456 



Nutation, reciprocal, of earth and 



lunar orbit, 7. Note 33. 

 , effects of, 73. 



O. 



Oblate spheroid, 4. Note 9. 

 Obliquity of the ecliptic, 9, 21. Note 



46. 



, its variation and limits, 23. 



Occupation of planets and stars, 41. ! 

 Ocean, tides of, 85. 



, effects of, on gravitation, 50. 



, density of, 50. 



, mean depth of, 86. 



, stability of, 93. 



, currents in, 95. 



Octahedrons, 105. Notes 160, 165. 

 Oersted, Professor, his discovery of 



electro-magnetism, 319. 

 Olbers, M., his observations of Bie- 



la's cornet, 347 ; and of the comet 



of 1811, 353. 

 Olmsted, Professor, on the shooting 



stars of the 13th of November, 385. 

 Opposition, 29. Note 96. 

 Optic axis of a crystal, 177. Note 



202. 

 Orbit of a plane), 8. 



of comets, 339. 



of binary systems, 365 et seq. 



of celestial bodies, 360. 



, elements of an, 10, 57. 

 Ordinary refraction, 148. Note 184. 



ray, 175. 



Oscillations, 3. Note 4. 



of the ocean, 86. 



of the pendulum, 49. Note 127. 



of the atmosphere, 115. 



P. 



Pacific Ocean, the origin of the tides, 



91. 



Pallas, its size, 56. 

 Parabola, 5. Note 22. 

 Parabolic elements, 339. 

 Parallactic motion, 370. 

 Parallax, 51. Notes 128, 129. 



, horizontal, 51. 



of the sun, Mars, and Venus, 



52, 53. 



of the moon, 51. 



, annual, 53, 371. 



Parallel directions, 14. Note 62. 



of latitude, 47. Note 11. 



Parathermic rays of solar spectrum, 



231 

 Parry, Sir Edward, his journey on 



the ice, 95. On the cold at Mel- 

 ville Island, 241. On the tem- 

 perature of the Arctic seas, 260. 



Particles of matter, 4, 96. Note 6. 



subject to gravitation, 4, 100. 



, size of, 101. 



, relative weights of, 102. 



, form of, 104. 



Pendulum, 32, 49. Note 100. 



, its variation discovered, 50. 



Penumbra, 39. Note 111. 



Perigee, lunar, 34. Note 102. 



, variation of, 37. 



, variation of solar. 82. Note 



147. 



Perihelion, 10. Note 57. 



, secular variation of, 16. Note 



64. 



Periodic inequalities of the planets, 

 13. 



of Jupiter's satellites, 27. 



of the moon, 34. 



times, 5, 9. 



, proportional to cubes of mean 



distances, 5. Note 20. 



Periodicity of the planetarv pertur- 

 bations, 20. 



Periods of rotation of the celestial 

 bodies, 61 ct seq. 



Perkins, Mr., his experiments on the 

 compressibility of matter, 74. 



Peron and Lesueur, MM., on the dis- 

 tribution of marine animals, 269. 



Perturbations of the planets, peri- 

 odic and secular, 12, 13. 



expressed in sines and cosines 



of circular arcs, 20. Note 7(5. 



of Jupiter and Saturn, 24. 



of Venus and the earth, 25. 



of Jupiter's satellites, 27. 



of the moon, 33, 34. 



of comets, 338. 



Phases of the moon, 38. 



Phosphorescence, 28(5. 



Phosphorescent action of solar spec- 

 trum, 286. 



Photographic rays of solar spectrum, 

 194 ct seq. 



pictures, 197. 



Plane of ecliptic, 9. 



, its secular variation, 21. 



Planetary motions. 8, 13. 



Planets move in conic sections, o. 



, their forms, 4, 



, atmospheres of, 238. 



, constitution of, 240. 



Plants, their distribution, 262 ct seq 



Plateau, M., on complementary col 

 ors, 160. 



