For many important meteorological purposes it would be an advantage to be able to keep separate records of the components of the wind in two fixed rectangular directions, the north-southerly and east-westerly directions being those that would naturally be chosen. At present the registering Robinson anemometer records merely the total amount of wind that has passed any spot; a separate pen gives the direction; and a somewhat laborious process of calculation is needed in order to obtain even an approximate estimate of the wind-components. The object of the instrument described below is to resolve the wind into northerly and easterly components and to record their absolute values with two separate pens. The instrument is so arranged that the distance of the one pen from its zero line at any instant will be a measure of the excess of north wind over south wind which has flowed past up to that instant, and the curve traced by that pen will show all the variations of this north-southerly component.