512 



INDEX. 



Elements of parabolic orbits, 388. 



Ellipse, a conic section, 6. Note 24. 

 , the limits of, 216. Note 210. 



Ellipsoid, oblate and prolate, 5. Note 9. 



of revolution, 51. Note 119. 



, terrestrial, 57. 



Elliptical or true motion, 10. Note 

 39. 



Encke, Professor, his determination of 

 the orbit and motion of the comet 

 named after him, 394. Of its accele- 

 ration, ib. And of the orbit of the 

 star 70 Ophiuchi, 419. 



Epoch, the, 12. 



, longitude of the, 12. 



Equation of the centre, 11, 40. Note 

 48. 



of time, 94. 



Equator, 5. Note 11. 



, dynamical, 343. 



Equilibrium, stable and unstable, 14. 

 Note 60. 



Equinoctial, 11. Note 46. 



Equinoxes, 11. Note 46. 



Era, the Christian, 96. 



Eratosthenes measures a degree of the 

 meridian between Syene and Alex- 

 andria, 55. 



Ether, its nature, 197. 



Ethereal medium, 25, 115, 197. 



, temperature of, 274. 



, resistance of, 385. 



, vibrations of, 197, 223. 



, elasticity of, 36. Note 99. 



Eudoxus describes the state of the 

 heavens about the time of the Trojan 

 war, 100. 



Evection, a lunar inequality, 40. Note 

 103. 



Excentricity, 11. Note 52. 



, secular variation of the, 20. 



of the orbits of Jupiter's satellites, 



32. 



of lunar orbit constant, 42. 



of the terrestrial orbit diminishing, 



22. . 



of the terrestrial orbit, its variation 



the cause of the acceleration in the 

 moon's mean motion, 43. 



Expansion of substances by heat, 256. 



Extraordinary refraction, 174. 



ray and image, 200. 



F. 



Fall of heavy bodies, 7, 56. 



at the surface of the sun and 

 planets, 65. 



Fall of meteorites, 446. 



Faraday, Dr., reduces the gases to a 

 liquid state, 118. His causes of af- 

 finity, 122. His experiments on spon- 

 taneous combustion, ib. His theory 

 of the aurora, 329. His views of elec- 

 tro-chemical decomposition, 338. His 

 experiments on the transmission of 

 electricity, 339. He produces rotatory 

 motion by the electric force, 356. 

 His experiments on magneto-electri- 

 city, 365, 370. He proves the identity 

 of the electric and magnetic fluids, 

 367, 368. His discovery of the dia- 

 magnetic properties of matter, 369. 

 His explanation of electricity evolved 

 by rotation, 371. His classification of 

 magnetic substances, 373. His ex- 

 periments on the induction of terres- 

 trial magnetism, 379. He supposes 

 rotation a cause of electric currents 

 in the earth, 380. On the evolution 

 of electric currents, and identity of 

 the different kinds of electricity, 383. 



Faye's comet, 389. 



Fiedler, Dr., his fulgorites, 322. 



Figure of the earth. See Earth. 



Fluids, the undulations of, 110. Note 

 156. 



, compression of, 118. 



, capillary attraction of, 130. 



Focal distance, 6. Note 22. 



length of a lens. Note 196. 



Foci of an ellipse, 6. Note 22. 



of magnetic intensity, 343, 345. 



Forbes, Professor, his experiments 

 during the annular eclipse of the sun, 

 183. His experiments on polarization 

 of heat, 249. On the heat of moon- 

 light, 274. 



Force, the unknown cause of motion, 5 

 et passim. 



proportional to velocity, 9. Note 



37- 



, gravitating, 7. See Gravitation. 



, centrifugal, 6, 50. Notes 18, 117. 



, molecular, 114. 



