Part 54

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.

Lightning, development of heat exhibited by, 276, 277; experiment showing the velocity of, 289; theory of, 292; the back stroke, _ib._; force of the direct stroke, 293; sheet, 294; effect of, on the compass, 312.

Lime, carbonate of, variety of form in its crystals, 107; invariable form ultimately assumed by, 109.

Lines of magnetic force, 338, 339; experiment ascertaining the form of, 339, 340; terrestrial, 341, 342; extensive courses of, 344; a connected system, 345; diamagnetic, 348.

Lion, the, conjunction of planets in, 42.

Liquids, balance of forces constituting, 104, 105; action of capillary attraction on, 113-116.

—— possessing the property of circular polarization of light, 190, 191-193.

Liquids, conditions affecting the transmission of radiant heat by, 263; evaporation from, 269; expansion of, by heat, 271; propagation of heat in, 273; action of heat as a mechanical force on, 275-277.

London, retarding of the tidal wave between Aberdeen and, 94.

——, pendulum vibrating in its latitude, a standard of measurement, 89; fulgorites exhibited in, 293.

Long, Dr., his attempt to measure distances of fixed stars, 388.

Longitude, mode of reckoning mean and true, 9; of the perihelion and of the epoch defined, 10; cause of periodical perturbations in, 14; calculation from the moon’s influence on the sun’s, 55; data of, used in computing a planet’s place in the heavens, 58-60; change effected by precession and nutation in, 81.

Lloyd, experiments of, in polarization of heat, 264.

Lubbock, Sir John, theory of planetary motion completed by, 64; his theory of shooting stars, 423.

Lumière cendré, definition of, 227.

Lunar distance, defined, 43.

—— theory, mean distances obtained from, 43.

—— tides of the terrestrial atmosphere, 121.

Lundahles, M., motions of heavenly bodies investigated by, 405.

Lupus, position of, 390.

Lussac, Gay, M., uniting of gases by volumes discovered by, 111; ascent of, in a balloon, 118; course of a lightning flash ascertained by, 292.

Lutetia, diameter of, 56.

Lyell, Sir Charles, his theory of changes of temperature in the northern hemisphere, 75; annual number of volcanic eruptions computed by, 233; volcanic phenomena related by, 234.

Lyncis 12, a triple star, 395.

Lyra, a variable star in, 391; a double star, 395; nebula, 410.

Machinery, relations of, to force, 353.

Mackintosh, Sir James, quotation from, illustrating the essential advantages of study, 1.

Maclear, Mr., parallax calculated by, 387.

Madeira, vegetation of, 252.

Madras, Saturn’s ring discovered from, 66.

Magellanic clouds, the, 417, 418.

Magnecrystallic action, 349; temperature affecting, 352.

Magnetic bodies, difference in power of, 347.

—— elements, the three terrestrial, 343.

—— equator of the earth, 343.

—— meridian, the, mean action of forces determining, 343.

—— poles of the earth, 343.

—— storms, 344; varying with latitude, 345, 346.

Magnetism, source of, 318; producing electrical phenomena, 322, 323; rotatory motion a source of, 330; classification of substances, with regard to their susceptibility of, 332; residing in substances after two manners, 335; experiment illustrating the forces of, 338; antithesis, its general character, 339; form of its lines of force, 339, 340; analogous properties of electricity and of, 340, 341; terrestrial, 342-347; connexion between solar and terrestrial, 344; action of, in crystals, 349-351; influence of temperature in, 352; affecting elasticity of matter, 352, 353; a property of the ethereal medium (?), 356, 357.

——, electro, discovery, importance of the science, 312; rotation effected by, 313, 314; electric intensity measured, 315; action of currents in, defined, 316; Ampère’s theory of, 317, 318; causing rotation of polarized rays, 319; action of, on light, 320; accidental combinations, 342; influencing metalliferous deposits, 346.

Magneto-electricity, principle suggesting, 322; machine constructed on the principle of, 325; relation of heat to, 329.

Magnets, influence of, on electric light, 307; fish possessing the power of making, 311; effect of an electric stream on, 312-314; obtained by electricity, 315; power of electro, measured, 315; cylinders acting as, 316, 317; producing electrical effects, 322, 323; evolving electricity by rotation, 330; classification of substances in relation to, 332; polarity a property of, 336; effect on themselves of imparting paramagnetism, 337; experiment showing the lines of force of, 338; properties of, indestructible by subdivision, 338, 339; the earth reckoned among, 342; planets reckoned among, 346; action of an electro, on copper, 351.

Maguire, Captain, his observations on magnetic storms, 345, 346.

Malo, St., rising of the tide at, 98.

Malus, M., discovery of polarization of light by, 195; attempts of, to polarize heat, 264.

Malta, observations on Saturn’s rings made at, 66.

Manchester, thunderstorm near, in 1835, 292.

Mankind, distinct tribes of, 255; limited perceptions of, 267.

Marcet, M., rate of increase in temperature below the earth’s surface calculated by, 230.

Marco Polo, atmospheric effects observed by, in ascending mountains, 118.

Marine plants, laws regulating their distribution, 252, 253; animals, specific localities of, 254.

Mariner’s compass. _See_ Compass.

Mars, used in illustrating the possible effects of the radial distributing force, 19; telescopic planets between Jupiter and, 20, 21; diameter of, 21; mean distance from the sun, _ib. note_; eclipse of Jupiter by, 42; parallax found by observing his oppositions, parallax of, 53; internal structure, 58; astronomical tables of, 63; climate of, 225; approach of the comet of 1770 to, 362; comets having their perihelia in his orbit, 381.

Marseilles, transit of a comet across the sun observed from, 374.

Masses, of the sun, of planets and their satellites, computations finding, 55, 56.

Mathematics, use of, in the study of astronomy, 2.

Matter, theory of its constitution, 102; hypotheses as to forces uniting its particles, 103, 104; counterbalancing action of elasticity and cohesion, 105; crystallization common to all forms of, 109; indestructibility of its particles, 110; composition of unorganised bodies, subject to permanent law, 110, 111; agent composing or decomposing, 112; mode of ascertaining the magnetism of, 335; increatable, indestructible, 353; proportion of, to spare, 424.

Matteucci, M., effect of electricity on polished silver observed by, 221; experiment showing polarization by electricity, 286; doubts of, on the polarity of diamagnetism, 348 _note_; experiments on magnetic action in crystals, 350; observation on the action of compression, 352.

Maury, Lieutenant, calms named by, 123.

Measurement of astronomical distances, formula assisting, 43.

Mechain, M., Encke’s comet seen by, 365.

Mechanical equivalent of heat, 275.

—— engines, incapable of generating force, 279.

Mediterranean, the, conditions of, shutting out the tidal wave, 98; hurricane in, divided into two storms, 126; vegetation of, 252.

Medium, ethereal, transmitting magnetism, 344; density of, 356; probable relations of, to gravity, _ib._; experiment testing its magnetic properties, 356, 357; functions of, 357; pervading the visible creation, 358; unsolved question touching, 365; a cause of accelerated revolutions of comets, 366, 367; direction of its increase in density, 367.

Medium occupying space, 424.

Medusa tribes, the, phosphorescent brilliancy of, 295.

Melloni, M., experiments of, in photography, 214; his application of the principle of thermo-electricity, 333; experiments of, in transmission of heat, 258-263; fixing the maximum of heat in the solar spectrum, 264; in polarization of heat, 264-266; light separated from heat by, 265.

Melville Island, height of the thermometer in, in January, 247.

Mercury, inclination of his orbit to the plane of the ecliptic, 21; eclipse of, 42; cause of his rotation unknown, 65; ellipticity of his orbit compared with the terrestrial, 74; climate of, 226; comet revolving between the orbits of Pallas and, 367; attraction of, determining a comet’s orbit, 369; comets revolving in his orbit, 381; velocity of, 400.

——, propagation of heat in, 273; rotating by electricity, 314.

Meridian, constant, of high water, 92.

——, mode of determining the magnetic, 343.

Meridians, size and form of the earth determined from, 46; measurement of arcs, 47; anomalies from local attraction, 48; result of the computations, 48, 49; permanent, of the moon, 69, 70.

——, magnetic, influencing the direction of metallic veins, 346.

Messier, comet of 1770 observed by, 361; Encke’s comet seen by, 365; nebula described by, 409.

Metallic salts, action of the rays of the solar spectrum on, 203.

—— springs used in construction of musical instruments, 143; rods giving musical notes, 144.

Metallic surfaces, polarized light reflected from, 193; plates, impressions on, from bodies in contact with, 220.

Metals, expansion of, by heat, 271; propagation of heat in, 274; transmission of electricity by, 284; electricity developed by oxidation of, 298; determining the appearance of a spectrum of voltaic flame, 303; distilled in the voltaic arc, 304, 305; electro-plating of, 309; properties of, modifying electric susceptibility, 333; magnetism an agent in the formation of, 346.

Meteor, the bursting of a, 118.

Meteors, 420; theory of, 421-423.

Meteoric stones, proofs of their foreign origin, 420, 421; shower of, 421, 422.

Mètre, adopted by the French as their unit of linear measure, 89.

Mica, polarization by induction effected with, 286.

Milky Way, the, described, 385; Sir John Herschel’s description, 385, 386; “Coal Sacks,” 386; stars composing, 286, 287; zone of stars crossing, 390; position of variable stars with regard to, 395; crowding in, apparent only, 405; orbit in the plane of, 406; relation of, to the stellar universe, 407; nebula resembling, 409; its quarter of the heavens, 414, 415; dividing the nebulous system, 416, 417; great nebula in, 418; remote branches of, 419.

Minerals, possessing the phosphorescent property, 294.

Mines, cause of increased temperature in, 229; green plants growing in, 253.

Mira, periods of its fluctuations in lustre, 390.

Mirage, supposed cause of, 157.

Miraldi, rotation of Jupiter’s satellite determined by, 70.

Mitscherlich, M., his experiments on crystals, 107; discoveries, 108; experiments of, in expansions of crystals, 272.

Mocha, meteors falling at, 421.

Moignot, M., crystals compressed by, 189.

Moisture, an indispensable requisite for vegetation, 248; transmission of electricity effected by, 284, 288.

Molecular polarity, produced by electricity, 282; attraction, electricity developed by destruction of, 284.

—— structure affecting transmission of electricity, 303.

—— vortices, hypothesis of, accounting for the absorption of light, 177.

Molecules, material, attraction and repulsion of, 103; effect of elasticity and cohesion on, 104-106; uniting to form crystals, 107-109; extreme minuteness of ultimate, 110; of ether, modes of their vibration in natural and polarized light, 193; in fluorescent light, 196, 197; images traced by the mutual action of, 219-222; arrangement of, connected with magnetism, 350-352.

Mollusks, distinct species of, 254.

Monocerotis 11, a triple star, 395.

Monsoons, theory of the, 123, 124.

Months, antiquity of, as a measure of time, 85.

Moon, the, force restraining, 4, 5; mean distance of, from the earth, 4; results effected by her nearness to the earth, 7; annual rate of decrease in her orbit’s excentricity, 17; average distance of, from the earth’s centre, period of her circuit of the heavens, 34; her periodic perturbations, 35-38; causes assigned for acceleration of her mean motion, 36, 37; eclipses of, 39, 40; longitudes determined by observations of, 42, 43; her mean horizontal parallax, 52; sources whence her mass may be determined, 55, 56; her diameter, 56; rotation of, 68; librations, 69; mountains, 70; precession resulting from her attraction, 79-81; influence of, producing tides, 91, 92, 96-98; period of her declinations, 97; atmospheric equilibrium disturbed by her attraction, 121; cause of her apparent increased magnitude in the horizon, 158; photographic image of, 214; comparative amount of light emitted by, 225; cause of the rarity of her atmosphere, 226; increased intensity of light at full, _ib._; effect of the terrestrial atmosphere on heat radiated from, 227; cause of acceleration in the mean motion of, 366; light reaching the earth from, 404.

Moorcroft, herbarium collected by, 250, 251.

Moser, Professor, mutual influence of bodies in contact tested by, 219, 220.

Mossotti, Professor, his analysis to prove the identity of the cohesive force with gravitation, 103, 104; his definition of gravity, 355.

Motion, a law of the universe, 274; perpetual, impossible, 279.

Mountains, anomalies in measurement caused by, 48; rarity of atmosphere on, 118; cause of perpetual snow, 119; modes of determining heights of, 120; becoming new centres of motion in hurricanes, 126; influence of chains on temperature, 241, 242; cause of éboulemens in, 271; tops of, fused by lightning, 293.

——, lunar, effect of solar rays passing between, in eclipses, 41; influence of, on the moon’s motions, 96; three classes of, 70.

Mu Herculis, direction of solar motion with regard to, 406.

Multiple systems of stars, 395.

Mundy, Captain, mirage described by, 157.

Music, comparison instituted of sympathetic notes in, 2; regulated undulations of sound producing, 142; instruments of, 143; experiments by means of vibrating plates, 144-146; sympathetic vibrations, 147, 148; experiments showing, 148, 149.

Musical instruments constructed by Professor Wheatstone, 143.

Naples, comet discovered from, 370.

Nautical Almanac, computations for calculating longitudes, 43; time calculated by, 84.

Navigation, importance of lunar motions in, 42; laws of storms to be observed in, 127, 128.

Neap-tides, 96, 99.

Nebulæ, number and general aspect of, 407; catalogues, 407, 408; classes, 408; irregular, 408, 409; of definite form, 409; spiral, 409, 410; annular, 410, 411; elliptical, double, 411; distance of a nebulous star discoverable, 411, 412; aspect and colour of planetary, 412; elliptical common, 413; globular clusters, 413-415; resolution of, 415; star clusters, 415, 416; probable law of motion, 416; distribution of, 416, 417; the Magellanic clouds, 417, 418; round η Argûs, 418, 419; remote systems, 419; invisible solar, 421; meteors falling from, 422.

Nebulous appearances of a comet, 364; extent of, matter surrounding a comet, 373; its variable brilliancy, 374; appearances round the sun, 412.

—— stars, 411, 412.

Needle, magnetized, effect of Voltaic electricity on a, 312, 313; suspended by means of electricity, 314; condition of its deviation by an electric current, 317.

Negative electricity defined, 282; mode of exciting, 283.

—— impressions in photography, 204.

Neptune, periodical variations in his orbit, 22; revolution of his satellite from east to west, 33; remoteness of, 54; anticipation of discovery, 61; orbit and motions of, determined, 62; his diameter, mean distance from the sun, 63; temperature of, 225; action of, on Halley’s comet, 363.

Neutral phosphate of soda, its crystals, 109.

New Mexico, monsoons occasioned by its deserts, 124.

Newton, Sir Isaac, steps of his argument for the universal influence of gravitation, 3; his discoveries of modes of attraction, 4; motions of bodies projected in space, ascertained by, 5; form of a fluid mass in rotation ascertained, 45; problem occupying astronomers since, 64; discrepancy between his theory of tides and observations, 96; compound nature of white light proved by, 159; his analysis of the solar spectrum disputed, 161; his theory of light disproved, 167; measurements of coloured rays, 172, 173; scale of colours, 174; decisive experiment disproving the theory of light, 202; remarks on the transmission of gravity, 355.

Niagara, the falls of, not independent of the influence of astronomy, 1.

Nickel, sulphate of, change in its crystals, when exposed to the sun, 107.

Niepcé, M., photographic pictures rendered permanent by, 204; discovery in photography suggested, 207; colours of images of the sun taken, 213; experiments by, on saturation of substances with light, 296.

Nimes, discovery of a telescopic planet at, 21.

Nitrogen, proportion of, in the atmosphere, 117; spectrum from, 303; iron volatilized by the Voltaic arc in, 304; unaffected by magnetism, 344.

Nobili, M., direction of electric currents ascertained by, 333.

Nodes, ascending and descending, of a planet defined, 9; movement of their lines in secular disturbances, 14; advance and recession of, 18; supposed recession of, on the equator of the solar system, 24; of the moon, period of their sidereal revolution, 37; secular inequality affecting, 38; influence of, on eclipses, 39; cause of their rapid motion, 55; points of rest on a vibrating string, 141; in the vibrations of an undulating column of air, 142; in vibrations of solids, 147.

Non-conductors of electricity, 284, 285.

Non-electrics, 285.

North Atlantic, the, winds in, 124.

—— Polar Ocean, tide in the, 94.

Norway, course of the tidal wave to, 94.

Notes in music, 142, 143.

Nubecula, Major and Minor, 417, 418.

Nucleus, of Halley’s comet, changes in its aspect, 364; disappearance of, in Encke’s, 369; division, in Biela’s, 369, 370; diaphanous, 373; solidity of, tested, 374; of a spiral nebula, 409.

Nuremburg, observations on a comet from, 370.

Nutations produced by the moon’s nearness to the earth, 7; in Jupiter’s equator, 29; in the planetary axes, 66; effect of, on the pole of the equator, longitudes and latitudes altered by, 81.

Nysa, nearness of its orbit to the earth, 21.

Oaks, range of, near the equator, 250.

Occultation, central, by Halley’s comet, 364; geographical position ascertained by, 384; prospective, by a sun of α Centauri, 400.

Occultations of stars, 42, 43.

Ocean, the, density and mean depth of, 51; mean density, compared with the earth’s, 77; its form in equilibrio, when revolving round an axis, 92; solar and lunar attraction disturbing its equilibrium, _ib._; inequalities in periodic motions, 93; motions of the tidal wave in 95; stability of its equilibrium, 100; circulation of currents in, _ib._; stratum of constant temperature in, 101; zones of, _ib._; decrease and increase of temperature with depth, 231; absorption and radiation of heat by, 242; electricity evolved from, 291.

Oceans of light and heat, processes producing, 225.

Ochotzk, the sea of, depression of the barometer observed in, 120.

October, 1832, position of Saturn’s rings in, 67.

Olbers, M., computations for a comet by, 367; period of his comet, 370; comet of 1811 observed by, 374.

Opaque bodies, mode in which heat is developed in, 227.

Ophiuchi 70, anomalies in the motions of, 400.

Ophiuchus, clusters of the Milky Way between the Shield and, 387; new star disappearing from, 393.

Optic axis, the, of crystals, 183; phenomena exhibited by transmission of a polarized ray along, 187, 188; affected by compression, 189.

Orbit, the, of the earth, attraction intensified by its diminished excentricity, 37; excentricity of, affecting temperature, 74, 75; crossed by comets, 368.

—— of the moon, force ruling, 4; its excentricity, 34; changes in, 35; its inclination to the plane of the ecliptic, 79.

—— of a nebula, 415.

—— of the solar system, 405, 406.

Orbits of comets, subject to variation, 361; examples, 361-363; prospective changes in, 369, 370; of Donati’s, 379; forces determining their forms, 382, 383.

—— of double stars, 396-400.

—— of planets, force regulating a planet’s velocity in, 8; measurement of their excentricity, 9; seven elements of, determining their position in space, 10; unequal movements in, 15; variation from elliptical to circular, 17; secular variations of, in inclination to the plane of the ecliptic, 18, 19; stable and unstable in form, 21, 22; influence of the ethereal medium on, 22; principle facilitating observations on secular inequalities, 23, 24; revolutions of Saturn compared with Jupiter, 25; periodic inequality increased by secular variations in their elements, 26; comets revolving in, 381, 382; cause of diversity in form of, 382.

Orbits of satellites, forms of Jupiter’s, 27; their inclinations, 28; inclinations of Saturn’s, 32; positions of Uranus’s, 33; forms of data in computing a planet’s place in the heavens, 59.

Orinoco, the cataracts of the, heard by day and by night, 135; area occupied by forests on, 243.

Orion, the Milky Way between Antinous and, 385, 386; position of, 390; variable star in, 393, 394; multiple system in, 395; nebula in, 408.

Oersted, Professor, discovery of, suggesting the theory of electro-magnetism, 312; science founding the reputation of, 316.