ALPHONSINE tables composed, 37. and corrected, 38.
ALTITUDE of the sun observed by Pytheas, 27.
AMAZON river, five high, and four low tides in, at
once, 480.

AMERICANS acquainted with astronomy, 17.
ANNUAL motion of the earth illustrated, 410-413.
ANOMALY, mean and true, 602. Eccentric, 604.
To find true on terms of mean, 604-609.
ANTARCTIC circles defined, 418.
ANTEDILUVIANS acquainted with astronomy, 3-5.
ANTICIPATION of the equinoxes, 429-431.
APHELION OF APSIDE of the planets, 601. Method
of finding place and motion of, 610. 617. 647.
Table of places of, 235.

ASCENDING node of planets, table of places of, 234. Defined, 335. 673.

ASPECTS of the planets, 340. ASTRONOMICAL instruments described, 776-862. Quadrants, 780-789. Mural circle, 790-811. Equatorial sector, 812-815. Transit Instrument, 816-850. Equatorial, 851-861. Machinery for illustration, 762-775. ASTRONOMICAL Society of London, 74. 180. ASTRONOMY, etymology of, definition of, sublimity and usefulness, 2. Antiquity of, 3-19. History of, 3-76. Various systems of, 210. 218. True system of, 219. 235.

ATHENIANS erect a statue to Berosus the astronomer, 27.

ATLANTIC Ocean, tides on the, less than on the Pacific, 479.

ATMOSPHERE, lunar, 170. Supposed to have tides, 483. Light refracted by it, 501-511. ATMOSPHERES, Venus and Mars have, 112, 113. Doubtful whether Mercury has one, 111. ATKINSON on refraction, 510,511.

nius, 33. Defined, 353. 360.

ARABIANS cultivated astronomy, 32, 33.

ARACTA, tables formed for the meridian of, 33.
ARCTIC circle defined, 416.

ARCTURUS, half a degree more southerly than observed by the ancients, 208.

ARMILLARY sphere erected at Alexandria, 28.

line, 60. Dr. Herschel's ideas of the effects of attraction of the heavenly bodies, 194. 200. power supposed to be balanced by projectile forces, 207. Effects of attraction on the motions of the planets, 254. 327.

Its

ATTRACTIVE force, law of, between different planets, 203--314.

CHALDEA, a country proper for astronomical observa-
tion, 18.

CHALDEANS, early astronomers, 12. 18, 19.
CHINESE, said to have been taught astronomy by
Noah, 7. Their superstition, 756.
CHRONOLOGY, eclipses useful in, 757.
CIRCLES, described by the planets, 328-336.
CLAIRAULT computed the orbit of a comet, 178, 179.
COLD, cause of in winter, 423-425.

COMETS, written on by Muller, 39. Observed by Wer-
ner, 41. And Hevelius, 44. Paths of, discovered by
Kepler, 48. Places of observed, and elements com-
puted by Bradley, 61. Number and appearances to
the eye, 87. Apparent magnitude, 88. Appear-
ances through telescopes, 142-146. Of their tails,
144-146. Fancies respecting, 172. Perihelion
distances, 175. Conjectures respecting tails, 176.
Methods of determining the orbits of, 294-302.
Resistance of æther inferred from the motion of
Guke's, 180,

COMMUTATION, angle of, 624.

CONJUNCTION of Jupiter and Saturn observed by
Tycho Brahe, 47.

CONJUNCTIONS of planets, 340, 341.
CONSTELLATIONS, number of the Chinese, 7. How
marked, 8. When first used by the Greeks, 22, 23.
Names of the ancient, 595. And of the modern,
596, 597. Number of stars in each, 595-597.
COPERNICAN SYSTEM published, 42. Improved, 43.
Account of, 219-235. Much opposed at first,
220. Confirmed by Newton, 221.

CORPUSCLE, attraction of a line on, 313. Of a plane
on, 314. Of a sphere on, 315.

CRABTREE, Mr. sees the first transit of Venus ever
observed, 51. 583.

density of matter in it, 67. The motion of main-
tained by Pythagoras and Nicetas, 219.
Its revo-
lution, diurnal motion, proportional density, &c.
233. 235. 327. Distance from the sun, 366.
Diameter and motion, ib. Form, 366-368. Angle
of its axis, 369. Its motion round the sun proved,
370-386. Objection, 387. Revolves on its axis,
383-409. Its motions illustrated, 411-431.
Appears as a moon to the Lunarians, and the
largest body in the universe, 435. Irregularity of
the form of its orbit, 276.

ECCENTRICITIES of the planets, 233. Method of
finding, 648.

ECCENTRICS, a term used in the Ptolemaic system,
214.

ECLIPSES, the theory of, known to the Chinese, 9.
Accounts of, collected by Hipparchus, 50. Pre-
liminary observations respecting, 666-678. Rules
and examples for calculating, 679-745. For a
general solar eclipse, 746-753. Eclipses of Ju-
piter's satellites, 25-760. Cometary eclipses,
761. Causes of explained, 772.

ECLIPTIC, obliquity of the, in Ptolemy's time, 28.
Fixed by Albategnius, 33. Observed by Arzachel,
34. Corrected by Werner, 41. Derivation of the
name, 330.
To find the obliquity of, 331. 333.
563, 564. Periodical variation in obliquity, 393.
Comprehended in the zodiac, 593.

EGYPT, a country adapted to astronomical observa-
tions, 18.

ELLIPTICAL orbits of the planets discovered by Kep-
ler, 48. Of Saturn's satellites, 136. Of comets,
very eccentric, 225.

ELONGATION, greatest of inferior planets, 235. De-
fined, 362-629.

EPHEMERIDES, made by Purbach, 38.

EPICYCLE, a term in the Ptolemaic system, 214.
EQUATION of centre, 607, 608.

EQUATION of time, table of, 543. Auxiliary table for
reducing to subsequent year, 544.
EQUATORIAL described, 851-862.
EQUINOCTIAL, obliquity of the, 420. Cause of the
seasons, 420.

EQUINOCTIAL point, method of finding the, 565.
EQUINOXES, precession of the, 33-41.
EVENING star, 83.

FACULE of the sun explained, 103.

Ptolemaic system, 213.
CURTATE distance, 625.

DARKNESS, extraordinary, supposed to be caused by
comets, 761.

DECLINATION, sun's, table of, 550, Principal fixed
stars, 863.

FIELDS of stars defined, 188.

FIXED stars, table of proper motions of, 209.
logue of principal, 864.

Cata-

FO-HE, emperor of China, taught the Chinese astro-
nomy, 7.

FORCES, central, 236. 242. 247.

GEOCENTRIC latitude defined, 334.

GEOCENTRIC motion explained, 342, 343. 351.
GEOCENTRIC observations, method of reducing to he
liocentric, 618, 625.

GEORGIAN planet, Georgium Sidus, Uranus, or Herschel, discovered by Herschel, 139. Apparent magnitude, ib. Diameter, ib. Periodic revolution. ib. Has six satellites, ib. Remarkable peculiarity in Theoretical deducPeriods and elon

the position of their orbits, ib. tion of La Place respecting, ib. gations of satellites, 140. GNOMON, the use of a, known to the Chinese, 9. Used by Pytheas, 27. One erected at Bologna, 58. GRAVITATION defined, 260. Its effects on the planets, 261-269. 307. And satellites, 270-277. On the moon in particular, 275-285. Illustrated, 286-292. Is diffused through the substance of the celestial bodies, 303-318.

satellite and its shadow seen on the planet at the same time, 125. Revolution of satellites on their axes, 126. Remarkable connexion among their periodic times, 127. Spots observed on him, 118. His figure and rotation, 119. His four satellites, 120. Account of these phenomena, 127. Other phenomena, 231. 233, 234, 235. Attractive power of Jupiter, 271, 272. Motion of light, from Jupiter to the earth, 374. Eclipses of his satellites very frequent, useful in finding the longitude, 760.

KATER observed a volcanic appearance in the moon,

167.

HALLEY, Dr. examines Hevelius's instruments, and makes observations along with him, 53. Makes a catalogue of the fixed stars; discovers the acceleration of the moon; points out the method of finding the distance of the sun from the transit of Venus, 59.

HARDING, discovered Juno, 69.

HARVEST moon, rises sooner than any other, 486. Reasons of this, 487-492. Goes through a course of more and less beneficial states, 493. HEAT, formula for determining time of day when greatest, 426.

Divisions

HEAVENS, general appearance of the, 80. of the starry, 589-597. HELIOCENTRIC circle defined and described, 328330.

HELIOCENTRIC latitude defined, 334.

HERSCHEL, Dr. improves reflecting telescopes, 57. Constructs very powerful ones, and discovers a new planet, with satellites, 68. His observations on Venus, 112. And on Mars, 113. Sees a satellite and its shadow both on the disk of Jupiter, 125. Discovers the double ring of Saturn, 131-133. A sixth and seventh satellite, 134. And vast numbers of nebulæ, 146. Observes eruptions of the lunar volcanoes, 167. Forms a new theory of the universe, 187. His theory of the heavens, 195203. Proposes a method of determining the parallax of the fixed stars, 586. HERSCHEL, Jun. on double stars, 71.

HERSCHEL, the new planet, so named by foreign as

tronomers, 68. See GEORGIUM SIDUS.

HIGH water, to find the time of, 484, 485.

LATITUDE of a planet defined, 334. Methods of computing, 620. Terrestrial, methods of finding, 561, 562,

LIBRATION, 109. 447.

LIGHT, progressive motion of, discovered, 58. 373. Proportion of, in the planets, 235. Velocity and alienation of, 376-387. Affords evidence of the motion of the earth, 395. 408-411. Illustrated, 411-413, Quantity of, afforded by the earth to the moon, 435. Refraction of by the atmosphere, 500-516.

LOCAL zodiac described, 336.

LONDON bridge, time of tides arriving at, 480. LONGITUDE, method of finding the, proposed by Werner, 41. By Dr. Halley, 59. Has since been carried into execution, ib. Longitude of a celestial phenomenon defined, 338. Method of computing, 620. Of places easily found in the moon, 438. Eclipses useful in determining it, 661, 664. LUNAR eclipses, two, at least, happen annually, 698. One visible, the other not, 699. Rules for calculating, 706-724. Exemplified, 772.

LUNAR tables computed, 62. When the moon's place is most correctly in the syzygies, 723, 724. LUNARIANS, appearance of the earth to the, 435, 436. 442. Have always equal day and night, 437-439.

LUNATIONS, no complete number of, finished without a fraction, 676. See MOON.

MACHINERY, astronomical, described, 762-775.
MACULE of the sun defined, 103.

MAGNITUDES of the celestial bodies, 561-588. Of the stars distinguished, 589.

phenomena, 84. Appearance through a telescope, 113. Rules for deducing his distance, 575, 576. Obliquity of axis of rotation, appearance of snow about poles of, 113.

500.

INDIANS early astronomers, 13.
INFERIOR planets defined, 227-335.
INSTRUMENTS, astronomical, described, 776-862.
JONES, constructed Greenwich mural circle, 790.
ITALY, great astronomers in, 63.

JULIAN year, excess of the, above the solar, 430.
JUNO, 116.

JUPITER, phenomena of, eclipses of, satellites of, 25. Conjunction of, with Saturn observed, 47. Occultation of, by the moon, 53. Eclipses of, by his satellites, observed by Cassini, 54. Theory of his satellites still imperfect, 62. His appearance to the eye, 86. And through a telescope, 118. A

MARSEILLES, the gnomon early used at, 27.
MATTER, universal attraction of, proved, 67. 262.
303. 318. Diversity of, in the earth, 67.262.
And planets, 320-327.

Through Has phases

MEAN distances of the planets, 233. MEDITERRANEAN sea has no tides, 482. MERCURY, appearance of, to the eye, 82. a telescope, 110. Mountains in, 111. similar to those of the moon, 231. Seen in conjunction with the sun, 345. And passing over his disk, 346. Table of occultations of, 665. MERIDIAN, rules for finding the, 517-522. To place a transit instrument in, 831-839. MICROMETER improved, 57. Necessary for measuring small angular distances, 779.

MILKY way, appearance of the, 96. Dr. Herschel discovers innumerable multitudes of stars in it; he views it by fields, 188. And supposes the sun to be sct, 192. Gauges it, 194.

MOON, acceleration of the, determined by Ebn. Younis's observations, 34. Discovered by Halley, 59. Her appearance to the eye, 78. And through a telescope, 109. Great inequalities on her surface, 165. Supposed to be mountainous; attempts made to measure their height, 166. Volcano observed in her by Kater, 167. Also by others, ib. Dr. Herschel's estimate of the height of the lunar mountains, 166. Conjectures respecting the moon's substance, 168. And her spots, 169. Atmosphere of, discovered by Ramage, Ross, and Comfield, 170. Enquiry whether the moon is inhabited, 171. Her orbit and motion, 271, 272. Illustrated, 273-292. Her conjunction, 340, 341. And peculiar phenomena, 432-449. She influences the tides, 450-482. Proportion of her

power to that of the sun in moving the sea, 459. Her appearance at the full in harvest, 486. Causes of it, 487-493. Appearance near the horizon, 494. Various reasons assigned for it, 490-500. Causes of her eclipses, 666-678. Rules for computing them, 680-724. To find her way from the 725-730. Her color, &c. during an eclipse, 754, 755. Her distance from the earth less than formerly, 758. Her various phases exemplified, 768. 770. 772. Method of delineating her visible disk, 447. Parallaxes indicate the shape of the earth, 578. MORNING star, 83.

sun,

Pro

MOTIONS of comets, 293-302. Of planets, in autecedence and consequence, defined, 336. Direct, 344. 357. And retrograde, 344-358. gressive of light, 408, 409. Annual and diurnal, of the earth, 410-413. 531. MURAL quadrant described, 781-787. MURAL circle, and its uses, described, 790-811.

NAUTICAL almanack, or Nautical Ephemeris, annually published, 62-66.

NEAP tides, cause of the, 455. 472. 476. NEBULE explained, vast numbers of, discovered by Herschel, 149. His account of them, 188-205. NEW stars, accounts of several, 90-95. NEWTON, Sir Isaac, constructs reflectors with spherical speculums, 55. Brings theoretical astronomy to perfection, 56. Determines the figure of the earth, 60. Confirms the Copernican system, and lays down the fundamental laws of motion and gravity, 221. NODES defined, 621. Method of finding when a planet is in, ib. To find the motion of the moon's, 239, 290. Line of the nodes defined, 335. NONAGESIMAL degree defined, 443. NORTH Pole star, appearance of the, 79, 80. NUTATION, natural, and cause of, 401. and tables for computing, 402-407.

Formulæ

OBLIQUITY of ecliptic, periodical variation in, 393. Method of finding, 563, 564.

OBSERVATORIES, the towers of Babel and Belus supposed to have been, and the pyramids of Egypt, probably used as such, 18.

OBSERVATORY, principal instruments in, described, 776-862.

OBSERVATORY, portable or equatorial, described, 851-862.

OCCULTATION of Jupiter by the Moon, observed, 53. 170. And of Saturn, ib.

OCTANTS of the moon described, 440.
OLBERS discovered Pallas and Vesta, 69.
OPPOSITION defined, 340. Mark of, 341.
ORBITS of the planets, inclination of the, to the eclip-
tic, 234. Of the moon, 286-291. Method of

Their appearance to the eye, 81-86. Number, 81. Apparent magnitudes and motions, 86. Their names and order, 222-227. Are all opaque bodies, 230. Their periods, distances, and eccentricities, 233. Secondary planets, 270-292. Their circles defined and described, 328-333.336. Their latitude, 334-337. Method of computing latitude of, 620. Longitude, 357. Method of computing, 620. Conjunctions, oppositions, and aspects, 340-349. Stationary appearances, 350. Motions, 355, 356. Direct, 357. Retrograde, 358. In apogee and perigee, 353. 360. Periods of return, 361-364. Methods of finding the parallax of the planets, 566-579. Their distances, 580-582. 609. 630-649. Periodic times, 630. Method of computing densities, 320-326. Comparative view of densities, 327.

354.

PLEIADES, number of stars in, 148. POLE, to find the place of, in projecting a solar eclipse, 750.

POLES of the earth, bodies heaviest when near, 397.

POND, astronomer royal, 71, 588. PRECESSION of the equinoxes, 390-392. Table and formulæ for computing effect of, 394-396. PROGRESSIVE motion of light proves the motion of the earth, 373-386.

PROJECTILE forces, supposed by Dr. Herschel to counteract the power of attraction, 207. Rendered probable by changes in the positions of stars, 208.

PROPORTIONAL distances of the planets from the sun, 233.

PROPORTIONS of light, heat, bulk, and density of the planets, 235. PYTHAGOREAN system of astronomy, taught by Philolaus, 25. And by Aristarchus, 28. Carried into Italy, Gaul, and Egypt, 26, 27. Restored by Copernicus, 42. 218.

PYTHAGORAS held comets to be of the nature of planets, 172.

QUADRANT, mural, described, 781-787. QUADRANT, portable, described, 788, 789. QUADRANT, reflecting, invented, 56.

SAMARCAND, the latitude of, determined by Ulug Beg, 35.

SATELLITES, four revolve round Jupiter, 120. Seven round Saturn, 134. And six round Herschel, 139.

SATURN, his ring discovered, 50. 128. And five of his satellites, 54. His appearance to the naked eye, 85. And through a telescope, 128. His ring described, 129, 130. Found by Dr. Herschel to be double, 131. Not changeable, 132. Period of his revolution, 133. Seven satellites, 134. Their periodical revolutions and distances from Saturn, and greatest angular distance as seen from the earth, 135. Table to determine the apparent form of the ring, and of the orbits of satellites, 137, 138. Mutual attraction between Jupiter and Saturn, 267, 268. Their power, 272.

SCHROETER, 111. 113.

SEA, the ebbing and flowing of the, causes of, 450. 483.

SEASONS, causes of the, 414. 423. Had fallen back
from the error of the Gregorian calendar, 430.
Rectified by the new style, ib. 431.
SECTOR, equatorial, described, 812. 815.
SEMITA LUMINOSA, or zodiacal light, 150-152.
SEMI Tychonic system, 217.

SEXTILE, definition and marks of, 341.
SHADOW of the earth always round, 367.

SIDERIAL days defined, 525.

SIGNS, Chinese names of the, 7. Defined, 336.
SOLAR days defined, 525.

687-693.

SOLAR eclipses, of the shadow of the penumbra in, When they can happen, 695. Number that may happen in a year, 698. Rules for computing, 731-753.

SOLAR noon, deviation of the, from the clock, 541. SOLAR systems, ours, in motion, 208. Synoptic view of 222-227.

SOLAR systems, space universally filled with, 183. SOUTHERN Constellations, 596.

STARS, fixed, catalogues of the, made by Hipparchus, 30. Ulug Beg, 35. William IV. of Hesse, 46. Tycho Brahe, 47. Flamsteed, 58. Halley, 59.

Herschel, 68. Their aberration discovered, 56. Appearances to the eye, 79-81. Most numerous

in the northern part of the heavens, 79-81. Liable to changes. 89. Their appearance through telescopes, 147, 148. Supposed to be suns, 181-186. Dr. Herschel's theory, 187. Observations of innumerable multitudes of stars, 188-205. His inferences, 205-208. Apparent changes of stars,

ib.

Are situated at an immense distance, shine by their own native light, 228. No method yet found to ascertain their distance, 584. Conjecture as to it, 585. Dr. Herschel's method, 586. Still insufficient, 587. Divisions of the stars, 589-597.

Number of, in different constellations, 595-597. Table of proper motion of, 209. Catalogue of principal, 865.

And that the

STYLE, reason for the change of, 430, 431. SUN, spots on the, discovered, 50. His parallax and distance computed, 64. His appearance to the eye, 77. And through a telescope, 98-108. His spots observed by Galileo, Scheiner, and Harriot, about the same time, 98, 99. Variety of aimensions, 100. Subject to increase and diminution, 101 -103. Their velocity and uniform motion from cast to west, 104. Other phenomena attending them 105-108. Dr. Long's account of them, 154. To find the time of their revolutions, 156, 157. Different opinions concerning them, 158. Dr. Wilson, 159-164. The sun supposed not to be in the centre of the universe, 192. Is at an immense distance, 229. Mutual gravitation between the sun and planets, 260-269. Action of the sun on the secondary planets, 270-292. Proportion of his action on both, 306-318. His conjunctions with the planets, 340-364. Is immensely larger than the earth, 370, 371. Proofs that the earth revolves round the sun, 371-413. sun revolves on his axis, 388, 389. in summer than in winter, 421. tant, 423. Reasons for the greater heat in summer, 423-426. Periods of his completing a tropical revolution, 427. Appears to fall back with respect to the stars, 428. Reasons for the apparent increase of magnitude near the horizon, 494-500. The motion of the sun illustrated by supposing a fictitious sun moving in the equator, 533-541. The sun's parallax the most important problem in astronomy, 532. Table of the sun's declination for 1824; with auxiliary table to find it for subsequent years, 550, 551. To find the moon's way from the sun in eclipses, 725-730. to calculate eclipses of the sun, 731-753. SYNOPSIS of the sun and planets, 232-235. SYSTEMS of astronomy, account of the most famous, 210-227. Of the Pythagorean, 212. Ptolemaic, 213, 214. Tychonic, 216. Semi Tychonic, 217. Cartesian, 218. And Copernican, 219-227.

He is higher And more dis

Various

To

TABLES, astronomical, published, 37. 48. 59. 62.
TELESCOPES, improvement of, 54-57.
kinds of, used by astronomers, 778. 784. 816.
point the telescope of an equatorial to a star,
861.

TELESCOPIC stars defined, 589.
TIDES, theory of, 450-483.

Causes of the spring and neap, 455. 472. 475, 476. Tides supposed in the atmosphere, 483.

TIME, methods of finding, 526-529. Equation of time, table of, 543, 544. Illustration of equation of time, 533-536. Explanation of, 537-541. TIME keeper, recommended by Frisius to determine the longitude, 45.

TRAJECTORIUM Lunare, described, 773-775. TRANSIT instrument, description and use of, 817 -850.

TRANSITS of inferior planets over the sun; intervals List of at which they may happen, 657. 663. transits of Venus, 664. Of Mercury, 665. Of Capricorn, TROPIC of Cancer described, 416. 418. TROUGHTON, maker of one of the Greenwich mural circles, 71. TWILIGHT, cause of the, 512. Method of determining the time of shortest at any place, 513-515. TYCHONIC system, account of the, 216.

VELOCITY of the spots on the sun, 104. Of comets,

greatest in their perihelion, 174. Of bodies, pheno