Hygrometer consisting of a glass tube that connects a brass dial to a small plate. The plate carries a mobile clamp whose position can be adjusted with a screw. The hygroscopic fiber (not original) is held by the clamp and winds on a pulley that pivots in a box fixed to the back of the dial. A spring, also connected to the pulley, keeps the fiber taut. A pointer indicates the changes in humidity on the dial scale. Made by Nairne & Blunt.