Part 56

Serpentarius, star in, vanishing, 392.

Shell-fish, their mode of clinging to rocks, 117.

Shield, the, clusters of the Milky Way between Ophiuchus and, 387.

Shooting stars, phenomena of, described, 421, 422; theories of, 423.

Siberia, Eastern, depression of the barometer observed in, 120.

Sidereal times, mean, periods of, 83; measurement of apparent, _ib._

Sigma Eridani, period of revolution in, 400.

Silesia, fulgorites from, 293.

Silver iodized, its sensitiveness to impressions, 221.

Sirius, the Egyptian year estimated from, 85; comet’s tail extending from the Hare to, 373; rank of, 384; comparative magnitude, 385; parallax, 389; cause of his irregular motion, 392; change in colour, 401; light, 402; extent of surface, 404.

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

——, Piazzi, heat of the moon felt by, 227.

Snow, cause of perpetual, on summits of alpine chains, 119; causes modifying the height of the line of perpetual, 241; protecting vegetation, 249; radiation of heat by, 257.

Soda, sulphate of, change of form in its crystals, 107; crystals of the neutral phosphate and the arseniate of, 109.

Soil, the, dependence of temperature on the nature of its products, 243.

Solar gravitation, 424, 425.

—— magnetism, its connexion with terrestrial, 344.

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

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

Soleil, M., crystals compressed by, 189.

Solids, conditions reducing molecular particles to, 104, 105; distinctive forms taken by matter in, 106; velocity of sound passing through, 135; change of shape in, accompanying ringing sound, 147; expansion of, by heat, 271.

Solstices, the, solar motion at, affecting the duration of time, 84; the year estimated from the winter, 85; periodical coincidence of the solar perigee and apogee with, 86, 87.

Sothaic period, the, of the Egyptians, 85.

Sound, medium conveying, 129; its propagation by undulations illustrated, 129, 130; conditions modifying the intensity of, musical notes, 131; experiments testing the compass of audible, 132, 133; media modifying the velocity of, 133-137; laws of its reflection from surfaces, 137, 138; undulations of, subject to the laws of interference, 138, 139; laws of the foundation of musical science, 140-143; reinforced by resonance of cavities, 150, 151; repeated vibrations required to produce, 178; different modes of action in undulations producing light and, 199, 200; identical nature of heat and, 280, 281; measuring velocity, 290, 291.

Sounding boards, intensifying musical vibrations, 149; action of, in musical instruments, 150.

South, Sir James, positions of stellar systems measured by, 396.

South pole, the, excess of cold at, 241.

—— Sea islands, height of tides at, 98.

Southern Ocean, rise of the tidal wave in, 93; velocity of the wave, 94.

Spain, meteoric showers off the coast of, 421.

Specific heat defined, 275.

Spectra of gases and flames, their characteristic peculiarities, 163, 164; three superposed, of the pure white sunbeam, 222.

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

—— of an electric spark, 289.

—— of the Voltaic arc, 303.

Spheres, mode of attraction in hollow and solid, 4; planets partaking the nature of, 7; impulses regulating rotations, _ib._; conditions procuring the figure of, 44; formula finding the density, 56; force giving the form of, 106; power of retaining electricity, 288.

Spherical form, the result of cohesion, 106.

Spheroids, influencing attraction differently from spheres, 4; force disturbing attraction in, 27; compression of the terrestrial and of Jupiter’s, computed, 38, 39; of elliptical strata, quantities invariable in, 46; of the sun, 65; effect produced by the attraction of an external body on, 79; power of retaining electricity, 288.

Spiral nebula, 409, 410.

Spots on the sun’s surface, periods of their vicissitudes, 224; amount of heat varying with, 225.

Spring tides, 96-99.

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

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

Stars, fixed, the, the solar system probably not independent of, 24; velocity of light deduced from aberration of, 31; vast distances of, 54; precession affecting their longitudes, 80; computations of their positions furnishing historical data, 88, 89; made visible by refraction, 154; peculiar law of light demonstrated by the aberration of, 202; magnitude of the solar system seen from, 226; numbers, classification of, 384; positions, 385; the Milky Way, 385-387; parallaxes and distances of, 387-389; variable, 390-395; missing, 395; systems of multiple, classified, _ib._; binary, 395-406 (_see_ Double stars); nebulous, 406-419 (_see_ Nebulæ); seemingly innumerable, 420; meteors, 420-423.

Static electricity, 282: _see_ Electricity.

Steam, formation of, 269; force converting liquids into, 277; measure of its elasticity, 278; question of its being superseded by electricity, 328.

Steel, paramagnetism induced in, 336; conditions of magnetic power remaining permanently in, 337, 338; its elasticity affected by magnetism, 352.

Stephenson, George, quotation from, 279-280.

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

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

Strata of the earth, position and comparative density of, 77.

Stratifications, experiments showing, in electric light, 306, 307.

Struve, M., measurement by, 48; his observations on Saturn’s rings, 68; occultation by a comet observed by, 364; comet’s nucleus described, _ib._; distance of a fixed star measured by, 388, 389; catalogue of double stars, 396; remarks on colour and light of double stars, 401; sun’s motion proved by, 405.

Stutgardt, natural hot springs used in manufactories near, 231.

Submarine telegraph, 325-327.

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

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

—— of soda, its crystals, 107.

—— of zinc, experiment on its crystals, 108.

Sulphuretted hydrogen gas, its constituent parts, 111.

Sumbawa, volcanic eruption of, 233.

Summer, mean temperature of, varying in the same latitude, 246, 247; atmospheric electricity in, 291.

Sun, the, law regulating his attraction of heavenly bodies, 5; effect of his attraction on planetary orbits, mean distance of planets from, 8; importance of his magnitude in the solar system, 12; disturbances in the relative positions of planets and, 14; force modifying his intensity of attraction, 16; resistance offered by, to the power of disturbing forces, 20; periods of conjunctions of Jupiter, Saturn, and, 25; influence of, on lunar motions, 34, 35; action of the planets reflected by, 37; eclipses of, 40, 41; supposed constitution of, 41; his atmosphere, 42; mode of finding his parallax, 52, 53; mean distance from the earth, 53; mass of, 55; diameter, 56; comparative density, attractive force, 56, 57; astronomical tables of, 63; deductions from his rotation about an axis, period of, 65; attraction of, producing a precession of the equinoxes, 79, 81; returns of, a measure of time, 83-85; divisions of time, dependent on revolutions of the major axis of his orbit, 86, 87; action on tides, 92, 97; disturbing the equilibrium of the atmosphere, 121; dry and rainy seasons regulated by, 123; cause of decreased light and heat in horizontal rays, 157, 158; distance of, falsely estimated, 158; light polarized by, 195; indications of an absorptive atmosphere surrounding, 212, 213; his diameter, 224; appearance of, through his atmospheres, _ib._; variations in heat and light emitted from, 225, 226; amount of heat annually received by the earth from, 238; effect of his brilliancy on the heat emitted by, 259; his position affecting variations in the magnetic elements, 343, 344; connexion between periodic variation in his spots and in the magnetic elements, 344; vast sweep of his gravitating force, 365; increased attraction of, for comets, 372; gulfs separating stars from, 390; possibility of change in his lustre, 394; spot on, measured by Sir John Herschel, 394, 395; proportion of his light to the moon’s, 404; rate and orbit of motion with his system, 405, 406; a nebulous star, 412; meteoric nebula revolving round, 422; gravitating force of, 424, 425.

Sunbeams, resolved into their component colours, 159-162; law prevailing in the phenomena of, 198; light a distinct property of, 214; resolved into three spectra, 222; undulations constituting, 223; their influence on vegetation, 249.

Swan, the, vanishing star in, 393.

Switzerland, meteors falling in, 421.

Syene, arc of the meridian measured between Alexandria and, 49.

Sykes, Colonel, extensive range of cultivation of wheat observed by, 250.

Sympathetic vibrations in musical instruments, 147-149.

Syren, the, an instrument ascertaining the number of musical pulsations in a second, 143.

Syzygies, tides increased in the, 96.

Table-lands, high, influence of, on the atmosphere, 241.

Tahiti, transit of Venus observed at, 53.

Tail of comets, sudden development of, 372; forces producing, 375; unequal illumination of, 375, 376; change in position of, 376; divided, _ib._; constitution of, 377.

Talbot, Fox, his inventions in photography, 204.

Tangent, a, to planetary orbits, planets impelled in the direction of, 8; force, disturbing, in the direction of, 14, 15; deflection from, a measurement of centrifugal force, 49.

Tangential force, occasioning secular inequalities, 14; effects produced by, 15; producing the variation of the moon, 35; force acting on the sea, 100.

—— velocity, effects produced by modifications of, 16; undiminished by the ethereal medium, 22.

Telegraph, the electric, discovery leading to the invention of, 323, 324; the Atlantic, 325; principles of its construction, 326, 327; date of its completion, 327.

Telegraphs, land, principle of their construction, 328.

Telescope, the achromatic, principle of its construction, 164.

——, the differential, differences in illumination determined by, 227.

——, Lord Rosse’s, nebulæ resolved by, 407, 415.

Telescopium, comet traversing the constellation of, 379; nebula in, 414.

Temperature, a decrease in, affecting the earth’s rotation, 72; excentricity of the terrestrial orbit, a cause of decreasing, 73; law equalising, 74; geological changes affecting, 75.

——, varying in the terrestrial atmosphere, zone of constant, 119; affecting atmospheric undulations, 121; modifying the velocity of sound, 134; chemical action of light affected by, 218-222; of the ethereal medium, 227, 228; underground stratum of constant, 228; rate of increase in, below the earth’s crust, 228, 231; of the ocean, 231; mode of finding annual average, 239; causes of disturbance in regular variation of, 240-245; variations in the same latitude, 246, 247; influence of, on vegetation, 248; affecting transmission of heat, 259, 260; of solid bodies, caused by absorption of rays, 268; affecting the length of the pendulum, 272; causes of perpetual variations in, 274; transmission of electricity affected by, 284; affecting magnetism, 352.

Teneriffe, the Peak of, prevailing winds on, 124; lunar heat on, 227; zones of vegetation, 250; character of its flora, 252.

Terrestrial globe, the, a magnet, 336.

—— magnetism, 341-343; the three elements and their variations, 343, 344; storms, period of their variation, 344; its connexion with solar magnetism, _ib._; effect of atmospheric magnetism on, 345; probable cause of, 346; effect of planetary magnetism on, 346, 347.

—— meridian, a, defined, 46.

Tessular system of crystallization, 108.

Texas, monsoons occasioned by its deserts, 124.

Thames, the, period occupied by the tidal wave in reaching, 94.

Thaw, cause of the sensible chilliness of, 276.

Theory of probabilities, use of, in determining astronomical data, 60.

Thermo-electric currents, discovery of, 332; phenomena exhibited by, 333; principle of, applied to measuring heat, 333, 334.

Thermography, examples of, 219-221.

Thermometer, the, principles applied to the construction of, 113; consulted in determining mountain heights, 119, 120; refraction varying with, 154; heat measured by motion in, 274.

Thermomultiplier, use of, in experiments, 264; principle of its construction, 333, 334.

Theta Orionis, the multiple system of, 395.

Thomas, St., the island of, hurricane with pauses at, 127.

Thomson, W., Professor, experiments of, in freezing water, 271; dynamical theory of heat maintained by, 275 _note_; his calculation of the force exerted in vibrations of light, 279; investigation into the relations of light and magnetism, 320; density of the ethereal medium computed by, 356; magnetic property of the ethereal medium pleaded for, 357.

Thunder, theory of prolonged peals of, 138.

Tibet, wheat ripening in, 250.

Tidal wave, theory of, 92; its birthplace, 93; course of, 93, 94; velocity, 94; effect of depth on its motion, 95.

Tides, calculation from the moon’s action on, 55; theory of forces producing, 91, 92; circumstances occasioning irregularities, 93; rising, progress of, 93, 94; three kinds of oscillations in, 95, 96; variations in, from lunar and solar influence, 96-98; effect of interference of waves on, 99; the sea’s equilibrium underanged by, 100.

——, lunar and diurnal, of the terrestrial atmosphere, 121; examples of sympathetic undulation, 148.

Time, a measure of motion, 58; a measure of angular motion, 83; difference between mean and apparent solar, 84; mean equinoctial, mode of computing its object, 86; estimation of, corrected by means of laws of unequal expansion, 272.

Timocharis, comparison of his observations with Hipparchus, 80.

Tomboro, submerged in a volcanic eruption, 233.

Toronto, observations on magnetic storms at, 346.

Torpedo, the, electrical action of, 310, 311.

Torricellian vacuum, experiment on the electric discharge in the, 306; lines of magnetic force passing through, 344.

Toucan, comet approaching the constellation of, 379; a nebula in, 414.

Toucani, 47; globular nebulous cluster, 414.

Tourmaline, brown, light polarized by prisms of, 180; property qualifying it to analyze polarized light, 182; coloured images produced by, 186, 187; changed by compression, 189; heat polarized by, 265; electricity communicated to, 284.

Trade winds, friction of, not affecting the earth’s velocity, 72; action on the general motion of the sea, 100; system of, accounting for atmospheric anomalies, 120; theory of their origin, phenomena connected with, 122, 123; becoming monsoons, 124.

Transits of Venus, 52, 53.

——, two consecutive, of any star, a measure of time, 83.

Transmission of radiant heat, 258, 262; of electricity, 284, 285; of voltaic electricity, 298; molecular structure affecting, 303; method of, determining the influence of electric currents, 317; of gravity, an unsolved question, 355; probable agent, 356; medium of, in space, 424.

Transparent bodies, temperature of, unaffected by the sun’s rays, 227.

Trees, number of species of forest, found in America and Europe, 252.

Tribes, apparently distinct, of the human race, 255.

Triple stars, 395; periods of revolution in, 400.

Tropical year, change in its length, 80; period of, 83; difficulty of adjusting its estimation, 85.

—— revolution of the major axis of the solar ellipse, its period, 86.

—— vegetation, the luxuriance of, 248.

Tuileries, clock in the, showing decimal time, 84.

Twilight, caused by refraction, 154; effect of reflection, 158.

Tyndall, Professor, his experiments proving diamagnetic polarity, 348; on magnetic action in crystals, 349.

Undulations, theory of, 99; of the atmosphere, 121, 122; of the waves of sound, 129, 130; intervals produced by interference, 139; giving musical notes, 142, 143; sympathetic, 147, 149; of the luminous ether, 169, 170; in refraction and reflection, 177; producing fluorescence, 197; different, in light and sound, 199, 200; constituting a sunbeam, 223; heat propagated by, 267; of light, evolution of latent force in extinguished, 279, 280; of natural forces identical, 281.

Undulatory theory of light, 168-170; law of motion affecting, 176, 177; phenomena proving, 198; objection, from the different action of light and sound, refuted, 199; proving the existence of the ethereal medium, 358; acceleration in comet’s motion proving, 367.

—— theory, experiments determining in favour of, 200, 201; final and decisive experiment, 202; of heat, 267.

Unison, note in, 142.

United States, astronomical observations made in, 371, 373.

Uranium, phosphorescent property of, 296; peculiar luminous properties of, 296.

Uranus, effect of reciprocal attraction between Neptune and, 22; periods of the revolutions of his satellites, 33; distance from the sun, 54; astronomical tables of, 60; discovery suggested by his perturbations, 61; observations on, leading to Neptune’s discovery, 62; sun’s influence in, 225; action of, on Halley’s comet, 363; appearance of the sun to, 380, 381; comets in his orbit, 381, 382.

Ursa Major, periodic time of a double star in, 398; nebulous region of, 417.

Utah, deserts of, causing monsoons, 124.

Vacuum produced by shell-fish, 117; existing in the air, 118.

Valz, M., telescopic planet discovered by, 21; comet observed by, 358; observations on a comet’s approach to the sun, 364; cause assigned by, for contraction in diameter of comets, 377, 378.

Vapour, formation and dispersion of, 269, 270; force developing, 277.

Variable stars, periodic fluctuation of lustre in, 390, 391; new, appearing and vanishing, 392, 394; missing, 395.

Variables, region of the, 122.

Vegetation, effect of, in lowering temperature, 243; the two requisites for, 248; strength and vitality of, 249; chemical action of light influencing, _ib._; laws of its distribution, 249-252; distribution of marine, 252, 253; theories of specific diversity of original distribution of, 253, 254.

Venus, zone of instability between the sun and, 21; perturbation in the mean motion of the earth and, 26; eclipsing Mercury, 42; transits of, parallaxes calculated from, 52, 53; astronomical tables of, 63; climate, 226.

Vernal equinox, planetary motions estimated from, 9.

Vesta, astronomical tables of, 63; no atmosphere surrounding, 226.

Vesuvius, revived volcanic action of, 234.

Vibrating plates used in experiments on musical sound, 144, 147.

Vibrations of the air producing sound, 129; in music, 131; number made by the human voice in a second, 132.

—— of the ether in natural and polarized light, 193; in fluorescence of light, 196; plane of, in polarized light, 223.

Vico, Padre de, comet discovered by, 370.

Vienna, observations on comets from, 370.

Vietch, James, comet with luminous rings discovered by, 374, 375.

Vincent, St., revival of an extinct volcano in, 234.

Virginia, daguerreotyped spectral image obtained in, 213.

Virgo, planetary conjunction between Libra and, 42; variable star in, 392; star vanished from, 395; nebulous zone passing, 416, 417.

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

Volcanic regions of the globe, 232; annual number of eruptions, 233; celebrated eruptions, _ib._; earthquakes caused by, 234; supposed causes of action, 235; Sir John Herschel’s theory, 235-237.

Volta, Professor, electricity rendered manageable by, 297; the world’s debt to, 328.

Voltaic electricity, first suggestions of, 297; theory of the transmission of, 298; construction of the battery, 298, 299; theory of its production, 300; characteristic properties, 300, 301; action of, generating heat and light, 301-303; arc, experiments, 303-305; the, discharge oxidizing silver, 305, 306; stratified light, 306, 307; chemical decomposition effected by agency of, 307, 308; crystallization, 308; an agent in the fine arts, 309; conductors of, _ib._; relations of heat and, 310; fish producing effects of, 310, 311; science suggested by its influence on a magnetized needle, 312; rotation effected by, 313, 314; inducing magnetism, 314, 315; distinction between static electricity and, 317; unvarying dual force of, 334.

Voltaic pile, the, invention of, 297; perfected, 298-300.

Vortices, molecular, theory of, 104.

Vosges mountains, temperature of mines in the, 228.

Vulpecula, nebula in, 409.

Wardhus, transit of Venus observed at, 53.

Watches, irregular action of, corrected by the laws of unequal expansion, 272.

Water, constituent parts of, 111; boiling point of, an estimate of mountain heights, 120; as a medium for sound, 135; light polarized circularly by, 194; experiment deciding the velocity of light in, 202; law of expansion of, 271; process of congelation, 276; boiling points of, 277; decomposed by electric agency, 307; as an electric conductor, 309; rotating by electricity, 314.

Waterspouts, origin and cause of, 128.

Waterstone, Mr., magnetic property of the ethereal medium maintained by, 357.

Waves neutralized by interference, 99.

——, atmospheric, over local districts, periods, dimensions of, 121, 122.

—— of sound, 131; furnishing an illustration of reflections of sound and light, 137; interference of, producing calm, 139.

Wedgwood, Dr., attempts of, to trace objects by means of light, 203, 204.

Week, the, of seven days, the most ancient and universal division of time, 85.

Wells, increase of temperature in, 230, 231.

Welsh, Mr., observations made by, in a balloon ascent, 119.

West Indies, the, cause of hurricanes in, 126.