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.
Despite being a ruin, Hogget Gill lead smelting mill survives reasonably well
and is a rare example of a late 17th to early 18th century smelt mill which
retains its smelting hearth. The monument contains a variety of integral
components including slag deposits, a wood drying kiln, a wheelpit, launder
supports, millponds, a millrace, a tailrace and an overflow channel, and the
whole complex is a very good example of this class of monument.
Details
The monument includes the late 17th to early 18th century Hogget Gill lead
smelting mill, the mill's water management system, and a wood drying kiln. It
is located on the east side of Hogget Gill approximately 1.3km south west of
Hartsop Hall and includes the remains of a smelt mill with attached wheelpit,
two millponds, an overflow channel, a headrace, the remains of launder
pillars, a slag tip, and a wood drying kiln.
The smelt mill building survives as a rectangular structure of drywalled slate
measuring c.9m by 5m internally with walls up to 1.5m high. There are two
openings; one at the north end of the west wall, the other towards the south
end of the east wall. Internally the building is divided by a cross-wall with
traces of a smelting hearth defined by two upright stones on the north side of
this wall. The outline of a wheelpit is visible on the building's south east
side and traces of an arch in the smelt mill's cross-wall suggest there was an
extension of the wheel shaft to operate a set of bellows in the southern half
of the mill. To the east of the mill there is a circular drystone kiln some 5m
in diameter and up to 1.5m high dug into the hillside with a flue entry on the
downslope side. This kiln was used for drying the coppiced wood as fuel for
the ore hearth smelting process. To the north of the mill there is an area of
slag which has been carried from the the smelting hearth, out through the
opening in the north west corner of the building, to be dumped downhill. The
water supply to power the mill's wheel came from two millponds situated on
higher ground to the south west of the mill. A short leat from the nearby beck
fed a small upper pond and this in turn fed a larger subrectangular lower
pond. At the northern end of the lower pond the earthworks of a mill race can
be traced for 37m towards the mill. Between the end of the mill race and the
wheelpit the water was carried on a wooden trough or launder and the bases of
four stone-built launder support pillars are visible. An overflow channel
carried unwanted water from the larger millpond and flowed down the east side
of the mill building, where it collected water from the wheelpit via a short
leat or tailrace, before emptying into a stream north of the kiln.
Documentary sources indicate that permission to erect a smelt mill was granted
at the end of the 17th century, possibly in 1696. A map dated 1764 shows a
building at the smelt mill site labelled `Old Smelt Mill' suggesting that the
mill had gone out of use by this time, and a survey undertaken in the same
year does not mention the mill but refers to alder and underwood growing on
the land occupied by the mill.
All fence posts and field boundaries 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.
