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.
Stone Edge smelt mill is one of the best preserved examples in England of
a reverberatory smelt mill, retaining the overall layout of smelt mill,
slag hearth, condensing flue and chimney, and slag-washing area. The site
demonstrates the development of a large smelt mill complex through the
later 18th and earlier 19th centuries, and is expected to retain
considerable below ground stratigraphic remains of its early phases. The
chimney is thought to be the earliest free standing industrial chimney in
England. The site is of amenity value since it lies in a prominent
location beside a road and is crossed by a public footpath. The chimney is
a prominent landmark.
Details
Stone Edge lead smelt mill is a well-preserved example of a reverberatory
or `cupola' smelt mill. The monument includes the smelt mill itself, a
condensing flue and chimney (for recovering lead fumes), and a millpond to
supply water to power the bellows for the slag hearth of the smelt mill.
The smelt mill used reverberatory or `cupola' furnaces to smelt the lead
ore. These heated the ore from a separate fire within the furnace, and
used natural draught for their airflow instead of relying on mechanical
blast. The slags from the furnaces contained appreciable quantities of
lead which was extracted by crushing and washing, followed by resmelting
in a slag hearth (a shaft furnace fuelled by coke and blown by water
power.
The southernmost feature of the site is a millpond and dam, which held
water to power the bellows of the slag hearth. To the north west of
this stands the square chimney, which is perhaps the oldest surviving
industrial chimney in England and is included in the scheduling. Around
the chimney lies a complex system of flues, surviving as underground
tunnels. The extensive ruins of the smelt mill itself lie east and north
east of these features; it is known that the smelt mill was rebuilt at
least once. A masonry-revetted mound, approached by a ramp from the west,
formed the loading ramp for a `Spanish' slag hearth (an improved type of
shaft furnace).
To the north of these features, the remainder of the site is occupied by
tips of slag and the earthworks of tanks, forming the remains of the
washing floor where slags were crushed and washed to extract entrapped
lead.
The smelt mill was built around 1770, and a slag hearth was added in the
early 19th century. A Spanish slag hearth added by 1850 was the earliest
in England. The smelt mill closed around 1860.
The scheduling excludes all modern boundary walls and a modern track
across the northern part of the site, but the ground beneath these
features is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
