Codex on the Flight of Birds

Codex on the Flight of Birds is a relatively short codex of circa 1505 by Leonardo da Vinci. It comprises 18 and measures 21 × 15 centimetres. Now held at the Biblioteca Reale in Turin, Italy, the codex begins with an examination of the flight behavior of birds and proposes mechanisms for flight by machines. Leonardo constructed a number of these machines, and attempted to launch them from a hill near Florence. However, his efforts failed.

In the codex, Leonardo notes for the first time that the center of gravity of a flying bird does not coincide with its center of pressure.

The following summaries are from the codex whose English translation was prepared by Culturando and Smithsonian Institution.

The front page is titled "On Casting Medals". The first paragraph gives a brief recipe that consists of "emery", "nitric acid", "iron filings", "vinegar", "ashes of walnut leaves", and "finely ground straw ash". The second paragraph tells of the process of crushing diamonds into diamond powder and separating the powder from lead. The last paragraph explains how to crush large crystals into smaller crystals, and how to grind, purify, and color enamel.

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.

Leonardo comments on how gravity, which is caused by the "attraction of one object to another", takes place when an object is placed above another object and the top object is heavier than the bottom object. He also writes on the workings of a balance by describing how "the vertical center of a balance must always be perpendicular" and how the length of the arm on the balance is proportional to the amount of oscillations and the oscillation angle. 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.

In the last page of this folio, Leonardo explains why an object falling down the arc of a curve will fall faster than if the object falls down the chord of a curve. He explains this saying that the angle of the chord is half of the angle the curve makes between the midpoint, endpoint, and horizontal, and since this angle is half then the speed will also be half. He compares this with the angle the arc makes with the endpoint, midpoint, and horizontal. An object falling down an arc is then said to be 7/8 faster than if it were to fall down the chord of a curve.

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