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.
The reverberatory lead smelt mill was developed in the late 17th century, and
marked an important stage in the development of the switch from wood to coal
fuel which rendered the Industrial Revolution possible. The reverberatory
smelt mill was a rectangular enclosure of stone or fire brick held by iron
strapping, within which ore was smelted by the heat of the flames from a
separate coal fire in one end reflected down onto the ore by an arched roof.
The separation of fuel from ore made the use of coal possible. A chimney at
the far end of the fire provided the draught to draw the flames over the ore;
no air blast was used and, consequently, water power was not required. Early
reverberatory lead smelt mills consisted simply of a large barn like building
containing the furnaces with chimneys projecting from the outer wall. Late
18th and 19th century smelt mills were often large complexes containing
several smelting furnaces, together with slag hearths for extracting lead from
the slags, roasting furnaces for extracting silver from the lead by a process
known as cupellation, and reducing furnaces for recovering lead from the
residue 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. Reverberatory smelt mills will also contain
fuel stores and other ancillary buildings.
Reverberatory smelt mills existed in all the lead mining fields of England,
and also in some coastal areas, using imported ores; about 100 sites are
believed to have existed. Since both the buildings and the sites of
reverberatory smelt mills are more easily re-used than those of ore hearth
smelt mills, well preserved examples are nationally rare.
All early sites with any structural or earthwork remains and all later sites
retaining a range of structural and/or earthwork features, together with any
sites believed to retain the remains of furnaces, whether as exposed ruins or
as buried stratigraphy, will merit protection.
Although much of the Allen smelt mill has been levelled, the remains of
significant structural elements survive, including a condensing chamber,
several flue openings and other related buildings. The associated system of
flues is considered to be one of the best preserved in England; much of it is
intact and retains important access ramps and openings for cleaning. The
survival of the two terminal chimneys enhances the importance of the monument.
Details
The monument includes the remains of part of an ore hearth smelt mill and a
reverberatory smelt mill, as well as the extensive system of flues which
includes two chimneys, several ramped access ways and part of a contemporary
trackway. It is in six separate areas of protection. The smelt mill is
situated on the valley floor on the south side of the River East Allen; the
flues emerge from the rear of the smelt mill and run in a south westerly
direction to the open fells above, terminating in a stone built chimney near
the watershed at Flow Moss approximately 3.5km away.
Ore smelting in Allendale is well documented and a smelt mill is recorded in
AD 1692 which belonged to the Bacon family. During the 18th century the smelt
mill was leased from Sir William Blackett by Lancelot Algood who used it to
smelt ore from his Alston Moor mines. From 1786 the mill was owned by the
Beaumont Company which, during the 19th century, carried out improvements to
the smelt mill. In 1847 a document and an accompanying plan of the mill shows
that there were five roasting furnaces, eight ore hearths, a refining furnace,
two reducing furnaces, two calcining furnaces, two reverberatory furnaces, one
slag hearth and a separating house with 18 pots. The Allen smelt mill ceased
production in 1896.
Much of the smelt mill has been levelled, but a broad retaining earthen bank
at the rear of the smelt mill site contains the remains of several stone
structures revetted into the slope. Some of these structures are interpreted
as the remains of a series of bouse teams located either side of the main
flue; they are visible as stone walls standing 5m high with buttresses forming
the individual bays. Some of the other structures contained within this area
include the remains of a condensing chamber and a flue opening. The flue
opening consists of a stone arch 1.5m high and 1.5m wide and a tunnel which it
is known runs for some distance into the slope; side flues run to the east and
west of the main flue. The smelt mill originally extended over a larger area
down to the river. Only that area in which significant archaeological remains
are known to survive is currently included in the scheduling. A structure
lying on the north side of the smelt mill complex and known as the Pattinson
Building still stands. It was a 19th century silver smelter in which silver
found in association with the lead was refined. The ground level flues, which
run between the smelt mill furnaces and their chimneys, were constructed
during the 19th century. Their prime purpose was to condense the noxious fumes
produced from the furnaces; the deposits, which formed as a result of this
process on the internal walls of the flues, were periodically removed and
their lead and silver content retained. Before the development of ground level
flues, this valuable silver deposit would not have been recoverable. The smelt
mill flues also removed the noxious gases away from settlements within the
valley to a more remote area. Work on the flues is thought to have taken place
in at least two separate phases. The first flue, which was begun in 1808, runs
from the south end of the smelt mill and follows the south side of the B6295
before turning west towards Cleugh Head where it originally terminated. On
construction of the second flue in 1853 it is thought that the first was
extended south and then south west to Flow Moss. The second flue emerges from
the south western side of the smelt mill and crossed over the adjacent road on
what is thought to have been a bridge; on the western side of the road there
is a substantial flat topped platform some 6m by 18m which is interpreted as a
structure associated with this bridge. The flue continued south west on a more
direct route to the chimneys on Flow Moss. The remains of the flues are
visible in various forms: where they survive intact they are visible as linear
mounds up to 8m wide standing to a maximum height of 2m. Internally, they
comprise an arched structure constructed of square masonry which also lies
below ground level for some 2m to 3m. Where the roofs and upper levels of the
flues are no longer intact they are visible above ground level as a ditch on
average 2m wide and 0.5m deep, flanked by two parallel mounds 2.5m to 3m wide
and standing up to 1m high. In some areas the upper parts of the flue walls
have become spread to form an earthwork on average 10m wide.
The remains of at least seven doorways giving access to the interior of the
second flue are visible in its upper 2km. These entrances would have given
barrow access to remove the condensed lead and silver from its walls.
Each of these access points is visible as a hollow road up to 4m wide and as
much as 17m long, which generally runs parallel with the flue. The road ends
in a concave walling and a ramped entrance into the flue. One of the ramped
access points near to Frolar Meadows is unusual in lying at right angles to
the flue, which at this point is also flanked by a trackway, thought to be
an original access route. Only those parts of the flues which survive well are
included in the scheduling.
There are two chimneys on Flow Moss. The most southerly chimney, into which
both flues pass, has undergone consolidation, and is visible as a well
preserved structure 7m in diameter. It is built of regular sandstone blocks
and was formerly higher than its present 6m. There are two arched flue
openings at its square base with the remains of mortice holes. A fragment of a
central dividing wall is visible within the chimney. The most northerly
chimney, approximately 40m north of the first, stands 25m high and 4m in
diameter, and contains a single arched flue opening; the earliest flue
bypasses this chimney in favour of the second, although traces of an earlier
course to it are visible as a slight earthwork.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
