Reasons for Designation
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 ores occur in a variety of forms
across England, giving rise to several different extraction techniques,
including open casting, seam-based mining similar to coal mining, and
underground quarrying, and resulting in a range of different structures and
features at extraction sites. 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 into malleable wrought 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. A comprehensive survey of the iron and
steel industry has been conducted to identify a sample of sites of national
importance that represent the industry's chronological range, technological
breadth and regional diversity.
Bloomery furnaces were typically small structures, no more than 2m in
diameter and height. They needed repairing after every smelt and were
usually rebuilt on a regular basis, frequently in a slightly different
location. String hearths, where the smelted metal was reheated for forging
and reworking, were similar in construction but different in design, for
instance lacking holes for running off molten slag. Those at Low Forge in
the early 17th century are known to have used water wheels to operate
bellows to provide an air draft for the furnaces. Excavation of similar
sites elsewhere nationally has shown that bloomery sites normally retain
remains of a sequence of furnaces buried in debris and waste slag.
Important remains of medieval and early post-medieval iron working are
thus expected to be preserved beneath later deposits at Wortley Low Forge.
The survival of documentary evidence for these early iron works at Wortley
adds to their importance.
Forges were iron works where iron was reheated and hammered to change its
internal structure and chemical composition. Finery hearths were used to
rework cast iron, which being crystalline in structure is brittle, to
convert it into malleable wrought iron. This was then repeatedly reheated
in a chafery hearth and hammered to remove carbon and other impurities and
to further improve its structure. These hearths were initially similar to
the string hearths associated with earlier bloomeries, but were developed
and refined over time. Puddling furnaces were one such development
invented by Henry Cort, a friend of James Cockshutt of Wortley, in the
1780s. Using coke rather than charcoal, iron was heated until just molten
so that most of the impurities formed a liquid slag with the iron being
reduced to a mass of sticky fibres. These fibres were then gathered
together into a ball that could then be removed from the furnace and
hammered to form wrought iron.
Rolling mills were used to shape blocks of wrought iron or steel into
plate, rods or bars of various cross-section such as rails. The iron would
be heated and then passed back and forth between shaped rollers until the
desired shape was produced and then sawn or cut to the desired length.
Initially typically powered by water wheels, rolling mills were often
converted to steam power in the 19th century. Usually as part of any
rolling mill, there would also be workshops for producing and maintaining
the shaped rollers.
Low Forge is nationally important for its long history and wide range of
features, including both those that are upstanding and visible, as well as
earlier structures thought to be buried in later deposits. Its association
with Top Forge (SM 29920), together with the extensive contemporary
documentation for the works, also adds to the monument's importance, as
does its association with the former site office and workers housing. The
survival of an early water powered hammer and a set of puddling furnaces
is of particular note.
Details
The monument includes the standing, earthwork and associated buried
remains of an iron forge which operated from the mid-17th century until
final closure in 1929. It also includes the buried remains of an earlier
iron works that predated the forge which included bloomeries, (furnaces
used for smelting iron from ore). Wortley Low Forge is sited on a river
terrace within a loop of the River Don, which lies to the west. It was
operated as part of a wider complex of forges and plants built along the
upper River Don. One of these, Wortley Top Forge, 550m to the north east,
is scheduled as a separate monument (SM 29920).
Medieval records suggest that iron was worked in Wortley from at least the
14th century. A surviving deed dated to 1621 documents a long established
iron works at Low Forge. It records a complex water powered works with
both bloomery and string hearths, furnaces for smelting iron from ore and
for reheating the metal respectively, which annually consumed 200 tons
(204 tonnes) of charcoal from local woods. During the English Civil War,
Wortley was in Royalist hands and is believed to have produced canon
balls, three of which were found at Low Forge in 1868. By 1658 the
bloomeries had been rebuilt as a forge, with a second forge also in
operation at Top Forge. From this date until the mid-18th century, the
Wortley forges were operated by the Spencer Syndicate, a complex network
of partnerships which monopolised the iron trade in Derbyshire, Southern
Yorkshire and Lancashire with controlling interests in at least 10
smelting works and 17 forges. Surviving accounts between 1695 and 1702
show that Top Forge operated as a finery, reworking pig iron from blast
furnaces. The resulting part-worked blooms of wrought iron were then
reworked in chaferies at Low Forge to produce bar iron, typically
producing 3 tons (3.05 tonnes) a week. Most of this was then taken half a
mile (800m) upstream of Top Forge to the Slitting Mill where the bars were
converted into rods which were mainly sold to nail makers in Mortomley. In
1713 there was extensive rebuilding at both Low and Top Forges, with the
installation of a new water powered hammer at Low Forge. In the mid-18th
century the Spencer Syndicate broke up and the Wortley forges became an
independent concern known as Wortley Ironworks in the control of the
Cockshutt family which also had interests in the South Wales iron
industry. Around this time the works extended up and down the River Don
with the Old and New Wire Mills and the Tilt Mill (the old Slitting Mill)
upstream from Top Forge and the Tin Mill downstream from Low Forge. Bar
iron from Low Forge either went upstream to become rods or wire or
downstream to the Tin Mill to be rolled into thin plates which were used
to make items such as shovel blades. Sometime after 1787, Low Forge was
equipped with puddling furnaces which, by keeping the furnace fire and
iron separate, allowed the production of high quality wrought iron using
coke instead of charcoal. In 1825 there was a further extension at Low
Forge with the installation of a new rolling mill. Ownership of Wortley
Ironworks changed again in 1849 and, soon after, a beam steam engine was
installed at Low Forge to power the rolling mills and other equipment,
although the tilt hammer used with the puddling furnaces remained water
powered. The works contracted down to just the Low and Top Forges in the
late 19th century with Low Forge specialising in producing relatively
small quantities of high quality bar iron. The market for wrought iron
contracted from the late 19th century onwards with the rise in the use of
mild steel. Top Forge, which had specialised in producing railway axles,
closed in 1908, but Low Forge continued until 1929, with the last bar
being rolled on the 29th November.
The most obvious remains of Low Forge are that of the water powered tilt
hammer installed in 1713. This used a waterwheel to turn a cam shaft which
repeatedly lifted and dropped a large weighted iron hammer against an
anvil. Although the massive timber work of the hammer beam is much
decayed, the water wheel, hammer and mechanism all still survive in situ
along with the massive stone weights. These remains all lie within a
hollow some 30m west of the former forge office. Partly exposed in the
eastern side of this hollow are parts of at least two puddling furnaces
that appear to extensively survive as buried remains. To the west of the
hammer there are further structural remains of the forge including
mountings for the beam engine installed in the mid-19th century and the
pit for the water wheel that it replaced. A plan of the forge in 1916
shows that immediately west of the beam engine was the rolling mill with a
pair of furnaces to the north and a powered saw and shears to the south.
Beyond this, close to the riverbank, was the fitting shop where equipment,
including rollers, were produced and maintained. Just north of this was a
gas powered furnace which was installed in 1917 but never used. Water for
the forge was taken from the Don some 230m north east of the hammer. The
southern half of the stone built weir still survives and is included in
the monument, its northern end having been washed away by the river. Water
was fed from the upstream side of the weir via a leat, known as a head
goit, into a millpond which by 1916 was about 100m long by up to 20m wide.
This millpond has been subsequently infilled following the levelling of
spoil tips to the north of the forge. It is believed that the millpond
would have originally been wider than 20m and elsewhere it has been shown
that such ponds were frequently used for dumping old equipment, tools and
other items. The infilled millpond is thus included in the monument as a
buried feature in its own right, as well as for the buried deposits it
contains. To the south of the hammer there are the partly demolished
remains of a building which was some 50m by 10m. This mainly functioned as
a store but also included blacksmith's and chain maker's workshops. To the
south of this the land has been extensively built up with spoil heaps from
the forge and the earlier bloomery. These spoil tips will retain
technological information about the workings of the site and will overlie
earlier features and so are included in the monument. To the east of the
hammer there is the former office for the forge with a set of workers'
cottages to the south. These are all in domestic occupation and are thus
not included in the monument. To the north west of the office there is a
brick built workshop which was a late addition to the industrial complex.
The building (which is included in the scheduling) still retains some
fittings for a line shaft for powering machinery.
The modern land surface of the monument is significantly higher than would
be expected for the natural land form. This is obvious when viewed from
the riverbank or Forge Lane. It also explains why the fields immediately
to the east of the monument tend to flood whereas the forge site does not.
This raised land surface is a result of centuries of ironworking with
continuous dumping of slag and other waste. Across large areas of the
monument this build-up of deposits appears to be at least 2m deep. Remains
of earlier structures, such as those mentioned in the 1621 deed as well as
earlier medieval furnaces, will survive buried in these later deposits.
Exposed in the trackway immediately to the west of the workers cottages,
are two stone wall lines which do not relate to any structures on the 1916
plan and are thus interpreted as an earlier part of the forge complex, the
majority of which is no longer visible on the surface.
A number of features are excluded from the scheduling: these are all late
20th century and later outbuildings, sheds, walls, fences, stiles, gates
and telegraph poles, and all water troughs and the platforms that they
stand on; however, the ground beneath all these features is included.
Fence lines defining the boundaries of the monument lie immediately
outside the area of scheduling.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
