Eddies, Sediment, and Why a River Is Never Level
Large and small whirlpools, the travel of light matter, and gravel bars
Four observations on flowing water, written in Leonardo's mirror script with no diagram on the sheet. In large wide eddies the water rises and lays bare the ground heaped in the middle, while small eddies instead bore and hollow out their centre. Of matter carried along the bed, the lightest travels furthest in equal time. He states that a river is never level, because after each current it deposits gravel and a new current is generated, whose course is steered to bank, middle, or many places by the ridges of gravel left behind.
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Large versus small eddies
In large, wide eddies the water rises and uncovers the ground heaped up in the middle. In small eddies the water instead bores and hollows out the very centre of the eddy.
Why a river is never level
After each current the river loads gravel, and then a further current is generated. Its motion is directed to the bank, the middle, or to as many different places as there are ridges of the gravel mounds left in the bed by the previous currents.