Recent work on Archaeomagnetism has been concentrated in two main fields, first, detection of sites with magnetic anomalies using instruments like the proton magnetometer, and secondly the construction of a dated graph of the earth’s magnetic field with the ultimate aim of providing an absolute chronology for fixed fired sites, mainly kilns and hearths. Important work in a third field, using the changing angle of inclination of pottery to provide a relative chronology for a series of vessels entirely independent of archaeological means, has fallen out of fashion despite the efforts of the pioneers of Archaeomagnetism and more recently the researches of Mr R. M. Cook on Corinthian pottery, at Cambridge and Dr M. J. Aitken on Chinese porcelain at Oxford. It is with this third method of approach that the present article is concerned and its application to a series of British beakers.

When a clay vessel is fired its temperature is usually raised well above the Curie-point, about 500-600° C.; at this point the magnetic elements in the clay will begin to orientate themselves with the prevailing Earth’s magnetic field rather as though they were myriads of minute compass needles. Upon cooling, this uniform orientation will remain ‘fossilized’ and under normal conditions a permanent record of the Earth’s magnetic field at the time and place of firing. However, the finished vessel will then be used and removed from its firing position, thus for ever removing any chance of comparing its angle of declination (or compass bearing) with that now existing, since their positions relative to geographic north cannot be determined. If it can be shown that the vessel was fired in a vertical position the angle of inclination (dip) is still recoverable for comparison with the modern angle and with that preserved in other similar vessels. Since the angle of inclination alters a little every year (non-linearly)—it should be theoretically possible to arrange them in relative order of firing or date, thus providing an invaluable relative chronology.