Arthur Snow.
Answer.—As the plane of the earth’s orbit crosses the equator at an angle of about 23½ degrees, the attractive force of the sun, moon, and planets, constantly exerted upon the earth, has a tendency to tilt the pole away from the sun and to draw the equator toward it. As a consequence, the sun crosses the equator each time a little farther west than the point where it crossed the last time preceding, and where it would have crossed on its return if there were no disturbing force. Originally it was said that the equinoctial point, or place of crossing, went forward to meet the sun, and hence this phenomenon was called the precession of the equinoxes. But, from the fact that the equinoctial point really falls backwards on the celestial equator, toward the west, each time about 50 seconds of a degree, it is now very frequently termed the recession of the equinoxes. In consequence of this recession the seasons begin a little earlier each year, and it is estimated that in 12,800 years they will be reversed, our summer occurring when the sun is in the constellation that he now traverses in winter time. It requires about 25,000 years for the sun to complete one circuit of precession of the equinoxes.
COMET OF 1812 AND 1813.
Lake Forest, Ill.
Is it true that the comet now coming into view is the same as the one of 1812? When will it become plainly visible to the naked eye, and when will it be nearest the sun?
Star-gazer.
Answer.—It is generally admitted that the comet discovered by Professor Brooks on the 5th of September last, and now visible, with the aid of a good opera or field glass, in the constellation Draco, between the “Great Dipper,” in Ursa Major, and the “Northern Cross,” in the Constellation Cygnus, is identical with the comet of 1812, which was believed by the superstitious to prognosticate our last war with Great Britain. It will reach perihelion, or the point in its orbit nearest the sun, Jan. 25. It will increase in brightness rapidly from the first of December, and be plainly visible to the naked eye by the middle of that month. At its brightest it will be brighter than in 1812, but it will not equal at any time the magnificent comet of 1882. The period, as calculated in 1812, was 70.6 years. As the interval between its perihelion time, Sept. 15, 1812, and its perihelion passage, Jan. 25, 1884, will be but 71.5 years, it is not strange astronomers—considering the imperfections of astronomical science and art then as compared with the state of astronomy now—are not surprised at this small error in this comet’s calculated orbital period.
LONGEVITY OF THE CIRCASSIAN RACE.