"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. Almost all of these are stars of the eighth to tenth magnitude; only once are both seen blue, and only in one case is the large one blue. In almost every case the large star is yellow. The color most prevailing is yellow; but the varieties of yellow are very great. "We may assume, then, that the blue stars are faint ones, and probably distant ones. But as not all faint stars or distant ones are blue, it shows that there is a real difference. In the star called 35 Piscium, the small star shows a peculiar snuffy-brown tinge. "Of two stars in the constellation Ursa Minoris, not double stars, one is orange and the other is green, both very vivid in color. "From age to age the colors of some prominent stars have certainly changed. This would seem more likely to be from change of place than of physical constitution. "Nothing comes out more clearly in astronomical observations than the immense activity of the universe. 'All change, no loss, 'tis revolution all.'