This "anemometer" helps determine the best weather for flying--it measures the force of air. The idea is simple: when wind blows against the hanging blade, it bends back along calibrations on the curved base. These calibrations signify the amount of force. The weather vane-like pinter on the top of the machine indicates the wind's direction.
In the background, a second style of anemometer measures air force and speed and can also be used to measure water force. When air rushes in through one of the horizontal cones, it spins the flapped wheel, lifting a weight connected to the wheel. The greater the force of air, the higher the weight is lifted. Today's weathermen (meteorologists), air traffic controllers and airport engineers measure wind speed, but with digital anemometers.