Buys ballot's law
From Glossary of Meteorology
Buys Ballot's law
(Also called baric wind law.) A law describing the relationship of the horizontal wind direction in the atmosphere to the pressure distribution; if one stands with the back to the wind, the pressure to the left is lower than to the right in the Northern Hemisphere.
In the Southern Hemisphere, the relation is reversed. This law was formulated in 1857 by the Dutch meteorologist Buys Ballot and is a qualitative statement of the geostrophic wind relation.