"Most of the stars seen with the naked eye are varieties of red, orange,
and yellow. The reds, when seen with a glass, reach to violet or dark
purple. With a glass, there come out other colors: very decided greens,
very delicate blues, browns, grays, and white. If these colors are
almost intangible at best, they are rendered more so by the variations
of the atmosphere, of the eye, and of the glass. But after these are all
accounted for, there is still a real difference. Two stars of the class
known as double stars, that is, so little separated that considerable
optical power is necessary to divide them, show these different tints
very nicely in the same field of the telescope.
"Then there comes in the chance that the colors are complementary; that
the eye, fatigued by a brilliant red in the principal star, gives to the
companion the color which would make up white light. This happens
sometimes; but beyond this the reare innumerable cases of finely
contrasted colors which are not complementary, but which show a real
difference of light in the stars; resulting, perhaps, from
distance,--for some colors travel farther than others, and all colors
differ in their order of march,--perhaps from chemical differences.
"Single blue or green stars are never seen; they are always given as the
smaller companion of a pair.
"Out of several hundred observed by Mr. Bishop, forty-five have small
companions of a bluish, or greenish, or purplish color.
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