Finding the Bird's Center of Gravity
An instrument for the center of gravity, and how gravity and resistance shift in climb and descent
Leonardo describes a device, sketched at the top of the sheet, for locating the center of gravity of the bird, and argues the study would be worth little without it. He then distinguishes the center of gravity from the center of resistance, showing with lettered figures (a c – b d; e f – h g) how they separate when the bird dives or climbs. A further passage explains that a bird need not keep its wings level like the arms of a balance, and analyzes how compound obliquity of wings and body sets the direction of descent. A red-chalk study of a leaf sits at the center of the page.
On this page
Instrument for locating the center of gravity
A device drawn at the top of the sheet is made to find the center of gravity of the bird. Leonardo notes that without such an instrument the investigation itself would have little value.
Center of gravity versus center of resistance (a c, b d; e f, h g)
When the bird descends, its center of gravity falls outside the center of its resistance, as if gravity lay on line a b and resistance on line c d. When it wishes to rise, the center of gravity stays behind the center of resistance, as marked by f g and e h.
Wings need not be held level; compound obliquity
Unlike the arms of a balance, the bird is not forced to hold its wings at equal height, because its center of gravity is not at the middle of the pivot. If the obliquity is compound, wings inclining south and head and tail east, the bird descends toward the southeast.
Red-chalk study of a leaf
A veined leaf is drawn in red chalk at the center of the sheet, below the writing. It is a natural-form study set among the flight notes.