Weights on Pivoted Wheels; Stairs of the Count of Urbino
Free weights seek the center of the world, with sketches of rustic staircases
A heading names the 'rustic stairs of the Count of Urbino' beside sketches of steep, ladder-like staircases. The main demonstration treats weights carried on a pivoted wheel (a - b), a pivoted half-wheel (n - c - d - m) and a pivoted half-cylinder (e - f), one drawn 'upside-down.' Leonardo argues that every free weight expresses a natural desire to descend, so with the wheel held still the weight a falls to b, and each mass set above its axis moves as near as it can toward the center of the world.
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Free weights descend toward the center of the world
Because every free weight puts forth, wholly or in part, its natural desire to descend, with the wheel a b held still in the position shown, the weight a will descend to b. The weight c, set above the center of its axis, moves as near as it can to the center of the world, and m n below does exactly the same.
Pivoted wheel, half-wheel and half-cylinder
Three lettered devices are set out: a pivoted wheel (a - b), a pivoted half-wheel (n - c - d - m) and a pivoted half-cylinder (e - f). Each carries weights whose tendency to fall is used to reason about balance and descent.
Rustic stairs of the Count of Urbino
A heading records the 'rustic stairs of the Count of Urbino,' set beside sketches of steep, ladder-like staircases. The note is one of the manuscript's memoranda on stair design.