Ecliptic, 40.; its obliquity, 40.

Eclipses of the sun, 529-541.; of the moon, 520.-528.; of ju-
piter's satellites, 505.; limits, 523. 533.; periods of eclipses,
543.

Elevation of equator, 26.

Ellipsis, properties of, 279., &c.

Elliptical orbits, 262., &c.

Elongation, greatest, 259.

Epicycle, 204, 228.; epicycloid, 240.

Equation of the centre, 299.; greatest, 312, 322.

Equation of time, 113.; Dr. Maskelyne's investigation of, 117.
Equator, 15.; equinoctial, 17.

Equinoxes, 40.

Errour in sun's altitude given, to find the errour in time, 132.
Evans, Mr., his rule to find latitude at the centre, 659. Note.
Excentricity, 295. 304. 345.

Eye's true and imaginary place and orbit, 222.

F.

Fixed stars, 27. 58.; order and magnitude, 59.; changes, 74.;
right-ascensions, &c. 62.; distances, 683.-693.; number,
695.; motion, 699.; nature, 709.

Galaxy, 70. 695.

G.

Geocentric, longitude, 46.; latitude, 47.

Georgium sidus, 195.; discovered by Herschel, 378.; calculation
of its orbit, 378.-380.

Gravitation, 212. 282.

H.

Harvest moon, 479.

Heavens, scheme of, 166.

Heliacal rising and setting, 187.

Heliocentric longitude, 46.; latitude, 47.; conjunction, 416

Horizon, sensible and rational, 21.

Horizontal parallax, 83. 579.; moon, 483.-488.

Horoscope, 166.

Hour circles, 43.

, I. J.

Inclinations of the planets' orbits, 291. 356.

Informes, 69.

Irregularities of the moon, 420.-439.

Inferiour planets, 251.

Jupiter, 202.; his diameter, 387.; belts, 401.; rotation, 401.;
distance from the sun, 360.; period, 333.; excentricity of or-
bit, 345.; aphelion, 341.; node, 351.; satellites, 511.

K.

Kepler's elliptic theory and laws, 208. 209. 271. 284.; problem,
318.-323.

L.

Latitude, terrestrial, 19; to find, 648.-659.; celestial, 47.;
geocentric, 47.; heliocentric, 47. 371.; on the sphere reduced
to latitude on the spheroid, 552. 659. Note.

Laws of motion, &c. 262. 274.

Libration of the moon, 463.

Light, its motion, 509.; Aberration, 630. 646.

Line of the nodes, 290.; of the apsides, 296.

Long, Dr., his globe at Pembroke hall, 73. Note.

Longitude, terrestrial, 20.; to determine, 660.-680.; celestial,
46.; geocentric, 46.; heliocentric, 46. 368.; of the nonagesi-
mal degree, 155. Note.

Lunar mountains, 471.

'Magnitude of the planets, 389.

M.

Mars, 201.; his parallax, 91.; distance, 360.; period, 333.; dia-
meter, 387.; rotation, 400.; excentricity, 345.; node, 351.;
aphelion, 341.

Maskelyne, Dr. on transits, 576, &c.

Mean distance, 294.

Mercury, 200; his distance, 360.; period, 333.; diameter, 387.;
aphelion, 341.; excentricity, 345.; node, 351.

Meridian, 18.; line, to find, 33.

Midheaven, 175.

Milky way, 70.

Moon, 197.; her irregularities, 420.-439.; apsides, 450.; nodes,
446.; inclination of orbit, 449.; excentricity, 453.; distance,
457; magnitude, 461.; rotation, 462.; period, 440.; accele
ration. 444; parallax, 455; path always concave, 458.; age
and southing, 489.-494.; libration, 463.; shadow, 5:9;
phases, 467-469.; cusps, or horns, 470.; mountains and
maps, 472.; atmosphere, 478.

Morning and evening star, 406.

Motion apparent and relative, 221.; annual and secular, 334.

Nebulæ, 696.

Newtonian system, 211.-214.; rules of philosophising, 216.
Nodes, and line of nodes, 290.

Nonagesimal degree, 158. 470.

North latitude, 19.

Northern signs, 45.

Nutation, 645. Note.

0.

Oblique, sphere, 30. ; ascension, 44.

Occultations, 55.; of the fixed stars, 545-559.
Opposition, 202. 250. 328.

Optic orbit, 222.

P.

Parallax, 79.; to find, 89, &c.; of the moon, 455.; of the sun,
579,; equatoreal reduced to parallax on the spheroid, 553-
Parallel of latitude, 19.; parallel sphere, 28.

Parallelism of the earth's axis, 205.

Penumbra, 528.; its dimensions, 531.

Perigee, 297.; perihelion, 296.

Periods of the planets, 333.

Phases of Venus, 207. 403.

Piazzi's planet, 195. 382. Note.

Plane of comparison, 224.

Planets, 27. 194. ; opake bodies, 205.; probably inhabited, 701.;
move round the sun, 205.; orbits elliptical, 262.-287.; infe-
riour and superiour, 251.; direct retrograde, 254.-255.; sta-
tionary, 254. 255. 407.; altitudies, azimuths, &c. 418.
Poles, 13.; of the equator, 15.; of the heavens, 17.

Polar circles, 31.

Precession of the equinoxes, 57.

Prime vertical, 50.

Projection of the optic orbit, 223.

Problems, relative to the sun, 121.-153; to the stars, 168.—183.;

the earth, 301-325.

Ptolemaic system, 204.

Satellites, 207. 493-513.; of jupiter, 511.; eclipses of, 505.; of
saturn, 512.; of georgium sidus, 513.

Saturn, 202.; his diameter, 387.; belts, 402.; rotation, 402.;
distance, 360.; excentricity, 345.; period, 333.; aphelion,
341.; node, 351.; ring, 402. 514.

Secondary, 12.

Seasons, 52. 53.

Semidiurnal arc, 52.

Semitychonic system, 206.

Scheme of the heavens, 166.

Sidereal year, 56.

Signs of the zodiac, 45.

Simple elliptic hypothesis, 321.

Solstices, 48. 53. 302.

Solar system, sun, centre of, 219.

South, 50.; latitude, 19.; signs, 45.

Sphere, parallel, 28.; right, 29.; oblique, 30.

Stars:
: see Fixed.

Sun, his apparent motion, 37.; real motion, 219.; meridian alu-
tude, 35.; rising and setting, 121.; magnitude, 389.; rota-
tion, 396.; distance, 325.; spots, 207, 397.; nature, 397.
Superior planets, 251.

Systems, 203.

T.

Telescopes, 207. 495. 580.

Time, mean, apparent, equation of, 113.
Theory of apparent motions, 220.-261.
Transits of Venus and Mercury, 562-578.

Two summers and two winters at the equator, 53.
Tychonic system, 206.

V.

Venus, 199.; distance, 360.; period, 333.; diameter, 387.; rota-
tion, 399.; excentricity, 345; aphelion, 341.; node, 351.;
greatest elongation, 259.; greatest brilliancy, 405.

Velocity of light, 509.

Vernal equinox, 52.

Vertical circles, 22.

W.

West, 50.

Wire of a telescope, time in which the sun passes over it, 152.
Wilson, Mr., his mode of ascertaining whether the centre of the so-
lar system be in motion, 646.

Y.

Year, tropical, 54; sidereal, 55.; anomalistic, 316,