Sunday, January 29, 2012

William Ferrel

William Ferrel was born on January 29, 1817 in Bedford (what is now Fulton) County, Pennsylvania. His father, Benjamin Ferrel, was a farmer and operated a sawmill. Ferrel was the oldest of eight children, six boys and two girls. In 1829 the family moved to  a farm in Berkeley County, Virginia (now in West Virginia). Ferrel was a shy boy and spent his youth working on his family farm. He got a minimal education in a one room school house for two winters. In 1832, at the age of 18, after observing a eclipse, he used farmer's almanacs and a geography book to compute a list of the dates of future eclipses. Aware of his lack of education he made trips to Martinsburg and Hagerstown in Maryland where he used what money he could make working on neighboring farms to purchase math and science books, solving geometry problems by drawing diagrams on the wooden doors of his father's threshing floor. He educated himself well enough that he could find work as a schoolteacher. He used money he earned teaching to attend Marshall and Bethany Colleges, graduating from Bethany in 1844 in its first graduating class.

After graduation Ferrel moved to Liberty, Missouri where he continued to work as a schoolteacher. In Liberty he purchased a copy of Newton's Principia which had been ordered by a earlier school teacher but never collected, which interested him in the actions of tidal forces. He stopped teaching for a while due to ill health and when he recovered he took another school teaching position in Allensville, Kentucky, where he taught from 1850 to 1854. In 1853, at the age of 36, after studying a translation of Pierre-Simon Laplace's work on celestial mechanics, Ferrel published his first scientific paper, contradicting Laplace and saying that the gravitational effects of the sun and moon on the tides tend to retard the rotation of the earth.  A year later he moved to Nashville, Tennessee, where he set up his own school.

In Nashville Ferrel had a much greater access to scientific books and interaction with other men of science. His interests turned to the subject of meteorology and in 1856 he published an article entitled, "An Essay on the Winds and Currents of the Ocean" in which he described what have come to be known as Ferrel cells, circulating air currents of the middle latitudes that give rise to westerly winds between 30 and 60 degrees of latitude (see here for an interesting video describing Ferrel cells and their place in the three cell model of atmospheric circulation). With this publication he become the founder of the study of geophysical fluid dynamics.

In 1857 he moved to Cambridge, Massachusetts and joined the staff of The American Ephemeris and Nautical Almanac. In 1858 he published another important paper on the effects of the Earth's rotation on bodies in motion at its surface. In the currents of air or water moving horizontally in the northern hemisphere is deflected to the right. In the southern hemisphere it is deflected to the left. This is a description of how air and ocean currents are affected by the Coriolis effect which is caused by the rotation of the Earth. This effect was independently described by Dutch meteorologist Christoph Buys Ballot and is sometimes called the Buys Ballot law. Buys Ballot later acknowledged Ferrel's priority.

In 1867 Ferrel joined the U.S. Coastal and Geodetic Survey and moved to Washington D.C. While there he researched tides and developed a machine that determined tidal maxima and minima. Due to the lack of a capable machinist, it was not constructed until 1883. The machine, once constructed did the work of forty people carrying out hand calculations and remained in service for over 25 years. In 1882 Ferrel joined the U.S. Army Signal Corp. working in what would become the U.S. Weather Bureau. He remained working there for four years, retiring in 1886 at the age of seventy.

Initially he planned to spend his retirement living with his brother Jacob in Kansas City, Missouri, but unable to keep abreast of scientific advancements in 1889 he moved to Martinsburg, West Virginia, where he died on September 18, 1891.


References:

Abbe, Cleveland; "A Biographical Sketch of William Ferrel: 1817-1891" in Biographical Memoirs Vol. 3; National Academy Press; 1895

Davis, William M.; "A Sketch of William Ferrel"; Popular Science Monthly (1892)40:686-695

O'Connor, J.J. and Robertson, E.F.; "Ferrel Biography"; 2002; at www-history.mcs.st-andrews.ac.uk

William Ferrel Wikipedia Entry



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