A geophysical instrument used in electromagnetic surveying for the detection of metal, but also for the location of archaeological features such as shallow pits, which have a different conductivity from the surrounding soil. The instrument has a transmitter coil which is fed with a continuous sinusoidal current, and a receiver coil; they are mounted at right angles to each other at opposite ends of a horizontal bar about a meter long. The instrument is designed to pick up differences in conductivity between features and the surrounding soil, i.e. the reverse of a resistivity meter. Resistivity surveying is considered more sensitive and versatile.