Barometer, thermometer and hygrometer combined, 1739.
© Science Museum / Science & Society Picture Library
This combined barometer, thermometer and hygrometer was made by George Graham (1673-1751), the leading clockmaker of his day. Graham has signed the dial of the central hygrometer in this three part table instrument. The measure of humidity by the hygrometer depends on the stretching and shrinking of a piece of weighted whipcord, suspended inside the tapered wooden spindle.