Lagging of tides, 753.
Lagrange, his theorems respecting the stability of the planetary system, 669. 639.701.
Laplace accounts for the secular accele- ration of the moon, 740. Lassell, his discovery of the satellite of Neptune, 524. Of an eighth satellite of Saturn, Appendix. Re-discovers two of the satellites of Uranus, 551. Latitude, terrestrial, 88. Parallels of, 89. How ascertained, 119. 129. Rö- mer's mode of obtaining, 248. On a spheroid, 247. Celestial, 308. He- liocentric, how calculated, 500. Geo- centric, 503.
Laws of nature how arrived at, 139. Subordinate, appear first in form of errors, 139. Kepler's, 352. 487... Level, spirit, 176. Sea, 285. Strata, 287. Leverrier, 506, 507. 767. Lexell, comet of, 585.
Libration of the moon, 435. Of ap- - sides, 694.
Light, aberration of, 331. Velocity of, 331. How ascertained, 545. Equa- tion of, 335. Extinction of, in tra- versing space, 798. Distance mea- sured by its motion, 802... Of certain stars compared with the sun, 817... Effect of its motion in altering appa- rent period of a double star, 863. Zodiacal, 897.
Magellanic clouds, 892... Magnitudes of stars, 780... and photometric scales of, 780... And Appendix.
Maps, geographical, construction of, 273. Celestial, 290... Of the moon, 437. Mars, phases of, 484. Gravity on sur- face, 508. Continents and seas of, 510. Elements (Appendix). Masses of planets determined by their satellites, 532. By their mutual perturbations, 757. Of Jupiter's satellites, 758. Of the moon, 759. Menstrual equation, 528. Mercator's projections, 283. Mercury, synodic revolution of, 472. Velocity in orbits, 474. Stationary points of, 476. Phases, 477. Greatest elongations, 482. Transits of, 483. Heat received from sun, 508. Phy sical appearance and description, 509 Elements of (Appendix).
Meridian, terrestrial, 85. Celestial, 101. Line, 87. 190. Circle, 174. Mark, 190. Arc, how measured, 213. Arcs, lengths of, in various latitudes, 216. Messier, his catalogue of nebulæ, 865. Meteors, 898. Periodical, 900... Heights of, 904.
Metis, discovery of, 505. Micrometers, 199...
Milky way. (See Galaxy, 302.) Mimas, 550., and note. Mira Ceti, 820.
Moon, her motion among the stars, 401. Distance of, 403. Magnitude and horizontal parallax, 404. Augmen- tation, 404. Her orbit, 405. Revo- lution of nodes, 407. Apsides, 409. Occultation of stars by, 414. Phases of, 416. Brightness of surface, 417.,
Nabonassar, era of, 926. Nadir, 99.
Nebula, classifications of, 868.879., note.
Law of distribution, 868. Resolvable, 870. Elliptic, 873. Of Andromeda, 874. Annular, 875. Planetary, 876. Coloured, ib. Double, 878. Of sub- regular forms, 881, 882. Irregular, 883. Of Orion, 885. Of Argo, 887. Of Sagittarius, 888. Of Cygnus, 891. Nebular hypothesis, 872. Nebulous matter, 871. Stars, 880. Neptune, discovery of, 506. 768. Per- turbations produced on Uranus by, analysed, 765... Place indicated by theory, 767. Elements of, 771... Per- turbing forces of, on Uranus, geo- metrically exhibited, 773. Their effects, 774... Newton, his theory of gravitation, 490... et passim.
Nodes of the sun's equator,_390.
the moon's orbit, 407. Passage of planets through, 460. Of planetary orbits, 495. Perturbation of, 620... Criterion of their advance or recess, 622. Recede on the disturbing orbit, 624... Motion of the moon's theory of, 638. Analogy of their variations to those of perihelia, 699.
Obliquity of ecliptic, 303. Produces the variations of season, 362. Slowly diminishing, and why, 640. Observation, astronomical, its peculiari- ties, 138.
Occultation, perpetual, circle of, 113. Of a star by the moon, 413... Of Ju- piter's satellites by the body, 541. Of Saturn's, 549.
Olbers discovers Pallas and Vesta, 505. His hypothesis of the partial opacity of space, 798.
Opacity, partial, of space, 798. Oscillations, forced, principle of, 650. Orbits of planets, their elements (Ap- pendix) of double stars, 843. Of comets. (See comets.) Orthogonal disturbing force, and its effects, 616. 619. Orthographic projection, 280.
Perihelia and excentricities, theory of, |
670... Perihelion, 368. Passage, 496. comets in, 592. Period, Julian, 924. Of planets (App.). Periodic time of a body revolving at the earth's surface, 442. Of planets, how ascertained, 486. Law of, 48. Of a disturbed planet permanently altered, 734...
Longitude of, 495. Heat endured by
Periodical stars, 820... List of, 825. Perspective, celestial, 114. Perturbations, 602...
Peters, his researches on parallax, 815. Phases of the moon explained, 416. Mercury and Venus, 465. 477. superior planets, 484. Photometric scale of star magnitudes, 780. Piazzi discovers Ceres, 505. Pigott, variable stars discovered by, 824...
Places, mean and true, 374. Geometric and heliocentric, 371. 497. Planetary nebulæ, 876... Planets, 456. Zodiacal and ultra-zo- diacal, 457. Apparent motions, 459. Stations and retrogradations, 459. Reference to sun as their center, 462. Community of nature with the earth, 463. Apparent diameters of, 464. Phases of, 465. Inferior and superior, 467. Transits of (See Transit) Mo- tions explained, 468. Distances, how concluded, 471. Periods, how found, 472. Synodical revolution, 472. Superior, their stations and retrogra- dations, 485. Magnitude of orbits, how concluded, 485. Elements of, 495. (See Appendix for Synoptic Table.) Densities, 508. Physical peculiarities, &c., 509... Illustration of their relative sizes and distances, 526. Plantamour, his calculations respecting the double comet of Biela, 583. Pleiades, 865. Assigned by Mädler as the central point of the sidereal system, 861.
Plumb-line, direction of, 23. Use of, in observation, 175.
Polar distance, 105. Point, on a mural circle, 170. 172. Poles, 83. Of ecliptic, 307. Pole-star, 59. Useful for finding the latitude, 171. Not always the same, 318. What, at epoch of the building of the pyramids, 319. Pores of the sun's surface, 387. Position, angle of, 204. Micrometer, ib.
Precession of the equinoxes, 312 In what consisting, 314... Effects, 313. Physical explanation, 642... Præsepe, Cancri, 865.
Priming and lagging of tides, 753. Principle of areas, 490. Of forced vibrations, 650. Of repetition, 198. Of conservation of vis viva, 663. Of collimation, 178.
Problem of three bodies, 608. Problems in plane astronomy, 127... 309...
Projection of a star on the moon's limb, 414., note.
Projections of the sphere, 280... Proper motions of the stars, 852. Of the sun, 853. Pyramids, 319.
Radial disturbing force, 615... Radiation, solar, on planets, 508. On comets, 592.
Rate of clock, how obtained, 293. Reading off, methods of, 165. Reflexion, observations by, 173. Refraction, 38. Astronomical and its effects, 39, 40. Measure of, and law of variation, 43. How detected by observation, 142. Terrestrial, 44. How best investigated, 191. Repetition, principle of, 198. Resistance of ether, 577. Retrogradations of planets, 459. nodes. (See Nodes.) Rhea, 548., note.
Right ascension, 108. How determined,
Rings of Saturn, dimensions of, 514.
Phenomena of their disappearance, 515...Equilibrium of, 518...Multiple, 521, and Appendix. Appearance of from Saturn, 522. Attraction of on a point within, 735., note. Rittenhouse, his principle of collimation,
Rosse, Earl of, his great reflector, 870. 882.
Rotation, diurnal, 58. Parallactic, 68. Of planets, 509... Of Jupiter, 512. Of fixed stars on their axes, 820.
Saros, 426. Satellites, of Jupiter, 511. Of Saturn, 518. 547. Discovery of an eighth (Appendix). Of Uranus, 523. 552. Of Neptune, 524. 553. Used to deter- mine masses of their primaries, 532.
Obey Kepler's laws, 533. Eclipses of Jupiter's, 535... Other phænomena of, 540. Their dimensions and masses, 540. Discovery, 544. Ve- locity of light ascertained from, 545. Saturn, remarkable deficiency of density, 508. Rings of, 514. Physical de- scription of, 514. Satellites of, 547. and Appendix. (See also elements in Appendix.)
Sea, proportion of its depth to radius of the globe, 31. Its action in mo- delling the external form of the earth, 227.
Seasons explained, 362... Temperature of, 366.
Sector, zenith, 192.
Secular variations, 655.
Shadow, dimensions of the earth's, 422. 428. Cast by Venus, 467.
piter's satellites seen on disc, 540. Shooting stars used for finding longi- tudes, 265. Periodical, 900. (See Meteors.
Sidereal time, 110. 910. Year. (See Year.) Day. (See Day.)
Signs of zodiac, 380.
Sirius, its parallax and absolute light,
Sphere, 95. Projections of, 280. traction of, 735., note. Spheroidal form of Earth (see Earth) produces inequalities in the moon's motion, 749. Spots on Sun, 389...
distribution of stars, 793. Discovery Ca- of parallax of a Lyræ, 813. talogue and observation of double stars, 835.
Struve, Otto, his researches on proper motions, 854.
great size on Apparent mo- Orbit elliptic,
Style, old and new, 932. Sun, oval shape and horizon explained, 47. tion not uniform, 34. 349. Greatest and least distances, 350. Actual distance, 357. Mag- nitude, 358. Rotation on axis, 359. 390. Mass, 360. Physical consti- tution, 386. Spots, ib.... Situation of its equator, 390... Maculiferous zones of, 393. Atmosphere, 395. Tempe- rature, 396. Expenditure of heat, 397. Eclipses, 420. Density of, 447. Natural center of planetary system, 462. Distance, how determined, 479. Its size illustrated, 526. Action in producing tides, 751. Proper motion of, 854... Absolute velocity of in space,
858. Central, speculations on, 861. Sunsets, two, witnessed in one day, 26. Survey, trigonometrical nature of, 274. Synodic revolution, 418. Of sun and moon, ib.
At-Tangential force and its effects, 618. Momentary action on perihelia, 673. Wholly influential on velocity, 660. Produces variations of axis, ib. ... Doubles the rate of advance of lunar apsides, 686. Of Neptune on Uranus, and its effects, 774. Telescope, 154. Its application to as- tronomical instruments, 117. Telescopic sights, invention of, 158., note. Temperature of earth's surface at diffe- rent seasons, 366. In South Africa and Australia, 369. Of the sun, 396. Tethys, 548, note. Theodolite, 192. Its use in surveying, 276.
Stars, visible by day, 61. Fixed, 777... Their apparent magnitudes, 778... Comparison by an astrometer, 783. Law of distribution over heavens, 785... alike in either hemisphere, 794. Parallax of certain, 815. Discs of, 816. Real size and absolute light. 817. Periodical, 820... Temporary, 827. Irregular, 830. Missing, 832. Double, 833... Coloured, 851., and note. Proper motions of, 852. Ir- regularities in motions not verified, 859. Clusters of, 864... Nebulous, 879... Nebulous-double, 880. Stationary points of planets, 459. How determined, 475. Of Mercury and Venus, 476.
Stereographic projection, 281. Stones, meteoric, 898. Great shower of, ib.
Struve, his researches on the law of
Theory of instrumental errors, 141. Of gravitation 490... Of nebulous subsi-
dence and sidereal aggregation, 872. Tides, a system of forced oscillations, 651. Explained, 750... Priming and lagging of, 753. Periodical inequal- ities of, 755. Instances of very high,
and secular, 655. Incident on the epoch, 731.
Velocity, angular, of sun not uniform, 350. Linear, of sun not uniform, 351. Of planets, Mercury, Venus, and Earth, 474. Of light, 545. Of shooting stars, 899. 904.
Venus, synodic revolution of, 472. Sta- tionary points, 476. Velocity of, 474. Phases, 477. Point of greatest bright- ness, 478. Transits of, 479. Phy- sical description and appearance, 509. Inequality in earth's motion pro- duced by, 726. In that of the moon, 743... Vernier, 97.
Vertical, prime, 102. Circles, 100. Vesta, discovery of, 505.
Weight of bodies in different latitudes, 322. Of a body on the moon, 508. On the sun, 450. Winds, trade, 240...
Year, sidereal, 305.
Tropical, 383. Anomalistic, 384., and day incom- mensurable, 913. Leap, 914. Of confusion, 917. Beginning of, in England changed, 932.
Vanishing point of parallel lines, 116. Zenith, 99. Sector, 192.
Line of parallel planes, 117. Variation of the moon explained, 705... Variations of elements, 653. Periodical
Zodiac, 305.
Zodiacal light, 899.
Zones of climate and latitude, 382.
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