BUYS BALLOT'S LAW

buys ballot's law, in meteorology, the name given to a law which may be expressed as follows:--"stand with your back to the wind; the low-pressure area will be on your left-hand." this rule, the truth of which was first recognized by the american meteorologists j.h. coffin and w. ferrel, is a direct consequence of ferrel's law (_q.v._). it is approximately true in the higher latitudes of the northern hemisphere, and is reversed in the southern hemisphere, but the angle between barometric gradient and wind is not a right angle in low latitudes. the law takes its name from c.h.d. buys ballot, a dutch meteorologist, who published it in the _comptes rendus_, november 1857.