ANEMOMETER

instrument for measuring the pre ure and velocity of the wind. Best known from that of Robinson (1846), consisting of four hemispherical cups rotating horizontally with the wind; combination of wheels records number of revolutions in given time. This superseded by that of W. H. Dines. It consists of a head exposed to wind, and recording apparatus. Head has a vane formed of a tube with open end kept facing wind; underneath, a larger tube perforated with holes arranged in rings. Two tubes separately connected with pipes communicate with recording apparatus. Osler’s pre ure anemometer consists of plate facing wind and forced back on spring, whose resistance measures wind force. Anemometers should be placed on scaffolding some 30 ft. high, and 10 ft. above any building or tree in vicinity. They are used in mines, gas-wells, etc., as well as in meteorology.