Hygrometer, Wet & Dry Bulb, Mason’s
Comprising two thermometers tubes with double scale graduation, mounted on a weather-proof case with shade. Scales graduated -10 to 50 × 1°C and 20 to 120 × 2°F. One thermometer kept dry and other has bulb covered with muslin or wick, dipped into a water reservoir, which keeps it wet during long periods of non-use. Comparing the reading of wet and dry thermometer from the humidity and temperature conversion chart included, relative humidity can be worked out. Mounted on wooden base.