Why the water walls of an eddy stand higher than its hollow
A heavy body weighs only along the line of its motion; a catalogue of natural eddies
Returning to eddies, Leonardo asks why the water forming the sides of a deep eddy stands higher than the air-filled hollow at its centre, comparing such eddies to deep wells. He answers by his principle that a heavy body weighs only along the line of its own motion, so the revolving walls of water press nothing sideways while they hold the impetus their mover gave them. He then raises questions about why eddies hollow out at all, and whether water poured into the hollow would fill it. A double eddy figure and a marginal catalogue of the varieties of natural eddy accompany the text.
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Water walls weigh only along their line of motion
Since every heavy body weighs only along the line of its own motion and nowhere else, the deep sides of an eddy — standing higher than the air at its centre, like the walls of a well — press nothing sideways while they retain the power their mover gave them.
Open questions on why eddies hollow out
Leonardo asks why eddies form and why some are hollowed in the middle while others are not, and whether water poured into an eddy's hollow would fill it or escape through the bottom into the lateral current.
A catalogue of the kinds of natural eddy
A marginal note lists the varieties of natural eddies: which sink deep and which shallow, which shift position and which stay fixed, which draw toward their centre and which lift, which reverse into contrary motions and which turn one way only, and which double or join with contrary motions.