Doubled Motion of the Arm in Throwing a Stone
With the sling, and a question on why short bombards report louder than long ones
Under the heading On motion, Leonardo analyses how the arm hurls a stone, arguing the motion is doubled: the elbow drives forward while the fist swings back in a circle, then forward, releasing the stone with a sudden check that rebounds like a percussion in the air and adds greatly to the throw. He shows the path as a b c and notes the sling (fromba) casts by the same motion with the added swing of its cord. A closing note, On percussion, asks why a short bombard makes a louder report than a long one. Small pen diagrams of the arm and an oval sling appear in the right margin, with faint red-chalk construction lines crossing the lower text.
On this page
The doubled motion of the throwing arm (a b c)
Leonardo argues that the arm's motion in hurling a stone is doubled: as the elbow goes forward, the fist with the stone swings back again in a circular path, then forward, releasing the stone with a sudden check of the arm. That abrupt arrest, by its suddenness, rebounds backward and acts in the manner of a percussion in the air, so the throw carries far more force than a single continuous swing. The path is marked a b c.
The sling continues the same doubled motion
Likewise the sling (fromba) is fastened to the arm and casts its stone by this same nature of motion, with the added circular or folded-back swing that the cord makes before it releases the stone.
Why a short bombard reports louder than a long one
Under the heading On percussion, Leonardo poses a question: why does the short bombard, when firing, make a greater report than the long one, as is heard in the firing of the tails of the passavolanti?