Bird with wings stretched forward
The 'hands' of the wings spend the acquired impetus during the descent
Leonardo studies the bird flying with its wings thrust forward. The 'hands' of the wings turn to face the air near where the bird descends along a straight slope, spending the impetus it has gained. In beating the wings, he adds, the part from the hand backward lifts the bird, while the hand itself drives it forward. A small sketch of a bird with wings extended forward appears at the top of the page.
On this page
The hands of the wings spend the acquired impetus
The hands of the bird's wings show themselves facing forward near the place where it comes down along a straight slope, so as to use up the impetus it has gathered. The outer wing thus acts as a brake at the end of the descent.
Hand drives forward, inner wing lifts
In beating the wings both to hold itself aloft and to advance, Leonardo divides the labor of the wing: the part from the hand backward makes the bird sustain itself on high, while the hand makes it gain ground forward.