Prehistoric field system and kerbed cairn, with post-medieval kelp pit and linear boundary on southern White Island


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Scheduled Monument
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Ordnance survey map of Prehistoric field system and kerbed cairn, with post-medieval kelp pit and linear boundary on southern White Island
© Crown Copyright and database right 2019. All rights reserved. Ordnance Survey Licence number 100024900.
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The building or site itself may lie within the boundary of more than one authority.

Isles of Scilly (Unitary Authority)
St. Martin's
National Grid Reference:
SV 92508 17341

Reasons for Designation

The Isles of Scilly, the westernmost of the granite masses of south west England, contain a remarkable abundance and variety of archaeological remains from over 4000 years of human activity. The remote physical setting of the islands, over 40km beyond the mainland in the approaches to the English Channel, has lent a distinctive character to those remains, producing many unusual features important for our broader understanding of the social development of early communities. Throughout the human occupation there has been a gradual submergence of the islands' land area, providing a stimulus to change in the environment and its exploitation. This process has produced evidence for responses to such change against an independent time-scale, promoting integrated studies of archaeological, environmental and linguistic aspects of the islands' settlement. The islands' archaeological remains demonstrate clearly the gradually expanding size and range of contacts of their communities. By the post- medieval period (from AD 1540), the islands occupied a nationally strategic location, resulting in an important concentration of defensive works reflecting the development of fortification methods and technology from the mid 16th to the 20th centuries. An important and unusual range of post- medieval monuments also reflects the islands' position as a formidable hazard for the nation's shipping in the western approaches. The exceptional preservation of the archaeological remains on the islands has long been recognised, producing an unusually full and detailed body of documentation, including several recent surveys. Regular field systems are one of several methods of field layout known to have been employed in the Isles of Scilly from the Bronze Age to the Roman period (c.2000 BC - AD 400); closer dating within that period may be provided by the visible relationships of the field boundaries to other classes of monument with a shorter known time-span of use, or by their relationship with an earlier recorded sea level. They comprise a collection of field plots defined by boundaries laid out in a consistent manner, along two dominant axes at approximate right angles to each other. This results in rectilinear fields which may vary in their size and length:width ratio both within and between individual field systems. The fields are bounded by rubble walls or banks, often incorporating edge- or end- set slabs called orthostats. Within its total area, a regular field system may be subdivided into blocks differing in the orientations of their dominant axes. Regular field systems may be associated with broadly contemporary settlement sites such as stone hut circles. Some regular field systems on the Isles of Scilly contain a distinctive association, rarely encountered elsewhere, whereby certain of their field boundaries directly incorporate or link cairns, entrance graves and cists in some groups of prehistoric funerary monuments. Although no precise figure is available, regular field systems form one of the three principal forms of prehistoric field system, along with irregular field systems and some groups of prehistoric linear boundaries, which survive in over 70 areas of the Isles of Scilly. They provide significant insights into the physical and social organisation of past landscapes and they provide evidence for the wider contemporary context within which other nationally important monuments were constructed.

The layout of this regular field system on White Island survives well, clearly displaying the character of the prehistoric land use organisation and the strong influence upon it of the natural topography. Despite truncation by rising sea levels, the field system contains a sufficient range of elements to determine its character and extent. The direct and sequential relationship of one field system wall with a kerbed cairn is rare and important for our understanding of the development of land use during the prehistoric period. The wider prehistoric land use context of this field system and its relationship to funerary and ritual activity is also demonstrated by the cairn cemetery occupying the island's northern hill, and by the broadly contemporary field system and cairns on Top Rock Hill. The shared perception of topographical elements as significant influences on land use organisation throughout human history is shown well by the close correspondence between the prehistoric field system's northern wall and the post-medieval linear boundary. The kelp pit contained in this monument also survives well, complete with its encircling cobble wall whose original appearance is unusually confirmed by photographic evidence and is now protected by later deposits.


The monument includes a prehistoric regular field system on the western slopes and upper shore of the southern half of White Island, an uninhabited island off the north coast of St Martin's in the Isles of Scilly. One of the field system boundaries cuts across an earlier prehistoric kerbed funerary cairn. A 17th-19th century kelp pit, where seaweed was burnt to produce soda ash, is located within the field system's area near the island's west coast. Adjacent to the north of the field system is the bank and ditch of a post-medieval linear boundary that bisects the island from coast to coast. The prehistoric field system forms the surviving eastern sector of a more extensive field system which occupied the low-lying basin now visible as Porth Morran and which has been truncated by the gradual submergence of the Isles of Scilly. The field system extends across the island's west-facing slopes which rise from the east coast of Porth Morran. For most of its extent the field system's upper limit is marked by the prominent outcrops of a ridge bordering the island's east coast, but beyond the northern end of the ridge, the field system crosses the full width of the island. Immediately behind the coast of Porth Morran, substantial post-prehistoric deposits of wind-blown sand mask the lower parts of many of the prehistoric walls; however some reappear in exposures at the coastal edge and in several cases, where a coastal cliff has not formed, they extend onto the upper shore of Porth Morran itself. The field system is defined by heaped rubble walls, generally 1.5m wide and 0.3m high, frequently incorporating a midline row of contiguous or closely spaced edge-set slabs, averaging 0.4m high but up to 0.8m high. The walls subdivide the field system's area above the coastline into broad strips, generally 30m-50m wide where corresponding sectors of consecutive walls remain unmasked by the wind blown deposits. The northernmost wall is also distinctly stepped in its course to avoid a natural outcrop on the coast of Stoney Porth. The strip walls run directly downslope: north east-south west in the north and veering to east-west in the south. On the east, the field system's northern walls are truncated by the coastal cliff of Stoney Porth; further south, a gap in the ridge outcrops that otherwise delimit the field system is infilled by a slightly curving wall along the saddle above Camper Porth. On the west, some strip walls continue the upper shore of Porth Morran for up to 8m before submerging beneath the beach shingle. At two locations along the western coast, opposite Camper Carn in the south and opposite Chad Girt to the north, the strips are subdivided by transverse walls with edge-set slabs exposed along the slight coastal cliff. A further such wall and adjacent hut circle has been recorded at a lower level on the upper shore of Porth Morran opposite Chad Girt, in an area now beneath the beach shingle. The transverse walls indicate that the upper level of rectilinear plot subdivision in the prehistoric field system equates roughly with the present coastline, while the land above, now the dry land of White Island, formed broad undivided strips of rougher ground. The wall defining the south east side of the field system's northern strip crosses the top of a small prehistoric cairn situated on the crest of the low ridge that forms the island's midline at this point. The cairn has a low turf covered rubble mound 4m in diameter and 0.25m high, adjacent to the south of a small surface bedrock exposure; its upper surface has a circular kerb, 3m in diameter, of spaced boulders, measuring up to 0.4m across, 0.2m high and generally 0.5m apart. The field system wall runs ENE-WSW, crossing the cairn's mound and kerb slightly south of its centre and clearly overriding this earlier cairn. A kelp pit is located in the southern part of the field system's area, 6.5m from the coastal cliff of Porth Morran opposite Camper Porth. The kelp pit is visible as a hollow shaped as an inverted-cone, measuring 1.9m north-south by 1.7m east-west across the top and 0.6m deep. It is lined by heat-reddened granite slabs up to 0.6m across, with one flat slab at the base. The upper edge of the pit is lined by cobbles measuring up to 0.3m across, rising slightly above the ground surface; an early photograph of this kelp pit shows this cobbling formed a distinct wall raised around the kelp pit perimeter: identification of particular cobbles still in place shows that little has been lost but that the surrounding land surface has risen by several centimetres since the photo was taken due to deposition of blown sand. Several heat- reddened slabs are visible in the surface turf, forming a spread extending for 3m north west of the kelp pit. Immediately beyond the northern wall of the field system, a straight bank and ditch form a linear boundary extending 40m north east-south west across the narrowest and lowest point across the island, from Stoney Porth to Porth Morran. The ditch averages 3m wide and 0.25m deep, accompanied along its north west side by the bank, up to 2.75m wide and 0.4m high, apparently formed of peaty deposits dug from the ditch. At the south west end, the bank and ditch extend through the shingle and sand ridge behind Porth Morran, indicating the boundary's relatively recent origin, as too does the upstanding size of the bank despite its insubstantial fabric. The date and function of the boundary, perhaps a fire-break or World War II trenching exercise, are not documented. Its presence parallel to and only 4m-6m north west of the prehistoric field system's northernmost wall denotes the continued human perception of this location and alignment as a significant topographical divide in this area. Beyond this monument, prehistoric land use on the island's north half is almost entirely represented by a cemetery containing various forms of funerary cairn scattered over the flanks and summit of the northern hill, from 50m north west of this monument's linear boundary. A small surviving lobe of the prehistoric field system focussed on Porth Morran extends up that hill's SSW spur, denoting the northern limit of the field system whose eastern sector is contained within this monument. Further broadly contemporary field system remains survive on the north eastern coastal slope of Top Rock Hill, the nearest point of St Martin's, from 300m SSW of this monument and occupying an adjoining basin, in the pre-submergence landscape of Scilly, to the low-lying land occupied by the Porth Morran field system in this monument. That field system is also complemented by a cairn cemetery on the summit plateau of Top Rock Hill.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


The contents of this record have been generated from a legacy data system.

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Books and journals
Arlott, J, Island Camera, (1983)
Thomas, C, Exploration of a Drowned Landscape, (1985)
Over, L, 'Isles of Scilly Museum Publications' in The Kelp Industry in Scilly, , Vol. 14, (1987)
Thomas, A C, 'Cornish Archaeology' in Recent Fieldwork in the Isles of Scilly, , Vol. 14, (1975), 87-94
Pl 158, Betjeman, J and Rowse, A L, Victorian and Edwardian Cornwall from Old Photographs, (1974)
Plate showing Kelp Pit, opposite p 64, Vyvyan, C C, The Scilly Isles, (1953)
Rees, S E, AM7 scheduling documentation and maplet for SI 999, 1975,
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7098, (1988)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7099.01, (1988)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7099.02, (1988)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7116, (1988)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7198, (1988)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7204, (1988)
Thorpe, C/CAU, AM 107s for Scilly SMR entries PRN 7096-7, (1988)
Title: 1:10000 Ordnance Survey Map; SV 91 NW Source Date: 1980 Author: Publisher: Surveyor:


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

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