White, you perceive, results from a body reflecting all the rays which fall upon it; black, is produced, when they are all absorbed; and colour, arises from a body possessing the power to decompose the solar ray, by absorbing some parts, and reflecting others.
Caroline. What is the reason that articles which are blue, often appear green, by candle-light?
Mrs. B. The light of a candle, is not of so pure a white as that of the sun: it has a yellowish tinge, and when refracted by the prism, the yellow rays predominate; and blue bodies reflect some of the yellow rays, from their being next to the blue, in the order of refrangibility; the superabundance of yellow rays, which is supplied by the candle, gives to blue bodies, a greenish hue.
Caroline. Candle-light must then give to all bodies, a yellowish tinge, from the excess of yellow rays; and yet it is a common remark, that people of a sallow complexion, appear fairer, or whiter, by candle-light.
Mrs. B. The yellow cast of their complexion is not so striking, when every surrounding object has a yellow tinge.
Emily. Pray, why does the sun appear red, through a fog?
Mrs. B. It is supposed to be owing to the rays, which are most refrangible, being also the most easily reflected: in passing through an atmosphere, loaded with moisture, as in foggy weather, and also in the morning and evening, when mists prevail, the violet, indigo, blue, and green rays, are reflected back by the particles which load the air; whilst the yellow, orange, and red rays, being less susceptible of reflection, pass on, and reach the eye.