INDEX. 



497 



HERSCHEL. 



395, 396 ; periodic time of y Vir- 

 ginis determined by, 398 ; eclipse of 

 a double star observed, ib. ; binary 

 system discovered, 400 ; remarks 

 on the motions of the stars, 405* ; 

 nebulas resolvable into stars, 507. 

 Herschel, Sir John, approximate periods 

 of satellites ascertained by, 33 ; 

 thickness of Saturn's ring computed, 

 67 ; observations of, on seasons, 

 74 ; difficulty of varying time, in 

 observations at distances, obviated 

 by, 86 ; tenuity of atmospheric 

 air demonstrated, 110; rapid de- 

 crease of density in the atmosphere, 

 118 ; mean temperature of space 

 computed by, 119; height of Etna 

 measured, 120 ; his explanation 

 of anomalies in atmospheric phe- 

 nomena, ib. ; quotation from, on 

 the transmission of sound, 136 ; 

 observations of, on thunder, 138; 

 remarks on the absorption of light 

 by coloured media, 175, 176 ; on 

 polarization of light, 179; experi- 

 mentalising apparatus, 188$ dis- 

 covery of epipolic light, 197 ; dis- 

 coveries in photography, 205, 206 ; 

 analysis of the solar spectrum, disco- 

 vert of its chemical properties, 207- 

 219 ; his theory of volcanic action, 

 235-237 ; observations showing the 

 maximum of heating influence of 

 the solar rays, 238 ; theory of the 

 original distribution of plants, 254 ; 

 divergent flame of a comet observed 

 by, 364 ; remarks on the possible 

 destruction of the solar system, 

 372 ; causes assigned by, for con- 

 traction of diameter in comets, 

 378 ; comparative lustre of stars 

 measured by, 384, 385 ; the Milky 

 Way described, 385, 386; num- 

 ber of stars in a group of the 

 Milky Way computed, 387 ; va- 

 riable star discovered, 391 ; re- 

 marks of, on the nature of the 

 fixed stars, 392 ; variable stars 

 discovered by, 393 ; remarks on 

 variable stars, 394 ; star missed 

 by, 395 ; double stars discovered, 

 396; eclipse of a doable star ob- 



HORIZON. 



served, 397 ; orbits determined, 

 398, 399 ; observations on colours 

 of double stars, 401 ; light of 

 a Centauri compared with the 

 moon's by, 404 ; light of the fixed 

 stars calculated, ib. ; observations 

 on nebulae corrected, 407 ; cata- 

 logues of nebulae, 408 ; nebula? 

 discovered by, 409 ; annular nebula 

 described, 410 ; magnitude of plane- 

 tary nebulas computed, 412 ; glo- 

 bular nebulous cluster described, 

 413 ; law of gravitation ascribed 

 to nebulae, 416 ; nebula round 

 v Argus described, 418 ; his work 

 on Nebulae, 419. 



Herschel, Miss, Encke's comet seen by, 

 365 ; catalogue of nebulae, 407. 



Hevelius, divergent flames of a comet 

 described by, 364 ; contraction in 

 diameter of comets observed, 377 ; 

 phases in comets observed, 380. 



Hieroglyphics interpreted by astro- 

 nomy, 89. 



Himalaya, the, inappreciable effect of, 

 on the globe's surface, 6 ; singular 

 effect of refraction on, 156 ; cause 

 of greater elevation of the snow- 

 line on the northern side of, 241 ; 

 flora of, 250. 



Hind, Mr., comet's orbit computed 

 by, 370, 371 ; observations of, on 

 Donati's comet, 379 ; variable stars 

 discovered by, 391 ; vanishing star 

 discovered, 393 ; his belief in 

 planetary systems, 394. 



Hindostan, the tidal wave striking on 

 its coasts, 94. 



Hipparchus, precession discovered by, 

 change of seasons since his age, 80 ; 

 phenomenon suggesting his cata- 

 logue of the stars', 392. 



History corroborated and corrected 

 by astronomy, 87, 89. 



Hoar-frost, cause of, 269. 



Holtzman, M., opinion of, with re- 

 gard to the vibrations of polarized 

 light, 223. 



Hooghly, the, bore of, 94. 



Horizon, effects produced by the 

 denser stratum of air in, 157,, 

 158. 



