Hygrometers were used to monitor the relative humidity in a weaving mill. In order for certain items to “perform well”, varying degrees of humidity were required.
This instrument consists of two thermometers, referred to by the workers as “dry” and “wet”. The case consists of one fixed and one adjustable ruler, with a table of correspondences expressed in percentages. The humidity level is determined by cross-referencing the readings of the two thermometers.