Humidity measurement, 1688.
© Science Museum / Science & Society Picture Library
Plate from 'Traittez des Barometres, Thermometres et Notiometres ou Hygrometres' (1688) by J D'Alence. This diagram shows how dampnes is indicated by changes in the length of a stretched cord. The book is a pocket-sized treatment of the barometer, thermometer and hygrometer, with 35 plates showing natural philosophers at work and the variety of instruments used, which are shown as installed. The thermometer was developed in the early 1600s and the barometer in about 1640.