Magnetic measurements on orientated samples from the baked clay walls and floors of pottery kilns, etc., enable the ancient direction of the Earth's magnetic field to be determined. This direction is recorded at the last firing by the phenomenon of thermoremanent magnetism. The time variation of this direction is found from measurements on structures of archaeologically known date and this information can then be used in reverse for dating. The above technique requires the existence of a reliable archaeological chronology. On the other hand, thermoluminescence measurements on fragments of pottery yield ages that are independent of existing chronologies. Thermoluminescent dating will therefore be valuable in checking the validity of the corrections to radiocarbon ages discussed in the preceding papers.