The Delphic Oracle: A Multidisciplinary
Defense of the Gaseous Vent Theory
Henry A. Spiller,
*John R. Hale,
and Jelle Z. De Boer
Kentucky Regional Poison Center, Louisville, Kentucky
Department of Anthropology, University of Louisville, Louisville, Kentucky
Department of Earth and Environmental Sciences, Wesleyan University,
Ancient historical references consistently describe an intoxicating gas, produced by
a cavern in the ground, as the source of the power at the oracle of Delphi. These
ancient writings are supported by a series of associated geological ﬁndings.
Chemical analysis of the spring waters and travertine deposits at the site show these
gases to be the light hydrocarbon gases methane, ethane, and ethylene. The effects of
inhaling ethylene, a major anesthetic gas in the mid-20th century, are similar to
those described in the ancient writings. We believe the probable cause of the
trancelike state of the Priestess (the Pythia) at the oracle of Delphi during her
mantic sessions was produced by inhaling ethylene gas or a mixture of ethylene and
ethane from a naturally occurring vent of geological origin.
Key Words: Delphi; Ethylene; Altered mental status; Oracle
Oracles were usedin the ancient world to gain insight to
the future. Oracles were believed to have unique access to
the gods of a particular religion and through this access
were often able to see into the future. The most revered
oracle in ancient Greece was located at the town of Delphi
in the temple of Apollo, the god of prophecy. The prestige
of this oracle made Delphi the most important, inﬂuential,
and wealthy sacred place in the entire Greek world. For at
least a thousand years, the pronouncements of the Delphic
oracle offered divine guidance on issues ranging from the
founding of colonies to declarations of war, as well as
advice on personal issues.Rulers of Greece, Persia, and the
Roman Empire made the arduous journey to this
mountainous site. The ancient Greeks believed that the
Copyright q2002 by Marcel Dekker, Inc. www.dekker.com
*Corresponding author. Mr. Henry Spiller, Kentucky Regional Poison Center, P.O. Box 35070, Louisville, KY 40232-5070. Fax:
502/629-7277; E-mail: email@example.com
Clinical Toxicology, 40(2), 189–196 (2002)
prophetic power of the Delphic oracle derived from the
unique location of the temple at Delphi. According to
classical authors such as Plutarch and Cicero, the priestess
who spoke the prophecies (the Pythia) sat on a tripod that
spanned a ﬁssure or cleft in the rock deep within the temple
of Apollo. A pneuma (breath, wind, vapor) rose from this
chasm into the recessed inner sanctum, or “adyton,” where
it intoxicated the Pythia and inspired her prophecies.
During the last century, however, these ancient testimonies
have been challenged and dismissed as unreliable, even as
fraud. We use a combinationof the ancient texts, geological
evidence, and modern understanding of the properties of
anesthetic gases to defend the argument that the prophesies
of the Pythias in fact occurred after an intoxication from
gases of geological origin.
When French archaeologists began to dig at Delphi in
the 1890s, they expected to ﬁndan elaborate marble temple,
ﬁne statuary, and an inner sanctum built on bedrock with a
large cleft or ﬁssure in the ﬂoor. To their disappointment,
the excavations revealed only the foundations of the
Temple of Apollo, along with parts of fallen columns. The
center of thetemple had no ﬂoor, but instead of revealing an
expanse of ﬁssured bedrock or the mouth of a cave it
seemed to be built over a thick bed of natural clay.
A visiting English scholar was the ﬁrst to express
skepticism about the ancient traditions (1). Half a century
later, an inﬂuential book was published by one of the
leaders of the French team (2). Amandry maintained that
there was no archaeological evidence in the temple itself
to support the belief in a ﬁssure or a gaseous emission
(2). Moreover, he claimed that such an emission would
be geologically impossible in the limestones of Mount
Parnassus and stated that such vapors are only produced
in volcanic areas.
The great authority of Amandry persuaded almost all
historians, classicists, and archaeologists, except the
Greeks themselves, that the ancient tradition recorded by
Plutarch, Diodorus, and other writers was either a myth, a
confusion, or a deliberate fraud. Most modern books on
Delphi state categorically that there was not and could
not ever have been an intoxicating gaseous emission
inside the Temple of Apollo (3,4).
The historical defense of the gaseous vent theory is
based on evidence that includes ancient Greek and Latin
texts as well as the archaeological remains of the temple
and sanctuary. The literary texts include the testimony of
ancient historians such as Pliny and Diodorus, philoso-
phers such as Plato, poets such as Aeschylus and Cicero,
geographers such as Strabo, the travel writer Pausanias,
and even a priest of Apollo who served at Delphi—the
famous essayist and biographer Plutarch. These writers
consistently link the power of the oracle to natural features
inside the temple, such as a ﬁssure, a gaseous emission, and
a spring. The geographer Strabo (64 B.C.– 25 A.D.) wrote:
They say that the seat of the oracle is a cave that is
hollowed out deep down in the earth, with a rather
narrow mouth, from which arises pneuma that
inspires a divine frenzy; and that over the mouth is
placed a high tripod, mounting which the Pythian
priestess receives the pneuma and then utters
oracles in both verse and prose.
The historian Diodorus of Sicily (ﬁrst century B.C.)
noted an additional element in his description of the
They say that the water of the Cassotis spring
plunges underground and emerges in the adyton of
the temple, where it makes the women prophetic.
While the Temple of Apollo was run by men, the
person who spoke the oracles was always a woman. She
was given the title “Pythia.” The Pythia served as a
medium for Apollo, who was believed to take over her
body and voice during her prophetic trances. The priest
Plutarch described the supposed relationship between the
god, the Pythia, and the natural forces by picturing the
god Apollo as a musician, the Pythia as his musical
instrument, and the pneuma, or vapor, as the plectrum or
tool with which he drew sounds from the instrument. The
Pythia was always a woman of the settlement of Delphi,
but she could be old or young, rich or poor, well educated
or illiterate. While she was serving as oracle, or
mouthpiece of the god, the Pythia lived in the sanctuary,
abstained from sexual intercourse, and fasted on or
before the days scheduled for oracular sessions. During
normal trances she heard the questions of visitors and
gave coherent, if cryptic, replies in verse or ordinary
speech. Occasionally she was seized with a violent
delirium rather than a benign trance.
THE SETTING OF THE ORACLE
The oracles at Delphi were delivered when the Pythia
was placed on a tripod (somewhat like a modern
Spiller, Hale, and De Boer190
barstool) in an enclosed chamber within the temple
called the adyton, a Greek term meaning literally “do not
enter.” The Pythia alone remained in the adyton. Those
consulting the oracle remained in a separate antechamber
nearby. The one surviving depiction of the adyton seems
to show that it had a low ceiling held up by a column or
columns (Fig. 1). This part of the temple was recessed
below the main ﬂoor level of the temple entrance.
Visitors descended a long narrow ramp or staircase to
reach the lower level of the waiting room and the
Only nine times each year did the woman mount the
tripod, enter the trance state, and speak for the god. These
sessions were held on “Apollo’s Day,” the seventh day
after each new moon in spring, summer, and fall. The
oracle did not operate during the three months of winter.
During days of oracle activity, the Pythia would initially
be brought by priests of the temple from a secluded and
protected residence and led through a series of
puriﬁcation and religious rituals in preparation for her
performance. Eventually she was led down into the inner
sanctum of the temple (the adyton ).
The geological defense of the gaseous vent theory is
supported by a series of associated facts: (1) the location
of the temple directly above the intersection of two major
faults, (2) the location of springs emerging from the
ground inside and around the temple, (3) the limestone
formations of the area containing petrochemicals, (4) the
unique design of the temple, (5) the fact that the oracle
did not function in the cold winter months, and (6) the
documentation of the presence of hydrocarbon gases
from the spring waters and travertine deposits.
The temple at Delphi is on a site intersected by major
tectonic faults that are part of the Korinth rift zone, a
region of crustal spreading (Fig. 2) (5). It sits on the
mainland of Greece on the southern slopes of the
Parnassos mountain range. Evidence for the recent
geologic activity of one of these faults includes
earthquakes and landslides. Evidence for intermittent
seismic activity is important as it helps to explain: (1) the
venting of the gases over an extended period of time, (2)
the periodic changes in the intensity of the gaseous
emissions, and (3) the eventual cause of their cessation.
Neeft believes that an earthquake destroyed the main part
of the Delphi settlement around 730 B.C. Delphi’s
highest period of prestige and wealth followed this event
and lasted to the end of the ﬁfth century B.C. Another
earthquake severely damaged the temple in 375 B.C. and
again in 23 A.D. Quakes in the area have been reported in
1580, 1769, and 1870. Early references to landslides may
have been indicative of seismic activity in the region.
Rockfalls thwarted attempts to ransack the temple
complex by the Persians in 480 B.C., the Phocians in
354– 352 B.C., and the Gauls in 279 – 278 B.C. Pechoux
Time and again earthquakes had rumbled here,
frightening away the plundering Persians and a
Figure 1. Only surviving depiction of the Pythia from the
time when the oracle was active.
Figure 2. Intersection of the Kerna Fault and the Delphi
Fault. The temple site is located directly above this intersection.
The Delphic Oracle 191
century later the plundering Phocians and a century
later the plundering Gauls; it was the God
protecting his shrine.
The oracle site is underlain by a limestone formation
of late Cretaceous age, which contains layers rich in
bitumen (oil). These limestone deposits formed some
100 million years ago in a shallow tropical sea. The
tectonic collision between the Eurasian and African
plates lifted these rocks above sea level to form the
mountain range of the Parnassos. Friction along fault
planes during slips heated and vaporized the lighter
constituents in the bituminous layers forming hydro-
carbon gases. The most likely path for the gases to follow
upwards would be to rise through the fault lines dissolved
in percolating ground water and to emerge eventually as
springs. There were a number of such springs recorded at
the Delphi site, including the Cassiotis that emerged in
It is interesting to note that the mantic sessions of the
Delphi oracle were never held during the winter months
when the god Apollo was believed to have gone north to
the land of the Hyperboreans. This suggests that the gas
emissions at Delphi may have diminished during the
colder periods when much of the water had accumulated
on Mount Parnassos as snow and ice, and ground water
temperatures were relatively low. As the ground water
temperature rose in the spring, more of the gas it had
incorporated was released.
Another key feature to support the argument for a
geological vent is the unique design of the temple.
Despite being one of the richest sites in ancient Greece,
the temple had an earthen ﬂoor in its center with stone
walls surrounding it. This unique construction, as
opposed to the standard stone ﬂoor of the other major
temples, suggests the design followed a physical need.
The site certainly did not lack funds or engineers, as
evidenced by the other major buildings at Delphi such as
the gymnasium, theater, and Temple of Athena.
A ﬁnal note of importance is the relationship of
seismic activity and continued gas emissions. Because of
changes in the solubility of calcium in enriched ground
water the spaces in the fault zones would be slowly and
inexorably ﬁlled with calcite. Such a process would
inevitably clog or close the exit pathways for the trapped
gases. To reopen such pathways brecciation is needed.
Such a process commonly results from motion along a
fault. Periodic seismic activity, as has been recorded in
the area, is necessary to produce a ten-century-long
venting of gas deposits. Additionally, seismic activity is
also probably responsible for the ﬁnal silencing of the gas
vents and of the oracle. Signiﬁcant earthquakes shift the
ﬂow of ground water with its dissolved gases, frequently
forcing it to emerge elsewhere along the fault.
A collapsed section of the ruined temple ﬂoor has
been tentatively identiﬁed as the possible site of the
adyton (26). It should be noted that three springs have
been identiﬁed at the site whose location of emergence
and ﬂow all follow a pattern of northwest to southeast in
a path that follows the geologic direction of the fault line
and that crosses directly under the temple itself (Fig. 3).
Chemical analysis by gas chromatography was
recently performed on water samples from the springs
in and around the temple site and from travertine deposits
in the adyton using a headspace equilibrium technique
(5). The results of these samples have identiﬁed the
trapped gases as primarily methane, ethane, and
ethylene. Results showed the presence of methane and
ethane in the travertine deposits with no ethylene
detected. Evaluation of the spring water, however,
showed a greater concentration of ethylene than ethane,
with 0.3 and 0.2 nM/L, respectively. Ethylene is a
signiﬁcantly less stable molecule than ethane and
methane, and may not have remained intact in the
travertine deposits in the proportions that originally
Figure 3. Location of fault line under temple and of the
springs’ emergence from ground.
Spiller, Hale, and De Boer192
The concentration of gases that were produced by the
ground vent at the time the oracle was functioning is
unknown. In all likelihood, the strength of the vent varied
over the centuries due to geological conditions, and in
fact Plutarch remarks on the waxing and waning of the
oracle over time. The oracle was reported to have ceased
to function sometime prior to the fourth century A.D. It is
unclear that if 1800 years after the reported cessation of
the vent, the gases present today reﬂect the same
proportion as existed in ancient times.
INTOXICATING PROPERTIES OF
The third portion of the defense of the gaseous vent
theory is that the volatile fumes produced an altered
mental state that is similar to that produced by inhalation
of anesthetic gases. The effects described in the Pythia
are the same as the ﬁrst stage of anesthesia, alternately
referred to as the excitation or amnesia phase (Table 1).
Of the three proposed gases, all have the potential to
produce an altered mental state, with ethylene .
ethane .methane (6). In present day volatile inhalant
abuse, hydrocarbon gases remain one of the primary
sought-after substances for their intoxicating properties
(7– 10). In one report on volatile inhalant abuse, three of
the top four volatile substances chosen for abuse were
aliphatic hydrocarbons (7). Of the three gases available at
Delphi, ethylene is the most likely candidate to have
produced the intoxicating vapor. Ethane, however, would
be nearly equipotent and a mixture of the two would also
produce signiﬁcant altered mental status (6).
Ethylene is a simple aliphatic hydrocarbon gas
), with a sweet odor detectable at 700 ppm (11).
It was one of the major inhalational anesthetic gases used
in general anesthesia from the 1930s through the 1970s
(12– 16). Induction of full anesthesia with ethylene
occurs rapidly (12,13,16 – 18). In less than 2 minutes after
inhalation, levels of ethylene in the brain are capable of
producing full anesthesia (16,17,19,21). Bourne found
ethylene to be approximately 2.8 times as potent as
nitrous oxide or ether (16). Some of the advantages of
ethylene were its rapid onset and clearance, and the lack
of respiratory and cardiovascular depressing effects. This
is primarily due to low solubility and distribution outside
of the vascular compartment. The major disadvantages
were the rare ﬁres or explosions in the operating room
(22,23). It was replaced with safer, less explosive gases
by the 1970s.
There are relatively few eyewitness descriptions of
the Pythia in her intoxicated state. This is most likely
because relatively few insiders knew the inner workings
of the temple. The descriptions that do exist offer two
distinct pictures of the Pythia in her intoxicated state. The
ﬁrst is the normal and “working state” of a calm relaxed
woman able to respond to questions with visions that in
many cases were random and not apparently associated
Comparison of Historical Descriptions of Usual Response/Presentation of the Pythia with That of Mild Anesthesia via Inhalational
Description of Pythia at Delphi
from a “Normal” Mantic Session
Description of Mild Anesthesia with
Ethylene or Nitrous Oxide
Rapid onset of trance state Full effects in 30 seconds to 2 minutes (Borne)
Calm response, willingly entered the adyton.
Remained there for hours
Pleasant state of being, no sense of anxiety or asphyxiation. Happy to
stay under inﬂuence of gas for long periods of time (Lockhardt)
Remain conscious Remain conscious (Lockhardt)
Able to maintain seated position Able to maintain seated position (James)
Can see others and hear questions Responds to questions and write answers (James)
Tone and pattern of speech altered Pattern of speech altered
Describe out of body experience—Feeling of being
possessed by the god Apollo
Altered state—experienced religious revelations (James)
Free Association—images not obviously connected
Free Association—random thought pattern not obviously connected to
initial question (James)
Recovers rapidly Complete recovery in 5 – 15 minutes from full operable anesthesia (Herb)
Amnesia of events while under inﬂuence Amnesia of event while under inﬂuence (Lockhardt, James)
Based on evidence from Plutarch, Plato, Lucan, and other ancient authors, as well as depiction of Pythia on a vase from the ﬁfth century.
The Delphic Oracle 193
to the subject at hand (Table 1). The second description is
that of an apparently rare event of a delirious, ataxic, and
combative woman, described as in a frenzy. Both
descriptions are consistent with intoxication by ethylene
and the early stages of anesthesia. This was a naturally
occurring vent. Strict control of the ﬂow of gas would not
exist and therefore control of the depth of anesthesia
would be crude, if at all. The likelihood of an adverse
event is high with hundreds of subjects over the ten
centuries using a poorly controlled source of gas.
Lockhardt et al., in their description of the ﬁrst human
experiments with ethylene as an anesthetic gas, reported
10 of their 12 subjects had a very pleasant experience.
However, two of the 12 had periods of excitement,
confusion, and combative behavior.
An interesting modern illustration of the power of
mild anesthesia to produce a religious visionary state
comes from the philosopher William James who, during
the late 19th and early 20th century, experienced
religious mysticism and “extraordinary revelations”
while experimenting with nitrous oxide. Descriptions
of his “sessions” are similar to descriptions of the
“normal” Pythia (24,25).
The most dramatic and detailed descriptions of the
Pythia are during sessions gone awry. This situation,
however, is not unlike the modern medical literature
where case reports of difﬁcult cases or adverse events get
published in great detail, while the many “normal” cases
go unrecorded and unpublished.
The most reliable documentation of the Pythia during
her mantic sessions comes from the essayist Plutarch. His
description of a mantic session gone awry correlates well
with the effects that have been reported from the
excitation phase of anesthesia: confusion, agitation,
ataxia, and delirium. Plutarch described how a rich
deputation from abroad had come to the temple for a
consultation. The preparatory rituals indicated it was not
the proper time but eventually the Pythia was forced to
take her position on the tripod by the temple priests who
were interested in satisfying the rich clients.
She went down into the oracle unwillingly and half-
heartedly; and with her ﬁrst responses it was at once
plain from the harshness ofher voice thatshe was not
responding properly; she was like a laboring shipand
was ﬁlled with a mightyand baleful spirit. Finallyshe
became hysterical and with a frightful shriek rushed
toward the exit and threw herself down, with the
result that not only the members of the deputation
ﬂed but also the oracle-interpreter Nicander and
those holy men that were present.
Marcus Anneeaus Lucanus (Lucan) relates another
story of a mantic session gone awry. It is the story of
when the Roman Governor and General Appius Claudius
consulted the oracle. Appius Claudius desperately
needed a consultation concerning which side to join in
the Roman civil war between Caesar and Pompey. He
had traveled a great distance; however, it was not the
seventh day and the oracle was not open for business.
The Roman general forced the oracle to open for him and
forced the Pythia down into the chamber against her will.
She initially dreaded the oracle recess of the inner
shrine, she halted by the entrance and counter-
feiting inspiration uttered feigned words from a
bosom uninspired; with no inarticulate cry of
indistinct utterances proved that her mind was not
inspired with the divine frenzy. Her words that
rushed not forth with the tremulous cry, her voice
had not the power to ﬁll the space of the vast
It is interesting to note that the ancient Greeks noted a
change in her speech, both in tone and in pattern. The
idea that lack of indistinct utterances proved her mind
was not inspired, suggests recognition of a different
clinical presentation during the time of “possession.”
Appius Claudius was not happy with the initial efforts of
the Pythia and is reported to have shouted down to her:
Profane wretch. I have come to inquire about the
fate of this distracted world. Unless you stop
speaking in your own voice and go down to the
cave for true inspiration the gods whose oracles
you are taking in vain will punish you—And so
Lucan, then describes how, terriﬁed by the Roman
General, the Pythia entered the adyton.
And her bosom for the ﬁrst time drew in the divine
power which the inspiration of the rock, still active
after so many centuries, forced upon her. At last
Apollo mastered the breast of the priestess. Frantic
she careens about the cave, with her neck under
possession, she whirls with tossing head through
the void of the temple she scatters tripods that
impede her random course.
What they appear to be describing are consistent with
the excitation phase of general anesthesia. Lockhardt
et al., when working with ethylene, describe a period of
ataxia after ethylene intoxication and later describe two
of their 12 subjects going through a period of excitement
Spiller, Hale, and De Boer194
“so that restraint by holding down of the extremities was
Another piece of supporting evidence is the report by
Plutarch of a sweet odor like that of perfume that would
drift to the outer sections of the temple from the adyton.
Ethylene has a slight smell that is described as sweet with
odor recognition at 700 ppm (11). That this odor was
detectable in the outer sections of the temple, after
diffusion over a large area, strongly suggests that greater
concentrations existed in the enclosed adyton where the
Pythia sat. The unique setup of the temple at Delphi, with
a history of a recessed enclosed cell, would tend to
concentrate the fumes around the Pythia allowing for a
more signiﬁcant exposure (Fig. 4). Also there is
archeological evidence of efforts by the Greeks to
concentrate the fumes by capping the vent and funneling
it through a directed opening (26). It is suggested that the
tripod of Pythia was then placed directly over this
funneled gas jet.
Historically with ethylene, a mixture of 70– 80%
ethylene and 20– 30% oxygen was used to produce full
operable anesthesia. Mixtures of 20% ethylene and 80%
oxygen were also used successfully (13). A concentration
of less than 20% would be capable of producing an altered
mental state while allowing her to remain conscious. This is
something that could easily be produced using a directed
vent in a small, enclosed chamber.
Another intriguing piece of evidence is offered by the
sole representation of the Pythia existing from the period
when the oracle functioned. It is interesting to note the
unusual slumped posture of the Pythia, in a period when
Greek human forms were proudly rendered with rigid
erect posture (Fig. 1). The artists of the period did not
attempt to portray her as raving and ﬂailing, nor as erect
and alert, but rather slumped over, as one would expect
from a mildly anesthetized woman.
Another example from the ancient texts that suggest
mild anesthesia is the report that the Pythia did not
remember her utterances or other events after she had
recovered. This is typical of the ﬁrst stage of anesthesia,
sometimes referred to as the stage of amnesia and
analgesia (27). Luckhardt et al. also describe amnesia of
the period under the inﬂuence of ethylene (12).
Several other interesting similarities exist but their
value is unclear. The ritual to prepare the Pythia for her
ordeal, for instance, involved fasting the day of the
ordeal. Similar advice is given to patients undergoing
anesthesia to fast the night before surgery. The well-
known side effect of nausea and vomiting may have been
learned by the ancient Greeks and incorporated into their
In conclusion we believe that: (1) the ancient texts all
consistently refer to a gas or breath from a cavern as the
source of the marvel at Delphi, (2) the geological studies
show the existence of conditions for producing
hydrocarbon gases in a manner consistent with the
ancient texts, and (3) intoxication by one of the
hydrocarbon gases, ethylene, produces effects consistent
with the descriptions of behavior of the Pythia in the
ancient texts. We believe the probable cause of the
trancelike state used by the Pythia at the oracle of Delphi
during her mantic sessions was produced under the
inﬂuence of inhaling ethylene gas or a mixture of
ethylene and ethane from a naturally occurring vent of
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