These bodies are supposed to revolve on axes in the same time as their revolution around the planet.

The eighth satellite is supposed to be about as large as Mars, and the remainder to be sinaller, according to their respective distances. They are supposed to have a rotation on axes, in the same time as they revolve around the planet.

Their motion is retrograde, and their orbits are nearly circles.

GLOSSARY OF ASTRONOMICAL TERMS,

WITH THEIR DERIVATIONS.

ALTITUDE-Lat. Altitudo, height. The height of a heavenly body above the horizon.

AMPLITUDE-Lat. Amplitudo, largeness. The distance of a heavenly body from the east or west points of the horizon. ANNULAR-Lat. Annulus, a ring. A term applied to an eclipse, in which the sun's disc looks like a ring.

ANTIPODES-Gr. Anti, against, and podes, feet. Those inhabitants of the earth, who live on exactly opposite sides of the earth, or feet to feet.

ANTOECI—Gr. Anti, against, and oikos, a house. Those whose dwellings are on opposite sides of the equator, but under the same meridian.

ARCTIC-Gr. Arktos, a bear. The name of the circle in the vicinity of the Constellation of the Bear.

ANTARCTIC-Gr. Anti, against, and arktos. The circle opposite the Arctic circle.

APHELION-Gr. Apo, from, and helios, the sun. The point of the earth's orbit farthest from the sun.

APOGEE Gr. Apo and ge, the earth. The point of the moon's orbit farthest from the earth.

APSIS-Gr. Apsis, a joining. The aphelion or perihelion of a planet's orbit.

APSIDES Plural of apsis.

ASTRONOMY-Gr. Astron, a star, and nemo, to classify. The science which classifies and describes the heavenly bodies. ASTEROIDS-Gr. Aster, a star, and eido, to resemble. Small planets between Mars and Jupiter, at first taken for stars.

ATMOSPHERE-Gr. Atmos, vapor, and sphæra, a sphere. The body of air, vapor, &c., which encompasses the earth.

AZIMUTH-Arabic. The distance of a body from the north or south points of the horizon.

ASTRAL-Gr. Aster, a star. Relating to the stars.

Axis, pl. Axes-Lat. Axis, an axle. The imaginary line on which the earth turns.

ALMACANTARS-Arabic. Parallels of altitude.

BINARY-Lat. Binus, two by two. A term applied to systems of double stars.

CULMINATE-Lat. Culmen, the top. To pass the meridian, because then it arrives at its greatest altitude. CREPUSCULUM-Lat. Twilight.

CUSPS-Lat. Cuspis, a point. The points of the moon's disc, when horned.

The force

CENTRIPETAL-Lat. Centrum, a centre, and peto, to seek. The force which urges a body towards the centre of motion. CENTRIFUGAL-Lat. Centrum and fugio, to flee from. by which a body recedes from the centre of motion. COMET-Lat. Coma, hair. A body surrounded by a nebulous appearance, resembling hair.

CONJUNCTION-Lat. Con, together, and jungo, to join. The apparent meeting of a planet with the sun.

CONSTELLATION-Lat. Con, together, and stella, a star. A group of stars.

CARDINAL-Lat. Cardo, a hinge. The term applied to the four principal points of the compass.

CONCENTRIC-Lat. Con, together, and centrum, a centre. Concentric circles are those drawn around the same centre.

DISC-Lat. Discus, a quoit. The circular face of a heavenly body. DIAMETER-Gr. Dia, through, and metron, a measure. The line which measures across a circle.

DIGIT-Lat. Digitus, a finger. One of the twelve equal divisions of the diameter of the disc.

ECLIPSE-Gr. Ekleipsis, a fainting away. The concealment of one heavenly body by the interposition of another.

ECLIPTIC-From Eclipse, a great circle in the heavens, so called because eclipses only take place when the moon is in its plane. ECCENTRICITY-Gr. Ec, from, and centron, a centre. Distance from the centre.

ELONGATION-Lat. Longus, long. The angular distance of a planet from the sun.

EQUATOR-Lat. Equo, to divide equally. The great circle which divides the earth into northern and southern hemispheres. · EQUINOCTIAL-Lat. Æquus, equal, and noctes, nights. A great circle in the heavens, so called, because when the sun is in it, every place on the earth has equal days and nights.

FOCUS-Lat. Focus, a fire-place.

orbit where the sun is situated.

The point within the earth's (Plural foci.)

GALAXY-Gr. Galaxias, the milky-way. Lat. Via Lactea. GIBBOUS-Lat. Gibbus, convex. Term applied to the partial disc of the moon, or a planet, when more than half is visible.

GEOCENTRIO-Gr. ge, the earth, and centron, a centre. Seen from the earth as a centre.

HORIZON-Gr. Horizo, to bound. The circle which bounds our vision.

HELIOCENTRIC-Gr. Helios, the sun, and centron, a centre. Seen from the sun as a centre.

MERIDIAN-Lat. Meridies, mid-day. The circle at which the sun arrives when it is noon.

NADIR-Arabic, Nazeer, opposite. The point opposite the zenith. NEBULA-Lat. Nebula, a cloud. A cloudy appearance among the

stars.

NITROGEN-Gr. Nitron, nitre, and gennao, to produce. One of the two component gases of air.

NODES-Lat. Nodus, a knot. The points at which the orbit of a planet intersects the ecliptic, or plane of the earth's orbit.