GEOGRAPHY OF THE HEAVENS FOR APRIL.

BY PROF. M. B. GOFF, Western University of Pennsylvania.

THE SUN,

With its immediate attendants, Mercury, Venus, Earth, Mars, etc., has been the “theme of our discourse” for the last eighteen months. Except an occasional reference to one of the planets as being located near some fixed star, or in some constellation, little has been said about the 3,391 “fixed” stars, visible to the naked eye, many of which are located on maps of the heavens, just as villages, cities, mountains, rivers and plains are located on maps of the earth; nor of the somewhere between 30,000,000 and 50,000,000 which are visible only through powerful telescopes, and whose distances from the sun are so great as to make that of Neptune appear like a little walk “across lots” to visit a neighbor. Nor is it proposed now to enter upon such an extensive subject, except so far as may be necessary to present a single thought. As we know, our sun is a bright body, whose light and heat (so great is their power) we can hardly estimate. Both these qualities render it visible to us and make us realize its presence. The other bodies, as Mars, Jupiter and the Moon are seen only by reflected light, and were they as distant as the fixed stars, would not be at all visible. These 30,000,000 to 50,000,000 stars must be suns. How many satellites has each? We do not know, for they can not be seen. Suppose each had as many as our sun. Then instead of 30,000,000 to 50,000,000 of heavenly bodies, we have within reach of the telescope from 240,000,000 to 400,000,000. How many are outside of these? No man can number them. We shall have to wait till our minds can grasp the infinite. Are these millions of bodies standing still, or are they in motion? Does our sun stand still and permit us to go around him once every year, or is he, and are we along with him, making our way through other vast multitudes and moving around some other central orb? Observation proves that the sun is only a sergeant in a great army of generals, and marches his squad in an appointed way to their assigned duties. How do we know? The records of patient watchers for centuries reveal the fact. “If we suppose the sun, attended by planets, to be moving through space, we ought to be able to detect this motion by an apparent motion of the stars in a contrary direction, as when an observer moves through a forest of trees, his own motion imparts an apparent motion to the trees in a contrary direction. All the stars would not be equally affected by such a motion of the solar system. The nearest stars would appear to have the greatest motion, but all the changes of position would appear to take place in the same direction. The stars would appear to recede from that point of the heavens toward which the sun is moving, while in the opposite quarter the stars would seem to crowd more closely together.” Proceeding upon this principle, Sir William Herschel was in 1783 enabled to announce that the observed proper motion of a large portion of the stars could be accounted for on the supposition that the sun was moving toward the constellation Hercules. Later investigations not only established the fact that the sun moved, but that it was moving nearly toward the star Rho, in Hercules, and Struve estimated its motion at about five miles per second; though Professor Airy places it at about twenty-seven miles per second. It is also highly probable that its motion is not in a straight line, but in obedience to the same laws that govern the motions of its own satellites, it with other suns revolves about a center located nearly in the plane of the Milky Way, and with an orbit so great “that ages may elapse before it will be possible to detect any change in the direction of its motion.” Meantime, finite beings are interested in knowing how its light and heat affect their interests, and how these qualities may be made most profitable to mankind. For ourselves, we must at present be content to know that on the 1st our sun has reached a point 4° 48′ north of the equator, and that by the 30th he will be 14° 58′ north, an increase in northern declination of 10° 10′, and, as a consequence, our daylight will be increased about one hour and thirteen minutes, and the time “from early dawn to dewy” twilight will be seventeen hours and thirty-five minutes. On the 1st sunrise occurs at 5:43 a. m., sunset, 6:24 p. m.; on the 16th, sunrise, 5:19, sunset, 6:40; on the 30th, sunrise, 4:59, sunset, 6:54.

THE MOON.

The phases for the month are as follows: Last quarter, 7th, at 9:34 a. m.; new moon, 15th, at 12:43 a. m.; first quarter, 21st, at 6:12 p. m.; full moon, 29th, at 1:06 a. m. Rises on the 1st, at 8:38 p. m.; sets on the 16th, at 8:28 p. m.; rises on the 30th, at 8:21 p. m. In latitude 41° 30′ north, least elevation on the 6th, and equals 30° 20′; greatest elevation on the 19th, equals 66° 44′ 29″.

MERCURY

Will be an evening star during the month; it will have a direct motion of 12° 25′ 59″ up to the 17th, after which, to the end of the month, a retrograde motion of 5° 22′ 11″. On the 8th, at 2:00 a. m., will be at its greatest eastern elongation (19° 26′); on the 16th, at 11:55 a. m., will be 6° 21′ south of the moon; on the 17th, at 5:00 a. m., will be stationary; on 27th, at 10:00 p. m., will be in inferior conjunction with the sun—that is, will be between the earth and sun; and next day, at 1:00 p. m., will be 1° 42′ north of Venus. A few days before and after the 8th may be seen as a pale, light star, near the western horizon. Its times of rising and setting are as follows: On the 1st, rises at 6:21 a. m., sets at 7:51 p. m.; on the 16th, rises at 5:50 a. m., sets at 8:00 p. m.; on 30th, rises at 4:53 a. m., sets at 6:29 p. m. Diameter increases from 6.4″ to 11.8″.

VENUS,

Like Mercury, will be evening star throughout the month, and near the 28th the two will keep “close company,” but will so completely hide themselves in the light of “Old Sol” as to be entirely indifferent to the gaze of the “vulgar crowd.” On the 1st Venus rises at 5:34 a. m., and sets at 5:34 p. m., being just twelve hours above the horizon; on the 16th, rises at 5:19 a. m., sets at 6:09 p. m.; on 30th, rises at 5:06 a. m., sets at 6:42 p. m. Diameter diminishes during the month two tenths of a second; motion, 34° 38′ 45″ eastwardly; on the 14th, at 3:00 p. m., six minutes north of the moon.

MARS

Has a direct motion of 21° 13′ 16″, and his diameter increases two tenths of one second. On the 14th, at 12:27 a. m., 12′ south of the moon. On the 1st, rises at 5:29 a. m., sets at 5:25 p. m.; on the 16th, rises at 4:56 a. m., sets at 5:24 p. m.; on the 30th, rises at 4:27 a. m., sets at 5:23 p. m.; on the 14th, at 12:27 a. m., twelve minutes south of moon.

JUPITER

May well be called this month the “Ruler of the Night.” From twilight till near the dawn his broad face looks condescendingly upon our little world, and by his example cheerily bids us “pursue the even tenor of our way.” Jupiter rises on the 1st at 2:26 p. m., sets next morning at 4:02 a. m.; on the 16th, rises at 1:24 p. m., sets on 17th at 3:02 a. m.; rises on 30th, at 12:29 p. m., and sets next morning at 2:07 a. m. Before the 21st, retrograde motion amounts to 36′ 26″; after that date to end of month, direct motion equals 8′ 42″; diameter diminishes three seconds, from 40.4″ to 37.4″. On 21st, at 3:00 p. m., stationary; on 23d, at 2:05 p. m., 4° 37′ north of the moon. It might be observed in passing that as a mean result of five years’ observations at the Dearborn Observatory, Chicago, the time of Jupiter’s rotation has been discovered to be greater by three seconds than was supposed in 1879.

SATURN

Sets at the following times: On the 1st, at 11:49 p. m.; on 16th, at 10:57 p. m.; on the 30th, at 10:09 p. m.; is, therefore, an evening star, and will remain so till the 18th of June. On the 18th, at 8:20 p. m., 4° 1′ north of the moon. Diameter diminishes from 16.6″ to 16″. Makes a forward (direct) motion of 3° 2′ 30″. For observation, this month is preferable to May. Can be found a little northwest of Zeta, in the constellation Taurus.

URANUS,

Unlike Saturn, retrogrades nearly one degree of arc during the present month, and shines from early eve to break of day, rising on the 1st at 5:18 p. m., and setting on the 2d at 5:22 a. m.; on the 16th, rising at 4:17 p. m., and setting next morning at 4:21; and on the 30th, rising at 3:19 p. m., and setting May 1st at 3:23 a. m., and can be seen all night by those who know where to find him (a little southwest of Eta, in the constellation Virgo). On 26th, at 12:16 a. m., 1° 17′ north of moon.

NEPTUNE,

Not only the father of waters, but water himself, scarcely visible at best, “hangs out” all day, rising soon after the sun, and setting as follows: On the 1st, at 9:36 p. m.; on the 16th, at 8:40 p. m.; on the 30th, at 7:46 p. m. Has a retrograde motion of 58′ 16″; and on the 16th, at 8:42 p. m., is 2° 13′ north of the moon.

We have now passed the boundary of the first century of our existence as an independent nation. We are as a people engaged in a confused struggle with the problem of our own national self-consciousness. We want to know what is the spirit that is in us as a nation. We must know this in order to be properly master of ourselves and of our destiny. We must know this in order to know our place in universal history.—George S. Morris.