Upper Merrivale tin blowing and stamping mills, 750m north of Shillapark

Reasons for Designation

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.

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.

Legacy

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

Legacy System number:

28755

Legacy System:

RSM

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,

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