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Summary

Leat constructed in the 19th century and carried water to the site of Powder Mills from the East Dart river. It measures circa 1 metre deep, circa 1.3 metres wide at the base and circa 3.2 metres wide at the top; a stone revetted earthen bank 3 metres wide and 1 metre high lies along its south side.

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: SX67NW231
• National Record of the Historic Environment: 887638
• Old DCC SMR Ref: SX67NW/143
• Old DCC SMR Ref: SX67NW/246
• Old SAM Ref: 28718

Monument Type(s) and Dates

• LEAT (Constructed, XVIII to XIX - 1800 AD (Between) to 1900 AD (Between))

Full description

Ordnance Survey, 1880-1899, First Edition Ordnance 25 inch map (Cartographic). SDV336179.

Leat shown on 19th century map. The direction of flow indicates that this leat does not divide at SX62987761. The leat running from Cherry Brook to that grid reference is a separate feature.

Royal Air Force, 1951, 540/483, 3047-9, 4047-8 (Aerial Photograph). SDV248164.

Greeves, T. A. P., 1983, Middle Merripit Survey Drawing (Plan - measured). SDV321106.

Powder Mills Leat. Runs from SX63908132 to SX63007762.

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

Clearly visible on 1951 Royal Air Force aerial photographs. The leat divides at SX62987761, one part going down through the wheel house, the other part extending to Cherry Brook.

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

(19/07/1989 P. Pattison) The largest of 3 leats serving the 19th century gunpowder works at Powder Mills (SX 67 NW 99). It was taken off the East Dart River at SX 63898131 and runs a sinuous course of c. 4.9km entering the Powder Mills enclosure at SX 62997781, a total fall of only c. 9m.
From the source it runs a fairly straight course for 1.3km S alongside the East Dart. From SX 63818000 it begins to curve to the SW, crossing the Broad Down Brook (Braddon Lake) at SX 63347962 where it is waterlogged and temporarily lost in the marshy overspill of the stream. It is similarly obscured at its crossing of the Chittaford Brook at SX 63477942, from where it runs around the NE flank of Chittaford Down and into the enclosures of Archerton (Just SE of a footbridge at SX 63797944 it is joined by another leat SX 67 NW 209 from Rowtor Marsh). This section of the leat is now dry, represented by a u-shaped channel averaging 1.5m wide at base and 0.8m deep with a substantial upcast bank on the downslope 4m wide and 1m high. The bank is sometimes stone revetted.
(19/07/1990 I. S. Sainsbury) SX 63887929 to SX 63827873. The Powder Mills Leat enters the Archerton Estate from open moorland under the NE Newtake Wall at a height of 390m OD. It follows a sinuous route for about 550m through the grounds of Archerton House. It apparently held water until recently and its channel has been cleaned out and in places recut. It measures 1m deep, 1.3m wide at the base and 3.2m wide at the top; a stone revetted earthen bank 3m wide and 1m high lies along its S side.
A disused stone-built sluice channel with the remains of 2 sluice gates lies at the S end. The channel is 7.7m long, 1.5m wide and 1m deep; the gates are set 4.6m apart in the channel. It was probably built to control the water flow after the gunpowder works (SX 67 NW 99) closed in the late 19th century. The leat was damaged by fallen trees during the 1990 gales.

Pye, A. R. + Robinson, R., 1990, An Archaeological Survey of the Gunpowder Factory at Powdermills Farm, Postbridge, Devon, 38, Figure 3 (Report - Survey). SDV254157.

SX 62887800 Leat running south from Cherry Brook to a reservoir in the Powder Mills gunpowder factory complex.

Pye, A. R. + Robinson, R., 1990, An Archaeological Survey of the Gunpowder Factory at Powdermills Farm, Postbridge, Devon, 38, Figure 3 (Report - Survey). SDV254157.

Leat from the East Dart river above Postbridge built circa 1845. Leads into a reservoir at the north end of the Powder Mills gunpowder factory complex.

Gerrard, S., 1990-2002, Monument Protection Programme. Archaeological Item Dataset., MPP 149198 (Report - Survey). SDV277946.

(1998) Leat serving the gunpowder factory at Powder Mills.

Pye, A., 1996, The Gunpowder Factory at Powdermills, 221 (Article in Serial). SDV254160.

Dartmoor Trust and Dartmoor National Park Authority, 2010, Dartmoor Trust Leats Project 2009-2010 (Report - Survey). SDV347530.

Powdermills Leat surveyed and recorded running between SX634794 - SX628773. (Postbridge). Dry leat. Other details: T:\Dartmoor Leats Survey / Q:\MAPDATA\HISTORIC\LeatsProject.

Ordnance Survey, 2011, MasterMap (Cartographic). SDV346129.

Leat shown on modern mapping.

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

'Leat (disused)' shown on modern mapping.

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 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. A partially enclosed stone hut circle settlement lies adjacent to the leat carrying water from the East Dart and survives as a series of four enclosures associated with at least 13 stone hut circles. The enclosure walls are of rubble bank construction standing up to 0.4 metres high. The stone hut circles survive as circular or oval walls surrounding an internal area varying between 4 and 50 square metres. A round cairn lies immediately west of the settlement and survives as an 8.7 metres diameter mound standing up to 0.9 metres high. Large edge set stones on the north western edge of the mound may suggest the presence of a kerb which survives elsewhere as a buried feature. A pit in the centre of the mound suggests partial early excavation or robbing. 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
• EDV8645 - Powder Mills and Gawler Newtake, Duchy Farms Survey
• EDV8646 - Archerton, Duchy Farms Survey
• EDV8648 - Middle Merripit Farm, Duchy Farms Survey
• EDV8650 - Great Stannon Newtake, Duchy Farms Survey
• EDV8409 - Dartmoor Royal Forest Project
• EDV8423 - Duchy Farms Project

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