Bombard flame, cracked towers, and painting at a distance
Gunpowder impetus, projectiles in air, structural fissures, and how distance dims a form
A composite of paper fragments carrying notes in several hands and directions. Leonardo argues that the dense flame confined between the resisting walls of a bombard is what gives the ball its impetuous motion, and treats projectiles thrown or shot through air, along with a short philosophical note distinguishing 'nothing' from the 'void'. A pen sketch of a fissured tower reasons about why buildings raised partly on old walls crack, naming the foundation and the uneven setting of mortar as the two causes. A closing note headed 'De pictura' states that true knowledge of a thing's shape is lost as distance shrinks its apparent size; further faint script beyond the transcription is present on the sheet.
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Why the confined flame drives the bombard's ball
The dense flame the powder generates within the resisting walls of the bombard is what produces the impetuous motion of its ball. This impetus cannot be created with a lesser density of flame nor a slower rate of its increase, and such speed cannot arise between weaker walls. Once the flame bursts into the open air it loses density and straightness, ceasing to follow the ball as it dilates.
Does the air behind an arrow drive it forward?
A drawn arrow with six superimposed points poses a question about projectiles rising through air. If the shafts do not divide from one another as they are drawn upward, then the air closing in behind them is not what propels them. It probes whether displaced air can be the mover of a flying dart.
Two causes of cracks in a tower built on old walls
The lettered tower (c e, f n, a, o, m, b, d) asks where fissures will run and where they will be widest. Buildings walled partly upon old masonry always break: the new work c f d set on old a b stays firm at c f while e and d split away. Two causes are named for the ruptures, the foundation and the unequal shrinking of the lime mortar.
Distance and the loss of a form's true shape
The note headed 'De pictura' gives a rule of aerial perception. As much of the true knowledge of a thing's shape is lost as its magnitude is diminished by distance. Recede far enough and the form itself, not only its size, becomes unknowable.