CASPIAN SEA has no fenfible DENSITY of the whole matter in the earth, 68. proportional, of the fun and planets, 272, 345, 346. DESCENDING NODE defined, 457, 577. mark of it, ib. DIAMETERS of the fun and pla nets, 271.
CELESTIAL BODIES, appear- ances of the, as feen by the naked eye, 71-91. as feen through telescopes, 92—137.
ASCENDING NODE, place of the, CENTRIPETAL POWER'S illuftra- 271. defined, 354-577- ASPECTS of the planets, 359. ASTRONOMICAL inftruments,
described, 682. machinery, 666-681. quadrants, 686-- 695. Sector, 696. Tables, how to conftruct, 563. writings, 70. ASTRONOMY, etymology of, de- finition of, fublimity and ufe- fulncfs, 3. antiquity of, 4-20. hiftory of, 4-69. various fyf- tems of, 248-256. the true fyftem of, 257, 272. ATHENIANS erect a ftatue to
Berofus the aftronomer, 28. ATLANTIC ocean, tides in the, lefs than in the Pacific, 477. ATMOSPHERE, a lunar, argu- ments against the existence of, 161. anfwered, 162-169. ATMOSPHERE, fuppofed to have aerial tides, 481. light refract- ed by it, 497-501. ATMOSPHERES, Venus and Mars have, 107, 108. ATTRACTION of the great moun- tains, affects the plumb-line, 61. Dr Herfchel's ideas of the effects of attraction upon the heavenly bodies, 220--226. a queftion refpecting attraction, 243. it power fuppofed to be balanced by projectile forces, 245. effects of attraction on the motions of the planets, 282-- 344.
AURORA BOREALIS, affinity be- tween the, and the tails of comets, 192, 193. Axis of the earth defcribed, 390,
AZIMUTH CIRCLE, utility of the, 694. how to adjust it, 708.
B. BALTIC Ocean has no fenfible tides, 480. BEARDEDCOMET, explained, 133. BELTS. See JUPITER. BENARES, a celebrated obferva- tory at, 12. BLACK SEA has no fenfible tides, 480.
BODIES of the fun and planets
deferibed, 332-336. BULL'S EYE, more foutherly than the ancients placed it,
CALIPPIC PERIOD corrected by Hipparchus, 31. CARTESIAN System, 256.
CHALDEA, a country proper for aftronomical obfervation, 19. CHALDEANS, early aftronomers, 13, 19, 20. CHINESE, faid to have been taught aftronomy by Noah, 8. their fuperftition, 660. CHRONOLOGY, eclipfes ufeful in, 661.
CIRCLES defcribed by the plan- ets, 347-355. COLD, caufe of, in winter, 424 -426.
COMETS, written on by Mullar, 40. obferved by Werner, 42. and Hevelius, 46. their paths difcovered by Kepler, 49. their places obferved, and ele- ments computed by Dr Brad- ley, 62. their number and ap- pearances to the eye, 81. ap- parent magnitudes, 82. ap- pearances through telescopes, 130-134. of their tails, 132- 134. conjectures refpecting comets, 171-178. conclufions drawn from obfervation, 180. -202. numbers noticed, 260. their nature and motions, 327 -331. fais to occafion eclipfes of the fun, 665. CONJUNCTION of Jupiter and Saturn, obferved by Tycho Brahe, 48.
CONJUNCTIONS of planets de- fined, 359. mark of, 360. CONSTELLATIONS, number of the Chinese, 8. how marked, 9. when first used by the Greeks, 23, 24. names of the ancient, 548. and modern, 549, 550. number of ftars in each, 548- 550. COPERNICAN SYSTEM publish- ed, 43. improved, 44. ac- count of it, 257-272. much cppofed at firft, 258. confirm- ed by Newton, 259. CRABTREE, Mr, fee the first tranfit of Venus ever obierved, 52, 537-
CRYSTALLINE HEAVENS, an erroneous notion in the Ptole- maic System, 251. D.
DARKNESSES, extraordinary, fuppofed to be caufed by co- mets, 187, 665. DELUGE, fuppofed to have been caused by a comet, 195.
DICHOTOMY of the moon, ufed by Ariftarchus to determine the fun's distance, 29. DIFFRACTION of rays, defized,
DIRECT MOTION of a planet defined, 378.
DIURNAL rotations of the fua and planets, 271. of the earth illuftrated, 411-414. DRUIDS early aftronomers, 28. E.
EARTH, the figure of the, difpute concerning, 61. mean deality of matter in it, 68. the motion of, maintained by Pythagoras and Nicetas, 257. its revolu. tion, diurnal rotation, prepor tional denfity, &c. 250-272 diftance from the fun, 386. da meter and motion, ib. form, 387, 388, 389.angle of its axis, 39c. its motion round the fun, ib.proved, 391-401.objectice. 402. moves on its axis, 433- 410, its motions illuftrated, 411 -431. appears as a moon to the Lunarians, 435. and the biggest body in the univerte, b ECLIPSES, the theory of, koura to the Chinese, 10. accounts of, collected by Hipparchus, 51. preliminary obfervations re fpecting, 570-382, ruks and examples for calculating, 583, 584-649. for a gra folar eclipfe, 650-657-cclip- fes of Jupiter's fatellites, 644- cometary eclipfes, 665. cza fes of, explained, 676. ECLIPTIC, obliquity of the, is Ptolemy's time, 29. fxd Ir Albategnius, 34. obferved b Arzachel, 35. corrected by Werner, 42. derivation of ur name, 349. how to frd the ecliptic, 350 352, and its co- liquity, 553. it is lefs then in Ptolemy's time, 554. the b cliptic, is comprehended in zodiac, 546. EGYPT, a country proper år aftronomical obfervations. I » ELECTRIC FLUID, fuppoff Hamilton, to be brought h to the planets by conats, an ELLIPTICAL ORBITS of nets, difcovered by Ko 49. of Saturn's fatellites ar comets, very excentra, ELONGATION
ELONGATION, greateft, of infe- rior planets, 272. defined, 361. EPHEMERIDES made by Pur- bach, 40.
phænomena, ib.-118. other, phænomena, 264, 267, 2703 271, 272. attractive power of Jupiter, 301, 301. motion of light from Jupiter to the earth, 396, his fatellites often eclipfed, 664.
HARVEST MOON rifes fooner than any other, 482. reafons of this, 483-488. goes through a courfe of more and lefs be- neficial ftates, 489. HEAT of comets, Newton's efti- mate of the, 194. HEAVENS, general appearance of the, 74. divifions of the ftarry,
EPICYCLE, a term in the Ptole-
maic, System, 252. EQUINOCTIAL, obliquity of the, 421. caufe of the feafons, ib. EQUINOXES, preceffion of the, calculated, 34, 42. EVENING STAR, 77. EXCENTRICITIES of the planets, 270. how to determine, 561. EXCENTRICITY of the earth's orbit, rule to determine, 560. EXCENTRICS, a term in the Ptolemaic System, 252. F.
FACULE of the fun explained, 97. FALLING BODIES, velocity of, 303, 304.
FIELDS OF STARS defined, 212. Fо-нI, emperor of China, taught the Chinese aftronomy, 80. FORCES, CENTRAL, explained
GALAXY. See MILKY WAY. GEOCENTRIC LATITUDE defi- ned, 353.
GEOCENTRIC MOTION explain-
ed, 361, 362, 370. GEOMETRY introduced into af- tronomy, 27. GEORGIAN PLANET, difco- GEORGIUM SIDUS,vered by Dr Herschel, 96. has two fa- tellites, ib. 128. its diftance from the fun, 69. its apparent magnitude, 128. fuppofed fize of the fatellites, ib. periods of revolutions and distances, 129. GLOBE, the improved celeftial, defcribed, 677-678. GNOMON, the ufe of a, known to the Chinese, 10. ufed by Pythoas, 28., one erected at Bologna, 59. GRAVITATION
defined, 289. its, effects on the planets, 290 -298. and fatellites, 300- 308. on the moon in particu- lar, 306-319. illuftrated, 320 -326. is diffused through the whole fubftance of the celef- tial bodies, 332-344. GRAVITY, various effects of, 275, 306. illuftrated, 276-281. GREEKS, probable origin of their aftronomy, 23, 24, 25, Vitruvius's account of it, 23. H.
HALLEY, Dr, examines Heveli- us's inftruments, 54. and makes obfervations along with him, ib. makes a catalogue of the fixed stars, 60. makes ta- bles of the comets, 197, 198. VOL. II. PART II,
542-550. HELIOCENTRIC CIRCLES defi- ned and defcribed 347, 349. HELIOCENTRIC LATITUDE, de- fined, 353. HERSCHEL, Dr, improves the reflecting telescope, 59. con- ftructs very powerful ones, 69. difcovers a new planet with fatellites, ib. his obfer- vations on Venus, 107. and Mars, 108. he difcovers two rings round Saturn, 122-124. a fixth and feventh fatellite, 125. and vaft numbers of ne- bulæ, 137. he obferves erup- tions of the lunar volcanoes, 158. forms a new theory of the universe, 210, 211. his theory of the heavens, 221- of nebulous ftrata, 233- 242. He propofes to afcertain the parallax of the flars, 539. HERSCHEL, the new planet fo named by foreign aftrono- mers, 69. See GEORGIUM SIDUS.
HORIZONTAL PARALLAX, defi- ned, 522. how to find it, 523. HORIZONTAL SUN and MOON, apparent magnitude of the, 490. accounted for by Alha- zen, 491. Des Cartes and Wallis, 492, 493. Dr Defa- guliers, 494, and Dr Smith, 495. probable cause, 496. HUENNA, Tycho Brahe builds an obfervatory on, 48. I. J.
INCLINATIONS of the planets to the ecliptic, 271. INDIANS, early aftronomers, 14. INFERIOR PLANETS defined, 354. INSTRUMENTS defcribed, 682
KPELER'S LAWS, 283-285. il luftrated, 286-289.
L. LATITUDE of a planet defined
353. of a place, direction for finding the, 552.
LIGHT, progreffive motion of difcovered, 59, 395 propor tions of, in the planets, 272. velocity and aberration of, 396 -402. afford evidence of the motion of the earth, 395, 409 -411. illuftrated, 412-414 quantity of, afforded by the earth to the moon, 435. re- fraction of, by the atmosphere, 197 501.
LOCAL ZODIAC, defcribed, 355. LONDON BRIDGE, time of the tides arriving at, 478. LONGITUDE, method of finding the, propofed by Wernet, 42. by Dr Halley, 60. executed, ib. Longitude of a celestial phæ. nomenon defined, 357. of pla- ces, easily found in the moon, 438. eclipfes ufeful in deter. mining it, 661, 664. LOOPED CURVES of the planets
defcribed, 375-377, 493 LUNAR ECLIPSES, two happen annually, 602. one vifible, the other not, 603. Rules for cal- culating, 610-628. exempli- fied, 676. LUNAR TABLES completed, 63.
fhow the moon's place trueit in the syzygies, 627, 628. LUNARIANS, appearances of the
earth to the, 435, 436, 442. have always equal day and night, 437-439. LUNATIONS, no complete num- ber of, finished without a frac tion, 580. See Moon.
MATTER, univerfal attraction of, proved, 68, 291, 332-344. denfity of, in the earth, 68, 291, and planets, 346. quantity ot, in the fuperior planets, 345. MEAN DISTANCES of the pla-
MEDITERRANEAN SEA has no tides, 480.
MERCURY, appearance of, to the eye, 76. and through a tele- fcope, 106. has phases fimilar to thofe of the moon, ib. 264. feen in conjunction with the fun, 364. and pafling over his difk, 365. when he will be thus feen again, ib. his motion une- qual, 366.
MERIDIAN, Fules for finding the, 708, 713.
MERIDIAN LINE, rules for draw-
ing a, 502, 507. MICROMETER improved, 58. ne- ceifary for meafuring angular diftances, 685.
MILKY WAY, appearance of the 90. Dr Herichel difcovers in- numerable multitudes of ftars in it, 212. he views it by fields ib. and supposes the fun to be in it, 216. he gauges it, 220. MONTH, fynodical and periodi- cal, defined, 565. Mean, acceleration of the, de- termined by Ebn Younis's ob- fervations, 35. difcovered by Dr Halley, 60. her appearan ces to the eye, 72. and thro' a telescope, 104, 105. number and names of her principal ipots, 105. great inequalities on her furface, 156.fuppofed to be mountainous, ib. attempts made to measure their height, 157. Dr Herfchel's eftim te,
fimilarity between them and terreftrial mountains, 158. volcanoes among them, ib. conjectures refpe&ting the meon's fubftance, 159. and her fpots, 16c. controverfy a- bout her having an atmof phere, 161-169. arguments for the negative, 161. and for the affirmative, 162–165. a luminous ring around her, in total eclipfcs, 166. experi- 10en's refpeéting it, 167. re- inark, 168, 169, inquiry whe, ther the moon is inhabited, 170. her fuifice rough and uneven, 203. her orbit and motion, 201. 02. illuftrated, 303-326. hur conjunctions, &c. 359, 30. and peculiar pbanctaena, 433-447, the in, fecrees the tides, 448-480. proportion of her icke to
O. OBSERVATORIES, the towers of Babel and Belus fuppofed to be, 19. the pyramids of Egypt probably used as fuch, ib. OBSERVATORY defcribed, 68: the portable, defcription c
that of the fun in moving the NORTH POLE STAR, appearance fea, 457. her appearance at of the, 73, 74. the full in harvest, 482. caufes of it, 483-489. appearance near the horizon, 490. vari- ous reafons affigned for it, ib. -496. inequalities of her motions, 564. how to find her diurnal and horary motions, &c. 567-569. caufes of her eclipfes, 570-582. rules for calculating them, 584-628. to find her way from the fun, 629-634. her colour, &c. during an eclipfe, 658, 659. her diftance from the earth lefs than formerly, 662. her various phafes exemplified, 672-6745 676. MORNING STAR, 77. MOTION, planetary, laws of, 285-285.363-325. of light,
Morions of comets, 327-331. of planets in antecedence and confequence, defined, 355. di- re&, 363, 378. and retrograde, 363, 379. progre five of light, 409, 410. annual and diurnal of the earth, 411-414, 5II.
N. NAUTICAL ALMANACK annual- ly published, 67. NAUTICAL EPHEMERIS publifh- ed, 63.
NEAP TIDES, caufe of the, 453,
NEBULA explained, 137. vaft numbers of, difcovered by Dr Herfchel, ib. his account of them, 214-233- NEW STARS, account of feveral, 84-89.
NEWTON, Sir Ifaac, conftructs reflectors with fpherical fpe- culums, 6. brings fpeculative aftronomy to perfection, 57. determines the figure of the earth, 61. difcovers the true motion of comets, 180. is of opinion that they are opaque bodies, 183, and that their tails are a thin vapour, expell- ed by the heat, 189. his efti- mate of the heat of comets 194. he confirms the Coper nican fyftem, 259. lays down the laws of motion, ib. and gravity, 25. 281. his argu- ment against the ctunity of the world, 299. NODES defined, 260. how to
find the motion of the meon's 323, 224. line of the nodes, defined, 354. NONAGISIMAL degree defned 443.
OCCULTATION of Jupiter, by the moon, obferved, 54. OCTANTS of the moon defcri- bed, 448. OPPOSITION defined, 359.1 of, 360. ORBITS, of the planets, inclina. tions of the, to the ecliptic,.1 defcribed, 282-298, of the fecondary planets, 320-13f, their excentricities, 360-pl ORION, number of stars in, 1. ORRERY erected by Archimethy 30 defcription of the greed, made for king George I. 1. of Mr Ferguton's, 665-674 OSYMANDYAS, an aftronomic circle in the monument of ly P. PARABOLA of a comet, method of finding the, 319. PENDULUM, a tent of velocity, 304. caufe of its vibratkan, 333. vibrates quickeft near the poles, 405. PENDULUM 683. PENUMBRA, rule to find the place touched by the, 6: PERIGEE defined, 372, 381. PERIOD of eclipics, &c. f ECLIPSES.
CLOCK deferbed,
and times of the plants, PISCES and Aries, appete of the moon in, 433–485. PLANETARIUM, erected by a chimedes, 30. Mr June fcribed, 675. PLANETS, a theory of the, with by Muller, 40. their appe ces to the eye, 75-8a ruD her, 75. apparent magata 8o. and motions, ib. Sept fed by Kepler to be huge mals, who fwim read t fun by means of fits! 1- Planets ditturb the motions vā comets, 202. Their Ins and order, 260. are all epage bodies, 263. and fphorical, s their periods, diftances, a csa centricities, 270. planets, scc-126, them a cles defined and dec 347-2529 355. their th 353–356. and long tree, conjunctions, opp titles
afpects, 359-368. ftationary appearances, 369-373. appa- rent paths, 374, 375. motions, 376, 377. direct. 378. and retro- grade, 379. in apogee and pe- rigee, 372, 381. periods of re- turn, 382-385. rules for find. ing the parallax of planets, 522 -533 their diftances, 534-
536. and periodical times, 559, PLEIADES, number of stars in, 136.
POLE of the heavens, how to find
the altitude of the, 552, 654. POLES defined, as ufed by Herf- chel, 237.
POLES of the earth, bodies hea-
vieft, when near the, 405. PROGRESSIVE MOTION of light proves the motions of the earth, 395-414. PROJECTILE FORCES, fuppofed by Dr Herfchel, to counter-act the power of attraction, 245. rendered probable by changes of the politions of ftars, 246. PROPORTIONAL DISTANCES of the planets from the fun, 270. PROPORTIONS of light, heat, bulk, and density of the pla-
PYTHAGOREAN fyftem of aftro- nomy, taught by Philolaus, 26. and Ariftarchus, 29. car- ried into Italy, Gaul, and E- gypt, 27, 28. restored, 43.250. PYTHAGOREANS held comets to be of the nature of planets, 172. Q. QUADRANT, MURAL, described, 687-693.
QUADRANT, PORTABLE, defcri-
bed, 694, 695. QUADRANT, REFLECTING, in- vented, 57. QUADRATURE defined, 359,360. R.
REFRACTION of light by the at-
mosphere, 497. illuftrated, 498 -501. REFRACTIONS, the ufe of, in af-
tronomy, fhown by Alhazen, 35. and Vitello, 38. RETROGRADE MOTION of a pla- net, defined, 363. REVOLUTION of the heavens, not a real motion, 411. RIGHT ASCENSION of the ftars, rule for finding the, 556, 557. RING. See SATURN. S. SAMARCAND, the latitude of, de- termined by Ulug Beg, 36. SATELLITES, four revolve round Jupiter, 111. feven around Sa- turn, 126. and two around Herfchel, 128.
SATURN, his ring difcovered, 51. 119. and five of his fatellites, 55 his appearance to the na- ked eye, 79. and through a telescope, 119. his ring defcri- bed, 120, 121. found by Dr Herfchel to be double, 122. not changeable, 123. period of his revolution, 124. and feven fatellites in all, 125. their pe- riodical revolutions and diftan- ces, 126. the revolution of Sa- turn retarded 13 days, by the approach of Jupiter, 199. phæ- nomena of Saturn's ring, 266. mutual attraction between Ju- piter and Saturn, 296, 297.
their power, 302. SEA, the ebbing and flowing of the, caufes of, 449—467. SEASONS, caufes of the, 415-
429. had fallen back, 430. rec- tified by the new ftyle, ib. 41. SECTOR, EQUATORIAL, deferi- bed, 696-699.
SEMITA LUMINOSA, explained
STARS, FIXED, catalogues of the, made by Hipparchus, 31. U- lug Beg, 36. William IV. of Heile, 47. Tycho Brahe, 48. Dr Flamstead, 59. Dr Halley, 60, and Dr Herfchel, 69. their aberration discovered, 57. ap- pearances to the eye, 73-75. moft numerous in the northern part of the heavens, 73-75. moft numerous in the northern part of the heavens, 73. liable to changes, 83. their appear- ances through telescopes, 135 -137, fuppofed to be funs, 203209. Dr Herfchel's theo- ry, 210, 211, and obfervations of innumerable multitudes of fars, 212-242. his inferences, Zzzzz
243. apparent changes of itars, 246. are fituated at an im- menfe distance, 261. fhine by their own light, ib. no method found to afcertain their dif- tance, 538. conjecture as to it, 539. Dr Herfchel's method, 540. ftill infufficient, 541. di- vifions of the stars, 542-350. number of in the conftellations, 548-550. how to find their right afcenfion, 556, 557. lon- gitude and latitude, 558. STYLE, reason for the change of,
SUN, fpots on the, discovered, 51. his parallax and diftanse computed, 65. his appearance to the eye, 71. and through a telefcope, 92-103. his fpots obferved by Galileo, Scheiner, and Harriot, about the fame time, ib. 93. variety and di- mentions of them, 94. fubjeét to increafe and diminution, 95 -97. their velocity, 98. and. uniform motion from E. to W. ib. other phænomena re- fpecting them, 99-103, Dr Long's account of them, 144, 145. how to find the time of their revolutions, 146, 147, different opinions concerning them, 148. Dr Willon's, 149 -154. an experiment propo- fed, 155. the fun fuppofed to be not in the centre of the u- niverfe, 216. is at an immenfe diftance, 262. mutual gravi- tation between the fun and primary planets, 289-297. action of the fun upon the fecondary planets, 300-326. proportion of his action on both, 335-344. his conjunc- tions with the planets, 359- 385. is immenfely larger than the earth, 391, 392. proofs. that the earth moves round the fun, 393-414. and that the fun moves round his axis, 403. 404. he is higher in fummer than in winter, 422. and more diftant, 424. reafons of his fu- perior heat, ib.-426. periods of his completing a tropical and fiderial year, 427. appears to fall back with regard to the flars, 418. reafons for his magnitude near the horizon, 490-496. the motion of the fun illuftrated, by supposing a fetitious fun to move equa- bly, 513-521. the fun's paral- lax, the most important prob lem in aftronomy, 536. how to find the fun's declination,
$55. and the moon's way from the fun, 629-634. to calcu- late eclipfes of the fun, 635- 637.
SYNOPSIS of the fun and pla-
nets, 269-272. SYSTEMS of aftronomy, account of the most famous, 248- 281. of the Pythagorean, 250. Ptolomæan, 251-2:53. Ty- chonic, 254. Semi-Tychonic, 255. Cartefian, 256. and Co. pernican, 257-281. T.
TABLES, aftronomical,, publish- ed, 38, 49, 60, 63, 552. how to conftruct, 563. TAILS of comets, various thec
ries refpecting, 188-193. One comet has fometimes feveral tails, 192. They are probably ftreams of electric matter, 193. TELESCOPES, improvement of, 54-59. various kinds of, 684, 690, 700, 704 how to point,
TRAJECTORUM LUNARE, de- fcribed, 679-681. TRANSIT INSTRUMENT, defcri- bed, 700-703. TRINE ASPECT, definition and mark of a, 360.
TROPIC of Cancer defcribed, 417. of Capricorn, 419. TWILIGHT, caufe of the, 500, 501.
TYCHONIC SYSTEM, account of the, 254.
VELOCITY of the fpots on the fun, 98. of comets greatest in their perihelion, 182. of bo- dies, phænomena of the, 274. 303, 304. of the earth, 386. of light, 396. VENUS, the firft tranfit of, ever obferved, 52, the 2d and 3d obferved in various places, 65. inferences, ib. her appearance to the eye, 77. and through a telefcope, 107. her phases and changes fimilar to thofe of the moon, ib. were firft obferved by Galileo, ib. Dr Herschel's obfervations and inferences, ib. fhe has an atmosphere and is larger than the earth, ib. pe- riods of her tranfits, 365. her apparent paths, 374. and mo- tions, 382, 383. rules for cal- culating her parallax, 531,532. 535, 536. advantage of obfer- ving her tranfits, 536. hiftory of them, 537. Venus's path traced, 558.
VERNIER defcribed, 691, 692. VIBRATION of pendulums, caufe of the, 333.
VISIBLE ECLIPSES, number of, in the year, 603. UMBRA on the fun defined, 100,
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