Born Bedford (Fulton) County, Pennsylvania, USA, 29 January 1817
William Ferrel was a self-taught American meteorologist and geophysicist best known for his maxima and minima tide-predicting machine, for Ferrel’s law, and as the father of geophysical fluid dynamics. He was the son of Benjamin Ferrel, a farmer and sawmill operator; his mother’s maiden name was Miller. In 1829, the family relocated from Pennsylvania to a farm in Berkeley County, Virginia (today Martinsburg, West Virginia). William attended public schools and worked on the family farm. His curiosity about the scientific world around him made him a passionate reader on mathematics, surveying, and mathematical physics. With money saved from teaching, he attended Marshall College in Mercersburg, Pennsylvania, beginning in 1839, and later transferred to the new Bethany College, Bethany, Virginia. Following graduation from Bethany in 1844, Ferrel continued teaching, first at Liberty, Missouri (1844–1850), then at Allenville, Kentucky (1850–1854), and finally in Nashville, Tennessee, until 1857, where he opened his own school.
Ferrel taught himself mathematics, including algebra, geometry, and trigonometry. He pursued his mathematical studies according to the availability of books rather than by following the traditional route, and he learned land surveying from a professional who lived in the area. Ferrel’s early years of educational deprivation, and his later years of intellectual isolation, left his mind open to original methods of thought. His interest in astronomy, which began in the early 1830s, prompted him to ponder mathematical complexities, such as the prediction of eclipses. The essays of George Airy , including his “Figure of the Earth” and “Tides and Waves,” influenced Ferrel’s study of the oceans and the atmosphere.
While in Liberty, Ferrel found for sale a copy of Isaac Newton ’s Principia, which he studied in detail. Newton’s explanation of tides particularly intrigued him, and following extensive study, Ferrel correctly concluded that the motion of the tides influenced the speed at which the Earth rotated. Ferrel also studied Nathaniel Bowditch ’s translation of the classic work Mécanique céleste by Pierre de Laplace . He was further influenced by physicist Jean Foucault ’s studies of the Earth’s rotation using his pendulum and gyroscope, and by Matthew Maury ’s publication Physical Geography of the Sea (1855).
… that if a body is moving in any direction, there is a force arising from the Earth’s rotation, which always deflects it to the right in the northern hemisphere, and to the left in the southern.
This was an independent statement of what is now called the Coriolis effect. He later showed how this law could explain storms, wind patterns, and ocean currents.
Ferrel’s advancements in science earned him a position in the US Navy’s Nautical Almanac Office in Cambridge, Massachusetts. This appointment placed him in proximity to libraries, and in an intellectually stimulating environment among mathematicians and astronomers, such as Benjamin Peirce , Gould, Asaph Hall , and Simon Newcomb . When Pierce became superintendent of the United States Coast Survey in 1867, Ferrel followed him to Washington.
In 1876, about the same time that William Thomson (Lord Kelvin) developed a tide-predicting machine, Ferrel independently built a tide machine of a somewhat different, more compact and refined design, which predicted minimum and maximum tides. Ferrel’s tide-predicting machine was put into service in 1883 and was unrivaled for the next 25 years. The chief of the Tidal Division of the Coast and Geodetic Survey stated that Ferrel’s tide machine performed the labor of 40 (human) computers.
Ferrel’s continuing interest in astronomy led him to use tidal data to calculate the mass of the Moon. The publication from 1877 to 1882 of his three-volume Meteorological Researches led to Ferrel’s employment from 1882 to 1886 as a meteorologist with the United States Army Signal Service, which was responsible for the nation’s weather service prior to the creation of the Weather Bureau in 1891. American meteorologist Cleveland Abbe credited Ferrel’s 1859/1860 memoir in the Mathematical Monthly on the mechanics of the atmosphere as being “… to meteorology what the Principia was to astronomy ….”
Ferrel retired to Kansas in 1887 to live with his family, and died there. He never married.