Reasons for Designation
Approximately 10,000 lead industry sites are estimated to survive in England,
spanning nearly three millennia of mining history from the later Bronze Age
(c.1000 BC) until the present day, though before the Roman period it is likely
to have been on a small scale. Two hundred and fifty one lead industry sites,
representing approximately 2.5% of the estimated national archaeological
resource for the industry, have been identified as being of national
importance. This selection of nationally important monuments, compiled and
assessed through a comprehensive survey of the lead industry, is designed to
represent the industry's chronological depth, technological breadth and
regional diversity.
Ore hearth smelt mills were introduced in the 16th century and continued to
develop until the late 19th century. They were the normal type of lead smelter
until the 18th century, when they were partially replaced by the reverberatory
smelt mill. The ore hearth itself consisted of a low open hearth, in which
lead ore was mixed with fuel (initially dried wood, later a mixture of peat
and coal). An air blast was supplied by bellows, normally operated by a
waterwheel; more sophisticated arrangements were used at some 19th century
sites. The slags from the ore hearth still contained some lead. This was
extracted by resmelting the slags at a higher temperature using charcoal or
(later) coke fuel, normally in a separate slag hearth. This was typically
within the ore hearth smelt mill, though separate slag mills are known.
Early sites were typically small and simple buildings with one or two hearths,
whereas late 18th and 19th century smelt mills were often large complexes
containing several ore and slag hearths, roasting furnaces for preparing the
ore, refining furnaces for extracting silver from the lead by a process known
as cupellation, and reducing furnaces for recovering lead from the residue or
litharge produced by cupellation, together with sometimes complex systems of
flues, condensers and chimneys for recovering lead from the fumes given off by
the various hearths and furnaces. The ore hearth smelt mill site will also
contain fuel stores and other ancillary buildings.
Ore hearth smelt mills have existed in and near all the lead mining fields of
England, though late 18th and 19th century examples were virtually confined to
the Pennines from Yorkshire northwards (and surviving evidence is strongly
concentrated in North Yorkshire). It is believed that several hundred examples
existed nationally. The sample identified as meriting protection includes: all
sites with surviving evidence of hearths; sites with intact slag tips of
importance for understanding the development of smelting technology; all 16th-
17th century sites with appreciable standing structural remains; 16th-17th
century sites with well preserved earthwork remains; and a more selective
sample of 18th and 19th century sites to include the best surviving evidence
for smelt mill structures, and flue/condenser/chimney systems.
Iron has been produced in England from at least 500 BC. The iron industry,
spurred on by a succession of technological developments, has played a major
part in the history of the country, its production and overall importance
peaking with the Industrial Revolution. Iron ore was originally smelted into
iron in small, relatively low-temperature furnaces known as bloomeries. These
were replaced from the 16th century by blast furnaces which were larger and
operated at a higher temperature to produce molten metal for cast iron. Cast
iron is brittle, and to convert it to malleable wrough iron or steel it needs
to be remelted. This was originally conducted in an open hearth in a finery
forge, but technological developments, especially with steel production, gave
rise to more sophisticated types of furnaces. Iron ore occurs in two main
chemical forms, as a carbonate and as an oxide. The carbonate ores require
calcining (roasting) to drive off carbon dioxide, converting the ore into a
oxide before it can be smelted to produce iron or steel. Calcining also
improves the ore for smelting by driving off water and other volatile
substances, and by breaking the ore into smaller fragments.
Roman signal stations were rectangular towers of stone or wood situated within
ditched, embanked, palisaded or walled enclosures. They were built by the
Roman army for military observation and signalling by means of fire or smoke.
They normally formed an element of a wider system of defence and signalling
between military sites such as forts and camps and towns, generally as part of
a chain of stations to cover long distances. In northern England signal
stations were used in particular to augment the main frontier formed by
Hadrian's Wall. The earliest examples were built between AD 50 and AD 117 for
use during the earliest military campaigns during the conquest period, and
generally took the form of a wooden tower surrounded by a ditch and bank and
possibly a slight timber palisade. After AD 117 towers were usually built in
stone, some on the same site as earlier timber towers. In the mid-4th century
AD more substantial stone signal station were constructed mainly along the
Yorkshire coast. As one of a small group of Roman military monuments, which
are important in representing army strategy, government policy and the pattern
of military control, signal stations are of importance to our understanding of
the period. All Roman signal stations with surviving archaeological remains
are considered to be nationally important.
Despite being roofless, the smelt mill and its associated features survive
reasonably well. The mill is a unique example in the North Pennines of a lead
smelting mill being converted to an iron roasting plant, and the building
retains a considerable number of technological features relating to both
aspects of its use. Additionally, and despite being partly mutilated by
construction of the mill's flue and chimney, the Roman signal station also
survives reasonably well. It formed an important part of the Roman
communication system both across the Stainmore Pass and within the northern
frontier as a whole, and will contribute greatly to our understanding of the
Roman signalling network in northern England.
Details
The monument includes the upstanding remains of Augill 19th century lead
smelting mill, a structure later converted to an iron roasting plant, together
with the earthwork remains of an associated reservoir, leats, a flue and a
chimney, and the buried remains of associated structures known from early
Ordnance Survey maps to have existed on three sides of the smelt mill. Also
included within the scheduling are the earthworks and buried remains of a
Roman signal station situated in an elevated position 300m ENE of Augill
Bridge. This signal station has been partly mutilated by construction of the
smelt mill's flue and chimney.
The smelt mill is located on the east bank of Augill Beck about 50m north east
of Augill Bridge. Documentary evidence suggest the mill was constructed in
1843 by the North Stainmore Mining Company to smelt lead ore raised from
nearby mines. About 1859/60 the smelt mill was converted to accommodate the
roasting of iron nodules found in the local mines. This roasting process drew
off carbon dioxide, giving a somewhat lighter load of magnetic iron oxide to
transport to the blast furnaces. Roasting could have been accomplished using
the former lead smelting hearths, although minor modifications were required
to produce the greater heat required for this process. The mill had gone out
of production by 1894 and was subsequently used as a stable. The roof was
removed about 1949.
The smelt mill is a stone-built two-celled rectangular structure measuring
approximately 25m by 7m with a waterwheel pit located immediately outside the
north wall. Water for powering the waterwheel ran along a header leat, the
remains of which survive as an intermittent earthwork running alongside an
overgrown trackway immediately east of Augill Beck which gave access to the
mines higher up the valley. There are no surface indications of a tail race,
suggesting that water was culverted from the waterwheel back into the beck.
The mill's west wall survives to eaves height while the two gables stand to
their full height. The majority of the east wall was built into the hillside
but the upper courses have fallen in. In the larger northern cell the west
wall has two pairs of windows either side of a central wagon entrance. Four
bays situated along the inside of the east wall are considered to have held
ore smelting hearths. At the back of each hearth are two square-headed
openings; the lower openings provided draught for the hearths while the upper
openings connected with the flue and removed the fumes out of the mill. Blast
for the hearths was provided either by bellows, a fan or a blowing engine,
with the waterwheel being used to power the blowing mechanism. The smaller
cell at the southern end of the building has a ground floor opening in the
west wall with a window above, while the rear east wall contains a partially
blocked wagon entrance. A blocked doorway originally gave access between the
two cells. Internally this smaller cell is divided into two by a wall which
appears to be a later insert.
Ordnance Survey 1st edition maps surveyed in 1859 depict two small associated
structures of unspecified function a short distance to the east and west of
the mill and a small enclosure to the south. Buried features reportedly
visible in the vicinity of the mill during the early 1990s include remains of
lead slags to the north west of the mill adjacent to the beck, and iron
residue to the south west of the mill.
As noted above, the upper holes at the back of the hearths in the mill were
all linked by a flue. This flue runs along the outside of, and parallel to,
the east wall. At a point close to the mill's centre the flues join to form a
single larger flue which runs uphill for approximately 260m to the site of a
chimney, now robbed of stone, the location of which is visible as a slight
depression immediately east of a drystone wall at NY81871470. The flue was
originally stone-lined and is intermittently visible as an earthwork feature
running around the north side of a reservoir. It survives as a linear
depression 2.5m to 5m wide flanked in places by turf-covered stone banks. In
places the flue remains buried, whilst elsewhere parts of it have been
partially robbed for drystone wall construction.
On the hillside above the mill at NY81651462 there is a reservoir measuring
about 80m by 10m. It has been scooped out of the hillside, the west side being
retained by a flat-topped dam 4m wide. The reservoir was fed by a substantial
leat 7m wide by 1.5m deep, probably forming part of an old field boundary,
which enters on the south side. There is no obvious evidence for an outflow
leat downslope to the mill, however, a modern cut in the dam to prevent
ponding may have disturbed the original sluice.
At NY81861469, in an elevated position with extensive views in all directions,
are the earthworks and buried remains of a Roman signal station. Brough Roman
fort, 3km to the west, is clearly visible from this point. Despite some
disturbance by construction of the flue and chimney, the signal station
earthworks measure about 25m in diameter and consist of a circular mound about
8m in diameter with a central depression. The mound is surrounded by a ditch,
bank and outer ditch and is one of a chain of signal stations overlooking the
Roman road over the Stainmore Pass. Limited excavation of the signal
station in the mid-1970s found the mound to be composed of yellow clay. One
large posthole and one smaller posthole were uncovered. On this evidence it
was concluded that two phases of activity were represented, and that there had
been a reconstruction of a central wooden platform about 3.5m square. No
datable objects were found but cut food bones were found in the recut ditch.
All modern field boundaries, fenceposts, gateposts, wooden steps and a stile
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.
