“For measuring how fast you go per hour with the course of a wind.”
This instrument is used for measuring the amount of moisture in the air. The model is constituted of a wooden supporting structure upon which a graduated quadrant of circular form is hung. On the quadrant hinges a bar, at the extremities of which a sponge and a block of wax are attached. To the sides of the bar rotating on the quadrant there are two materials: one is impermeable (the wax), while the other is hygroscopic (absorbent: the sponge or cotton) and weighs more in accordance as the air is more humid, causing the bar to move along the graduated quadrant.
The model is based on the drawing:
- Codex Atlanticus f. 675 r. (1487)
Milano, Biblioteca Ambrosiana