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Black Road causeway, Black Bridge and World War II reservoir at Copperhouse Pool

List Entry Summary

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 Culture, Media and Sport.

Name: Black Road causeway, Black Bridge and World War II reservoir at Copperhouse Pool

List entry Number: 1020400


The monument may lie within the boundary of more than one authority.


District: Cornwall

District Type: Unitary Authority

Parish: Hayle

National Park: Not applicable to this List entry.

Grade: Not applicable to this List entry.

Date first scheduled: 25-Aug-2001

Date of most recent amendment: 17-Dec-2010

Legacy System Information

The contents of this record have been generated from a legacy data system.

Legacy System: RSM

UID: 15564

Asset Groupings

This list entry does not comprise part of an Asset Grouping. Asset Groupings are not part of the official record but are added later for information.

List entry Description

Summary of Monument

Legacy Record - This information may be included in the List Entry Details.

Reasons for Designation

The Hayle Estuary, one of the few natural harbours on the north coast of south west England, was an important focus for trade and the movement of people and ideas in the prehistoric and early medieval periods. The area around the estuary has produced prehistoric artefacts with Irish affinities and, later, some of the earliest post-Roman evidence for Christianity in south west England, again showing strong Irish influences. Trade and religious elements continued with a growth of pilgrimage to European shrines and more locally to St Michael's Mount, but rapid decline set in during the later medieval period as the estuary became choked by silts from tin extraction along the valleys feeding into it. By the early post-medieval period, the estuary was surrounded by dispersed settlement remote from regional and national centres of trade and economic power. This situation changed dramatically from the mid-18th century with the need to service the increasingly industrialised exploitation of tin and copper in west Cornwall. The resulting developments show the considerable extent to which industrialisation restructured earlier economic, settlement and transport patterns, overcoming significant natural difficulties to meet its needs. Extensive quays built from 1740 at the heart of the estuary facilitated the import of coal and other supplies required for the mines. A copper smelter built by Copperhouse Creek in 1758 further stimulated business on the quays. The difficult maritime and land access to and within the estuary was eased in 1769 by constructing the Copperhouse Canal and Dock, and, in the early 19th century, by the Black Road across Copperhouse Creek and by the early development of the Hayle Railway. Blocks of slag, called scoria, from the Cornish Copper Company's smelter, provided a distinctive building material in the rapid growth of the Copperhouse district. In 1779, Harvey's Foundry was established at the head of Penpol Creek, an area later known as `Foundry'. Initially serving local mine needs, it became one of the world's leading suppliers of industrial pumping engines in the early 19th century, a role shared with the rival Copperhouse Foundry which supplanted the copper smelter that ceased operation in 1819. In contrast to Copperhouse, Harvey's drew much of its workforce from nearby villages, tending to build large villas rather than urban housing on its land. Fierce competition over access to quays produced the `South Quay' built by Harvey's in 1819, aggravating the natural problems of estuarine silting. These problems were resolved by impounding Copperhouse Pool and, from 1834, creating the wholly artificial Carnsew Pool as tidally-filled sluicing pools whose waters were directed to the canal, quays and harbour mouth. This complex system maintained the port facility that gave the foundries their national and international role besides serving their regional hinterland. Accompanying this industrial growth, the foundry companies operated as general merchants, developing the necessary storage, cartage and stabling facilities and further stimulating use of the port. From the 1860s, rapid economic decline of the Cornish mining industry undermined the foundries' core business leading to their closure, at Copperhouse in 1869 and Harvey's for heavy engineering in 1903. In the early 20th century Hayle diversified into ship-breaking, light engineering and general cargo shipping, but these also underwent serious decline. The survival of extensive elements from the early industrial development of the Hayle Estuary and their contrasting nature in differing areas contributes much to the distinctive character of Hayle in the present day. These survivals also have a wider significance from Hayle's role as the world's leading supplier of pumping engines in the early 19th century, especially for deep mining, and are of major importance for studies of this formative period of our present industrialised society.

The Black Road causeway and Black Bridge have been little modified and survive well. Their physical survival and documented origins demonstrate clearly the major changes and improvements to the transport infrastructure which the early industrial development required around the Hayle Estuary. In particular they form a tangible illustration of the close economic relationship between the manufacturing sites and the wharfage providing import and export facilities. The scoria block construction of both the causeway and bridge is highly unusual, a good example of the diverse applications of this by-product of the copper smelting industry and part of the distinctive contribution which the Hayle area makes to the national stock of architectural fabrics.


Legacy Record - This information may be included in the List Entry Details.


The monument includes an early 19th century causeway, called the Black Road, across the upper end of Copperhouse Pool, the broad, shallow eastern arm of the Hayle estuary in west Cornwall. Near the centre of the causeway, the Black Bridge carries the causeway over the tidal channel of the Copperhouse Creek. The monument also includes a World War II reservoir impounded against the north east side of the Black Bridge. The Black Bridge is a Listed Building Grade II. The `Black' element in the name of both the causeway and bridge (also known as Sea Lane and Sea Lane Bridge respectively) derives from their facing of rectangular, moulded blocks of very dark, glassy, copper-smelting slag called scoria. Scoria blocks were a by-product from the Cornwall Copper Company's smelter which operated from 1758 to 1819 at Copperhouse, south of Copperhouse Pool. Produced in large quantities, scoria blocks were used extensively for a variety of building purposes during the smelter's operation and for long after it ceased production, providing one of the distinctive architectural features of the area. The Black Road causeway is visible for 197m north west-south east, crossing Copperhouse Pool from an area of raised ground on the south east to the sea wall fronting the north of the Pool. The causeway is up to 17.5m wide at its base, rising up to about 2m high to a flattened upper surface about 10m-11m wide. Within that upper surface the carriageway is now visible as a 4.5m wide gravelled track, but earlier records note its former metalling by scoria waste. The south west side of the causeway is faced by coursed scoria blocks, largely unmortared except for the upper course near the bridge. The scoria facing has a steep slope, called a batter, and rises at least seven courses high beside Black Bridge. The causeway's upstream facing, on the north east side, is almost entirely obscured by accumulated silts and overlying vegetation. At intervals along the causeway, roughly-worked upright granite guide-slabs, variously 0.6m to 1.16m high, stand in pairs, one to each side of the present track, marking the road when the causeway was inundated at high spring tides. Two pairs of such guide-slabs, 37m apart, survive north west of Black Bridge; to the south east of the bridge, only one guide-slab now survives, 50m from the bridge on the south west verge. The Black Bridge is situated south east of the causeway's midpoint and measures 19.3m long overall with a carriageway 4.65m wide. The bridge spans the channel of Copperhouse Creek by two unequal rounded arches separated by a single pier lacking cutwaters. The south eastern arch, 4.75m wide, is lower and wider than the north western, 4.35m wide. This asymmetry reflects an early modification reputedly to allow the boat of the Rector of Phillack to pass beneath the bridge. The abutments also differ: on the south east, the sides of the bridge extend about 2m from the arch before splaying out to the sides of the causeway while the north western abutment splays from close beside the springing of the arch. The faces of the bridge rise from the arches, pier and abutments to flank the carriageway as a parapet up to 1.2m high and 0.5m wide, level over the main body of the bridge but angled down above the abutment splays. The downstream side parapet over the north west abutment follows a course inside that of the abutment, leaving a step on top of the abutment splay. The bridge is faced almost entirely by coursed rectangular scoria blocks, mortared except at lower levels, with scoria blocks also providing the arch-rings and paving across the channels beneath the arches. Limited use of brickwork infills the irregular shapes where blockwork courses approach the curves of the arch-rings. The parapet coping is also of scoria blocks but these are edge-set and moulded to a pointed arch in profile. The carriageway between the parapets now has a rough gravelled surface which breaks over the north western arch to reveal the outer surface face of the scoria block arch-ring. The Black Road and Black Bridge were built during the first two decades of the 19th century to provide more direct access from the Cornwall Copper Company works at Copperhouse to the company's main quay facilities at North Quay; the year 1811 is considered the most likely date of construction, when the company obtained the freehold of North Quay. During World War II, a reservoir north east of Black Bridge was used to store water for emergency fire-fighting purposes, enlarging an earlier, smaller pool formed by sluice gates inserted against the upstream side of the bridge by 1908; similar but earlier sluices may have produced ponding behind the bridge apparent on maps of the 1830s and 1840s. The 1940's reservoir is retained by a small dam immediately behind the bridge's north east face. The dam comprises three large shuttered-concrete blocks, 0.6m thick and 1.6m high, separated by two sluice gate gaps, 1.6m wide and 1m deep, narrowing to slender gaps between the blocks' bases. The reservoir, now partly silted, extends 25m north east from the bridge by up to 24m wide, north west-south east, and about 1m deep. A raised bank diverts the upstream channel of Copperhouse Creek around the north east of the reservoir, only merging with the reservoir close behind the bridge. All modern electricity poles, fittings and cables, all street lighting equipment, and the modern gravel metalling of the track are excluded from the scheduling, although the ground beneath these features is included.

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.

Selected Sources

Books and journals
Buck, C, Smith, J R, Hayle Town Survey, (1995)
Buck, C, Smith, J R, Hayle Town Survey, (1995)
Cahill, N, CAU, , Hayle Historical Assessment Cornwall, (2000)
Cahill, N, CAU, , Hayle Historical Assessment Cornwall, (2000)
Cahill, N, CAU, , Hayle Historical Assessment Cornwall, (2000)
CAU, Cornwall SMR entry PRN 139245,
CAU, Cornwall SMR entry PRN 31974,
DCMS & EH, AM7 & internal core data & reports for CO 987,
DCMS, Listed Building entry SW 5638-5738 9/106,
In conversation on 13/7/2001, Information given in conversation with MPPA, (2001)
In conversation on 13/7/2001, Mr Frank Johns ex Hayle Town Councillor, Information given in conversation with MPPA, (2001)
Title: 1:10000 Ordnance Survey Map SW 53 NE Source Date: 1979 Author: Publisher: Surveyor:
Title: 1:10000 Ordnance Survey Map: SW 53 NE Source Date: 1979 Author: Publisher: Surveyor:
Title: 1:2500 Ordnance Survey Map SW 5637-5737 Source Date: 1970 Author: Publisher: Surveyor:
Title: 1:2500 Ordnance Survey Map: SW 5637-5737 Source Date: 1970 Author: Publisher: Surveyor:
Title: 25": 1 mile Ordnance Survey Map Cornwall sheet LXII: 14 Source Date: 1908 Author: Publisher: Surveyor:
Title: Map of Bodriggy Waste with Indenture of land N of old highway Source Date: 1836 Author: Publisher: Surveyor: In Cornwall Record Office
Title: Ordnance Survey 25": 1 mile Map Cornwall sheet LXII:14 Source Date: 1877 Author: Publisher: Surveyor:
Title: Ordnance Survey 25": 1 mile Map Cornwall sheet LXII:14 Source Date: 1908 Author: Publisher: Surveyor:
Title: Phillack Parish Tithe Map Source Date: 1842 Author: Publisher: Surveyor:

National Grid Reference: SW 56658 38128


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End of official listing