"This ball inside the circle will be what lets you guide the instrument straight or crooked, as you will. That is when you want to go level, make it so the ball stands in the middle of the circle, and the use of it will teach you."
This instrument was used for controlling the air position of the flying machines devised by Leonardo. For the machine to reach the horizontal position indispensable for certain flight conditions, the small ball in the bell jar must be positioned right in the middle of the inclinometer. The bell glass is for preventing the wind from affecting the ball.
The model is based on the drawing:
- Codex Atlanticus f. 1058 r. (1485)
Milano, Biblioteca Ambrosiana