Use this instrument for rapid determinations of the wet and dry bulb temperatures, from which the relative humidity can be derived using tables. Two 9" long matching Fahrenheit spirit-filled thermometers, one with a wick attached to the bulb, are mounted in a metal frame with a folding handle and swivel, enabling it to be whirled rapidly by hand. The results obtained with the psychrometer are more accurate than those obtained with a stationary wet and dry bulb hygrometer. The thermometers have a range of 20–120°F with 1° intervals. Instructions and tables are included.