The Smoke and Dust of Cities
Why smoke fades against sunlit roofs and dust reads darker
This page completes the discussion of smoke and dust over a city. With the sun in the east, smoke seen toward the west is no longer lit through by the sun's rays but stands against a dark ground, and because the sunlit roofs form a bright field behind it the smoke is barely visible. Dust in the same situation appears darker than smoke, being of a denser material than the humid substance of smoke. The leaf is text only, in mirror script.
On this page
Smoke fades against the sunlit western roofs
Toward the west the smoke of a city is not lit through by the solar rays but is seen against a dark ground. Because the sunlit roofs form a bright field behind it, the smoke there is barely visible.
Dust reads darker than smoke
Under the same conditions dust appears darker than smoke. This is because dust is of a denser material than smoke, which is a humid substance.