The role of traditional geophysical methods in evaluating mine sites in England and Wales by Vernon, R.W., McDonnell, J.G., and Schmidt, A. Department of Archaeological Sciences, University of Bradford, England. Introduction Research at the University of Bradford (Vernon et al. 1999, 2002; Vernon 2005) has shown that interpretable geophysical results can be obtained from complex smelting sites so why not from complex mine sites? A few 16th century mine sites have been geophysically surveyed in the Vosges, France (Ancel and Fluck 1990; Grandemange 1990) but such sites can be relatively uncomplicated when compared to 19th century remains. Disused metal-mine sites contain many elements that can make geophysical data acquisition virtually impossible, for example iron debris, porous rubble and dense vegetation. Surveys may also be limited by shafts and spoil tips with steep slopes. At the shaft top there can be an engine house for pumping and winding machinery, and small workshops. Magnetometer and earth resistance surveys however, might detect spreads of ferrous debris and walling, respectively associated with those structures. Geophysical surveys, using the Geoscan FM 36 fluxgate gradiometer and the Geoscan RM15 earth resistance meter, have been conducted around the shaft top areas of three 19th century lead mines in Britain. This paper outlines the failures and successes of these surveys. Nant Mine, Flintshire, Wales (1998). (Figure 1) A mine abandonment section showed a possible boiler house located near an engine house. The survey was conducted to confirm the boiler house location, as it was considered that deposits of fired material, often found in and around such structures, might produce a response on a fluxgate gradiometer survey. Four 10m square fluxgate gradiometer and earth resistance grids were surveyed at 0.5m x 0.5m resolution. It was only possible to survey about 50% of the planned earth resistance survey due to dense vegetation and the presence of limestone rubble. The results of the fluxgate gradiometer survey were difficult to interpret because of iron spiking and incomplete data. However, a weakly contrasting linear anomaly was identified parallel with, and approximately 4m from, the east wall of the engine house. On the earth resistance survey this area was represented by low data values. Both surveys appear to identify the boiler house position but on a different orientation to that shown on the mine section. After abandonment, the floor of the boiler house would have become infilled with fine material that would generate lower earth resistance values than the surrounding limestone rubble. The earth resistance survey also identified several curved anomalies that may correspond to the location of a circular horse-whim used for winding, but the survey area was constrained at this point making a valid interpretation difficult. 1 Cononley Mine, North Yorkshire, England (1999). (Figure 2) A small pumping engine house occupies the west side of this extensive mine site. The purpose of the survey was to identify the location and dimensions of the boiler house and a small workshop built against the engine house wall in the 20th century. The survey consisted of three 10m square fluxgate gradiometer and earth resistance grids at 0.5m x 0.5m resolution on the north side of the engine house, and east towards the boiler house chimney. The fluxgate gradiometer survey identified the boiler house walls as distinct linear positive anomalies at ranges between -100 to 100nT. On the earth resistance survey an area of low resistance coincided with the interior of the boiler house. Values increased towards the chimney suggesting the presence of collapsed walling. Some positive data were recorded around the possible site of the workshop on the fluxgate gradiometer survey but they were not confined to a specific area. The initial earth resistance survey was less promising. The mobile probes were set at 0.5m spacing and several areas of high earth resistance data corresponded to deposits of mineral dressing residues. When the area was resurveyed with a mobile probe spacing of 1m, two linear high earth resistance anomalies were identified that corresponded to the foundations of the workshop walls. Magpie Mine, Derbyshire, England (2004). (Figure 3) The survey was conducted on this scheduled monument to identify the location of a mid-19th century boiler house for a small winding engine. It had been originally brought to this site from a mine site currently being excavated. The survey was conducted to see if the configuration of the equipment on both mine sites was similar. Unlike the Nant and Cononley mine surveys, this survey area was undulating and was located about 50m to the south of, and some 6m lower than, the shaft top. The fluxgate gradiometer and earth resistance surveys consisted of eight 10m square grids surveyed at 0.5m x 0.5m resolution. Iron debris was common in the survey area, but the fluxgate gradiometer survey identified two short linear anomalies trending roughly northeast from the vicinity of a chimney and adjacent forge. However, below a range of –100 to 100nT they become lost in the overall responses produced by iron spiking. The earth resistance survey identified a pronounced narrow linear anomaly of high earth resistance data that probably represents the partially collapsed western wall of the boiler house. An irregular pseudo-linear cluster of higher values that correspond to a topographical change is believed to represent the west wall. When the results are compared the anomalies that represent the west wall of the boiler house do not match exactly. However, the two techniques respond to different physical parameter. The fluxgate gradiometer does not respond to the non-magnetic limestone walls, but will respond to any magnetic material that may lie within the boiler house or against the walls. The earth resistance survey will respond to the actual walls, and linear anomalies represent the position of the boiler house walls. When the results were compared with structures on the site, it was realised that the chimney and the forge adjacent to the survey were actually part of the boiler house. 2 Conclusions The three examples show that it is possible to collect interpretable results from geophysical surveys over mine sites. Historical research and an understanding about how the mine site functioned compliment them. It is an area of research that extends the use of archaeological prospection into complex industrial areas. References Ancel, B. and Fluck, P. 1990. Sainte-Marie-aux-Mines, Secteur de L’Altenberg, Vallee de Fertrupt: Etude souterrainne del la Porte de Fer, un reseau medieval repris au XVIème Siecle (Sondage 1988). in Pierres et Terre 34, Federation Patrimoine Minier, Ste. Marie-aux-Mines. 78-80. (In French) Grandemange, J. 1990. Le Samson: Ateliers et Habitats d'une Mine D'Argent du XVIeme Siecle. in Pierres et Terre 34, Federation Patrimoine Minier, Ste. Marie-aux-Mines. 116-120. (In French) Vernon, R.W., McDonnell, G. and Schmidt, A. (1999) Medieval iron and lead smelting works: a geophysical comparison. In Pollard, A.M. (ed) Geoarchaeology: exploration, environments, resources. Geological Society, London Special Publication. 165 15-34 Vernon R., McDonnell G. and Schmidt A. 2002. The geophysical evaluation of British lead and copper working sites. Comparisons with iron working. Archaeological Prospection 9. 123-134 Vernon, R.W. 2005. Application of Archaeological Geophysical Techniques to the Investigation of British Smelting Sites. Unpublished PhD Thesis. University of Bradford. 1b 1c 1d Engine House Fluxgate gradiometer data. -20nT (White) to 20nT (Black) Earth resistance data. 340 (White) to 600 (Black) Boiler house? Trace of horse whim circle? Figure 1. The Nant Mine Engine House. 1a. The engine house with the chimney from the boiler house. 1b. The fluxgate gradiometer survey. 1c. The earth resistance survey. 1d. Interpretation. 1a The survey of four 10m grids was conducted between the engine house and the chimney. 3 2a Survey grid 2c E.H. E.H. Chimney 5m a) Fluxgate gradiometer survey and grid 50nT (white) to 50nT (black) 2b Structures survey by M.Roe. 1998. Figure 2. The Cononley Mine Engine House. E.H. E.H. 5  (white) to 56  (black) Mobile probes 0.5 m 15  (white) to 110  (black) Mobile probes 1.0m 2a. The fluxgate gradiometer survey fitted to the 10m survey grid. 2b. The earth resistance survey at different mobile probe spacings. 2c. Interpretation. Boiler house (B) from fluxgate gradiometer survey. Workshop foundations (W) from earth resistance survey. b) Earth resistance surveys. 3a E.H. = Engine House. 20th century winding house. 3b  Original boiler house  19th century winding engine. F F = Forge. 0 metres 20 0 Flue metres 20 Chimney Figure 3. The Magpie Mine Engine House. 3a. The fluxgate gradiometer survey. -80nT (white) to 80nT (black) 3b. The earth resistance survey. 20 ohms (white) to 220 ohms (black) The surveys proved that the walls of the forge and the chimney were originally part of the boiler house. The chimney was later modified with the addition of the flue. 4