Wesleyan geologist Jelle Zeilinga de Boer believes natural gases such as ethylene, a once popular anesthetic now used to ripen fruit, entered the chamber in the Delphic Oracle where the priestesses sat through vaults below the temple. Exposure to the gas often produces reduced inhibitions, a sense of floating and euphoria.

Ancient Greeks considered the oracle, near the foot of Mount Parnassus, their spiritual center and the earthly vehicle for the judgments of Earth goddess Gaia and, later, Apollo.

From 1400 B.C. to 381 A.D., colonies were founded, state policies were set and war actions were taken based on what the priestesses had to say.

De Boer's report was published in the August issue of Geology, a journal of the Geological Society of America. It was co-written by archaeologist John Hale of the University of Kentucky and geochemist Jeffrey Chanton of Florida State University.

Visitors to the oracle would ask questions on a variety of topics such as personal finances and military operations, according to ancient writings.

Various women held the position of priestess over the years. The priestess, also known as the Pythia, sat in a chamber and inhaled the "divine breath" of Apollo.

As the priestess responded to visitors' questions, priests who ran the temple scribbled furiously to record the often-cryptic answer, which they would later translate into something more intelligible.

De Boer said ancient Greeks wondered how the priestess came up with the answers.

For centuries, the references to the "divine breath" prompted speculations that vapors played a part in the prophecies.

A team of French archaeologists all but disproved the theory when they did not find a fault during a thorough excavation of the area at the turn of last century.

De Boer told Hale that he believed a fault did exist near the oracle's site, and Hale challenged the geologist to follow up on his suspicions. They recruited Chanton and went to work.

The team's first challenge was to obtain permission from Greek officials to dig and take samples from the site.

"The problem is that this is a sacred site of Greece," de Boer said, explaining that it took about one year before they could begin. "Delphi is the heart of everything."

The three scientists did find two faults and intersecting fractures that created pathways for groundwater and gases to rise, de Boer said.

The presence of methane and ethane, which limit oxygen intake, were found in rock samples taken from the site. They also found ethylene in a nearby spring.

In the early 1900s, hospitals used ethylene frequently as an anesthetic. But the use of the gas, which is highly explosive, became impractical as the amount of electrical equipment in operating rooms increased.

The philosopher Plutarch, who once served as the high priest of the oracle, described reduced inhibitions, a sense of floating and euphoria when he wrote of the priestesses' behavior.

Roger Travis, an assistant professor of classics at the University of Connecticut, said the gas probably had little effect on the prophecies. He said many of the prophecies were interpreted by the more sober-minded priests who ran the temple. He also said priests often received kickbacks to interpret the prophecies to suit the wishes of their sponsors.

"The process of getting a prophecy from Delphi was extremely tightly controlled," Travis said. "They took the drug-induced or otherwise induced ramblings and translated them into usable, or at least ambiguous, hexameter poetry that could then be interpreted in just about anything they wanted to."

De Boer and his colleagues also play down suggestions that the work should radically alter how we regard ancient Greek society. What the research does, they say, is add credibility to the ancient texts, which first suggested the role of vapors in the prophecies.

"The main importance is to scholars; it shows ancient writings as true and valid sources of ancient history," Hale said.

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