Chapter XLIV: Section XXXVII (4)

Biela, M., date of the discovery of his comet, 367;
possibility of collision with the earth, 368;
present and prospective planetary influence on, 369;
becoming two distinct bodies, 369, 370.

Binary systems of stars, 395-406.
_See_ Double stars.

Biot, M., his ascent in a balloon, 118;
experiments of, on the transmission of sounds through pipes, 137;
liquids possessing the power of circular polarization discovered by,
190;
his theory of circular polarization, 191;
cause of phosphorescence in the solar spectrum investigated by, 217.

Birds, distribution of distinct species of, 255.

Birt, Mr., atmospheric waves measured by, 121, 122.

Bise, in Switzerland, cause of, 242.

Bismuth, its magnetic and electric properties, 347.

Black Sea, the, scarcely affected by tides, 98.

Bode, Baron, law of, assumed in computing Neptune’s position, 61;
failing in the case of Neptune, 63.

Bond, Mr., satellite of Saturn discovered by, 32;
elliptical nebula resolved, 413.

Bonnycastle, Captain, phosphorescent phenomenon observed by, 295, 296.

Bonpland, M., identical productions of the Old and New World found by,
251.

Boötes, nebulous system in, 417.

Bore, the, of the Hoogly, its origin, 94.

Botanical districts, distinct, of the globe, 251, 252.

Botto, M., thermo-electricity used in decomposition by, 333.

Bouguer, degrees of the meridian measured by, 48.

Boussingault, M., depth of the underground stratum of constant heat
calculated by, 228.

Bouvard, M., atmospheric undulations estimated by, 121.

Bradley, Dr., motion of the pole of the equator discovered by, 84;
his tables of refraction, 155.

Brahmins, measurement of time by, 85.

Brand, M., observation of, on meteors, 423.

Brewster, Sir David, his analysis of the solar spectrum, 161;
experiments on rayless lines, 163;
experiments on spectra of flames, 164;
law discovered by, determining angles of polarization for light, 183;
experiments on fluorescence of light, 197;
line of coincidence in temperature of springs and of the atmosphere
determined by, 238;
temperature of a pole of maximum cold determined, 245;
isogeothermal lines determined by, 246;
observations on the light of fixed stars, 402.

Brighton, phenomenon caused by reflection observed from, 157.

Brinkley, Bishop, mass of the moon determined by, 56.

British Channel, height of tides in, 98.

—— Isles, atmospheric wave passing over, 121.

Brorsen, M., periods of comets discovered by, 370.

Brown, Dr. Robert, peculiar vegetation found by, in Australia, 251.

Buchan, Dr., phenomenon caused by reflection observed by, 157.

Cæsar, Julius, era computed from his reign, 85.

Cagniard de la Tour, M., instrument designed by, measuring musical
notes, 143.

Calms produced by the trade-winds, 122, 123.

Calorific rays.
_See_ Rays of heat.

Calotype, the invention of, 204.

Camelopard, nebulous system in, 417.

Canaries, the, vegetation of, 252.

Canary-glass, fluorescence of light in, 196.

Cancer, the calms of, 123;
the tropic of, marking the limit of the trade-winds, 126;
nebulous cluster in, 415.

Canis Major, position of, 390.

—— Venatica, nebulous system in, 417.

Capillarity, theory of, 113;
forces producing, 114;
familiar examples of, 115;
curious phenomena, 115, 116.

Capricorn, the calms of, 123;
the tropic of, hurricanes changing their direction at, 126.

Carbon, its powers contrasted as a crystal and as an opaque amorphous
substance, 302, 303.

Carbonate of lime.
_See_ Lime.

Carbonic oxide, its constituent parts, 111.

—— acid, proportion of, in the atmosphere, 117.

Cardinal points, the, position of continental masses with regard to,
influencing temperature, 244.

Caribbean Islands, hurricanes beginning at, 126.

Castor, discovered by Sir William Herschel, 396.

Cassiopeia, star appearing and vanishing in, 392, 393.

Categat, the, consequence of its narrowness, 98.

Cauchy, M., data furnished by, for investigation of the theory of
light, 201.

Cayenne, variation in length of the pendulum between Paris and, 51.

Celestial bodies:
law of their mutual attraction, 4;
of the solar system:
law determining their attraction to the sun, 5;
problem to fix the positions of, on occurrence of disturbance in
their motions through counteracting attractions, 11;
theory of their mutual connection and dependence, 24;
mode of finding the absolute distances of, 43;
distances of, computed from their parallax, 52, 54;
apparent position of, affected by refraction, 153, 154;
apparent infinity of, 420.

Centaur, position of, 390;
brilliant double star in, 399.

Central Asia, the mountains of, their ascent by Marco Polo, 118.

Centre of gravity.
_See_ Gravity.

Centrifugal force, moon’s motions modified by, 5;
influence of, on planet-forms, 6;
retarding oscillations of the pendulum, 32;
action of, in determining the figure of the earth, 44, 45;
measurement of its intensity, 49;
resolved into two forces, its action on the sea, 100.

Ceres, astronomical tables of, 63;
height of her atmosphere, 226;
comet of 1770 revolving beyond the orbit of, 361.

Cetus, nebulous patches crossing, 417.

Chaldeans, the, mean longitude found from observations of, 36;
result of comparison of their observations with modern, 38.

Challis, Professor, Brewster’s analysis of light questioned by, 161.

Charcoal, light produced by electricity from, 302-303.

Charles V., the Emperor, observations on comets, made in his reign,
370.

Chaudes Aigues, temperature of, 231.

Chemical action of rays of the solar spectrum, 203, 207;
varying maximum of energy, 208;
action varying with refrangibility, 209-212;
action in luminous spectrum not continuous, 213;
energy an independent property of rays, 214;
properties of the parathermic rays, 219;
action of light maintaining vegetation, 249;
affinities the source of the power of steam, 278;
of electricity on oxygen, 284;
eliciting voltaic electricity, 297, 300;
voltaic electricity, an agent in, analysis, 307, 308.

—— combinations, theory of, 110;
invariable proportions of, 111;
cohesive force inducing, 112;
producing combustion, 270.

—— force, the power of, 112.

—— rays, causing the deposition of dew, 269.

Chile, elevation of land by an earthquake in, 234.

China, distinct flora of, 251.

—— Sea, the, monsoons blowing over, 124.

—— ink, polarized light reflected from, 193.

Chinese, the, observations of, on the mean motions of Jupiter and
Saturn, 25;
proof of their early study of astronomy, 88;
decimal divisions used by, 90;
elements of comets computed from their observation, 365;
comet of 1264 recorded by, 370.

—— Tartary, herbarium collected in, 250, 251.

Chladni, discovery of, in musical science, 145.

Christian era, traces of astronomical records before, 365.

Chromatype, the invention of, 206.

Chronology, dependent on astronomy, 87-89.

Chrysotype, the, coloured photographs obtained from, 206.

Circuit, galvanic, modes of obtaining, 332.

Circular arcs, principle with regard to their sines and cosines, a
pledge for the stability of the solar system, 20.

—— motion, ratio of forces procuring, 382.

—— orbits of planets distinguished from elliptical, 8;
of satellites, 27.

—— polarization of light, 189-192;
of heat, 266.

Circumference of the earth, 49.

Civil time, measure of its periods, 83;
not precisely adjusted to solar revolutions, 85.

Clairaut, periodic time of Halley’s comet computed by, 362, 363.

Cleavages of crystals, 109;
position of, affecting the intensity of magnetic action, 350.

Climates, planetary, 225, 226;
cause of the different terrestrial, 237;
phenomena affecting, 239, 240;
causes of variety of, 243, 244;
milder, of the Polar Ocean, 245, 246;
like mean annual temperatures not ensuring like, 246;
compensations of irregularities, 247.

Clocks, showing apparent sidereal time, 83;
regulated to show decimal time, 84;
irregular action of, corrected by the laws of unequal expansion, 272.

Clouds, circling the belt of equatorial calms, 123;
region of, 124;
electricity evolved from, 291-292.

Cloyne, Bishop of, his calculation of the moon’s mass, 56.

Coal-measures, tropical plants in, 72, 73;
age of their formation, 75.

Coal, chemical force evolved from, by combustion, 278;
source of its combustible qualities, 279, 280.

“Coal Sacks” in the Milky Way, 386.

Cohesion, influence of, on matter, 105;
phenomena arising from its force, 106;
attraction of, overcome by the expansive power of heat, 271.

Cohesive force, properties of material molecules constituting, 103;
effectual only to unite particles of like nature, 110;
inducing chemical combination, 112;
capillary attraction, an action of, 113.

Coins, impressions taken from, by contact, 220;
by electricity, 221.

Cold, contraction caused by, 271, 272;
mitigated by slow propagation of heat in air, 273;
generated by voltaic electricity, 302;
increasing the conducting power of the air, 345.

Colladon, M., experiments of, testing the velocity of sound, 135.

Collision between the earth and comets, possibilities, possible effects
of, 367, 369.

Collodion, sensitiveness of, to light, 203;
properties of, as an agent in photography, 207.

Colours, seven primary, 159;
theory of the decomposition of white light into, 160;
degree of refrangibility not invariable, 161;
three primary, _ib._;
new, discovered by Sir John Herschel, 162;
rays refracted without, 164;
rarely homogeneous, 165;
experiments on accidental and complementary, 165, 166;
determined by undulations of ether, experiments, 170-175;
of material substances, whence derived, 175;
produced by analyzing polarized light, 186-188;
varying with refrangibility of rays, 198;
obtained in photography, 206;
images of the solar spectrum imitating the prismatic, 208-209;
of seaweeds, 253;
not invariably dependent on light, _ib._;
affected by absorption and reflection, 268;
of the electric spark, affected by the atmosphere, 289;
of the voltaic spectrum, 303;
of the electric spark, 304;
produced by oxidation on silver, 305;
of the fixed stars, 401, 402;
of planetary nebulæ, 412;
of nebulous clusters, 415.

Columbus, beds of algæ found by, 253.

Column, capillary, forces producing changes in its form, 114, 115.

Coma Berenices, a nebulous cluster, 415;
nebulous zone passing, 416, 417.

Combustion, cause of, 270;
defined, 304.

Comets, attraction by the sun of, 5;
disturbances in the motion of, a key to the nature of the ethereal
medium, 22;
retrograde motion in, 33;
passing through Jupiter’s satellites, 69;
return of, to their perihelia, furnishing historical data, 88;
existence of the luminous ether demonstrated by, 168, 169;
terrestrial atmosphere unaffected by, 358;
amount of their light computed, 358, 359;
passages of, through the solar system, 359;
velocity, paths of, 359, 360;
proof of the return of, 360;
disturbing action of planets on their orbits, 361;
of 1770, an example, 361, 362;
computed return of Halley’s, 362, 363;
aspects, records of Halley’s, 363-365;
discoveries made by the revolutions of, 365;
of the solar system, Encke’s, 365, 366;
Biela’s, possibility of collision with, 367, 370;
periods of various, 370;
cause of their brilliancy, 371;
velocity, sun’s influence on, 371, 372;
of 1843, 372, 373;
their constitution, 373, 374;
of 1811, its luminous envelopes, 374, 375;
sudden convulsions in, 375;
tails, 375-377;
causes assigned for contraction of diameter in, 377, 378;
Donati’s, 378, 379;
nature of their light, 379-381;
computations of their numbers, 381, 382;
orbits of, 383;
nebula resembling, 413.

Compass, mariner’s, phenomena disturbing, 312;
intensity of a galvanic current measured by, 315.

Compression of the terrestrial spheroid, calculations of, 48-51;
cause of the great, in Jupiter, 66;
measures of, from pressure of superincumbent mass, 78;
effect of, on magnetic action, 351.

Concord, a, in music, 142.

Conductors of electricity, 284, 285;
lightning, 293;
molecular structure determining the power of, 303.

Conic sections, conditions compelling bodies in space to move in, 5;
principle determining their nature, 11.

Constellations, nearest the sun, 390;
where the orbit of the solar system lies, 406;
occupied by the nebulous system, 417.

Contraction caused by cold, 271, 272.

Cook, Captain, object of his first voyage, 53.

Cooper, Mr., list of missing stars drawn up by, 395.

Copper, electricity communicated to plates of, 220;
lightning-conductors of, 293;
action of an electro-magnet on, 351, 352.

Cordier, temperature of mines observed by, 228.

Cordilleras, effect on temperature of their table-lands, 241.

Corn, a, field used to illustrate the propagation of sound, 129, 130.

Cornwall, hot-springs in mines of, 229.

Corona Australis, nebula in, 414.

Corpuscular theory of light, 167;
phenomena disproving, 171, 175, 176.

Coseguina, volcanic irruption of, 233.

Coulomb, instrument measuring electrical intensity, invented by, 287.

Creation, vastness and magnificence of, 2.

Crimea, cause of the great storm in the, 122.

Cross, Mr., voltaic battery with constant action invented by, 300.

Cross, the Southern, vacant patches of the Milky Way near, 386.

Crystallization defined, 106;
forms of, their variety affected by temperature, 107, 108;
permanent and variable forms, 108, 109;
cleavages in, 109;
common to all substances, _ib._;
by the agency of electricity, 308, 309.

Crystals, conditions determining their forms, 107-109;
optic axes of, 183;
used in polarizing light, 186, 188;
changes in, effected by compression, 189;
transmission of rays of heat by, 258;
expansion of, by heat, 272, 273;
formed by electricity, 308;
action of magnetism in, 349, 350;
circumstances determining the set of, 350, 351;
effect of temperature on magnetized, 352.

Cumming, Professor, experiments of, in thermo-electricity, 333.

Currents, two great, setting from each pole towards the equator, 100;
proving the rotation of winds, 124, 125.

——, electric, flow of, regulated by Volta, 297-299;
characteristics of Voltaic, 301;
conductors, non-conductors of, 309;
continuous flow of Voltaic, 312;
action of, on magnets, 313-315;
reciprocal and mutual action of magnetic and electric, 316, 317;
Ampère’s theory of, unsolved difficulties, 317, 318;
effect of, on polarized rays, 319;
electric, evolved by magnets, 322, 323;
their power of producing induction, 324;
direction of, produced by rotation, 330-332;
evolved by application of heat, 332, 333;
produced by intersecting magnetic curves, 339;
induced by crossing terrestrial lines of magnetic force, 342.

Curves, described by bodies projected in space, 5.

——, magnetic, 338;
electricity produced by intersecting, 339;
nature of, proved by Dr. Faraday, 339, 340;
terrestrial, 341, 342;
extent of the range of terrestrial, 344;
complete connected system of the terrestrial, 345;
inductive effect on the Atlantic telegraph, 346;
diamagnetic, 348.

Cyanite, changes effected in, by magnetism, 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 α Centauri and, 386.

Cylinders, rotating by electricity, 313;
electro-dynamic, 316.

Dalcoath copper-mine, its temperature, 228.

Daguerre, M., his inventions in photography, 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 improved 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 spectrum, 289;
alkalies, earths decomposed 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 refraction, 153.

Densities of heavenly bodies, formula finding, 56;
experiments, 57, 58;
comparative of the terrestrial globe, 77, 78.

Deserts, causing monsoons, 124;
influence of, on temperature, 243.

Dew, cause of its deposition, 269.

Diamagnetic substances, 335, 336.

Diamagnetism defined, 335;
substances it is resident in, 336;
discovery, characteristics of, 347;
neutral substances obtained by proportionate combination of, with
paramagnetism, _ib._;
polarity of, 348;
connected with arrangement of molecules, 350-351;
affected by division and compression, 351;
possibly 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.

Dielectrics in electricity, 286.

Dieppe, seen from Hastings, 157.

Differential telescope, the, experiments 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.

Dœbereiner, M., spontaneous combustion discovered by, 112.

Doldrums, region of the, 123.

Dollond, Mr., achromatic telescope perfected by, 165.

Donati, Signore, discovery of his comet, 378;
changes in, its irregularities, 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 γ Virginis, 397;
orbit of, determined, 398;
eclipse in ζ Herculis, _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 ascertaining their actual
distance, 402, 403;
data for finding their masses, 403, 404;
calculations founded on the quantity of light emitted from, 404;
real and apparent motions of, 404-406;
apparent periodic time, 406, 407;
connection of elliptical nebulæ with, 411.

Dove, Professor, law of the wind’s rotation developed by, 125;
average temperature of the earth’s surface estimated by, 237.

Draco, nebulous system in, 417.

Draper, Professor, experiments of, on fluorescence of light, 198;
experiments in photography, 213;
properties of parathermic rays discovered by, 219;
spectrum produced from diffracted light, 223;
theory of heat propagated by undulations, 267.

Dunlop, Mr., revolution of a double star calculated by, 400.

Dusejour, M., distances of comets computed 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 condensation, 278;
by generation of steam, 276, 277;
power of nature, 279-281.

Dynamics, principle in, a law, with regard to the earth’s rotation, 72;
electro, discovery of action of currents in, 316;
the theory of, universal 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 seasons, 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 attraction of the moon, 37;
compression of its spheroid, 38;
internal structure of, 39;
its mean distance from the sun, 43;
theoretical investigation of its figure, 44-46;
dimensions of, determined, 48, 49;
figure of, found by calculating its variations in gravitation, 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 revolutions producing geological changes, 76, 77;
conjectures touching its internal structure, 78;
effects produced by solar and lunar attraction affecting its equator,
79-81;
its form furnishing standards of weight and measure, 89;
rotation of, acting on tides, 92;
attraction of, affecting the lunar atmosphere, 226;
conjectured constitution of its interior, 231, 232;
principles regulating 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 α Centauri to, 388;
theories of meteors falling on, 421-423.

Earthquakes in South America, 234.

Earths, decomposed by voltaic electricity, 307.

Eastern coasts, cause of their colder climates, 244.

Ebb, _see_ Tides.

Éboulemens of mountains in Switzerland, cause of, 271.

Echoes, theory of their origin, 137, 138.

Eclipses, lunar, accelerated revolutions 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 atmosphere 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 perpendicular to, 33;
lunar motions towards, 35;
inclination of the sun’s plane of rotation to, 65;
inclination of the plane of Saturn’s rings, 67;
inclination of the plane of the terrestrial equator, 79;
tendency of its plane to coincide with the equatorial, _ib._;
retrograde motion of the equinoctial points on, 80;
obliquity of, affecting the duration 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 dynamical theories, 357.

Elasticity, property of, resisting compression, 105.

Electric telegraphs, experiment suggesting the principle of, 323;
construction of, 325-328.

Electricity assumed as the medium attracting particles of matter, 103,
104;
identical with chemical affinity, 110;
in composition and decomposition, subject to laws of definite
proportion, 112;
influencing winds, 125;
its comparative velocity, 138;
producing phosphorescence, 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;
transmission of, 284, 285;
transmission by induction, 285, 286;
laws of attraction and repulsion determining intensity of, 286-288;
heat and light produced by, 288;
velocity of, 289;
experiment determining its velocity, 290;
development of, in the atmosphere, 291, 292;
phosphorescence excited by, 294;
Voltaic, _see_ Voltaic;
conduction of static, contrasted with Voltaic, 309;
laws of action in, distinguishing it from Voltaic, 317;
relation between 322, 323;
telegraphs working by, 323-328;
produced 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 magnetic, 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 disturbance, 15;
cause and measures of variation in, 17;
described by comets, 363, 366.

Ellipsoid, an, of revolution, mass assuming the form of, 45;
its equatorial and its polar radius, 48;
permanent axes of rotation, 76.

Elliptic motion, ratio of forces procuring, 382.

Elliptical polarization of light, 192, 193;
of heat, 267.

—— nebulæ, 409;
their connection with double stars, 411;
frequency, 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 revolution, 366, 367;
crossing the terrestrial 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 measured 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;
impressions taken from, by galvanism, 309.

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 action on the terrestrial, 55;
effects produced by external attraction influencing 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 temperature, 245.

Equator of the sun, maximum of solar heat attained in, 225.

——, dynamic, surrounding the terrestrial 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;
venial, a point whence planetary motions are estimated, _ib._;
of the planets, cause of a precession in, 66;
causes preventing their invariable correspondence with points of the
ecliptic, 79;
precession affecting the seasons, 80;
secular motion of, periodic variations, 80, 81;
eras depending on the precession of, 86, 87;
tides augmented in, 97.

Eras, astronomical, determined by the position of the major axis of the
solar ellipse, 86, 87.

Eratosthenes, the earth’s circumference measured by, 49.

Eridanus, nebulous patches crossing, 417.

Erman, M., depression of the barometer 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.

Europe, atmospheric wave passing over, 121;
causes of variation of climate in, 244;
separation of isothermal lines in high latitudes of, 245;
differences of latitude enjoying the same mean temperature, 246;
indigenous productions of, 249;
number of indigenous productions common to Australia and, 251;
number of species of forest trees, 252.

Eudoxus, Plato’s contemporary, astronomical observation of, 88.

Evaporation, conditions affecting, 269, 270.

Everest, Colonel, arc of the meridian measured by, 48.

Excentricity of planetary orbits measured, 17.

Expansion, universal law of, 271;
accuracy in measurement ensured by laws of unequal, 272;
of crystals, 272, 273;
theory of, 275, 277;
of steam, 278;
by electricity, 285.

Extra-tropical winds, 124.

Fabricius, the comet of 1556 observed by, 370;
variable star, 390.

Fahrenheit, mode of ascertaining heights proposed by, 120.

Falling stars, 420;
theories of, 422, 423.

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;
chemical origin of electricity defended by, 300;
electro-chemical decomposition defined by, 308;
remarks of, on conduction of voltaic electricity, 309;
experiments on magnetic rotation, 313;
experiment magnetizing polarized light, 318, 319;
importance of his experiment, 320;
experiment establishing the identity of magnetism and electricity,
322, 323;
his magnetic battery, 324, 325;
aid given by, in construction of telegraphs, 326, 328;
electricity produced by rotatory motion explained, 330;
his classification of substances according to magnetic qualities,
332;
quotation from, on conservation of force in electricity, 334;
magnetism 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-magnetic combinations pointed out by, 342;
his discovery of diamagnetism, 347;
experiments on magnetic action in crystals, 349;
observations on influence of heat in magnetism, 352;
definition of gravity questioned by, 354, 355;
magnetism 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, 270.

—— balls, theory of, 421.

Fires, central, subterranean, 231-237.

Fish, phosphorescent, 294, 295;
electric, 310.

Fixed stars.
_See_ Stars.

Fizeau, M., decisive experiment in proof of the undulatory theory of
light accomplished by, 202.

Flame, chemical combination evolving, 270, 271.

Flames, lambent, caused by electricity, 294.

—— divergent from the nucleus of a comet, 364.

Fletcher, Mr., periodic time of γ Virginis determined by, 398.

Flora of the Himalaya, 250;
distinct, in separate regions, 251;
condition establishing distinct, in islands, 252.

Florence, comet discovered from, 378.

Fluor-spar, its property of diminishing refrangibility of light, 196.

Fluorescence of light, definition of, 195;
vibrations of the substance producing, 196;
experiments, 197, 198.

Focus of a meteoric shower, 422.

Fog, yellow, excluding the chemical action of rays, 214.

Forbes, Professor, temperature of the boiling point ascertained by,
120;
observations of, on rayless lines, 163;
lunar heat tested by, 227;
experiments of, in polarization of heat, 264, 267.

Force, relation of, to heat, 275;
transforming solids to liquids and to vapour, 275, 277;
a power of nature, 279;
light and heat modes of, 219, 220;
heat a living, 329;
lines of magnetic, 338, 340;
conservation of, maintained in periodic variation of atmospheric
magnetism, 345;
increatable, indestructible, 353;
examples of conservation of, 354;
fundamental principle of conservation, 357;
influence and action of the gravitating, 424, 426.

Forces, the unknown cause of motion, 5 _et passim_;
counteraction of solar and tangential, in planetary motion, 8;
adjustment of, ensuring the permanence of the solar system, 11, 12;
three partial, causing perturbation in planetary motion, 14, 15;
excess of equatorial diameter the origin of, 27, 28;
three, disturbing lunar motions, 34, 35;
determining planet forms, 44, 45;
producing tides, 91, 92;
combining to form the centrifugal, 100;
acting on molecules of matter, 102, 105;
producing capillary phenomena, 114;
latent, in nature, 279, 280;
one universal power, the root of all, 321;
exact balance of, in electricity, 334;
kindred and convertible, 353;
developing comets’ tails, 375;
determining the forms of orbits, 382, 383;
maintaining the stability of the solar system, 426;
mutual relations of, 427.

Forests, change produced in the atmosphere by, 241, 243;
number of species of trees found in American and European, 252.

Formentera, quadrant of the meridian passing through, furnishing a unit
of linear measure, 89.

Fornix, nebulous patches crossing, 417.

Forster, Lieutenant, conversation carried on by, across Port Bowen
Harbour, 136.

Fossil plants, an evidence of change in temperature, 74.

Fourier, mean temperature of space according to, 119;
rate of decrease in the earth’s central heat computed by, 232.

Fox, Mr., temperatures in mines tested by, 228, 229;
law of paramagnetic force ascertained by, 338;
observations in mines, proving agency of electro-magnetism, 346.

France, arcs of the meridian measured in, 48;
unit of linear measure in, 89;
mode of arithmetical computation, 90;
atmospheric pressure in, 120;
cliffs of, seen from Hastings, 157.

Fraunhofer, M., discovery of rayless lines in the solar spectrum, 162;
comparative refrangibility of rays ascertained by, 163;
data furnished by, to determine the dispersive power of rays, 165;
his discovery determining the length of waves independently of
refraction, 201;
spectrum of an electric spark observed by, 289.

Freezing, temperature required for, under pressure, 271;
theory of, 276.

Fresnel, M., his testimony in favour of the undulatory theory of light,
171;
theory of refraction, 183;
discoveries in polarization of light, 191, 193.

Freyberg, green plants found in mines at, 253.

Friction evolving heat, 274, 275;
electricity, 282, 283.

Fringes of coloured light bordering shadows, 174, 175;
produced by interference of polarized rays, 194.

Fulgorites, found in Silesia, 293.

Fundy, the Gulf of, cross tides pouring into, 94.

Gage, Mr., experiments of, on magnetism, 315.

Gales.
_See_ Winds.

Galileo, laws affecting music discovered by, 145;
his method of finding distances of fixed stars, 388.

Galle, Dr., Neptune’s place communicated to, by Le Verrier, 62.

Galloway, Mr., sun’s motion proved by, 405.

Galvani, Professor, peculiar effects of electricity suggested to, 297.

Galvanism, phenomenon suggesting the theory of, 297;
batteries, 298, 300;
heat and light evolved by currents of, 300, 304;
decomposition and composition, 307, 308;
applied to plating and gilding, 309;
effect of heat on, 310;
effect of, on the senses, _ib._;
fish exhibiting analogous phenomena, 310, 311;
phenomena exhibited by currents of, on magnets, 312, 314:
intensity of a current measured, 315;
conditions obtaining a circuit in, 332.

Galvanometer, the principle of its construction, 315;
experiment by means of, identifying magnetism and electricity, 322,
323.

Gambart, M., parabolic elements of a comet computed by, 367.

Gamma Andromeda, colours of, 401.

—— Aquarii, planetary nebula near, 412.

—— Hydræ, a variable star, 391.

—— Leonis, focus of a meteoric shower in, 422.

—— Sagittarii, cluster of the Milky Way round, 387.

—— Virginis, eclipse in, 397;
orbit of the revolving star determined, 398.

Ganges, the, tidal wave at the mouths of, 94.

Gardner, Mr., extent of diametrically opposite lands estimated by, 244.

Gases, conditions retaining matter in the form of, 104, 105;
combinations of, 111;
transmission of radiant heat through, 258;
expansion of, 271;
voltaic spectrum modified by, 303;
effect of heat on the conducting powers of, 309.

Gassiot, Mr., experiments of, on the electric discharge, 306;
connexion between magnetism and light discovered by, 321;
electric apparatus improved, 328.

Geneva, the Lake of, experiment on the velocity of sound in, 135.

Gensanne, M., increasing temperature of mines tested by, 228.

Geographers, lunar motions important to, 42.

Geological changes, probable cause of, 77.

Geology, the lessons of, 326.

Georgia Island, S., excess of cold in, over corresponding latitudes,
241.

Germany, shooting stars seen from, 421.

Gibraltar, the Straits of, turning aside the tidal wave, 98.

Giromagny, temperature of the lead-mines of, 228.

Glass, effect of cohesion on plates of, 106;
musical notes elicited from rods and plates of, 144-147;
transmission of waves of light in, 177;
polarizing light, 184, 185;
elliptical polarization produced by, 193, 194;
used in photography, 207;
impressions on, from bodies in contact with, 220;
impressions on, traced by electricity, 221;
transmission of radiant heat by, 259;
by coloured, 261, 262;
its temper altered by magnetism, 352, 353.

Globular clusters of nebulæ, 413-415.

Glow-discharge observed by Captain Bonnycastle, 295, 296.

Gold, action of, on light, 173.

Good Hope, the Cape of, icebergs drifted to, 101.

Goodricke, Mr., variable stars discovered by, 391;
opaque bodies represented as revolving round fixed stars by, 394.

Graham, Mrs., account of an earthquake by, 234.

Graham’s compensation pendulum, 272.

Gravitating force of the sun, 365, 424, 425.

Gravitation, offices of, in the material creation, 1, 2;
process of reasoning in ascertaining the law of, 3;
law determining its intensity in the solar system, 5;
complex action of, by attraction in mass and in particles, 6;
increase of, towards the poles of the earth, 45;
calculations founded on its increase, 49-51;
in a mine, its excess over surface, 57;
action of, modifying tides, 92, 93;
law, universally acting on matter, 105;
the air subject to, 117;
influence of, in motions of the heavenly bodies, 382, 383;
double stars revolving by, 398;
stellar systems subject to, 400;
influence of, on nebulæ, 416;
a general law of the visible creation, 424;
mode of its action, 425, 426.

Gravity, centre of, in spheres, effect of impulses passing through, 7;
of the solar system, invariable plane passing through, 23;
straight line described by, 24;
action of, in determining the figure of the earth, 44, 45;
definition irreconcilable with the conservation of force, 354, 355;
question of its transmission, 355, 356.

Great Bear, the nebulous zone passing, 416.

—— Gobi, the, effect of the expansion of air over, 124.

Greeks, astronomical observations of, confirming results of analysis,
38.

Greenland, ocean on the northern coast of, 94.

Greenwich, lunar distances computed for, 43;
quadrant of the meridian passing through, furnishing a unit of linear
measure, 89;
periodic circuits of winds, 125.

Grimaldi, coloured fringes bordering shadows described by, 175.

Groombridge, velocity of his proper motion, 404.

Grotthus, the transmission of voltaic electricity investigated by, 298.

Grove, Mr., copper and zinc plates electrified by, 220;
substances radiating heat of different refrangibilities enumerated
by, 257;
the transmission of voltaic electricity investigated by, 298;
electric heat tested by, 301, 302;
remarks of, on carbon, 302, 303;
on the voltaic arc, 304, 305;
remarks of, on light and heat, 319;
electric apparatus improved by, 328;
his definition of the ethereal medium, 355.

Grylli, supposed delicate sense of hearing in, 132.

Guanaxato, temperature of the silver-mine of, 228.

Gulfs separating stars, 390.

Gum-guaiacum, chemically affected by rays of the solar spectrum, 203;
condition of its sensibility to light, 206;
effect of red rays on, 209;
used in experiments on parathermic rays, 217, 218.

Gum-lac, electrical intensity measured by means of, 286, 287.

Gymnotus electricus, the, 310.

Haidinger, M., experiments of, proving water an essential part of
crystals, 107.

Hail, formation of, 270.

Hales, his calculation of the amount of surface exposed by the leaves
of a helianthus, 243.

Hall, Mr., achromatic telescope constructed by, 165.

Halley, elements of a comet’s orbit computed by, 362;
return of his comet, 363;
changes in its aspect, 363, 364;
records of, 365;
no solid nucleus in, 374;
cause of its luminous sectors, 376;
Sir John Herschel’s observations on, 378.

Hare, the, comet observed near, 372, 373.

Harmonics of the fundamental note in music, 140, 141.

Harmony, property of sound regulating, 131;
definition of, vibrations producing, 142.

Harris, Sir William Snow, experiments of, in electricity, 287, 288;
lightning-conductors invented by, 293.

Harrison, pendulum invented by, 272.

Hastings, coast of France distinctly seen from, 157.

Heat affecting the form of crystals, 107;
evolved in chemical combinations, 110;
irregular decrease of, in the atmosphere, 119;
maxima of, in the solar spectrum, 215;
peculiar chemical quality of, in parathermic rays, 218;
impressions traced by, 220-222;
periodical variations in the sun’s, 225;
different proportions of solar, reaching the planets, 225, 226;
effect of the terrestrial atmosphere on lunar, 227;
mode of its development in opaque bodies, _ib._;
sources of terrestrial, 228-238;
irregular distribution of, 239-247;
laws affecting its radiation, 257;
its transmission, 258-262;
polarization of, 264-267;
undulatory theory, 267;
absorption and reflection of radiant, 268;
phenomena caused by radiation of, 269;
accumulation of, producing light, 270;
expansive force of, 271, 272;
modes of propagation, 273, 274;
produced by motion and equivalent to it, 274-277;
laws regulating the force of artificial, 279, 280;
power evolved by application of, 280;
identical in nature with sound, 281;
electrical, 288;
sheet-lightning caused by, 294;
phosphorescence, 294;
developed by voltaic electricity, 301, 302;
effect of, on electrical conductors, 309;
connexion between the production of electricity and, 310;
its direct relation to magnetism and electricity, 319, 320;
mechanical power and convertible forces, 329;
terrestrial magnetism attributed to the action of, 333;
measured by electric currents, 334;
affecting atmospheric magnetism, 344;
fundamental principle of the dynamic theory, 357.

Helena, St., distinct flora of, 252.

Helix, circular and elliptical, described in polarization of light,
192, 193;
electrical experiments by means of, 314;
induction of, increasing electric power, 322, 323.

Heller, his observations on the comet of 1556, 370, 371.

Helmholtz, Professor, power of chemical force estimated by, 112;
his calculation of the chemical force developed by combustion, 278;
of the amount of latent force in our system, 280.

Hemisphere, cause of excess of cold in the southern, 241;
superficial extent of land in northern and southern, 244.

Henley, Mr., magneto-electric machine constructed by, 325.

Henderson, Professor, parallax of α Centauri calculated by, 387;
of Sirius, 389.

Henry, Professor, experiments of, on magnetism, 315.

Herapath, Mr., his view of elastic force preferred to Sir Humphry
Davy’s, 276.

Hercules, eclipse of a double star in, 398;
globular nebulous cluster, 414.

Herschel, Sir William, observations of Saturn’s and Uranus’s satellites
by, 32, 33;
theory of, regarding the solar constitution, 41;
cause of effects of light in eclipses according to, 42;
rotation of Jupiter’s satellites determined by, 70;
mutual independence of light and heat, 214, 215;
influence of the sun’s spots on heat, 225;
point of maximum heat in the solar spectrum, 263;
comet of 1811 observed by, 374;
its luminous envelopes examined, 375;
the Milky Way examined by, 385;
his discovery of the orbital motions of double stars, 388;
catalogue of double stars by, 395, 396;
periodic time of γ Virginis determined by, 398;
eclipse of a double star observed, _ib._;
binary system discovered, 400;
remarks on the motions of the stars, 405;
nebulæ 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 decrease of density in the atmosphere, 118;
mean temperature of space computed by, 119;
height of Etna measured, 120;
his explanation of anomalies in atmospheric phenomena, _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;
experimentalising apparatus, 188;
discovery of epipolic light, 197;
discoveries in photography, 205, 206;
analysis of the solar spectrum, discovery 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 contraction of diameter in comets, 378;
comparative lustre of stars measured by, 384, 385;
the Milky Way described, 385, 386;
number of stars in a group of the Milky Way computed, 387;
variable star discovered, 391;
remarks 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 double star observed, 397;
orbits determined, 398, 399;
observations on colours of double stars, 401;
light of α Centauri compared with the moon’s by, 404;
light of the fixed stars calculated, _ib._;
observations on nebulæ corrected, 407;
catalogues of nebulæ, 408;
nebulæ discovered by, 409;
annular nebula described, 410;
magnitude of planetary nebulæ computed, 412;
globular nebulous cluster described, 413;
law of gravitation ascribed to nebulæ, 416;
nebula round η Argus described, 418;
his work on Nebulæ, 419.

Herschel, Miss, Encke’s comet seen by, 365;
catalogue of nebulæ, 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 astronomy, 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 catalogue of the stars, 392.

History corroborated and corrected by astronomy, 87, 89.

Hoar-frost, cause of, 269.

Holtzmann, M., opinion of, with regard to the vibrations of polarized
light, 223.

Hoogly, the, bore of, 94.

Horizon, effects produced by the denser stratum of air in, 157, 158.

Horologium, nebulous patches in, 417.

Horton coal-mine, experiments with the pendulum in, 57.

Hours, cause of their mal-correspondence over the globe, 86.

Hudson’s Bay, tide in, 98.

Humboldt, his sufferings from rarity of the atmosphere, 118;
his explanation of the apparent greater acuteness of hearing observed
at night, 135;
observations of, in mines, 228;
causes of disturbance in the equal diffusion of heat enumerated by,
240;
identical productions of the Old and New World found by, 251;
his distribution of palms and grasses, 252;
green plants found growing in mines by, 253.

Hunt, Mr., coloured image of the solar spectrum obtained by, 209;
image obtained in England, 213;
his experiments in tracing images by juxtaposition of bodies, 220,
221;
experiments on the condensing power of rays, 223.

Hurricanes, origin and cause of, 125, 126;
curve described by the axis of, _ib._;
their extent and velocity, 126,127;
phenomena resulting from their revolving motion, 127;
laws of, making avoidance possible, 128.

Huygens, theory originated by, 169.

Hydrogen, proportion of, in water and gases, 111;
spectrum from, 303;
separated from water by electricity, 307.

Hygrometer, dew-point measured by, 269.

Hyperbolic motion, ratio of forces procuring, 382.

Iapetus, seen by Mr. Lassell, 33.

Ibn Junis, progress of science in his time, 90.

Ice, formation of, 271;
force acting in its formation, 276;
stopping the current of voltaic electricity, 309.

Icebergs, drifting of, 100, 101;
farthest range of northern and southern, 241;
effect of electricity in collisions, 284.

Iceland spar, its property of double refraction, 181;
polarized ray analyzed by, 187;
transmission of radiant heat by, 258;
electricity elicited from, 284.

Illumination, comparative, of objects, experiments determining, 227.

Images, coloured, of the solar spectrum, 208-211;
traced by contact and juxtaposition of bodies, 219, 220;
by electricity, 221;
by media absorbing hot rays, 222.

India, arcs of the meridian measured in, 48;
discovery of Saturn’s ring, 66;
ancient monument of astronomical knowledge, 85;
observations confirming the antiquity of astronomical science in, 88.

Indian Ocean, the tidal wave in, 94;
monsoons blowing over, 124.

Induction, law of, in electricity, 285, 286;
magnetic, 314, 315;
phenomena of, produced by electric currents, 324;
illustrated by the Atlantic telegraph, 325, 326;
velocity of electricity modified by power of, 327;
possibility of electro, furnishing a motive power, 328;
of electricity by rotation of magnets, 330-332;
as possessed by magnets, 336;
paramagnetism evolved by, 337;
means of accelerating, _ib._;
subject to the laws of mechanics, 338;
analogy between electric and magnetic, 341;
of heavenly bodies, affecting terrestrial magnetism, 346, 347;
diamagnetic substances capable of, 348.

Indus, comet passing through the constellation of, 379.

Inequality, the, of Jupiter and Saturn marking historical epochs, 88.

Insects, law of their dispersion, 255.

Instruments, musical, 143, 149, 150;
imitating articulation of letters, 151, 152.

Insulation in electricity, 285.

Interference, laws of, neutralizing undulations, 138, 139;
the theory of, referred to a general law, 169.

Iota Cetæ, comet observed near, 372.

—— Orionis, a nebulous star, 411.

Ireland, progress of the tidal wave towards, 94.

Iron, distilled, 305;
rotation of its particles, _ib._;
magnetized by electricity, 314, 315;
magnetic properties of, 332;
rendered paramagnetic, 336, 337;
magnetic and electric properties of, 347;
elasticity of, affected by magnetism, 352.

Islands, character of their floras, 252.

Isogeothermal lines of temperature defined, 238, 239;
parallel with the isothermal lines, 246.

Isomorphous crystals, 109.

Isothermal lines of temperature defined, 240;
latitudes of, deviation from the line of the equator, 245;
formula determining, 246;
similarity of vegetation in the same, 253.

Italy, local attraction, occasioning inaccuracy in measurement, 48.

Ivory, M., his method of computing heights, 120;
his theoretical investigation of planet forms, 44;
deduction from measurement of arcs of the meridian, 48.

Jacob, Mr., discovery of Saturn’s ring by, 66;
periodic time of α Centauri determined by, 399;
periodic time of 70 Ophiuchi, 400.

James, Colonel, measurements of, in the General Survey of Great
Britain, 47;
density of the earth determined by, 58.

Jamin, M., remarks of, on substances producing elliptical polarization,
193.

January, epoch of its beginning the year, 85.

Jews, denominations of time in their calendars, 85.

Josephstadt, discovery of a comet from, 367.

Joule, Mr., heat considered a mechanical force by, 275;
his view of elastic force, 276;
amount of latent force in a pound of coal, computed by, 278;
furnishing data to Professor Thomson, 279;
quantity of heat generated in a unit of time by electricity computed
by, 302;
powerful magnet obtained by electricity, 315;
electric machines constructed by, 328;
experiments proving heat and mechanical power convertible, 329.

Jovial system, mass of the whole, 55.

Julian Calendar, year of, the first of our era, 86.

June, 1833, reappearance of Saturn’s rings, 67;
coincidence of times in, 84.

Juno, the diameter of, 56;
astronomical tables of, 63.

Jupiter, rotation of, distinguished from the other planets, 7;
periodical inequality in his motions, 15;
discovery of telescopic planets between Mars and, 20, 21;
diameter of, 21;
his position with respect to the equator of the solar system, 24;
inequalities in the motion of, apparently anomalous, 25, 26;
his mass proved not homogeneous, 29;
eclipses, 30, 31;
compression of his spheroid computed, 39;
eclipsed by Mars, 42;
mass of, compared with the sun, 55;
his diameter, 56;
increase of density in, 58;
astronomical tables of, 60;
rapid rotation, 66;
period of a year in, _ib._;
effect of his disturbing energy, 81;
photographic images of, 226;
light reflected by his atmosphere, 227;
action of, on the comet of 1770, 361, 362;
on Halley’s comet, 362, 363;
comet revolving between the orbits of the earth and, 367;
future influence of, on comets, 369;
comet nearly approaching his fourth satellite, 370;
comets having their perihelia in his orbit, 381.

——, orbit of, revolutions of its major axis, source of variation in
excentricity, 17;
slow revolution of its nodes, decrease in its inclination to the
ecliptic, 19.

—— with his satellites, an epitome of the solar system, 27;
effect of his excessive equatorial diameter on their orbits, 28;
satellites, libration in, 69;
rotation of, 70.

Kane, Dr., Polar Sea discovered by, 94;
cold of Northern Greenland marked by, 247.

Kappa Crucis, cluster of coloured stars round, 419.

—— Draconis, seen in the pole of the equator, 88, 89.

Karsten, Mr., impressions made on glass by electricity, 221.

Kasan, summer and winter mean temperature of, compared with Edinburgh,
246, 247.

Kater, Captain, approximate length of the pendulum, determined by, 89.

Kempelen, M., speaking-machine invented by, 151.

Kepler, paths, revolutions of planets discovered by, 5;
his law regarding the mean distances of planets from the sun, 19;
law of, applied to calculating distances, 53, 54;
rapidity of planetary revolutions determined by his law, 66;
his law finding areas described by heavenly bodies, referred to, 360.

Kew, balloon ascent from, 119.

Knoblauch, position of the magnecrystallic axis proved by, 349.

Knowledge, limited nature of human, 2.

Kotzebue, stratum in the ocean discovered by, 101.

Kratzenstein, M., instrument invented by, articulating words, 151.

Kupffer, M., observations of, on temperature, 246.

La Basilicata, earthquake in, 234.

Lacaille, his globular nebulous cluster, 414;
nebula, 418.

La Grange, his investigations into the stability of the solar system,
20, 21;
greatest discovery of, 23.

La Hire, phases in comets observed by, 380.

La Place, stability of the solar system proved by, 20;
principle in astronomical calculations established, 23;
angle of inclination fixed, 24;
his theory accounting for acceleration in the moon’s mean motion, 36,
37;
result of observations compared with his theory of Jupiter’s
satellites, 55;
theory of planetary motion, 65, 66;
universal epoch proposed by, 87;
scientific observations complementing historical records, 87;
date fixed by, for the lunar tables of the Indians, 88;
justifies Newton’s theory of tides, 96;
density of a liquid column estimated by, 114;
action of the earth on a comet, 359;
change in a comet’s orbit, 361;
cause of error in Clairaut’s calculation pointed out by, 363;
opinion of, as to the comet of 1682, 378.

“Lake of the Gazelles” ascribed to an effect of reflection, 157.

Lalande, epochs of conjunctions computed by, 42.

Lambda Herculis, general motion of the stars determined by, 405.

Land, dry, comparative extent of, on the globe, 242, 244;
extent of, in diametrical opposition, 244.

Landscapes in chiaroscuro, produced by photography, 207.

Languages, resemblances and analogies between, 255, 256.

Lapland, arcs of the meridian measured in, 48;
transit of Venus observed in, 53.

Laroche, M., his experiments on transmission of radiant heat, 259, 261.

Lassell, Mr., satellite of Saturn discovered by, 32;
observations of, on Uranus’ satellites, 33;
his discovery of Neptune’s satellite, _ib._;
observations on Saturn’s rings, 66.

Latent heat, energetic action of, on matter, 275-277.

Latitude, the, of a planet defined, mode of obtaining, 9, 10;
cause of periodical inequalities in, 15;
perturbations from action of the perpendicular force, 18;
moon’s motion in, disturbed, 35;
effects of disturbance, 38;
data of, used in computing a planet’s place in the heavens, 58-60;
conditions ensuring the invariability of geographical, 76, 77;
change effected by nutation in, 81;
climate not invariable in the same, 239;
degrees of, where diminution of mean heat is most rapid, 244, 245;
the same mean temperature in different, 246, 247;
of wine-growing, 250;
magnetic storms varying with, 345.

Layang, observations made at, 1100 years before the Christian era, 88.

Le Sueur, specific diversity of marine animals observed by, 254.

Le Verrier, M., principle of La Grange applied by, 21;
zone of instability found, _ib._;
discovery of Neptune, 62;
his observations on atmospheric waves, 122;
comets identified by, 362;
his table of comets’ orbits, _ib._

Lenticular nebulæ, 409;
haze surrounding the sun, 412.

Leo, nebulous system in, 417.

Léon-Faucault, M., velocity of light in air and water ascertained by,
202.

Lerius, banks of algæ found by, 253.

Leslie, Professor, compression of air calculated by, 78;
experiments on radiation of heat, 257.

Lexel, observations of, on the comet of 1770, 361, 362.

Libra, the five great planets in conjunction near, 42.

Librations of the moon, of Jupiter’s satellites, 69;
of α Centauri, 399.

Lichen, red, growing on snow, 249.

Light, rate of its velocity, 31;
truth deduced from the uniformity of its velocity, 32;
from the aberration of, _ib._;
period required to reach the earth from α Centauri, 54;
action of the atmosphere on, 153;
conditions regulating the transmission and reflection of, 156;
loss of, transmitted by the horizontal stratum, 157;
effects of transmission through the atmosphere, 158;
Newton’s analysis of, 159;
Brewster’s, 161;
phenomena disproving Newton’s theory, 167, 168;
undulatory theory, 168-170;
conditions affecting its intensity and colour, 170;
experiments testing the mutual relations of colour and, 171-175;
law of its absorption identical with a law of motion, 175-177;
repeated vibrations producing the sensation of, 178;
polarized, defined, 179;
modes of polarization, substances polarizing, 179-185;
accidental polarization of, 195;
degraded, or fluorescence, 196;
objections to the undulatory theory analyzed and disproved, 199-202;
comparative velocity of, in air and water, 202;
pictures produced by reflected, 203-207;
rays of, independent of heat, 214, 215;
comparative amounts of solar and lunar, 225;
different measures of illumination from, 227;
influence of, on vegetation, 249;
colour developed without the influence of, 253;
separated from heat by Melloni, 265;
produced by accumulation of heat, 270;
law regulating the force of artificial, 279, 280;
electrical, 288, 289;
produced by voltaic electricity, 302;
stratifications of the electric, 306;
influence of magnetism and electricity on, 319, 320;
of comets, 379-381;
of the fixed stars, 401-404.