Too small to be seen properly with the naked eye, this little shell belongs to a marine creature called Argyrotheca. It鈥檚 hardly impressive. And it鈥檚 certainly not something worth dying for. But the attempt to retrieve it from the bottom of the Caribbean off the island of Jamaica cost a young 19thcentury geologist his life. Lucas Barrett鈥檚 career ended abruptly when he was just 25. Had he lived longer, he might have become one of the great names of geology. Instead he achieved a distinction of another sort-as one of the first people to die of the bends. The shell is now tucked away in a drawer at the Natural History Museum in London, a tiny memento of a life cut short.
LUCAS BARRETT was an over-achiever. His father owned an iron foundry in London, but young Lucas鈥檚 ambitions were rather different. By the tender age of 18 he was already keeping company with eminent scientists. And by 21 he was head of a geological survey in the Caribbean. But four years later he was dead, a victim of his insatiable curiosity, perhaps coupled with the overconfidence of youth.
Barrett started out in an ordinary enough way, as a schoolboy fossil fanatic. Outside school hours he rummaged about in chalk pits for additions to his collection, and during his holidays he made frequent trips to the British Museum to ask the experts to identify his finds. At 16, his father packed him off to Germany to study chemistry. But Barrett鈥檚 mind was on fossils even then, and he managed to fit in a walking tour of Bavaria to search for new ones.
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By this time, Barrett was something of an expert himself, and in 1855 he became the youngest ever fellow of the Geological Society. That year too, he was invited to join a scientific yachting voyage that took him from Shetland to the Arctic. It began his fascination with undersea geology, probing bits of the Earth鈥檚 surface far removed from the everyday world. The expedition made him handy with a dredge-just about the only means of gathering specimens from depth-and also introduced him to the brachiopods, the group of animals to which the fateful Argyrotheca belongs.
To the untrained eye, brachiopods look much like clams and their kin, the bivalve molluscs. They all have two halves to their shells, but in most other respects brachiopods are different. In evolutionary terms, the brachiopods have been playing a long game. One species, Lingula, has remained unchanged for almost 500 million years. More importantly, in past geological ages the seas teemed with a multitude of species, and their fossilised remains are a good guide to the age of a rock.
Barrett鈥檚 experience in the rough, cold waters of the North Atlantic quickly paid off. In 1859, he was offered a job he could hardly refuse, as director of the government鈥檚 Geological Survey of the British West Indies. Despite the arduous journey, the prospect of isolation and tropical diseases, and the fact that he had just got married, Barrett sailed off to the Caribbean, taking his new wife with him.
Jamaica wasn鈥檛 much of a honeymoon. Barrett was hard at work as soon as he arrived. He quickly discovered one of the finest fossil deposits in the world-the Bowden shell bed, later famous for its magnificent Pliocene molluscs. Barrett also worked hard on the island鈥檚 geology, re-dating its rocks by looking at the fossils entombed in them, a technique that was still being developed when the island was originally mapped in the 1820s.
It was too good to last. In 1862, Barrett returned to England on leave and showed some of his specimens at the London International Exhibition, a huge event intended to highlight progress in science and technology. True to form, Barrett won a medal at the exhibition, but he also made what turned out to be his fatal mistake. He bought a diving suit so that he could explore the sea around Jamaica.
The diving equipment in use at the time had been developed little more than a decade earlier. It consisted of a heavy, watertight suit and a metal helmet fitted with one or more glass-fronted portholes for the diver to peer through. Air was supplied through a tube attached to a large pump, usually operated by a couple of energetic assistants.
The pressure inside the suit had to match that of the surrounding water, so the deeper the dive, the greater the air pressure required to supply the diver in his cumbersome costume. Despite the restrictions this sort of diving dress imposed on movement, it stayed in routine use until the invention of scuba diving a century later.
Barrett鈥檚 idea was to use his new suit to investigate reefs, where the sharp lumps and bumps of coral made dredging impossible. On 17 December 1862, he made his first dive in the shallow water off the Port Royal cays, south of Kingston. Barrett stayed underwater for half an hour and then returned safely to the surface.
Two days later, despite pleas from his friends, he made a second, longer dive in deeper water. This time something went wrong. Barrett floated to the surface, dead inside his suit.
鈥淎ccording to the evidence given by the men, Mr Barrett went direct down from the boat into deep water by means of a rope-ladder,鈥� reported one of his friends in The Geologist. 鈥淭he pumps were worked uninterruptedly . . . but they noticed that he remained below longer than previously, and suddenly, to their horror, they observed his body floating at the surface of the water, a little distant from the boat. They got to him as quickly as possible, without ceasing pumping (so they declare), and on the removal of the helmet found him apparently dead.鈥�
The inquest returned a verdict of death by drowning. Yet Barrett鈥檚 clothing had been quite dry, a fact that those who examined him could hardly have failed to notice. Far more likely is that Barrett came back to the surface too quickly and died of decompression sickness-the bends.
Why did Barrett shoot up to the surface so suddenly? Perhaps the outflow valve of his suit jammed, inflating it and forcing him upwards at speed. Perhaps something happened on the reef that made him panic and head upwards as fast as he could. Perhaps, being a confident and adventurous young man, he simply ignored the risks. 鈥淚t looks like an instance of self-reliance carried too far, and a valuable life sacrificed, apparently, by the neglect of those precautions which any one less daring would have observed,鈥� wrote his obituarist in The Geologist.
Whatever the truth, Barrett didn鈥檛 make his ascent empty-handed. When his colleagues recovered his body, they found that he had collected some of the specimens he was diving for. In a little pot tied to his diving suit was a handful of seashells, among them Argyrotheca.