Reasons for Designation
For several millennia the western part of the South West Peninsula, namely
Cornwall and West Devon, has been one of the major areas of non-ferrous
metal mining in England. It is defined here as prospecting, extraction,
ore processing and primary smelting/refining, and its more important and
prolific products include copper, tin and arsenic, along with a range of
other materials which occur in the same ore bodies. Throughout much of the
medieval period most of the tin was extracted from streamworks, whilst the
other minerals were derived from relatively shallow openworks or shafts.
Geographically, Dartmoor was at the peak of its importance in this early
period.
During the post-medieval period, with the depletion of surface deposits,
streamworking gradually gave way to shaft mining as the companion to
openworking methods. Whilst mining technology itself altered little, there
were major advances in ore processing and smelting technologies. The 18th
century saw technological advances turning to the mining operations
themselves. During this period, Cornish-mined copper dominated the market,
although it was by then sent out of the region for smelting. The
development of steam power for pumping, winding and ore processing in the
earlier 19th century saw a rapid increase in scale and depth of mine
shafts. As the shallower copper-bearing ores became exhausted, so the mid
to late 19th century saw the flourish of tin mining operations, resulting
in the characteristic West Cornish mining complex of engine houses and
associated structures which is so clearly identifiable around the world.
Correspondingly, ore processing increased in scale, resulting in extensive
dressing floors and mills by late in the 19th century. Technological
innovation is especially characteristic of both mining and processing
towards the end of the century. In West Cornwall, these innovations relate
chiefly to tin production, in East Cornwall and West Devon to copper.
Arsenic extraction also evolved rapidly during the 19th century, adding a
further range of distinctive processing and refining components at some
mines; the South West became the world's main producer in the late 19th
century.
From the 1860s, the South West mining industries began to decline due to
competition with cheaper sources of copper and tin ore from overseas,
leading to a major economic collapse and widespread mine closures in the
1880s, although limited ore-extraction and spoil reprocessing continued
into the 20th century.
A sample of the better preserved sites, illustrating the technological and
chronological range, as well as regional variations, of non-ferrous metal
mining and processing sites, together with rare individual component
features, are considered to merit protection.
Betty Adit tailings works survives well and represents a good example of a
20th century tin reprocessing site. At one time there were many tailings
works associated with the Cornish tin industry, but most have been destroyed
by later activity. The tailings works at Betty Adit is essentially complete
apart from the loss of its machinery and enough remains to be able to read
the whole dressing process.
Details
The monument includes a 20th century tin tailings works known as Betty Adit
or Brea Adit together with an earlier leat and reservoir associated with the
nearby Dolcoath Mine. The tailings works is situated on a revetted terrace
immediately above and west of the Red River. The site lies within the
Cornwall and West Devon Mining Landscape World Heritage Site.
The visible remains are mainly associated with the 1920s tailings works and
include a series of buddles, frames, settling pits and concrete machine
plinths. The Robert Symons' map of 1850 shows a building and the Dolcoath
leat in the area. An Ordnance Survey map for 1880 depicts the leat and a
reservoir where the building once stood. The 1907 Ordnance Survey map
illustrates a radical change in the level of activity within the area, with
the appearance of the large primary settling tanks and a series of
interconnected leats and channels. The next available Ordnance Survey map
dates to 1967-75, shortly after the works were abandoned and shows less
detail than is currently known to survive.
The visible remains are considered to relate to the period of working between
1928 and 1962 carried out under the name Brea Tin Streams by Ewart Bawden. No
trace of the 1880s Dolcoath leat and reservoir are visible on the site; but
because the area has seen considerable build up of material they will survive
below the later deposits. Tailings works were built downstream of most of
the major Cornish mines and were built to reprocess wastes from their larger
neighbours. They are essentially independent dressing floors involved solely
with the extraction of black tin (cassiterite) from material that had already
been processed on at least one occasion. The works rely on water for
dressing purposes and the actual processing was carried out using a series of
interconnected settling tanks and buddles.
At Betty Adit, a complete set of tanks, round frames and buddles of different
types survive together with machinery plinths, leats and channels. The raw
material entered the works in suspension and flowed into the primary settling
tanks in the southern part of the monument. From here it passed through a
series of buddles, frames and smaller tanks until by the time it reached the
lower northern part of the site much of the tin had been removed.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
