An Ocean of Air (16 page)

Then he saw a copy of a book that he immediately coveted. It was called
Parks Arithmetic,
and it contained enticing diagrams for how to calculate the circumferences of shapes and their sizes, too. He wanted it desperately.

Still, Ferrel was too shy to ask his father for the money—for a book, of all things. Instead, he waited until he managed to earn fifty cents by helping at a neighbor's farm during harvest, and then headed off to the book shop in Martinsburg. The book, it turned out, cost sixty-two cents, but the kindly storekeeper let him have it anyway.

Parks Arithmetic
was the unlikely beginning of Ferrel's lifelong love affair with books. He devoured the text, working eagerly through its problems and delighting at each answer that he found. Arithmetic came easily to Ferrel. It was theoretical, even perhaps imaginary, and held no apparent connection to the natural world that he lived and breathed on the farm. But he loved it the way crossword addicts love their puzzles. Give him the problem, and he would find the solution.

Then, on the morning of July 29, 1832, something important happened to connect this solving of puzzles to the world around him. Ferrel was on his way to the fields when he saw an eclipse of the sun. He hadn't expected it, but he realized that somebody must have known it was coming. The moon was perpetually floating over his head, and once in a while it must get between Earth and the sun and briefly block the view. A lunar eclipse had to be the same sort of thing, except that the moon's view of
the sun was being blotted out by our shadow. In each case, the cosmic do-si-do of the planets had to be predictable.

Of course, Ferrel had never studied astronomy. He didn't know the shape of the moon's orbit, and in any case hadn't learned enough geometry to be able to calculate its path. But he could look for patterns. If he worked hard enough, with the only tools he could find—an elementary geography book containing information about the globe, and a farmers' almanac predicting the positions of the sun and moon at different times of the year—perhaps he could work out the times and dates of future eclipses.

This was a fabulous new puzzle, one that appealed to his practical streak as well as to the theoretician in him. He worked every moment that he could spare from his chores, day and night, carefully inscribing his efforts in a notebook. (At one point, he almost gave up in despair. He had wrongly assumed that Earth's shadow would always be the same diameter as Earth itself, whereas in fact it gets steadily smaller as you move farther away. With this error in place, his geometry simply wouldn't make sense. Then, one evening on the threshing floor, he noticed that a shadow cast by a wooden plank was thinner than the plank itself, and he raced back to redo his calculations.)

After two years of hard labor, Ferrel finally had his predictions: The following year, 1835, would have one solar eclipse and two lunar ones. He had no need to wait for the specified dates and times to find out if he were right—the calendar for 1835 would have the answers. And when it arrived, Ferrel was triumphant. The three eclipses were due exactly as he'd predicted, and his times were accurate to within a few minutes.

Now Ferrel was hooked. A neighboring youth told him about a book he had seen that contained "a great many diagrams" and was on a subject called trigonometry. Back at the Martinsburg book shop, Ferrel bought the nearest thing he could find—a surveying text—and began studying it avidly.

He had hardly any spare time that summer—he was supposed to be working all the hours of daylight on the threshing floor, separating wheat from its chaff. Luckily the building had large doors at either end, made of wide planks of soft poplar wood. With this at hand, Ferrel had no need of
a blackboard or of paper and pen. He drew his diagrams on the doors, making circles with the prongs of a pitchfork and straight lines with a single prong, using a small piece of board as a ruler. (The lines he had carved survived wind and weather for several decades, and even after he had become an exalted scientist, each time he returned to visit the farm he went to look at them.)

That winter, Ferrel borrowed another geometry text from an old surveyor who lived in the mountains and studied it by the feeble light of a tallow candle, or more often by firelight. He had a stock of light wood, and each log that he threw in would encourage the fire to flare up, though only for a few minutes at a time. The next winter, he rode for two days through the snow to buy a copy of
Playfair's Geometry
from Hagerstown in Maryland. The more he learned, the hungrier he became.

Ferrel wasn't simply studying to know what others had already figured out. He now felt an urge to discover things, to explain the Earth in ways that hadn't been explained before. Thanks to his work on the eclipses, his favorite puzzles had become the ones that truly existed, in the real world that he sensed around him.

With money made from teaching, and some donated by his bemused but supportive father, Ferrel attended college, where he studied algebra, geometry, and trigonometry. (Finding this didn't fully occupy his intellectual energy, he also picked up Latin and Greek grammar on the side.) In 1844, after a hiatus to earn more money for fees, Ferrel finally graduated, age twenty-seven. He had gone from farmer to mathematician, but there were still few academic options for a poor boy from West Virginia. He returned to his day job of teaching, and devoted his evenings and all his spare time to research. Always, he was seeking the next subject that would fire his imagination with the fervor he could scarcely control.

A decade passed, Ferrel working at this and that in between his teaching. And then, in 1855, at the age of thirty-eight, he came across a book called
The Physical Geography of the Sea,
by Lieutenant Matthew Fontaine Maury of the U.S. Navy. The book was a curious one. It contained tables and tables of data on winds, currents, and air pressures collected from around the world. But it was also full of what seemed to be odd theories
about how these numbers connected. Ferrel bought the book and took it home for closer study.

Ferrel didn't know it, but Maury was already famous, or more accurately infamous, in the nation's capital. He was an ambitious, bombastic military man with apparently limitless energy to promote himself. He had made his name through the undoubtedly excellent idea of collecting logbooks from ocean-going vessels, tracing their routes and collating their wind records so that he could publish maps of the prevailing winds. The resulting
Charts of Winds and Currents
had been an immediate hit. Unfortunately, it had also fed Maury's already considerable ego into believing that he was a great scientist. He was convinced he was now qualified to speak with scientific authority on every imaginable subject. And when, in spite of having no background whatsoever in astronomy, he managed to get himself appointed superintendent of the U.S. Naval Observatory in 1844, he became insufferable.

Although he wasn't an easy man to like, you could feel sorry for Maury. He wanted nothing more than to be one of the scientific gang. But his problem was that he simply wasn't very good at science. His theories were wild. He invoked random magnetic forces to explain phenomena that he couldn't begin to understand, and when that failed, he resorted to thundering passages from the Old Testament to justify his "scientific" claims.

Others in Ferrel's day were either scornful of or downright alarmed by Maury, especially when he began claiming to be an expert in meteorology and urging Congress to accept him as head of a new, and highly dubious, system for predicting America's weather. By 1856, the burgeoning scientific community had already begun openly referring to him as a "humbug." Maury was just as insulting in his ripostes. When he was criticized at a scientific meeting at the Smithsonian Institution in Washington, he responded by declaring that John Smithson, the institution's otherwise illustrious founder, had been born a bastard (a fact that everybody knew but nobody ever mentioned). The city's principal newspaper, the
Washington Star,
then took up the cudgels, describing Maury's work as "one of the most remarkable and successful careers of unblushing charlatanism known in the world's history."

Ferrel was sublimely unaware of all this Washington name-calling and wouldn't have paid attention to it anyway. But he was intrigued by what he read in Maury's book
The Physical Geography of the Sea.
In this book, Maury had set out much of the data that he had collected from records of wind currents and pressures. But, in a bid to seem more scientific, he had also filled the book with his bizarre theories of how the winds work. What Ferrel read set the circles turning in his head. Somehow there had to be a way to make the connection between all the disparate winds that Maury was describing, one that Maury himself clearly hadn't found. It seemed a shame to waste such valuable data on such feeble ideas. What's more, Ferrel was sure the answer would involve his favorite subject—geometry.

He decided to take the book to one of his best friends in Nashville, a medic from the college named Dr. William Bowling. Ferrel had no family here in the city, and not many friends. He was far too shy to socialize with strangers, but the few people who had managed to break down his barriers had become very close to him. Bowling was one of these, and he especially loved talking to Ferrel about science. He was the publisher of the
Nashville Journal of Medicine and Surgery,
and had been trying for years to give this journal some intellectual clout of the sort that Ferrel always seemed to carry with him. Ferrel explained his interest in Maury's data and his disquiet about the conclusions in the book. When Bowling heard this he was gleeful. Write me a review for the journal, he demanded. "Pitch into him."

But gentle William Ferrel had no intention of pitching into anyone. He decided instead to use Maury's data to come up with his own ideas of how the winds work.

This had two odd consequences. By accidentally turning Ferrel's gaze onto meteorology, Maury's contribution to the subject would indeed turn out to be seminal—though not in the way he had hoped. And one of the most important papers ever written in the history of the subject was about to be published in an obscure Nashville medical journal.

Ferrel decided to ignore Maury's theories completely and look for the facts that he had gleaned from shipboard measurements and reports. It seemed that the winds in the two hemispheres moved in mirror image. On each side of the equator were the steady trade winds, which blew consistently from the east. Beyond these was another pair of wind belts, which were much stormier than the trades and usually blew from the west. Between these two sets of winds lay a mighty mountain range made not of rock, but of air. According to Maury's data, for some reason, air piled up in two giant ridges of high pressure, which circled the entire planet north and south of the equator, and separated the trades from the westerlies. This was the puzzle that Ferrel determined to solve: What drove these giant belts of wind to form, and why did the air pile up in between them?

Ferrel began by considering how moving air would be affected by passing over a surface (the planet beneath) that was itself moving. He picked up his pencil and began his calculations.

The math was fiendishly complicated, but the answer surprised Ferrel with its sheer simplicity. In response to the turning Earth below, air itself felt the urge to turn, and always in a certain direction. Put plainly, "in whatever direction a body moves on the Earth's surface there is a force arising from the Earth's rotation which deflects it towards the right in the northern hemisphere, but the contrary in the southern."

Air descends at the tropics to create two "mountain ranges" of high pressure.
Equatorwards of this, air moves to the west, while polewards it moves to the east.

In other words, Ferrel had discovered the precise nature of the giddying effect that our planet's spin has on the air above it. Unscrupulous locals crouching over buckets at the equator might have tried to con money from you by convincing you that water goes down plugholes counterclockwise in the north and clockwise in the south because of it. This isn't true—in something as small as a bucket, any tiny perturbation in the water will be big enough to swamp the effect. But on a larger scale, the effect of the planet's spin certainly does make storms circle in opposite directions in the different hemispheres. Chances are you think of this as the "Coriolis effect."

Nobody really understands why the effect was called this. About 1930, forty years after Ferrel's death, textbooks began inexplicably to refer to it this way, after French mathematician Gustave Gaspard Coriolis, who in 1836 had published a set of equations explaining how objects behaved in theoretical rotating systems. His math was flawless. But Coriolis had never applied his research to the atmosphere, nor even imagined using it to explain the winds.

Even in Ferrel's time, meteorologists called the "north hemisphere turns right, southern hemisphere turns left" rule after someone else. A year after Ferrel came up with his rule, Dutch scientist Christophe Buys Ballot from the Royal Netherlands Meteorological Institute published a paper simply pointing out the observation that northern air tends to move right. He had made no attempt to derive it mathematically, nor did he take it any further. However, because nobody had heard of William Ferrel, researchers began calling this "Buys Ballot's Law," and the name stuck.