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.
Sargill ore hearth smelt mill survives well and significant remains of the
technical processes are preserved. The surviving remains of shaft-type ore
and slag hearths are of particular importance as they, are on present
knowledge, the best-preserved in England. This type of slag hearth is unusual
for the area. Also present are the remains of the unfinished zig-zag flue
system, another an unusual feature in the Dales. These features form important
survivals of 19th century developments in lead smelting technology.
Details
The monument includes the well preserved standing remains of the Sargill ore
hearth lead smelt mill and associated structures. The monument is situated on
a modified terrace on the north bank of Sargill Beck on Staggs Fell about 2km
north east of Sedbusk.
The smelt mill is believed to have been built in the 1840s, located 340m to
the south east of the mine which produced the lead ore. The lead from the mine
was originally taken to a mill at Summerlodge in Swaledale but, owing to the
transportation costs, a mill was built closer to the mine. The mine and mill
both ceased production in 1870.
The smelt mill building is a rectangular structure 17m by 9m, partly built
into the slope. Although ruined, the front walls stand to a maximum height of
3.95m. Internally the mill was divided into two main areas: the western end
which held a waterwheel and a bellows system and the eastern part in which
the ore hearths were located. The waterwheel stood in a wheel pit and was
powered by water flowing through a channel taken from Sargill Beck
approximately 220m upstream. Only the final 12m of this channel is included
in the scheduling.
In the eastern part of the mill were two ore hearths located against the rear
wall. As well as smelting ore, it appears that the easternmost of the two
hearths was also used for re-smelting slag. This was produced from the primary
smelt which could contain appreciable amounts of lead. Although the remains of
the hearths are obscured by rubble, it is clear that both the hearths were of
a shaft-furnace form, rather than the low hearth type traditional to the area.
Such furnaces were introduced in the 1850s as a development from the Spanish
Slag Hearth, although they were not used exclusively for smelting slag.
Immediately to the rear of the hearths is a narrow chamber which held a
condenser, used to extract lead from the exhaust fumes. To the rear of the
mill are the remains of a stone built flue extending up the hillside for 19m.
This comprised a stone lined vertical sided trench 0.8m wide which is now
open, the original roof covering having collapsed. At the end of the flue is
the remains of a rectangular chimney stack which survives up to 2.4m high.
Immediately north of the chimney is a substantial `V' shaped zig-zig ditch
extending northward for 73m. There are shallow banks formed from spoil
alongside the ditch. This feature is an uncompleted extension to the flue.
The zig-zag shape would create turbulence within the exhaust fumes from the
mill which would allow lead in the fume to be deposited in the flue to be
recovered for re-processing. Attached to the west wall of the mill was a
rectangular room 6.7m by 5.25m, containing a roasting furnace which heated
the ore prior to smelting. To the east of the mill building are two level
platforms which represent processing or storage and loading areas. To the
north of these are two natural gullies, the southern ends of which have been
modified in order to control water supply into the mill complex.
Access to the mill from the mine was provided by a track extending north west
from the mill which still survives.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
