1685-1768

English natural philosopher who followed up Edmond Halley's (1656-1742) attempt at defining atmospheric circulation by correctly describing the trade wind circulation in relation to the rotation of Earth. A member of the early Royal Society, in 1735 Hadley presented a paper "Concerning the Cause of the General Trade Winds," theorizing from the observed data of trade wind motion. Halley stated that sun-heated air rose over the equator allowing air from the north and south to flow toward the equator, but the easterly orientation of this flow escaped him. Hadley realized that the rotation of Earth from west to east gave northerly or southerly flow an easterly trajectory, since motion from the north or south toward the equator in the reference of a rotating sphere appears slower. This anticipated the theory of Coriolis force, the conception of a force acting to the right on an object on a rotating body, in the next century.