Details

The monument includes the structural, earthwork and buried remains of the Moss
Dam, situated 3.75km north west of Gunnerside village. The monument lies on a
watershed between the Gunnerside and Swinner Gills, approximately on the 560m
contour above the head of Botcher Gill, within an area of grouse moorland.
The Blakethwaite mines were recorded as part of the Surrender Grant in the
late 1790s. By 1806 the leases were split and the Blakethwaite mine sett
leased separately until its decline in the late 19th century. The Moss Dam
is thought to have been built around 1842 by Messrs Tomlin to supply water to
a hydraulic engine installed in the west workings of Blakethwaite Level, which
had previously been supplied from Sun Hush Dam 1km to the east. The dam, which
was fed by a leat carrying water from East Gill Head, approximately 4km to the
NNW, is also thought to have supplied water to the Blakethwaite Dams, the
subject of a separate scheduling, situated 2.5km to the NNE, and in turn the
Blakethwaite dressing floors and smeltmill, also the subject of a separate
scheduling, a further 1.25km downstream.
In plan the monument is subrectangular with a NNW-SSE orientation, measuring
approximately 270m long by a maximum 120m wide, and includes three adjacent,
broadly rectangular ponds connected by culverts. The ponds are defined by a 3m
high flat-topped earthen bank with gently sloping internal and external faces.
The internal face is retained with a brickwork pattern of edge-laid drystone
masonry. The upper pond measures 60m long by 50m wide and consists of a sunken
area with earthen bank at the downslope end. The middle pond, 150m long by 70m
wide, and lower pond, 55m long by 90m wide, are both entirely enclosed within
the earthen bank.
All timber and wire fencing, on the south and east sides, is excluded from the
scheduling, although the ground beneath is included.

MAP EXTRACT
The site of the monument is shown on the attached map extract.
It includes a 2 metre boundary around the archaeological features,
considered to be essential for the monument's support and preservation.

Source: Historic England

Reasons for Scheduling

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 ore works were an essential part of a lead mining site, where the mixture
of ore and waste rock extracted from the ground were separated (`dressed') to
form a smeltable concentrate. The range of processes used can be summarised
as: picking out of clean lumps of ore and waste; breaking down of lumps to
smaller size (either by manual hammering or by mechanical crushing); sorting
of broken material by size; separation of gravel sized material by shaking on
a sieve in a tub of water (`jigging'); and separation of finer material by
washing away the lighter waste in a current of water (`buddling').
The field remains of ore works include the remains of crushing devices,
separating structures and tanks, tips of distinctive waste from the various
processes, together with associated water supply and power installations, such
as wheel pits and, more rarely, steam engine houses.
Simple ore dressing devices had been developed by the 16th century, but the
large majority of separate ore works sites date from the 18th and 19th
centuries, during which period the technology used evolved rapidly.
Ore works represent an essential stage in the production of metallic lead, an
industry in which Britain was a world leader in the 18th and 19th centuries.
Sites are common in all lead mining areas and a sample of the best preserved
sites (covering the regional, chronological, and typological variety of the
class) will merit protection.

The Moss Dam is an important survival of the formerly extensive water
management system of the Gunnerside Gill lead mining area and contributes
towards the understanding of the development of the mines in the 19th century.

Source: Historic England

Sources

Books and journals
Gill, M C, Gunnerside Gill: Historical Survey, (1995), 42-45
Raistrick, A, The Lead Industry of Swaledale and Wensleydale: The Mines, (1975), 57
Shaylor, A E, Almond, J K, Beadle, H L, Lead Mining and Smelting in Swaledale and Teesdale, (1979), 12
Other
Gill, M C, (1996)

Source: Historic England