Reasons for Designation
Nucleated lead mines and smelt mill sites are a prominent type of field
monument produced by the lead extraction and processing industries. Lead mines
consist of a range of features grouped around the adits and/or shafts of a
mine. The simplest examples contain merely a shaft or adit with associated
spoil tip, but more complex and (in general) later examples may include
remains of engine houses for pumping and/or winding from shafts, housing,
lodging shops and offices powder houses for storing gunpowder, power
transmission features such as flat rod systems, transport systems such as
railways and inclines, and water supply and water power features such as wheel
pits, dams and leats. The majority of lead mines are of 18th to 20th century
date, earler mining being normally by rake or hush (a gully or ravine partly
excavated by use of a controlled torrent of water to reveal or exploit a vein
of mineral ore).
Lead smelt mills consist of a range of buildings and structures associated
with the processing and smelting of lead ore. The smelt mill itself, is a
building containing one or more furnaces or ore hearths, a bellows mechanism
for providing draught, and may also include slag hearths for further
processing of smelt waste. A flue extends from the mill to a chimney which
would expel fumes away from the mill site and also allow for the condensing of
lead within the fume on the flue wall for collection and processing. Lead ore
was provided for smelting in a dressed form (separated from waste rock to
create a smeltable concentrate). Ore dressing took place at either the mine
site or the smelt mill. The range of processes can be summarised as: picking
out clean lumps of ore and waste; breaking down lumps to smaller size; sorting
of broken material by size; separation of gravel sized material by shaking on
a sieve; and separation of finer material by washing away lighter waste in a
current of water. 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. Other associated features found at smelt mills include fuel
stores, further processing structures such as condensers and separate slag
hearths, water management works such as leats, dams and culverts, transport
systems, assay houses for testing the grade of an ore, stores, smithies,
offices and housing. Lead ores invariably contain traces of silver and some
larger smelt sites included a silver refinery to exploit this. Lead mining and
smelting sites often illustrate the great advances in industrial technology
associated with the period known as the Industrial Revolution and, sometimes,
also inform an understanding of the great changes in social conditions which
accompanied it. Because of the greatly increased scale of working associated
with the lead industry such features can be a major component of upland
landscapes. A sample of the better preserved sites illustrating the regional,
chronological and technological range of this class of monument is considered
to merit protection.
Keld Heads lead complex displays a wide range of features associated with the
lead exploitation and processing industry. The site is unusual in that there
are well preserved structures of both a mine and smelt mill lying close
together and being worked as a single unit. The monument includes the rare and
well preserved remains of an engine bed at the mine and an ore condenser at
the mill. In the 19th century the smelt mill complex was regarded by
contempories as the most advanced in the country. The mine is the oldest
recorded in Wensleydale and was the richest in the county and with the late
and technologically advanced smelt mill, the site offers important scope for
the study of lead exploitation and its development both locally and
nationally.
Details
The monument includes the remains of the Keld Heads lead smelt mill and
nucleated mine complex situated on the north side of Wensleydale 800m east of
Preston-Under-Scar. It is divided into two separate areas. The mine and
associated structures are located at the foot of a scar and the mill lies 300m
to the north with associated features extending for 250m up the hillside.
The mine complex includes the standing remains of the engine house, chimney, a
further building and the wheelpit. The engine house is a rectangular shaped
stone structure, unroofed and lying partly below road level, and measures 20m
east to west by 10m north to south. Within the building are the remains of the
engine bed which supported the engine used for pumping and winding in the
mine. Connecting rods from the engine passed through an arched tunnel beneath
the road and then down the mine shaft. To the south of the engine house and
sharing a party wall is a further stone building 20m by 10m, thought to be
stables and stores. The chimney lies 20m to the east of the engine house, is
c.2.5m square in plan and is c.12m high. The wheelpit lies 30m to the west of
the engine house and is a narrow stone trough 12m long by 1m wide. It is
mostly cut into the hillside but because of the uneven slope the western part
is built above ground level. The wheel pit held a wheel for winding and
pumping in the mine before it was replaced by the engine.
The remains of the smelt mill lie on a wide terrace north of the mine and
include the footings of the demolished mill building, now mostly buried by
quarry waste. The mill building originally had a rectangular room orientated
east to west, measuring c.20m by c.10m which housed a bellows and water wheel
at the west end, and two ore hearths on the north east wall where dressed lead
ore was smelted. A flue extended northwards from the mill to a chimney on the
hillside above. In 1855 a third ore hearth was added and the mill extended by
the addition of a second room at right angles on the north side of the mill
measuring c.18m north to south by c.10m east to west. This housed two slag
hearths on the south east wall to process the slag from the initial smelting.
A second flue emerged from this later building and joined to the existing one
to form a double flue sharing a central wall which extended northwards for
150m to the condenser house and then continued as a single flue to the
chimney. A further flue emerged from the north of the mill and joined the main
double flue further to the north. The flue was extended in 1855 to a new
chimney over 3km distant at Cobscar as the original chimney had been placed
too close and fumes were not carried away but tended to settle nearby. The
walls of the flue survive intact for most of its length and although most of
it has collapsed some sections still survive as an arched tunnel or a channel
with a stone flagged roof. Only the first 250m of the flue is included in the
scheduling. The condenser house consisted of a stone building and a large
wooden structure to the west and the flue from the mill running between them.
The stone building held a water wheel which provided a draught to draw fumes
from the flue in the wooden structure where heavy material was condensed in
what were known as Stokoe Condensers. Water was passed through the condensers
and emerged at the bottom with lead condensed from the fume held in
suspension. This water was then fed out to stone flagged settling pits from
which lead deposits could be collected for re-processesing. The wheel house
survives as a ruined building, partly built into the hillside, with low walls
measuring c.10m by 5m. The tail race for the water wheel survives as a stone
culvert extending south to discharge into the beck. The settling tanks are
clearly identifiable as a stone lined tank 30m by 10m with a central partition
and sluice at the west end, lying 40m to the south east of the condenser. The
condenser building itself was a wooden structure and no longer survives above
ground level.
A large tank 80m wide lies 250m north of the mill. This was fed by springs and
served as a reservoir. Further becks have been culverted and diverted to
create ponds and to manage the water supply required for smelting and
associated processes.
The peat store stands as a roofed building c.30m south of the mill. It is a
stone rubble structure 18m by 4m and has a corrugated sheet roof. It is two
storeys high with four arched entrances at the front (east face) with square
windows in the upper storey.
Lead was first known to have been mined at Keld Heads from the 12th century
and by the 13th was a prosperous operation which provided lead for the roof of
Jervaulx Abbey. In 1823 the mines were becoming exhausted but a series of long
adit levels were driven deep into the hillside beneath the mill which brought
back prosperity to the mine. The smelt mill complex was built in the early to
mid 19th century to replace that at nearby Preston Mill and was extended in
1855. With the introduction of new equipment and techniques in the mid 19th
century to smelt the large amount of ore, Keld Heads was considered to be the
most advanced in the country. It is known that silver, which occurs naturally
in lead ore, was refined here, although not in large quantities. Towards the
end of the 19th century flooding of the lower levels of the mine increased
pumping costs and this combined with a fall in the value of smelted lead
resulted in the closure of the mine and mill in c.1888. The peat store and
lead mine buildings are Listed Grade II.
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.
