On motion: a cannonball in fog and an arrow bending in water
Projectile motion through fog and thin air, and an experiment on the arrow's refraction
Under the heading 'On motion', Leonardo argues that a bombard's ball fired through fog travels much less far and strikes with less force than one fired through pure, thin air, though it makes a far greater noise. He then supposes that an arrow shot obliquely into water bends as the 'visual line' does, and lays out an experiment: a fixed crossbow shoots through a paper stretched over water, after which the water is drained and a fine thread checks whether crossbow-rest, hole and arrow lie on one line. The page is entirely text, in mirror script.
On this page
A cannonball fired through fog
The ball of a bombard fired through fog makes much less travel and less impact than one fired through pure, thin air, yet it produces a far greater noise. Leonardo weighs the resistance of the medium against the projectile's range and force.
An arrow refracts in water like a visual ray
Leonardo believes an arrow shot obliquely into water twists as the visual line does, drawing an analogy with the bending of sight. The comparison treats the arrow's deflection as a case of refraction.
Crossbow-and-paper proof over water
To test the idea he fixes the crossbow and shoots into a paper stretched on a frame set above water. Draining the water, he uses a fine thread to see whether the crossbow-rest, the hole in the paper and the arrow align, and from this means to draw a general rule.