William Ferrel

Meteorologist, born in Fulton Co, Pennsylvania, USA. Largely self-taught, he is credited with moving meteorology from a descriptive science to a quantitative science. He was the first to describe mathematically the significance of the earth's rotation on its surface bodies. Known as Ferrel's Law, it states ‘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 hemisphere’. He was a school teacher in the midwest before joining the American Ephemeris and Nautical Almanac in Cambridge, MA (1857). During 1867–82 he worked on the US Coast and Geodetic Survey. As a member of the Signal Service (1882–6), he invented a tide machine, the first to predict maximum and minimum tides. His publications include Popular Essays on Movement of the Atmosphere (1882).

William Ferrel (1817 – 1891), an American meteorologist, developed theories which explained the mid-latitude atmospheric circulation cell in detail, and it is after him that the Ferrel cell is named.

Ferrel demonstrated that it is the tendency of rising warm air, as it rotates due to the Coriolis effect, to pull in air from more southerly, warmer regions and transport it poleward.