The Restless Sphere of Water, and Movers versus Moved
Water seeking its level about the center of the world, ball-and-chain governors, and a water-wheel
Leonardo pairs a meditation on the 'sphere' of water and air — forever restless as it strives to return to its level about the center of the world — with a set of propositions on movers and things moved. He argues that what is moved cannot in turn move its mover, citing a water-wheel that cannot drag back the water once it has passed, and studies balls hung on chains ('augmentative motions') that fly outward from the axis so their chains stand equidistant. Notes on wear observe that a pole loaded unequally wears on one side only, while the balanced wheel c d e f scarcely wears its pole, so 'the wheel f moves better than any other.' Pen sketches show chain-and-ball governors on vertical spindles and a flywheel over a bladed wheel.
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Why water forever seeks its sphere about the world's center
The sphere of water and air desires its boundaries equally distant from the center of the world, and any part found outside always pushes downward. All the water lying farther out than the surface of its sphere is in continuous motion to return home, its speed varying with the width, depth and obliquity of the rivers it moves through.
'Augmentative motions' of balls on chains
Of six motions called augmentative, Leonardo asks which is best and why the weights, hung perpendicularly below the ends of their supporting chain, come to stand equidistant. Since the cause of motion first pulls the chain and then the ball, the thing pulled cannot give motion back to the cause of its motion; the balls simply seek to fly as far as they can from the center of their mover.
A moved thing cannot move its mover (r and S)
In moving S, the part r must necessarily go forward; hence S cannot be the mover of r. The point is set beside a small linked diagram lettered s, r.
Water-wheel and the balanced wheel (c d e f)
No thing moved can be a cause of motion to its mover: a wheel pulled by water cannot, once the water leaves it, pull that water back. The pole of an unequally loaded weight wears on one side only, toward the weight it moves, whereas the equally loaded wheel c d e f scarcely wears its pole, so the wheel f moves better than any other.