Details

The monument includes a tin blowing mill, two stamping mills and dressing
floors lying adjacent to the River Walkham. The blowing mill is of drystone
construction with the wall standing up to 1.2m high. The interior of the mill
measures 11.1m by up to 4.5m and access to it was through a clearly defined
doorway in the eastern wall. A mould stone sits next to and north of the
doorway. West of the mould stone and adjacent to the western wall of the mill
is a stone edged rectangular structure which represents a pit in which tin was
probably washed prior to smelting. In the northern part of the building is a
recess which would have held the bellows that provided the air blast for the
furnace. The bellows were powered by a water wheel sitting in the wheelpit
attached to the eastern wall of the mill. The water for the wheel was carried
to the site in a leat leading from the River Walkham and stored in a small
reservoir immediately above the mill building.
The southern eastern stamping mill survives as an irregular shaped building
denoted by large orthostats. The interior of this building measures up to 7.3m
long by 3.5m wide with a substantial recess in the south western corner. A
wheelpit adjacent to the northern wall of this mill was served by water
carried on a well-preserved embankment.
The north western stamping mill lies on the site of the later blowing mill
and was identified during excavations carried out by the Dartmoor Tinworking
Research Group over five seasons from 1991. During this excavation, evidence
for a channel leading from a stamps pit below the later furnace was recovered.
It was not possible to establish the precise character of the building
associated with this mill because the structures in this area had clearly been
remodelled when the later blowing mill was constructed.
Excavations within the blowing mill revealed a well-preserved furnace, which
has since been removed, post holes that had supported the bellows, large
numbers of mortar stones, and considerable quantities of slag and ceramic
material. Work within the south eastern stamping mill revealed the stamps pit
together with a mortar stone still in its original position.
To the north of the blowing mill, four elongated gulleys represent the
site of buddles where the crushed tin was dressed. North of these is a hollow
which represents the site of a small openwork. South of the mills a terrace
with some slight earthworks contains a further dressing floor. West of this
and above the scarp is a granite block into the top of which has been cut a
trough. This stone would have been intended for use as a mould stone but was
never completed.
Above the scarp in the area north of the blowing mill considerable quantities
of slag together with prehistoric artefacts and a rubble spread suggests
earlier activity on the site.
Many of the mould, mortar and other worked stones found during the
excavation now lie south of the south eastern mill.

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.

Source: Historic England

Reasons for Scheduling

Dartmoor is the largest expanse of open moorland in southern Britain and,
because of exceptional conditions of preservation, it is also one of the most
complete examples of an upland relict landscape in the whole country. The
great wealth and diversity of archaeological remains provide direct evidence
for human exploitation of the Moor from the early prehistoric period onwards.
The well-preserved and often visible relationship between settlement sites,
major land boundaries, trackways, ceremonial and funerary monuments as well as
later industrial remains, gives significant insights into successive changes
in the pattern of land use through time.
Blowing mills (also known as blowing houses) survive as rectangular drystone
buildings served by one or more leats and are characterised by the presence of
granite blocks with moulds cut into them - bevelled rectangular troughs known
as mould stones - and on occasion by the square or rectangular stone built
base of the furnace itself. During the medieval and early post-medieval
period, black tin (cassiterite) extracted from streamworks and mines was taken
to blowing mills to be smelted. At the blowing mill the cassiterite may have
been washed a final time before being put into the furnace together with
charcoal. To smelt tin the temperature within the furnace had to reach 1150
degrees C. This was achieved by blowing air through the furnace using water
powered bellows. Once the tin had become molten, it flowed from the furnace
into a float stone and was ladled into the mould stone, in which it cooled to
form an ingot of white tin. The original number of blowing mills on Dartmoor
is unknown, but at least 26 are believed to survive, whilst a further 41 are
known only from stray finds and documentary sources. All examples with a
clearly identifiable surviving structure are therefore considered to be of
national importance.

The Upper Merrivale tin blowing and stamping mills survive well and are known
from excavation to represent an important resource for our understanding of
tin processing. In particular, the southern dressing floor remains essentially
intact and most other structures still contain archaeological and
environmental information.
This site is the only example on Dartmoor where separate blowing and stamping
mills existed adjacent to each other.

Source: Historic England

Sources

Books and journals
Gerrard, S, Greeves, T, Excavation of Upper Merrivale Tin Blowing and Stamping Mill, etc., (1992)
Gerrard, S, Greeves, T, Excavation of Upper Merrivale Tin Blowing and Stamping Mill, etc., (1992), 7-8
Greeves, T, Excavation of Upper Merrivale Tin Blowing and Stamping Mill, etc., (1993), 3-4
Greeves, T, Excavation of Upper Merrivale Tin Blowing and Stamping Mill, etc., (1993), 4-5
Greeves, T, Excavation of Upper Merrivale Tin Blowing and Stamping Mill, etc., (1994)
Other
Gerrard, S. and Greeves, T., Excavation of Upper Merrivale Tin Blowing & Stamping Mill, etc, 1991,
Gerrard, S. and Greeves, T., Excavation of Upper Merrivale Tin Blowing & Stamping Mill, etc, 1991,

Source: Historic England