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Charcoal fired blast furnace site

in Canaston Wood, near Blackpool Mill, Pembrokeshire.


Introducton

This site has been known to the author since the late 1980s following field investigations carried out after the late Michael Evans suggested that place-name evidence from the Ordnance Survey field drawings of circa 1810 indicated that iron smelting had been carried out on the site in addition to the well known forge operations. Recent clear felling of the site has allowed a further, more detailed, investigation to be carried out in support of the Dyfed Archaeological Trust and Forest Enterprise.


A brief history and description of the site

The first evidence for iron smelting on the site is a document of 1635 granting George Mynne, of Woodcote in Surrey, a lease of the 'decayed mill called Canaston Myll,' with 'free liberty of the river and other waters,' the right to erect buildings 'for melting iron' within one mile of the mill, and 'a proportion of timber for the use of the iron works ... in the woods of West Wood, Toft Wood, Pickhill Wood, Minweare Wood and Penglynes Cliffs.' (1) Prior to that document Canaston Mill was referred to as a 'water mill' and is generally associated with the weir on the Cleddau at Blackpool. (2)

This was at a time when the blast furnace based iron industry was dispersing from its 16th century base in the Weald of Sussex. (3) Furnaces were already well established in the Forest of Dean (a total of 11 by 1633) where Mynne had iron working interests. The criteria for such iron works being water, as a source of power; a sustainable supply of wood for fuel; access to iron ore and flux (initially old bloomery slags but later, as at Blackpool, limestone) and good transport facilities. All of these were met at Blackpool, at the tidal limit of the Cleddau, and when, in 1636, Mynne was granted letters patent for the erection of two forges and a furnace within a 12 mile radius of Whitland Abbey, the Blackpool site would have been well suited for a blast furnace and forge, with a further forge reported near Whitland Abbey itself. Production may have ceased before Mynne's death in 1648 and was possibly concentrated in the few years after establishment of the furnace and forges when there was extensive removal of wood from the Whitland area. Although his widow did subsequently (1654) value his iron working assets at 10,000 per annum. (4) It is not known if the furnace was operated again but it was certainly not in use in 1709 when consideration was given changing the forge at Blackpool into a furnace. (5) At that time the forge was in the hands of the Foley partnership who were processing pig iron brought from the Forest of Dean.

Further documentary research is required in an attempt to determine the period over which the furnace at Blackpool was active. Field evidence suggests that the iron ore used was in part carbonate ore from the Coal Measures. That could have been sourced close at hand, possibly at Landshipping, or brought in from the south Pembrokeshire coast between Saundersfoot and Amroth. A search of the Exchequer Port Books (Public Record Office E190) has so far failed to find evidence for the import of ore or the export of pig / bar iron. Although local shipments of ore would probably not be recorded, ore, bar and pig iron shipped from and to ports outside the Milford area should be recorded. Unfotunately, the surviving coastal port books do not provide a complete series for the period.

The green glassy slag found on the site is typical of a furnace using limestone as a flux. That was available locally in the Mounton - Newton area. Gauging total pig iron production from the amount of slag is a possibility. However, a survey of the site would be necessary to determine the extent and depth of slag scatter south and west of the main heaps.


The field evidence

Attached are two maps, both based on the 2nd edn. 25" OS, annotated with information gained from field and archival investigations. Comment is made below on the features shown on those maps.
[GENERAL
Map One - general layout of furnace and later forge site.
  1. Furnace leat - there is now only slight evidence on the ground for the leat between the field boundary south of the furnace site and its source, but the abstraction point appears to have been at or near the point where the track to Eagle Lodge crosses the stream. There may have been a dam on the stream at that point.

  2. Furnace site - see Map Two for detail.

  3. Tailrace leat - rather than return the tailrace from the bellows wheel directly to the stream it was expected that the water would be utilised at any associated finery / forge site and that appears to confirmed by the field evidence. This leat can be followed as a clear feature through the standing mature conifers and as a slight feature across clear felled ground north of the track. South of the track, as far as the woodland boundary, it is a clearly identifiable feature. Beyond the woodland boundary it is lost in cultivated ground, currently standing corn, but appears to head for the farm south-east of Blackpool Mill. Further field work is required to determine whether the leat was intended for a finery site there or at the site of the 18th century forge.

  4. 18th century forge site - clearly marked on contemporary maps, utilizing the surviving leat from the Cleddau. (6)

[DETAIL
Map Two - detail of furnace site.
  1. Leat - this is a clear ground feature north of the southern field boundary, terminating in an area of disturbed ground.

  2. Dump of iron-rich material - a small heap of low grade iron ores, including a few nodules of Coal Measure ironstone. Anthracite is also found in the heap, probably brought in with the ironstone. On the northern end of the heap are stones possibly originating from a masonry structure on the site.

  3. Gully - probably the site of the bellows water-wheel.

  4. Burnt stone - a heap of material from the furnace structure, including scraps of furnace lining. Iron slag containing entrapped charcoal has been found in this area. To the north-east of this area the ground is level before falling away to the north and east. There is currently no evidence of a casting floor.

  5. Slag dump - a moderate sized dump of grey-green glassy slag parallel with the stream.

  6. Slag scatter - between the furnace site and the slag dump are numerous pieces of iron rich slag but north of the northern field boundary is an extensive area of grey-green glassy slag, diminishing in depth to the north-west.

  7. Tail race leat - from the northern end of the gully the leat runs east as a clear earthwork feature following the contour. See Map One.

Conclusions

Further documentary research is required to determine the full period over which the blast furnace was active. However, although this is not the earliest blast furnace site in west Wales, Ponthenri predates it by over twenty years,(7) it does present a relatively undisturbed set of features illustrating the furnace at the height of the migration westwards.

Notes

The furnace site is now designated as a Scheduled Ancient Monument - contact Cambria Archaeology www.acadat.com for further details.

References

  1. National Library of Wales (NLW), Slebech 441.
  2. NLW, Slebech 359; 342; 315; 317; 871; 314; and 5608 (dated 1555 to 1633)
  3. Harris, J R. The British Iron Industry 1700 - 1850, 1988.
  4. See Evans, M C S. The Pioneers of the Carmarthenshire Iron Industry, Carmarthenshire Historian, 1967.
  5. NLW, Slebech 5609.
  6. Pembrokeshire Record Office D/RTP/SLE/80
  7. Riden, Philip. A Gazetteer of Charcoal-fired Blast Furnaces in Great Britain, 2nd. edn., 1993, p. 29-30. Riden failed to update the information on Blackpool in the gazetteer, p. 13, despite being informed as to the location and extent of surviving features in 1989. However, there is as yet no evidence that the furnace was operated beyond 1660.

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Peter Claughton / SHiPSS
P.F.Claughton@exeter.ac.uk
Last modified 17 May 2003