Abstract
AbstractAs part of a long‐term research project on prehistoric and medieval iron‐working sites in northwest Wales, a technique has been developed for processing magnetic survey data to improve the presentation and recognition of the high‐amplitude dipolar signals that are characteristic of iron‐smelting furnaces. This technique has now been used successfully on some 37 British iron‐working sites. High‐resolution surveys, on a 10‐cm grid, have been made both by caesium magnetometer and fluxgate gradiometer over four prehistoric furnaces and one medieval furnace giving detailed maps of their magnetic signals. Mathematical models of these maps, using multiple dipoles, has given estimates of the directions of total magnetization of the furnaces. Three of the furnaces were also surveyed at subsequent stages of excavation and after the removal of the furnace, giving the background signal. The background signals can then be subtracted from the survey data to give clean residual maps. These are easier to model, giving more reliable results, and they give useful information on the contribution of the different furnace materials to the overall magnetic signals. The corrections required for the influence of induced magnetism and for viscous remanent magnetism are examined. The results are compared with the British archaeomagnetic curve, and with the archaeomagnetic date estimates from three of the furnaces, to assess the value of the modelling technique in giving usable estimates of the date of last firing of the furnaces. Copyright © 2002 John Wiley & Sons, Ltd.
Published Version
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