Blowing mill 165m north of Yealm Steps.
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. Tin mining and processing is restricted to Devon and Cornwall. The blowing mill 165m north of Yealm Steps is one of very few surviving examples where the processes taking place can be identified from visible surface remains. The mill will contain archaeological, environmental and chemical evidence relating to its construction, use, the competency of the workforce, longevity, its abandonment and overall landscape context.
This record was the subject of a minor enhancement on 13 November 2015. This record has been generated from an "old county number" (OCN) scheduling record. These are monuments that were not reviewed under the Monuments Protection Programme and are some of our oldest designation records.
This monument includes a blowing mill situated in the valley of the River Yealm on the western bank of the river at the foot of Penn Moor. The blowing mill survives as a rectangular drystone built structure measuring approximately 8.8m long by 3.1m wide internally defined by 0.8m wide and up to 1.7m high walls. There is an entrance with doorjambs on the north east side. The wheel pit is preserved as a buried feature. There are traces of a leat leading towards the western side of the building. Within the interior, to the south west is a recess measuring 1.2m long and 0.9m wide which is the site of the furnace. A single block in front of this feature has four axle bearings cut into it. The interior is largely filled with tumbled stone. There are at least two visible mould stones. The blowing mill is situated within an area of tin stream workings.
Further archaeological remains survive within the vicinity some are scheduled but others have not been formally assessed.