were no refraction. But by the refraction of the Sun's rays, occasioned by the atmosphere, he becomes visible some days sooner, and continues some days longer in sight, than he would otherwise do: so, that he appears above the horizon of either pole, before he has got below the horizon of the other. 1 And as he never goes more than 23 degrees and 28 minutes below the horizon of the poles, they have very little dark night; twilight being there, as well as at all other places, till the Sun be 18 degrees below the horizon. The full Moon being always opposite to the Sun, can never be seen while the Sun is above the horizon, except when the Moon falls in the northern half of her orbit; for when any point of the ecliptic rises, the opposite point sets. Therefore, as the Sun is above the horizon of the north pole from the 20th of March, till the 23d September; it is plain that the Moon when full, being opposite to the Sun, must be below the horizon during that half of the year. But when the Sun is in the southern half of the ecliptic, he never rises to the north pole; during this half of the year, every full Moon happens in some part of the northern half of the ecliptic which never sets. Consequently, as the polar inhabitants never see the full Moon in Summer, they have her always in the Winter; before, at, and after the full, shining during 14 of our days and nights. And when the Sun is at his greatest distance below the horizon, being then in Capricorn, the Moon is at her first quarter in Aries, full in Cancer, and at her third quarter in Libra. And as the beginning of Aries is the rising point of the ecliptic, Cancer the highest, and Libra the setting point, the Moon rises at her first quarter in Aries, is most clevated above the horizon, and full in Cancer, and sets at the beginning of Libra in her third quarter, having continued visible for 14 diurnal rotations of the earth. Thus the poles are supplied one half of the Winter time with constant Moon-light, in the absence of the Sun, and only lose sight of the Moon from her third to her first quarter, while she gives but very little light, and could be but of little, and sometimes of no service to them. Interrogations for Section Ninth. What is understood by the MOON'S PHASES? What is discovered by observing the moon with a telescope? Of what use is the ruggedness to us? If the surface of the moon is uneven, why does it not so appear when viewed by the eye only ? What is the moon? What part of the moon do we discover? When is she said to be in conjunction with the Sun ? When she is in her first octant, how much of her enlightened side is visible? How much of her enlightened side does she show in her first quarter? When she has gone half around her orbit, how does she appear? How does she appear when viewed from the Sun ? Are the moon's motions faster or slower than the earth's, from her change to her first quarter? How far does she fall behind the earth? From her first quarter to her full, which moves with the greatest rapidity? Which from the full to her third quarter? Which from the third quarter to the change? Is the gravity of the moon at any time greater towards the Sun, than towards the earth, and at what time? How much greater is the quantity of matter in the Sun, than in the earth? In what proportion does the attraction of each body diminish? How far from the earth is the point of equal attraction between the earth and the Sun ? Why does not the moon leave the earth and go to the Sun ? What is understood by the Harvest Moon? How many minutes later at the equator does the moon rise every day, than on the preceding? Is there any material difference in high northern, of southern latitudes ? At what time in northern latitudes, does the full moon rise? How many days together does the moon in such cases rise at nearly the same time? What is the cause of this small difference? How far does the earth advance in her orbit, while the moon goes round the ecliptic? How many conjunctions and oppositions of the Sun and Moon can take place in any particular part of the ecliptic, in the course of a year? How many full Moons in the course of a year, that rise with so little difference near the time of Sunsetting? Does this singularity appear in southern latitudes, as well as in northern? Does the Moon's orbit lie exactly in the ecliptic? What is understood by the moon's nodes ? How many times from change to change, is the moon in her nodes? Which is called the ascending node? How many degrees are they asunder? How much does these nodes shift in the course of a year? Which way do they shift? In what length of time do they go around the ecliptic? How many degrees can the Sun go below the horizon of the poles? How many degrees must the Sun be below the horizon before the twilight is wholly gone ? Is the full moon in the Summer season ever seen at the north pole? Is it continually seen in Winter, from the first to her third quarter? Is it the same at the south pole? |