INDEX. 



521 



VAPOUR. 

 Vapour, formation and dispersion of, 



269, 270 ; force developing, 277. 

 Variable stars, periodic fluctuation of 

 lustre in, 390, 391 ; new, appear- 

 ing and vanishing, 392, 394; miss- 

 ing, 395. 



Variables, region of the, 122. 

 Vegetation, effect of, in lowering tem- 

 perature, 243 ; the two requisites 

 for, 248 ; strength and vitality of, 

 249 ; chemical action of light in- 

 fluencing, ib. ; laws of its distribu- 

 tion, 249-252 ; distribution of 

 marine, 252, 253 ; theories of 

 specific diversity of original distri- 

 bution of, 253, 254. 

 Veitch, James, comet with luminous 



rings discovered by, 374, 375. 

 Venus, zone of instability between 

 the sun and, 21 ; perturbation in 

 the mean motion of the earth and, 

 26 ; eclipsing Mercury, 42 ; tran- 

 sits of, parallaxes calculated from, 

 52, 53 ; astronomical tables of, 63 ; 

 climate, 226. 

 Vernal equinox, planetary motions 



estimated from, 9. 

 Vesta, astronomical tables of, 63 ; no 



atmosphere surrounding, 226. 

 Vesuvius, revived volcanic action of, 



234. 

 Vibrating plates used in experiments 



on musical sound, 144, 147. 

 Vibrations of the air producing sound, 

 129; in music, 131 ; number made by 

 the human voice in a second, 132. 

 of the ether in natural and po- 

 larized light, 193 ; in fluorescence 

 of light, 196 ; plane of, in polarized 

 light, 223. 

 Vico, Padre de, comet discovered by, 



370. 

 Vienna, observations on comets from, 



370. 

 Vincent, St., revival of an extinct 



volcano in, 234. 

 Virginia, daguerreotyped spectral 



image obtained in, 213. 

 Virgo, planetary conjunction between 

 Libra and, 42 ; variable star in, 

 392; star vanished from, 395; 

 nebulous zone passing, 416, 417. 



WATER. 



Viviers, transit of a comet across the 

 sun observed from, 374. 



Volcanic regions of the globe, 232 ; 

 annual number of eruptions, 233 ; 

 celebrated eruptions, ib. ; earth- 

 quakes caused by, 234 ; supposed 

 causes of action, 235 ; Sir John 

 Herschel's theory, 235-237. 



Volta, Professor, electricity rendered 

 manageable by, 297 ; the world's 

 debt to, 328. 



Voltaic electricity, first suggestions 

 of, 297 ; theory of the transmission 

 of, 298 ; construction of the bat- 

 tery, 298, 299 ; theory of its pro- 

 duction, 300 ; characteristic pro- 

 perties, 300, 301 ; action of, gene- 

 rating heat and light, 301-303 ; 

 arc, experiments, 303-305 ; the, 

 discharge oxidizing silver, 305, 

 306 ; stratified light, 306, 307 ; 

 chemical decomposition effected by 

 agency of, 307, 308 ; crystalliza- 

 tion, 308 ; an agent in the fine arts, 

 309 ; conductors of, ib. ; relations 

 of heat and, 310 ; fish producing 

 effects of, 310, 311; science sug- 

 gested by its influence on a mag- 

 netized needle, 312 ; rotation ef- 

 fected by, 313, 314; inducing 

 magnetism, 314, 315; distinction 

 between static electricity and, 317; 

 unvarying dual force of, 334. 



Voltaic pile, the, invention of, 297 ; 

 perfected, 298-300. 



Vortices, molecular, theory of, 104. 



Vosges mountains, temperature of 

 mines in the, 228. 



Vulpecula, nebula in, 409. 



WARDHUS, transit of Venus observed 

 at, 53. 



Watches, irregular action of, corrected 

 by the laws of unequal expansion, 

 272. 



Water, constituent parts of, 111 ; 

 boiling point of, an estimate of 

 mountain heights, 120 ; as a me- 

 dium for sound, 135 ; light polar- 

 ized circularly by, 194 ; experiment 

 deciding the velocity of light in, 

 202 ; law of expansion of, 271 ; 



