Ancient Monuments

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The Blakethwaite Dams

A Scheduled Monument in Muker, North Yorkshire

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Latitude: 54.4223 / 54°25'20"N

Longitude: -2.1024 / 2°6'8"W

OS Eastings: 393453.9939

OS Northings: 502988.5428

OS Grid: NY934029

Mapcode National: GBR FKR9.MH

Mapcode Global: WHB52.P32M

Entry Name: The Blakethwaite Dams

Scheduled Date: 6 August 1997

Source: Historic England

Source ID: 1015855

English Heritage Legacy ID: 28903

County: North Yorkshire

Civil Parish: Muker

Traditional County: Yorkshire

Lieutenancy Area (Ceremonial County): North Yorkshire


The monument includes the structural, earthwork and undisturbed buried remains
of the Blakethwaite mine dams and includes two areas. It lies in the upper
reaches of the Gunnerside Gill, 6.5km north of Gunnerside village, within an
area of unenclosed 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 to Thomas Chippendale and Co. In 1811 an ore shoot was being worked by
adit and shaft. However it was not until the following year that the
Blakethwaite Level was driven. The company also built a dressing floor, which
is the subject of a separate scheduling, near the level entrance to process
the ore. A second level (Blakethwaite Low Level) was begun in 1814 but
abandoned in 1818. The abandonment may have been partly affected by Clarke and
Co, a Chippendale partner, who took over the lease in that year. Early returns
from the mines encouraged the building of the Blakethwaite Smelt Mill, also
the subject of a separate scheduling, which began smelting in 1821. The lease
was surrendered in 1836 and taken up by Messrs Tomlin (Strands and Co) who
held the lease until Tomlin's death in 1846. The following year a new company
headed by Thomas Bradley took over. The lease again changed hands in the early
1860s, but the mines gradually fell into decline.
The Blakethwaite Dams lie approximately 120m apart and have been built across
a narrow, steep sided gully in the upper reaches of Gunnerside Gill. They are
believed to have been built after 1836 and were in existence by the 1850s.
Bradley and Co were responsible for a major investment in the Blakethwaite
mine sett during the mid-19th century including the development of the water
management system. This period is likely to have seen the construction of the
Moss Dam, situated 2.5km to the SSW, and the feeder leat which carried water
from East Gill Head c.4km southward to the dam. Moss Dam, itself the subject
of a separate scheduling, is believed to have been built to supply water to
the west workings of the Blakethwaite Level where a hydraulic engine was
installed in c.1842, and is also thought to have supplied water to the
Blakethwaite Dams. The Blakethwaite Dams were primarily built to store water
for the Blakethwaite mine dressing floors some 1km downstream to the SSE but
also supplied water to power a hydraulic engine in West Sump c.1837-40.
The upper dam, which is oriented north east-south west and measures 40m in
length, consists of two parallel drystone walls, which average 1.5m wide at
top (the upper wall increases to 2m in width toward the centre), with a
central earthen core averaging 3m wide. The walls have vertical internal faces
and external faces tapering outward with a stepped batter to the base. The
external face of the outer wall is also buttressed by a substantial earthen
bank contained by revetment walls either side of the central area. A square
vertical slot, with two bolt holes and vertical in situ iron bar, cut down
through the upper wall, is thought to form part of the sluicing mechanism. The
crest of the dam is breached at this point. The former pond area behind the
dam is now almost silt-filled, with a flat surface just below dam crest level.
It originally formed a large body of water to the west of the dam, and a
sample area of the floor of the pond is included in the scheduling. The lower
dam, which is oriented NNE-SSW and measures c.30m in length, is of the same
construction though the earthen bank and protruding revetment walls are

The site of the monument is shown on the attached map extract.

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 whole of Gunnerside Gill is an exceptionally well preserved lead mining
landscape, containing a wide range of features. It is well documented
historically from the 17th century onwards. The Gill is accessible to the
public and the archaeological remains form an important educational resource
and public amenity. The Blakethwaite Dams are an important part of the
Gunnerside Gill lead mining landscape and contribute to the understanding of
the 19th century development of the Blakethwaite mines. In addition they
provide evidence for the formerly extensive water management system which
supplied the Blakethwaite dressing floors and smeltmill.

Source: Historic England


Books and journals
Dennison, E, Gunnerside Gill Phase II: Archaeological Survey, (1995), 24
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

Source: Historic England

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