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rives at the first of Aries at that time. But when the full nearest the equinox happens any number of days before or after the 23d of September, her distance from that point at the full may be obtained with sufficient nearness, by taking a degree for each day between the full and the equinox, rejecting odd minutes both of time and motion. Compute the time of her arrival by her motion from the Sun. It will be found that the Moon is rarely more than one day's motion from the first of Aries at the time of the equinoctial full.

If the index be set at 12, when the first paper is brought to the horizon, and the other papers be brought in succession to that circle, the difference of time, when the Moon rises on the several nights, may be seen on the hour circle.

A more natural representation of the harvest Moon may be made by an artificial globe taken from the frame. Let a candle be placed on a stand, to represent the Sun. On a level with the candle, and a little distance to the west of it, let the globe be holden, the north pole so elevated as to form an angle of 23° 28′ with the horizon. Let a small taper be placed under the globe, to represent the Moon at her first quarter. Carried to the west of the globe, the taper may represent her at the full in Aries. Over the globe, it will show her situation at her last quarter. By turning the globe round, and observing when any place, as Washington, comes into the light of the taper in its different situations, the appearance of the Moon rising at that place may be represented. If, in its western position, the taper be moved slowly and circularly up, so that the arch moved may subtend an angle of 1250 at the globe, while the globe itself is turned once round on its axis, and continued in this manner for several rotations, nearly an exact resemblance of the harvest Moon may be presented.

When the Moon rises with the least angle, she sets with the greatest; and when she rises with the great

est, she sets with the least. In other words, when the time of day, in which she rises for successive evenings, differs the least, the time of day in which she sets differs the most. At the full, the time of rising on successive evenings, differs most about the vernal equinox.

In every revolution, the Moon passes through the same signs; but, except in autumn, her rising with the least angle or difference of time, always about the first of Aries, is seldom observed. She enters Aries, in

winter, about the first quarter, and, rising about midday, attracts no particular notice; about the change in spring, when, from nearness to the Sun, she is not visible; in summer, about the last quarter, and rising at or near midnight, is seldom observed.

The statement of Mr. Ferguson, respecting the rising of the Moon at the polar circles, is not strictly true. From the first quarter, when she rises about sunset at those circles, to nearly the last quarter, the Moon rises 3 m. 56 s. earlier in the day on each succeeding evening.

The Moon is seldom full exactly at the equinox. When it is not, the fulls immediately before and after that time, exhibit phenomena resembling the equinoctial full. The nearer any full is to the equinox, the more resemblance it bears to the harvest Moon; the nearest being generally so denominated, whether it happen before or after the equinox.

The same phenomena are exhibited by the Moon in south latitudes, but at opposite times of the year; the autumnal equinox of south latitude being coincident with the vernal of the north.

The circumstances of the harvest Moon are in some measure affected by the inclination of the Moon's orbit to the ecliptic. This inclination is about 5° 9'. Moving backward, her nodes perform a revolution in about 18 y. 224 d. The harvest Moon is most beneficial during half of this time; least beneficial during the other half; most, when her ascending node is in the first

degree of Aries; least, when her descending node is in that degree.

The full Moon, in summer, always runs low, but much lower in some years than in others. The running low seldom attracts particular notice, except when she is in that part of her orbit which is south of the ecliptic. The summer full Moon runs the lowest, when her latitude south is greatest; or she is 90° from her nodes. When the Moon is north of the ecliptic, she runs high at the winter fulls; highest, when she is farthest north, or 900 from her nodes. The full Moons of summer not only run low, but continue a short time above the horizon. But this is at the time when the length of the days makes moonlight of little utility. On the contrary, the full Moons of winter not only run high, but continue long above the horizon. This is at the season when the light of the Moon is peculiarly useful, guiding and cheering the lonely traveller in the dreary and protracted nights.

At the poles, the full Moon, being below the horizon, is not seen for nearly half the year. This is in summer, when, were the Moon to shine, her light, immerged in the continued splendor of the Sun, would be of no use. In winter, when, at the benighted polar regions, the light of the Moon is most beneficial, she shines from about the first to the third quarter. What claim can he have to rational being, who does not adImire and adore the wisdom and benevolence of Him, who not only "gave the Sun for a light by day," but "the Moon and Stars for a light by night!"

The years, when the harvest Moon is least, and when most beneficial, may be seen in the following table. L. stands over the columns least beneficial; M. over those most beneficial. In both the columns marked N., the harvest Moon is farthest north in the orbit; in those marked S., it is farthest south.

HARVEST MOON OF THE NINETEENTH CENTURY.

Years least beneficial.

N.

L.

S.

1806 1807 1808 1809 1810 1811 1812 1813 1814 1815
1825 1826 1827 1828 1829 1830 1831 1832 1833
1844 1845 1846 1847 1848 1849 1850 1851 1852

1862 1863 1864 1865 1866 1867 1868 1869 1870

1881 1882 1883 1884 1885 1886 1887 1888 1889
1899 1900

Years most beneficial.

S.

M.

N.

1801 1802 1803 1804 1805

1816 1817 1818 1819 1820 1821 1822 1823 1824
1834 1835 1836 1837 1838 1839 1840 1841 1842 1843
1853 1854 1855 1856 1857 1858 1859 1860 1861
1871 1872 1873 1874 1875 1876 1877 1878 1879 1880
1890 1891 1892 1893 1894 1895 1896 1897 1898

How far does the Moon move in a solar day? How much does the motion of the Moon exceed the apparent motion of the Sun ? At the equator, what is the difference in the time when the Moon rises on each succeeding night? In high latitudes, what have farmers observed respecting the rising of the autumnal full Moon? What is there remarkable in the Moon's rising at the polar circles? From what arise the phenomena of the harvest Moon? When is the harvest Moon? How would you illustrate the phenomena of the harvest Moon? What would give a very natural representation of this peculiarity in the Moon's rising? When there is the least difference in the time of the Moon's rising, how is her setting? As the Moon passes through the same signs in every revolution, why are not the phenomena of the harvest Moon observed at other seasons besides autumn? Why is not the statement of Mr. Ferguson respecting the Moon's rising at the polar circles, strictly true? When the Moon is not full exactly at the equinox, what fulls are

taken for the harvest Moon? When have the inhabitants of south latitude the phenomena of the harvest Moon? Does the inclination of the Moon's orbit to the ecliptic affect the phenomena of the harvest Moon? Is the motion of the Moon's nodes direct or retrograde? How long are they in performing a revolution? During what part of the time of their revolution is the harvest Moon most beneficial, and what part least beneficial? When does the full Moon run low? In what part of her orbit does it run lowest? How are the full Moons of winter? When do they run highest? Is the regulation of the high and low fulls calculated for our benefit? How long does the Moon shine in winter in the polar regions? Do the wisdom and benevolence of the Deity appear in the regulations of the Moon?

CHAPTER VII.

The Tides.

THE tides are the alternate ebbing and flowing of the sea. They are imperceptible in the midst of the ocean, and can only be known by the rising of the water on the adjacent land, or where the depth of water will admit of sounding.

Kepler was the first who discovered the true cause of the tides, and that the attraction of the Sun and Moon produced the constant flux and reflux of the water. But, a "hint being given, the immortal Sir Isaac Newton improved it, and wrote so amply on the subject, as to make the theory of the tides in a manner quite his own, by discovering the cause of their rising on the side of the Earth opposite to the Moon. Kepler believed that the presence of the Moon occasioned an impulse, which caused another in her absence."

For

The attraction of the Moon is the principal cause of the tides; but the attraction of the Sun operates to in

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