Reasons for Designation
For several millennia the western part of the South West Peninsula, namely
Cornwall and West Devon, has been one of the major areas of non-ferrous
metal mining in England. It is defined here as prospecting, extraction,
ore processing and primary smelting/refining, and its more important and
prolific products include copper, tin and arsenic, along with a range of
other materials which occur in the same ore bodies. Throughout much of the
medieval period most of the tin was extracted from streamworks, whilst the
other minerals were derived from relatively shallow openworks or shafts.
Geographically, Dartmoor was at the peak of its importance in this early
period.
During the post-medieval period, with the depletion of surface deposits,
streamworking gradually gave way to shaft mining as the companion to
openworking methods. Whilst mining technology itself altered little, there
were major advances in ore processing and smelting technologies. The 18th
century saw technological advances turning to the mining operations
themselves. During this period, Cornish-mined copper dominated the market,
although it was by then sent out of the region for smelting. The
development of steam power for pumping, winding and ore processing in the
earlier 19th century saw a rapid increase in scale and depth of mine
shafts. As the shallower copper-bearing ores became exhausted, so the mid
to late 19th century saw the flourish of tin mining operations, resulting
in the characteristic West Cornish mining complex of engine houses and
associated structures which is so clearly identifiable around the world.
Correspondingly, ore processing increased in scale, resulting in extensive
dressing floors and mills by late in the 19th century. Technological
innovation is especially characteristic of both mining and processing
towards the end of the century. In West Cornwall, these innovations relate
chiefly to tin production, in East Cornwall and West Devon to copper.
Arsenic extraction also evolved rapidly during the 19th century, adding a
further range of distinctive processing and refining components at some
mines; the South West became the world's main producer in the late 19th
century.
From the 1860s, the South West mining industries began to decline due to
competition with cheaper sources of copper and tin ore from overseas,
leading to a major economic collapse and widespread mine closures in the
1880s, although limited ore-extraction and spoil reprocessing continued
into the 20th century.
A sample of the better preserved sites, illustrating the technological and
chronological range, as well as regional variations, of non-ferrous metal
mining and processing sites, together with rare individual component
features, are considered to merit protection.
Despite partial reduction of the buildings and limited modification for
use as rough pasture, Wheal Trewavas copper mine 310m south of
Trewavas survives very well. The survival of the western manual capstan
platform is exceptional. The dressing and dumping area is largely
undisturbed and has potential for analysis of the waste, and for the
survival of buried features.
Early 19th century methods and technology for copper extraction,
transportation, and primary processing are well represented. The remains
form a fairly complete and well-integrated complex, with evidence for
development at the site over time. The whole illustrates vividly how
copper mines, often situated on the coast because of the visibility of the
mineral in cliffs, could be adapted to exploit such locations with their
natural hazards and limited accessibility.
Details
The scheduling includes remains of an early 19th century copper mine, Wheal
Trewavas, situated on the south coast of Cornwall, east of Mount's Bay. The
location comprises moderate to steep south and south east slopes, and sheer
cliffs. The two standing engine houses with their detached chimneys, and the
capstan platform at Old Engine Shaft, are Listed Buildings Grade II. The
scheduling also includes later cliff-top pasture boundaries, and remains of a
World War II radar station. Wheal Prosper pumping engine house lies 770m
north west, and is the subject of a separate scheduling.
Wheal Trewavas was a short-lived, though productive, mine documented as
beginning production in or just before 1834 and ceasing by mid-1846 when the
workings beneath the sea were flooded. The most westerly of the two main
shafts, Old Engine Shaft, was active by 1834; the other, New Engine, in 1836.
(In 1879 limited exploration of the east part of the area took place). The
mine exploited four copper lodes and one bearing tin, trending south
east-north west across the coastline. Its underground levels extend beneath
the sea, beyondthe scheduling, where rich copper ore was found. On the land
are earthworks and structures for obtaining ore through shafts and adits
(sloping tunnels), and dressing or preparing it for smelting. Old maps
provide complementary evidence for the complex.
The core of the mine contains a possible openwork or pit to exploit a lode
from the surface, and at least two adits and five shafts. Six or seven more
shafts are known beyond the scheduling, and steam engines draining and
raising ore from shafts within it may have been supplied with water by
launder from a spring to its west.
The Old Engine Shaft is spectacularly sited on a ledge on the cliff top, some
40m below the plateau and 20m above sea level. The ledge is cut into the very
steep rocky slope by up to 4m, and extends to the brink of the cliff, where
walling up to 8m high revets the sites of the capstan, boiler house, and
shaft head. An adit opens from the back of the platform.
The Old Engine Shaft is in fact a pair of adjoining shafts on Trewavas Old
Lode. That to the north is sub-rectangular. Its relationship with the
standing engine house to its south west, which supported a steam driven
pumping engine for draining the mine, suggests that the northern shaft is
earlier. Masonry on its northern side could be the remains of a contemporary
engine house. A platform further north, with a truncated granite chimney on
its western side, is considered to represent a boiler house, and this could
have served an earlier steam engine.
The standing engine house is a gabled structure with three storeys above the
part sunken basement. The walls are of granite, mostly large, roughly coursed
rubble, with massive squared and dressed pieces at corners and openings and
other stress points. Doors and windows are flat-topped. The WNW doorway is
exceptionally tall to ease the movement of machinery around the precipitous
and confined site.
The SSW wall of the engine house bears traces of the roof of the boiler
house, also visible as a platform with rubble walling surviving up to 3m
high. This house extends 8.5m NNE-SSW and an estimated 16m WNW-ESE. Its
rubble stone chimney is sited on the slope above. The connecting flue has
rubble walling, and was roofed with stone slabs, some remaining in situ.
Above the chimney is a rock-cut sub-rectangular yard, perhaps for coal, with
evidence for a structure on its northern side. The yard contains the concrete
footprints of structures associated with the World War II radar station. The
station itself, situated on a prominent spot to the south west, survives as a
concrete base, with traces of walls, openings, and wooden flooring.
To the SSW of the boiler house is the site of a capstan for moving machinery
in the shaft. It has a rock-cut pit for the winding drum and slot for a rope
to the shaft head. There is also a levelled area surrounding the pit where
people circled the drum, turning it by pushing radiating handles. Quarries
west and north west of Old Engine Shaft provided building material for
structures at the mine, and contain evidence of stone splitting methods. The
installation of the Old Engine Shaft and subsequent plant was facilitated by
a levelled and metalled access way. This approaches from the north west,
where it was carried over a hollow on a causeway, the width of which (around
4m) reflects that of the boilers and other loads. The count house where
workers were paid is by the track, on the site of the possible openwork;
parts of its walls are standing. Miners going to and from work, via the
adits, would also have used this route.
Ore brought to the surface at New Engine Shaft for dressing was hauled up the
coastal slope by inclined tramway. Three are visible, each a straight
cutting, with a platform of the type used for a horse whim above it. The
easternmost cuts that on its west; it may have been replaced by the third
following reuse for flat rods. The floors and dumps west of the inclines,
extend south to the sea. Here ore was hand broken and sorted in the open or
under sheds. This area would also have processed ore from other shafts, such
as that to the north on Way Sowan Lode with low walling of an engine house,
as well as New Engine Shaft, thought to be on North Lode. It contains waste
(with variations in size reflecting its treatment); trackways; a tram or
barrow way; and is considered to incorporate other buried remains.
The New Engine Shaft in the eastern part of the mine is also sunk from the
top of the cliffs, though set slightly back from the edge. The ground is
higher and less steep than at the early shaft, but is still cut down some 2m
to accommodate the works. The rectangular shaft here has a slot for a balance
bob to counteract the weight of the pump rods below. The adjoining pumping
engine house is similar to that standing at the Old Shaft. Unusually, it has
no large opening to admit machinery at the rear, due to the proximity of the
cut bedrock there. The opening at the front is round-headed, and the driving
floor retains its cylinder bedstone. The boiler house to the east, visible as
an earthwork, is offset to follow the contour. It is 9.5m long by 2.4m wide
and has a detached granite chimney with string course and collar. Both this
house and a further building platform beyond have retaining walls up to 5m
high on the seaward side. West of the shaft are horse whim and capstan
platforms. By 1844 power was taken from the New Engine by flat rods. These
are thought to have run plant at the Old Shaft, via a cutting through the
mine road, and the eastern tram incline.
All modern fencing, stiles, and notices are excluded from the scheduling,
although the ground beneath these features is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
