A zonally symmetric circulation that appears to be thermally indirect (when viewed using height or pressure as the vertical coordinate) first proposed by William Ferrel in 1856 as the middle of three meridional cells in each hemisphere. A similar type of cell was described by Matthew Maury in 1855 and James Thomson in 1857 at about the same time. The Ferrell cell has sinking motion in the same latitudes as the Hadley cell, but has rising motion in higher latitudes (approximately near 60°). The Ferrel cell is maintained by heat and momentum fluxes due to large-scale eddies and by diabatic processes; these processes are illustrated by the Kuo–Eliassen equation.