The law of equal angles for incident and reflected rays
Reflection diagrams with a maxim: nature acts by the shortest way
The margins of f. 85v give a rule for constructing the equal angles that flank the meeting of an incident and a reflected ray: b m is the incident ray, m c the reflected ray, and the angle o equals the angle e because a b equals c n. A second note states the principle that every action of nature is performed in the shortest way, and that the rebound is proportional to the force of the impact. Above, curved surfaces shed sheaves of radiating lines—rays striking and rebounding—and columns of untranscribed figures fill the upper left, noted here from the image only.
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Rule for the equal angles of incidence and reflection
A rule for making the equal angles that flank the angle formed by the incident ray, and for drawing the line of the reflected ray. That is, b m is the incident ray and m c is the reflected ray, whence the angle o equals the angle e, because a b equals c n.
Nature acts by the shortest way; rebound follows the blow
Every action done by nature is done in the shortest way. And the rebound will be such as the power of the percussion—the bounce is proportional to the force of the impact. The maxim links the geometry of reflection to the mechanics of a rebounding body.
Sheaves of rays on curved surfaces
The upper diagrams show semicircular and curved surfaces from which bundles of straight lines fan out, representing rays that strike and rebound. They illustrate the reflection studied in the marginal notes but carry no transcribed text of their own. They are noted here from the image only.