Seven-Tenths
Page 18
5
Deeps and the Dark
The wreck of the Florida in Jules Verne’s Twenty Thousand Leagues under the Sea (1870), perfectly illustrating the enduring belief that any object will reach a level beyond which it cannot sink.
I
Why did Dr Ballard, on his journeys to photograph the Titanic, habitually play classical music during the descent and rock music on the way back up? It is unthinkable that it could have been the other way around. The idea of ‘the Deep’ is so powerful that if we listen to the word as we say it a shiver may pass through in recognition of all the associations it has jarred into resonance. By comparison, ‘heaven’ is blank and thin, even faintly unserious. ‘The Deep’ is utterly solemn. Tennyson, whose childhood on the Lincolnshire coast left the recurrence of the sea and its imagery in his poems, knew the word’s exact weight. Stately, funereal, mysterious, it spoke ultimately of loss: a steep dark bulk, time’s liquid correlative which gulps down objects, lives, all that was and will be. Sometimes it is dreamily sinister, as when he layers the ocean horizontally to intensify sheer depth and discern his ageless monster:
Below the thunders of the upper deep;
Far, far beneath in the abysmal sea,
His ancient, dreamless, uninvaded sleep
The Kraken sleepeth …*
Elsewhere, he blurs the outline of a lost friend with the geological implacability of death:
There rolls the deep where grew the tree
O earth, what changes hast thou seen!
There where the long street roars, hath been
The stillness of the central sea.†
Tennyson had read Principles of Geology and must have been struck by the passage where Lyell describes how ‘many flourishing inland towns, and a still greater number of ports, now stand where the sea rolled its waves.’* These two themes – monsters and geology – recur over and over again in the intellectual life of the mid-nineteenth century as the question of ‘the Deep’ was finally tackled by science.
*
Alexander the Great allegedly had himself lowered into the Mediterranean in a glass cage whose door was fastened with rings and chains. He judiciously took food with him, anticipating a long vigil. It was a legendary business, suitable for enhancing the heroic myth, paralleled in the twentieth century by stories such as those told during the Chinese cultural revolution of Mao Tse-Tung strolling for an hour on the bottom of the Yangtse. In Alexander’s case the things he saw were on a properly heroic scale. He observed a monster fish which took three days and three nights to swim past. Such was the insatiability of his scopic drive that, powerless inside his observation chamber, he nonetheless managed to include in his hero’s gaze the subjects of another monarch, uninvited as he was to Neptune’s abyssal kingdom. It was an exclusive as well as excluding view:
None of the men who have been before me, and none of those who shall come after me upon the earth shall see the mountains and the seas, and the darkness, and the light which I have seen …†
The glass cage was all-important. Alexander was not in that humbler but more reliable alternative, a wooden barrel with a glass spyhole. Evidently he felt it important both to see and be seen, to be recognised as Alexander the Great by the creatures of the deep. Maybe this is a characteristic of heroes, for it is also told of him that after death his body was embalmed in honey and, according to his own instructions, exhibited in a glass coffin. This must have afforded an attraction of Leninesque proportions, and it would be interesting to know if he left orders that his eyes remain open beneath the honey the better to survey his awed pilgrims even as they him.
The legend of Alexander’s descent makes plain that the depths of the sea is no place for ordinary mortals. It took a hero to confront it on anything like equal terms. Despite salvage activities, until the late eighteenth century the average European’s mental image of the sea was literally superficial, of a navigable surface above an abyss. It was a treacherous surface, obviously, being liable to spasms of hostility or the unpredictable appearance of awesome creatures from below; but a seafarer needed to know only about winds, waves and currents, and the intentions of other seafarers. Anything deeper was hidden. Yet the work of early hydrographers, the attempts of Scandinavians to correlate the supply of fish with currents, and the demands of geologists to have their theories confirmed made it inevitable that the barrier of the deep sea would be tackled. It was a barrier in more than just the physical sense, however. There was something in the very concept of the abyss which paralysed thought. There seems no other way of explaining the long survival of certain fallacies more akin to superstitions, often promoted by scientists themselves in contradiction of their own laws. Two famous examples show this: the notion of the compressibility of seawater, and the temperature at which seawater reaches its greatest density.
By the end of the eighteenth century scientists knew perfectly well that water, unlike air, can scarcely be compressed at all. Even under great pressure the density of water changes little, certainly not enough to alter its viscosity by much. To the extent that it does change, temperature is a more important factor than pressure. Yet an extraordinary theory survived this knowledge, lasting well into the twentieth century. It held that as pressure increased with depth, seawater grew more and more solid until a point was reached beyond which a sinking object could sink no further. Thus, somewhere in the middle regions of the great abyss, there existed ‘floors’ on which objects gathered according to their weight. Cannon, anchors and barrels of nails would sink lower than wooden ships, which in turn would lie beneath drowned sailors who themselves lay at slightly different levels one from another, depending on their relative stoutness, the clothes they were wearing and, quite possibly, the weight of their sins. This notion was reflected in the old saying ‘Jack will find his own level’. The popular belief was that having reached their level, bodies would forever drift and revolve in timeless suspension. After the Titanic disaster in 1912 it was reported that some of the relatives of drowned passengers had expressed dismay at the prospect of their loved ones wandering through the abyss in submarine limbo.
In the mid-nineteenth century this belief was held even by many scientists. Doubt had been voiced that the transatlantic telegraph cable would ever reach the seabed Lieutenant Maury claimed to have mapped. Might it not sink only so far, to lie conveniently above any ridges and crevasses? (‘This would be to our benefit,’ one nervous shareholder in the original Atlantic Telegraph Company wrote to a friend. ‘Yet surely the conversants’ [sic] voices, subjected to such uncommon compression, may emerge only as mouselike squeakings?’, thereby adding a further misconception of his own. Heady days for speculators, in both senses.) In an otherwise sensible book published in New York in 1844 we find:
Heavy bodies, which will sink rapidly from the surface, do at length apparently cease to descend long before they have reached the bottom; the pressure of the water being such as to cause them to remain at certain depths, varying in proportion to their weights. Thus it is that the plumb line will not act beyond a certain length, and we have no means, of course, of extending our enquiries deeper.*
This passage embodies a strange and interesting idea which reverses conventional heuristic wisdom, namely, that theory can itself make experimentation impossible. At moments like this it becomes legitimate to think about a psychic barrier to exploring the deep. A similar implication, that there are certain things best left undone and certain places it is wiser to leave untrespassed, is no doubt behind the pseudo-scientific reasons periodically advanced for the impossibility of doing them and warnings of the disaster which must befall any attempt to breach the ‘natural’ limits to human activities. It had been predicted at much the same period that speeds above that of a galloping horse would necessarily kill railway passengers. (In the twentieth century, too, ideas were dreamed up to show how any attempt to travel in space would be doomed. Arthur C. Clarke once quoted a man who had written in the 1950s to inform him there was a barri
er separating the outer atmosphere from space proper, an ‘adamantine membrane’ which kept our air in. Anyone having the temerity to force his impudent way through this protection put there for our benefit by A Being Wiser than Ourselves would risk being sucked at infinite speed into outer darkness, followed by all the planet’s air.) The anxiety behind such misgivings has accompanied all technological advance. Why else the notion of the sound ‘barrier’? Those who worry about ‘breaking’ the speed of sound or infringing the depths of space are hardly distinguishable from those who, a century earlier, believed the depths of the sea could never be explored.
Any object or creature floating on the sea’s surface is already supporting with its body the weight of a column of atmosphere tens of miles high, a pressure defined as one atmosphere. To a creature accustomed to sea-level pressures, such as most human beings, this is not noticeable since his body will be in equilibrium with atmospheric pressure. The moment he descends below the waves, however, he will carry the additional weight of a column of water which, being so much denser than air, bears very heavily on his lightly pressurised body. Water pressure increases by an entire atmosphere for every 10 metres of depth. Although the human body is seven-tenths fluid, its pockets of air, its cavities and the materials and construction of many of its components make it far less dense than water. In order to prevent himself being squeezed to death beyond a certain, quite shallow, depth, a human needs to be protected by an outer casing (a diving suit or a submersible) which can resist this external pressure and permit an enclosed environment at his preferred sea-level pressure of one atmosphere. Clearly, the deeper he goes, the stronger this protective cell will need to be. The pressure at the bottom of the Marianas Trench is some 1,170 atmospheres, where each square inch of the seabed, or of a body lying on it, bears a weight of 7.75 tonnes.
The assumption that water itself could be squeezed ‘solider’ by such pressures, as a human body would, no doubt derived from Homo’s habit of seeing the physical world in his own image. This fallacious idea that water could be compressed into an impenetrable layer somewhere ‘below the thunders of the upper deep’ was remarkably tenacious although it never stopped serious attempts to take soundings at ever greater depths. Certain scientists did wonder whether the sounding line might not really be going any lower but simply be piling up in loose coils on this invisible floor like a thread of honey falling on to a plate. Samples of mud brought up were explained as the sediment which had likewise collected there over the course of millennia, presumably building up into a false bottom to the sea. It was the second misconception, however – about the temperature at which seawater reaches its maximum density – that was the more seriously and widely held and had further-reaching effects on early oceanography. It was more baffling, too, since it was blandly assumed – and could very simply have been disproved – that salt water behaves like fresh and is at its densest at 4°C. Strangest of all, the actual temperature had already been established, as Wyville Thomson later pointed out. ‘In 1833 it was ascertained that the temperature of sea water at its maximum density is – 3.67°C, and even before that it was known that sea water can be colder than the freezing point of fresh water and still remain liquid.’*
Unfortunately, the reluctance to accept what had already been scientifically determined was compounded by the inadequacy of the instruments of the day, as Sir James Clark Ross unwittingly showed on his Antarctic expedition of 1839–43. From the decks of HMSS Terror and Erebus (which only two years later were to disappear famously when Sir John Franklin took them to the Arctic to search for the north-west passage), thermometers were lowered on sounding lines deep into the South Polar ocean. When pulled up, those that had not imploded under the pressure read 4°C. What Ross did not know was that in those latitudes the water temperature drops about 1°C every 550 fathoms, a decrease which by sheer mischance happens exactly to compensate for the opposite effect of pressure on an unprotected thermometer. In point of fact his own uncle, Sir John Ross, had already found a temperature of –1.8°C more than twenty years earlier with a thermometer which must have been protected against pressure. This was in 1818, during the expedition to Baffin Bay in HMS Isabella. Sir John not only established this temperature at a depth of 1,050 fathoms but he also brought up a beautiful ‘Medusa’s Head’ starfish (a basket star) from the same depth, something which was conveniently overlooked in the following decades.
The prevailing view of the abyss was now of a vast body of water at a uniform temperature of 4°C, unmoved by either winds or currents. (Had the temperature been allowed by theory to vary between 4°C and –3.67°C, slow convection currents would have been set up.) Without movement, scientists reasoned, there could be no circulation of dissolved oxygen and no renewal of any food particles in suspension. This in turn would ensure the abyss was ‘azoic’, or lifeless, since a stagnant body of water under huge pressure, at barely above freezing point and utterly without light, could not conceivably support life.
The word ‘azoic’ was coined by Edward Forbes, who in the 1840s tried to discover where the boundary lay between the upper part of the ocean which would support life and this great ‘lifeless’ zone. Forbes was a Manx naturalist who in 1842 sailed to the Aegean in HMS Beacon to study the vertical distribution of marine animals. What he found confirmed his theory to his own satisfaction and he came home saying he considered 300 fathoms to be the absolute limit of animal life in the ocean. In fact, as Margaret Deacon has pointed out, such life is particularly sparse at that depth in the Mediterranean.* Forbes also went dredging in the Firth of Forth, taking with him the young Wyville Thomson who for a long time accepted his mentor’s ‘azoic’ theory and thirty years later would write shamefacedly:
We had adopted the current strange misconception with regard to ocean temperature; and it is perhaps scarcely a valid excuse that the fallacy of a universal and constant temperature of 4°C below a certain depth … was at the time accepted and taught by nearly all the leading authorities in Physical Geography.*
If it caused a scientist shame in the 1870s to recall the cant of his youth, it is not easy to know how to treat an episode which took place in the House of Commons nearly a century later. On 12 April 1961 the MP Hector Hughes asked the Civil Lord of the Admiralty, Ian Orr-Ewing, certain questions about recent ‘experimental missions’ beneath the Arctic ice cap by the Royal Navy submarines Finwhale and Amphion. The Civil Lord would give no details, explaining ‘It would not be in the national interest.’ His questioner shifted to the less classified ground of schoolboy physics and the following exchange took place:
Mr Hughes: Can the hon. Gentleman say why the water under the North Pole does not freeze while the water on the surface of the North Pole does freeze? … Is the water under the ice kept warm by the heat generated from the centre of the earth?
Mr Orr-Ewing: In view of the hon. and learned Gentleman’s interest in bathing, I can understand his anxiety about where the ice forms. If he studies the physical tables, he will find that the water is most dense at 4 degrees centigrade and rises to the surface when it reaches 0 degrees centigrade and starts to freeze.†
The ‘azoic’ theory held into the second half of the nineteenth century. When HMS Bulldog resurveyed the transatlantic route for a telegraph cable, soundings were taken down to 2,000 fathoms. When the sounding lines brought up starfish, everyone maintained that the creatures must somehow have become entangled as the lines were being pulled through shallower levels. It was only in 1860 that the theory was finally and unequivocally exploded when a section of telegraph cable was fetched up for repair off the coast of Sardinia. The cable had been laid three years earlier in more than 1,000 fathoms of water (i.e. over a mile deep) and it was found that various marine animals were encrusted on it, their anchoring filaments having worked their way into the outermost layer of insulation. It was quite impossible to argue that they had ‘become entangled’; they had quite evidently grown there. Thus it turned out that the abandoning of the ‘azoic’ theor
y happened neatly to coincide with the publication of Darwin’s theory of evolution.
Practically overnight the almost universal conviction that the deeps were sterile changed to intense speculation that they might actually conceal life forms as well as mineral wealth. As Wyville Thomson was to observe, ‘the land of promise for the naturalist … was the bottom of the deep sea.’ It is perhaps hard now to imagine the ferment which the scientific method was causing in the middle of the nineteenth century. In the 1860s wild speculation became common when the abyss was considered in the new Darwinian light which made necessary a complete revision of prevailing ideas about the planet’s history, about man’s position in the ‘natural’ world and about his relationship to a ‘creator’. Two fields of study, geology in general and the fossil record in particular, had an especial bearing on oceanography. In his Principles of Geology Charles Lyell had avoided tackling head-on the six-day, Genesis version of creation. Instead, he confined himself to pointing out that the Earth’s features could all quite adequately be explained in terms of the simple physical processes which were visibly still shaping it: tension/compression and erosion/sedimentation. This was elegant and satisfactory. The implications might have raised some eyebrows but few hackles since it concerned only the inanimate world of petrology. The real furore was to come a quarter-century later when Darwin made man and the animals also subject to an evolutionary process which led to notions of trial and error, sports and dead ends, casual extinctions, uncomfortable family connections and – worst of all – to the logical conclusion that Homo, far from having been perfected as Nature’s last word, must himself still be evolving. Darwin’s theory also made plain the crucial evolutionary role played by environment. Where conditions were (in geological timescales) fickle and changing rapidly, the species that survived were those which best adapted and evolved to keep pace with them. It was this idea which, coinciding with the demise of the ‘azoic’ theory of the deeps, generated speculation as to what kind of creature might have adapted itself to conditions hitherto considered inimical to life. All the factors which until so recently had indicated sterility – absence of light, intense cold and pressure, no movement – now suggested the one place on Earth in which to look for unmodified ancient creatures, ‘living fossils’. (The terrestrial equivalent was the search for the ‘missing link’, a hypothetical extinct creature midway between the anthropoid apes and man. Storybook quests such as Conan Doyle’s The Lost World grew directly out of the notion that living fossils might yet be found on dry land.)