1911 Encyclopædia Britannica/Ferrel's Law

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FERREL’S LAW, in physical geography. “If a body moves in any direction on the earth’s surface, there is a deflecting force arising from the earth’s rotation, which deflects it to the right in the northern hemisphere and to the left in the southern hemisphere.” This law applies to every body that is set in motion upon the surface of the rotating earth, but usually the duration of the motion of any body due to a single impulse is so brief, and there are so many frictional disturbances, that it is not easy to observe the results of this deflecting force. The movements of the atmosphere, however, are upon a scale large enough to make this observation easy, and the simplest evidence is obtained from a study of the direction of the air movements in the great wind systems of the globe. (See Meteorology.)