AIR, 23. Mechanical laws for re- gulating its dilatation and com- pression; rarefaction of, 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.
Bode's law of planetary distances, 277.
Bodies, effect of the earth's attrac-
tion on, 128. Motion of, 233.
Rule for determining the veloc-
city of, 234. Problem of three, 315.
Borda, his invention of the prin- ciple of repetition, 104.
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. ment, 99.
Equinoxes, precession of the, 168. Uranographical effect of, 169. Excentricity of the planetary orbits, its variation, 366. Explanation of the seasons, 195.
Floating collimator, invented by captain Kater, 95. Force, centrifugal, 234.
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.
Hadley's sextant, 102.
Halley discovers the secular 'acce-
leration of the moon's mean motion, 355.
Harding, professor, 276. Herschel, sir William, his view of the physical constitution of the sun, 200.
Horizon, dip of the, explained, 18. Hour-glass, 17.
Kater's floating collimator, 95. Kepler, the first who ascertained the elliptic form of the earth's orbit, 188. His laws, and their interpretation, 263.
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.
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. 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.
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, 246. 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,
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.
Rays of light, refraction of, 26. Reflecting circle, 104. Reflection, angle of, equal to th of incidence, 91.
Refraction, 26. Of the atmosphere, 27. Effects of, to raise all the heavenly bodies higher above the horizon in appearance than they are in reality, 28. General no. tions of its amount, and law of variation, 30. Terrestrial refrac- tion, 33. Celestial refraction, 34.
Repetition, principle of, invented by Borda, 105.
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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