An Ocean of Air

by Gabrielle Walker

  Observers were always welcome at Boyle's experiments, but he was now finding their presence rather awkward. One of his tests with another bird had to be abandoned when the subject was rescued by "some fair lady" who was horrified by the creature's convulsions, and insisted that Boyle immediately let air back in. After this, he did his more controversial experiments at night.

  He began to wonder if his animals were dying because their exhalations somehow clogged up the globe. So he tried leaving a mouse in the closed vessel overnight, with a bed of paper to rest on and some cheese in case it was hungry, and carefully placed the vessel by the fire to make sure it didn't suffer from cold. Next morning, the mouse was not only alive but had eaten almost all of the cheese.

  It was all very baffling. There were plenty of theories at the time for why breathing is necessary, but none of them was really enticing, which is perhaps not surprising, since none of them was right. Boyle himself inclined toward the idea that we breathe to cool down our lungs, which might otherwise become overheated. After all, cold-blooded animals such as fish have no lungs. On the other hand, Boyle correctly suspected that fish might somehow be making use of air dissolved in the water around them.

  It wasn't only animals that needed air. Boyle also discovered that flames flickered out as soon as he drew air out of his globe. In some cases, for glowing coals for instance, readmitting air would rekindle the flame. But if he left the coals for more than four or five minutes, the spark irrevocably died. Boyle couldn't help but notice the similarity between flame and life. "The flame of a lamp," he remarked, "will last almost as little after the exsuction of the air as the life of an animal." Air was clearly vital for both processes, but Boyle had no idea why.

  At least, he remarked, the "spring" that he had discovered made air extremely difficult to remove. Each time his pump operated, the remaining air was more reluctant to quit the globe, which Boyle decided was ultimately a good thing. "This invited us thankfully to reflect upon the wise goodness of the creator who by giving air a spring hath made it very difficult, as men finde it, to exclude a thing so necessary to animals."

  But still, he strove to understand why. And he nearly, so very nearly, came upon the answer. His writings are full of speculations that come tantalizingly close to the mark: "The difficulty we find of keeping flame and fire alive, though but for a little time, without air, makes me sometimes prone to suspect, that there may be dispersed throughout the rest of the atmosphere some odd substance, either of a solar, or astral, or some other exotic, nature," he wrote once. And another time: "I have often suspected that there may be in the air some yet more latent qualities or powers ... due to the ingredients whereof it consists."

  That last comment is extraordinarily prescient. Nobody yet knew that air was a mixture of different gases. Even the notion of individual gases hadn't yet been invented. Air was an element, a pervasive substance that had no parts of its own. This was the mountain of prejudice that had yet to be overcome before the most extraordinary secrets of air would begin to emerge.

  The trouble with Boyle's air pump was it removed everything at once. If the power of air came from its individual ingredients, Boyle was never going to be able to separate them out. His combination of rational mind and vivid imagination had taken him this far, but the next step continually eluded him. In the end, he turned to other things. As his eyesight grew still worse, he studied what little was known of the functions and maladies of the eyes. Ever hopeful, he seized on increasingly bizarre remedies, such as blowing powdered dung into his eyes, or bathing them in honey. Once he had been able to read for ten hours a day, but now he could barely make out the words on a page.

  Boyle's health continued to deteriorate along with his sight, and in 1691, at the age of sixty-five, he died. In his will, Boyle bequeathed his scientific collections to the Royal Society, "praying that they, and all other searchers into physical truths, may cordially refer their attainments to the glory of the great Author of Nature, and to the comfort of mankind."

  Like Galileo and Torricelli before him, Boyle had never married, though he always wore a mysterious ring bearing two small diamonds and an emerald. He left this ring to his beloved sister, Katherine, saying that she would know why. She, however, had died just a week earlier, and the secret died with her.

  The secrets of air, though, did not die. Those three great scientists of the seventeenth century, Galileo, Torricelli, and Boyle, two of them blind and one afraid of the Inquisition, had permanently changed the way we see our world. They had discovered that we live at the bottom of an ocean of air. Now, those who came after were about to discover the ways that same ocean transforms a lump of rock and stone into a living, breathing planet.

  First, the answer that had perpetually eluded the frustrated Boyle. The spirit of air somehow gives life to both animals and flame. But how?

  CHAPTER 2

  ELIXIR OF LIFE

  AUGUST 1, 1774

  BOWOOD HOUSE, WILTSHIRE, HOME OF THE SECOND EARL OF SHELBURNE

  JOSEPH PRIESTLEY PICKED UP his new burning glass carefully by the rim and held it up to the sunlight. It was twelve inches wide, the size of a dinner plate, and looked like a huge magnifying glass without a handle. Ground into its lens shape by a master craftsman, it had cost him the shocking sum of six guineas. But he was convinced it would be worth the money.

  The rest of his apparatus had been in place for some time, and this was the only missing piece. Now, at last, he would be able to focus the sun's light into an intense burning beam that could penetrate the curious arrangement of glass, valves, and mercury-filled troughs that was assembled on the table in front of him.

  Priestley was an unlikely figure to be found in the magnificent surroundings of Lord Shelburne's country seat. He was forty-one years old, of medium height and slim build. His hair was thin and unremarkable, and he rarely bothered with the carefully curled and powdered wigs that were de rigueur for the time. He wore the drab clothes of a clergyman. His features had a slightly pinched look, left over from childhood illnesses, and his eyes were gray. But in spite of his sober appearance, there was something irrepressible about him, and—especially when he was performing one of his experiments—an air of intense excitement. On this afternoon in particular, that excitement was more justified than ever. He was on the point of discovering something that would make him more famous than anything he had ever written, and anything else he would ever do.

  Joseph Priestley was born asking questions. He had been raised in a religious but nonconformist household, and to challenge the accepted order of things was as natural to him as breathing. By the time he was old enough to take holy orders he was already asking too many questions for the religiously hidebound hierarchy of church, state, and aristocracy that controlled England in the eighteenth century. In fact, he had questioned his way into abandoning so many of the basic tenets of the Anglican faith that he was banned from attending university (which was open only to those who could demonstrate a conventional belief in the articles of Anglicanism), and was summarily fired by his first congregation.

  Priestley was no firebrand, though he described himself as a "furious freethinker." His demeanor was pleasant, and his style at the pulpit conversational rather than inflammatory. Above all, Priestley believed in the power of reason. Throughout his life he remained cheerfully convinced that rational argument would prevail.

  It rarely did. The problem was that clergymen were expected to embody the accepted order of things, not try to change it. And in Priestley's case, his attitude frequently got him dismissed. The combination of his scandalous (though gently spoken) views and his exasperating habit of trying to change people's minds meant that he rarely spent more than a few years in one place. He sometimes worked as a clergyman, sometimes as a teacher, other times as a polemicist and prolific writer of pamphlets. By the end of his life, he'd written 150 books and pamphlets and more than one hundred papers, leading some of his contemporaries to grumble that he wrote his words slightl
y faster than his audience could read them.

  Priestley wrote so much partly to counteract a terrible memory. Once, for a pamphlet he was writing, he needed some details about the traditions of the Jewish Passover. Having consulted several writers and condensed the information into a shorthand paragraph, he mislaid the paper in a moment of abstraction. A fortnight later, with no memory of his previous studies, he repeated the whole exercise even down to the shorthand note. With the second note in hand, he then unexpectedly found the first, which he viewed, he says, with "a degree of terror," believing that his mental powers had begun to fail him. But a further effort of memory made him realize that the same thing had happened before, and after that he made it a habit to write down and carefully preserve anything he didn't want to forget.

  To an intellectual such as Priestley, the inability to remember would be a distressing handicap, but it may also have been the source of part of his genius—by helping him to see the world with fresh eyes. He lived constantly in the moment. Unlike other, cooler minds, which needed quiet retreats for concentration, Priestley could work anywhere. In fact his favorite place for writing was beside the fire, surrounded by his cheerful, noisy family, with whom he would stop to exchange comments or pleasantries before continuing with his work.

  Precipitancy was more Priestley's trouble than procrastination, and he was driven in all he did by an overriding curiosity. Already, the structure of grammar, the history of philosophy, theories of jurisprudence and static electricity had been subjects of his intense—and sometimes unsettling—study. "My manner has always been to give my whole attention to a subject till I have satisfied myself with respect to it," he commented. He was also an unabashed enthusiast of learning. A true heir of the Enlightenment, he pictured knowledge spreading like a wave in all directions and believed that it would soon put an end to all usurped authority in the world. He once declared that the English hierarchy "has reason to tremble even at an air pump." This was the sort of proclamation that enchanted his admirers. (One even wrote a poem to laud Priestley's unfettered outspokenness: "Champion of Truth ... eccentric, piercing, bold/ Like his own lightnings, which no chains can hold/ Neglecting caution, and disdaining art/ He seeks no armor for a naked heart.") However, it was also exactly the sort of statement that explained his constant trouble with employers, and which would ultimately bring about his downfall.

  Priestley had no fear of false starts and misconceptions, and detailed all of his mistakes for the benefit of the "adventurers in experimental philosophy" who would follow him. Nor was he afraid of being caught out in his errors. "He who does not foolishly affect to be above the failings of humanity," he once wrote, "will not be mortified when it is proved that he is but a man."

  The latest subject to capture his attention was the hottest new topic in the world of natural philosophers. Nearly one hundred years after the death of Robert Boyle, the science of gases, or "airs" as they were then known, had begun to take off. As well as ordinary "common air"—the stuff that surrounds us and that we breathe—it seemed that there were several other "airs." A "fixed air" that extinguished candles had been discovered to burst out of certain plants and minerals under the right conditions, and there had been recent suggestions of others, including one that exploded when exposed to a naked flame.

  This was exciting news, because for centuries all the focus of natural philosophers had been on the more accessible states of matter—liquids and solids. Gases were so ephemeral and hard to study that until Priestley's time, nobody had noticed there was more than one kind. Still, these were very early days. There were plenty of people now playing with the new gases that bubbled through their glassware, and yet none had yet realized that air itself was made up of more than one component. Any hints that common air might contain traces of separate gases were largely ascribed to impurities. In its purest form, common air was still believed to be a single element, entire and indivisible.

  Priestley's interest in the new airs had begun a few years earlier, while he was living next to a brewery. He had noticed that the "fixed air" (what we now call carbon dioxide) that bubbled out of the vats and hung above them in a choking cloud could be induced to impregnate water, to make a very refreshing beverage. In other words, he had invented soda water. "It was with peculiar satisfaction that I first drank of this water," he said later, "which I believe was the first of its kind that had ever been tasted by man." At first he simply left a vessel of water overnight among the bubbles. Later, he developed a more sophisticated technique involving bellows. He delighted in making the fresh, zingy new drink for his friends and house-guests. He had no idea—and could probably have cared less—that his invention would eventually provide the necessary pizzazz for a billion-dollar global beverage enterprise.

  The problem with more sophisticated experiments with airs was that the equipment they required was expensive, out of the price range of a threadbare vicar and scholar, even one as brilliant as Priestley. However, he had recently obtained a wealthy and sympathetic patron. Priestley was often indignant when he was dismissed or his endeavors were unjustly blocked, but it rarely bothered him for more than a day or so. He sunnily assumed that something else would come along, and it usually did. The latest "something else" had been in the form of William Fitzmaurice Petty, second Earl of Shelburne, a young, handsome, and most important, extremely rich man, with a definite soft spot for revolutionaries. Both men sympathized with the struggles of the American colonists to achieve some measure of independence from their British overlords. Priestley was a good friend of Benjamin Franklin, and his writings would inspire Jeremy Bentham's famous phrase "the greatest happiness for the greatest number," not to mention a certain other phrase that made its way into the Declaration of Independence two years later, involving life, liberty, and the pursuit of happiness.

  Shelburne had decided that Priestley would be an amusing addition to his household, and had invited him to take up the post of librarian for 250 pounds a year. Priestley wasn't particularly impressed by Shelburne and his wealthy, spoiled friends. "I can truly say that I was not at all fascinated with that mode of life," he wrote later. "There is not only most virtue and most happiness, but even most true politeness in the middle classes of life ... On the other hand, the passions of persons in higher life having been less controlled, are more apt to be inflamed; the idea of their rank and superiority to others seldom quits them." Shelburne himself had a very uncertain temper, which, when taken together with the air of privilege that hung around him, meant that even his peers found him difficult. However, Priestley was never overawed, and instead considered that the lack of practice at considering others made members of Shelburne's class objects of pity rather than envy. "On this account," he said, "they are readily entitled to compassion, it being the almost unavoidable consequence of their education and mode of life."

  And in truth, Priestley took full advantage of his time with Shelburne. Though the salary wasn't princely, especially as Priestley by then had a family of four to support, it was adequate. And he didn't have to bother much with stocking the library or performing mundane household tasks. As long as he was on hand now and then to impress Shelburne's guests with his latest ideas, he was free to do whatever experiments he liked. Shelburne even threw in an extra forty pounds a year for equipment, which is how Priestley had finally managed to afford his much-coveted new burning glass.

  This was necessary as part of an elaborate system that Priestley had devised to make and study the new airs. He knew that many solid materials would give off different kinds of air when they were heated. The problem was how to trap the airs without losing them into the surrounding "common air." To get around this, Priestley had invented a clever system involving a series of glass vessels. He would place some substance, in this case a solid red lump of mercurius calcinatus (a calx made by heating mercury in ordinary air), at the bottom of a long glass tube. Then he would fill the tube with mercury. He could then invert the tube and place it in a trough of mercury. Ju
st as in Torricelli's experiment, some of the mercury slipped down the tube into the trough, leaving an empty space at the top, devoid of any kind of air. The only difference in Priestley's case was that now there was a small red lump resting gently on the tightly curved surface of the mercury.

  Now, all Priestley had to do was heat the lump. Then he could collect any air it generated and study it. That's why he had bought the new burning glass. He would at last be able to focus the sun's rays onto the glass vessel to heat his mercurius calcinatus and see what happened.

  He had chosen the mercury calx at random. Priestley's scientific method, like his curiosity, was both all-encompassing and chaotic. He never quite knew what would happen. In one experiment, in which he packed his materials inside a gun barrel and heated them in a fire, the gas he generated emerged so fiercely and rapidly from its prison that the whole gun barrel exploded, shattering the glass equipment that Priestley had put in place to collect its output. Fortunately, he noticed the problem just in time and leapt out of the way. Ever curious, he then repeated the experiment—explosion and all—but with an extra vessel carefully placed to trap some of the gas as it burst out. (It turned out to be what we would now call nitrous oxide, or "laughing gas.")

  This time, however, the experiment proved a little less dangerous. Using the burning glass, Priestley carefully focused a spot of light onto the mercurius calcinatus and waited. Gradually, bubbles of some kind of air made their delicate way through to his collecting vessel. To Priestley's delight, this simple process produced a prodigious amount of gas. But what was it?