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

A Scheduled Monument in St. Martin's, Isles of Scilly

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Latitude: 49.9768 / 49°58'36"N

Longitude: -6.2905 / 6°17'25"W

OS Eastings: 92497.291896

OS Northings: 17344.53241

OS Grid: SV924173

Mapcode National: GBR BXVR.3FZ

Mapcode Global: VGYBR.XV94

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

Scheduled Date: 7 October 1976

Last Amended: 1 August 1996

Source: Historic England

Source ID: 1014789

English Heritage Legacy ID: 15442

County: Isles of Scilly

Civil Parish: St. Martin's

Traditional County: Cornwall

Lieutenancy Area (Ceremonial County): Cornwall

Church of England Parish: Isles of Scilly

Church of England Diocese: Truro


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.

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.

Source: Historic England

Reasons for Scheduling

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'
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
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.

Source: Historic England


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

Source: Historic England

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