spherical, but become more elevated at its equator and most depressed at its poles; because, the particles of matter near its equator, would have the most centrifugal force, and those near its poles, the least. The degree of velocity, in its equatorial motion, joined to its density, would determine the degree in which it would become spheroidal. We might expect, therefore, that Saturn would be more flattened at its poles than Jupiter, this last, more than the Earth, and Mercury still less. Observation confirms this theory. It is not necessary to suppose, that the planets hare acquired their spheroidal forms by long rotation on their axes, any more than it is needful to suppose, that the first oak or the first acorn, were as long in acquiring their specific forms as their successors. We choose rather to believe, that the Creator launched the planets into the heavens with essentially the same forms. which laws then inscribed upon them, are adapted to perpe tuate. In one part of the orbit of Saturn, the Sun is 30 degrees north of its equator. The squares of the distance, between the Sun and the rings of Saturn, are less, than between the Sun and the planet itself; consequently, those rings will be attracted north, and the Sun in passing to the southern hemisphere, will be vertical over the centre of the rings, sooner than over the Equator of Saturn. Similar effects, will attend the Sun's influence in the opposite hemisphere. These remarks, will aid in the illustra tion of phenomena in the heavens, resulting from the same cause, in its operation on the spheroidal form of the Earth. To render this subject intelligible, there is occasion to describe an imaginary belt in the heavens. If its matter could easily change its position, what form would it take? What causes are to be considered in producing a spheroidal figure? Which of the planets is most spheroidal? Is it necessary to suppose the planets have acquired their form from their rotation? Why not? How broad is the torrid zone in Saturn? What influence will the Sun's variation north and south have on the position of the rings ?-and on the Equator? THE ZODIAC. THE Sun's apparent annual path, and the real orbit of the Earth among the stars, is in the Ecliptic, an imaginary line, in the centre of a zone in the heavens, called the ZODIAC. This zone is 16° broad, contains the orbits of all the planets except 3 of the Asteroids, and is divided into 12 equal parts, called the 12 signs of the Zodiac. The names, and characters, of the 12 signs, with the time of the Sun's entrance into them, are as follow: 1. Aries, Y, or the Ram; March 20th. 6. Virgo, m, the Virgin; August 23d. The first six, are called northern signs, lying on the north side of the Equator; and the last six southern, lying on the south side. The signs VS,~~~, ✈, Y, 8, II, are called ascending, because the Sun approaches our north pole, while it passes through them; and , S, M, ≈, m, f, are called descending, the Sun receding from our pole, as it passes through them. What is the Zodiac? How broad? How many signs in it? Which signs are called northern? Which southern? Which ascending? Which descending? PRECESSION OF THE EQUINOXES. THE number, and the names of these signs, will be recognized at once, as the same with the constellations of the Zodiac. They, doubtless, had a common origin, and their places were together more than 2000 years ago; but they now vary more than 30°. Where the Sun's place among the stars, is the 20th of March, or the vernal equinox, is called the beginning of the sign Aries. If the Sun and Moon were always over the Equator, the solar, and the siderial year, would be, alike. When the Sun is at the summer solstice, his attraction on the elevated matter of the Earth at its Equator, being greater than if it were a perfect sphere, affects the position of this planet, to make the Sun cross the Equator, at the autumnal equinox, sooner than it would otherwise do. A similar effect, is produced in the southern hemisphere, in our winter. The attraction at the south, makes the vernal equinox occur sooner. The arrival of the Sun, at the vernal equinox, precedes its complete apparent revolution in the Ecliptic, by 50" of a degree, or 20' of time. Hence, it is called the PRECESSION OF THE EQUINOXES. In about 26 thousand years, the Sun's place among the stars, at the vernal equinox, will have advanced from west to east, quite round the heavens, carrying the signs with it. When had the signs and constellations of the zodiac a common location? How much do they now vary? How is the beginning of the sign Aries reckoned? When the Sun is at the summer solstice, what fect has it on the elevated matter at the Equator? What effect when at the winter solstice? How much does the vernal equin each year PRECEDE the arrival of the Sun at the same point of the Ecliptic? What is the length of the great celestial period The constellations of the Zodiac, remain immoveable, and while the sign Aries is 50 seconds each year farther east, it is obvious, that it will be advancing through the stars of Pisces and Aquarius quite round the Zodiac. As the Moon revolves near the plane of the Ecliptic, it will exert a similar influence, which affects the return of the equinoxes. NEW STYLE. HERE, we may consider the difference between a siderial, a solar, and a Julian year. A siderial year is the time required for the Sun to perform a complete revolution in the ecliptic; which is 365d. 6h. 9 and 11". The solar or tropical year is from one vernal equinox to another; which is 365d. 5h. 48′ and 48". A Julian, or civil year, is either 365 or 366 days. To reckon time by Julian years, one day is added to February every fourth year; which is called Bissextile, or Leap year. This being about 11 minutes longer than the solar year, would gradually change the times, both of the equinoxes, and the solstices. Pope Gregory XIII. reformed the calendar, and in 1752, the British Parliament introduced NEW STYLE, into England and all her colonies, by calling the 2d of September, the 13th of September, and changing the beginning of the year from the 24th of March, to the 1st of January. This will explain the reason, why some years in history, directly after the adoption of New Style, were written January, 1757-8. According to Old Style 57; to New 58. While 11 days were thrown out of the calender, it was determined, that the first leap year in each What other cause is affecting the return of the equinoxes? What is the difference between a siderial year, solar year, and a Julian year? What is NEW STYLE? When adopted by the English? What measure is to be adopted to keep the vernal equinox from variation? century, for three centuries in four, should be thrown out; or called a common year. This mode of reckoning, will prevent the vernal equinox from varying, one day, in twenty thousand years. DOMINICAL LETTER. The first 7 letters of the alphabet are commonly placed in the annual almanacs, to show on what days of the week the days of the months fall throughout the year. And because one of those 7 letters must necessarily stand against Sunday, it is printed in a capital form, and called the Dominical letter: the other six are changed to figures. When January begins on Sunday, A is the Dominical, or Sunday letter. If it begins on Monday, B is the Dominical letter. If on Tuesday, C, &c. till the series of letters of the alphabet are used answering to the same days of the week. Suppose the Dominical letter be required for the year of Christ 1835, new style, I look for 1800 at the head cr the Dominical letter table, on the next page, and for 35 at the left hand of the same table; and in the angle of meeting, I find F, which is the Dominical letter for that year. There are always two Dominical letters to the leap-year, the first of which is used till the 24th of February, the last for the following part of the year. How can the Dominical letter be found for any given year? |