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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.

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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, 185.
Differences found by chrono
meters, 137. Determined by
telegraphic signals, 139.
Lunar eclipses, 225.

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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.

N.

Ac-

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Parallax, 48.
Pendulum, 126.

P.

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.

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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

earth, 50. Sidereal time reck-
oned by the diurnal motion of
the, 59. Visible by day, 63.
Fixed and erratic, 161. Their
relative magnitude; infinite
number, 373. Their distribution
Their
in the heavens, 375.
distances, 376. The centers of
planetary systems, 380. Period-
ical, 381. Temporary, 383.
Double, 385. Binary, 390. Their
orbits elliptic, 391. Their colours,
394. Their proper motions, 395.
Clusters of, 398. Globular clus-
ters of, 400. Irregular clusters
of, 402. Nebulous, 404.
Sun, apparent motion of the, not
uniform, 184. Its apparent dia-
meter also variable, 185.
Its
orbit not circular, but elliptical,
186. Variation of its distance,
187. Its apparent annual mo.
tion, 188. Parallax of, 189. Its
distance and magnitude, 192.
Dimensions and rotation of, 193.
Mean and true longitude of, 202.
Equation of its center, 203. Phy-
sical constitution of, 207. Den-
sity of; force of gravity on its
surface, 239. The disturbing
effect of, on the moon's motion,
240.

T.

Table, exhibiting degrees in dif
ferent latitudes, expressed in
British standard feet, as result-
ing from actual measurement,
113.
Telescope, 85. Application of, the
grand source of all the precision
of modern astronomy, 86. Dif-

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