Holmbush Mine: Windsor Lane rotative engine house with adjacent boiler house, loadings and platform
Heritage Category: Scheduled Monument
List Entry Number: 1020327
Date first listed: 24-Jul-2002
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The building or site itself may lie within the boundary of more than one authority.
District: Cornwall (Unitary Authority)
National Grid Reference: SX 36117 71930
Legacy Record - This information may be included in the List Entry Details.
Reasons for Designation
For several millennia the south west peninsula has been one of the major
areas of non-ferrous metal mining in England, its more important and
prolific products including copper and tin along with a range of minor
metals and other materials, notably arsenic, which occur in the same ore
bodies. Before the 16th century, exploitation of this region's non-ferrous
metal resources almost exclusively involved tin. Extraction focussed along
valley floors and hillslopes on and around the granite uplands of the
south west where tin ore had accumulated after natural erosion from the
parent lodes. These accumulations were exploited by streamworks, using
carefully controlled flows of water to expose and then concentrate the
ore, leaving behind distinctively deepened valley floors with various
patterns of spoil heaps. By the early post-medieval period, most
substantial deposits susceptible to streamworking had long been exhausted
and exploitation transferred to the mineralised lodes themselves, a change
which marks the appearance of copper as an important product of the south
western mining industry. The early post-medieval exploitation of the lodes
was restricted by the ability to drain the cut, resulting in relatively
shallow workings directly into the lode exposures at the bedrock surface,
often by pits called lode-back pits and sometimes enlarged to form longer
openworks along the lodes.
By the 18th century, ore extraction and processing rapidly expanded to meet growing demands, aided and promoted by technological development. Surface workings became larger and more extensive, and deeper extraction was achieved from shafts, the water pumped from larger mines by early steam engines or drained through near-horizontal tunnels called adits which also served to access the lodes. Horse-powered winding engines lifted the ore from the shafts while larger and more efficient water wheels served ore-processing areas. By such means, west Cornwall became England's main producer of copper in the 18th-early 19th century.
Intensification accelerated in the late 18th-early 19th century with more efficient steam-powered pumping engines allowing deeper shafts from which extensive underground workings spread out. By the mid-19th century, steam also powered winding and ore-processing operations, the engines, boilers and ancillary machinery housed in distinctive masonry buildings grouped around the main shafts and dressing areas. Later in the century, compressed air was used for underground extraction equipment, fed from steam-powered compressors on the surface. Ore-processing became increasingly mechanised, along with the development of more effective methods of separating and retaining different ores, particularly in the production of arsenic which became a major saleable product in the 19th century, adding a further range of distinctive processing and refining components to some mines. With these advances, this area of east Cornwall and west Devon became one of the world's main sources of copper and arsenic ore until the later 19th century, while in west Cornwall, copper ores became exhausted and replaced as that area's main product by the tin ores present at deeper levels.
From the 1860s, the south western mining industries began to decline in competition with cheaper sources of copper and tin ore overseas, especially from South America, leading to a major economic collapse and widespread mine closures in the 1880s, though limited ore-extraction and spoil reprocessing continued into the 20th century.
The Windsor Lane rotative engine house at the Holmbush Mine survives very well, complete with its adjacent boiler house, loadings and platform. Its largely intact built structure, with little collapse and only minor modifications from unintensive 20th century reuse, owes much to it being one of very few 19th century engine houses to have retained a considerable part of its original roof structure into the 21st century. The good body of supporting documentation for this mine allows the development of the Windsor Lane complex to be understood as well as the context for the erection of this engine house within that development. The good survival of this engine house also provides a tangible reminder of the ongoing impact of the 19th century mining boom on settlement patterns, accounting for the development of Kelly Bray, which remains a substantial settlement in the landscape neighbouring this engine house.
Legacy Record - This information may be included in the List Entry Details.
The monument includes an engine house, with adjacent boiler house,
loadings, raised platform and plinth, which powered mid- to later 19th
century winding operations in the Windsor Lane complex of the Holmbush
Mine, north of Kelly Bray near Callington in south east Cornwall. This
complex was part of the wider overall extent of the Holmbush Mine, a
copper, lead and arsenic mine operating mainly during the 19th century but
developed from earlier activity. The engine house in this scheduling is a
Listed Building Grade II.
Mining at Holmbush dates from at least the 17th century. By the 1820s shafts were being sunk on the copper-rich Holmbush Lode in two areas: the eastern, containing this scheduling, occupied the floor and western slope of a narrow valley crossed by Windsor Lane, north west of Kit Hill; the western area, the subject of a separate scheduling, was sited on an adjacent ridge.
Prior to the mid-19th century, the Windsor Lane site formed the chief operational centre for the mine and it remained the focus for ore dressing, administration and service facilities throughout the mine's active life though the principal pumping, winding and access provision transferred to the mine's western area from the 1840s. From the 1830s the mine produced large quantities of copper ore with some lead and silver ore, complemented by arsenic after 1876 which rapidly became its most profitable product. The mine's workforce and supply needs promoted growth of the nearby settlement of Kelly Bray and, from 1872, the East Cornwall Mineral Railway's terminus. The engine house in this scheduling is situated on the valley floor north of Windsor Lane. Rectangular in plan, 8.25m long, NNW-SSE, and up to 6m wide externally, with walls 0.75m-1.12m thick, it survives to full height with the rear gable, about 9.5m high, to the south. It is built of local rubble with brick quoins and arches to most door and window openings. Joist slots mark the levels of the first and second half-floors: three timber joists and some floorboarding remain in position from the first half-floor. The original roof timberwork remains over the southern half of the roof, accompanied by most of its original slate covering in that sector. Internally, behind the tall plug doorway in the north wall, is a large timber beam which secured part of the engine. The beam crosses the cataract pit which is backed by a vertical revetment wall rising to the cylinder bed, with its bedstone in situ, 1.25m across, retaining the iron sleeve of its north eastern cylinder bolt. The engine house finally housed a 30-inch (0.76m) cylinder engine on the mine's closure. Built centrally into, and projecting from, the southern gable wall is the boiler house chimney, rising about 14m, also rubble-built with a projecting brick-built coping ring. A rough hole broken through to the engine house interior from the chimney base is a later alteration.
Extending 7m north of the engine house is a depression 7m wide, crossed by the NNW-SSE masonry and timber loadings for the crankshaft, now reduced from their original height. In an area up to 6m further north, two turf-covered ridges at right-angles to the loadings, with a hollow between them, derive from the arrangements transferring power from the crankshaft.
Beside the east of the engine house and extending beyond it to the SSE is the boiler house with a wider northern antechamber, their interiors slightly sunken below ground level. The antechamber, considered to have been a coal store, is 5.05m long, NNW-SSE, by 4.15m wide internally, with walls 0.85m thick but reusing the engine house east wall for its west side. Its north wall, with a doorway, abuts that of the engine house. Its southern wall has been extensively dismantled and opens to the narrower boiler house, 11.5m long, NNW-SSE, by 2.8m wide internally, appropriate to house a single boiler and with walls 0.6m-0.7m thick but also reusing the east wall of the engine house at the north of its west side. The boiler house and antechamber walls survive extensively to 2.5m high, rubble-built with brick-quoined openings. Extending west from the engine house is a rectangular level platform, 13.5m long, NNW-SSE, by 8.7m wide, merging with ground level on the south side but ending at a straight scarp edged with masonry on the west and north sides, where it is up to 1.5m above the valley floor. The north side of the platform extends 5m beyond the north face of the engine house but is interrupted by a trough and steep slope beside the crankshaft loadings. Beside this trough, the platform supports a rectangular, granite-quoined plinth, 2.6m NNW-SSE, 1.65m wide and 1.6m high; on the east of its upper surface are two studs, 1.1m apart. The rectangular platform is directly aligned on, and midway between, the Wall Shaft to the NNW and the Flopjack Shaft to the SSE. The platform is shown with two parallel walls on the 1883 Ordnance Survey map, considered to be the crank pit where rotative power from the engine house was converted to horizontal motion, driving flat-rods that formerly extended to each shaft.
The development of the Windsor Lane complex, providing the context for the construction and operation of this engine house, is evident from documentary sources and depictions on successive maps and mine drawings. The Stoke Climsland tithe map of 1841 shows the mine's main service buildings on the valley's western lower slope, with two small buildings beside the Wall Shaft on the valley floor. On an 1860s' sectional view of the mine, `Wall's Engine Shaft' was served by an adjacent pumping engine house with boiler house and chimney. From 1861, underground working from Hitchen's Shaft, in the mine's western area, began development along a second copper-rich lode, the Flopjack Lode, to the south of the original Holmbush Lode. The Flopjack Shaft was sunk on this lode from the valley floor at a point 175m SSE of the Wall Shaft. Both the Wall and Flopjack Shafts appear on the 1883 Ordnance Survey map, by which time the pumping engine complex specifically serving the Wall Shaft in the 1860s had been removed and the engine house complex in this scheduling had appeared. By 1883 a roofed dressing floor had also appeared south east of the Wall Shaft, with a tramway to the spoil dumps north east along the valley floor.
In 1876, the Holmbush Mining Company had been formed to extract arsenic ore which, by the early 1880s, had joined copper ore as the mine's chief profitable products. By 1885 the mine achieved its highest annual production of copper ore, but falling ore prices severely diminished its value and greater profits were gained from arsenic production. In the later 1880s the mine became increasingly uneconomic against cheaper ores available from overseas; shaft-mining operations eventually ended in 1892, followed by only limited and intermittent activity during the first half of the 20th century.
By 1906 the Ordnance Survey map shows no evident ore-dressing structures around the Wall Shaft and demolition had begun among the mine's service buildings on the lower slope to the west, marking the start of considerable modification and redevelopment which took place throughout the 20th century over the site of the Windsor Lane complex beyond those features in this scheduling.
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.
The contents of this record have been generated from a legacy data system.
Legacy System number: 15558
Legacy System: RSM
Books and journals
Barton, D B , A Historical Survey of the Mines and Mineral Railways of East Cornwall and West Devon, (1964)
Booker, F, Industrial Archaeology of the Tamar Valley, (1971)
Buck C/CAU, Holmbush Mine Archaeological Assessment, 1998, Unpubl CAU Rept Feature numbers 23-25
Title: 1:10000 Ordnance Survey Map SX 37 SE Source Date: 1980 Author: Publisher: Surveyor:
This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.
End of official listing