"Those who know Sirius and Betel do not at once perceive that one shines with a brilliant white light and the other burns with a glowing red, as different in their brilliancy as the precious stones on a lapidary's table, perhaps for the same reason. And so there is an endless variety of tints of paler colors.
"We may turn our gaze as we turn a kaleidoscope, and the changes are infinitely more startling, the combinations infinitely more beautiful; no flower garden presents such a variety and such delicacy of shades.
"But beautiful as this variety is, it is difficult to measure it; it has a phantom-like intangibility—we seem not to be able to bring it under the laws of science.
"We call the stars garnet and sapphire; but these are, at best, vague terms. Our language has not terms enough to signify the different delicate shades; our factories have not the stuff whose hues might make a chromatic scale for them.
"In this dilemma, we might make a scale of colors from the stars themselves. We might put at the head of the scale of crimson stars the one known as Hind's, which is four degrees west of Rigel; we might make a scale of orange stars, beginning with Betel as orange red; then we should have
Betelgeuze, Aldebaran, ß Ursae Minoris, Altair and a Canis, a Lyrae,
the list gradually growing paler and paler, until we come to a Lyrae, which might be the leader of a host of pale yellow stars, gradually fading off into white.
"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.