After 1962 Michel Siffre did not go underground alone again for ten years. He sent other people. The French army, which wanted to know how long a man could be kept awake, paid for most of it; the caves were in the Audibergue, the limestone country thirty-odd miles north of Nice, where the Institut Français de Spéléologie that he had founded could reach them; and the subjects were cavers, because, as he said in 2008, nobody else was motivated enough to stay. The protocol was his own of 1962. The subject telephoned the surface at every waking, meal and sleep, said what time he thought it was, and was told nothing. The surface wrote down the real time beside the guess. The newspapers called the subjects, following the French, speleonauts.

Laures and Senni, 1964 to 1965

The first two went down a fortnight apart, into two separate caves about 330 feet deep, in the winter of 1964: Antoine Senni, a furniture maker of thirty-five, on 30 November, and Josiane Laures, a midwife of twenty-six who had been caving for three years, on 14 December. Each had a telephone to the base camp, 4,000 feet up in the Alps; Laures, Reuters reported, gave the team her pulse, temperature, weight and breathing at every call.

The losses began at once. On New Year’s Day 1965, Reuters reported from Nice, Laures went to sleep at nine in the morning believing it was the night of 26 December, and Senni, further out, thought it was 22 December and began to dress the Christmas tree that had been lowered to him. By 17 February, Siffre told the agency, Laures was “still going strong” after two months, passing the time reading novels and painting. On 11 March he telephoned her to say it was over. She thought it was 25 February. “It is not true,” she said. “You must be lying. Have I really been here three months already?” And then: “But I have not finished all the things I wanted to do while I was here.” She had read, painted, written an 80,000-word diary, woven baskets and knitted Siffre a pullover, and she had put on seven or eight pounds. The worst of it, she told reporters, had been the colour: the red of the cave walls under her electric lamp, which she came to see everywhere. “I even had red dreams.”

It took the CRS mountain police more than three hours to bring her up, and the hauling gear jammed thirty feet from the top, leaving her and her escort, Sergeant Canova of the 1962 team, dangling while Siffre’s men wound them up by hand for forty minutes. She came out on 12 March after 88 days, tired, her pulse at ninety, saying she felt like an old woman and that she was ready to go down again and stay longer; she was carried half a mile through thick snow on a stretcher to a police helicopter, flown to Nice, and put under three weeks’ medical observation. Senni, in the next cave, knew nothing of it. On the morning she came up he believed it was 27 January; four days later, when he had beaten Geoffrey Workman’s record of 105 days without knowing it, he believed it was the 28th. He came up on 5 April after 126 days. Once, Siffre recalled in 2008, Senni slept for thirty-three hours with a microphone on his head, and the team above could not tell whether he was dead until, at thirty-four hours, he snored, and a few minutes later rang up to give his pulse. “Today,” Siffre said, “doctors would have to wake him up.”

The physiologists got their first proper look at the body in these two. Siffre, Reinberg, Halberg and others published the two cases in the Presse médicale in 1966, with the heart rate keeping a day of 24.8 hours in the man and 24.6 in the woman; Reinberg’s group put Laures’s body temperature in the Comptes rendus of the Académie des sciences the same year, and found her menstrual cycle shortened underground from twenty-nine days to twenty-six.

The six months of 1966 and the forty-eight-hour day

In 1966 a man did six months. The scientific paper that came out of it, by Colin, Timbal, Boutelier, Houdas and Siffre in the Journal of Applied Physiology in 1968, has been read for this piece only in summary, and does not name him there; later accounts name him as Jean-Pierre Mairetet, who had kept the surface watch at Scarasson in 1962. The paper’s finding, as a 2019 review summarised it, was that his cycle of rest and activity started near twenty-five hours and within ten days had stretched to forty-five hours between one waking and the next, while his body temperature went on keeping a day of about twenty-four. The sleep-wake cycle and the temperature cycle had come apart.

That was the beginning of the forty-eight-hour day. On 22 August 1968 two more men went down the Olivier cave in the Audibergue, about 200 feet deep, to live apart for four months: Philippe Englender, thirty, who had been on the 1961 expedition that found the Scarasson ice, and Jacques Chabert, twenty-nine. Chabert was kept under constant artificial light, which disturbed his sleep for the first days; Englender controlled his own. After thirty days, Reuters reported in October, Englender “fell into an almost exactly regular 48-hour cycle, working for up to 36 hours at a stretch and then sleeping about 12 hours”. Siffre told the agency the tendency “had been suspected before but had never been demonstrated so clearly”. By Christmas Chabert had followed him into it. On Christmas Day, while three American astronauts circled the moon, Englender believed it was 15 November and Chabert 7 December; both came up on 15 January 1969. Siffre told Paris Match that what interested him now was speleology applied to space.

Michel Jouvet’s laboratory in Lyon, which had the brain-wave records, published the series in 1974 under a title that gave the phenomenon a name, “bicircadian periodicity”: with variable latencies, all the subjects had reached a rhythm of about thirty-four hours awake and fourteen asleep, and the amount of dreaming sleep in each night rose with the length of the waking before it. The French army, Siffre said in 2008, then looked for drugs that would lengthen dreaming sleep, in the hope of giving soldiers days of thirty hours or more. In 1988, at a European Space Agency colloquium, Siffre summed up seven long confinements of two to six months: five of the subjects had abandoned the circadian day for a “circabidian” one, some within eight to fifteen days, some after months, and kept it for weeks. He himself, in Texas in 1972, had caught it only twice.

Véronique Le Guen, 1988

The last of Siffre’s long stays was a woman’s. On 10 August 1988, with reporters at the mouth of the Valat-Nègre cave in south-central France, Véronique Le Guen went down to live alone, with neither calendar nor clock, in what the American magazine In Health later called a beautiful but hostile living room. Her partner, the adventurer Francis Le Guen, had been all for it. She was young and athletic, and Siffre, the magazine reported, had said when he watched her dive: “If it’s Véronique, we all win.” Eight days after descending she began a “day” that lasted seventy-four hours, forty awake and thirty-four asleep, without knowing it. She came out after 111 days, in November 1988, a world record.

The darkness, the magazine wrote, stayed with her. A physician who met her soon after the experiment was struck by obvious symptoms of something wrong. Within two years she had killed herself. The magazine’s writer, Joseph Anthony, went to Paris to ask about her, and found the question of whether the cave had done it unanswerable and unavoidable. Francis Le Guen did not blame Siffre. One of those interviewed said she had committed suicide “and there’s no ifs, ands, or buts” that her rhythms had been different underground; another observed that the breaking of a person’s internal synchronisation “can be associated with very serious depression in some individuals”. Siffre, asked whether he had ever thought of suicide in Midnight Cave, said “Oh, no, never”, though he had written in 1975 that he had; asked whether he worried about the depression that he and so many others had suffered, he said “Oh, no, no, no!” and that he already had plenty of volunteers.

The others, elsewhere

The caves were never Siffre’s alone. In Australia in the autumn of 1962 a Darwin businessman, Bill Penman, went into a hot cave in the Northern Territory to beat the Frenchman’s record and gave up after sixty-four days with his eyesight failing. In Yorkshire in 1963 Geoffrey Workman did 105 days at Stump Cross Caverns, knowing the time, and came up fit. In 1989 an Italian woman, Stefania Follini, spent 131 days alone in a cave in the United States with the space agencies’ interest; the immunologists who studied her blood, and who put her name among their authors, found her white cells changed and her bones lighter by 2 per cent. An Italian man, Maurizio Montalbini, stayed down for 366 days, the record the Italian caving press still cites, in a programme of his own. The record for solitude underground, as the British cavers’ newsletter that keeps the table records it, belongs to a Serb, Milutin Veljković, who spent 463 days in a cave in 1969 and 1970.

What none of the later stays reproduced was the thing Siffre had in 1962 without meaning to: a subject who did not know he had a clock. Every speleonaut after him went down knowing what the surface log would show. They were still wrong about the date by a fortnight a month, and still said, when the telephone rang, that it could not be true.

Sources

• Reuters and Associated Press reports in the Evening Post (Wellington) and the Press (Christchurch), via Papers Past: “Isolation Has Them Back At Xmas,” 2 January 1965; “General News,” 18 February 1965; “French ‘Cave Girl’ Due Up From Underground Isolation,” 12 March 1965; “3 Months Alone In Cave,” 15 March 1965; “Cave Girl Sees Sunlight After 88 Days Underground,” 17 March 1965; “Pothole Champ—But Does Not Know It,” 18 March 1965; “48-Hour Day,” 25 October 1968; “Out Of Touch,” 26 December 1968; “Underground Endurance Record Effort,” 19 September 1962, on Penman’s party. 15 March 1965, 25 October 1968, 26 December 1968
• Joshua Foer, “Caveman: An Interview with Michel Siffre,” Cabinet 30, Summer 2008. The army’s funding, the subjects who were cavers, Senni’s thirty-three hours, the dreaming-sleep finding and the search for drugs. cabinetmagazine.org
• M. Siffre, A. Reinberg, F. Halberg, J. Ghata, G. Perdriel and R. Slind, “L’isolement souterrain prolongé. Étude de deux sujets adultes sains avant, pendant et après cet isolement,” Presse médicale 74, 915–919, 1966; A. Reinberg, F. Halberg, J. Ghata and M. Siffre, “Spectre thermique (rythmes de la température rectale) d’une femme adulte avant, pendant et après son isolement souterrain de trois mois,” Comptes rendus de l’Académie des sciences 262, 782–785, 1966; J. Colin, J. Timbal, C. Boutelier, Y. Houdas and M. Siffre, “Rhythm of the rectal temperature during a 6-month free-running experiment,” Journal of Applied Physiology 25, 170–176, 1968. Cited from their titles and as summarised in Zuccarelli and colleagues, below; the texts were not reached.
• L. Zuccarelli and colleagues, “Human Physiology During Exposure to the Cave Environment: A Systematic Review With Implications for Aerospace Medicine,” Frontiers in Physiology 10, 2019. The 24.8 and 24.6 hours, the menstrual cycle, the 45-hour cycle after ten days, and Follini’s 131 days (Sonnenfeld and colleagues, 1992). europepmc.org
• G. Chouvet, J. Mouret, J. Coindet, M. Siffre and M. Jouvet, “Périodicité bicircadienne du cycle veille-sommeil dans des conditions hors du temps,” Electroencephalography and Clinical Neurophysiology 37, 367–380, 1974, from the abstract in NASA’s Aerospace Medicine and Biology, supplement 143, 1975; M. Siffre, “Biological Rhythms, Sleep, and Wakefulness in Prolonged Confinement,” ESA SP-280, 1988, from the abstract on the NASA Technical Reports Server. archive.org, ntrs.nasa.gov
• Paris Match, 1 February 1969, on Englender and Chabert, read in snippets on archive.org. archive.org
• Joseph Anthony, “Journey Out of Time,” In Health, March–April 1991. Le Guen’s descent on 10 August 1988, the 74-hour day, the 111 days, her death, and the interviews in Paris. archive.org
• G. H. Workman, “An Experiment in Underground Living,” Memoirs of the Northern Cavern and Mine Research Society 2 (3), 1973, on Penman and on his own stay. nmrs.org.uk
• Peter and Julie Mohr, “Les Speleonauts,” RRCPC Newsletter 44 (1), October 2007, with the table of long stays, and Scintilena, 25 August 2024, on Montalbini. rrcpc.org.uk, scintilena.com