BY THE standards of boats built by desert-island castaways, the Providence was a thing of beauty. Thirty-three feet long, and made of timber from the shipwreck that had stranded them, she was simple but seaworthy. She also offered the only viable route back to civilisation for more than 200 refugees. As a first step, that meant a westward journey of 500km or so to Madagascar, where the wrecked ship had come from. If you arrive on a ship—a brand-new transport three-masted schooner belonging to the French East India Company—you cannot all leave on a raft.

Whether the castaways were on land controlled by the Company, which projected France’s imperial ambitions in the eastern hemisphere, was anybody’s guess. The charts used by the captain of the doomed ship, L’Utile, on July 31st 1761 indicated nothing but ocean for hundreds of kilometres. Coming off a fortnight of unfavourable winds, he had little time for officers fretting about a probably mythical “Île de Sable”—sandy island—in the area. At half past ten on a moonless night, a coral reef stopped the ship in its tracks. By sunrise, L’Utile had been lost.

The Île de Sable, if indeed this was it, was not hospitable. It is so small that a swift walker can get round it in an hour, and so barren, bar a few bushes, that it can barely support human life. Winds and waves, rolling uninterrupted from Antarctica 5,000km to the south, batter it incessantly. More recent study has established it as the tip of a dormant volcano rearing up from 4,500m below, in the depths of the western Indian Ocean.

As they landed on the island on the night of the wreck, some of the crew supposed it inhabited. But the dark-skinned “locals” they encountered had come on the same ship, just a different part of it. Below deck 160 or so slaves had languished, men, women and children. Nearly half of them had died in the night, probably drowned under the nailed-down hatches. That still left 88, two-thirds of them men, now unshackled.

They had been a secret, albeit an open one. The captain had picked them up in Madagascar, as a bit of side business tolerated by the Company. He was knowingly flouting a French ban on slave-trading in its Indian Ocean territories—though one motivated more by concerns that a British blockade would leave extra mouths to feed on its precarious island colonies, than by common humanity.

Perhaps because of the French crew’s numerical superiority—123 had survived—the social order that existed on L’Utile carried through on land. Even the ship’s log was kept as before. It is now stored in the French ministry of defence’s archive. It continued to note the wind and weather, but also recorded the island’s new arrangements. In particular, it recounted how Barthelemy Castellan du Vernet, L’Utile’s first officer, emerged as the leader to replace the captain, shocked speechless by the crash. It was Castellan who had made the decision to scupper L’Utile by cutting her rudder in the hope that more men might be saved.

The island provided fish, turtles, birds and eggs, but at first no water

Within days Castellan, whose younger brother had died in the wreck, had sentenced a man to death for stealing some of the rations that had spilled out of the ship. L’Utile had disgorged 22 barrels of flour, 200kg of beef and other provisions; the island itself provided fish, turtles, birds and eggs. But there had been little water on the ship, and none could be found on the island—until, after three days of chipping through volcanic rock, a brackish, milky liquid welled up. The men rejoiced, and the condemned sailor was pardoned. By then, though, 28 castaways had died of thirst. All were slaves.

With water assured, things got easier. Members of the crew, from cook to priest, resumed their roles on land. If tensions arose, they were not recorded in the ship’s log, which soon resumed its focus on the weather. (Entries for August: “18th and 19th: Bad sea. 20th: Calm sea.”) Using sails and fragments of L’Utile’s masts, the French set up camp on the west of the island, near a beach where one of the anchors from the wreckage protruded from the surf. The slaves huddled at the northern tip.

A ship was spotted far off on August 9th; it cannot have missed the noise and smoke from two barrels of gunpowder the castaways detonated as flares. But it continued on its way to India.

Castellan, who had sailed on slave ships before, knew there was a risk of disorder. A vessel had to be built, and quickly. But three problems arose. The ship’s carpenter had no actual woodworking skills. There were no trees on the island; all wood had to be salvaged from the wreck, much of which was submerged. And the crew was disinclined to work, all but 20 preferring the more leisurely task of bird-hunting to manual labour. Castellan shook off the first problem: though he had no naval-architecture training, he skilfully sketched plans for the Providence. The problem of the slothful crew could be overcome with the help of the Malagasy slaves. “The slaves toiled with great zeal in this work,” according to a contemporaneous account. Nothing suggests they were coerced into it. If the white man offered the only way off an uninhabitable island, reason suggested any enmity was best left aside until after the escape. That left the second problem, of insufficient wood. Or rather, the right kind of wood. There was enough to build a seaworthy barge with sides five feet high. But Castellan’s plans for the Providence were predicated on a 45-foot end-to-end beam underpinning the boat. L’Utile had not been that generous: the longest beam at hand was only 33 feet. Scale down a boat’s beam and length in proportion, and her capacity shrinks by nearly half. There is no record of any discussion of which half of the stranded island community should have first dibs on this smaller boat. It is hard to imagine one was held. On September 27th 1761, two months after the shipwreck, it was the 123-strong white crew who boarded the Providence—including around 100 who had played no part in its construction. The abandoned were left with three months’ provisions and a letter recognising their good conduct: important if the slaves were to prove to a passing captain that they had not been ditched for having caused trouble.

But the most important reward they were given for their loyalty and their labour was also the most intangible: a promise that someone would come back for them. Castellan reckoned that might be possible in a couple of weeks, maybe a month if the weather turned. Whatever happened, the provisions he had left would be ample, he thought, to cover the time for the crew to reach Madagascar and return.

Weeks passed, then months, then years.

Desert island risks

“We affirm with truth that, after God, we owe our escape from that island to [Castellan] alone…we acted only to obey his counsel and orders,” the crew unanimously proclaimed after they reached dry land. It had taken just four days for the Providence to arrive in Foulpointe, a port in eastern Madagascar. The men had travelled crammed together as the slaves once had, but just one died en route. They were greeted with amazement. But here Castellan’s winning streak ended. The crew’s declaration mentions his endeavours to retrieve the slaves. “However,” it notes, “he couldn’t secure the spare sails required to do so.”

Castellan’s abilities did not extend to the political realm. Everything suggests his desire to return was genuine. But it was not shared by Company higher-ups administering the islands. His inability to secure fresh sails—an unlikely impediment, given the constant coming and going from Foulpointe, a trading hub—was only his first hurdle.

A few days’ deferment turned into weeks. As objects of curiosity, the entire crew was ordered to Île de France, now Mauritius, the local bastion of French power. By the time they arrived, on November 25th, the slaves had been stranded for two months.

Local grandees on Île de France saw no rush to intervene. The governor, Antoine-Marie Desforges-Boucher, in particular, displayed a palpable lack of enthusiasm for Castellan’s flight of mercy. Ships had suddenly become scarce, he explained, not least since L’Utile’s wreck. Once a distant threat, Britain’s navy now loomed more closely, threatening the security of supplies to the islands. And with all those delays already—not anybody’s fault, of course—was it even likely the slaves were still alive?

Historians suspect ulterior motives. Desforges-Boucher is known to have had a sideline in trading slaves. A cargo of 200 Mozambicans he had ordered were on their way to the islands. The ban on trading had helped firm up prices and boost margins. There seemed no sense in bailing out a hapless rival at the last minute, especially when the British could be made to carry the can.

Whatever the reasons, the two men ended up at loggerheads. Desforges-Boucher promised a ship once the war with Britain ended (the Seven Years’ War dragged on until 1763), while Castellan vowed not to leave the islands until the slaves had been retrieved. As so often happens, stalemate favoured the bureaucracy. While most of the crew returned home, Castellan took a position aboard a supply ship ferrying goods around the islands. He nearly scored an unlikely success: in January 1762, the captain of his new ship was amenable to a detour via Île de Sable. The plan was foiled when the Royal Navy landed on a nearby island.

By September of that year, 12 months after the Providence had sailed, Castellan realised the futility of his quest and returned to France. Yet his lobbying continued, if letters later found in various government archives are to be believed. His cause was aided by the publication of a real-life-adventure pamphlet printed in Amsterdam that turned the castaways into a minor cause célèbre. Mysteriously, a hastily added footnote even suggested a happy conclusion for the slaves: “A ship has been sent from Île de France to rescue these wretched souls.”

It was not so. The suggestion of benevolence when none was forthcoming infuriated one reader. In the copy of the pamphlet held in the French Navy archives, the erroneous footnote is annotated by hand. “It had been promised one would be sent, it has not been done as yet.” Irène Frain, a French author who has written a fictional retelling of the slaves’ fate, is adamant the handwriting is Castellan’s.

A decade later, he was still writing pleading letters. The bankruptcy of the Company in 1769—the cause of great financial hardship for Castellan—had led to new administrative arrangements in France’s Indian Ocean territories. Perhaps that explained why in 1772, for no stated reason, the secretary of the navy was now willing to back a rescue mission. Nobody knew then, more than a decade on, whether any slaves might have survived. In any event, the order was ignored for another three years.

The island they called home A ship was dispatched in August 1775, 14 years after the original crash. It reached Île de Sable, but heavy weather prevented it from doing much more. Worse, it added a castaway to the island; one of the two men aboard a dinghy launched from the ship was left stranded there. The expedition at least answered any remaining questions of whether the island was inhabited. Lying offshore (he could get no closer), the captain saw that a community of sorts seemed to have endured. There were 13 people in all—14, with the newly added sailor. Buildings had been erected. The anchor from L’Utile still protruded from the surf. More surprisingly for a woodless island, a plume of smoke suggested fire. A rescue mission looked harder than expected. But the new governor of Île de France was made of sterner stuff than Desforges-Boucher. It helped that by 1776 Britain had bigger colonial problems to contend with than minor islands in the Indian Ocean; there, France ruled supreme. Still, the task required unexpected effort. Two more ships were commissioned to save the castaways, but failed. The fourth succeeded. In November 1776, 15 years after Castellan had left, the Dauphine, a corvette captained by Jacques-Marie Lanuguy de Tromelin, at last got favourable winds. At Île de Sable a dinghy was dispatched from it. By then, the only inhabitants were seven women wrapped in clothes made of birds’ feathers. One of them—oddly, on an island with no men—held an eight-month-old baby boy.

With no pomp or ceremony, they were ferried to the Dauphine and evacuated. In the space of a morning, the island went from being inhabited and unnamed to being uninhabited and named after the man who had made it so: Tromelin Island.

Why had only seven castaways survived, when 14 had been spotted weeks before? It seems the newly marooned sailor had tried his luck as a latter-day Castellan. With the help of the now-natives, one assumes, he had salvaged whatever could still be used from L’Utile’s wreck and built his own Providence. Sails were improvised from birds’ feathers. Unlike Castellan, the unnamed sailor had taken some of the slaves: the last three men and three women. Also unlike his predecessor, he failed to reach Madagascar.

One little island an everywhere

Back on Île de France, the women were declared free and baptised. Semiavou, the mother of the child (and the only one whose name was recorded) was christened Eve. The boy was named Moïse, after the prophet who was born a slave and whose name means “drawn out of the water”.

Whatever meagre accounts of life on the island were collected—there was no great eagerness to do so—have been supplemented since by Max Guérout, a French naval researcher who calls himself an “archaeologist of distress”. With teams of volunteers, he has been on many expeditions to the island since 2006. Digging through metres of sand accumulated since the 18th century, they have unearthed a dozen buildings erected by the slaves. The stone walls are a metre-and-a-half thick to withstand the wind and make up for the lack of cement. With no materials at hand to craft a roof, the rooms are tiny. One of them had no entrance, for unknown reasons. They made unseemly accommodation: in Madagascar stones are used for tombs, not buildings.

In fact no tombs or bodies have ever been found. This makes it difficult to establish what happened to the other slaves. Of the 80 or so left behind, less than half are accounted for. Eighteen are thought to have embarked on a raft shortly after they were abandoned; with no textile sails, it is assumed they never reached land. Most of the others died early on, including some women in childbirth. Moïse, as he later became, was the only child to survive. With his light skin, it was speculated but never confirmed that he was the son of the white sailor who had arrived the year before.

The same brackish well that had saved the sailors had slaked the slaves’ thirst for 15 years. A fire started in Castellan’s day had been kept burning since then, fed with scraps of wood gathered from L’Utile. The only cloth available consisted of birds’ feathers woven together using ropes from the wreck, hence the women’s attire that had startled the sailors. Basic metalwork—copper for eating implements, lead for water cisterns—had continued at a furnace set up to build the Providence.

The women declined to return to Madagascar, where they would probably have fallen back into slavery. Their wish for a quiet life on Île de France seems to have been realised: nothing is known of them thereafter. Castellan, by then a hospital administrator in Brittany, may have heard of their rescue; his reaction was not recorded. He died in 1782. Desforges-Boucher, who stayed on the island after relinquishing the governorship in 1767, perished on the voyage back to France. Tromelin returned to France only to have his family’s estate seized in the revolution of 1789.

That the story of Tromelin Island has survived at all is largely due to one of the revolution’s central figures, the Marquis de Condorcet. He included the harrowing tale of the castaways in his pamphlet “Reflections on Negro Slavery”, published in 1781. His account is confused on the details, mentioning 300 slaves stuck on an island that was submerged by tides twice daily. But the gist of the story is damning of the behaviour of the French authorities: “Seven negro women and a child born on the island were found, the men having all died, either of misery, or hopelessness, or attempting to escape.”

The pamphlet galvanised anti-slavery campaigners, and was reissued seven years later. In only a matter of years, Desforges-Boucher landed on the wrong side of history. Debates in the new Assemblée Nationale in February 1794 decried the practice as lèse humanité, a precursor to today’s crime against humanity. The new regime abolished slavery—a decision that was never properly implemented, and ultimately reversed.

As for Tromelin Island, little happened there for the next hundred years. In 1810 Britain seized control of Île de France, and so, at least in theory, inherited its distant cousin as part of its empire. In 1867 the Atieth Rahamon, a three-masted ship carrying 10,400 bags of sugar, crashed into Tromelin, but the crew were rescued.

The island’s precise co-ordinates were established only in the 1950s. France, keen to keep some sort of foothold in the Indian Ocean ahead of the impending decolonisation of Madagascar, established a weather station on Tromelin in 1954. There is now a cluster of modern buildings—erected, with no little irony, using labourers imported from Madagascar—and a runway of crushed coral runs the length of the island.

Today the weather station needs no staff, but French soldiers fly in every other month to rotate a crew of three people. Their presence serves mainly to weaken long-standing, if half-hearted, claims of sovereignty by Mauritius. One hut doubles up as a fully-fledged post office adorned, like all French municipal buildings, with a portrait of François Hollande, the island’s nominal president. Mr Guérout and his archaeologists of distress arrive periodically to dig up some corner of the island. A plaque commemorating the betrayed slaves was erected in 2013: not far from L’Utile’s rusting anchor, still stranded in the surf, battered by the waves.