Clouds by Night Beneath the Moon; A Rule for Their Redness
Transparency and whiteness of moonlit clouds, and a closing rule to redden clouds near the horizon.
Concluding the account of night clouds, Leonardo describes how a cloud's middle grows brighter while its bright parts turn opaque with a deadened redness, its dark and light edges dissolving into smoky, confused boundaries. Thin clouds are wholly transparent, and the farther a cloud lies from the moon the whiter its light, while a very thin cloud has little brightness because the darkness of night penetrates it. A brief closing section instructs the painter to make clouds cast their shadows on the earth and to redden them the nearer they stand to the horizon. This page ends Part Seven's text; it carries writing only, with a Vatican Library stamp below and no diagrams.
On this page
Transparency and reddening at a cloud's core
The middle of the clouds becomes brighter, while their bright parts turn more opaque, reddening with a deadened red. The edges of their darkness, entering the transparent brightness, form smoky, confused boundaries, and so do the bright edges that terminate against the air. Clouds of small thickness are wholly transparent, more so at the middle than the edges.
Night clouds are whiter the farther from the moon
The more a cloud is distant from the moon, the whiter its light, which increases around the cloud's shadowiness and especially toward the moon. A thin cloud has no blackness and little whiteness, because into it penetrates the darkness of the night that shows itself in the air.
Rule: cast cloud-shadows, redden clouds near the horizon
Make the clouds cast their shadows on the earth, and make the clouds of so much greater redness the nearer they are to the horizon. This closing instruction restates for the painter the rules developed through Part Seven on clouds.