532. Why does the sky appear red at sunset?
Because the light vapours of the air, which are condensed as the sun sets, refract the rays of light, and produce red rays. The refraction which produces red requires only a moderate degree of density.
533. Why do the clouds sometimes appear yellow?
Because there is a larger amount of vapour in the air, which produces a different degree of refraction, resulting in yellow.
534. Why does a yellow sunset foretell wet weather?
Because it shows that the air is heavy with vapours. The refraction that produces yellow requires a greater degree of density.
"When it is evening ye say it will be fair weather, for the sky is red."—Matt. xvi.