INDEX. 



515 



Homogeneous spheroid, its rotation, 

 51. 



Horizontal refraction, 46. Note 113. 



parallax of the moon, 59. 



Horoscope, 100. 



Humboldt, Baron, his observations on 

 the Gulf-stream, 112. Effects of the 

 rarity of the air on, 134. His observ- 

 ations on the transmission of sound, 

 150. On the temperature of mines, 

 277. On the distribution of heat, 290. 

 His botanical observations, 304. On 

 the distribution of plants, 305. On 

 the Gulf- weed, 306. His observations 

 on terrestrial magnetism, 347, 377- 



Hurricanes, laws of, 139. 



Huygens, his undulatory theory, of 

 light, 190. 



Hyperbola, 14. Note 22. 



I. 



Ibn Junis, his observations, 101. 

 Ice, its double refraction, 205. 



useful for polarising light, 212. 



impermeable by Voltaic electricity, 



339. 

 Icebergs drifted from the poles, 113. 



collision of, a cause of light, 319. 



Iceland spar, a carbonate of lime, its 



form, 202. Note 16. 

 , a doubly refracting substance, 204. 



Note 200. 



useful as an analyzing plate, 210. 



a negative crystal, 205. 



Image from a crystal with one optic 



axis, 212. Note 207. 

 from a crystal with two optic axes, 



211. Note 208. 

 Impetus, a force proportional to the 



mass and the square of the velocity of 



the striking body conjointly, 152. 

 Imponderable agents, 384. 

 Inactive lines in photographic spec 



trum, 236. 

 Inclination of planetary orbits, 11 



Note 53. 



variation of, 21. Note 72. 



Indians, the lunar tables of, 99. 

 Inequalities. See Perturbations. 

 Insects, the distribution of, 308. 



ntensity of light, 191. 



of sound, 145, 152. 



of gravitation, 5. 



nterference of waves, 110. Note 174. 

 of tides at Batsha in Tonquin, 109. 



of sound, 154. 



of light, 187, 217. Notes 193, 211. 

 nternal heat of the earth, 81, 277 <* 



seq. 



structure of the earth, 88. 

 structure of Jupiter, 33, 66. 



structure of Saturn and Mars, 66. 

 invariable plane of the solar system , 27. 



Note 80. 

 , position of, 27. Note 81. 



of the universe, 28. 



riverse square of distance, 6. Note 23. 



cube of distance, 63. Note 133. 

 ron, its magnetic properties, 348, 3?3. 



Isogeothermal lines, 289, 297- 



Isomorphism, 126. 



Isothermal lines, 296. 



Ivory, Mr., his determination of the 

 form of the terrestrial spheroid, 50, 

 55. His formulae for barometrical 

 measurements, 132. On the distribu- 

 tion of the electric fluid, 315. 



J. 



Jews used the week of seven days, 96. 

 Jovial System, the mass of, 63. 

 Julian Calendar, 96. 

 Jupiter, the compression of, J5. 



, diameter of j 25. 



, magnitude of, 63. 



, rotation of, 75. 



, precession and nutation of, 33. 



, in conjunction and opposition, 35. 



Note 96. 

 and Saturn, their theory, 29. Note 



84. 

 Jupiter's satellites, theory of, 31. 



, masses of, 31, 63. 



, orbits of, 31, 32. Notes 86, 87- 



, law in the mean motions and 



mean longitudes of, 34. 



, synodic motions of, 34. Note 92. 



, eclipses of, 34. Notes 93, 94. 

 , configuration of, 32. Note 88. 



LL2 



