INDEX. 



519 



Nebulosity of comets, 402, 408. 



Nebulous stars, 433. 



Needle, the dipping, 341. 



Neptune, stability of his orbit, 25. 



, his disturbing action on Uranus, 



25, 69 et seq. 



discovered by Mr. Adams and M. 



Le Verrier, 71. 



, diameter, 71. 



his satellites, 71. 



mean distance from the sun, 72. 



mass, form, orbit, and periodic 



time, 69. 



Newton, Sir Isaac, on the attraction of 

 spheroids, 5. His discovery of gravi- 

 tation, 5. Of the laws of elliptical 

 motion, 5, 27- On the figure of a 

 fluid mass in rotation, 50. His theory 

 of the tides, 103. His analysis of light, 

 178. His theory of light, 187. His 

 rings, 193. Mensuration of his rings, 

 193. His scale of colours, 194. 



Nickel, sulphate of> its properties, 124. 

 Note 161. 



Nodal points of vibrating strings and 

 columns of air, 157 et seq. 



lines in air, 166. 



lines on cylinders, 163. 



lines on surfaces, 160. 



Nodes, ascending and descending, 12. 

 Note 55. 



motion of, 21. Note 73. 



connected with the inclination, 22. 



Norman, Robert, discovers the mag- 

 netic dip, 348. 



Nutation of earth's axis, 91. Note 144. 



of lunar orbit, 9. Note 35. 



, reciprocal, of earth and lunar or- 

 bit, 9. Note 33. 



, effects of, 92. 



O. 



Oblate spheroid, 5. Note 9. 

 Obliquity of the ecliptic, 11, 26. Note 

 46. 



, its variation and limits, 26. 



Occultation of planets and stars, 47, 419. 

 Ocean, tides of, 102. 



, effects of, on gravitation, 58. 



, density of, 58. 



Ocean, mean depth of, 130. 



, stability of, 111. 



, currents in, 112. 



Octahedrons, 123. Notes 160, 165. 

 Oersted, Professor, his discovery of 



electro-magnetism, 361. 

 Olbers, M., his observations of Biela's 



comet , 396 ; and of the comet of 181 1 , 



403. 

 Olmsted, Professor, on the shooting 



stars of the 13th of November, 449, 



450. 



Opposition, 34. Note 96. 

 Optic axis of a crystal, 204. Note 202. 

 Orbit of a planet, 10. 



of comets, 387, 399. 



of binary systems, 416 et seq. 



of celestial bodies, 411. 



elements of an , 12, 66. 



Ordinary refraction, 171. Note 184. 



ray, 202. 



Oscillations, 3. Note 4. 



of the ocean, 102. 



of the pendulum, 56. Note 127. 



of the atmosphere, 127, 134. 



P. 



Pacific Ocean, the origin of the tides, 



108. 



Pallas, diameter of, 25. 

 Parabola, 6. Note 22. 

 Parabolic elements, 387, 388. 

 Parallactic motion, 426. 

 Parallax, 59. Notes 128, 129. 



, horizontal, 59. 



of the Sun, Mars, and Venus, 60, 



61. 



of the Moon, 59. 



Parallel directions, 16. Note 62. 



of latitude, 298. Note 11. 



Parathermic rays of solar spectrum, 265. 

 Parry, Sir Edward, his journey on the 



ice, 113. On the cold at Melville 



Island, 276. On the temperature of 



the Arctic seas, 297- 

 Particles of matter, 5,114. Note 6. 



subject to gravitation, 5, 119. 



, size of, 120. 



, relative weights of, 121. 



, form of, 123. 



