ing, 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 elec- tricity by rotation, 330; classifica- tion 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 sub- division, 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 tem- perature below the earth's surface calculated by, 230.
Marco Polo, atmospheric effects ob- served 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 be- tween Jupiter and, 20, 21; diame- ter of, 21; mean distance from the sun, ib. note; eclipse of Jupiter by, 42; parallax found by observing his oppositions, parallax of, 53; in-
ternal structure, 58; astronomical tables of, 63; climate of, 225; approach of the comet of 1770 to, 362; comets having their peri- helia 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 find- ing, 55, 56.
Mathematics, use of, in the study of astronomy, 2.
Matter, theory of its constitution, 102; hypotheses as to forces unit- ing its particles, 103, 104; coun- terbalancing action of elasticity and cohesion, 105; crystallization com- mon to all forms of, 109; indestruc- tibility of its particles, 110; com- position of unorganised bodies, sub- ject 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 dis- tances, 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 mag- netism, 344; density of, 356; pro- bable relations of, to gravity, ib.; experiment testing its magnetic pro- perties, 356, 357; functions of, 357; pervading the visible crea-
tion, 358; unsolved question touching, 365; a cause of accele- rated revolutions of comets, 366, 367; direction of its increase in density, 367.
• Medium occupying space, 424. Medusa tribes, the, phosphorescent brilliancy of, 295.
Megallanic clouds, the, 417, 418. Melloni, M., experiments of, in pho- tography, 214; his application of the principle of thermo-electricity, 333; experiments of, in transmis- sion of heat, 258-263; fixing the maximum of heat in the solar spec- trum, 264; in polarization of heat, 264-266; light separated from heat by, 265.
Melville Island, height of the ther- mometer in, in January, 247. Mercury, inclination of his orbit to the plane of the ecliptic, 21; eclipse of, 42; cause of his rotation un- known, 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 revolv- ing 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 mag- netic, 343. Meridians, size and form of the earth determined from, 46; measurement of arcs, 47; anomalies from local attraction, 48; result of the com- putations, 48, 49; permanent, of the moon, 69, 70.
-, magnetic, influencing the direc- tion 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 re- flected from, 193; plates, impres- sions on, from bodies in contact with, 220. Metals, expansion of, by heat, 271; propagation of heat in, 274; trans- mission of electricity by, 284; elec- tricity 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; pro- perties of, modifying electric suscep- tibility, 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; crowd- ing 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 phosphores- cent 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; ex- periments of, in expansions of crys- tals, 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 elec- tricity, 282; attraction, electricity developed by destruction of, 284.
structure affecting transmission of electricity, 303.
vortices, hypothesis of, account- ing for the absorption of light.
Molecules, material, attraction and repulsion of, 103; effect of elasti- city and cohesion on, 104-106; uniting to form crystals, 107-109; extreme minuteness of ultimate, 110; of ether, modes of their vi- bration in natural and polarized light, 193; in fluorescent light, 196, 197; images traced by the mutual action of, 219-222; ar- rangement of, connected with mag- netism, 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 de- crease 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 as- signed for acceleration of her mean motion, 36, 37; eclipses of, 39, 40; longitudes determined by ob- servations of, 42, 43; her mean horizontal parallax, 52; sources whence her mass may be deter- mined, 55, 56; her diameter, 56; rotation of, 68; librations, 69; mountains, 70; precession result- ing from her attraction, 79-81; influence of, producing tides, 91, 92, 96-98; period of her declina-
tions, 97; atmospheric equilibrium disturbed by her attraction, 121; cause of her apparent increased magnitude in the horizon, 158; photographic image of, 214; com- parative 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,
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 atmo- sphere 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 tem- perature, 241, 242; cause of éboulemens in, 271; tops of, fused by lightning, 293.
lunar, effect of solar rays pass- ing between, in eclipses, 41; in- fluence 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 sym- pathetic notes in, 2; regulated un- dulations 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 mo- tions 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; an- nular, 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 megallanic clouds, 417, 418; round Argus, 418, 419; remote systems, 419; invi- sible solar, 421; meteors falling from, 422.
Nebulous appearances of a comet,
364; extent of, matter surround- ing 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; sus- pended 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 satel- lite from east to west, 33; re- moteness of, 54; anticipation of discovery, 61; orbit and motions of, determined, 62; his diameter, mean distance from the sun, temperature of, 225; action of, on Halley's comet, 363.
Neutral phosphate of soda, its crys- tals, 109.
New Mexico, monsoons occasioned by its deserts, 124.
Newton, Sir Isaac, steps of his argu- ment for the universal influence of gravitation, 3; his discoveries of modes of attraction, 4; motions of bodies projected in space, ascer- tained 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 disprov- ing the theory of light, 202; re- marks 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.
Niepce, M., photographic pictures rendered permanent by, 204; dis- covery in photography suggested, 207; colours of images of the sun taken, 213; experiments by, on saturation of substances with light, 296.
Nismes, discovery of a telescopic planet at, 21.
Nitrogen, proportion of, in the at- mosphere, 117; spectrum from, 303; iron volatilized by the Vol- taic arc in, 304; unaffected by magnetism, 344.
Nobili, M., direction of electric cur-
rents 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 equa- tor of the solar system, 24; of the moon, period of their sidereal re-
NON-CONDUCTORS.
volution, 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 vi- brations of an undulating column of air, 142; in vibrations of solids, 147.
Non-conductors of electricity, 284,
Non-electrics, 285.
North Atlantic, the, winds in, 124,
Polar Ocean, tide in the, 94. Norway, course of the tidal wave to,
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; so- lidity 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 Ju- piter's equator, 29; in the planet- ary axes, 66; effect of, on the pole of the equator, longitudes and lati- tudes 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 a 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 attrac- tion 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 tempera- ture in, 101; zones of, ib.; de- crease and increase of temperature with depth, 231; absorption and radiation of heat by, 242; electri- city 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 mo- tions 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 transmis-
sion of a polarized ray along, 187, 188; affected by compression, 189. Orbit, the, of the earth, attraction intensified by its diminished ex- centricity, 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 the solar system, 405, 406. Orbits of comets, subject to variation,
361; examples, 361-363; pros- pective 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; measure- ment of their excentricity, 9; seven elements of, determining their po- sition in space, 10; unequal move- ments in, 15; variation from elliptical to circular, 17; secular variations of, in inclination to the
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