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AIR, 23. Mechanical laws for re Calendar, 408. Gregorian, 410.
gulating its dilatation and com. Julian, 412.
of, affected by its moisture, 29. Construction of, by observations
tion, 158. Objects divided into
fixed and erratic, 161. Longi.
Centrifugal force, 121.
heavenly bodies explained, 41. Circles, co-ordinate, 97.
Practical difficulties in the con. Comets, their number, 301. Their
303. Their orbits, 305. Their
Biela's, 309. Their dimensions,
of the, 26. General notions of its Copernican explanation of the
Reflective power of, 32.
408. Sidereal, 409.
Definitions of various terms em-
Diurnal or geocentric parallax, 189.
apparent motion of, explained,
Its apparent diameter, 16. A
diagram, elucidating the circular
215. Motions of the nodes of,
accounted for by Laplace, 355.
ances resulting from diurnal
ance with these laws, 239.
256. Superior planets, 259. Their
pendently of satellites, 371.
vilinear path of, 234.
ary orbits, 340.
sun, when it has a satellite, 290.
of, 244. Their stations and re-
Satellites, 288. Their motions
round their primary analogous
Its optical property, 168.
diurnal motion of the stars, 59.
earth, 50. Sidereal time reckoned by the diurnal motion of the, 59. Visible by day, 63. Fixed and erratic, 161. Their relative magnitude ; infinite number, 373. Their distribution in the heavens, 375. Their 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. Physical constitution of, 207. Density of; force of gravity on its surface, 239. The disturbing effect of, on the moon's motion, 240.
ferences of declination measured by, 87. Terrestrial refraction, 33. Theodolite, construction of the,
149. Tides, their physical cause, 335. Time, measurement of, 77. Its
measures, 408. Trade winds, 128. Explanation of
this phenomenon, 129. Compens. ation of, 131. Transit instrument, 75. Trigonometrical survey, 147. Tropical and anomalistic years,
205. Twilight caused by the reflection of the sun and the moon on the atmosphere, 31.
Uranographical problems, 181.
Variations, periodic and secular,
Table, exhibiting degrees in dif
Year," tropical, the civil measure ferent latitudes, expressed in
of time, 408. Sidereal, 409. British standard feet, as resulting from actual measurement,
113. Telescope, 85. Application of, the grand source of all the precision Zodiac, the, 163, of modern astronomy, 86. Dif. 1 Zodiacal light, 407.
BY SIR JOHN F. W. HERSCHEL, KNT. GUELP.
F.R.S. L. & E. M.R.I.A. F.R.A.S. F.G.S. M.C.U.P.S. CORRESPONDENT OF THE ROYAL ACADEMY OF SCIENCES OF PARIS, AND
OTHER FOREIGN SCIENTIFIC INSTITUTIONS.