REASONS FOR DESIGNATION
Approximately 10,000 lead industry sites are estimated to survive in England, spanning nearly three millennia of mining history from the later Bronze Age (c.1000 BC) until the present day, though before the Roman period it is likely to have been on a small scale. Two hundred and fifty one lead industry sites, representing approximately 2.5% of the estimated national archaeological resource for the industry, have been identified as being of national importance. This selection of nationally important monuments, compiled and assessed through a comprehensive survey of the lead industry, is designed to represent the industry's chronological depth, technological breadth and regional diversity. Ore hearth smelt mills were introduced in the 16th century and continued to develop until the late 19th century. They were the normal type of lead smelter until the 18th century, when they were partially replaced by the reverberatory smelt mill. The ore hearth itself consisted of a low open hearth, in which lead ore was mixed with fuel (initially dried wood, later a mixture of peat and coal). An air blast was supplied by bellows, normally operated by a waterwheel; more sophisticated arrangements were used at some 19th century sites. The slags from the ore hearth still contained some lead. This was extracted by resmelting the slags at a higher temperature using charcoal or (later) coke fuel, normally in a separate slag hearth. This was typically within the ore hearth smelt mill, though separate slag mills are known. Early sites were typically small and simple buildings with one or two hearths, whereas late 18th and 19th century smelt mills were often large complexes containing several ore and slag hearths, roasting furnaces for preparing the ore, refining furnaces for extracting silver from the lead by a process known as cupellation, and reducing furnaces for recovering lead from the residue or litharge produced by cupellation, together with sometimes complex systems of flues, condensers and chimneys for recovering lead from the fumes given off by the various hearths and furnaces. The ore hearth smelt mill site will also contain fuel stores and other ancillary buildings. Ore hearth smelt mills have existed in and near all the lead mining fields of England, though late 18th and 19th century examples were virtually confined to the Pennines from Yorkshire northwards (and surviving evidence is strongly concentrated in North Yorkshire). It is believed that several hundred examples existed nationally. The sample identified as meriting protection includes: all sites with surviving evidence of hearths; sites with intact slag tips of importance for understanding the development of smelting technology; all 16th- 17th century sites with appreciable standing structural remains; 16th-17th century sites with well preserved earthwork remains; and a more selective sample of 18th and 19th century sites to include the best surviving evidence for smelt mill structures, and flue/condenser/chimney systems.
The Froggatt Wood smelt mill is one of the very few 16th-17th century smelt mills in England to retain any standing structures. The water channel and wood-drying kiln are unique within the lead industry, and the survival of an undisturbed complex of this date, with a wide range of features, is very rare. It has enhanced amenity value due to its location on National Trust land within a National Park.
The monument lies in woodland on the eastern side of the Derwent valley. It includes a lead smelt mill and associated structures, contained within two contemporary enclosures. The water supply to the smelt mill is provided by a pond and dam on the east side of the site, from which a channel of shaped stone blocks leads to the mill. The smelt mill itself survives as a ruined building, orientated east- west, within which a wheelpit is visible at the east end. The interior of the building is full of rubble. To the west, tips of slag extend down the hillslope, and a broken stone mould (for pouring pigs of lead) lies nearby. An unusually complex stone wood-drying kiln lies to the south east of the smelt mill, which was used to dry wood for use in the ore hearth of the mill. The structures are contained within two conjoined enclosures, defined by ruined drystone walls; a third enclosure to the north contains no visible internal features and is not included in from the scheduling. The character of the remains indicates a 16th-17th century date.
Article Reference - Author: Crossley, D, and Kiernan, D - Title: The Lead-Smelting Mills of Derbyshire - Date: 1992 - Journal Title: Derbyshire Archaeological Journal - Volume: CXII - Page References: 15-16 - Type: DESC TEXT
Article Reference - Author: Crossley, D, and Kiernan, D - Title: The Lead-Smelting Mills of Derbyshire - Date: 1992 - Journal Title: Derbyshire Archaeological Journal - Volume: Vol CXII - Page References: 15-16 - Type: DESC TEXT