IT IS a very unusual thing that two comets, conspicuous to the naked eye, should be in sight at once. Such was the case, however, during the early part of October, when Brooks's comet was still a prominent object in the evening sky, and could also be seen before dawn, while farther to the south, in the morning sky, appeared another comet, of about the same brightness. This latter object, discovered by the Russian astronomer Beljawsky on September 28th, reminds one in some ways of the great comet of January, 1910. Both were first observed as conspicuous naked-eye objects, rising shortly before the sun, and in both cases it was some time before satisfactory observations of position could he obtained, owing to the difficulty of seeing the nearby stars (which serve as reference points) upon the brightly illuminated morning sky. A satisfactory orbit has by this time been computed, which explains why the comet was not seen sooner. It was in perihelion, at a distance of 28 million miles from the sun, - on October 10th. Three weeks earlier it was more than twice as far from the sun, and probably less than one-quarter as bright. Moreover, its orbit stands almost at Tight angles to the plane of the ecliptic, so that it came from far south of the sun, and remained south of him (and hence in a very unfavorable position for northern observers) until about the time of discovery. At the date of writing it is in the evening sky, in 15 hours R. A. and 3 degrees south of the equator, and sets about 1% hours later than the sun. On November 1st it will be almost due west of the sun, at a distance of some 25 degrees,' and will still be observable; but, being already twice as far from the sun as at perihelion, and remoter, too, from the earth it will not be at all conspicuous, though it may be followed telescopically by southern observers for some time. Brooks's comet, which passed north of the sun on October 12th, at a distance of 36 degrees, is now a fine object in the morning sky. On November 1st it will be almost exactly on the celestial equator, not far from the star Gamma Virginis, and will rise fully .two hours before the sun. Its head, at last reports, was of the second magnitude, and its tail 20 degrees long, so that it will be well worth getting up to see, before the moon comes into the morning sky. Later in the month it recedes from us and from the sun, gets more and more nearly behind the latter, and disappears. Still a third comet, discovered by Quenisset on September 23rd, is under observation. This one requires the aid of a field glass, at least, to make it visible. Its orbit is likewise highly inclined to that of the earth, but its distance from the sun at perihelion (on November 12th) is 72 million miles. At the beginning of November it is in 15 hours 45 minutes R. A. and 13 degrees north declination, and is moving south and a very little east, at the rate of 1 degree a day. This puts it 1% hours west and 27 degrees north of the sun, so that it will be easily observable. It will probably be of about the seventh magnitude. A faint periodic comet, first discovered by Borelly in 1905, has been reobserved on its return at certain southern observatories, but, being visible only in the most powerful telescopes, is of little interest to us. The Heavens With the present month, a slight change is made in the manner in which the star-maps of our annual sequence are used. Up to this time they have shown the appearance of the sky during the early evening in the month of publication, or the later evening hours of the preceding month. There are some advantages in choosing our assumed hour of observation a little later, so that the same stars may still be seen, before twilight, during the month following that for which these articles are published. From this time, therefore, our map will show the sky as it appears at 10:30 P. M. in the middle of the month of publication, and at 8: 30 in the middle of the next month. Alt these hours, then, in November or December, the At 91 j> o 'clock: November 30^ NIGHT SKY: NOVEMBER AND DECEMBER heavens will appear as the accompanying map shows them. The Great Bear is low in the northeast, and Draco and Ursa Minor are beneath the pole. Cassiopeia and Cepheus are high up, just west of north. The brilliant Vega is setting in the northwest, and the cross of Cygnus stands erect, just to the left. The great square of Pegasus is the most conspicuous object in the western sky. Below It lies Aquarius, the constellation represented in our initial letter. This is one of the ancient signs of the zodiac, but contains no bright stars. Its most prominent group is a small Y (lying on its side) formed by the stars f, 'Y, and two others. This represents the water jar from which the Water-Bearer pours forth a stream marked by small stars too faint to be shown on our map, which flows downward, first to the right and then to the left, till it is swallowed by the Southern Fish, whose one bright star, Fomalhaut, is now low on the southwestern horizon. Of telescopic objects in Aquarius, we may mention the star f Aquarii (the middle one of the Y) a fine slow binary pair, separated by 3.5 seconds, whose period of revolution is probably a couple of thousand years. Due south is Cetus, with one conspicuous star, fl, standing very much alone about 30 degrees northeast of Fomalhaut. North of this is the inconspicuous group of Pisces, and the small but brighter one of Aries, with Andromeda still higher, right overhead. The most brilliant region of the whole heavens is now well up in the southeast, where Sirius has just risen. Orion is resplendent above him, and Taurus shines still higher up. Mars and Saturn, which are at present between Taurus and Aries, add their luster to the spectacle. Procyon is low down in the east, and Castor and Pollux are a little higher, and more to the north. Above them, the bright Capella marks the place of Auriga, and above this, almost overhead, is Perseus. Minima of the variable star Algol—may be observed at c P. M. on the 1st, 5 P. M. on the 4th, 10 P. M. on the 21st, 7 P. M. on the 24th, and so on; the eclipses coming on every' third day, about 3 hours 10 minutes earlier by the clock. , The Planets Mercury is evening star throughout November, but, being very far south of the Sun, is ill placed for observation. Toward the end of the month he may perhaps be seen as he sets about 5: 45 P. M. Venus is morning star, at her very best, rising in the neighborhood of 3 A. M. and getting high in the southeast before dawn. On the 16th she is in conjunction with the crescent Moon, and, when nearest, at about 2 P. M., will be less than a degree away. By this hour both will be low in the west, so, if we wish to see the planet in the daytime (which is perfectly easy if the sky is really clear) we will do better to go out in the forenoon, and look a couple of degrees east of the Moon. Mars is in opposition on the 24th and is visible-all night. He is farther from us than he was two years ago—47 millions miles— but his high northern declination makes up for this, by carrying him high in the sky, where we have to look through less of our own unsteady atmosphere in order to see him. To find him, it is only necessary to look eastward, and pick out the brightest and . reddest thing in sight. With even a small telescope, he shows a considerable disk. The darker markings which are the most conspicuous features of the Martian surface can be seen fairly well with small telescopes, and these will also show that the “polar cap” is at present inconspicuous, most if not all of the polar snows having disappeared during the long summer of the Martian southern hemisphere, now near its close. Jupiter is in conjunction with the Sun on the 17th, and is invisible throughout the month. Saturn is just past opposition, in Aries, about 20 degrees west of Mars, and is finely placed for observation, with the ring-system opened widely. The contrast in color and brightness between the two planets is conspicuous to the naked eye. Uranus is in Sagittarius, too low in the west at sunset to be well seen Neptune is in Gemini, coming to meridian about 4 A. M. in the middle of the month. The Moon is full at 11 A. M. on the 6th, in her last quarter at 2 A. M. on the 13th, new at 4 P. M. on the 20th, and in her last quarter at 9 P. M. on the 28th. She is nearest us on the 8th, and remotest on the 24th. She is in conjunction with Saturn on the 6th, Mars on the 7th, Neptune on the 11th, Venus on the 16th, Jupiter on the 20th, Mercury on the 22nd, and Uranus on the 25th. Princeton University Observatory.