490 



PHYSICAL SCIENCES. 



EARTHQUAKES. 



effect of its collision with a comet, 

 368; nearest approach of comets 

 to, 369 ; passage of light from a, 

 Centauri to, 388 ; theories of me- 

 teors falling on, 421-423. 



Earthquakes in South America, 234. 



Earths, decomposed by voltaic elec- 

 tricity, 307. 



Eastern coasts, cause of their colder 

 climates, 244. 



Ebb, see Tides. 



Eboulemens of mountains in Switzer- 

 land, cause of, 271. 



Echoes, theory of their origin, 137, 

 138. 



Eclipses, lunar, accelerated revolu- 

 tions proved by observations of, 36 ; 

 observations of, confirming results 

 of analysis, 38 ; principle regulating 

 their return, 39 ; refraction of rays 

 by the terrestrial atmosphere, 40. 



, solar, 40 ; effects of light in, 41. 



, planetary, 42 ; the solar at- 

 mosphere visible in, 224 ; of double 

 stars, 397, 398. 



Ecliptic, the, forming the equinoxes, 

 9 ; latitude reckoned from the plane 

 of, ib. ; deviations of planetary 

 orbits from, 10 ; forces affecting 

 their position towards, 15 ; their 

 compensated and uncom pen sated 

 variations to the plane of, 18, 19 ; 

 secular variation in the plane of, 

 2 i ; orbits of satellites, nearly per- 

 pendicular to, 33 ; lunar motions 

 towards, 35 ; inclination of the 

 sun's plane of rotation to, 65 ; in- 

 clination of the plane of Saturn's 

 rings, 67 ; inclination of the plane 

 of the terrestrial equator, 79 ; ten- 

 dency of its plane to coincide with 

 the equatorial, ib. ; retrograde mo- 

 tion of the equinoctial points on, 

 80 ; obliquity of, affecting the du- 

 ration of time, 84. 



Edinburgh, comparatively equal mean 

 annual temperature of, 246. 



Egypt, hieroglyphic manuscript from, 

 interpreted by astronomy, 89. 



Egyptians, the civil year of, 85. 



Elastic impact, the foundation of dy- 

 namical theories, 357. 



ELLIPSES. 



Elasticity, property of, resisting com- 

 pression, 105. 



Electric telegraphs, experiment sug- 

 gesting the principle of, 323 ; con- 

 struction of, 325-328. 



Electricity assumed as the medium 

 attracting particles of matter, 103, 

 104 ; identical with chemical affi- 

 nity, 110; in composition and 

 decomposition, subject to laws of 

 definite proportion, 112 ; influenc- 

 ing winds, 125; its comparative 

 velocity, 138 ; producing phos- 

 phorescence, 217 ; communicated to 

 metal plates by juxtaposition, 220 ; 

 impressions traced on glass by, 221 ; 

 rays exciting, 223 ; a dual power, 

 282; modes of exciting by disturbing 

 equilibrium, 282-284; transmis- 

 sion of, 284, 285 ; transmission by 

 induction, 285,286 ; laws of attrac- 

 tion and repulsion determining in- 

 tensity of, 286-288 ; heat and light 

 produced by, 288 ; velocity of, 

 289 ; experiment determining its 

 velocity, 290 ; development of, in 

 the atmosphere, 291, 292; phos- 

 phorescence excited by, 294 ; Vol- 

 taic, see Voltaic ; conduction of 

 static, contrasted with Voltaic, 309 ; 

 laws of action in, distinguishing it 

 from Voltaic, 317 ; relation be- 

 tween polarized light and, 320; 

 experiment establishing its identity 

 with magnetism, 322, 323; tele- 

 graphs working by, 323-328 ; pro- 

 duced by rotation, 330, 331 ; 

 thermo, 332, 333 ; exact balance of 

 its dual force, 334 ; points of 

 analogy between magnetism and, 

 340, 341 ; causing convulsions in 

 comets, 375. 



Electro-dynamics, see Dynamics. 



magnetism, see Magnetism. 



Elements, the three terrestrial mag- 

 netic, 343 ; variations in, ib. ; 

 storms affecting, 344. 



Elevation, effect of, on temperature, 

 240-242 ; on vegetation, 250. 



Ellipses, described by .planets, 5 ; 

 paths of planets describing, 10 ; 

 preventing compensation of dis- 



