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.
Medieval lead smelters include a range of features known from field or
documentary evidence. The commonest type is the bole or bolehill, a wind-blown
smelting fire located on an exposed hilltop or crest. This consisted of a
rectangular or circular stone structure, open on one side, within which a
large fire was constructed using large blocks of wood at the base and smaller
wood interleaved with ore above. Boles used the wind to provide draught and
were located on exposed summits or ridges, normally facing south west. The
molten lead was run out by channels on the upwind side into a casting pit or
area. The slags produced by the bole retained considerable quantities of lead.
Some of this could be extracted by crushing and washing the slags and the
remainder could be recovered by resmelting the slag in a smaller enclosed
hearth (the slag hearth or 'blackwork oven') using charcoal fuel and an air
blast normally supplied by hand or foot operated bellows; the resulting black
glassy slag is distinct from the grey or yellow slag produced by the bole
itself.
The bole and associated features were in use from at least the 12th to the
late 16th centuries. They are important as the main form of medieval lead
smelting technology, differing markedly from the smelting technology of other
metals. Boles are found on exposed sites in and around the Pennine lead mining
fields; there is also historical evidence for their existence in Shropshire,
but they are not known to have existed in the Mendip or south west England
mining areas. It is likely that around 200 bole sites existed, with smaller
numbers of slag washing sites (sometimes in separate locations from the bole).
The majority of sites are known from place name evidence only; scatters of
slag or visibly contaminated ground are unusual, and sites retaining
informative slag distributions, intact tips, or visible structural or
earthwork features are very rare. All sites with informative slag
distributions, intact tips, or visible structural or earthwork features are
therefore considered to merit protection. It is known that other types of lead
smelter were used in the medieval period. There is documentary evidence for
smelter types known as the 'furnace' in Devon and the Mendips, 'hutt' in
Devon, and 'smelt mill' in North Yorkshire. On the Mendips, most smelting was
undertaken at four central washing and smelting places known as 'mineries',
probably using small open hearths blown by foot powered bellows. There is also
field evidence for an enclosed smelting furnace (from the Isle of Man) and a
range of sites identified by scatters of slag (from County Durham). These
field site types cannot yet be fully correlated to the documented site types,
and are a priority for future research. Due to their rarity, all non-bole
medieval lead smelting sites retaining informative slag distributions, intact
tips, or visible structural or earthwork features are considered to merit
protection.
The site at Bole Hill, Totley is an unusually well preserved example of a
medieval lead smelting site, containing visible evidence of at least one bole
and two blackwork ovens, with associated casting channels and pits. The
diversity of features is very rare in England. The site has enhanced amenity
value due to its location on publicly accessible land within a National Park.
The site is one of the best medieval lead smelting sites known to survive in
England.
Details
The monument at Bole Hill, Totley is that of a medieval lead smelting site,
including the bole itself and at least two slag hearths, with associated
casting areas and slag tips. The bole lies on the crest of the ridge,
orientated north-south and open to the west, and measures 7m x 3m externally.
Traces of all three walls are visible. It is connected by casting channels to
an oval casting area measuring c.2m x 1.5m. This may have been reused by a
slag hearth immediately south of the bole. The main blackwork oven (a medieval
slag hearth) lies c.50m north of the bole, also on the crest of the ridge, and
consists of an oval area of contaminated ground (measuring c.5m x 3m) with
traces of stonework, connected by channels to two small casting areas. A small
pond c.7m west of the bole has been used for washing slags. The remainder of
the hilltop is occupied by scatters of slag, charcoal, and contaminated
ground.
The lead smelting site at Bole Hill, Totley is likely to have operated from
the medieval period until the later 16th century.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
