The wind pattern in the North Atlantic (Fig. 1) is more or less clockwise, and therefore the easiest way to cross the Atlantic from east to west is by the southern route, and from west to east along the northern route. In between, in the middle of this rotary system, are the horse latitudes where winds tend to be light and variable. Superimposed on this wind system, of course, is a series of depressions which commonly move from west to east across the North Atlantic, each depression having its own system of winds rotating anti-clockwise: on the south side of the depression winds tend to be westerly whilst on the north side they tend to be easterly.