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.
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 enclosed structure of stone or firebrick held by
iron strapping, within which ore was smelted by the heat of 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 (or
flue to a separate chimney) at the far end from 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 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. Reverberatory smelt mill sites
will also contain fuel stores and other ancillary buildings. Many of the later
sites used water power to provide the air blast for the slag hearths.
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 were more easily reused than those of ore hearth
smelt mills, examples surviving as well preserved field monuments are very
rare nationally.
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.
The Snailbeach new smeltmill survives well and is considered one of the best
preserved examples of its type in the country. The remains are unusually
complete for a monument of this type and date and, with the exception of the
hearth itself, much of the internal arrangement of the slag mill is visible,
whilst buried archaeological deposits within the floor of the furnace
structure will provide information on the layout and mode of operation of the
furnaces. In addition, the slag tips form an important source of information
for the scientific study of reverberatory smelting and the importance of the
site is increased by its short working life, with little subsequent
disturbance.
Details
The monument is situated 350m north east of Green Acres and includes the
standing remains (several of which are Listed Grade II) and buried features of
Snailbeach new smeltmill and the earthworks of associated reservoirs and a
transport system.
The smeltmill was constructed in 1862 for the Snailbeach Mining Company, whose
lead mine was located some 0.8km to the south. The mine's former smeltmill at
Pontesford was abandoned in 1863 in favour of this new reverberatory mill; it
possessed totally enclosed furnaces which were able to operate continuously;
and was connected to the mine by railway. A decline in the demand for lead in
the late 19th century resulted in the closure and demolition of much of the
site in 1895, although one hearth was operated for a short period in June
1897.
Much of the layout of the smeltmill complex survives intact and, together with
map evidence from the late 19th century, allows the plan of the site to be
reconstructed. The buildings are situated within a rectangular enclosure,
bounded by rubblestone walls along its south, west and north west sides. The
smeltmill building itself defines the east side of this enclosure and is a
rectangular structure of roughly coursed stone which has been constructed
against a slope on a levelled terrace. It is believed to have originally
housed at least four reverberatory furnaces, a roasting hearth and, at the
northern end of the building, a vaulted chamber which may have been used for
storage. The furnaces were located against the rear wall of the building and
were charged from above, access being provided via a railway track which ran
parallel with the east side of the building. The furnaces themselves have been
removed but their buried remains and those of associated features will
survive.
Five flues which are Listed Grade II and included in the scheduling, are
visible exiting the rear of the mill structure from which they run
independently to an underground condensing chamber where further quantities of
lead would have been recovered from the fumes. This is located approximately
50m south east of the smeltmill structure, and although it has collapsed and
been partly infilled, its buried remains will provide information for its
design and plan. From here, a single flue ran southwards as far as Lordshill
at Snailbeach mine where the fumes were discharged via a chimney. Parts of the
flue have collapsed but, those sections which survive intact within the mine
site are the subject of a separate scheduling.
Although the reverberatory furnace was effective in removing lead from the
ore, the slag was still fairly rich in metal and, during the 19th century, it
was invariably resmelted in a slagmill. The slagmill at Snailbeach, a Grade II
Listed Building which is included in the scheduling, is situated at the
northern end of the enclosure and is now used for storage. It is built of
roughly coursed rubblestone with brick dressings. The interior is divided into
two rooms by two parallel cross walls and the floor of the western room is
considerably lower than that to the east. The hearth which was set within
these cross walls has been removed but much of the internal arrangement
remains visible. The basic slaghearth was of fairly simple construction with
the tapping opening located at the front base of the hearth whilst the
charging door was positioned above the hearth bottom, reached via the higher
level at the rear. The brick flue from the slagmill is visible beyond the
northern end of the smeltmill building, running south as far as the condenser.
Whereas the reverberatory furnace relied on a chimney to provide a draught,
slagmills required a blast, and at Snailbeach this is believed to have been
provided by steam powered fans which were probably located in the eastern half
of the building. To the north east of the slagmill are four small reservoirs
which have been terraced into the hillslope; they are now mostly dry but would
have provided the water supply for a steam engine. Immediately to the north
and north west of the slagmill are several slag tips; these in situ deposits
of process residues will retain important technological information about lead
smelting in the late 19th century and are thus included in the scheduling. The
site was served by a network of railway tracks which transported material from
one process to another, and was connected to the Snailbeach District Railway
via two branch lines that approached from the north east. Buried remains of
the track beds are believed to survive beneath the ground surface and these
are included in the scheduling.
The south side of the enclosure is occupied by the dwelling known as the
Smelthouse, part of which is believed to have formerly served as the site
office. Much of the southern boundary wall to the complex has been
incorporated within its fabric and this, together with the house itself, is
thus excluded from the scheduling but the ground below is included. All fence
posts and the dwelling's associated outbuildings are also excluded, although
the ground beneath these features is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
