But luckily, for archaeological purposes, rock doesn't pass electric current as well as soil does, so measuring levels of resistivity can identify subsurface features like buried foundation walls very well indeed.
The most commonly used type of soil resistivity used on archaeological sites is the Venner method, which involves inserting four probes into the soil and sending electric currents across to one another. Resistance is measured in ohms by a voltmeter.
Sources
Ellwood, Brooks B. 1990 Electrical resistivity surveys in two historical cemeteries in Northeast Texas: A method for delineating unidentified burial shafts. Historical Archaeology 24:91-98.
Heimmer, Don H. 1992 Near-Surface, High Resolution Geophysical Methods for Cultural Resource Management and Archaeological Investigations. Interagency Archeological Services, Rocky Mountain Regional Office, National Park Service, Denver
This glossary entry is part of the Dictionary of Archaeology. Any mistakes are the responsibility of Kris Hirst.

