The largest migration of life on earth departs every night from the twilight zone, the kilometre-deep middle layer of open ocean in which the majority of living creatures can be found. As darkness falls, millions of tons of animals, ranging in size from the smallest arrow worms to the largest cetaceans, swim their way up to the photic zone to feed in relative safety, braving shallower waters under cover of night to gorge themselves on nutrients – and on one another – before plunging back into the gloomy depths as dawn begins to break. For a few short hours, the top thirty metres of the world’s great oceans teem like overstocked aquaria. The process, known as vertical migration, was discovered relatively recently, and as yet scant details of its natural history have been collected by marine zoologists, for whom many of the goings-on in the ocean’s deeper regions remain just as mysterious and out of reach as they were when ocean science began in earnest in the mid-19th century. ‘The great depths of the ocean are entirely unknown to us,’ Jules Verne declared in 1869, in the early pages of Twenty Thousand Leagues under the Sea. ‘What passes in those remote depths – what beings live, or can live, twelve or fifteen miles beneath the surface of the waters – what is the organisation of these animals, we can scarcely conjecture.’ Much the same could be said today, 140 years on from the voyage of the Nautilus, with less than 5 per cent of the world’s 320 million cubic miles of ocean having so far been explored, and an estimated 50 million unknown species thriving in its depths.
Like space exploration, a branch of science with which it is often compared, deep-sea oceanography is an extremely expensive and risky endeavour; in fact, more people have been sent into outer space than have ever journeyed into the dark zone, 2000 metres below the surface, and there are still only a handful of unmanned submersibles capable of reaching the deep-sea floor, six or seven kilometres down. What makes deep exploration so difficult and dangerous is the steady increase in hydrostatic pressure caused by the weight of water above. By 1000 metres down, the outside pressure has risen to 100 times that at the surface. By 5000 metres (just over three miles) down, the pressure will have increased to 500 atmospheres – some 3.5 tons per square inch – inducing levels of stress that few man-made objects can withstand. A popular trick among deep-sea divers is to strap a polystyrene coffee cup to the outside of their submersible, and, as they descend, watch it being slowly crushed to the size of a doll’s-house thimble – which is pretty much what would happen to their internal organs should the vessel spring a leak.
Given such an extreme working environment, oceanographers, perhaps more than any other scientists, are forcefully aware of the courage displayed by their forebears, whose achievements were all the more remarkable given the lack of reliable equipment and, more often than not, their lack of experience of the open sea. When HMS Challenger sailed from Sheerness harbour in December 1872 at the start of its unprecedented four-year voyage of oceanographic exploration, few among the team of onboard ‘philosophers’ had any inkling of the kinds of privation that four years at sea would bring. All of them, naturally, had studied Darwin’s account of his five-year voyage on the Beagle that had first appeared in 1839, but Darwin had sought to play down the hardships of life on board a naval brig, not least the misery of sharing a cabin with Captain Robert Fitzroy, whose temperament Darwin privately described as ‘a most unfortunate one. This was shown not only by passion but by fits of long-continued moroseness against those who had offended him,’ particularly the unfortunate Darwin, whose journals bear testimony to endless quarrels with the irascible Fitzroy – ‘some bordering on insanity’ – that marked their five years together.
But even if Darwin had been more candid in his account of the day-to-day realities of life on board the Beagle, it seems unlikely that any among that rising generation of natural scientists would have been remotely dissuaded from taking their chances on a voyage across the open seas: what did a few insults, dangers and discomforts matter when set against the chance to secure an immortal reputation? And so, by the middle decades of the 19th century, as Helen Rozwadowski observes, ‘the act of setting sail on the blue water’ had ‘shifted from unfortunate necessity into a heroic undertaking’. Now, the open ocean was no longer a void to be journeyed through as quickly as possible en route to civilisation, but an object of fascination in itself and, more to the point, a subject of state-funded research.
In Fathoming the Ocean, Rozwadowski sets out to explain the rapid rise of ocean science in the second half of the 19th century, a process which began, as she puts it, ‘modestly, at the shoreline’, with the early Victorian beachcombing craze that will be familiar to readers of Edmund Gosse’s Father and Son. In one of the book’s most celebrated sequences, Gosse recalls how his newly widowed father would ‘wade breast-high into one of the huge pools, and examine the worm-eaten surface of the rock above and below the brim’ in search of corals and sea anemones to add to his growing collection. Thousands of others were doing the same, and by the end of the century, according to Gosse, the rock pools of Britain – ‘the ring of living beauty drawn about our shores’ – had been all but stripped of their contents: ‘An army of “collectors” has passed over them, and ravaged every corner of them . . . No one will see again on the shore of England what I saw in my early childhood, the submarine vision of dark rocks, speckled and starred with an infinite variety of colour, and streamed over by silken flags of royal crimson and purple.’
But in spite of Gosse’s painful retrospections, the beachcombing craze was short-lived, not least because many of its leading exponents had graduated to hitching rides on fishing smacks and survey ships in search of rarer specimens. Rozwadowski’s account of these amateur oceanographers travelling on working vessels is a tremendous piece of historical retrieval, particularly in the way that the endless practical difficulties they faced while dredging for sea-floor samples are used to illustrate the social impact a generation of landlubber naturalists had on the professional world of the sea. It was, for example, the sailors rather than the naturalists who were expected to work the unfamiliar equipment. Since it often took an entire ship’s crew an hour or more to haul in a laden dredge, and even longer to help sort its muddy contents, many sailors ended up working 14-hour shifts thanks to the presence of these seasick scholars, most of whom ‘enthusiastically welcomed any chance to get off the ship’. They were always in the way, they complained about the food, they failed to learn rudimentary sea-going terms (even at the end of his four-year voyage the chief scientist on board the Challenger continued to reckon time by academic terms, much to the irritation of the officers and crew); still, Rozwadowski’s dredging nerds come across as a likeable bunch. I warmed especially to Edward Forbes, an Edinburgh medical student whose enthusiasm for marine research prompted him to compose a sort of middle-class shanty, ‘The Dredging Song’ (‘Hurrah for the dredge,’ it begins), which he and his shipmates sang together, and which was published in the Literary Gazette in November 1840. He also filled his letters with ‘fishy puns’, writing to a friend that his research on starfish proceeded ‘swimmingly’. It was a habit he shared with many other naturalist-dredgers, such as the American biologist William Stimpson, who wrote of arming his chartered schooner with a gun capable of firing seashells, so that ‘if they encountered a privateer, they could “make them SEA STARS (N.B. – Joke)”.’
As Rozwadowski observes, these songs and in-jokes were a product of the camaraderie that develops at sea, intensified, in the case of the early ocean scientists, by their outsider status aboard working vessels, as well as by the steepness of the learning curve that each of them faced every day. For in spite of their soft hands and their air of scholarly innocence, Forbes and Stimpson’s generation were intellectual pioneers, venturing bravely into worlds where the rules of fieldwork no longer applied, and where few of the species that were dredged up fitted any known category of life on earth. Some of the names that they gave to these startling new demersal species – Chimaera monstrosa, Synanceia horrida – serve as a permanent record of their discomfort and alarm as monster after monster was hauled to the surface, bloated and dead after its journey up from the abyss. Many of these swollen-eyed, poisonous creatures had clearly come from the hadal depths, several kilometres down, but how deep, exactly, were those depths, and how far down did one need to dredge before life would no longer be found?
Questions relating to ocean depth were surprisingly difficult for scientists to answer in the years before the introduction of sonar imaging. Soundings taken at the same co-ordinates could vary wildly from ship to ship, with no one able to tell precisely when the sea floor had been reached, since undercurrents tended to pull lines from their reels long after the sinkers had struck bottom. Consequently, a great deal of time at sea was spent experimenting with a range of sounding equipment in pursuit of a reliable ‘law of descent’ that would let the user know exactly when the sinker (a 32-pound shot attached to a specific diameter of sounding line) had landed. Every piece of kit, including the lines, would be tested and retested over the years, with hemp ropes and steel cables giving way in the end to cheap commercial packing twine, the only kind of line that did not break when hauled from a deep-sea sounding.
Oceanography remains a science of measurement and of arguments about measurement, and Rozwadowski is good at reconstructing the technical debates that so occupied its 19th-century founders. The notion of what constituted deep-sea dredging, for instance, changed almost from year to year as expertise spread and equipment was refined, pushing the definition of ‘deep water’ from 50 fathoms (90 metres) in the 1850s to well over 1000 fathoms by the 1870s. Forbes claimed in 1842 that life could not exist below 300 fathoms, and despite the growing body of evidence to the contrary, his azoic theory, as it was known, was difficult to disprove without reliable measurements. The deep-sea creatures could have been picked up by a rising dredge at any point during its ascent. It was only when a length of telegraph cable was raised for repair in 1860 from a known depth of 1000 fathoms off the south-west coast of Sardinia, heavily encrusted with a host of marine animals, that Forbes’s theory was definitively abandoned. Life, it appeared, could thrive without light in the enormous pressures of the deep.
There are, essentially, two sorts of ocean scientist: those who are interested in what’s in the sea, and those who are interested in what’s under the seabed, and it turned out to be the latter sort who would succeed in establishing oceanography on a modern disciplinary footing. That, of course, meant funding, and in Britain and the United States, government support for ocean science increased markedly during the 1850s in response to the needs of the transatlantic telegraph companies, whose ships were preparing to cast thousands of kilometres of expensive cable into the ocean depths. Their worries concerning the physical conditions of the Atlantic sea floor led to a number of large-scale sounding expeditions being commissioned and paid for at public expense. One result was the discovery of the ‘Telegraph Plateau’, a near-level trough of some 2000 fathoms’ depth running between Valentia in Ireland and St John’s, Newfoundland – a plateau which, according to the author of a hydrographic report submitted in 1854, ‘seems to have been placed there especially for the purpose of holding the wires of the submarine telegraph, and keeping them out of harm’s way’. Others, however, were not convinced, pointing to the ancient but still widely held belief that seawater increased in density the further down one ventured, so that all objects, including heavy cables, found their level long before hitting the bottom. So while it was the case that the suspended cables would not be affected by sea floor irregularities, would they not present a hazard to shipping by snagging on anchors and fishing trawls?
In response to such fears, which were surprisingly prevalent, an energetic PR campaign was launched to persuade shareholders and the general public that the electric cable would indeed lie safely on ‘the down-like softness’ of Telegraph Plateau, where, in the words of a statement issued by the Atlantic Telegraph Company: ‘Nature, indeed, has made every necessary preparation for the work.’ Newspapers such as the New York Herald were also brought on-message, with reassuring photographs of newly-dredged Atlantic sediment carried prominently on their front pages, while the cable’s ‘memoir’, entitled The Story of My Life, was published in London in 1859. The accuracy of the oceanographers’ work was praised, as were the comforts of the ‘oceanic eiderdown quilt’ on which the patriotic cable was soon to lie: ‘Providence has designed that the Old World and the New, severed at first by a great gulf, shall be reconnected by electrical sympathies and bonds, and Providence has prepared the material means for the fulfilment of the design.’
All in all, this was an extraordinary episode, the Atlantic sea floor being an entirely unknown region that no one had come close to seeing, yet marketed by a cartel of scientists and entrepreneurs as a welcoming environment, ‘safe, still and free of dangers’, where it was easy to imagine a cable resting peacefully in its ‘tranquil and undisturbed retreat’. Blatantly unscientific as it was, the campaign did its job, and by the time the Atlantic cable was finally laid in 1866, doubts over its safety had long been dispelled. Leftover sections were sold at Tiffany’s as souvenirs, and grains of sea-floor sediment were set like jewels into watches and rings. Oceanography’s future as a state-funded science was also assured: the Challenger expedition’s 50-volume report was soon established as the discipline’s founding text, along with Twenty Thousand Leagues under the Sea and The Story of My Life, each in its own way an eloquent testament to the 19th century’s awed encounter with the unfathomed reaches of the sea.
The 20th century, by contrast, saw a falling away of public involvement as oceanography became increasingly professionalised, its standing (and funding) no longer dependent on the crowd-pleasing exploits of amateur scientists. As Rozwadowski rather sadly points out, later submarine discoveries, such as the existence of the mid-ocean ridges, were not even reported by the same daily papers that, only a couple of decades before, had published scaled-up photographs of sea-floor sediment on their covers. ‘By the end of the 19th century,’ she writes, ‘the sea floor, and increasingly the intermediate waters, aroused the interest of only a handful of oceanographers.’ The age of enchantment was over, but during its brief heyday – c.1840 to 1880 – ocean science impressed itself on the public mind in ways that would not be matched until the moon landings of the late 1960s, a full century after Nemo’s Nautilus had vanished into the maelstrom.