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.
The reverberatory lead smelt mill was developed in the late 17th century, and
marked an important stage in the development of the switch from wood to coal
fuel which rendered the Industrial Revolution possible. The reverberatory
smelt mill was a rectangular enclosed structure of stone or firebrick held by
iron strapping, within which ore was smelted by the heat of flames from a
separate coal fire in one end, reflected down onto the ore by an arched roof.
The separation of fuel from ore made the use of coal possible. A chimney (or
flue to a separate chimney) at the far end from the fire provided the draught
to draw the flames over the ore; no air blast was used and, consequently,
water power was not required. Early reverberatory lead smelt mills consisted
simply of a large barn-like building containing the furnaces, with chimneys
projecting from the outer wall. Late 18th and 19th century smelt mills were
often large complexes containing several smelting furnaces, together with slag
hearths for extracting lead from the slags, 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. Reverberatory smelt mill sites
will also contain fuel stores and other ancillary buildings. Many of the later
sites used water power to provide the air blast for the slag hearths.
Reverberatory smelt mills existed in all the lead mining fields of England,
and also in some coastal areas, using imported ores; about 100 sites are
believed to have existed. Since both the buildings and the sites of
reverberatory smelt mills were more easily reused than those of ore hearth
smelt mills, examples surviving as well preserved field monuments are very
rare nationally.
All early sites with any structural or earthwork remains, and all later sites
retaining a range of structural and/or earthwork features, together with any
sites believed to retain the remains of furnaces, whether as exposed ruins or
as buried stratigraphy, will merit protection.
Alport smelt mill is of importance primarily for its condensing system, which
is considered to be the most complex example surviving in England, and is
unusually well preserved. The importance of this system is enhanced by the
survival of metallurgical residues adhering to the inside surfaces.
In addition, the slag tip is a well preserved example, affording opportunites
for study of the metallurgy of 19th century lead smelting. The remains of the
smelt mill itself, though not well preserved, are of importance because of
their association with the condensing system and slag tip, and are expected to
retain buried remains of furnaces and slag hearths.
The importance of the whole site is enhanced by its description in a
contemporary textbook of metallurgy (Percy 1870) as an example of good
practice. In particular, this source describes the operation of the condensing
system in detail.
The site is of amenity value due to its location in a National Park.
Details
Alport smelt mill lies in a steep wooded valley cut into the limestone plateau
of Derbyshire, 500m north east of the village of Alport. It is a site relating
to the local lead industry and was in use between 1845 and 1875. It includes
the remains of reverberatory smelting furnaces and Spanish slag hearths (small
blast furnaces for reprocessing the slags to extract more lead), together with
a complex system of flues, condensers and chimney. The whole site was
described in detail in 1870 as an example of contemporary best practice. The
condensing system is particularly well preserved and retains residues
important to the study of lead smelting, but the slag tips and some ruins of
the smelt mill buildings also survive. These latter features lie on the flat
valley floor, while the condensing system occupies the steep hillside to the
south.
The smelt mill itself occupied the west end of the site, and is visible as
slight masonry remains with associated earthwork platforms and a head-race
running from the river; below ground remains of furnaces and Spanish slag
hearths are likely to survive. To the north east, beside the river and east of
an access bridge, a slag tip survives as an east-west earthwork 40m long and
10m wide. The remainder of the area is occupied by a very complex system of
arched, lintelled and tunnelled flues zig-zagging along the hillside and
communicating with several condensing chambers in varying states of survival.
This system terminates at a large stubby chimney, on the hillside south east
of the smelt mill site.
Excluded from the scheduling are the wooden hut and a stone hut beside the
access bridge, although the ground beneath these features is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
