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Trances may have been caused by underground gases, but scientists don't agree which ones.

B. Mason

The Prophet of Gases

The Oracle at Delphi in central Greece was a major religious center for more than 1000 years. Citizens and rulers alike made pilgrimages there to get advice on everything from mistresses to military conquests. The officiant at the oracle was always a woman, referred to as the Pythia, who perched on a tripod above a chasm in the bowels of the Temple of Apollo and inhaled fumes from the earth that would induce a prophetic, often crazed, trance during which she would relay the wisdom of the gods.

The story was dismissed as a myth during the first half of the 20th century, when excavation of the temple and studies of the area by archaeologists turned up no sign of a chasm or a large fissure of any sort. But in the late 1990s, geologist Jelle de Boer of Wesleyan University in Middletown, Connecticut, suggested that two faults crossing directly under the temple could have been the source of the chasm and the vapors. De Boer's group found traces of ethylene, a central-nervous stimulant that can produce euphoria, in a local spring and concluded it was the likely source of the oracle's frenzied trances.

Giuseppe Etiope of the National Institute of Geophysics and Volcanology in Rome, Italy, and his colleagues are skeptical. They assert that the marine limestones underlying the temple couldn't have contained ethylene in high enough concentrations to account for the Pythias' trances or the sweet smells reported by Plutarch, a high priest of the temple in the first century. The team brought a portable laser sensor to Delphi and discovered no traces of ethylene. Other labwork turned up significant amounts of carbon dioxide and methane seeping from the ground in the area. Etiope's group suggests that if gas was having a neurotoxic effect on the prophetic women at Delphi, it was most likely carbon dioxide and methane causing oxygen deprivation in the enclosed temple chamber that was the source of the Pythias' inspiration. They speculate that the sweet smells Plutarch reported could have been from benzene fumes coming from local springs, although they did not detect the gas. The research appears in the current issue of Geology.

De Boer says ethylene is the strongest contender, and that benzene is too toxic to be a good candidate: "We all know how dangerous inhalation of this gas is, and most Pythia would probably have died within a year after having inhaled this gas." However, geologist Luigi Piccardi of the National Research Council Institute for Geosciences and Georesources, in Florence, who has also studied Delphi, agrees with Etiope that ethylene was probably not the culprit but says more gas sampling needs to be done before the case can be closed on any of the suspects.

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