Labels:text | human face | head covering | person | woman | screenshot OCR: As proof of Aristotle's theory on the nature of the atmosphere and the darkness of the "sphere of fire," Leonardo describes an experiment in glazing: "But to see the final proof of this, a board should be stained with various colors, including a most beautiful black, and a coat of thin transparent white should be applied over them all. The luster of the white nowhere will then be seen to display a more beautiful blue than over the black, but it should be applied very thin and finely ground." (4r)
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