On the Connexion of the Physical Sciences

by Mary Somerville

[Plate 9] represents some of the same objects as seen by Lord Rosse.

1. Nebula in the girdle of Andromeda.

2. The circular nebula of Lyra.

3. The dumb-bell nebula in Vulpicula.

The spiral nebulæ of 51 Messier, as seen by Lord Rosse, 1 in [plate 10], represents fig. 4 of [plate 8]; and fig. 2 in the same plate is part of the great nebula in Orion, for the whole has never been seen, on account of extreme remoteness.

Note 237, pp. [32], [427]. The motion of the earth is visibly proved by M. Foucault’s experiments. If a pendulum be left to oscillate quite freely, the forces producing the oscillations being in the vertical plane, there is no cause that can produce an absolute change in its position with regard to space; but the motion of the earth changes the position of a spectator with respect to the vertical plane, and he refers his own motion to it, which seems gradually to turn away from its position, precisely as a person in a boat refers his own motion to that of the land, and thus the motion of the earth is truly and visibly proved.

INDEX.

• Aberdeen, high water at, [94].
• Absorption, influence of, on temperature, [239];
  • difference of sea and land in power of, [242];
  • gradually decreasing, in transmission of radiant heat, [259];
  • of radiant heat, varying with substances, [268];
  • a transfer of force, [275], [276].
• Acceleration of the moon’s mean motion, [37], [38].
• Adams, Mr., perturbation in Uranus’s motion computed by, [22];
  • discovery of Neptune, [62].
• Aërolites, theory of, [420], [423].
• Africa, tidal wave passing, [94];
  • mean annual equatorial temperature in, [245];
  • indigenous productions of, [249], [250].
• Air, comparative velocity of light in water and, [202].
  • See Atmosphere.
• Airy, Professor, periodic inequality in the solar system worked out by, [26];
  • phenomenon observed by, during an eclipse, [41];
  • mass of Jupiter ascertained by, [55];
  • experiments ascertaining its density, [57];
  • astronomical tables improved by, [63];
  • discoveries in polarization of light, [192], [193].
• Aldebaran, an optically double star, [401].
• Aleutian Islands, the, vegetation of, [252].
• Alexandria, arc of the meridian measured between Syene and, [49].
• Algæ, districts of distinct species of, [252];
  • banks of, in the Atlantic, [253].
• Algol, fluctuations in lustre of, [390], [391].
• Alhazen, effects of refraction observed by, [155].
• Alkalies, resolved into metallic oxides, [307].
• Alpha Antaris, “Coal Sacks” between α Centauri and, [386].
• Alpha Aquilæ, an optically double star, [401].
• —— Centauri, the parallax of, [54];
  • its rank, [384];
  • the Milky Way near, [386];
  • parallax, as determined by Henderson and Maclear, [387];
  • distance from the sun, [388];
  • orbit and mass of, [399], [400];
  • colour, [401];
  • amount of light emitted by, [404];
  • rate of its proper motion, [404], [405];
  • globular nebulous cluster, [414].
• —— Crucis, zone of stars passing through, [385];
  • zone between η Argûs and, [390];
  • nebulous cluster round, [415].
• —— Lyræ, the polar star of the northern hemisphere, [82];
  • parallax of, [388];
  • distance from the sun, [389];
  • an optically double star, [400];
  • amount of light emitted by, [404].
• —— Orionis, a variable star, [393], [394].
• Alum, experiments on the crystallization of, [106], [107];
  • heat transmitted through, [261], [262].
• Amazons, the river of, distance from its mouth where tides are perceptible, [98];
  • area occupied by forests on, [243].
• America, course of the tidal wave along its coasts, [93], [94];
  • mean annual equatorial temperature in, [245];
  • separation of isothermal lines in high latitudes, ib.;
  • number of known species of plants indigenous in, [249];
  • number of species of trees, [252];
  • shooting stars over the continent of, [421].
• ——, South, area of country raised by an earthquake in, [234].
• Ampère, M., his discovery in electricity, [316];
  • theory of magnetism, [317], [318];
  • experiment testing his theory, [319], [320].
• Analysis, boundless dominion of, [427], [428].
• Andes, the, proportion of, to the earth’s mass, [6];
  • increasing rarity of the air experienced in ascending, [118].
• Andromeda, nebula in, [413];
  • nebulous region of, [417].
• Angström, the electric spark defined by, [303].
• Animals, specific diversity of, laws regulating their distribution, [254], [255].
• Annual equation, the, of the moon, [35], [36].
• —— variations in mean values of the magnetic elements, [343].
• Annular nebulæ, [409];
  • in the northern hemisphere, [410], [411].
• Antarctic Ocean, tidal wave rising in [93];
  • period of its passage to the Thames, [94];
  • depth of the stratum of constant temperature in, [101];
  • depression of the barometer observed in, [120].
• Antilles Islands, hurricanes beginning at, [126].
• Antinori, Cav., experiments of, in electricity, [333].
• Antinous, comet observed in the constellation of, [372];
  • the Milky Way between Orion and, [386].
• Antithesis, the general character of magnetism, [339].
• Aphelion of a planet’s path defined, [16].
• Apogee, solar, its coincidence with the solstices, [86], [87].
• April, 1833, disappearance of Saturn’s rings, [67];
  • apparent and mean time coinciding in, [84].
• Apsides of an axis defined, [9];
  • direct, variable motion of, [14];
  • cause of their advance, or recession, [16].
• Apures, the mission of the, Humboldt’s observations on sound at, [135].
• Aqueous vapour, proportion of, in the atmosphere, [117].
• Ara, nebula in, [414].
• Arabian Gulf, the, monsoons blowing over, [124].
• Arabs, the, their observations on planetary irregularities, [26];
  • lunar eclipses observed by, [38];
  • their division of time, [85];
  • the pendulum used as a measure of time by, [90].
• Arago, François, experiment by, in proof of the undulatory theory of light, [200];
  • decisive experiment suggested by, [202];
  • observations in photography, [213];
  • observations on the moon’s atmosphere, [226];
  • increase of temperature below the earth’s surface calculated by, [230];
  • slow communication of temperature from the earth, observed, [244];
  • source of magnetism discovered, [330];
  • theory of his magnetic experiments, [332];
  • divergent flames of a comet described by, [364];
  • his treatise on comets, [368];
  • nature of comet’s light determined by, [380], [381];
  • numbers of comets computed, [381], [382];
  • remark of, on fixed stars, [405].
• Arc, the Voltaic, [303-305].
• Arcet, M. d’, vibration of fibres of the retina according to, [178].
• Archer, Scott, stimulus given to photography by, [207].
• Arcs of the meridian, mode of measuring, [47].
• Arctic Sea, depth of the zone of constant temperature, [101].
• —— regions, vegetation found in, [249].
• Arcturus, comet bearing comparison with, [379];
  • rank of, [384].
• Areas, described by the radii vectores of planets, a test of disturbing forces, [10];
  • unequable description of, [15].
• Argelander, M., period of a comet calculated by, [370];
  • his mode of estimating distance of fixed stars, [389];
  • periods of fluctuation in stars computed by, [390], [391];
  • sun’s motion proved, [405].
• Argentine preparations in photography, chemical energy varying with, [207], [208];
  • changes effected by washing with alkalies, [210], [211].
• Argo, variable star in, [393].
• Aries, season of the sun’s entrance into, in Hipparchus’ age, [80].
• Arseniate of soda, its crystals, [109].
• Artesian wells, mode of sinking, origin of the name, [230].
• Asia, indigenous productions of, [249].
• Assyrians, the, division of time by, [85].
• Astronomers, fruits of their labours, [3];
  • question still to be resolved by, [24];
  • terrestrial orbit differently measured by, [36].
• Astronomical distances, method of measuring, [43];
  • tables, method of forming, [58-64].
• Astronomy, its rank in the physical sciences, an important office of, [1];
  • studies necessary to the study of, [2];
  • the key to divers problems in physical science, [3];
  • the two greatest discoveries in, [23];
  • the three departments of, [58];
  • standards for measurement afforded by, [83];
  • application of, to chronology, [87-89];
  • furnishing standards of weights and measures, [89], [90];
  • atmospheric effects connecting the laws of molecular attraction with, [102];
  • progress lately made by, [419], [420].
• Atalanta, diameter of, [56].
• Atlantic Ocean, direction of tidal waves in, [93];
  • conditions modifying tides, [94];
  • depth of, [96];
  • currents, [100];
  • origin of hurricanes, [126];
  • superficial temperature of, [244];
  • distinct vegetation of the polar basin, [252];
  • beds of algæ in, [253];
  • meteors falling in, [421].
• —— telegraph, [325], [326];
  • terrestrial magnetism disturbing, [346].
• Atmosphere of nebulous stars, [411], [412].
• —— of planets, [226], [227].
• —— of the sun, its constitution, [42];
  • indications of an absorptive surrounding the luminous, [213];
  • the true, [224].
• —— terrestrial, solar rays bent by, in lunar eclipses, [40];
  • influence of, in solar eclipses, [41];
  • its analysis, pressure on the surface of the globe, [117];
  • form of, gradual decrease in density of its strata, [117], [118];
  • influence of temperature on its density, [119];
  • mean pressure of, variable, [120];
  • the medium conveying sound, [129];
  • sympathetic vibrations transmitted by, [147], [148];
  • its action on light, falsifying vision, [153];
  • phenomena produced by accidental
  • changes in its strata, [155-156];
  • effects of increased density in the stratum in the horizon, [157], [158];
  • lunar heat absorbed by, [227];
  • cause of the cooler air in higher regions of, [240], [241];
  • sun’s heat modified by, [244];
  • action of electricity in, [284];
  • transmission of electricity by induction, [286];
  • periodical variations of electricity in, [291];
  • accidental developments of electricity, [291], [292];
  • cause of variations in its magnetism, [344], [345];
  • nebulous bodies made visible by, [421-423].
• Atmospheric air, extreme elasticity of, [105].
• —— pressure, effect of, on electricity, [288].
• Atomic constitution determining crystalline forms, [109].
• Atoms, qualities of, determining the nature of substances, [110];
  • differences in weight of, [111].
• Attraction, modes of, in spheres, in the celestial bodies, [4];
  • determining the forms of planets, [6];
  • determining the motions of planets, [7];
  • solar, compelling the elliptical revolutions of planets, [8];
  • mutual, of planets, complicating their motions, [10];
  • interference of, disturbing the motions of heavenly bodies, [11];
  • disturbances from the operation of reciprocal, [13];
  • disturbances from inequality of, [14];
  • of satellites to primaries, little disturbed, [26];
  • disturbing force of, in spheroids, [27];
  • its effects on Jupiter’s satellites, [28];
  • sun’s, of the moon, [34];
  • principle modifying the earth’s, [37];
  • local, affecting the plumb-line, [48];
  • comparative force of the sun’s, [57];
  • of an external body affecting a spheroid, [79];
  • producing tides, [91], [92];
  • of particles of matter, [103];
  • capillary, [113];
  • producing annual atmospheric undulations, [121];
  • the lunar atmosphere affected by, [226];
  • expansive force of heat overcoming, [271];
  • of electricities, [283];
  • destruction of, producing electricity, [284];
  • laws of electrical, [286-288];
  • modes of, in static and in voltaic electricity, [317];
  • action of planetary, on comet’s orbits, [361-363];
  • range of solar, [365].
• Aurora, the, affecting the compass, [312].
• Australia, evidence of deserts in the interior of, [124];
  • species of plants common to Europe and, [251].
• Auvergne, temperature of hot springs in, [231].
• Axes, change in form of masses revolving round, [6].
• ——, major, length of, in orbits, invariable, [20];
  • of the orbits of Jupiter’s satellites, cause of the direct motion observed in, [28];
  • position of, in the solar system, [65];
  • a nutation in planetary, [66];
  • of the moon, [68], [69];
  • mechanical law affecting, [76].
• ——, optic, of crystals, [183].
• Axis, greater, of the earth’s orbit, period of its revolution, [38];
  • period of the earth’s revolution, [58];
  • excess of Jupiter’s equatorial over his polar, [66];
  • of rotation, proof of its being invariable, [76], [77].
• ——, major, of a planet’s orbit, distance from the sun measured by, [8];
  • designation of its extremities, [9];
  • length of, determining the form of the orbit, [10];
  • periods of its revolutions, [17];
  • length of, not permanently changed, [20];
  • Jupiter’s periodically diminished, Saturn’s increased, [26];
  • of the solar ellipse, period of its revolution, [86].
• ——, magnecrystallic, [349].
• Azores, the, icebergs reaching, [100].
• Babbage, Charles, his theory of volcanic action, [235-237];
  • quotation from, on the nature of force, [353].
• Babinet, M., his theory of dark lines observed in the solar spectrum, [163];
  • comet’s light computed by, [359].
• Babylon, eclipse observed at, [36].
• Bacon, Francis, anticipation of discovery by, [32].
• Baily, Mr., compression of the terrestrial spheroid calculated by, [50];
  • density of the earth determined, [57];
  • fictitious antiquity ascribed to Indian astronomical observations, [88].
• Bali, volcanic eruption in, [233].
• Balloon, rarity of the air felt in a, [118];
  • observations made from, [119].
• Baltic, the, a tideless sea, [98];
  • decreased atmospheric pressure on the shores of, [120].
• Barlow, Mr., observations supporting his theory of electric currents, [346].
• Barometer, the, principles of cohesion and attraction applied to the construction of, [113];
  • density of the atmosphere measured by, [117];
  • mean heights of, varying with atmospheric densities, [118];
  • mountain heights measured by, [119], [120];
  • atmospheric phenomena affecting, [120];
  • used to trace the course of atmospheric waves, [121];
  • cause of sudden fall in, before hurricanes, [127];
  • refraction varying with, [154].
• Barrow, Cape, observations on magnetic storms at, [345], [346].
• Battery, voltaic, construction of, [298], [299];
  • Professor Daniell’s improvements, [299], [300];
  • action of, charged with water, [300];
  • constant flow of electricity obtained by means of, [312].
• ——, magnetic, constructed by Dr. Faraday, [324], [325];
  • Mr. Henley’s magneto-electric, [325];
  • Atlantic telegraph, [326];
  • structure of, for land telegraphs, [328];
  • relation of heat to power of, [329];
  • thermo-electric, [333].
• Batsha, port of, tides neutralised in, [99].
• Bayle, comparative density of the atmosphere in interplanetary space according to his law, [356].
• Bear, Little, the, the polar star in, [82].
• Becquerel, M. E., unexplained photographic phenomenon observed by, [213];
  • phosphorescent property in the solar spectrum discovered, [216];
  • cause of phosphorescence, [217];
  • electricity excited by pressure, [283];
  • light attributed to electricity by, [284];
  • cause of phosphorescence investigated, [296];
  • instrument comparing intensities of electricities invented, [300];
  • crystals formed by agency of electricity, [308];
  • thermo-electric battery constructed by, [333];
  • effect of atmospheric on terrestrial magnetism estimated, [345].
• Beehive, the, a nebulous star, [415].
• Berard, M., experiments of, in polarizing heat, [264].
• Berlin, line of coincidence in temperature passing through, [238].
• Berne, increasing temperature of a deserted mine in, [230].
• Berre, Dr., photographic pictures perfected by, [205].
• Bessel, M., his calculations from measurements of arcs of the meridian, [48];
  • calculation of the sun’s mean apparent diameter, [56];
  • his computation of the mass of Saturn’s ring, [68];
  • diminished obliquity of the ecliptic observed by, [81];
  • parallax calculated, [389];
  • his theory of Sirius’s irregular motions, [392];
  • catalogue of double stars, [396];
  • mass of [61] Cygni found by, [404].
• Beta Lyræ, a variable star, [391];
  • nebula between γ Lyræ and, [410].
• Benzenberg, M., velocities of falling stars computed by, [423].
• 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 [177]0, [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 [168]2, [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 [177]0, [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].
• 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].
• Oscillations, wide-spreading, produced by gravitation, [2];
  • mechanical principle affecting small, [11];
  • of the sines and cosines of circular arcs, [20];
  • invariable plane whence they may be estimated, [24];
  • of the pendulum retarded, [32];
  • of the pendulum, experiments founded on, [50], [51];
  • experiments testing the earth’s density, [57];
  • a measure of time, [83];
  • produced by tides, [95], [96];
  • instruments measuring atmospheric, [113];
  • barometer affected by periodic atmospheric, [120], [122];
  • of ears of corn, [129], [130];
  • producing musical notes, [140-142];
  • instances of forced sympathetic, [148];
  • causing vicissitudes in climates, [247];
  • of the pendulum, disturbed by effects of temperature, [272];
  • measuring variation of electrical intensity, [287].
• Otto, M., motions of the heavenly bodies observed by, [405].
• Oxidation of metals, electricity developed by, [298];
  • by the Voltaic discharge on polished silver, [305].
• Oxides decomposed by electricity, [307];
  • alkalies resolved into metallic, [307].
• Oxygen, in crystals, [109];
  • proportion of, in water and carbonic oxide, [111];
  • in the atmosphere, [117];
  • chemical combination with, evolving light and heat, [270];
  • action of electricity on, [284];
  • electricity afforded by combination of metals with, [298];
  • spectrum from, [303];
  • separated from water by electricity, [307];
  • paramagnetic, [344].
• Ozone, produced by electricity, [284].
• Pacific Ocean, mean depth of, [77];
  • course of tidal waves down, [93];
  • mean depth of, [96];
  • currents, [100].
• Paderborn, fulgorites from, [293].
• Pallas, inclination of its orbit to the ecliptic, [10];
  • diameter of, [21];
  • astronomical tables, [63];
  • ellipticity of its orbit compared with the terrestrial, [74];
  • height of its atmosphere, [226];
  • comet revolving between the orbits of Mercury and, [367].
• Pan’s pipes, vibrations in the air passing over, [142].
• Parabolic motion, ratio of forces procuring, [382].
• Parallax of the sun, circumstance favourable to its correction, [21].
• —— of an object defined, [43].
• ——, definition, mode of ascertaining, [52];
  • distances computed from, [52-54];
  • calculation from the moon’s horizontal, [55].
• —— of fixed stars, [387-390].
• —— of meteors, [421], [422].
• Paramagnetic substances, [335], [336].
• Paramagnetism defined, [335];
  • substances it is resident in, [336];
  • modes of imparting, ib.;
  • a dual power, ib.;
  • imparted by induction, [337];
  • law of its intensity, [338];
  • a property of oxygen, [344];
  • in antithesis to diamagnetism, [347];
  • neutral substances obtained by combinations of diamagnetism and, ib.;
  • Dr. Tyndall’s experiments on polarity of, [348];
  • dependent on arrangement of molecules, [350], [351];
  • affected by compression, [351];
  • truth establishing its identity with diamagnetism, [356], [357].
• Parathermic rays, analyzed by Sir John Herschel, [217-219].
• Paris, variation in length of the pendulum at, [51];
  • mean annual temperature, [228];
  • temperature of an Artesian well in, [230].
• Paths of comets, [359], [360];
  • secrets disclosed by their excentricities, [365].
• Parry, Sir Edward, turned back by the Polar current, [101];
  • mean temperature calculated from observations of, [245];
  • thermometer at Melville Island marked by, [247].
• Pauxis, the Straits of, ebb and flow of the sea in, [98].
• Peel, Sir William, thunderstorm experienced by, [293], [294].
• Pegasus, nebulous region of, [417].
• Pendulum, the, principle equalizing its oscillations, [50];
  • the earth’s figure calculated by, [50], [51];
  • experiments ascertaining the earth’s density, [57];
  • isochronous, a measure of time, [83];
  • a standard of the measure of extension, [89];
  • the, a connecting link between time and force, [94];
  • inventions to neutralise the effects of temperature, [272].
• Penumbra, in lunar eclipse, breadth of space occupied by, [40].
• Perigee, of the lunar orbit, period of its revolution, [37], [38];
  • cause of its rapid motion, [55].
• ——, solar, periods of its coincidence with the equinoxes, [86].
• Perihelion of a planet’s path defined, [16].
• —— of the earth’s orbit, its position regulating the length of seasons, [74].
• Periodic inequalities of planets, [13], [14];
  • law from which they are deduced, [24], [25];
  • of Jupiter’s satellites, [28], [29];
  • lunar, [35].
• Perkins, Mr., experiments of, testing the laws of compression, [78].
• Peron, M., specific diversity of marine animals asserted by, [254].
• Perpendicular force, the source of periodic inequalities, [15];
  • effects produced by, [18].
• Perpetual motion, invariable proportion between heat and force precluding, [279].
• Perseus, variable star in, [390], [391].
• Peters, Mr., comet discovered by, [370];
  • parallax of α Lyræ, [388], [389];
  • distances of fixed stars calculated, [389];
  • his theory of Sirius’ irregular motions, [392];
  • sun’s motion proved by, [405].
• Petit, M., observations of, on meteoric satellites, [423].
• Peru, arcs of the meridian measured in, [48].
• Phases of the moon, regulating returns of eclipses, [39].
• Phenomena, of effects of light in eclipses, [41], [42];
  • applied to computing longitudes, [43];
  • caused by tidal oscillation, [96];
  • from force of cohesion, [106], [107];
  • of capillary attraction, [115];
  • produced by refraction and reflection, [155-157];
  • by polarization of light, [186-190];
  • exhibited in fluorescence of light, [196], [197];
  • resulting from interaction of rays and molecules, analogous to effects of photography, [219-222];
  • phosphorescent, [295], [296];
  • of galvanism, [310];
  • of magnetism, [335], [345-348];
  • magnecrystallic, [349], [350];
  • exhibited by comets, [363], [364], [369], [370], [372-376];
  • by the Milky Way, [385-387];
  • by variable stars, [390-393];
  • by double stars, [397-401];
  • by nebulæ, [409-415], [417-419];
  • by meteoric showers, [421], [422].
• Phosphorescence, rays of the solar spectrum exciting, [216];
  • cause of, in the solar spectrum, [217];
  • excited by electricity, [294];
  • fish possessing the property of, [295];
  • the glow discharge, [295], [296];
  • experiments investigating the nature of, [296].
• Photo-galvanic engraving, [309].
• Photography, first suggestions, [203];
  • discoveries and improvements in, [204-207];
  • conditions affecting the chemical properties of rays producing, [207], [208];
  • images of the solar spectrum obtained by, [208-210];
  • coloured copy of an engraving, [211];
  • phenomena in, suggesting an absorptive action in the solar atmosphere, [212], [213];
  • chemical energy producing, distinct from light and heat, [214];
  • experiments by means of, testing the properties of rays, [218], [219];
  • experiments on action of light, heat, electricity, producing results analogous to effects of, [219-223].
• Photosphere, the, of the sun described, [224].
• Physical Sciences, the most extensive example of their connection, mode of its operation, [1].
• Pi Herculis, direction of solar motion with regard to, [406].
• Pisces, nebulous region of, [417].
• Planetary motion, representation of, [14].
• —— nebulæ, [409];
  • appearance of, [412].
• Planets, paths round the sun described by, [5];
  • law determining their revolutions, ib.;
  • forces adjusting their forms, [6];
  • their motions in elliptical orbits, mean distance from the sun, [8];
  • mode of obtaining the place of, in their orbits, [9];
  • computations giving the place of, in space, [10];
  • disturbances from reciprocal attraction affecting, compensations, [13-19];
  • telescopic, [20], [21];
  • perturbations in the mean motions of, [25], [26];
  • influence of, on lunar motions, [36];
  • eclipses and conjunctions of, [42];
  • formula finding their masses, [55];
  • their diameters, [56];
  • mass of the telescopic, compared with the moon, ib.;
  • comparative density, [58];
  • method of computing their places, [58-64];
  • discovery of, [61-63];
  • exploded theory touching telescopic, [63];
  • periods of their rotations, [66];
  • variation and position of the plane of the ecliptic produced by, [79];
  • its effect on the equinoctial points, [80];
  • climates of, [225], [226];
  • probably magnets, [346];
  • constant velocity of their mean motions, [366].
• Plants, distribution of known species over the globe, [249], [250].
• Plates, vibrating, experiments by means of, [144-146].
• Plateau, M., experiments of, on colour, [165], [166].
• Platina, incandescent, used as a source of heat, [260].
• Platinum, experiment producing spontaneous combustion of, [112], [113].
• Playfair, Professor, quoted in reference to La Grange’s discovery, [23].
• Pleiades, the, nebulous stars, [415].
• Plücker, Professor, discoveries of, in the action of magnetism in crystals, [349].
• Plumb-line, deviations of, from local attraction, [48];
  • earth’s density calculated from a deviation of, [58].
• Poinsot, M., La Place’s discovery extended by, [23];
  • comparison by, [24].
• Point, ready escape of electricity from a, [288].
• Poisson, M., decisions of, on the phenomena of capillary attraction, [114].
• Polar basin, probable temperature of, [245], [246].
• —— star, change of position in the, [81], [82].
• —— vegetation, contrasted with tropical, [248].
• Polarity, produced by electricity, [282];
  • of magnets defined, [336];
  • induced in iron, [337];
  • its antithetical manifestations of, [339];
  • invariably dual, [341];
  • of diamagnetic substances, [347], [348].
• Polarization of light, definition of, [179];
  • refracted by various substances, [180-183];
  • by reflection, [184];
  • angles of, [185];
  • phenomena exhibited by transmission through analyzing media, [186-188];
  • circular, [189-191];
  • theory of circular and elliptical, [192], [193];
  • substances producing, [193], [194];
  • theory of coloured images formed by, [194];
  • accidental, [195];
  • discovery of, ib.;
  • degraded light incapable of, [198];
  • communicating electricity, [220];
  • plane of motion of vibrations in, [223].
• Polarization of heat, first attempts, [264];
  • successful experiments, [265-267].
• —— of electricity by induction, [286].
• ——, experiment showing the action of magnetism on, [319];
  • affected by mechanical compression, [352].
• Poldice mine, the, temperature of the water pumped from, [229].
• Poles, the, cause of the flattening of a spheroidal mass at, [6];
  • diameter of Jupiter at, [27];
  • experiment determining the increase of gravitation towards, [49], [50];
  • the, drifting of ice from, [100], [101];
  • of maximum cold, centres of the isothermal lines, [245], [246];
  • nature of magnetic force distinguished by, [332];
  • four terrestrial, of maximum magnetic force, two magnetic, [343].
• Pollux, an optically double star, [401].
• Port Bowen Harbour, transmission of sound across, when frozen, [136].
• Positive electricity, defined, [282];
  • mode of exciting, [283].
• —— impressions in photography, [204].
• Pouillet, M., his estimate of the mean temperature of space, [119];
  • quantity of solar heat received by the earth computed by, [238];
  • data furnished by, to Professor Thomson, [279];
  • development of electricity investigated by, [291].
• Powell, Baden, substances producing elliptical polarization enumerated by, [193];
  • dispersion of light accounted for by the undulatory theory, [200], [201];
  • experiments in transmission of radiant heat, [262];
  • attempts to polarise heat, [264].
• Power, Mr., undulations producing fluorescent light computed by, [197];
  • law of solar rays acting on media, [198].
• Præsepe, the, in Cancer, [415].
• Precession, a, in the equinoxes of planets, its cause, [66];
  • mean, of the equinoctial points, defined and calculated, [80];
  • influence of, on the pole of the equator, on longitudes, [81].
• Pressure, electricity elicited by, [283], [284];
  • law of electrical, [288].
• Principato Citeriore, earthquake in, [234].
• Prisms, solar spectrum formed by, [159];
  • neutralizing effects of colour, [164];
  • of brown tourmaline, light polarized by, [180];
  • resolution of the pure white sunbeam by, [222];
  • substance of, determining the point of maximum heat in the solar spectrum, [263], [264];
  • electrical light analysed by, [288].
• Problem determining the motions of translation of the celestial bodies, [11];
  • of the three bodies, [58];
  • the hardest astronomical, [92].
• Procyon, light of, [402].
• Proportion, definite, the law of, in mixing substances, [111], [112].
• Protoxides of metals, their crystals, [109].
• Prussia, Eastern, fulgorites from, [293].
• Ptolemy, decrease in the inclination of Jupiter’s orbit since the age of, [19];
  • discovery of the Evection by, [35];
  • Indian lunar tables calculated in his time, [88];
  • horoscope ascribed to the age of, [89];
  • effects of refraction observed by, [155];
  • colour of Sirius in his time, [401].
• Quadratures, the equation of the centre in, [9];
  • lunar orbit augmented in, [35];
  • tides affected by the moon in, [96].
• Quadrupeds, distribution of distinct species of, [255].
• Quartz, crystallised, light polarized circularly by, [189], [190];
  • varieties of polarization exhibited by, [193].
• Quebec, extremes of temperature found in, [247].
• Quinine, sulphate of, producing fluorescence of light, [197].
• Radial force producing periodical changes in relative positions of the heavenly bodies, [15];
  • effects produced by, [16], [17];
  • principle neutralising its ultimate result, [19], [20].
• Radiation of heat, laws regulating, [257];
  • universal from substances, [268];
  • natural phenomena resulting from, [269];
  • slow decrease of the earth’s central heat from, [232];
  • influence of, on temperature, [239];
  • power of, in water compared with dry land, [242];
  • of heat, a transfer of motion, [277].
• Radii vectores, signification of, [8];
  • areas described by, [10];
  • force disturbing in the direction of, [14], [15].
• Ragona-Scina, M., his theory of rayless lines in the spectrum, [163].
• Rain, force shaping drops, [106];
  • cause of periodic tropical, [123];
  • region of, [124];
  • theory of its formation, [270];
  • an electric conductor, [292].
• Rankine, Mr., his theory of the structure of matter, [104];
  • his theory of the absorption of light, [177].
• Rays, common nature and common properties of, [268].
• —— of heat, existing independently of luminous, [257];
  • laws of transmission of, [258];
  • analogy between transmission of luminous rays and, [259];
  • temperature of their source affecting transmission, [260];
  • varying in nature with their origin, [261];
  • transmitted through coloured glass, [262];
  • traversing various media, ib.;
  • subject to refraction and reflection, [263];
  • polarized, [265-267];
  • absorption and reflection of, [268];
  • rotation of polarized, caused by magnetism, [319].
• —— of light, bent by passing from rare into dense media, [153];
  • partial and total reflection of, [156];
  • loss of, by obliquity of incidence, [158];
  • theory of their transmission and absorption, [159-161];
  • comparative refrangibility of, [163];
  • experiments on dispersion of, [164];
  • principle determining their colour, [170], [171];
  • transmission of, in glass or water, [177], [178];
  • conditions of polarized, [179];
  • double refraction, [181-183];
  • polarized by reflection, [184], [185];
  • coloured images produced by interference of, [194], [195];
  • internal dispersion of, [195-198];
  • heat, light, chemical action, independent properties of, [214], [215];
  • undulations constituting, [223];
  • conditions modifying the power of solar, to produce heat, [237];
  • transmitted independently of calorific rays, [258];
  • magnetizing of polarized, [318], [319].
• Rays, solar, effect produced by their refraction in lunar eclipse, [40];
  • passing between lunar mountains in solar eclipse, [41].
• —— of the solar spectrum, their chemical properties, [203];
  • varying chemical energy, [207], [208];
  • varying nature of their action, [208];
  • peculiar chemical action of the red, [209-211];
  • deoxydating and oxydating action of, [211], [212];
  • experiments detailed, [212-215];
  • new, obscure, detected by Sir John Herschel, [217].
• Red Sea, the, tide in, [98].
• Reflection of waves of sound, [137], [138];
  • of rays at surfaces of strata differing in density, phenomena occasioned by, [156], [157];
  • affecting colour, [160];
  • motion of a ray of light in, [177];
  • light polarized by, [184], [185];
  • elliptical polarization produced by, [193];
  • heat polarized by, [266];
  • of radiant heat from surfaces, [268].
• Refraction of the sun’s rays in lunar eclipses, [40];
  • of waves of sound, [138];
  • of light by the atmosphere, [153], [154];
  • mode of estimating, in case of celestial bodies, [155];
  • formulæ obtaining in case of terrestrial objects, ib.;
  • phenomena occasioned by, [155], [156];
  • colours decomposed by, [159], [160];
  • produced without colour, [164], [165];
  • power of, in media affecting the elasticity of the luminous ether, [177];
  • of a polarized ray, [180];
  • double, [181], [182];
  • Fresnel’s theory of, [183];
  • diminished capability of producing fluorescence, [196];
  • capability of, in rays, affecting their chemical action, [209-212];
  • effect of, on the lunar atmosphere, [226];
  • influence of, on transmission of heat, [258];
  • of rays of heat, [261-264];
  • heat polarized by, [266].
• Refrangibility, substances diminishing, of light, [196];
  • affecting the chemical action of rays, [209-212];
  • affecting radiation of heat, [257];
  • affecting transmission of radiant heat, [261-263].
• Reich, Professor, temperature of mines observed by, [228];
  • mean increase calculated by, [230].
• Reptiles, distribution of distinct species of, [254].
• Repulsion of electricities, [283];
  • experiments determining the laws of electrical, [286], [287];
  • modes of, in static and in Voltaic electricity, [317];
  • developing comets’ tails, [375-377].
• Resistance, a cause of accelerated motion, [367].
• Retina, the, action of, in receiving impressions, [166];
  • comparative sensibility of its fibres to light, [178].
• Retrograde motion of comets, [359], [368], [373], [379].
• Rhodiola rosea, identical species of, found in Tartary and in Scotland, [251].
• Rhombohedrons of carbonate of lime, [109].
• Richman, Professor, killed by lightning, [293].
• Richter, variation in length of the pendulum observed by, [51].
• Rings of Saturn, [66-68];
  • Saturn’s, diamagnetic, [347];
  • luminous, surrounding comets, [374], [375];
  • surrounding Donati’s, [379].
• Ritchie, Professor, electrical experiments of, [314].
• Ritter, M., chemical properties of the solar spectrum observed by, [203];
  • oxydizing effect of red rays, [209].
• Rive, M. Auguste de la, rate of increase of temperature in wells observed by, [230].
• Rivers, curvature of the land proved by, [46];
  • influence of, on the earth’s rotation, [71];
  • rising of tides in, [98];
  • effect of, in cooling the atmosphere, [243].
• Roget, Dr., phenomena of electro-magnetism explained by, [313].
• Rome, observations on lunar mountains made at, [70];
  • era fixed at, [85];
  • comet discovered from, [370].
• Ross, Sir James, stratum in the ocean discovered by, [101];
  • depressure of the barometer observed by, [120];
  • volcanic region discovered, [232].
• Rosse, Lord, nebulæ resolved by his telescope, [407], [408];
  • spiral nebula, [409], [410];
  • annular nebulæ discovered by, [410];
  • nebulous star, [411];
  • planetary nebulæ, [412];
  • nebulæ resolved by, [415].
• Rotation affecting winds, [122-127];
  • of winds, [124], [125];
  • of hurricanes, [125], [126];
  • produced by the Voltaic current acting on iron, [305];
  • of stratifications of electrical light, [307];
  • caused by electricity, [313], [314];
  • of light caused by an electric current, [319];
  • of magnets producing electricity, [330-332];
  • changes produced in comets by, [376].
• Rotations of the solar system, [7];
  • of the sun, [65];
  • of the planets, [66];
  • of satellites, [68];
  • of Jupiter’s satellites, [70];
  • of the earth, a measure of time, [71];
  • influence of temperature on, [72];
  • axis of, invariable, [76], [77].
• Rotatory motion, form indicating, [65];
  • of Donati’s comet, [379].
• Roux, M. le, observations on magnetic action in crystals, [350].
• Rudberg, M., refrangibility of substances ascertained by, [201], [202].
• Ruhmkorff, M., improvements on his electro-inductive apparatus, [328].
• Russell, Scott, Mr., velocity of the tidal wave estimated by, [95].
• Russia, arc of the meridian measured in, [48];
  • climates of, [244].
• Sabine, General, variations in the magnetic elements investigated by, [343], [344].
• Sagittarius, comet traversing the constellation of, [379];
  • the Milky Way in, [386];
  • nebula, [414].
• Sahara, the, causing monsoons, [124].
• —— desert, extent, influence of, on the atmosphere, [243].
• Salt, Mr., papyrus sent from Egypt by, [89].
• Sand, tubes in, formed by lightning, [293].
• Sandy deserts influencing temperature, [243].
• Sandwich Land, excess of cold in, over corresponding latitudes, [241].
• Sargassa, or grassy sea, found in the Atlantic, [253].
• Satellites, intensified action of attraction upon, [7];
  • intimate union of, with their primaries, [26];
  • exceptions to a general law of the solar system, [65], note;
  • rotations equal to the times of their revolutions, [68];
  • comet passing through, [69].
• ——, Jupiter’s, proportion of their mass to that of their primary, [27];
  • disturbing force of attraction affecting their orbits, [28];
  • periodic and secular inequalities, [28], [29];
  • eclipses, [30];
  • rotation, [70];
  • passage of a comet through, [359];
  • comet nearly approaching, [370].
• —— of Saturn, [32];
  • of Uranus and Neptune, [33].
• ——, mode of computing their masses, [55];
  • comparative density of, [58].
• —— of Neptune, [63].
• —— of the earth, shooting stars, [423].
• Saturn, unequally occurring compensations of disturbance in its motions, [15];
  • disturbing influence of, on Jupiter, excentricity of its orbit compared with Jupiter’s, [17];
  • retarding the revolution of Jupiter’s nodes, [19];
  • invariable plane passing between Jupiter and, [24];
  • observations on the mean motions of Jupiter and, [25], [26];
  • eclipse of, [42];
  • internal structure, [58];
  • astronomical tables of, [60];
  • period of his year, [66];
  • the rings of, described, [66-68];
  • his ring probably diamagnetic, [347];
  • action of, on Halley’s comet, [362], [363];
  • comets having their perihelia in his orbit, [381].
• Saurian reptiles, distinct tribes of, [254].
• Saussure, M., temperature of mines observed by, [228], [229];
  • lichen discovered by, [249].
• Savart, M., his researches and experiments in acoustics, [132], [133];
  • experiments on vibrations of glass rulers, [145-147];
  • experiments showing sympathetic undulations, [148], [149];
  • discoveries on the nature of voice, [152].
• Savary, M., orbital elements of a double star determined by, [396];
  • his mode of ascertaining the actual distances of fixed stars, [402], [403].
• Scheele, M., chemical changes effected by the solar spectrum observed by, [203].
• Schroëter, height of planetary atmospheres calculated by, [226].
• Schwabe, M., periodic variation in the solar spots observed by, [344].
• Science, its value regarded as the pursuit of truth, [1];
  • errors of the senses corrected by, [32];
  • evidence of its antiquity, [87].
• Sciences, mutual relations of forces proving the connexion between, [319-321];
  • analysis proving the whole circle of, kin, [427], [428].
• Scoresby, Captain, phenomenon occasioned by refraction observed by, [156].
• Scorpio, vacant patch of the Milky Way in, [386];
  • position of, [390];
  • a double star in, [395];
  • nebula in, [414].
• Scotland, progress of the tidal wave round, [94].
• Sea, the, inappreciable influence of, on the direction of gravity, [77];
  • mean height of snow-line above the level of, [241];
  • comparative extent of, [242].
• Seasons, conditions determining the duration of, [74];
  • cause of their unequal periods, [87];
  • theory of the tropical dry and rainy, [123].
• Seaweeds, photographic impressions of, [205], [206];
  • luxuriance, deep colours of, [253].
• Secchi, Professor, mountains of the moon observed by, [70];
  • photographic image of the moon obtained, [214];
  • temperatures of the sun’s surface estimated, [225];
  • experiments of, in photographing the moon and Jupiter, [226], [227].
• Secular inequalities of planets, [13], [14];
  • means of discovering, [24], [25];
  • effect of, on the mean motion of the moon, [36], [37].
• —— variations in mean values of the magnetic elements, [343].
• Seebeck, point of maximum heat in solar spectrum fixed by, [263];
  • discovery of, [264];
  • relations of heat to electricity discovered by, [332], [333].
• Seed-lobes, proportion in the distribution of plants having one or two, [252].
• Seleniate of zinc, crystals of, [107].
• Senarmont, M., experiments of, in expansion of crystals, [273].
• Senses, necessarily inaccurate testimony of the, [281].
• September, times coinciding in, [84].
• 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].
• Wheels invented to test intensity of sound, [132], [133].
• Wheat, range of its cultivation, [250].
• Wheatstone, Professor, experiments in acoustics of, [132];
  • musical instruments invented by, [143];
  • paper on musical vibrations read by, [145];
  • experiments on sounding boards of, [150];
  • experiments on sound reinforced by resonance, [151];
  • instrument measuring velocities of electricity and light invented by, [202];
  • spectrum of an electric spark observed, [289];
  • speed of electricity measured, [289], [290];
  • experiments on the spectrum of Voltaic flame, [303].
• Willis, Mr., articulating machine invented by, [151];
  • investigations of, into the mechanism of the larynx, [152].
• Winds, trade, [122], [123];
  • monsoons, [124];
  • extra-tropical, in the North Atlantic, ib.;
  • currents above the trade winds, [124], [125];
  • phenomena of rotatory motion, [125];
  • hurricanes, [125], [128];
  • agency of, influencing temperature, [244], [245].
• Wines, range of cultivation of the best, [250].
• Winter, atmospheric electricity in, [291].
• ——, mean temperature of, varying in the same latitude, [246], [247].
• Wolf, Professor, periods of variation in solar heat computed by, [225].
• Wollaston, Dr., experiments of, on sensitiveness to sound, quotation from, [132];
  • experiment of, to show the effect of variable media on refraction, [156];
  • discovery of rayless lines in the solar spectrum, [162];
  • observations of, on the chemical properties of the solar spectrum, [203], [209];
  • magnetic rotation suggested by, [313];
  • light emitted by the heavenly bodies calculated, [404].
• Xi Ursæ Majoris, periodic time of, [398];
  • velocity of the revolving star, [400].
• Year, a, in Jupiter and Saturn, [66];
  • tropical change in its length, [80];
  • length of the sidereal, ib.;
  • period of the mean, [83];
  • estimation of the Egyptian, [85];
  • first of our era, [86];
  • length of the, affected by a comet’s passage, [359].
• Young, Dr., his calculation of the possible compression of solids, [78];
  • date of a horoscope determined by, [89];
  • density of a liquid column estimated by, [114];
  • exception adduced by, to a general law in acoustics, [137];
  • his theory of the pleasures of harmony, [142];
  • undulatory theory established by, [169];
  • data used by, to test his theory of light, [175];
  • illustration of, proving sound and heat kindred forces, [280], [281].
• Zeta Cancri, a triple star, [395];
  • periodic time of, [398];
  • revolution, [400];
  • colours, [401].
• Zeta Herculis, periodic time, eclipse of, [398];
  • light, [402].
• Zinc, seleniate of, effect of temperature on its crystals, [107];
  • sulphate of, its crystals boiled in alcohol, [108].
• ——, electricity communicated to plates of, [220].
• Zodiac, the, signs of, change in their positions, [80].
• Zone of constant temperature in the atmosphere, [119];
  • laws of storms in the temperate and torrid, [127], [128];
  • of spots on the sun’s surface, its breadth, [224];
  • of constant temperature below the earth’s crust, [228];
  • comparative unequal distribution of land in temperate and torrid, [244];
  • of fixed stars, [385];
  • of stars nearest the sun, [390];
  • nebulous, [416];
  • of nebulous patches, [417];
  • of meteoric nebulæ, [423].
• Zones of instability of planetary orbits, [21].
• —— of temperature in the ocean, [101].
• —— of vegetation on the Peak of Teneriffe, [250].
• Zoophytes, specific distribution of, [254].

THE END.

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