Science: Search for Sybaris

Did the ancient Greeks have outside toilets? Up-to-date archaeologists interested in esoteric problems heard last week about a handy way of finding answers to such questions—for a latrine's humus-rich contents have magnetic properties that vary from the earth around them.

The clever instrument that can tell the difference was the hit of an erudite conference that met at Venice to discuss new methods of archaeology. Called a proton magnetometer, the gadget is based on a principle of nuclear physics discovered only a few years ago. The nuclei of hydrogen atoms (protons) are, in effect, tiny magnets, and they line up like compass needles parallel to the earth's magnetic field. When nudged out of alignment, they oscillate for a few seconds, the speed of their oscillation changing with the local strength of the earth's magnetism. Buried objects that affect the field show up plainly.

Bottle & Coil. The magnetometer displayed at Venice was developed by Oxford's Research Laboratory for Archaeology, following U.S.-designed electronic circuits. The working arm of the instrument is a small (about 5 oz.) bottle of plain water, which contains hydrogen and, therefore, protons. Surrounding the bottle is an electrical coil connected to a control box. The magnetometer is usually operated by two people, one of whom moves the bottle from point to point, while the other sits at the control box. To make an observation, the controller presses a button, shooting an electric current from a storage battery through the coil, deflecting the protons in the bottle. When the current stops, the protons oscillate, creating a feeble alternating current in the coil. This current flows back to the control box, where its frequency is measured, giving the strength of the magnetism surrounding the bottle.

Oxford Archaeologist M. J. Aitken explained to the conference why almost any disturbance of the soil shows up on the magnetometer. Topsoil is generally more magnetic than soil below it, so when a ditch or cellar gradually fills with material washed from the surface, it distorts the earth's magnetic field enough to be detected by the magnetometer despite several yards of debris.

No Good for Treasure. Ancient rubbish, garbage and human excreta are easily detectable. So are buried walls, whose stones usually have different magnetic properties from the material that covers them. Empty spaces, such as buried tombs, stick out like magnetic sore thumbs. Most conspicuous of all are objects of iron or steel, but the magnetometer does not detect gold and silver, and it will be of little use to treasure seekers.

The instrument is now being used to find Sybaris, the rich Greek colony in southern Italy that gave its name to the word sybaritic. After losing a war with the nearby city of Croton. Sybaris was leveled to the ground, and the Crotonians made the river Crathis flow over the ruins and cover the site with silt. Archaeologists hope that some of the city's interesting features were sealed in protective mud, but they have never known just where to look for them.