In the double star we shall find a good light test for our three-inch aperture, the magnitudes being six and eleven, distance 22", p. 212°. The four-inch will show that is a double, magnitudes four and ten, distance 6", p. 232°. The smaller star

smaller than our planet Jupiter, but shining, of course, by its own light. Its distance from Pollux, however, exceeds that of Jupiter from the sun in the ratio of about one hundred and thirty to one.

K

1s of a delicate blue color, and it has been suspected of variabulity. That it may be variable is rendered the more probable by the fact that in the immediate neighborhood of x there are three undoubted variables, S, T, and U, and there appears to be some mysterious law of association which causes such stars to group themselves in certain regions. None of the variables just named ever become visible to the naked eye, although they all undergo great changes of brightness, sinking from the eighth or ninth magnitude down to the thirteenth or even lower. The variable R, which lies considerably farther west, is well worth attention because of the remarkable change of color which it sometimes exhibits. It has been seen blue, red, and yellow in succession. It varies from between the sixth and seventh magnitudes to less than the thirteenth in a period of about two hundred and forty-two days.

Not far away we find a still more curious variable ; this is also an interesting triple star, its principal component being a little under the third magnitude, while one of the companions is of the seventh magnitude, distance 90", p. 355°, and the other is of the eleventh magnitude or less, distance 65", p. 85°. We should hardly expect to see the fainter companion with the three-inch. The principal star varies from magnitude three and seven tenths down to magnitude four and a half in a period of a little more than ten days.

With the four or five inch we get a very pretty sight in 8, which appears split into a yellow and a purple star, magnitudes three and eight, distance 7", p. 206°.

Near 8, toward the east, lies one of the strangest of all the nebulæ. (See the figures 1532 on the map.) Our telescopes will show it to us only as a minute star surrounded with a nebulous atmosphere, but its appearance with instruments of the first magnitude is so astonishing and at the same time so beautiful that I can not refrain from giving a brief description of it as I saw it in 1893 with the great Lick telescope. In the center glittered the star, and spread evenly around it was a circular nebulous disk, pale yet sparkling and conspicuous. This disk was sharply bordered by a narrow black ring, and outside the ring the luminous haze of the nebula again appeared, gradually fading toward the edge to invisibility. The accompanying cut gives but a faint idea of this most singular nebula. If its peculiarities were within the reach of ordinary telescopes, there are few objects in the heavens that would be deemed equally admirable.

In the star we have another long-period variable, which is

η

also a double star; unfortunately the companion, being of only the tenth magnitude and distant less than 1" from its third-magnitude primary, is beyond the reach of our telescopes. But 7 points the way to one of the finest star clusters in the sky, marked 1360 on the map. The naked eye perceives that there is something remarkable in that spot, the opera glass faintly reveals its distant. splendors, but the telescope fairly carries us into its presence. Its stars are innumerable, varying from the ninth magnitude downward to the last limit of visibility, and presenting a wonderful array of curves which are highly interesting from the point of view of the nebular origin of such clusters. Looking backward in time, with that theory to guide us, we can see spiral lines of nebulous mist occupying the space that now glitters with interlacing rows of stars. It is certainly difficult to understand how such lines of nebula could become knotted with the nuclei of future stars, and then gradually be absorbed into those stars; and yet, if such a process does not occur, what is the meaning of that narrow nebulous streak in the Pleiades along which five or six stars are strung like beads on a string? The surroundings of this cluster, 1360, as one sweeps over them with the telescope gradually drawing toward the nucleus, have often reminded me of the approaches to such a city as London. Thicker and closer the twinkling points become, until at last, as the observer's eye follows the gorgeous lines of stars trending inward, he seems to be entering the streets of a brilliantly lighted metropolis.

Other objects in Gemini that we can ill miss are: μ, double, magnitudes three and eleven, distance 73", p. 76°, colors yellow and blue; 15, double, magnitudes six and eight, distance 33", p. 205°; y, remarkable for array of small stars near it; 38, double, magnitudes six and eight, distance 6'5", p. 162°, colors yellow and blue (very pretty); λ, double, magnitudes four and eleven, distance 10", p. 30°, color of larger star blue-try with the five-inch; , double, magnitudes three and nine, distance 110", p. 94°.

From Gemini we pass to Cancer. This constellation has no large stars, but its great cluster Præsepe (1681 on map No. 4) is easily seen as a starry cloud with the naked eye. With the telescope it presents the most brilliant appearance with a very low power. It was one of the first objects that Galileo turned to when he had completed his telescope, and he wonderingly counted its stars, of which he enumerated thirty-six, and made a diagram showing their positions.

The most interesting star in Cancer is, a celebrated triple. The magnitudes of its components are six, seven, and seven and a half; distances 1", p. 35°, and 5'5", p. 122°. We must use our fiveinch glass in order satisfactorily to separate the two nearest stars. The gravitational relationship of the three stars is very peculiar.

The nearest pair revolve around their common center in about fifty-eight years, while the third star revolves with the other two, around a center common to all three, in a period of six or seven hundred years. But the movements of the third star are erratic, and inexplicable except upon the hypothesis advanced by Seeliger, that there is an invisible, or dark, star near it by whose attraction its motion is perturbed.

In endeavoring to picture the condition of things in Cancri we might imagine our sun to have a companion sun, a half or a third as large as itself, and situated within what may be called planetary distance, circling with it around their center of gravity; while a third sun, smaller than the second and several times as far away, and accompanied by a black or non-luminous orb, swung with the first two around another center of motion. There you would have an entertaining complication for the inhabitants of a system of planets!

Other objects in Cancer are: 1223, double star, magnitudes six and six and a half, distance 5", p. 214°; Σ 1291, double, magnitudes both six, distance 13", p. 328°-four-inch should split it; , double, magnitudes four and a half and six and a half, distance 30", p. 308°; 66, double, magnitudes six and nine, distance 4'8", p. 136°; ≥ 1311, double, magnitudes both about the seventh, distance 7", p. 200°; 1712, star cluster, very beautiful with the fiveinch glass.

The constellation of Auriga may next command our attention (map No. 5). The calm beauty of its leading star Capella awakens an admiration that is not diminished by the rivalry of Orion's brilliants glittering to the south of it. Although Capella must be an enormously greater sun than ours, its spectrum bears so much resemblance to the solar spectrum that a further likeness of condition is suggested. No close companion to Capella has been discovered, and it is not probable that any exists except, possibly, in the form of planets which no telescope can reveal. A ninth-magnitude companion, distant 159", p. 146°, and two others, one of twelfth magnitude at 78", p. 317°, and the other of thirteenth magnitude at 126", p. 183°, may be distant satellites of the great star, but not planets in the ordinary sense, since it is evident that they are self-luminous. It is as ignificant fact that most of the first-magnitude stars have faint companions which are not so distant as altogether to preclude the idea of physical relationship.

While we are in Auriga we must look at the star ẞ (Menkalina), which belongs to a peculiar order of double stars discovered within the past few years. But neither our telescopes, nor any telescope in existence, can directly reveal the duplicity of ẞ Auriga to the eye-i. e., we can not see the two stars composing it,

shows that the star is double and that its components are in rapid revolution around one another, completing their orbital swing in the astonishingly short period of four days! The combined mass of the two stars is estimated to be two and a half times the mass

because they are so close that their light remains inextricably mingled after the highest practicable magnifying power has been applied in the effort to separate them. But the spectroscope