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Summary

A gunpowder factory established in 1844 by George Frean, and remained in use until 1897, when it closed as a result of increasing competition from dynamite and a slump in local mining activity. The production of gunpowder involved combining a mixture of saltpetre, sulphur and charcoal and the buildings in which the different stages of the process were carried out survive at Powder Mills. The process was inherently dangerous and to reduce the chances of cataclysmic explosions, the buildings were situated at a safe distance from each other and each had a flimsy roof which would have allowed any explosion to be carried upwards. Amongst the buildings identified at Powder Mills are: grinding mills; blending mills; incorporating mills; a range of buildings where the gunpowder was broken, pressed, corned, dried, dusted and glazed; and finally charge magazines. The quality of the finished gunpowder was tested using two different techniques. At SX 6377681 a proving mortar, which was used to test the strength of the gunpowder, still sits on a restored carriage. Whilst at SX 62757750 a number of large boulders have been split using a single charge, possibly the result of testing. Within the vicinity of the gunpowder works there are four quarries from which material was derived during the construction of the buildings.

Location

Protected Status

• Scheduled Monument 1016635: Gunpowder factory at Powder Mills, a partially enclosed stone hut circle settlement and round cairn
• SHINE: Earthwork remains of part of the 19th century leat supplying Powder Mills gunpowder factory, as well as a leat and reave on Chittaford Down

Other References/Statuses

• National Monuments Record: SX67NW99
• National Record of the Historic Environment: 442786
• Old DCC SMR Ref: SX67NW/51
• Old SAM County Ref: 921
• Old SAM Ref: 28731(P)
• Ordnance Survey Archaeology Division: SX67NW99

Monument Type(s) and Dates

• GUNPOWDER WORKS (Constructed, XIX - 1844 AD (Between) to 1897 AD (Between))

Full description

Ordnance Survey, 1904 - 1906, Second Edition Ordnance Survey 25 inch Map, 99SW (Cartographic). SDV325644.

'Powder Mills (disused)' shown on early 20th century map.

Royal Air Force, 1951, RAF/540/483, 3048-9 (Aerial Photograph). SDV224087.

Ordnance Survey, 1954, SX67NW (Cartographic). SDV350080.

'Powder Mills (disused)' shown on map.

Brown, T., 1961, Tales of a Dartmoor Village: Some Preliminary Notes on the Folklore of Postbridge, 196 (Article in Serial). SDV238060.

Harris, H., 1968, Industrial Archaeology of Dartmoor, 128-133 (Monograph). SDV149229.

The powder mills were built in 1844 and closed circa 1890, due to the invention of dynamite.

Devon County Council, 1974, Survey of Watermills in Devon: Gazetteer (Report - Survey). SDV83967.

Minchinton, W. E., 1976, Industrial Archaeology in Devon, 26 (Monograph). SDV7016.

A proving mortar for the gunpowder can still be seen from the road. The mills were driven by a leat from the East Dart.

National Monuments Record, 1979, SF1509, 289-292 (Aerial Photograph). SDV346618.

Ordnance Survey Archaeology Division, 1979, SX67NW99 (Ordnance Survey Archaeology Division Card). SDV350197.

(27/09/1979 & 05/10/1979) [SX 627773] Power Mills (Disused) [NAT] (1963 map).
The gun powder mills at Two Bridges were built by George Frean in 1844 and closed in the last decade of the 19th century, due to the invention of dynamite in 1867. Three rectangular wheelhouses and two chimneys remain besides workers' cottages and other buildings which have been adapted to farm use. A proving mortar for the gunpowder can still be seen near the lane from the road. The mills were driven by water from a leat on the East Dart (SX 63898131) which passes under the Cherry Brook in two places (SX 62807739 and 68897706) before discharging into the Brook (SX 63407698) (Harris / Minchinton) SX 62807737 Powder Mills near Higher Cherrybrook Bridge. Scheduled monument No 921.
The leat, six wheel-houses and the other buildings shown on the OS 25" 1885, when the factory was still in use, are virtually the same as those shown on OS 25" 1952, although Harris (1968) says that many buildings have been destroyed. Only one small building at SX 62917765 and a few small ones at Powder Mill Cottages are missing from the 1952 map. The hollow at SX 62767728 is shown water-filled on OS 25" 1885, fed by a leat from the stream at SX 62787785. Possibly this was a reservoir for fighting fires in the mill and three wheel houses between SX 62807714 and 62777735.
Buildings are widespread over about 33ha but the factory is concentrated within 9ha centred at SX 62807730 alongside Cherry Brook (see 1:2500 plan and ground photos). All are now roofless although the majority are in good condition with dressed and mortared stone walling standing to roof level. South of this area are the converted buildings which form the complex of Powder Mills Farm and its cottages with isolated ruined structures.
The ruins and other features are correctly shown on the 1:10.000 MSD, and the 1:2500 plan for record purposes.

Hemery, E., 1983, High Dartmoor, 435-7 (Monograph). SDV249702.

Water-powered mid 19th century gunpowder factory. Built by George Frean of Plymouth. The mills flourished for some decades; gunpowder was in demand for blasting at the large tin mines and quarries, and by farmers clearing enclosures of rock. Gunpowder was made by finely grinding and mixing sulphur, saltpetre and charcoal. The millstones were of hard border rock rather than granite. The efficiency of the finished powder was tested and graded by firing a measured shot from a mortar which is still to be seen. Rows of alder trees planted around the mills provided both a windbreak and wood for charcoal. Workers' cottages were built at a minimum safe distance from the mills. The remains of these houses, known as Sunnyside Cottages, lie beside the original road connecting the mills to the turnpike road. The manager and foreman lived closer to the mills in the terrace of buildings seen from the road. Following the invention of dynamite in 1867 the trade in gunpowder began to decline and twenty years later the mills closed.

Robinson, R., 1983-1984, Survey Drawings of Powdermills (Report - Survey). SDV248162.

Royal Commission on the Historical Monuments of England, 1985, Aerial Photograph Project (Dartmoor) - Dartmoor Pre-NMP (Cartographic). SDV319854.

A detailed survey has been carried out for the surrounding buildings in 1983-4. Copies of survey drawings are in parish file. Powder Mills buildings clearly visible along with the three wheel houses with the leat running through them. Also visible on Royal Air Force 1951 and National Monument Record 1979 aerial photographs.

Greeves, T. A. P., 1985, Steeperton Tor Tin Mine, Dartmoor, 114, figure 4 (Article in Serial). SDV310154.

Plymouth and Dartmoor gunpowder company. The first known proof of gunpowder from these works being sold direct to Dartmoor tin mines is the provision of a 50lb barrel of powder for 18s to Steeperton Tor Mine in 1877.

Griffith, F. M., 1986, DAP/HP, 1-4 (Aerial Photograph). SDV304235.

Department of National Heritage, 1986, Scheduled Monument Consent (Correspondence). SDV248145.

Scheduled Monument Consent granted on 2nd September 1986 for refurbishment of chimney stacks.

Department of Environment, 1987, Lydford, 9 (List of Blds of Arch or Historic Interest). SDV266265.

Ruins of gunpowder mill established 1844. Originally an extensive complex running up the valley with several waterwheels powered by a leat, and with two chimneys. All buildings now in varying degrees of ruin although one chimney survives and three main groups are recognisable of granite rubble with granite lintels, all roofless. Chimney with stringcourse near top and plinth. Covered channel runs downhill from it towards the largest ruinous building.

Royal Commission for the Historical Monuments of England, 1987-1993, Duchy Farms Project Survey Visit, P. Pattison (Report - Survey). SDV350839.

(15/08/1989) The complex remains of a gunpowder works at Powder Mills, situated on both banks of the Chery Brook, bear evidence of substantial change during their short working life. All the principal buildings and features are described below. Most of the information provided by the Exeter City Museums Archaeological Field Unit on a tentative basis as their work is not yet complete. It may be possible at a later date to decide what more of the structures were used for and what processes were involved (information from Mr A Pye of the Exeter City Museum Arch Field Unit).
Most of the buildings are constructed from local quarried stone, mortared into random courses with, occasionally, dressed granite quoins. All measurements given relate to internal area. The roofs were covered by brick-red tiles with a black lustrous glaze; many fragments are strewn about the site.
Water delivered by three main leats A-C, provided most of the power for the various treatment processes.
A: The Powder Mills Leat (SX 67 NW 231) conveyed water from the East Dart River, 2.5km to the NNE. It consists of a flat-bottomed channel, 2.2m wide on average and 0.6m deep, with a substantial bank of earth and stone on the downslope side. It averages 3.6m wide and 0.8m high and in places is revetted with drystone walling.
B: A leat taking water from the Cherry Brook averages 1.5m wide and 0.4m deep; it has a bank 3.5m wide and 0.7m high.
C: A leat leading from the Cherry Brook is of similar form and size to leat B.
Leats A and B supplied water to the 'incorporating mills' G-I on the E side of the Cherry Brook. A number of subsidiary and diversionary leats, controlled by sluices, together with two small reservoirs D-E regulated and distributed water between these mills. The main outflow leat emerged from mill 'I' and crossed the Cherry Brook via a vanished culvert to run on the W bank, possibly supplying other buildings. Leat C fed the mills on the W side of the Cherry Brook and also filled a circular reservoir F.
D: A flat-bottomed sub-rectangular reservoir, 25 by 17m, cut 1.5m into the ground. It was used for temporary storage of water prior to its use in the mills.
E: A small reservoir measuring 19m long, 11m wide and 0.5m deep.
F: A flat-bottomed circular reservoir cut into a slope on the WW and contained around the E by a massive bank, 5.4m wide and 2.2m high; the downslope is revetted by a drystone wall. The sloping internal face is partly lined with stone slabs and incorporates a stepped cascade where leat C enters. A large spoilheap from the excavation lies just to the S. This reservoir was allegedly used as a separate resource to fight fires.
G-I: Three similar structures, each of which has a central wheelpit flanked by identical two-storied rectangular chambers; these originally held machinery which was powered by the wheels. The walls stand to roof level and are between 1.25 and 2.1m thick at ground level reducing to 0.5m on the upper storey; they are built of finely cut massive granite blocks. This construction suggests their use as 'incorporating mills' where the constituents of gunpowder were mixed a hazardous process with high risk of fire or explosion. The wheelpits are between are between 8.2 and 8.7m long and 1.5 to 1.7m wide. Their overshot wheels were supplied by leats running along raised, drystone-revetted launder banks.
J: The three sides of a ruined rectangular building, defined by low stone walls, 0.6m wide and 0.4m high. It survives for a length of 5.0m and retains its S end which is 3.0m wide. It may have been a store for materials processed in the adjacent mills.
K: A rectangular building, possibly a store, badly damaged by a modern farm track. The structure was probably about 5.5m long and 4.0m wide, but only two walls survive- they measure 0.5m wide and 0.4m high.
L: A ruined rectangular building terraced into a slope along its major axis. it measures 8.3 by 2.9m with walls 0.5m thick and 0.6m high; there is an entrance in the S end. A small leat formerly passed under the building suggesting that this may have been a store or magazine for volatile materials.
M: A multi-period structure, covering an area 29.5 by 10.5m, was originally of two rooms with later additions on the N, W and S. There is a flue chamber and flue on the E side leading to a restored chimney similar to that associated with building O.
N: Ruins of a rectangular building measuring 6.7 by 3.9m with walls 0.5m thick and up to 0.7m high. There is an entrance in the W wall. A small leat formerly passed under the building, suggesting a function similar to building L.
O: A building complex consisting of a range of at least eight rooms linked by the remains of two flues to a complete, recently restored chimney. The main block occupies an area 51 by 12m. The ruinous walls and turf-covered foundations are between 0.2 and 2.0m high and generally 0.55m thick. It is possible that this complex contained drying staves for either gunpowder or its ingredients.
P: A multi-phase building group, much of which stands to roof level. It originated as a single rectangular mill chamber, 4.3 by 4.15m, with a wheelpit, 6.0m long and 0.6m wide, along its N side. Its overshot wheel was fed by a leat approaching from the SW which was carried on a raised launder bank. Later, a second chamber of similar size was added on the N side of the wheelpit, forming a mill arrangement similar to mills G-I but with much slighter walls, 0.6m thick. Subsequently three further rectangular structures were added: a loading bay and platform, on the N side of the launder measuring 10.5 by 3.0m; a long structure S of the mill chambers, 20.2 by 4.75m; and another to the N of them 9.8 by 4.6m. There is a fragment of mill grindstone outside the E wall of the range. The extant functions of this mill complex are unknown.
Q: A single-storied rectangular building, of unknown function, measuring 7.25 by 3.9m with walls 0.5m thick and standing to roof height.
R: A rectangular building 14.9m long and 4.4m wide, with main walls 0.5m thick. Inside are wall foundations for supporting a raised floor which may have been used to keep stored materials dry and ventilated.
S: A single-storied rectangular building measuring 4.5 by 3.9m, with walls 0.5m thick standing to roof height. It contains a large limestone table, possibly used for pounding raw materials.
T: A rectangular mill building 10.2 by 5.4m with walls 0.5m thick. At ends the walls survive to roof level but chambers are considerably reduced. Along the S end is a wheelpit, 5.8m long and 1.1m wide which was served by a leat running along the W side of the building.
U: A long range of mill buildings grouped around two wheelpits. The S wheelpit is 7.0m long and 2.0m wide and is flanked by double chambers measuring 4.85 by 4.75m and 5.0 by 4.85m; this arrangement is similar to mills G-I. The N wheelpit has a single chamber to the N, measuring 6.2 by 3.9m. The gap between the wheelpits and chambers was later filled by a two-storied structure, 10.5m long and 4.6m wide.
V: A single-storied rectangular building measuring 5.15 by 3.9m with walls 0.5m thick standing to roof height. Its function is unknown.
W: A single-storied rectangular building of unknown function, measuring 16 by 3.9m with walls 0.5m thick surviving to roof height. A cart shed, 6.2 by 4.9m, has been added to its S end.
Buildings O-W are all terraced into the foot of a steepish slope, with leat C, to the W serving them from above. In places the terracing has created substantial quarry scarps to the W of the buildings.
X: Ruins of a rectangular building measuring .5. by 4.0m, with walls 0.5m thick standing up to 2.0m high. There is a blocked doorway at the S corner.
Y: Three clapper bridges spanning the Cherry Brook and a third crossing a tributary. The first two carried the main access track through the works and comprise long drill-split slabs resting on abutments and piers of large coursed blocks.
Z: A silted channel, 1.0m wide and 0.3m deep, running parallel to the Cherry Brook and close to the E bank. A series of smaller channels, spaced about 2.0m apart and parallel to each other, issue from it at right angles and drain towards the brook. Although resembling drainage gullies, it is possible they may have been connected with a washing process at the works.
A further building not now visible is shown on the 1st Edition 6" OS map at SX 62867704 (1980).
The buildings at Powder Mills Farm, SX 628769, were also part of the original complex, though distanced from the powder making buildings, The long building on the extreme E is the former cooperage and there is also a managers house and a smithy. All are well maintained.
The proving mortar, used for testing the grade of gunpowder, has been placed on a reconstructed base at SX 62797680, adjacent to the modern approach road.

See also SX 67 NW 231 (Powder Mills Leat), SX 67 NW 229 (Workers cottages), SX 67 NW 230 (Powder Magazine) and SX 67 NW 194 (possibly workers cottages) and SX 67 NW 196 and 198 (Leats) (12).

Griffith, F., 1988, Devon's Past. An Aerial View, 108 (Monograph). SDV64198.

The location of the powder mills right out in the middle of the moor was deliberately chosen because of the hazardous nature of the operations. An air view shows the entire layout of this establishment, since the buildings are well spread out to minimise the risk of one explosion setting off others. See extract for further details of the buildings.

Pye, A. R. + Robinson, R., 1990, An Archaeological Survey of the Gunpowder Factory at Powdermills Farm, Postbridge, Devon (Report - Survey). SDV254157.

Physical and documentary survey describes 18 individual structures.

Department of National Heritage, 1992, Scheduled Monument Consent (Correspondence). SDV248154.

Scheduled Monument Consent granted on 30th April 1992 for consolidating existing remains and some rebuilding to prevent further collapse following storm damage.

English Heritage, 1993/1998, Gunpowder Industry; Step 3 Evaluation, Devon 1 (Report - Evaluation). SDV350575.

Pye, A., 1994, An Example of a Non-metalliferous Dartmoor Industry: The Gunpowder Factory at Powdermills, 221-240 (Article in Serial). SDV248175.

Dawson, T. + Hambley, J., 1995, A Survey of the Service and Accommodation Buildings belonging to the Powdermills Gunpowder Factory, Postbridge, 1-3, 14 (Report - Survey). SDV351071.

Survey of the occupied buildings and ruined cottages at Powdermills undertaken in 1995.
Powder Mills include the ruins of a gunpowder mill which were listed on 28th October 1987. Established in 1844 by a Plymouth alderman George Frean. Originally quite an extensive complex of buildings running up the valley with several water wheels turned by water from a leat and with two chimneys. All the buildings are now in varying degrees of ruin although one chimney survives and three main groups are recognisable of granite rubble with granite lintels, all roofless. The chimney is well constructed with stringcourse near the top and plinth. It has a covered channel running downhill from it towards the largest ruinous building. The invention of dynamite in 1867 rapidly superseded gunpowder. And the mills, which employed about 100 men and closed in the 1890s.

Department of National Heritage, 1996, Scheduled Monument Consent (Correspondence). SDV248176.

Scheduled Monument Consent granted on 19th December 1996.

Department of National Heritage, 1996, Scheduled Monument Consent (Correspondence). SDV248156.

Scheduled Monument Consent granted for works concerning consolidation of masonry to buildings 1, 2, 3, 7, 9, 10, 14, 18 at Powdermills.

Bodman, M., 1998, Water-Powered Sites in Devon (Report - non-specific). SDV305931.

Ordnance Survey, 2012, MasterMap (Cartographic). SDV348725.

'Powder Mills (disused)' shown on modern mapping.

English Heritage, 2012, National Heritage List for England (National Heritage List for England). SDV348729.

Ruins of gunpowder mill at Powder Mills. Established in 1844 by a Plymouth alderman George Frean. Originally quite an extensive complex of buildings running up the valley with several water wheels turned by water from a leat and with two chimneys. All the buildings are now in varying degrees of ruin although one chimney survives and three main groups are recognisable of granite rubble with granite lintels, all roofless. The chimney is well constructed with stringcourse near the top and plinth. It has a covered channel running downhill from it towards the largest ruinous building. The invention of dynamite in 1867 rapidly superseded gunpowder. and the mills, which employed about 100 men closed in the 1890s.

Ancient Monuments, 5/10/1972, Gunpowder Factory at Powder Mills (Report - non-specific). SDV248140.

Site visited on 5th October 1972. Powder Mills near Higher Cherrybrook Bridge. Set in a typically secluded valley setting with its buildings scattered and widely spaced for safety. This powder mill built in granite is presumably of 19th century build and usage. Two boiler buildings are present with chimneys and leats, now blocked from the cherry brook. The brook is bridged by a clapper bridge. There are four further isolated granite buildings representing mills on the mill leat which brings water 4 kilometres from the East Dart river. Workers in the mill presumably resided in the powder mill cottages with a tied house at the end of this isolated terrace being reserved for the mill foreman. Cottages at present in occupation.

English Heritage, 9/10/1981, Gunpowder factory at Powder Mills (Schedule Document). SDV350194.

The gunpowder factory at Powder Mills survives well and contains a complete range of buildings and other structures and features associated with the industry. Many of the buildings remain essentially intact, with only the roofs and machinery having been removed. The system of leats and trackways provides useful additional information concerning the character of the factory. The unique survival of the associated proving mortar emphasises the quality of the surviving archaeology. Together with a comprehensive historical background this represents a fine example of a gunpowder production site. The prehistoric settlement and cairn associated with the Powder Mills are of national importance in their own right and contain information relating to the exploitation of the central part of Dartmoor during the Bronze Age.
The monument, which falls into five areas, includes a gunpowder factory, a partially enclosed stone hut circle settlement and a round cairn situated adjacent to the Cherry Brook. The gunpowder factory, which is Listed Grade II, comprises at least 18 buildings involved in the production, storage and management of gunpowder. Many of these buildings contained machinery which was powered by water which was carried to the site by three large leats from the East Dart and Cherry Brook rivers. These are included in the scheduling. A system of trackways link the buildings and the river was crossed by way of clapper bridges. The gunpowder factory established in 1844 by George Frean, was certainly operational by 1846 and remained in use until 1897, when it closed as a result of increasing competition from dynamite and a slump in local mining activity. The production of gunpowder involved combining a mixture of saltpetre, sulphur and charcoal and the buildings in which the different stages of the process were carried out survive at Powder Mills. The process was inherently dangerous and to reduce the chances of cataclysmic explosions, the buildings were situated at a safe distance from each other and each had a flimsy roof which would have allowed any explosion to be carried upwards. Several explosions are known to have occurred at Powder Mills and fortunately these precautions may have ensured that no workers were ever killed. Amongst the buildings identified at Powder Mills are: grinding mills, where the ingredients were crushed separately between horizontal rotating millstones; blending mills, where the ingredients were mixed in rotating barrels; incorporation mills, where the material from the blending mills was mixed further into a single compound; a range of buildings where the gunpowder was broken, pressed, corned, dried, dusted and glazed; and finally charge magazines, where the gunpowder was stored. Further buildings on the site may have been used as storage or office accommodation. The quality of the finished gunpowder had to be tested and at Powder Mills this appears to have been carried out using two very different techniques. At SX 63777681 a proving mortar, which was used to test the strength of the gunpowder, still sits on a restored carriage. Whilst at SX 62757750 a number of large boulders have been split using a single charge, possibly the result of testing. To the south west of the gunpowder factory stands an isolated rectangular building in which finished gunpowder was stored prior to transportation. Within the vicinity of the gunpowder works there are four quarries from which material was derived during the construction of the buildings. Parts of the valley bottom contain earthworks related to tin streamworking. Modern post and wire fences, a shed and piles of sand and other materials associated with a consolidation programme are excluded from the scheduling, although the ground beneath them is included.

Sources / Further Reading

Associated Monuments

Associated Finds: none recorded

Associated Events

• EDV6029 - An Archaeological Survey of the Gunpowder Factory at Powdermills Farm
• EDV6128 - Survey of the Service and Accommodation Buildings associated with Powdermills Gunpowder Factory (Ref: 95.63)
• EDV8644 - Cherrybrook and Longford Newtake, Duchy Farms Survey
• EDV8645 - Powder Mills and Gawler Newtake, Duchy Farms Survey
• EDV8409 - Dartmoor Royal Forest Project
• EDV8423 - Duchy Farms Project

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