Cascade and the Boiling-Up of Water
Why eddies and up-leaping waters form at the foot of a fall
A pen study shows a cascade pouring down a slope into churning water, with a tight spiral vortex sketched at the upper right. The note asks how the boilings, or up-leapings, of water arise in the midst of the eddies above. Leonardo weighs three causes: whether the eddies run toward the lowered point of the water's impact, whether the thrust of the current down the middle of the surface piles the water into a mound that then flows back toward its entry into the pool, or whether water struck and pressed by the current simply spurts and leaps up.
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Three hypotheses for the boiling-up of water
Here arise the boilings, or up-leapings, of water in the midst of the eddies above. He asks whether their motion comes from running toward the lowered point of the water's impact; or whether the current's thrust down the middle of the surface strikes the other waters, raises them into a mound, and drives water back toward its entry into the pool; or whether water struck and pressed by the current spurts and leaps up.
Drawing of a cascade and a spiral vortex
The sheet shows a cascade pouring down a broken slope into agitated water, its foam rendered in fine parallel strokes. A separate, tightly wound spiral at the upper right records a single rotating eddy.