the longitude of the perihelion; and
Tis the time of perihelion passage;
that of the ascending node for the epoch of the perihelion;
4, the inclination to the ecliptic; a, the semi-axis; e, the excentricity; P, the period in days.
N. B. The reader will find a complete list of elements of all known comets up to June, 1847, by all their several computors, in Prof. Encke's edition of Olbers's Abhandlung über die leichteste und bequemste Methode die Bahn eines Cometen zu berechnen." The list is compiled by Dr. Galle. It contains orbits of 178 distinct comets. From an examination of these orbits we collect the following, as a more correct statement of cometary statistics than that in art. 601. viz.:- Retrograde comets under 10° inclination, 3 out of 15; under 20o, 9 out of 29. Retrograde comets, moving in orbits sensibly elliptic, under 170 inclination, 0 out of 9. In such orbits, of all inclinations from 0 to 90°, 11 out of 37. Thus we see that the induction of that article is materially strengthened by the enlarged field of comparison.
N.B. The references are to the articles, not to the pages.
attached to a reference number indicates that the reference extends to the article cited, and several subsequent in succession.
Acceleration, secular, of moon's mean Argo, nebulæ in, 887. Irregular star ʼn
in constellation, 830.
Ascension, right, 108. (See Right ascen- sion.)
Asteroids, their existence suspected pre- vious to their discovery, 505. Ap- pearance in telescopes, 525. Gravity on surface of, 525. Elements, Appen- dix, Synoptic Table. Astræa, discovery of, 505. Astrometer, 783, 784. Astronomy. Etymology, 11. General notions, 11.
Atmosphere, constitution of, 33... Pos- sible limit of, 36. Its waves, 37. Strata, 37. Causes refraction, 38. Twilight, 44. Total mass of, 148. Of Jupiter, 513.
Attraction of a sphere, 445-450. (See Gravitation.)
Augmentation of moon's apparent dia- meter, 404.
Augustus, his reformation of mistakes in the Julian calendar, (919.) Era of, 926.
Australia, excessive summer tempera- ture of, 369.
Axis of the earth, 82. Rotation per- manent, 56. Major of the earth's orbit, 373. Of sun's rotation, 392. Axis of a planetary orbit. Momentary variation of, caused by the tangential force only, 658. 660. Its variations periodical, 661... Invariability of, and how understood, 668. Azimuth, 103.-and altitude instru- ment, 187.
of, 291... Bremiker's, 506, and note. Chinese records of comets, 574. irregular stars, 831. Chronometers, how used for determining differences of longitude, 255. Circle, arctic and antarctic, 94. Verti-
cal, 100. Hour, 106. Divided, 163. Meridian, 174. Reflecting, 197. Re- peating, 198. Galactic, 793. Clepsydra, 150.
Clock, 151. Error and rate of, how found, 253.
Clouds, greatest height of, 34. Magel- lanic, 892...
Clusters of stars, 864... Globular, 867. Irregular, 869.
Collimation, line of, 155.
Collimator, 178...
Coloured stars, 851...
Colures, 307.
treme tenuity of, 558. General de- scription of, 560. Motions of, and described, 561... Parabolic, 564. Elliptic. 567... Hyperbolic, 564. Di- mensions of, 565. Of Halley, 567... Of Cæsar, 573. Of Encke, 576. Of Biela, 579. Of Faye, 584. Of Lexell, 585. Of De Vico, 586. Of Brorsen, 587.
Of Peters, 588. Sy- nopsis of elements (Appendix). In- crease of visible dimensions in re- ceding from the sun, 571.580. Great, of 1843, 589... Its supposed identity with many others, 594... Interest at- tached to subject, 597. Cometary statistics, and conclusions therefrom, 601.
Commensurability (near) of mean mo- tions; of Saturn's satellites, 550. Of Uranus and Neptune, 669. and note. Of Jupiter and Saturn, 720. Earth and Venus, 726. Effects of, 719. Compensation of disturbances, how ef- fected, 719. 725.
Compression of terrestrial spheroid, 221. Configurations, inequalities depending on, 655...
Conjunctions, superior and inferior, 473. Perturbations chiefly produced at, 713. Consciousness of effect when force is exerted, 439. Constellations, 60. 301.
How brought into view by change of latitude, 52. Rising and setting of, 58. Copernican explanation of diurnal mo- tion, 76. Of apparent motions of sun and planets, 77.
Correction of astronomical observations, 324... s. Uranographical summary, view of, 342...
Culminations, 125. Upper and lower, 126.
Cycle, of conjunctions of disturbing and disturbed planets, 719. Meto- nic, 926. Callippic, ib. Solar, 921 Lunar, 922. Of indictions, 923.
Day, solar, lunar, and sidereal, 143. Ratio of sidereal to solar, 305. 909. 911. Solar unequal, 146. Mean ditto, invariable, 908. Civil and astronomical, 147. Intercalary, 916. Days elapsed between principal chro- nological eras, 926. Rules for reckon- ing between given dates, 927. Declination, 105. How obtained, 295. Definitions, 82...
Degree of meridian, how measured, 210. | Egyptians, ancient, their chronology, Error admissible in, 215. Length of in various latitudes, 216. 221. Diameters of the earth, 220, 221. planets, synopsis, Appendix. (See also each planet.)
Dilatation of comets in receding from the sun, 578. Dione, 548.
Distance of the moon, 403.; the sun, 357.; fixed stars, 807. 812...; polar,
Districts, natural, in heavens, 302. Disturbing forces, nature of, 609... Ge- neral estimation of, 611. Numerical values, 612. Unresolved in direc- tion, 614. Resolution of, in two modes, 615. 618. Effects of each resolved portion, 616... On moon, expressions of, 676. Geometrical re- presentations of, 676. 717. Diurnal motion explained, 58. Paral- lax, 339. Rotation, 144. Double refraction, 202. Image micro- meter, a new, described, 203. Co- met, 580. Nebula, 878. Double Stars, 833... Specimens of each class, 835. Orbitual motion of, 839. Subject to Newtonian attraction, 843. Orbits of particular, 843. Dimen- sions of these orbits, 844. 848. Co- loured, 851... Apparent periods af- fected by motion of light, 863. Dove, his law of temperature, 370.
Elements of a planet's orbit, 493. Va- riations of, 652... Of double star or- bits, 843. Synoptic table of planet- ary, &c., Appendix.
Ellipse, variable, of a planet, 653. Mo- mentary or osculating, 654. Elliptic motion a consequence of gravi- tation, 446. Laws of, 489... Their theoretical explanation, 491. Ellipticity of the Earth, 221. Elongation, 341. Greatest, of Mercury and Venus, 467. Enceladus, 548., note. Encke, comet of, 576. His hypothesis of the resistance of the ether, 577. Epoch, one of the elements of a planet's orbit, 496. Its variation not inde- pendent, 730. Variations incident
on, 731. 744. Equation of light, 335. Of the center, 375. Of time, 379. Lunar, 452. Annual, of the moon, 738. Equator, 84. Equatorial, 185.
Equilibrium, figure of, in a rotating body, 224.
Equinoctial, 97. Time, 935. Equinox, 293. 303.
Equinoxes, precession of, 312. Its ef- fects, 313. In what consisting, 314... Its physical cause explained, 642... Eras, chronological list of, 926. Errors, classification of, 133. Instru- mental, 135... Their detection, 140. Destruction of accidental ones by taking means, 137. Of clock, how obtained, 293.
Establishment of a port, 754. Ether, resistance of, 577. Evection of moon, 748. Excentricities, stability of Lagrange's theorem respecting, 701. Excentricity of earth's orbit, 354. How ascertained, 377. Of the moon's, 405. Momentary perturbation of, investi- gated, 670. Application to lunar theory, 688. Variations of, in orbits nearly circular, 696. In excentric orbits, 697. Permanent inequalities depending on, 719.
of place, 670, 671. Path of, in virtue | of both elements of disturbing force, 704. Traced in the case of the moon's variation, 706... And paral- lactic inequality, 712. Circulation of, about a mean situation in planetary perturbations, 727.
Force, metaphysical conception of, 439. Forced vibration, principle of, 650. Forces, disturbing. See Disturbing force.
Galactic circle, 793. Polar distance, ib.
Galaxy composed of stars, 302.
W. Herschel's conception of its form and structure, 786. Distribution of stars generally referable to it, 786. Its course among the constellations, 787... Difficulty of conceiving its real form, 792. Telescopic analysis of, 797. In some directions unfathom- able, in others not, 798. Gulle, Dr., 506. Finds Neptune in place indicated by theory, 768. Galloway, his researches on the sun's proper motion, 855.
Gasparis, Sig. De, discovers a new planet (Appendix). Gauging the heavens, 793.
Gay Lussac, his aëronautic ascent, 32. Geocentric longitude, 503. Place, 371.
Hansen. His detection of long ine- qualities in the moon's motions, 745... Harding discovers Juno, 505. Heat, supply of, from sun alike in summer and winter, 368. How kept up, 400. Sun's expenditure of esti- mated, 397. Received from the sun by different planets, 508. Endured by comets in perihelio, 592. Hebe, discovery of, 505.
Heights above the sea, how measured, 286. Mean, of the continents, 289. Heliocentric place, 500. Heliometer, 201.
Hemispheres, terrestrial and aqueous,284. Herschel, Sir Wm., discovers Uranus, 505, and two satellites of Saturn, 548. His method of gauging the heavens, 793. Views of the structure of the Milky Way, 786. Of nebular sub- sidence, and sidereal aggregation, 869. 874. His catalogues of double stars, 835. Discovery of their binary con- nexion, 839. Of the sun's proper motion, 854. Classifications of ne- bulæ, 868. 879. note.
Horizon, 22. Dip of, 23. 195. Rational and sensible, 74. Celestial, 98. Arti- ficial, 163.
Horizontal point of a mural circle, how determined, 175...
Hour circles, 106.; angle, 107.; glass,
Iapetus, 548. Inclination of the moon's orbit, 406. Of planet's orbits disturbed by orthogo- nal force, 619. Physical importance of, as an element, 632. Momentary variation of, estimated, 633. Crite- rion of momentary increase or dimi- nution, 635. Its changes periodical and self-correcting, 636. Application to case of the moon, 638. Inclinations, stability of, Lagrage's theo- rem, 639. Analogous in their per- turbations to excentricities, 699. Indictions, 923. Inequality. Parallactic of moon, 712. Great, of Jupiter and Saturn, 720... Inequalities, independent of excentri- city, theory of, 702... Dependent on, 719. Intercalation, 916.
Iris, discovery of, 505. Iron, meteoric, 888.
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