If there was a true intellectual giant among the meteorologists of the nineteenth century, a man who was both able and inclined to devote scientific genius to the problems of the atmosphere, a man who could define the behavior of the air in such a way as to set the science on a whole new plane, a Newton or a Kepler of meteorologists, it was a certain American country boy who learned his physics with a pitchfork while carving geometric diagrams in the soft poplar of a barn. That boy would be William Ferrel. Although great astronomers and physicists had taken up problems of the atmosphere from time to time, adding insight and advancement here and there before turning back to their principal endeavors, Ferrel's was the first really powerful intellect to focus sustained attention on meteorology.
Unfortunately for the science, this Irish American was born into such poverty and such raggedly low rural circumstances that his scientific education came especially slowly and unevenly, and recognition of the importance of his work, when it came at all, arrived especially late. Contemporaries described his "extreme diffidence" and complete indifference to personal position. While these self-effacing characteristics may have endeared him to fellow researchers, they very likely contributed to the obscurity and late blooming of his reputation. So it happened that one of the most important papers in the history of meteorology was written by an unknown Tennessee schoolteacher and was first published in 1856 in the Nashville Journal of Medicine and Surgery.
Ferrel's epoch-making explanation of the general circulation of the atmosphere appeared first as "An Essay on the Winds and the Currents of the Ocean" and then, with more mathematical development, as "The Motions of Fluids and Solids Relative to the Earth's Surface," which was published in 1859 and 1860 as successive chapters in Runkle's Mathematical Weekly. "This alone, had he written nothing else, would have assured his fame in after years, when it would have been discovered," wrote a friend, Professor Frank Waldo of Boston, the author of an early influential text on meteorology. Neither the Nashville journal nor the Mathematical Weekly were likely to circulate among meteorologists, and the influence of these papers was slow to materialize in the United States and in Europe, especially in Britain, during the second half of the nineteenth century. Among men who understood what they were reading, however, Ferrel's essays had an immediate and profound effect. The eminent American meteorologist Cleveland Abbe never forgot the experience. "They gave me at once the strong conviction that a successful attack had at last been made on the complex mechanics of the atmosphere, and that ultimately all would be unraveled," he wrote. "I have often said that that memoir is to meteorology what the 'Principia' was to astronomy." The allusion was less extravagant than it might seem, for Ferrel was a celestial mechanic in the tradition of Pierre-Simon Laplace and Sir Isaac Newton. There was what Abbe called "an intellectual inheritance."
William Ferrel was born "of humble parentage," as he called it, in 1817 in the backcountry of south-central Pennsylvania, the eldest of six boys and two girls. His father, Benjamin, was in the lumber business for a time and had an interest in a sawmill. The rural schools William attended "were of a very inferior order, the teachers mostly being able to teach only reading and writing and a part of the arithmetics," he recalled. "It was thought that I made very rapid progress and I soon had the reputation of being the best scholar in the neighborhood." When William was 12, his father bought a farm in Berkeley County, Virginia, now part of West Virginia. The move there in the spring of 1829 did nothing to improve his educational opportunities. "I was now kept closely at work on the farm, but I went to school here two winters and completed my common-school education," he wrote. "The school-house was an average one of the country at that time—a rude log cabin with oiled white paper instead of glass for window panes." And after school there was nothing but farmwork, "nothing to engage my mind in the way of study and nothing to read" except a weekly newspaper. Somewhere he ran across an advanced arithmetic text, and with the first 50 cents he earned, by harvesting at a nearby farm, he traveled to Martinsburg to purchase the book. In the flickering light of a fire or a tallow candle flame, soon he mastered the work, his intellect fired especially by the brief sketch and few diagrams on geometric measurement.
On the morning of July 29, 1832, while on his way to the field, Ferrel witnessed a solar eclipse. "This excited me and set me to thinking," he wrote. "I had not read or thought anything about astronomical subjects before, but knew somehow that an eclipse of the sun was caused by the moon's passing between it and the earth, and that the lunar eclipses were caused by the moon's passing through the earth's shadow." Working only with a calendar and an elementary geography text, 15-year-old Ferrel set to work to create his own solar ephemeris, accurately describing the times of solar and lunar eclipses. "The amount of study I gave to the subject, both day and night, was very great," he remembered. His work was finally done in 1834. During the next year, he accurately predicted one solar eclipse and two lunar eclipses; on the later occasions, he noted, "the greatest error in the predicted times was only nine minutes."
The farm and the country were poor in those days, and the Ferrel family was big. Most everything William really wanted had to be borrowed or bartered for. In February 1834, he went looking in Martinsburg for a treatise on trigonometry and instead came away with a surveying text, which served his purpose even better. "It happened that during the summer I was engaged a great part of my time on the threshing-floor, which had large doors at both ends, with wide and soft poplar planks," Ferrel wrote. "Upon these I made diagrams, describing circles with the prongs of the pitchfork and drawing lines with one of the prongs and a small piece of board." The diagrams on the doors remained visible for more than a quarter of a century, he said, "and in returning occasionally to the old homestead I always went to take a look at them." In the middle of the winter of 1835-1836, he rode for two days to obtain a copy of Playfair's Geometry in Hagerstown, Maryland. In 1839, with money earned from teaching, he finally enrolled in a small college in Mer-cersburg, Pennsylvania, where he got his first look at algebra. But his money ran out before he could complete his courses of study. It wasn't until July 1844, at the age of 27, with financial help from his father, that he graduated from little Bethany College in Virginia.
Ferrel happened upon a copy of Newton's Principia in a country store in Liberty, Missouri, where he was teaching school. Studying this work, he recalled, "I now became first interested in the tides and conceived the idea that the action of the moon and sun upon the tides must have a tendency to retard the earth's rotation on its axis." Then he obtained a translation of Laplace's five-volume Mecanique Céleste and delved more deeply into this subject. This is what Cleveland Abbe meant by an intellectual inheritance: from Newton through Laplace there was a straight line to William Ferrel's first scientific paper, published at the age of 35 in Gould's Astronomical Journal in 1853. "On the Effect of the Sun and Moon upon the Rotary Motion of the Earth" was the first to point out what mathematicians call a "second order" discrepancy in Laplace's formulation of the frictional effect of the tides on Earth's rotation.
In a bookstore in Nashville, Tennessee, where he was now teaching, Ferrel picked up a copy of Matthew F. Maury's The Physical Geography of the Sea, which he read and found to be scientifically flawed in many important respects. "This first turned my attention to meteorology," Fer-rel recalled. As the eminent Harvard scientist William Morris Davis would later observe, "This almost gives reason to be obliged to Maury for putting his theory in so convincingly impossible a form." Still later writers would remark that turning Ferrel's gaze onto meteorology was Maury's greatest contribution to the subject. Ferrel told a friend, Dr. William K. Bowling, the publisher of the Nashville Journal of Medicine and Surgery, that "I did not agree with Maury in many things," although he declined Bowling's invitation to write a critical review of the book. Ferrel abhorred the kind of controversy that seemed to so animate men like Maury or James P. Espy. Instead, in response to this request, he wrote his first meteorological paper, "An Essay on the Winds and the Currents of the Ocean," a famous work that mentions Maury's views only incidentally.
In Ferrel's hands, for the first time, the deflective force of Earth's rotation finally was given its appropriately fundamental place in shaping the behavior of the global winds and the currents of the ocean. Not since the trade winds researches of Edmond Halley in 1686 and George Hadley in 1735 had the subject of the general circulation of the atmosphere been considered with such care. Ferrel gave the atmosphere both motion and shape—bulging in the middle latitudes, at about 35 degrees, where the force of Earth's rotation deflects to the east its poleward-leaning upper winds and to the west its equatorial trades at the surface. With this work, and the more rigorous treatment of the subject a few years later, Ferrel established himself, along with Laplace, as a founder of geophysical fluid dynamics, a rigorous interdiscipline that is the mother of modern earth sciences.
In the hands of this country boy, the American storm controversy finally came to an end. "In those days it required close study and a very clear insight into the subject and a very independent mind to prevent one from becoming a partisan either of Maury or of Espy or of Redfield, not to mention Dr. Hare, the electrician of Philadelphia, or Dove, the statistician of Berlin," Abbe wrote later. "Precisely such a mind we find in Fer-rel, who, from his surroundings in Nashville, was enabled to look out upon the world of meteorological disputants and to insist upon logic and reason in place of a war of words."
William C. Redfield was nearly right about the rotary motion of winds around hurricanes and most other storms, of course, and Espy was wrong about them blowing in from all sides directly toward a center. Still, he dismissed Redfield's effort to explain the gyration as having to do with "the peculiarities of the aerial currents" and Maury's vacuous suggestion that it "may be owing to the magnetism of the air." Ferrel's model of the general circulation of the atmosphere not only explained the rotary shape of the big storms as a function of the effect of Earth's rotation, it made it absolutely essential. On the other hand, wrote Ferrel, Espy was right about the source of the energy of such storms. Hurricanes, "and all ordinary storms, must begin and gradually increase in violence by the action of some constantly acting force, and when this force subsides, friction brings the atmosphere to a state of rest," he wrote. "This force may be furnished by the condensation of vapor ascending in the upward current in the middle of the hurricane, in accordance with Professor Espy's theory of storms and rains."
In 1857 came an invitation to join the staff of the American Ephe-meris and Nautical Almanac, an annual publication of the U.S. Naval Observatory, in Cambridge, Massachusetts. Ferrel left Nashville a schoolteacher and arrived in New England a man of science. After 25 years at home on the farm, after nearly 15 years of grammar school teaching, Ferrel began the professional career for which in every way he seemed to be intended. At the age of 39, William Ferrel had finally found his calling. More accurately, his calling had found him. He never asked for a job, and many of his important papers were written not from his own impulse but at the urging of friends. Until his retirement in 1886, at the age of 69, he devoted his life to science, to studying the mechanics of the tides and to meteorology and, in a loosely knit pattern, to elaborating his thinking about the planetary motions of the atmosphere and the oceans that he first characterized in 1856.
Ferrel's scientific articles, even the "popular" treatments which contained no equations, were different than others on the subject. As fellow researcher Alexander McAdie put it, Ferrel "built a science, and lifted meteorology from a mass of observations and description, with a few self-appearing general laws, to an exactitude requiring the most refined methods of mathematical discussion." He was a brilliant deductive theorist. Abbe wrote:
Many of our colleague's papers are to be recognized as successful efforts to solve problems that had hitherto been considered beyond our reach.
So completely did he examine his field of study, so accurately did he select the important from the unimportant forces at work in nature, that in every one of the numerous results formulated by him we recognize that a distinct advance has been made from which there will be no need to retreat in future years. In the study of such complex phenomena as the motions of the ocean and air we have to consider the presence of some eight or ten factors, either one of which may become at times of preponderating importance. At some distant epoch man may be able to effect a general solution of equations that shall express the simultaneous influence of all these diverse forces, but at the present time we are not able to even write out the equations, much less to resolve them.
If Ferrel ever took the time to look at a thermometer or a barometer or make any other atmospheric observation himself, the occasion was not recorded anywhere. "He does not seem to have been at all blind to the occurrence of external facts," wrote Davis, "but he appreciated that the proper understanding of meteorology must be based on wider observations than could be made by any one person." For his data he relied on others, such as the meticulous storm studies of Elias Loomis, the global wind observations compiled by James Coffin, and the facts about barometric pressure contained in Maury's Physical Geography of the Sea.
Ferrel was not a great mathematician, but he was, like Newton, good enough. Davis called Ferrel's ideas in meteorology "wonderfully original" and far more important than his mathematical treatment of them. "It is perhaps because of too great attention to mathematical form and relative neglect of the idea that it clothes that the English mathematicians and meteorologists as a whole have been so little affected by Ferrel's suggestions," Davis wrote in 1891. "His principles as yet have not really touched meteorological science in that conservative country."
The situation in British meteorology in those years was ironic at the least, if not scandalous. Old men of dimming vision were in charge of the scientific societies. To borrow a phrase from one historian, there were dead hands at the tiller. At a time when the English mathematicians and scientists were so sententiously berating the applied, empirical work of the pioneering forecaster Robert FitzRoy, they were themselves cultivating a fairly thorough ignorance of some of the nineteenth-century's most important theoretical work in meteorology. For years, British meteorologists were repeating old theories long after they had been abundantly disproved.
Ferrel himself seemed largely indifferent to these matters. "In Ferrel's everyday life there seemed to all who knew him to be a certain amount of isolation too large to satisfy us, and he himself felt this," Abbe wrote of his old friend. "Preoccupied by problems, and therefore necessarily alone with his own thoughts, he had, even from boyhood, neglected the development of the social side of his nature." He never married, never lost that painful shyness, passing his days living with friends in what Abbe described as "a systematic regularity from which he knew that he must not depart if he were to master the problems of the ocean and the air." A few minutes of parlor conversation with people he knew well was all the social interaction that he required, and all that he really seemed comfortable with. "Of the leading traits of my character a prominent one all through my life has been a great diffidence and a backwardness in coming in contact with strangers or in putting myself forward in any manner," Ferrel wrote. This trait was to cause him trouble even at the height of his scientific powers. He described how on at least one occasion he could not bring himself to stand before a sympathetic assemblage of the American Academy of Sciences in Boston and read a paper, "Note on the Influence of the Tides in Causing an Apparent Acceleration of the Moon's Mean Motion." He wrote, "Although the paper contained an original and important suggestion and I had it all written out, yet I carried it to the meetings of the Academy time after time with the intention of reading it, and my courage failed, and if I had deferred it one time more I would not have anticipated [Charles] Delaunay on the same subject."
In 1867 came an offer of a job at the Coast and Geodetic Survey, which was interested in his insights into tidal observations. At the survey, he developed a tide-predicting machine. Beginning in 1884, this elaborate device was used for years by the agency to compute tides mechanically.
In 1882, while still overseeing the construction of his tide machine at the Coast and Geodetic Survey, Ferrel accepted an invitation to work as a professor of meteorology at the new U.S. Army Signal Service Office, where his longtime friend Cleveland Abbe had been in charge of weather forecasting for the nation since 1871.
For 30 years Ferrel conducted his highly original and valuable research, producing 3,000 pages of studies that other investigators would pour over for many years. For all that, he ended his own brief description of his career by expressing a sense of lost opportunity in his life. "Much of my time has been wasted," he wrote, "especially the earlier part of it, because not having scientific books and scientific associations I often had nothing on hand in which I was specially interested."
William Ferrel died on September 18, 1891, in Maywood, Kansas, in the company of his brothers and sisters. In the following months, in all of the important societies in the country, men of science gathered to pay their respects.
"Here was a man known by name to hardly more than a few hundred of our millions; known personally to fewer still in a vast population that is ever ready to recognize notoriety; and yet his quiet work greatly advanced the bounds of human knowledge," wrote Davis. "It is a curious commentary on renown to name Ferrel, of whom the great world knows nothing, as the most eminent meteorologist and one of the most eminent scientific men that America has produced."
Cleveland Abbe, who knew Ferrel longer and better than probably anyone, never lost the feeling that he was in the presence of someone who was in some important way intellectually different from other men. "We all remember his quiet ways, his indefatigable industry, his shyness, his perpetual absorption in the contemplation of some new and complex problem," he wrote. "He lived in an atmosphere of abstraction; he was with us, yet not of us."
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