Description

The monument comprises a linear earthwork, known locally as a treb dyke, which stretches in an irregular line from just N of Viggay Banks in a NE direction towards Gairsna Geo.

It is one of two such dykes which divide North Ronaldsay into three. About 2.4 km in length, its survival is variable: about 650m survives in several discrete sections as a prominent earthen bank, up to 4m wide and 1.8m in height; for much of its remaining length it is visible as a low bank and as tell-tale humps in the modern dykes; in several places the line is all but invisible, but can be seen as a soil or cropmark on aerial photographs dating from the 1940s.

The date of treb dykes has yet to be demonstrated archaeologically. Muckle Gairstay first appears on a map of 1770. It has been suggested they may date from as far back as the Bronze Age. Later land divisions have respected the line of the dyke.

Local legend attributes this and Matches Dyke to a man who divided the island between his three sons.

The area to be scheduled is a long irregular area between 30m and 35m wide, centred on the line of the dyke, to include the dyke and an area around in which evidence relating to its use and construction may survive, as marked in red on the accompanying map extract. Modern roads and above ground modern structures, such as houses and dykes, are excluded from the scheduling, to allow for their maintenance.

Source: Historic Environment Scotland

Statement of Scheduling

The monument is of national importance because it is a rare instance of a distinctive linear earthwork found in the Northern Isles, apparently prehistoric, which has well-defined field characteristics but is vulnerable to further destruction.

It has the potential to provide information about prehistoric land divisions and, from the buried soil beneath the bank, to provide information from which the prehistoric environment and farming economy can be reconstructed. Its significance is heightened by the fact that it is a prominent landmark feature to which local folklore is attached.

Source: Historic Environment Scotland

Sources

Bibliography

RCAHMS records the monument as HY 75 SE 26.

References:

Lamb, R. G. (1980) The Archaeological Sites and Monuments of Sanday and North Ronaldsay, 9.

Ritchie, A. (1985) Exploring Scotland's Heritage. Orkney and Shetland, 73, No. 35, Edinburgh.

Source: Historic Environment Scotland