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capability of producing fluorescence,
196; capability of, in rays, affect-
ing their chemical action, 209-
212; effect of, on the lunar atmo-
sphere, 226; influence of, on
transmission of heat, 258; of rays
of heat, 261-264; heat polarized
by, 266.
Refrangibility, substances diminishing,
of light, 196; affecting the che-
mical action of rays, 209-212;
affecting radiation of heat, 257;
affecting transmission of radiant
heat, 261-263.

Reich, Professor, temperature of mines
observed by, 228; mean increase
calculated by, 230.

Reptiles, distribution of distinct species
of, 254.

Repulsion of electricities, 283; expe.
riments determining the laws of
electrical, 286, 287; modes of, in
static and in Voltaic electricity,
317; developing comets' tails, 375-

Resistance, a cause of accelerated
motion, 367.

Retina, the, action of, in receiving im-
pressions, 166; comparative sen-
sibility of its fibres to light,


Retrograde motion of comets, 359,
368, 373, 379.

Rhodiola rosea, identical species of,
found in Tartary and in Scotland,

Rhombohedrons of carbonate of lime,

Richman, Professor, killed by light-
ning, 293.

Richter, variation in length of the
pendulum observed by, 51.
Rings of Saturn, 66-68; Saturn's,
diamagnetic, 347; luminous, sur-
rounding comets, 374, 375; sur-
rounding Donati's, 379.
Ritchie, Professor, electrical experi-
ments of, 314.

Ritter, M., chemical properties of the
solar spectrum observed by, 203;
oxydizing effect of red rays, 209.
Rive, M. Auguste de la, rate of in-


crease of temperature in wells ob-
served by, 230.

Rivers, curvature of the land proved
by, 46; influence of, on the earth's
rotation, 71; rising of tides in,
98; effect of, in cooling the atmo-
sphere, 243.

Roget, Dr., phenomena of electro-
magnetism explained by, 313.
Rome, observations on lunar moun-
tains made at, 70; era fixed
at, 85; comet discovered from,

Ross, Sir James, stratum in the ocean
discovered by, 101; depressure of
the barometer observed by, 120;
volcanic region discovered, 232.
Rosse, Lord, nebulæ resolved by his
telescope, 407, 408; spiral nebula,
409, 410; annular nebulæ dis-
covered by, 410; nebulous star,
411; planetary nebulæ, 412; ne-
bulæ resolved by, 415.

Rotation affecting winds, 122-127; of
winds, 124, 125; of hurricanes,
125, 126; produced by the Voltaic
current acting on iron, 305; of
stratifications of electrical light,
307; caused by electricity, 313,
314; of light caused by an electric
current, 319; of magnets pro-
ducing electricity, 330-332;
changes produced in comets by,


Rotations of the solar system, 7; of the
sun, 65; of the planets, 66; of satel-
lites, 68; of Jupiter's satellites, 70;
of the earth, a measure of time, 71;
influence of temperature on, 72;
axis of, invariable, 76, 77.
Rotatory motion, form indicating, 65;
of Donati's comet, 379.
Roux, M. le, observations on magnetic
action in crystals, 350.
Rudberg, M., refrangibility of sub-
stances ascertained by, 201, 202.
Ruhmkorff, M., improvements on his

electro-inductive apparatus, 328.
Russell, Scott, Mr., velocity of the

tidal wave estimated by, 95.
Russia, arc of the meridian measured
in, 48; climates of, 244.


SABINE, General, variations in the
magnetic elements investigated by,
343, 344.

Sagittarius, comet traversing the
constellation of, 379; the Milky
Way in, 386; nebula, 414.
Sahara, the, causing monsoons, 124.
desert, extent, influence of, on
the atmosphere, 243.
Salt, Mr., papyrus sent from Egypt
by, 89.

Sand, tubes in, formed by lightning,

Sandy deserts influencing temperature,

Sandwich Land, excess of cold in, over

corresponding latitudes, 241.
Sargassa, or grassy sea, found in the
Atlantic, 253.

Satellites, intensified action of attrac-

tion upon, 7; intimate union of,
with their primaries, 26; excep-
tions to a general law of the solar
system, 65, note; rotations equal
to the times of their revolutions,
68; comet passing through, 69.

Jupiter's, proportion of their
mass to that of their primary, 27;
disturbing force of attraction affect-
ing their orbits, 28; periodic and
secular inequalities, 28, 29; eclipses,
30; rotation, 70; passage of a
comet through, 359; comet nearly
approaching, 370.

of Saturn, 32; of Uranus and
Neptune, 33.

mode of computing their masses,
55; comparative density of, 58.
of Neptune, 63.

of the earth, shooting stars,
Saturn, unequally occurring compen-
sations of disturbance in its motions,
15; disturbing influence of, on
Jupiter, excentricity of its orbit
compared with Jupiter's, 17; re-
tarding the revolution of Jupiter's
nodes, 19; invariable plane passing
between Jupiter and, 24; observa-
tions on the mean motions of Ju-
piter and, 25, 26; eclipse of, 42;
internal structure, 58; astronomical


tables of, 60; period of his year,
66; the rings of, described, 66-68 ;
his ring probably diamagnetic, 347;
action of, on Halley's comet, 362,
363; comets having their perihelia
in his orbit, 381.

Saurian reptiles, distinct tribes of,

Saussure, M., temperature of mines

observed by, 228, 229; lichen dis-
covered by, 249.

Savart, M., his researches and experi-
ments in acoustics, 132, 133; ex-
periments on vibrations of glass
rulers, 145-147; experiments show-
ing sympathetic undulations, 148,
149; discoveries on the nature of
voice, 152.

Savary, M., orbital elements of a
double star determined by, 396;
his mode of ascertaining the actual
distances of fixed stars, 402,

Scheele, M., chemical changes effected
by the solar spectrum observed by,

Schroëter, height of planetary atmo-

spheres calculated by, 226.
Schwabe, M., periodic variation in the
solar spots observed by, 344.
Science, its value regarded as the
pursuit of truth, 1; errors of the
senses corrected by, 32; evidence
of its antiquity, 87.
Sciences, mutual relations of forces
proving the connexion between,
319-321; analysis proving the
whole circle of, kin, 427, 428.
Scoresby, Captain, phenomenon occa-
sioned by refraction observed by,

Scorpio, vacant patch of the Milky
Way in, 386; position of, 390; a
double star in, 395; nebula in,

Scotland, progress of the tidal wave
round, 94.

Sea, the, inappreciable influence of,

on the direction of gravity, 77;
mean height of snow-line above the
level of, 241; comparative extent
of, 242.


Seasons, conditions determining the
duration of, 74; cause of their un-
equal periods, 87; theory of the
tropical dry and rainy, 123.
Seaweeds, photographic impressions
of, 205, 206; luxuriance, deep
colours of, 253.
Secchi, Professor, mountains of the
moon observed by, 70; photo-
graphic image of the moon obtained,
214; temperatures of the sun's
surface estimated, 225; experi-
ments of, in photographing the
moon and Jupiter, 226, 227.
Secular inequalities of planets, 13,
14; means of discovering, 24, 25;
effect of, on the mean motion of the
moon, 36, 37.

variations in mean values of the
magnetic elements, 343.
Seebeck, point of maximum heat in
solar spectrum fixed by, 263; dis-
covery of, 264; relations of heat to
electricity discovered by, 332, 333.
Seed-lobes, proportion in the distri-
bution of plants having one or two,
Seleniate of zinc, crystals of, 107.
Senarmont, M., experiments of, in ex-
pansion of crystals, 273.
Senses, necessarily inaccurate testi-
mony of the, 281.

September, times coinciding in, 84.
Serpentarius, star in, vanishing, 392.
Shell-fish, their mode of clinging to
rocks, 117.

Shield, the, clusters of the Milky

Way between Ophiuchus and, 387.
Shooting stars, phenomena of, de-
scribed, 421, 422; theories of,

Siberia, Eastern, depression of the
barometer observed in, 120.
Sidereal times, mean, periods of, 83;
measurement of apparent, ib.
Sigma Eridani, period of revolution
in, 400.

Silesia, fulgorites from, 293.

Silver iodized, its sensitiveness to im-
pressions, 221.

Sirius, the Egyptian year estimated
from, 85; comet's tail extending


from the Hare to, 373; rank of,
384; comparative magnitude, 385;
parallax, 389; cause of his irre-
gular motion, 392; change in
colour, 401; light, 402; extent of
surface, 404.

Smyth, Admiral, his measurement of
Etna compared with Sir John Her-
schel's, 120; eclipse of a double
star observed by, 397; its periodic
time determined, 398.

Piazzi, heat of the moon felt
by, 227.

Snow, cause of perpetual, on summits
of alpine chains, 119; causes modi-
fying the height of the line of per-
petual, 241; protecting vegetation,
249; radiation of heat by, 257.
Soda, sulphate of, change of form in
its crystals, 107; crystals of the
neutral phosphate and the arseniate
of, 109.

Soil, the, dependence of temperature
on the nature of its products, 243.
Solar gravitation, 424, 425.

magnetism, its connexion with
terrestrial, 344.

spectrum, cause of the point of
maximum heat varying in, 263, 264.

system, the, gravitation of the
bodies composing, 5; conditions
securing the stability of, 11, 12;
proof of its stability, 20; equi-
librium of, underanged by the
ethereal medium, 22; invariable
plane, forming the equator of, 23,
24; question of its revolution
round a common centre, 24; pro-
perties of its medium, 32; masses
of bodies composing, 55, 56; their
diameters, 56; uniform direction
of rotation in, 65; comparative
apparent importance of, in creation,
226; probably magnetic through-
out, 346; comets forming part of,
365; possible ultimate destruction
of, 372; computations of comets
revolving within, 381, 382; paths
described by heavenly bodies in,
382, 383; position of, relatively
to the Milky Way, 385; direction
of its motion, 405.


Soleil, M., crystals compressed by,
Solids, conditions reducing molecular
particles to, 104, 105; distinctive
forms taken by matter in, 106;
velocity of sound passing through,
135; change of shape in, accom-
panying ringing sound, 147; ex-
pansion of, by heat, 271.

Solstices, the, solar motion at, affecting

the duration of time, 84; the year
estimated from the winter, 85;
periodical coincidence of the solar
perigee and apogee with, 86, 87.
Sothaic period, the, of the Egyptians,
Sound, medium conveying, 129; its
propagation by undulations illus-
trated, 129, 130; conditions modi-
fying the intensity of, musical notes,
131; experiments testing the com-
pass of audible, 132, 133; media
modifying the velocity of, 133-137;
laws of its reflection from surfaces,
137, 138; undulations of, subject
to the laws of interference, 138,
139; laws of the foundation of
musical science, 140-143; rein-
forced by resonance of cavities, 150,
151; repeated vibrations required
to produce, 178; different modes of
action in undulations producing
light and, 199, 200; identical
nature of heat and, 280, 281; mea-
suring velocity, 290, 291.
Sounding boards, intensifying musical
vibrations, 149; action of, in mu-
sical instruments, 150.
South, Sir James, positions of stellar
systems measured by, 396.
South pole, the, excess of cold at, 241.
Sea islands, height of tides at,


Southern Ocean, rise of the tidal wave
in, 93; velocity of the wave,
Spain, meteoric showers off the coast
of, 421.

Specific heat defined, 275.

Spectra of gases and flames, their

characteristic peculiarities, 163,
164; three superposed, of the pure
white sunbeam, 222.

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Spectrum, the solar, decomposed into
seven colours, 159; colours of, modi-
fied by thickness of the medium
absorbing, 160; decomposed into
three colours, 161; rayless lines
in, 162; observations and experi-
ments on rayless lines, 163, 164;
experiment of fluorescent light, 197;
obtained independently of prismatic
refraction, 201; energetic action of,
on matter, 203; photographic co-
loured images of, 208-210; analysis,
properties of, experiments, 211-219;
complex nature of, 222; produced
from diffracted light, 223.

of an electric spark, 289.
of the Voltaic arc, 303.
Spheres,mode of attraction in hollow and
solid, 4; planets partaking the nature
of, 7; impulses regulating rotations,
ib.; conditions procuring the figure
of, 44; formula finding the density,
56; force giving the form of, 106;
power of retaining electricity, 288.
Spherical form, the result of cohesion,

Spheroids, influencing attraction dif-
ferently from spheres, 4; force dis-
turbing attraction in, 27; com-
pression of the terrestrial and of
Jupiter's, computed, 38, 39; of
elliptical strata, quantities invari-
able in, 46; of the sun, 65; effect
produced by the attraction of an
external body on, 79; power of
retaining electricity, 288.

Spiral nebula, 409, 410.

Spots on the sun's surface, periods of
their vicissitudes, 224; amount of
heat varying with, 225.
Spring tides, 96-99.

Springs, hot, rising in mines, 229;
mean heat of the earth determined
from, 238.

Standards of weights and measures,
whence derived, 89, 90.

Stars, fixed, the, the solar system pro-
bably not independent of, 24; ve-
locity of light deduced from aberra-
tion of, 31; vast distances of, 54;
precession affecting their longi-
tudes, 80; computations of their


positions furnishing historical data,
88, 89; made visible by refraction,
154; peculiar law of light demon-
strated by the aberration of, 202;
magnitude of the solar system seen
from, 226; numbers, classification
of, 384; positions, 385; the Milky
Way, 385-387; parallaxes and
distances of, 387-389; variable,
390-395; missing, 395; systems
of multiple, classified, ib.; binary,
395-406 (see Double stars); ne-
bulous, 406-419 (see Nebula);
seemingly innumerable, 420; me-
teors, 420-423.

Static electricity, 282: see Elec-

Steam, formation of, 269; force con-
verting liquids into, 277; measure
of its elasticity, 278; question of
its being superseded by electricity,
Steel, paramagnetism induced in, 336;
conditions of magnetic power re-
maining permanently in, 337, 338;
its elasticity affected by magnetism,

Stephenson, George, quotation from,

Stokes, Professor, remarks of, on gra-
dation of colours, 161; experiments
on fluorescence of light, 197; his
decision with regard to vibrations of
polarised light, 223.

Storms, magnetic, 344; varying with
latitude, 345, 346.

Strata of the earth, position and com-
parative density of, 77.
Stratifications, experiments showing,
in electric light, 306, 307.
Struve, M., measurement by, 48; his
observations on Saturn's rings, 68;
occultation by a comet observed by,
364; comet's nucleus described, ib.;
distance of a fixed star measured by,
388, 389; catalogue of double stars,
396; remarks on colour and light
of double stars, 401; sun's motion
proved by, 405.

Stutgardt, natural hot springs used in
manufactories near, 231.
Submarine telegraph, 325-327.


Sulphate of magnesia, its crystals
boiled in alcohol, 108.

of nickel, effect of exposure to
the sun, on its crystals, 107.
of soda, its crystals, 107.

of zinc, experiment on its crys-
tals, 108.
Sulphuretted hydrogen gas, its con-
stituent parts, 111.

Sumbawa, volcanic eruption of, 233.
Summer, mean temperature of, vary-
ing in the same latitude, 246, 247;
atmospheric electricity in, 291.
Sun, the, law regulating his attraction
of heavenly bodies, 5; effect of his
attraction on planetary orbits, mean
distance of planets from, 8; im-
portance of his magnitude in the
solar system, 12; disturbances in
the relative positions of planets and,
14; force modifying his intensity of
attraction, 16; resistance offered
by, to the power of disturbing
forces, 20; periods of conjunc-
tions of Jupiter, Saturn, and, 25;
influence of, on lunar motions,
34, 35; action of the planets re-
flected by, 37; eclipses of, 40, 41;
supposed constitution of, 41; his
atmosphere, 42; mode of finding his
parallax, 52, 53; mean distance
from the earth, 53; mass of, 55;
diameter, 56; comparative density,
attractive force, 56, 57; astrono-
mical tables of, 63; deductions
from his rotation about an axis,
period of, 65; attraction of, pro-
ducing a precession of the equinoxes,
79, 81; returns of, a measure of
time, 83-85; divisions of time, de-
pendent on revolutions of the major
axis of his orbit, 86, 87; action on
tides, 92, 97; disturbing the equi-
librium of the atmosphere, 121;
dry and rainy seasons regulated by,
123; cause of decreased light and
heat in horizontal rays, 157, 158;
distance of, falsely estimated, 158;
light polarized by, 195; indications
of an absorptive atmosphere sur-
rounding, 212, 213; his diameter,
224; appearance of, through his

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