Bissextile, or leap year, is a year consisting of 366 days, which happens every fourth year.

Bootes, a northern constellation, containing fifty-four

stars.

Boreal Signs, are those on the north side of the equator, viz. Aries, Taurus, Gemini, Cancer, Leo and Virgo.

C.

Cancer, the Crab, one of the constellations of the Zodiac: when the Sun enters this sign it has its greatest north declination; it contains 83 stars.

Canis Major, or the Great Dog, is a southern constellation that contains Sirius, one of the brightest fixed stars in the heavens: the number of stars in this constellation is thirty-one.

Cardinal points, are the north, south, east and west points of the horizon.

Cassiopeia, a northern constellation, consisting of fiftyfive stars.

Centrifugal Force, is that force by which all bodies moving about a central body or force, endeavour to fly off in tangent lines.

Centripetal Force, is that by which a body moving round another, tends towards it; this, and the centrifugal force acting upon the planets, cause them to describe curvilinear orbits about the sun.

Ceres, a primary planet, moving between the orbits of Mars and Jupiter. It was discovered on the first of January, 1801, by M. Piazzi.

Conjunction of two celestial bodies, is when they have the same degree of longitude.

Consequentia, in astronomy, is when the planets move according to the order of the signs.

Constellation, is a number of stars contained within some assumed figure.

Culmination, the transit or passage of a star over the meridian.

Cycle, a certain period of time in which the same revolutions begin again.

Cycle of the Moon, or the Lunar Cycle, is a period of 19 years, in which the new and full Moons return on the same days as they did nineteen years before: this Cycle is called the Golden Number.

Cycle of the Sun, is a period of 28 years, in which time the days of the month return again to the same days of the week.

D.

Day Astronomical. The astronomical day begins at apparent noon, and is counted twenty-four hours to the following noon.

Declination, is the distance of the Sun, Moon or stars from the equinoctial, either north or south. Degree, the thirtieth part of a sign.

Descending Node, is that point of a planet's orbit where it cuts the ecliptic proceeding southward.

Dial, an instrument to show the hour of the day by the Sun.

Digit, the twelfth part of the Sun's or Moon's diameter, and is used to show the degree of obscuration in an eclipse

Disk, is the face of the Sun or Moon as it appears to the eye.

Disk of the earth, is the difference between the horizontal parallax of the Sun and Moon, and is used in the protraction of solar eclipses.

Diurnal Arc, is the arc described by the celestial bodies from their rising to their setting.

Diurnal Motion, is the degrees, minutes, or seconds a celestial body describes in twenty-four hours.

E.

Earth, one of the planets. Its orbit lies between Venus and Mars.

Eclipse, a privation of the light of the Sun or Moon by the interposition of some opaque body.

Ecliptic, the orbit of the earth in performing her revolution round the Sun. It is inclined to the equator, or equinoctial, at an angle of twenty-three degrees and twenty-eight minutes.

Elements, in Astronomy, are those principles deduced from observation, by which tables of the planetary motions are computed.

Ephemeris Tables, containing the computations of the places of the heavenly bodies for every day at noon.

Equinoctial in the heavens, or equator on the earth, is one of the great circles of the sphere whose poles are the poles of the world.

Eccentricity, is the distance of the centre from the foci of the elliptical orbit of the planet.

F.

Fixed Stars, are such as do not appear to change their relative situations.

Fomalhaut, a fixed star of the first magnitude, in the mouth of the southern fish.

G.

Galaxy, is that whitish track which appears to encompass the heavens.

Gemini, a constellation of the Zodiac in the northern hemisphere, containing eighty-five stars.

Geocentric place of a planet, is its place as seen from the earth.

Geocentric Latitude of a planet, is its perpendicular distance from the ecliptic as seen from the earth.

Geocentric Longitude of a planet, is its elliptical distance from the first point of Aries as seen from the earth.

H.

Halo, a very conspicuous circle of about 45 degrees in diameter, surrounding the Sun or Moon, supposed to arise from the refraction of light in passing through the thin vapours of the atmosphere.

Heliocentric place of a planet, is its latitude and longitude, or place in the heavens as seen from the Sun. The heliocentric motion of a planet is always direct, the Sun being its centre of motion.

Hemisphere, is the half of a globe or sphere divided by a plane passing through its centre.

Hercules, a northern constellation, containing one hundred and thirteen stars.

Horizon, is a great circle of the sphere, where the sight appears to be confined.

Horizontal Parallax, is the parallax of a celestial body when in the horizon, (see Parallax.)

Hydra, a constellation of the southern hemisphere, containing 60 stars.

I.

Inclination, of the orbit of a planet, is the angle which the plane of the planet's orbit makes with the plane of the ecliptic or earth's orbit.

Ingress, is the Sun's entering any of the twelve signs or other parts of the ecliptic.

J.

Julian year, is the year established by Julius Cæsar, now called the old style.

Juno, one of the newly discovered planets, and the sixth in order from the Sun.

Jupiter, one of the superior planets, and the largest in the Solar System.

L.

Leo, the Lion, a northern constellation of the Zodiac, containing ninety-five stars.

Libra, the Balance, a constellation of the Zodiac, containing fifty-one stars.

Limit of a planet, signifies its greatest heliocentric latitude.

Longitude of a celestial body, is the distance of that point of the ecliptic cut by a secondary to it, passing through the body from the beginning of Aries.

Μ.

Magnitudes. The fixed stars, according to their size or brightness, are divided into magnitudes. The brightest are called stars of the first magnitude; the next in brightness, stars of the second magnitude; and so on to the sixth or seventh magnitude; which are the smallest that can be seen with the naked eye.

Mars, a superior planet, and the fourth in order from the Sun.

Mean Anomaly of a planet, is its angular distance from the aphelion or perihelion, supposing it to revolve in a circle with its mean velocity.

Mean conjunction of the Sun and Moon, is the conjunction of their mean longitudes.

Mean distance of a planet is the semi-transverse diameter of its orbit.

Mercury, an inferior planet, the nearest to the Sun. Mid-heaven, called also Medum Cæli, is that point or degree of the ecliptic which is upon the meridian at any time.

Moon, the satellite of the earth, and which is nearest to the earth of all the heavenly bodies.

Ν.

Nadir, is that point in the heavens directly under our feet.

Nebulæ, is a term applied to those telescopic stars that have a cloudy appearance.

Nutation of the earth's axis, is a kind of vibratory motion, by which its inclination to the plane of the ecliptic is subject to a small variation.

0.

Oblique Ascension, is that point of the equinoctial which rises with a celestial body in an oblique sphere. Oblique Descension, is that point of the equinoctial which sets with a celestial body in an oblique sphere. Oblique Sphere, is that position of the sphere in which the equator and its parallels cut the horizon obliquely. Observatory, a place or building fitted up with proper instruments for observing celestial bodies.