AIB, 23. Mechanical laws for re-
gulating its dilatation and com. pression ; rarefaction of, 24. Density of, 25. Refractive power
of, affected by its moisture, 29. Angle of reflexion equal to that of
incidence, 91. Angles, measurement of, 82. Anomalistic and tropical years,
205. Apparent diurnal motion of the
heavenly bodies explained, 41. Apsides, their motion illustrated,
361. Astronomical instruments, 64.
Practical difficulties in the con. struction of, 65. Observations
in general, 66. Astronomy, 1. General notions
concerning the science, 9. Atmosphere, 25. Refractive power
of the, 26. General notions of its amount, and law of variation, 30.
Reflective power of, 32. Attraction, magnetic and electric, 236. Of spheres, 237. Solar at
traction, 239. Azimuth and altitude instruments,
100.
Calendar, 408. Gregorian, 410.
Julian, 412. Cause and effect, 232. Celestial refraction, 34. Maps, 157.
Construction of, by observations on right ascension and declina. tion, 158. Objects divided into fixed and erratic, 161. Longi-
tudes and latitudes, 167. Centrifugal force, 121. Chronometers, 77. Circles, co-ordinate, 97. Clairaut, 128. Clepsydras, 77. Clocks, 77. Comets, their number, 301. Their
tails, 302. Their constitution, 303. Their orbits, 305. Their predicted returns; Encke's, 308. Biela's, 309. Their dimensions,
311. Copernican explanation of the
sun's apparent motion, 194.
Dates, astronomical means of fix.
ing, 414. Day, solar, civil measure of time,
408. Sidereal, 409. Definitions of various terms em..
ployed in astronomy, 54. Diurnal or geocentric parallax, 189.
Earth, the, one of the principal
objects of the astronomer's con. sideration; opinions of the an. cients concerning, 10. Real and apparent motion of, explained, 12. Form and magnitude of, 14. Its apparent diameter, 16. A diagram, elucidating the circular
form of, 17. Effect of the curva- ture of, 19. Diurnal rotation of, 38. Poles of, 47. Figure of, 108. Means of determining with accu. racy the dimensions of the whole or any part of, explained, 109. Meridional section of, 115. Ex. act dimensions of, 117. Its form that of equilibrium, modified by centrifugal force, 120. Local variation of gravity on its sur- face, 123. Effects of the earth's rotation, 127. Correction for the sphericity of, 149. The point of the earth's axis, 170. Conical movements of, 171. Mutation of, 172. Parallelism of, 195. Pro. portion of its mass to that of
the sun, 290. Ecliptic, the, 164. Its position among the stars, 165. Poles of, 166. Plane of its secular varia.
tion, 328. Elliptic motion, laws of, 187. Equations for precession and nuta-
tion, 175. Equatorial or parallactic instru. Equinoxes, precession of the, 168.
Uranographical effect of, 169. Excentricity of the planetary orbits,
its variation, 366. Explanation of the seasons, 195.
Equant, 99. recessiorect of, orbits,
Lalande, his ideas of the spots on
the sun, 209. Laplace accounts for the secular
acceleration of the moon, 355. Latitude, 57. Length of a degree
of, 111. Level, description and use of, 92. Light, aberration of, 177. Urano- graphical effect of, 179. Its velo- city proved by eclipses of Jupi.
ter's satellites, 297. Longitudes, determination of, by
astronomical observation, 135. Differences found by chrono. meters, 137. Determined by
telegraphic signals, 139. Lunar eclipses, 225.
Gay-Lussac, his aeronautic expe.
dition, 23. Galileo discovers Jupiter's satel.
lites, 296. Geographical latitudes determined,
133. Geography, outline of, so far as it
is to be considered a part of
astronomy, 107. Gravitation, law of universal, 233. Gravity, local, variation of, 123.
Statical measure of, 125. Dyna. mical measure of, 126. Terres- trial, 233. Diminution of, at the moon, 235. Solar, 240.
Maclaurin, 128. Maps, construction of, 147. Pro-
jections chiefly used in, 151. The orthographic, stereographic, and
Mercator's, 151. Menstrual equation, 289. Mercators', projection of the
sphere, 153. Mercury, the most reflective fluid
known, 91. Meridian, or transit circle, for as.
certaining the right ascensions and polar distances of objects,
92. Microscope, compound, 84. Milky way, 163. 375. Moon, the, its sidereal period; its
apparent diameter, 213. Its paral. lax, distance, and real diameter, 214 The form of its orbit, like that of the sun, is elliptic, but considerably more excentric; the first approximation to its orbit,
215. Motions of the nodes of, 216. Occultations of, 217. Phases of, 222. Its synodical periods, 223. Revolutions of the apsides of, 227. Physical constitution of, 228. Its mountains, 229. Its atmosphere, 230. Rotation of; libration of, 231. Diminution of gravity at the; distance of it from the earth, 235. Its gravity towards the earth; towards the sun, 289. Its motion disturbed by the sun's attraction, 354. Ac- celeration of its mean motion;
accounted for by Laplace, 355. Motion, parallactic, 13. Appear.
ances resulting from diurnal motion, 14. Real and apparent motion of the earth described, 172. Of bodies, 233. Laws of elliptic motion, 238. Orbit of the earth round the sun in accord. ance with these laws, 239. Mural circle, 89.
256. Superior planets, 259. Their distances and periods, 260. Method for determining their sidereal periods and distances, 262. Elliptic elements of the planetary orbits, 265. Their heliocentric and geocentric places, 272. The four ultra. zodiacal planets, discovered in 1801, 276. The physical peculi. arities, and probable condition of the several planets, 277. Their apparent and real diameters, 280. Their periods unalterable, 358. Their masses discovered inde- pendently of satellites, 371. Polar and horizontal points, 91. Pole star, 43. Situation of, 89. Precession, its physical causes,
329. Projectiles, motion of, 233. Cur.
vilinear path of, 234.
Parallax, 48. Pendulum, 126. Perturbations, 313. Of the planet-
ary orbits, 340. Planet, method of ascertaining its mass, compared with that of the
sun, when it has a satellite, 290. Planets, the, 243. Apparent motion
of, 244. Their stations and re- trogradations, 245. The sun their natural center of motion, 216. Their apparent diameters and distances from the sun, 247. Motions of the inferior planets ; transits of, 249. Elongations of, 251. Their sidereal periods, 252. Synodical revolutions of, 253. Phases of Mercury and Mars, 255, Transits of Venus explained,
Satellites, 288. Their motions
round their primary analogous to those of the latter round the sun, 291. Of Jupiter, 292. Their
masses, 372. Saturn, his satellites, 298. Sea, action of the on the land,
121. Seasons, explanation of the, 195. Sextant and reflecting circle, 102
Its optical property, 163. Sidereal clock, 59. Sidereal year, 165. Sidereal time, reckoned by the
diurnal motion of the stars, 59. Sirius, its intrinsic brilliancy, 379. Solar eclipses, 218. System, 243. Sphere, celestial, 35. Projections
of, 151. Stars, 49. Distance of, from the
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