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 field system in Great Porth survives reasonably well, clearly displaying
the character of the prehistoric land division. Its extensive survival well
into the inter-tidal zone confirms its long term stability against a
considerable period of submergence. This sector of the field system
complements that at higher levels which survives with the prehistoric
settlement on Heathy Hill, providing an unusually complete view of prehistoric
land allotment across the altitude range into now-submerged levels. This field
system is one of very few inter-tidal survivals on Scilly situated on a shore
facing out from the core of the archipelago. As a result of these factors this
monument is of particular importance for Scilly's contribution to the study of
land-use responses to island environments during the prehistoric period. The
wider contemporary context of this monument and its relationship to
prehistoric funerary and ritual activity is demonstrated by the field systems
and cairn cemeteries on Samson Hill and Gweal Hill. The association of the
abandoned post-medieval quay in this monument with the kelp pit on Heathy Hill
illustrates the main visible surviving elements of kelp-burning, a formerly
major economic activity in the islands' economy.
Details
The monument includes a prehistoric field system surviving on the shore of the
southern half of Great Porth, a rounded bay on the west coast of Bryher in the
Isles of Scilly. The field system incorporates an abandoned post-medieval quay
near the southern end of the bay. The north west periphery of this monument
includes an area below Mean Low Water level.
The field system is defined by walls of heaped rubble and continuous rows of
larger slabs, generally 0.5m to 1m wide and 0.4m high. The walls incorporate
occasional edge-set slabs, called orthostats, commonly 0.5m high; in the field
system's longest wall the orthostats are larger, up to 0.8m high, and are
spaced at intervals along the wall, 2m-5m apart.
The field system contains at least four walls subdividing the gently shelving
shore on ESE-WNW alignments, 18m to 70m apart. Their known eastern and western
extents differ with local variations in thickness of the pebble and sand
overburden on the shore in the centre and north of the scheduling and of
rubble on the boulder shore in the south. However near the centre of the
scheduling, the longest of these walls extends WNW below the present Mean Low
Water level before curving to adopt a south westerly course, rising up the
present middle shore of the Heathy Hill promontory and intersecting another of
the ESE-WNW walls shortly before its limit of visibility on the boulder shore.
On the upper shore in the south east of the scheduling, limited scouring of
the sand cover has revealed two areas of finer subdivision within the larger
scale strips; one includes at least two lengths of walling 7.5m apart on a
NNE-SSW axis, at right angles to the dominant strip axis; the other includes a
curved stagger in a short exposure of ESE-WNW wall.
This field system forms the north eastern continuation of a prehistoric field
system that also survives, with a hut circle settlement, over most of the
adjacent Heathy Hill promontory from 17m to the south west of this scheduling.
This is the subject of a separate scheduling. The nearest prehistoric
boundaries on the promontory share the dominant ESE-WNW alignments found in
this monument, crossed by north east - south west walls running down the
slope. These two areas of the field system's survival reflect relatively low
rates of erosion on the promontory and, despite submergence by rising sea
levels, on the very gently sloping surface of the bay. They are separated by a
zone of active erosion and archaeological destruction where the rising sea
level has reached the steeper gradient along the edge of the promontory. In
addition to the visible remains of the field system, a number of prehistoric
flint artefacts have been recovered from various locations adjacent to the
field boundaries.
In the south of the area of the scheduling, a long-abandoned post-medieval
quay extends 19m north from a point slightly below Mean High Water level at
the southern end of the bay's curve. The quay survives as a broad boulder
wall, 1.75m wide and 0.6m high, built over exposed bedrock on the shore. The
quay is faced along its eastern side by a closely-spaced line of slabs, backed
by a less organised scatter of boulders which has been partly disrupted by
wave action. This quay has been identified as a `small pier' mentioned in 1794
by the local churchman and antiquary John Troutbeck. It is also considered
that the quay will have served as an off-loading point for seaweed to serve a
kelp pit on the northern edge of Heathy Hill, 130m to the west, where seaweed
was burnt to produce soda ash in a local industry practised between AD 1684
and 1835 supplying a vital commodity for the mainland glass, soap and alum
industries.
Beyond this scheduling and the prehistoric field system's adjacent extension
onto Heathy Hill, further broadly contemporary field system remains survive on
the higher lands of Samson Hill and Gweal Hill, from 275m to the south east
and 450m to the north west respectively, giving way to cairn cemeteries about
their summit areas. These archaeological features are the subject of separate
schedulings.
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.
