Cyanite, changes effected in, by mag-
netism, 349.
Cyanotypes, coloured photographs
obtained by, 206.
Cygni 61, distance from the sun of,
389; orbit and mass of, 398, 399;
colours, 401; mass, 404; proper
motion, 405.
Cygnus, portion of the Milky Way
lying between a Centauri and, 386.
Cylinders, rotating by electricity,
313; electro-dynamic, 316.
DALCOATH copper-mine, its tempera-
ture, 228.
Daguerre, M., his inventions in pho-
tography, 205; action of light on
the iodide of silver explained by, 219.
Daguerreotype, the, invention of, 205.
Dalton, Dr., law of definite proportion
established by, 111; law of the
wind's rotation observed by, 125.
Damoiseau, M., perturbations of a
comet computed by, 367.
Daniell, Professor, Voltaic battery im-
proved by, 299.
Daubuisson, M., observations of, in
mines, 228.
Davy, Sir Humphry, his first attempts
to produce photographic pictures,
203-204; experiment of, proving
identity of heat and motion, 275;
experiments on the electric spec-
trum, 289; alkalies, earths decom-
posed by, 307.
Days, law determining the length of,
71; period of the mean sidereal
and solar, 83; varying with the
seasons, 84; decimal division of,
84; seven, the most permanent
division of time, 85.
Deccan, the, wheat ripening in, 250.
December, 1832, disappearance of
Saturn's rings in, 67; coincidence
of mean and apparent time in, 84;
date of Christ's nativity, 85; the
astronomical year beginning in, 86.
Decimal division of time, 84.
Declinations of the moon, 97.
Decomposition, effected by electricity,
307-308; by magnetism, 323; by
thermo-electricity, 333.
Delambre, his computations of the
length of the year, 359.
Delta Cephei, a variable star, 391.
Denmark, course of the tidal wave to,
94.
Density, variable, impeding sound, 135,
136; of media, modifying refrac-
tion, 153.
Densities of heavenly bodies, formula
finding, 56; experiments, 57, 58;
comparative of the terrestrial globe,
77, 78.
Deserts, causing monsoons, 124; in.
fluence of, on temperature, 243.
Dew, cause of its deposition, 269.
Dialectrics in electricity, 286.
Diamagnetic substances, 335, 336.
Diamagnetism defined, 335; sub-
stances it is resident in, 336; dis-
covery, characteristics of, 347;
neutral substances obtained by pro-
portionate combination of, with
paramagnetism, ib.; polarity of,
348; connected with arrangement
of molecules, 350-351; affected by
division and compression, 351; pos-
sibly identical with paramagnetism,
356, 357.
Diameter of the earth, 21; Jupiter's
polar, 27; excess of his equatorial,
39; apparent, of the sun and moon,
nearly equal, 40; of the earth,
49; of bodies composing the solar
system, 56; of Neptune, 63;
comets lacking a sensible, 373;
contraction of, in comets, 377;
causes assigned for, 377, 378.
of an annular nebula, 410;
sensible, of a planetary nebula, 412,
Diamond, the, polarized light reflected
from, 193.
Dieppe, seen from Hastings, 157.
Differential telescope, the, experi
ments to be made by, 227.
Discord, a, in music, 142.
Diurnal tides of the atmosphere, their
duration, 121.
variations in mean values of the
magnetic elements, 343.
Dobereiner, M., spontaneous combus-
tion discovered by, 112.
Doldrums, region of the, 123.
Dolland, Mr., achromatic telescope
perfected by, 165.
Donati, Signore, discovery of his
comet, 378; changes in, its irregu-
larities, 379.
Doradus, nebulous patches on, 417.
Dorpat, occultation of a star observed
from, 364.
Double nebulæ, 411.
Double stars, catalogues of, 395, 396;
formulæ obtaining the relative
position and motions, 396, 397;
eclipse in Virginis, 397; orbit of,
determined, 398; eclipse in Her-
culis, ib.; orbits and periodic times
of, 398, 399; anomalies in motions,
400; optically double, 400, 401;
colours of, 401; rays composing
the light of, 401, 402; passage of
light from, furnishing data to as-
certaining their actual distance,
402, 403; data for finding their
masses, 403, 404; calculations
founded on the quantity of light
emitted from, 404; real and ap-
parent motions of, 404-406; appa-
rent periodic time, 406, 407; con-
nection of elliptical nebula with,
Dove, Professor, law of the wind's
rotation developed by, 125; aver-
age temperature of the earth's sur-
face estimated by, 237.
Draco, nebulous system in, 417.
Draper, Professor, experiments of, on
fluorescence of light, 198; experi-
ments in photography, 213; pro-
perties of parathermic rays dis-
covered by, 219; spectrum produced
from diffracted light, 223; theory
of heat propagated by undulations,
Dunlop, Mr., revolution of a double
star calculated by, 400.
Dusejour, M., distances of comets com-
puted by, 359.
Dynamic electricity, 297. See Voltaic.
theory of heat, fundamental
principle of, 357.
Dynamic equator of the earth, 343.
Dynamical theory of heat, 274, 275;
illustrated by liquefaction and con-
densation, 278; by generation of
steam, 277, 276; power of nature,
279-281.
Dynamics, principle in, a law, with
regard to the earth's rotation, 72;
electro, discovery of action of cur-
rents in, 316; the theory of, uni-
versal application of, 426, 427.
EARTH, the, influence of its form on
attraction, 4; square of the moon's
distance from, 5; form of, 6, 7;
moon's influence on its rotations, 7;
diameter of, 21; mean distance
from the sun, ib. note; permanence
of revolution in its times and sea-
sons, 23; perturbation in the mean
motion of Venus and, 26; proof of
the motion of, in its orbit, of its
rotation, 32; variations in its at-
traction of the moon, 37; com-
pression of its spheroid, 38; in-
ternal structure of, 39; its mean
distance from the sun, 43; theo-
retical investigation of its figure,
44-46; dimensions of, determined,
48, 49; figure of, found by cal-
culating its variations in gravita-
tion, 49-51; density compared with
the sun, 56; experiments finding
its mean density, 57, 58; rate of
revolution round its axis, 58; its
diurnal rotation immutable, 71, 72;
changes in temperature and their
causes, 73, 74; nature of the revo-
lutions producing geological changes,
76, 77; conjectures touching its
internal structure, 78; effects pro-
duced by solar and lunar attraction
affecting its equator, 79-81; its
form furnishing standards of weight
and measure, 89; rotation of, act-
ing on tides, 92; attraction of,
affecting the lunar atmosphere, 226;
conjectured constitution of its in-
terior, 231, 232; principles regu-
lating the diffusion of solar heat,
237-247; distribution of known
species of plants over, 249-252;
electric tension of, 291; lines of
magnetic force issuing from, 341;
magnetic properties of, 342, 343;
effect of its collision with a comet,
368; nearest approach of comets
to, 369; passage of light from a
Centauri to, 388; theories of me-
teors falling on, 421-423.
Earthquakes in South America, 234.
Earths, decomposed by voltaic elec-
tricity, 307.
Eastern coasts, cause of their colder
climates, 244.
Ebb, see Tides.
Eboulemens of mountains in Switzer-
land, cause of, 271.
Echoes, theory of their origin, 137,
138.
Eclipses, lunar, accelerated revolu-
tions proved by observations of, 36;
observations of, confirming results
of analysis, 38; principle regulating
their return, 39; refraction of rays
by the terrestrial atmosphere, 40.
solar, 40; effects of light in, 41.
planetary, 42; the solar at-
mosphere visible in, 224; of double
stars, 397, 398.
Ecliptic, the, forming the equinoxes,
9; latitude reckoned from the plane
of, ib.; deviations of planetary
orbits from, 10; forces affecting
their position towards, 15; their
compensated and uncompensated
variations to the plane of, 18, 19;
secular variation in the plane of,
23; orbits of satellites, nearly per-
pendicular to, 33; lunar motions
towards, 35; inclination of the
sun's plane of rotation to, 65; in-
clination of the plane of Saturn's
rings, 67; inclination of the plane
of the terrestrial equator, 79; ten-
dency of its plane to coincide with
the equatorial, ib.; retrograde mo-
tion of the equinoctial points on,
80; obliquity of, affecting the du-
ration of time, 84.
Edinburgh, comparatively equal mean
annual temperature of, 246.
Egypt, hieroglyphic manuscript from,
interpreted by astronomy, 89.
Egyptians, the civil year of, 85.
Elastic impact, the foundation of dy-
namical theories, 357.
Elasticity, property of, resisting com-
pression, 105.
Electric telegraphs, experiment sug-
gesting the principle of, 323; con-
struction of, 325-328.
Electricity assumed as the medium
attracting particles of matter, 103,
104; identical with chemical affi-
nity, 110; in composition and
decomposition, subject to laws of
definite proportion, 112; influenc-
ing winds, 125; its comparative
velocity, 138; producing phos-
phorescence, 217; communicated to
metal plates by juxtaposition, 220;
impressions traced on glass by, 221;
rays exciting, 223; a dual power,
282; modes of exciting by disturbing
equilibrium, 282-284; transmis-
sion of, 284, 285; transmission by
induction, 285, 286; laws of attrac-
tion and repulsion determining in-
tensity of, 286-288; heat and light
produced by, 288; velocity of,
289; experiment determining its
velocity, 290; development of, in
the atmosphere, 291, 292; phos-
phorescence excited by, 294; Vol-
taic, see Voltaic; conduction of
static, contrasted with Voltaic, 309;
laws of action in, distinguishing it
from Voltaic, 317; relation be-
tween polarized light and, 320;
experiment establishing its identity
with magnetism, 322, 323; tele-
graphs working by, 323-328; pro-
duced by rotation, 330, 331;
thermo, 332, 333; exact balance of
its dual force, 334; points of
analogy between magnetism and,
340, 341; causing convulsions in
comets, 375.
Electro-dynamics, see Dynamics.
magnetism, see Magnetism.
Elements, the three terrestrial mag-
netic, 343; variations in, ib.;
storms affecting, 344.
Elevation, effect of, on temperature,
240-242; on vegetation, 250.
Ellipses, described by planets, 5;
paths of planets describing, 10;
preventing compensation of dis-
turbance, 15; cause and measures
of variation in, 17; described by
comets, 363, 366.
Ellipsoid, an, of revolution, mass as-
suming the form of, 45; its equa-
torial and its polar radius, 48;
permanent axes of rotation, 76.
Elliptic motion, ratio of forces pro-
curing, 382.
Elliptical polarization of light, 192,
193; of heat, 267.
nebulæ,
409; their connec-
tion with double stars, 411; fre-
quency, 413; difficult of resolution,
415.
Encke, Professor, sun's parallax found
by, 53; his comet, 169; aspects,
period of his comet, 365, 366;
cause of acceleration in its revolu-
tion, 366, 367; crossing the ter-
restrial orbit, 368; prospective and
present planetary influence on, 369;
disappearance of its tail and nucleus,
369; referred to, 377; contraction
of diameter, ib.
England, arcs of the meridian mea-
sured in, 48; course of the tidal
wave towards its west coast, 94;
peculiarities of photography in, 213;
meteors falling in, 421.
Engravings copied by photography,
204; impressions taken by contact
with iodized silver, 221; impres-
sions taken from, by galvanism,
Epipolic light, 197.
Epsilon Orionis, zone of stars passing
through, 385.
Equation of the centre, defined, 9;
lunar, 35.
Equator, the, forces compelling the
wider circle of, 6; inclination of
the terrestrial to the plane of the
ecliptic, 23; of the solar system,
24; measure of the centrifugal force
at, 49; calculation from lunar ac-
tion on the terrestrial, 55; effects
produced by external attraction in-
flucing the direction of its plane,
79, 80; inequality in its polar
motion, 81; cause of the calms at,
122; depth of the underground
stratum of constant temperature at,
228; maximum of solar heating
influence, 238; superficial extent
of land, 244; mean annual tem-
perature, 245.
Equator of the sun, maximum of solar
heat attained in, 225.
dynamic, surrounding the ter-
restrial globe, 343.
-, magnetic, of the earth, 343.
Equinoctial circle, the, defined, 9,
points, effects of solar and lunar
attraction on, 79; period of their
revolution, 80; measuring time,
83..
Equinoxes, the, defined, 9; vernal, a
point whence planetary motions are
estimated, ib.; of the planets, cause
of a precession in, 66; causes pre-
venting their invariable correspond-
ence with points of the ecliptic, 79;
precession affecting the seasons, 80;
secular motion of, periodic varia-
tions, 80, 81; eras depending on the
precession of, 86, 87; tides aug-
mented in, 97.
Eras, astronomical, determined by the
position of the major axis of the
solar ellipse, 86, 87.
Eratosthenes, the earth's circumfer-
ence measured by, 49.
Eridanus, nebulous patches crossing,
Erman, M., depression of the baro-
meter observed by, 120.
Eruptions, volcanic, recorded, 234.
Eta Aquilæ, a variable star, 391.
Argûs, zone stretching from,
390; nebula round, 418, 419.
Coronæ, periodic time of, 398.
Etna, measurements of, 120.
Ethereal medium, undulations of,
propagating heat, 267; permeable
to lines of magnetic force, 344; its
density, 356; transmitting gravity,
ib.; magnetic, 356, 357; offices
discharged by, 357; pervading the
visible creation, 358; influence of,
on comet motion, 365; astral
revolutions accelerated by, 366;
probable increase in density of,
367.
Faraday, Dr., gases reduced to liquids
by, 105; experiments testing
chemical affinity, 111; instance of
cohesive force inducing chemical
combination, 112; experiments on
vibrations producing colour, 173;
influence of dialectrics, 286; chemi-
cal origin of electricity defended
by, 300; electro-chemical decom-
position defined by, 308; remarks
of, on conduction of voltaic elec-
tricity, 309; experiments on mag-
netic rotation, 313; experiment
magnetizing polarized light, 318,
319; importance of his experiment,
320; experiment establishing the
identity of magnetism and elec-
tricity, 322, 323; his magnetic
battery, 324, 325; aid given by,
in construction of telegraphs, 326,
328; electricity produced by rota-
tory motion explained, 330; his
classification of substances accord-
ing to magnetic qualities, 332;
quotation from, on conservation of
force in electricity, 334; mag-
netism raised to a new science by,
335; the magnet as represented by,
338; experiment determining the
forms of magnetic lines of force,
339, 340; accidental electro-mag-
netic combinations pointed out by,
342; his discovery of diamagnetism,
347; experiments on magnetic
action in crystals, 349; observa-
tions on influence of heat in mag-
netism, 352; definition of gravity
questioned by, 354, 355; mag-
netism of the ethereal medium
tested, 356.
Fauna, distinct, of separate regions,
254, 255.
Faye, M., his conception of the sun's
constitution, 41; his theory of
phenomena observed in eclipses, 42;
comet of 1843 discovered by, 361.
Fiedler, Dr., fulgorites exhibited by,
293.
Fire, chemical combination producing,
balls, theory of, 421.
Fires, central, subterranean, 231-
237.
Fish, phosphorescent, 294, 295; elec-
tric, 310.
Fixed stars. See Stars.
Fizean, M., decisive experiment in
proof of the undulatory theory of
light accomplished by, 202.
Flame, chemical combination evolv-
ing, 270, 271.
Flames, lambent, caused by elec-
tricity, 294.
divergent from the nucleus of a
comet, 364.
Fletcher, Mr., periodic time of y
Virginis determined by, 398.
Flora of the Himalaya, 250; distinct,
in separate regions, 251; condi-
tion establishing distinct, in islands,
252.
Florence, comet discovered from, 378.
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