Motion, weight, and wheels: the mover and the moved
Balances, inclined obliquities, and bodies driven by water and by wind
This double page gathers Leonardo's propositions on weight and motion. He argues that a body wedged between two wheels cannot descend, that the moved is never swifter than its mover, and that along equal obliquities the ease of descent exactly matches the difficulty of ascent. Small captioned sketches show bodies displaced by water and by wind, while a closing note challenges the philosophers' claim that heaviness increases toward the center of the world. Numerous wheels, circles, and balances are drawn across both leaves.
On this page
Why weight b on the two wheels cannot descend
The heavy body b resting between a larger and a smaller wheel cannot fall, because the path a c between the supports is far shorter than the bent line a b c that runs from the larger wheel's pole through the contact point o to b and on to c. The geometry locks the weight in place.
Maxims on the mover, the moved, and weight on a wheel's rim
A moved body is never faster than its mover and reaches greatest speed at the instant of separation. A weight on a wheel's rim weighs according to its transverse distance from the center; if propped from the contact upward it is directed toward the wheel's center rather than the world's center.
Easy descent, hard ascent along equal obliquities
Where descent is easier, ascent is harder. Since the obliquity m s equals n r and s f equals r n, the ease of the descent m s f equals the difficulty of the ascent n r a, so equal things do not overcome one another.
A body driven out of place by water
One small captioned figure marks a body d driven out of position c by the water. It sits among notes comparing the natural descent of a heavy body in water to the oblique motion of a river.
A body driven by the wind
A companion figure marks a body a driven from f by the wind, pairing the action of moving air with that of moving water in the study of what displaces a resting body.
A falling weight and the philosophers on gravity toward the center
Weighing the spaces n o and o c against the weights of bodies c and a, Leonardo finds the higher body a to be heavier, contrary to philosophers who say heaviness grows nearer the center of the world. He notes that experience yields more motion than their rule predicts.