Cupid measuring humidity, 1688.
© Science Museum / Science & Society Picture Library
Plate from 'Traittez des Barometres, Thermometres et Notiometres ou Hygrometres' (1688) by J D'Alence. Cupid is sitting on a cloud, measuring humidity by weighing a damp sponge. The book is a pocket-sized treatise on the barometer, thermometer and hygrometer, with 35 plates showing natural philosophers at work and the variety of instruments used by them. The plates are particularly early illustrations of natural philosophers at work.