The Da Vinci Notebooks
Constituents of the atmosphere.That the brightness of the air is occasioned by the water which has dissolved itself in it into imperceptible molecules. These, being lighted by the sun from the opposite side, reflect the brightness which is visible in the air; and the azure which is seen in it is caused by the darkness that is hidden beyond the air. 530
219:530 : Compare Vol. I, No. 300.