch is 43 1/2 ft high, and the overall diameter at its base is 50 ft and at the top 40 ft. The wall profile externally is not straight, but slightly curved outward at the base. The local stone is dry-built in carefully laid regular courses. Its entrance is a small rectangular opening facing the sea on the west side.
Internally the circular courtyard is 20 ft diameter at ground level. The walls average 15 ft thick at the ground and the inner face is vertical, the thickness tapers towards the top on the outside. The upper part of each wall is hollow, spanned at intervals by flagstones forming galleries. There is a stair within the wall having a width of 3 ft which ascends spirally to the wall top. It seems unlikely that the broch was roofed. The date of construction is unknown but it is possiblethat the broch existed in the first century AD. Brochs are always found near arable land and seldom far from the edge of the sea. They comprise strong towers capable of passive defence but are in no sense offensive structures. Their purpose seems to have been to provide refuge for peaceful cultivators in the face of attacks from seaborne forces.
The point of embarkation on the mainland is via the 200 ft long, 15 ft wide masonry Sandsayre Slip, with a slope of 1 in 27 and external batters of 1 1/2
in. to 1 ft, designed by D. & T. Stevenson in 1854.
R Paxton and J Shipway, 2007.
Reproduced from 'Civil Engineering heritage: Scotland - Highlands and Islands' with kind permission from Thomas Telford Publishers.
