Go into Trafalgar Square, on a breezy day, without a mackintosh or
umbrella. Then stand under St. Martin's cab-stand when the fountains are
playing. If you get wet through immediately, the wind is due W.; if it
takes a little time to do so, it is N.W., or S.W.; but if you remain
quite dry, it is N., S., or E., which can only be ascertained by
standing respectively at the foot of the column, under the terrace, or
before the club. It hath rarely been known to fail.