The moon's water, reflected sunlight, and eclipse light
Why the moon's seas reflect the sun to us, why it glows faintly in eclipse, and the sun's image on moving water.
Leonardo explains that the wavy surface of the moon's 'water' catches the sun's rays and reflects them to us, and that this water does not fall to earth because it weighs toward the center of its own sphere, not the center of the world. Using an eye moving along a canal and figures of reflected images, he shows that one moving toward the sun over water travels along a continuous image as long as the motion itself. He asks why the moon glows more in the western sky than during a solar eclipse, and why in eclipse the moon's disc shows a faint splendour 'like slightly heated iron', attributing it to light taken from the stars rather than the earth.
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The moon's water weighs toward its own sphere
The rays of the surface waves of the moon take the solar rays and reflect them to us. If the moon's water weighed toward the center of the world it would strip the moon and fall to us; but it weighs toward the center of its own sphere.
The shadowy pyramid and the faint light of eclipse
Let a be the eye and c d b the shadowy pyramid of the moon clothed in the sun's rays, ending in the point b; an eye within that pyramid sees no illuminated part of the moon. He also asks why in a solar eclipse the moon's disc glows faintly 'like slightly heated iron', answering that it takes this light from the stars, not the earth.
A continuous image of the sun on moving water
Three figures show images reflected along a straight line, lettered a - f e - d c - b. If you move toward the sun through the water lying between it and its image, you navigate along a continuous image whose length equals that of your motion.