The bow's motive power: great at the start, ending in nothing
A drawn bow and arrow illustrating the pyramidal decline of an impelling force
A bent bow with its string drawn and an arrow nocked is sketched at the head of the page, above a passage on the 'motor' whose force is spent while the cord is still pulled. Leonardo argues this movement has the same power as the taut cord as the arrow leaves the crossbow, its force being 'pyramidal' — great at the beginning and fading to nothing. The arrow's motion likewise begins great and ends in nothing. The passage breaks off mid-sentence and continues on the following folios; a small circle marked with dots below stands for the spherical mobile body of the mechanics.
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Pyramidal decline of the motor's force
Leonardo considers a motor whose course is finished while the cord is still drawn, and calls its power 'pyramidal' — great at the beginning and finishing in nothing. He says this movement has the same power as the cord that stays taut as the arrow leaves the crossbow. The arrow's own motion also begins great and ends in nothing, keeping the length of its power of motion.
Drawn bow charged with an arrow
At the top of the sheet is a pen sketch of a bent bow with its string drawn and an arrow set at the centre. The weapon is used here as a demonstration of impelling force rather than as an object of war, standing for the 'crossbow' whose cord and arrow the text discusses.