Codex on the Flight of Birds

[3] The first page in the folio one contains 11 diagrams with captions for each that relate to gravity, density, balance, and oscillations.

The next page contains four diagrams and a lengthy paragraph on velocity and the differences in movement along the arc and chord of part of a circle.

A short commentary is included on relating density to weight, and he questions why ice floats in water if it is the denser of the two.

Leonardo writes that if a balance was suspended in its center of gravity, then it would not move or oscillate, regardless of position.

[5] The third folio contains 10 drawings and commentary on the following: science of machines, balances, energy, and circular motion.

The diagrams in this folio represent round balances and multiple shaped objects on differing slopes that are connected together.

[6] Folio 4 contains nine diagrams and a page of text on gravity and its effect on different shapes connected together on a balance.

[7] Leonardo writes a lengthy amount of text about two weights that each weigh three pounds that are connected together on either side of a balance.

The first reference to pressure for this codex is made towards the end of this folio, relating it to the working of a balance.

He also questions what part of the wing of a bird experiences the greatest amount of air pressure.

[8] Leonardo starts off folio 5 by stating that if a man were to be in a flying machine, nothing should get in his way from the waist up, so that he can balance himself as one does in a boat.

Leonardo describes how a bird rests in the air, after flapping its wings to gain altitude, by gliding downward to the ground.

[9] Leonardo explains that a bird should fly above the clouds to prevent its wings from getting wet and to avoid the circular air patterns that come from mountainous terrain.

[10] Leonardo starts writing on a flying machine and comparing it with the notes he has already taken on the flight of birds.

He states that "the bird" (machine) must attain a high altitude it case it were to turn over so as to have enough time to right itself.

He notes that the framework needs to be strong with leather laces and raw silk for the ribs.

He states that the action of lowering the tail to be less susceptible to wind in this situation will make it impossible for the "bird" to be overturned.

To prove this, he asks readers to examine bird wings for themselves and to check the larger spacing in between the not as large feathers.