Profile heads, a balancing nude, and the impetus of a bombard
Figure studies over notes on projectile impetus and the proportion of circles to their diameters
The sheet is dominated by faint metalpoint figure drawings: a finished male profile head with curling hair at the centre, a second profile face at the far left, and a nude striding while balancing a long pole. The transcribed passages, however, concern other matters. One argues that when the powder ignites in a bombard the impetus grows as the ball's resistance falls, right to the mouth of the barrel, and then always diminishes, just as a crossbow's cord is strongest at the start of its release. Another works the proportion of circle to circle as the squares of their diameters, running the arithmetic with a million and its square. Additional writing fills the right folio and is not transcribed here.
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A male profile head and a nude balancing a pole
At the centre a carefully modelled male profile with curling hair is drawn in metalpoint, with a second profile face at the far left. Toward the upper left a nude figure strides while balancing a long pole, its weight carried across the shoulders.
How the impetus of a bombard's ball grows then wanes
When the powder first moves in the bombard little is kindled, so the greater force meets the ball with ever less resistance; the impetus grows successively up to the mouth of the barrel and always diminishes thereafter. Likewise the crossbow's cord is most powerful at the start of the motion, not when the arrow leaves it.
Circle-to-circle proportion as the squares of diameters
The proportion from circle to circle equals that of the square to the square built on their diameters. Leonardo runs the arithmetic with a unit and a million, taking one square as a unit and the other as four million, so that four million times four million yields sixteen million, then halves the diameter of the greater circle.