How wind builds a double wave on water
A wave-diagram (a d b, c e f) explaining how gusts redouble a wave
A red-chalk diagram at the head of the page shows a train of waves with the points a d b along the top and c e f below. The note explains that the wave grows because the wind grows: the wind d b e f strikes the water at e f and readies it to surge, and the second part of the same wind, d a e c, finds the water already prepared and drives against it, redoubling the force and so making a double wave. The passage treats waves as the cumulative product of successive gusts of wind.
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The wind redoubles its own wave
The wind d b e f strikes the surface e f and prepares it for flooding; the following part of the same wind, d a e c, meets the water at ce already raised and drives against it with its power, doubling the force d b e f. In this way one gust builds upon another to raise a double wave. The wave grows, Leonardo writes, because the wind grows.