Color of the Clouds.

The Scientific American 10, 7.3.1868

The varied colors which the clouds assume at various times especially at sunrise and sun-set, are explained by Mr. Sorley on the principle that the clear transparent vapor of water absorbs more of the red rays of light than of any other, while the lower strata of the at-mosphere offer more resistance to the passage of the blue rays. At sunrise and sunset the light of the sun has to pass through about 200 miles of atmosphere within a mile of the surface of the earth in order to illuminate a cloud a mile from the ground. In passing through this great thickness the blue rays are absorbed to a far greater extent than the red, and much of the yellow is also removed. Hence clouds thus illuminated are red. When the sun is higher above the horizon, the yellow light passes more readily and the clouds become orange, then yellow, and finally white. Clouds in different parts of the sky or at different elevations often show these various colors at the same time.