Mason Type Hygrometer

For the determination of relative humidity. One thermometer bulb is kept constantly wet by a siphon reservoir while the other gives a dry temperature reading. Humidity is obtained by comparing the two readings on the enclosed chart. Uses a safe and easy-to-read red liquid instead of mercury. Dual scales of -10 to 50°C and 10 to 120°F. Dimensions: 304 x 73 x 32 mm.