The Redness and Splendor of Clouds; How Clouds Are Made
Why cloud-edges glow, where the eye sees most splendor, and how moisture gathers into clouds.
Continuing the account of clouds' redness, Leonardo argues that the thinner edges of each cloud-globe let the solar rays through with more resplendent red than the thick, impenetrable middles. He sets out the geometry of the eye placed between cloud and sun, showing where the greatest splendor appears, and distinguishes the case of the sun behind the clouds from that of the sun in front of them. A new section then opens on the creation of clouds from moisture gathered by cold winds, noting that clouds generate winds both in their forming and in their dissolving. The page is text only, with no diagrams.
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Why cloud-edges glow redder than their cores
The globes of a cloud are thinner at their edges than in the middle, so the solar rays penetrate the edges with more resplendent redness. The thick central parts remain dark, being impenetrable to those rays. Because clouds are always thinnest where their globosities meet, their redness is of various qualities of red.
Where the eye sees the greatest splendor
An eye placed directly between the cloud-globosities and the body of the sun sees the middles of those globes as brightest. But if the eye is to one side, so that the lines from globosity to eye and from sun to eye make an angle less than a right angle, the greatest light falls at the edges of the globes. The redness described holds when the sun is behind the clouds; with the sun in front, the globes shine brighter than their intervals.
The creation of clouds from moisture and wind
Clouds are created from moisture infused through the air, gathered together by the cold that various winds carry through the air. Such clouds generate winds both in their creation and in their destruction. In their creation the winds arise because the dispersed, vaporized moisture, coming together into a cloud, leaves empty the place from which it came.