Ferrel, William (1817-1891)

US meteorologist. He was the first to describe mathematically the significance of the earth's rotation on its surface bodies. As a member of the Signal Service, he invented a tide machine, the first to predict maximum and minimum tides.

He was born in Fulton County, Pennsylvania. Largely self-taught, he is credited with moving meteorology from a descriptive science to a quantitative science. Ferrel's Law states 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 hemisphere’. He joined the American Ephemeris and Nautical Almanac in Cambridge, Massachusetts and he worked on the US Coast and Geodetic Survey. His publications include Popular Essays on Movement of the Atmosphere (1882).