VAPOUR.

WATER.
Vapour, formation and dispersion of, Viviers, transit of a comet across the

269, 270; force developing, 277. sun observed from, 374.
Variable stars, periodic fluctuation of Volcanic regions of the globe, 232;
lustre in, 390, 391; new, appear'•

annual number of eruptions, 233 ;
ing and vanishing, 392, 394; miss- celebrated eruptions, ib.; earth-
ing, 395.

quakes caused by, 234 ; supposed
Variables, region of the, 122.

causes of action, 235; Sir John
Vegetation, effect of, in lowering tem- Herschel's theory, 235-237.

perature, 243; the two requisites Volta, Professor, electricity rendered
for, 248 ; strength and vitality of, manageable by, 297; the world's
249.; chemical action of light in- debt to, 328.
fluencing, ib.; laws of its distribu- Voltaic electricity, first suggestions
tion, 249-252; distribution of of, 297 ; theory of the transmission
marine, 252, 253; theories of of, 298; construction of the bat-
specific diversity of original distri- tery, 298, 299; theory of its pro-
bution of, 253, 254.

duction, 300; characteristic pro-
Veitch, James, comet with luminous perties, 300, 301 ; action of, gene-

rings discovered by, 374, 375. rating heat and light, 301-303 ;
Venus, zone of instability between arc, experiments, 303-305; the,

the sun and, 21; perturbation in discharge oxidizing silver, 305,
the mean motion of the earth and, 306 ; stratified light, 306, 307;
26; eclipsing Mercury, 42; tran- chemical decomposition effected by
sits of, parallaxes calculated from, agency of, 307, 308; crystalliza-
52, 53 ; astronomical tables of, 63 ; tion, 308 ; an agent in the fine arts,
climate, 226.

309; conductors of, ib.; relations
Vernal equinox, planetary motions of heat and, 310; fish producing
estimated from, 9.

effects of, 310, 311; science sug-
Vesta, astronomical tables of, 63; no gested by its influence on a mag-
atmosphere surrounding, 226.

netized needle, 312; rotation ef-
Vesuvius, revived volcanic action of, fected by, 313, 314; inducing
234.

magnetism, 314, 315; distinction
Vibrating plates used in experiments between static electricity and, 317;
on musical sound, 144, 147.

unvarying dual force of, 334.
Vibrations of the air producing sound, Voltaic pile, the, invention of, 297 ;

129; in music, 131; number made by perfected, 298-300.
the human voice in a second, 132. Vortices, molecular, theory of, 104.

of the ether in natural and po- Vosges mountains, temperature of
larized light, 193; in fluorescence mines in the, 228.
of light, 196; plane of, in polarized | Vulpecula, nebula in, 409.

light, 223.
Vico, Padre de, comet discovered by, WARDHUS, transit of Venus observed

370.
Vienna, observations on comets from, Watches, irregular action of, corrected
370.

by the laws of unequal expansion,
Vincent, St., revival of an extinct 272.
volcano in, 234.

Water, constituent parts of, 111;
Virginia, daguerreotyped spectral boiling point of, an estimate of
image obtained in, 213.

mountain heights, 120; as a me-
Virgo, planetary conjunction between dium for sound, 135; light polar-

Libra and, 42; variable star in, ized circularly by, 194; experiment
392; star vanished from, 395 ; deciding the velocity of light in,
nebulous zone passing, 416, 417. 202; law of expansion of, 271;

at, 53.

ZETA.

WATERSPOUTS.
process of congelation, 276; boil- mena of rotatory motion, 125 ;
ing points of, 277; decomposed by hurricanes, 125, 128; agency of, in-
electric agency, 307 ; as an electric fluencing temperature, 244, 245.
conductor, 309; rotating by elec- Wines, range of cultivation of the
tricity, 314.

best, 250.
Waterspouts, origin and cause of, 128. Winter, atmospheric electricity in,
Waterstone, Mr., magnetic property 291.

of the ethereal medium maintained mean temperature of, varying in
by, 357.

the same latitude, 246, 247.
Waves neutralized by interference, 99. Wolf, Professor, periods of variation

-, atmospheric, over local districts, in solar heat computed by, 225.
periods, dimensions of, 121, 122. Wollaston, Dr., experiments of, on

of sound, 131 ; furnishing an sensitiveness to sound, quotation
illustration of reflections of sound from, 132 ; experiment of, to show
and light, 137 ; interference of, pro- the effect of variable media on re-
ducing calm, 139.

fraction, 156 ; discovery of rayless
Wedgwood, Dr., attempts of, to trace lines in the solar spectrum, 162;

objects by means of light, 203, 204. observations of, on the chemical
Week, the, of seven days, the most properties of the solar spectrum,

ancient and universal division of 203, 209; magnetic rotation sug-
time, 85.

gested by, 313; light emitted by
Wells, increase of temperature in, the heavenly bodies calculated, 404.

230, 231.
Welsh, Mr., observations made by, in
a balloon ascent, 119.

X1 Ursæ Majoris, periodic time of,

398 ; velocity of the revolving star,
West Indies, the, cause of hurricanes

400.
in, 126.
Wheels invented to test intensity of
sound, 132, 133.

YEAR, a, in Jupiter and Saturn, 66 ;
Wheat, range of its cultivation, 250. tropical change in its length, 80;
Wheatstone, Professor, experiments in

length of the sidereal, ib.; period
acoustics of, 132 ; musical instru- of the mean, 83; estimation of the
ments invented by, 143; paper on

Egyptian, 85; first of our era, 86;
musical vibrations read by, 145 ;

ZETA.

ZOOPHYTES.
Zeta Herculis, periodic time, eclipse perature below the earth's crust,
of, 398 ; light, 402.

228 ; comparative unequal distri-
Zinc, seleniate of, effect of tempera- bution of land in temperate and

ture on its crystals, 107; sulphate torrid, 244 ; of fixed stars, 385 ;
of, its crystals boiled in alcohol, of stars nearest the sun, 390 ; ne-
108.

bulous, 416; of nebulous patches,
electricity communicated to 417; of meteoric nebulæ, 423.
plates of, 220.

Zones of instability of planetary orbits,
Zodiac, the, signs of, change in their 21.
positions, 80.