514 



INDEX. 



Harmonic divisions of a column of air, ' 



159. 



Harmony, 158. 

 Harris, Mr. Snow, his experiments on 



electricity, 315 et seq. 

 Harrison, Mr., his compensation pen- 

 dulum, 257- 

 Hearing, the extent of, f47. 



, experiments of Dr. Wollaston on, 



146. 



, experiments of M. Savart on, 147. 



Heat, theory of, 238. 



, transmission of, 240. 



of various kinds, 242. 



, solar, transmission of, 245. 



, maximum point of, in solar spec- 

 trum, 247 



, polarization of, 248. 



, analogy between light and, 251. 



, radiant, 253. 



, expansion by, 256. 



, propagation of, 258. 



, latent, 260. 



, application of, 263. 



supposed to consist of undulations 



of the ethereal medium, 264. 



, solar, 265 et seq . 



, quantity of solar, 288. 



, quantity of solar lost and gained 



by the earth, invariable, 298. 



, central, of earth, 277 et seq. 



, superficial, of earth, 289. 



, distribution of, 289. 



, influence of, on vegetation, 300. 



Height of atmosphere, 133. 



of tides, 108. 



of mountains, 8. 



Heliacal rising, 96. Note 146. 

 Helix, circular and elliptical, 215. 

 Henderson, Mr., on the parallax of 



Sirius, 427. 



Henry, Professor, his temporary mag- 

 net, 359. 



Herschel, Sir William, his discovery of 

 the satellites of Saturn and Uranus, 

 37; of the rotation of Jupiter's satel- 

 lites, 79; of the calorific rays of the 

 solar spectrum, 230. His observations 

 on the point of maximum heat in the 

 solar spectrum, 247- His account of 

 the nucleus of the comet of 1811 , 402. 

 Number of fixed stars he saw in one 



hour, 414. His catalogue of double 

 stars, and discovery of the binary 

 systems, 416. His observations of if 

 Serpentarii and of Orionis, 420. 

 Discovers the orbital motions of the 

 double stars, 426. On the motion of 

 the solar system, 431. On the nebulae, 

 433. His sidereal astronomy, 445. 

 Herschel, Sir John, his estimation of 

 the thickness of Jupiter's ring, 76. 

 He ascribes the decrease of the earth's 

 temperature to the secular variation 

 of the excentricity of the earth's or- 

 bit, 84. On the decrease of heat in 

 the northern hemisphere, ib. Pro- 

 poses the use of equinoctial time, 97. 

 His remarks on the clearness of sound 

 during the night, 151. On thunder, 

 153. His discovery of two new pris- 

 matic colours, 181. His argument in 

 favour of the undulatory theory of 

 light, 196. On the phenomena of 

 polarization of light, 200. On polar- 

 ising apparatus, 212. His discoveries 

 in the photographic spectrum, 227. 

 On the discontinuity of calorific spec- 

 trum, 238. His discovery of the pa- 

 rathermic rays, 265. His theory of 

 volcanic action, 285. Supposes the 

 ether may be in motion, 401. On the 

 contraction of the heads of comets, 

 408. His description of the Milky 

 Way in the southern hemisphere, 

 414 et seq. He misses a star, 422. His 

 account of the star Algol, 423. De- 

 termines the orbit of y Virginis, 419. 

 Adds to the catalogue of double stars, 

 ib. On the colour of the stars, 421. 

 On variable stars, 424. On clusters 

 of stars, 438. On the nebulae, 434 et 

 seq. 



Herschel, Miss Caroline, her observa- 

 tions of Encke's comet, 393. Her 

 catalogue of nebulae, 434. 

 Hevelius first noticed the contraction 

 of comets in approaching the sun, 

 407.' Thought he saw the phases of a 

 comet, 409. His observations of Hal- 

 ley's comet, 392. 

 Hipparchus discovers precession, 90, 



His catalogue of stars, 422. 

 Homogeneous light, 178- 



