colors are combined, and assuming that which is least intense among them, combine with it the proportion of the other two, which is necessary to produce white, the resulting tint will be such as would be produced by the balance of the remaining colors diluted by the resulting white.

By following out this reasoning, it will be seen how the infinite variety of tints of color may be produced by the simple component colors, red, yellow, and blue, existing in different degrees of intensity.

The color called black is produced by the absence of all light, and is, in fact, a name for absolute darkness. If it were possible to find a substance absolutely incapable of reflecting any light to the eye, or what is the same, of absorbing all the light which falls upon it, such substance would appear absolutely black. But as no substance in nature is, on the one hand, capable of reflecting all the light which falls upon it, so, on the other hand, no substance in nature is capable of absorbing all the light that falls upon it. If we take the blackest known substance and throw upon it strongly-condensed light, it will become distinctly visible to the eye by a small portion of light which it will reflect, which will make it appear of a gray color, or faint white. It appears, then, that objects which are popularly termed black, are, in fact, faintly white. A true black would be an object having no color at all.

Experiments made on finely-divided substances have proved that there is no substance absolutely opaque. The most dense substances known, and those that are, apparently, most impervious to light, are found, when cut into leaves or filaments sufficiently thin, to be transparent; but the light which goes through them is always of a tint contrary to that which they reflect. Thus if an object appears to the eye to be of a yellow color, we know that the reason is that it reflects to the eye yellow light. What, then, becomes, it may be asked, of the red and the blue components of the solar light which falls upon it? If we obtain a shaving of the body sufficiently thin, and look behind it, we shall find that it will appear of a color composed of the red and blue; that is, it transmits through it the colors which it fails to reflect.

Hence it has been inferred that the absorption of light which takes place in colored bodies is effected, not immediately on their surface, but at some definite depth within their dimensions, and that such portion of the compound solar light that falls upon it, as is not reflected, passes successively through lamina, one within another, each of which absorbs a portion of it, until, at length, it is altogether lost.

As heat is, by some means not clearly known to us, connected with light, we have, in these circumstances, a clear explanation of the fact, that more heat is absorbed by bodies of a dark color than by those of a light color. In general the lighter the color the greater the proportion is of the reflected light, and the darker the color the less the proportion is. The greater the proportion of light that is absorbed the greater will be the proportion of the heat which attends that light. Hence it follows that, as dark colors absorb more heat than light ones, and as black absorbs the most of all, dark colors are, in general, warm, and black the most so. If two pieces of cloth be thrown upon snow, one black and the other white, the black will sink through it, melting the snow under it, before the other penetrates into it perceptibly.

Hence, dark-colored cloths are most suitable in cold weather, and light-colored in warm weather.

After all that has been explained, it will be scarcely necessary to say that the sense in which color is commonly understood to be a quality of bodies, is incorrect, and, strictly speaking, it is true, although it may sound paradoxical to say that leaves are not green, and that the sky is not blue. The green and the blue colors belong, properly speaking, not to the objects which appear to

the eye to be green or blue, but to the light which they reflect from their surfaces. A red object is one which reflects red light and absorbs all other colors, a blue object one which reflects blue light and absorbs other tints, and so The color of a body, then, or more properly, the cause which produces the color, is the quality possessed by its particles to reflect certain lights and absorb others.

on.

That the color which seems to belong to a body is not really inherent in the body, or inseparable from it, is proved by showing that we can give any color that may be desired to a body by exposing it to light of that peculiar tint. Thus if a piece of blue cloth be illuminated by a beam of pure red light, it will appear red; or, if by yellow light, it will appear yellow; but neither the yellow, nor the red, will be as vivid as the color it would exhibit if illuminated by blue light.

THE

VISIBLE STARS.

What occupies the Space beyond the Limits of the Solar System.-Wide Vacuity between this System and the Stars.-Indications of this observable in the Motions of the Planets-Indications in the Motions of the Comets.-The immense Distance of the Stars proved by the Earth's annual Motion.-Observations made at Greenwich.-Bessel's Discovery of the Parallax.-The consequent Distance of the Stars.-Illustrations of the Magnitude of this Distance.—The different Orders and Magnitudes of the Stars.-How accounted for.-Why those of the lowest Magnitude are most Numerous. The real Magnitude of the Stars.-The Telescope unable to Magnify them.-Dr. Wollaston's Investigations of the comparative Brightness and Magnitude of the Stars in Relation to the Sun. Their stupendous Magnitude.-Application of this to the Dog-star.

the eye to be green or blue, but to the light which they reflect from their surfaces. A red object is one which reflects red light and absorbs all other colors, a blue object one which reflects blue light and absorbs other tints, and so The color of a body, then, or more properly, the cause which produces the color, is the quality possessed by its particles to reflect certain lights and absorb others.

on.

That the color which seems to belong to a body is not really inherent in the body, or inseparable from it, is proved by showing that we can give any color that may be desired to a body by exposing it to light of that peculiar tint. Thus if a piece of blue cloth be illuminated by a beam of pure red light, it will appear red; or, if by yellow light, it will appear yellow; but neither the yellow, nor the red, will be as vivid as the color it would exhibit if illuminated by blue light.

THE

VISIBLE STARS.

What occupies the Space beyond the Limits of the Solar System.-Wide Vacuity between this System and the Stars.-Indications of this observable in the Motions of the Planets.-Indications in the Motions of the Comets.-The immense Distance of the Stars proved by the Earth's annual Motion.-Observations made at Greenwich.-Bessel's Discovery of the Parallax.-The consequent Distance of the Stars.-Illustrations of the Magnitude of this Distance.-The different Orders and Magnitudes of the Stars.-How accounted for.-Why those of the lowest Magnitude are most Numerous. The real Magnitude of the Stars.-The Telescope unable to Magnify them.-Dr. Wollaston's Investigations of the comparative Brightness and Magnitude of the Stars in Relation to the Sun. Their stupendous Magnitude.—Application of this to the Dog-star.