The man who attends to his neighbor’s business generally has his hands full. So has the man who attends to the motions of his neighbor, the moon. By the time he investigates her parallax, diameter, distance, revolution on her axis, sidereal and synodic revolutions, the form of her orbit, her phases, discusses her physical properties, determines her heat, height of her mountains, size of her craters, describes her librations, decides upon the effect she exercises on the weather, and a thousand more or less of other things, he had better settle down and make it the business of his life. And if he does, he may be able to show some good results of his labors. It is well for us that not any single man, but many men, have given our satellite so much attention; for it is only by the uniting of the results of their researches that we are enabled with comparative ease to predict what business our neighbor has on hand, and when and how she will perform her duties. Thus, we find that she will this month present the following phases: On the 5th, at 5:47 a. m., full; on the 12th, at 3:08 a. m., last quarter; on the 19th, at 4:29 a. m., new moon; on the 27th, at 5:13 a. m., first quarter. She will rise on the 15th at 1:39 a. m., and set on the 1st and 30th at 1:36 a. m. and 1:18 a. m., respectively. At 12:54 p. m., on the 10th, will be nearest the earth (in perigee), and on the 25th, at 12:54 (exactly fifteen days later), farthest from the earth, or in apogee. Greatest elevation on the 12th, amounting to 66° 54⅔′; least elevation on the 26th, equaling 30° 8′.
MERCURY
Will be evening star till the time of its inferior conjunction on the 19th, after which it will be morning star. It appears stationary on the 6th, and also again on the 28th. On the 19th it is 1° 34′ south of the moon. Its apparent diameter increases from 8.4″ to 10.4″, and then diminishes to 7.4″ at the close of the month. It sets on the 1st at 7:08 p. m.; on the 15th at 6:05 p. m.; and rises on the 30th at 4:37 a. m.
VENUS
Reaches her greatest distance east of the sun, 46° 6′, on the 29th, at 7:00 a. m. Her diameter decreases from 30.8″ to 22″; and her direct motion amounts to 27° 40′ 55.2″. On the 15th, at 1:08 p. m., she is 2° 26′ north of the moon. She rises on the 1st, 15th and 30th, at 2:00, 1:59, and 2:11 a. m., respectively.
MARS
Still retains his position as evening star, setting on the evening of the 1st, 15th and 30th in the same order, at 8:08, 7:36 and 7:11. His diameter decreases from 4.8″ to 4.6″. Direct motion amounts to about 18° 40′ 12″ of arc. He is 2° 20′ south of the moon on the 22nd, at 6:48 a. m.
JUPITER
Is morning star, rising at the following times: 1st, at 3:55 a. m.; 15th, at 3:16 a. m.; 30th, at 2:32 a. m. Its motion is direct, and equals about 5° 45′ 14″ of arc. Its diameter increases one second, being on the 30th 31″. On the 16th, at 8:30 p. m. is 4° 55′ north of the moon.
The satellites of Jupiter, four in number and designated as 1, 2, 3, 4, outwardly from the planet, are frequently used to find the longitude. To do this, however, requires the use of a telescope. By observing the time at which one of these satellites passes into or emerges from the shadow of its primary, and comparing this time with the recorded time of the same event in Washington City, for example, one can determine whether he is east or west of this city, and how many degrees. On the 14th No. 1 enters the shadow of Jupiter at 4:46 a. m., Washington mean time. Suppose the observer at Allegheny Observatory should note the same event as occurring at exactly 57 minutes 50.84 seconds after four, Allegheny Observatory time. He would find the difference of the two times to be 11 m. 50.84 s., which reduced to longitude by multiplying by 15 (since one hour of time equals 15° of arc) gives the difference of longitude 2° 57′ 40.3″. And since the ingress occurred at Allegheny Observatory at an earlier hour (by its local time) than by Washington local time, it follows that the latter place is 2° 57′ 40.3″ east of the former.