Anemometer

Instrument for measuring the velocity of wind, or of currents of air in ventilating systems. For the former, in meteorological observations, the usual apparatus consists of cup-shaped ve els on the ends of arms which turn a central vertical shaft. The anemometer for currents of air in pa ages or ducts consists of a propeller wheel with a num IMG:content-0174.png:[graphic] Robinson's Hemispherical cup Anemometer. IMG:content-0175.jpg:[ocr errors] Register-sheet of an Osler's Anemometer. ber of vanes or blades. The number of turns in any given time is recorded upon a series of dials, as the wheel is turned by the action of the air-current upon the inclined blades. The Wollaston anemometer measures the force of a chimney draft or other flue-current by recording the difference in pre ure inside the flue and in the ordinary air.